Process for preparing endo-unsaturated 1,3-dioxol-2-ones

Abstract

The present invention relates to a process for preparing endo-unsaturated 1,3-dioxol-2-ones bearing an optionally substituted methyl group in the 4-position which comprises the isomerization of a 4-methylene-1,3-dioxol-2-one (2) in the presence of a catalyst which is a combination of a base and phenolic compound (3). The invention also relates to certain endo-unsaturated 1,3-dioxol-2-ones which can be prepared by said process.

Description

[0001]Process for preparing endo-unsaturated 1,3-dioxol-2-ones The present invention relates to a process for preparing endo-unsaturated 1,3-dioxol-2- ones bearing an optionally substituted methyl group in the 4-position. The invention also relates to certain endo-unsaturated 1,3-dioxol-2-ones which can be prepared by said process. TECHNICAL BACKGROUND Endo-unsaturated 1,3-dioxol-2-ones, also known as endo-vinylene carbonates, are valuable compounds, especially for the use as electrolyte additives in electrochemical storage systems, as building blocks in organic synthesis of active compounds for pharmaceutical and agricultural applications, as reactive diluent in the manufacture of epoxy resins, or as monomers in polymer applications. Despite their usefulness, synthetic methods for accessing them are still limited and usually restricted to specific substitution patterns, making certain substituted endo- vinylene carbonates inaccessible to date. The simplest endo-vinylene carbonate, 1,3-dioxol-2-one, for example is available via the chlorination of ethylenecarbonate followed by elimination of HCl to form the double bond as described for example in WO 2006 / 119909. Although this route works well for unsubstituted 1,3-dioxol-2-one, it often gives unsatisfactory results in the preparation of substituted 1,3-dioxol-2-ones due to the lack of selectivity of the chlorination step. Another drawback of this route is the formation of the hydrogen chloride as waste and the need for chlorine in the chlorination step. Endo-vinylene carbonates with substituents in the 4,5-positions are accessible via a different approach by reacting the corresponding acyloin with phosgene or derivatives of phosgene, such as triphosgene, 1,1’-carbonyldiimidazole or diphenylcarbonate. For example, M. Torres et al., Can. J. Chem. 1983, 61, 996-998 describe the synthesis of 4,5- di(tert-butyl)-1,3-dioxol-2-one by reacting the corresponding acyloin with phosgene. The conversion of acyloins to the respective 4,5-substitued endo-vinylene carbonates using triphosgene instead of phosgene is described in D. P. Sahu, Indian J. Chem. 2002, 41B, 1722-1723. Using 1,1’-carbonyldimidazole instead of phosgene for converting acyloins to the corresponding 4,5-substitued endo-vinylene carbonates is described in M. M. Krayushkin et al., Russ. Chem. Bull. 2002, 51, 1731-1736. A drawback of these routes is is the need for appropriately substituted acyloins, which are difficult to obtain. In particular acyloins for producing unsymmetric endo-vinylene carbonates which are unsubstituted in one of the 4 or 5 positions are difficult. Also, phosgene and triphosgene are toxic and difficult to handle and produce two equivalents of hydrogen chloride. The less toxic carbonyl diimidazole is expensive and therefore not particularly useful in industrial production on large scale. By using the less harmful and cheaper diphenylcarbonate, different 4,5-subsituted endo-vinylene carbonates are accessible based on the corresponding acyloins, as described in K. Onida et al., Adv. Synth. Catal. 2021, 363, 5129-5137. However, this method seems to be suitable only for preparing symmetric endo-vinylene carbonates, since preparations of unsymmetric ones bearing one hydrogen in position 4 or 5 were not successful. In addition, the formation of two equivalents of phenol as a by- product / waste is another drawback. Endo-vinylene carbonates synthetic are alos accessible by reaction of a substituted propargyl alcohol a with carbondioxide in the presence of a catalytic system comprising silver acetate (AgOAc) and 1,8-diazabicyclo[5.4.0]undec-7-en (DBU) as described in R. Ugajin et al., Synlett 2014, 25, 1178-180 and as depicted in the following scheme: Although this method allows for producing unsymmetrically substituted endo-vinylene carbonates, the method requires a very high amount, namely 40 mol%, of DBU. Another disadvantage is that at least one of the substituents Ra, Rbof the propargyl alcohol must be an aryl or alkenyl group, or else the endovinylene carbonate will not be formed. Therefore, this method does not allow for producing endo-vinylene carbonates bearing one hydrogen substituent in the 4- or 5 position. Catalytical isomerizations of olefinic double bonds are broadly reported and well known using as catalyst for example transition metal compounds (see e.g. S. Sanz-Navarro et al., Nat. Commun. 2022, 13, 2831) or strong acids, such as sulfuric acids. In a computa- tional study of the thermodynamics of exo–endo isomerization of carbon–carbon dou- ble bonds in five-membered ring compounds by E. Taskinen, Structural Chemistry 2001, 12, 405-412 it was mentioned that isomerization of exo- to endo-vinylene carbonates should be thermodynamically favored. However, this theoretical study does not disclose any catalyst systems or reaction conditions. In fact, processes for preparing endo-vi- nylene carbonates by catalytic isomerization of a corresponding exo-vinylene car- bonates having an exocyclic double bond instead of the endocyclic double bond having not been reported so far. This is most likely due to the incompatibility of the reactive vi- nylene carbonates with the known catalysts. SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide a process for preparing endo- vinylenecarbonates that is more economic than the known ones. In particular, the process should avoid toxic co-reagents, minimize side-products and waste, require small amounts of catalyst, and allow a more general access to unsymmetrically substituted endo-vinylene carbonates, such as those carrying one hydrogen in one of the 4 or 5 position. A further object of the invention is to provide new unsymmetrically substituted endo-vinylene carbonates. These objects have been achieved by providing a process for isomerizing exo- to the corresponding endo-vinylene carbonates using an efficient catalyst system, which is a combination of a base and phenolic compound. The present invention relates thus to a process for preparing an endo-unsaturated 1,3- dioxol-2-one (1), bearing an optionally substituted methyl group in the 4-position which comprises the isomerization of a 4-methylene-1,3-dioxol-2-one (2) in the presence of a catalyst which is a combination of a base and phenolic compound (3). The process of the invention is particularly suitable for preparing endo-unsaturated 1,3- dioxol-2-one compounds (1) that are of the formula (I) where R1, R2are identical or different and selected from the group consisting of hydrogen, an organic radical having 1 to 40 carbon atoms and up to 12 heteroatoms se- lected from O, S, Si and N, and where one of the radicals R1, R2may also be a moiety of the formula (IV): Link-(R4)k(IV) where Link is a bi- or trivalent organic radical having 1 to 40 carbon atoms and up to 12 het- eroatoms selected from O, S, Si and N, where the organic radical does not con- tain OH, NH2, COOH or SO3H, k is 1 or 2, and R4in formula (IV) is a radical of the formulae (R4a) or (R4b) # indicates the point of attachment of the radicals R4aand R4bto “Link”; R1aand R2aare identical or different and selected from the group consisting of hydrogen, an organic radical having 1 to 40 carbon atoms and up to 6 heteroatoms selected from O, S, Si and N and which are not a radical of the formula (IV). Accordingly, the exo-unsaturated 1,3-dioxol-2-one compounds (2) will have the follow- ing formula, where R1and R2are as defined for the formula (I), except for that R4in the moiety of the formula (IV) is a radical of the formulae R4cor R4d where #, R1aand R2aare as defined r the radicals of the formulae R4aand R4b. The compounds of the formula (I) where R2is hydrogen and R1is a radical CH2-O-R5, which is described herein below, are novel and accessible for the first time by the pro- cess described herein. Therefore, these compounds are also part of the present inven- tion. DETAILED DESCRIPTION OF THE INVENTION Definitions In the present description, the term radical is used interchangeably with the terms , moi- ety, residue, group or substituent, when defining the variables Rxin the presented for- mulae. Here and in the following the terms “radical” and “moiety”, “substituent” and “residue” refer to group of atoms in which the atoms are linked to each other by covalent bonds and which in turn are linked to the rest of the molecule by a covalent bond. If not stated otherwise, “radicals” are monovalent, i. e. they are linked to the rest of the molecule by one covalent bond. However, if indicated, radicals may also be di- or trivalent, i. e. they link to 2 or 3 groups of the molecules by 2 or 3 covalent bonds. The term “organic radical having 1 to 40 carbon atoms and up to 10 heteroatoms se- lected from O, S, Si and N” is understood by a skilled person as an organic radical con- sisting of 1 to 40 carbon atoms, in particular 1 to 20 carbon atoms, up to 10 heteroatoms selected from O, S, Si and N, and a hydrogen atoms. The organic radical may be an ali- phatic radical, a cycloaliphatic radical, a heterocycloaliphatic radical, an aromatic radical or a heteroaromatic radical and combinations of such radicals, such as arylalkyl, cycloal- kylalkyl, heteroaarylalkyl and the like, provided that the total number of carbon atoms and heteroatoms is in the ranges given here. The heteroatoms may form functional groups, such as ether groups, thioether groups, ester groups, amide groups, urea groups or urethane groups. Typically, the heteroatoms do not form hydroxyl groups, carboxylic acid groups or sulfonic acid groups, as these groups may interfere with the base or may act as nucleophiles under the reaction conditions. The term “halogen” denotes in each case fluorine, chlorine, bromine or iodine. The term "alkyl" indicates a saturated straight-chain or branched aliphatic hydrocarbon radical having for example 1 to 10 (= C1-C10alkyl) carbon atoms, or 1 to 6 (= C1-C6alkyl) or 1 to 4 (= C1C4alkyl) or 1 to 3 (= C1C3alkyl) or 1 or 2 (= C1-C2alkyl) carbon atoms. C1-C2Alkyl is methyl or ethyl. Examples for C1-C3alkyl are, in addition to those mentioned for C1-C2alkyl, propyl and isopropyl. Examples for C1-C4alkyl are, in addition to those men- tioned for C1-C3alkyl, butyl, 1-methylpropyl (sec-butyl), 2-methylpropyl (isobutyl) or 1,1- dimethylethyl (tert-butyl). Examples for C1-C6alkyl are, in addition to those mentioned for C1-C4alkyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, hexyl, 1-methylpentyl, 2- methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3- dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2- ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, or 1-ethyl- 2-methylpropyl. Examples for C1-C10alkyl are, in addition to those mentioned for C1-C6alkyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl and positional isomers thereof. The term "fluoroalkyl", also expressed as "alkyl which is partially or fully fluorinated", in- dicates saturated straight-chain or branched aliphatic hydrocarbon radicals having for example 1 to 10 (= C1-C10fluoroalkyl) carbon atoms, or (= C1-C6fluoroalkyl) or 1 to 4 (= C1-C4fluoroalkyl) or 1 or 2 (= C1-C2fluoroalkyl) carbon atoms, where some or all of the hydrogen atoms in these groups are replaced by fluorine atoms as mentioned above. "C1-C2Fluoroalkyl" refers to alkyl groups having 1 or 2 carbon atoms (as mentioned above), where some or all of the hydrogen atoms in these groups are replaced by fluo- rine atoms as mentioned above. "C1-C3Fluoroalkyl" refers to straight-chain or branched alkyl groups having 1 to 3 carbon atoms (as mentioned above), where some or all of the hydrogen atoms in these groups are replaced by fluorine atoms as mentioned above. "C1-C4fluoroalkyl" refers to straight-chain or branched alkyl groups having 1 to 4 carbon atoms (as mentioned above), where some or all of the hydrogen atoms in these groups are replaced by fluorine atoms as mentioned above. "C1-C6fluoroalkyl" refers to straight-chain or branched alkyl groups having 1 to 6 carbon atoms (as mentioned above), where some or all of the hydrogen atoms in these groups are replaced by fluo- rine atoms as mentioned above. Examples for C1-C2fluoroalkyl are difluoromethyl, tri- fluoromethyl, 1-fluoroethyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl or pen- tafluoroethyl. Examples for C1-C3fluoroalkyl are, in addition to those mentioned for C1- C2flluoroalkyl, 1-fluoropropyl, 2-fluoropropyl, 3-fluoropropyl, 1,1-difluoropropyl, 2,2- difluoropropyl, 1,2-difluoropropyl, 3,3-difluoropropyl, 3,3,3-trifluoropropyl, heptafluoro- propyl, 1,1,1-trifluoroprop-2-yl, 1,1,1,3,3,3-hexafluoroprop-2-yl, heptafluoroprop-2-yl and the like. Examples for C1-C4fluoroalkyl are, in addition to those mentioned for C1-C3fluoroalkyl, 4-fluorobutyl and the like. The term "C2-C10alkenyl" as used herein denotes monounsaturated straight-chain or branched hydrocarbon radicals having 2 to 6 ("C2-C6alkenyl") or 2 to 10 ("C2-C10alkenyl") carbon atoms and a double bond in any position, for example C2-C6alkenyl, such as ethenyl, 1-propenyl, 2-propenyl, 1-methylethenyl, 1-butenyl, 2-butenyl, 3-bu- tenyl, 1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-2-pro- penyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 2-me- thyl-1-butenyl, 3-methyl-1-butenyl, 1-methyl-2-butenyl, 2-methyl-2-butenyl, 3-methyl-2- butenyl, 1-methyl-3-butenyl, 2-methyl-3-butenyl, 3-methyl-3-butenyl, 1,1-dimethyl-2- propenyl, 1,2-dimethyl-1-propenyl, 1,2-dimethyl-2-propenyl, 1-ethyl-1-propenyl, 1-ethyl- 2-propenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 1-methyl-1-pentenyl, 2-methyl-1-pentenyl, 3-methyl-1-pentenyl, 4-methyl-1-pentenyl, 1-methyl-2-pentenyl, 2- methyl-2-pentenyl, 3-methyl-2-pentenyl, 4-methyl-2-pentenyl, 1-methyl-3-pentenyl, 2- methyl-3-pentenyl, 3-methyl-3-pentenyl, 4-methyl-3-pentenyl, 1-methyl-4-pentenyl, 2- methyl-4-pentenyl, 3-methyl-4-pentenyl, 4-methyl-4-pentenyl, 1,1-dimethyl-2-butenyl, 1,1-dimethyl-3-butenyl, 1,2-dimethyl-1-butenyl, 1,2-dimethyl-2-butenyl, 1,2-dimethyl-3- butenyl, 1,3-dimethyl-1-butenyl, 1,3-dimethyl-2-butenyl, 1,3-dimethyl-3-butenyl, 2,2-di- methyl-3-butenyl, 2,3-dimethyl-1-butenyl, 2,3-dimethyl-2-butenyl, 2,3-dimethyl-3-bu- tenyl, 3,3-dimethyl-1-butenyl, 3,3-dimethyl-2-butenyl, 1-ethyl-1-butenyl, 1-ethyl-2-bu- tenyl, 1-ethyl-3-butenyl, 2-ethyl-1-butenyl, 2-ethyl-2-butenyl, 2-ethyl-3-butenyl, 1,1,2-tri- methyl-2-propenyl, 1-ethyl-1-methyl-2-propenyl, 1-ethyl-2-methyl-1-propenyl, 1-ethyl-2- methyl-2-propenyl and the like, or C2-C10alkenyl, such as the radicals mentioned for C2- C6-alkenyl and additionally 1-heptenyl, 2-heptenyl, 3-heptenyl, 1-octenyl, 2-octenyl, 3- octenyl, 4-octenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl, 4-nonenyl, 1-decenyl, 2-decenyl, 3- decenyl, 4-decenyl, 5-decenyl and the positional isomers thereof. In particular, "C2-C10alkenyl" is "C2-C4alkenyl", such as ethenyl or 1-propen-2-yl. The term "cycloalkyl" indicates monocyclic, bicyclic or polycyclic saturated hydrocarbon radicals having in general 3 to 10 (= C3-C10cycloalkyl), or 3 to 8 (= C3-C8cycloalkyl) or 3 to 6 (= C3-C6cycloalkyl) carbon atoms and of course no heteroatoms as ring members; i.e. all ring members are carbon atoms. Examples of monocyclic cycloalkyl having 3 to 4 carbon atoms comprise cyclopropyl and cyclobutyl. Examples of monocyclic cycloalkyl having 3 to 5 carbon atoms comprise cyclopropyl, cyclobutyl and cyclopentyl. Examples of monocyclic cycloalkyl having 3 to 6 carbon atoms comprise cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. Examples of monocyclic cycloalkyl having 3 to 8 carbon at- oms comprise cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooc- tyl. Examples of monocyclic cycloalkyl having 3 to 10 carbon atoms comprise cyclopro- pyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl and cy- clodecyl. “Alkoxy” is an alkyl group, as defined above, attached via an oxygen atom to the remainder of the molecule; for example a C1-C4alkyl group attached via an oxygen atom to the remainder of the molecule (= C1-C4alkoxy). "C1-C2Alkoxy" is a C1-C2alkyl group, as defined above, attached via an oxygen atom. "C1-C3Alkoxy" is a C1-C3alkyl group, as defined above, attached via an oxygen atom. C1-C2Alkoxy is methoxy or ethoxy. C1-C3Alkoxy is additionally, for example, n-propoxy and 1-methylethoxy (isopropoxy). C1-C4Alkoxy is additionally, for example, butoxy, 1-methylpropoxy (sec- butoxy), 2-methylpropoxy (isobutoxy) or 1,1-dimethylethoxy (tert-butoxy). The term "fluoroalkoxy" as used herein denotes in each case a straight-chain or branched alkoxy group, as defined above, having e.g. from 1 to 4 carbon atoms (= C1-C4fluoroalkoxy), wherein the hydrogen atoms of this group are partially or totally replaced with fluorine atoms (thus, the radical is also termed fluorinated alkoxy). C1-C2Fluoroalkoxy is, for example, OCH2F, OCHF2, OCF3, 2-fluoroethoxy, 2,2-difluoroethoxy, 2,2,2-trifluoroethoxy, or OC2F5.C1-C3Fluoroalkoxy is additionally, for example, 2-fluoropropoxy, 3-fluoropropoxy, 2,2-difluoropropoxy, 2,3-difluoropropoxy, 3,3,3- trifluoropropoxy, OCH2-C2F5, OCF2-C2F5or 1-(CH2F)-2-fluoroethoxy. C1-C4Fluoroalkoxy is additionally, for example, 4-fluorobutoxy or nonafluorobutoxy. “C3-C10Cycloalkoxy” is a C3-C10cycloalkyl group, as defined above, attached via an oxygen atom to the remainder of the molecule. Examples of C3-C10cycloalkoxy groups are cyclopropoxy, cyclobutoxy, cyclopentoxy, cyclohexoxy, cycloheptoxy and cyclo- octoxy. “C6-C14Aryl” relates in particular to mono-, bi- or tricyclic carbocyclic aromatic radical having 6 to 14 carbon atoms. One example for a monocyclic aromatic radical is phenyl. In bicyclic aryl rings two aromatic rings are condensed, i.e. they share two vicinal C at- oms as ring members. One example for a bicyclic aromatic radical is naphthyl. In tricyclic aryl rings, three rings are condensed. Examples for tricyclic aryl radicals are phenan- threnyl, anthracenyl and phenalenyl. “C6-C14Aryloxy” is a C6-C14aryl group, as defined above, attached via an oxygen atom to the remainder of the molecule. Examples of C6-C14aryloxy are phenoxy, 1-naphthoxy, 2- naphthoxy, 9-phenantroxy and the like. The term "C3-C10heterocyclyl" as used herein denotes mono-, bi- or tricyclic saturated or partially unsaturated ring system having as ring members 3 to 10 carbon atomes and 1 to 4 heteroatoms or heteroatom-containing groups selected from O, N, S, SO and S(O)2. Examples of C3-C10heterocyclyl are oxetanyl, piperidinyl, piperazinyl, morpholinyl, thiomorpholinyl, pyrrolidinyl, oxazolidinyl, tetrahydrofuryl, dioxolanyl, dioxanyl, hexahy- droazepinyl, hexyhydrooxepinyl, hexahydrothiepinyl, di- and tetrahydropyridinyl, pyrroli- nyl, oxazolinyl, dihydrofuryl, tetrahydroazepinyl, tetrahydrooxepinyl, tetrahydrothiepinyl and the like. “C3-C10Heterocyclyloxy” is a C3-C10heterocyclyl group, as defined above, attached via an oxygen atom to the remainder of the molecule. Examples of C3-C10heterocyclyloxy are 3-piperidinoxy, 2-tetrahydrofuroxy, 4-oxazolinoxy and the like. The term " C3-C14hetaryl" refers to heteroaromatic, monocyclic, bicyclic or tricyclic con- densed systems with 3 to 14 carbon atoms as ring members, in which at least one of the rings is aromatic and which contain 1, 2, 3 or 4 heteroatoms selected from N, S or O. Monocyclic hetaryl groups are preferably 5- or 6-membered hetaryl groups comprising 1, 2 or 3 heteroatoms selected from O, S or N such as 2-furyl (furan-2-yl), 3-furyl (furan- 3-yl), 2-thienyl (thiophen-2-yl), 3-thienyl (thiophen-3-yl), 1H-pyrrol-2-yl, 1H-pyrrol-3-yl, pyrrol-1-yl, imidazol-2-yl, imidazol-1-yl, imidazol-4-yl, pyrazol-1-yl, pyrazol-3-yl, pyrazol- 4-yl, pyrazol-5-yl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 3-isothiazolyl, 4-isothiazolyl, 5-isothiazolyl, 2-oxazolyl, 4-oxazolyl, 5-oxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, pyri- din-2-yl, pyridin-3-yl, pyridin-4-yl, 3-pyridazinyl, 4-pyridazinyl, 2-pyrimidinyl, 4-pyrimidi- nyl, 5-pyrimidinyl, 2-pyrazinyl, 1,3,5-triazin-2-yl and 1,2,4-triazin-3-yl. Bicyclic throughout aromatic heteroaryl is 9- or 10-membered and contains 1, 2, 3 or 4 heteroatoms selected from O, S or N. Examples are quinolinyl, isoquinolinyl, indolyl, isoindolyl, indolizinyl, ben- zofuranyl, isobenzofuranyl, benzothiophenyl, benzoxazolyl, benzisoxazolyl, benzthia- zolyl, benzoxadiazolyl, benzothiadiazolyl, benzoxazinyl, benzopyrazolyl, benzimidazolyl, benzotriazolyl, benzotriazinyl. Examples for tricyclic hetaryl are carbazolyl, dibenzo- furanyl, acridinyl, phenazinyl, phenoxazinyl, phenothiazinyl, and phenoxathiinyl. “C3-C14Hetaryloxy” is a C3-C14hetaryl group, as defined above, attached via an oxygen atom to the remainder of the molecule. Examples of C3-C14hetaryloxy are 2-furanyloxy, 1-imidazoloxy, 8-quinolinoxy, 4-oxazolinoxy and the like. “C1-C10Alkandiyl” is a linear or branched divalent radical derived from the corresponding C1-C10alkane. Examples are -CH2-, -CH2CH2-, -CH(CH3)-, -CH2CH2CH2-, -CH(CH3)CH2-, -CH2CH(CH3)-, -C(CH3)2-, -CH2CH2CH2CH2-, -CH(CH3)CH2CH2-, -CH2CH2CH(CH3)-, -C(CH3)2CH2-, -CH2C(CH3)2-, -(CH2)5-, -(CH2)6-, -(CH2)7-, -(CH2)8-, -(CH2)9-, -(CH2)10- and the like. “C3-C10Cycloalkylene” is a divalent cycloalkanediyl radical having 3 to 10 carbon atoms. Examples are cyclopropane-1,1-diyl, cyclopropane-1,2-diyl, cyclobutane-1,1-diyl, cyclobu- tane-1,2-diyl, cyclobutane-1,3-diyl, cyclopentene-1,1-diyl, cyclopentene-1,2-diyl, cyclo- pentene-1,3-diyl, cyclohexane-1,1-diyl, cyclohexane-1,2-diyl, cyclohexane-1,3-diyl, cyclo- hexane-1,4-diyl, cyclooctane-1,5-diyl and the like. “C6-C14Arylene” is a divalent aromatic radical having 6 to 14 carbon atoms. Examples are 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 1,4-naphthylene, 1,6-naphthylene, 2,7-phe- nanthrylene, 3,6-phenanthrylene, 2,6-anthracylene and the like. The remarks made below as to preferred embodiments of the variables (substituents) of the compounds of formulae (I) and (II) are valid on their own as well as preferably in combination with each other. A preferred group (A) of embodiments relates to the process of the invention, where the substituents R1and R2of the compounds of formulae (I) and (II) have the following meanings: R1is selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroal- kyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl, C3-C14hetaryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra1and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; and R2is selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroal- kyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl and C3-C14hetaryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra2and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2; where Ra1, Ra2independently of each other are selected from Cl and Br and where one of Ra1, Ra2may -OR12, O-C(O)- OR12, C alkyl)3, C3-C10cy- cloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last mentioned radicals are unsubstituted or sub- stituted by 1, 2, 3 or 4 radicals Rcyc3; Ra3is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, A-Ra4, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl or C3- C14hetaryl, where the 8 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; Ra4is selected from H, CN, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)-OR12, O-C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C1- C6-alkyloxy, C1-C6-fluoroalkoxy, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3- C14hetaryloxy, where the 8 last mentioned radicals are unsubstituted or substi- tuted by 1, 2, 3 or 4 radicals Rcyc3; A is C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be re- placed by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C10alkandiyl may be replaced by O and where C3-C10cycloalkylene and C6-C14arylene are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc4; Rcyc1, Rcyc2, Rcyc3, Rcyc4independently of each other are selected from selected from the group consisting of F, Cl, Br, CN, NO2, C1-C10-alkyl, C1-C10-fluoroalkyl, C1-C10-al- kyloxy, C1-C10-fluoroalkoxy, C(O)-R11, O-C(O)-R11, C(O)-OR12, O-C(O)-OR12, C(O)- NHR13and O-C(O)-NHR13and C6-C14aryl; R11is selected from hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl; R12, R13independently of each other are selected from C1-C10alkyl, C1-C10fluoroalkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl; or where one of the radicals R1, R2may also be a radical of the formula (IV), Link-(R4)k(IV) wherein k is 1 or 2, in particular 1, R4is a radical of the formulae (R4a), (R4b), (R4c) or (R4d) as defined herein above and Link is a bivalent or trivalent radical selected from C1-C10alkandiyl, C1-C10alkantriyl, bi- or trivalent C6-C14arylene and bi- or trivalent C3-C10cycloalkylene, where one of the CH2groups of C1-C10alkandiyl and C1-C10alkantriyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C10alkandiyl and C1-C10alkantriyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where C6-C14arylene and C3-C10cycloalkylene are unsubstituted or carry 1, 2 or 3 radicals Rcyc4; R1ais selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroal- kyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl, C3-C14hetaryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra1and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; R2ais selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroal- kyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl and C3-C14hetaryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra2and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2. A particular subgroup (A1) of group (A) of embodiment relates to the process of the in- vention, where the substituents R1and R2of the compounds of formulae (I) and (II) have the following meanings: R1is selected from the group consisting of hydrogen, C1-C10alkyl, CH2-O-Ra3, CH2-O-ARa4, C3-C10cycloalkyl and C6-C14aryl, where C1-C10alkyl is unsubstituted or substituted by one radical Ra11and where C3-C10cycloalkyl and C6-C14aryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; R2is selected from the group consisting of hydrogen, C1-C10alkyl, C3-C10cycloalkyl and C6-C14aryl, where C1-C10alkyl is unsubstituted or substituted by one radical Ra22and where C3-C10cycloalkyl and C6-C14aryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2; where A, Ra3, Ra4, Ra11, Ra12, Rcyc1and Rcyc2are as defined above and where A, Ra3, Ra4, Ra11, Rcyc1and Rcyc2alone or preferably in combination have in particular the following mean- ings: A is C1-C8alkandiyl; Ra11, Ra22independently of each other are selected from C1-C4-alkoxy, C3-C10cycloalkyl, C3-C10cycloalkoxy, phenyl, phenoxy, where phenyl and phenoxy are unsubsti- tuted or substituted by 1, 2, 3 or 4 radicals Rcyc3; Rcyc1, Rcyc2independently of each other are selected from the group consisting of F, Cl, Br, CN, C1-C6-alkyl, C1-C6-fluoroalkyl, C1-C6-alkyloxy, C1-C6-fluoroalkoxy and phenyl; Ra3is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3-C10cycloalkyl and phenyl and phenoxy, where C3-C10cy- cloalkyl and phenyl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; Ra4is selected from H, C1-C6-alkyloxy, C1-C6-fluoroalkoxy, C(O)-R11, O-C(O)-R11, NH- C(O)-R11, C(O)-OR12, O-C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3-C10cycloalkyl, C3-C10cycloalkoxy, phenyl and phenoxy, where the 4 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; where R11, R12, R13and Rcyc3are as defined above and where R11, R12, R13and Rcyc3alone or preferably in combination have in particular the following meanings: Rcyc3is selected from the group consisting of F, Cl, Br, CN, C1-C6-alkyl, C1-C6-fluoroal- kyl, C1-C6-alkyloxy, C1-C6-fluoroalkoxy and phenyl; R11is selected from hydrogen, C1-C6alkyl, C1-C6fluoroalkyl, C2-C6alkenyl, C5-C6cy- cloalkyl and phenyl; R12, R13independently of each other are selected from C1-C6alkyl, C1-C6fluoroalkyl, C2- C6alkenyl, C5-C6cycloalkyl and phenyl. Another particular subgroup (A2) of group (A) of embodiment relates to the process of the invention, where one of the substituents R1, R2is a radical of the formula (IV’), CH2-O-A’-R4(IV’) while the remaining substituent R1or R2is as defined in group (A1) of embodiments and wherein R4is a radical of the formulae (R4a), (R4b), (R4c) or (R4d) as defined herein above and A’ is a bivalent radical selected from C1-C10alkandiyl, phenylene and C5-C6cycloal- kylene, where one of the CH2groups of C1-C10alkandiyl may be replaced by one of phenylene and C5-C6cycloalkylene; and where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where phenylene and C5-C6cycloalkylene are unsubstituted or substituted by 1, 2 or 3 radicals Rcyc4; R1ais selected from the group consisting of hydrogen, C1-C10alkyl, CH2-O-A-Ra33, C3-C10cycloalkyl and C6-C14aryl, where C1-C10alkyl is unsubstituted or substi- tuted by one radical Ra11, and where C3-C10cycloalkyl and C6-C14aryl are unsub- stituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; R2ais selected from the group consisting of hydrogen, C1-C10alkyl, C3-C10cycloalkyl and C6-C14aryl, where C1-C10alkyl is unsubstituted or substituted by one radical Ra22and where C3-C10cycloalkyl and C6-C14aryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2, where Ra11, Ra22, Ra33, Rcyc1, Rcyc2and Rcyc4are as defined above and where A, Ra3, Ra4, Ra11, Rcyc1and Rcyc2alone or preferably in combination have in particular the following mean- ings: A is C1-C8alkandiyl; Ra11, Ra22, Ra33independently of each other are selected from C1-C4-alkoxy, C3-C10cy- cloalkyl, C3-C10cycloalkoxy, phenyl, phenoxy, where phenyl and phenoxy are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; Rcyc1, Rcyc2, Rcyc3, Rcyc4independently of each other are selected from the group con- sisting of F, Cl, Br, CN, C1-C6-alkyl, C1-C6-fluoroalkyl, C1-C6-alkyloxy, C1-C6- fluoroalkoxy and phenyl. Irrespective of their occurrence in the groups (A), (A1) and (A2) of embodiments of the invention the variables A, Ra11, Ra22, Rcyc1, Rcyc2, Rcyc3, Rcyc4, Ra3, Ra4, R11, R12, R13, A’, Ra1, Ra2and R4have the following preferred meanings: A is C1-C4alkandiyl, and more preferably is C1-C2alkandiyl; in particular is C1-C2alkandiyl, such as methylene or 1,2-ethandiyl; Ra11, Ra22independently of each other are selected from C1-C4-alkoxy, phenyl, phenoxy, where phenyl and phenoxy are unsubstituted or substituted by 1 or 2 radicals Rcyc3; and in particular from C1-C4-alkoxy and phenyl; Rcyc1, Rcyc2, Rcyc3, Rcyc4independently of each other are selected from F, Cl, CN, C1-C4- alkyl, C1-C4-fluoroalkyl, C1-C4-alkyloxy, C1-C4-fluoroalkoxy and phenyl; more preferably from F, C1-C2-alkyl, C1-C2-fluoroalkyl, C1-C4-alkyloxy and phenyl; and in particular from F, methyl, fluoromethyl, trifluoromethyl, methoxy and phenyl; Ra3is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, and phenyl, where phenyl is unsubstituted or substituted by 1 or 2 radicals Rcyc3; more preferably from C(O)- R11and C(O)-OR12; Ra4is selected from C1-C4-alkyloxy, C1-C4-fluoroalkoxy, C(O)-R11, C(O)-OR12, C3-C6cycloalkyl and phenyl, where the 2 last mentioned radicals are unsubstituted or substituted by 1 or 2 radicals Rcyc3; more preferably from C(O)-R11, C(O)-OR12, C3-C6cycloalkyl and phenyl, where the 2 last mentioned radicals are unsubstituted or substituted by 1 or 2 radicals Rcyc3; and in particular from C(O)-OR12and phenyl which is unsubstituted or substituted by 1 or 2 radicals Rcyc3; R11is selected from hydrogen, C1-C4alkyl, C2-C4alkenyl and C1-C4fluoroalkyl; more preferably from methyl, ethyl, C2-C4alkenyl and C1-C2fluoroalkyl; and in partic- ular is methyl, ethyl, ethenyl or 1-propen-2-yl; R12, R13independently of each other are selected from C1-C6alkyl and C1-C4fluoroalkyl; more preferably from C1-C4alkyl and C1-C2fluoroalkyl; and in particular from C1-C4alkyl; A’ is a bivalent radical selected from C1-C10alkandiyl and phenylene, where one of the CH2groups of C1-C10alkandiyl may be replaced by phenylene, and where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl may be replaced by O, C(O), C(O)- O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where phenylene is unsubsti- tuted or substituted by 1 or 2 radicals Rcyc4; and A’ is in particular selected from C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be re- placed by phenylene, and where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl may be replaced by O, C(O)-O, NH-C(O) or NH-C(O)-O, and where phenylene is unsubstituted or substituted by 1 radical Rcyc4; R1ais selected from hydrogen and C1-C4alkyl; more preferably from hydrogen and methyl; and in particular is hydrogen; R2ais selected from hydrogen and C1-C4alkyl; more preferably from hydrogen and methyl; and in particular is hydrogen; and R4in case of a compound of formula (I) is in formula (IV’) a radical of the formula R4aand in case of a compound of formula (II) is in formula (IV’) a radical of the formula R4c. In particular subgroups (A1a) and (A2a) of groups (A1) and (A2) of embodiments the radical R1in formulae (I) and (II) is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra11, where Ra11has one of the meanings defined herein, in particular one of those mentioned as preferred. According to this embodiment R1is preferably hydrogen or C1-C10alkyl, and in particular is hydrogen. In particular subgroups (A1b) and (A2b) of groups (A1) and (A2) of embodiments the radical R1in formulae (I) and (II) is CH2-O-Ra3or CH2-O-ARa4, where A, Ra3and Ra4have one of the meanings defined herein, in particular one of those mentioned as preferred. According to these subgroups (A1b) and (A2b), R1is in particular CH2-O-C(O)-R11, CH2-O-C(O)-OR12, CH2-O-C(O)-NHR13, CH2-O-CH2-C(O)-OR12, CH2-O-CH2-CH2-C(O)-OR12or CH2-O-CH2-phenyl, where R11is hydrogen or C1-C4alkyl, such as methyl, and R12and R13are both C1-C4alkyl, such as methyl or tert-butyl, or phe- nyl which is unsubstituted or carries 1 or 2 radicals Rcyc3, which are especially selected from methyl, phenyl, F and trifluoromethyl. In particular subgroups (A1c) and (A2c) of groups (A1) and (A2) of embodiments the radical R1in formulae (I) and (II) is C6-C14aryl which is unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1, where Rcyc1has one of the meanings defined herein, in particular one of those mentioned as preferred. In a particular subgroup (A2d) of group (A2) of embodiments the radical R1in formulae (I) and (II) is CH2-O-A’-R4, where A’ and R4each have one of the meanings defined herein, in particular one of those mentioned as preferred. According to this embodi- ment R1is in particular CH2-O-A’-R4, wherein A’ is C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be replaced by phenylene, where 1, 2 or 3 of the CH2 groups of C1-C10alkandiyl may be replaced by O, C(O)-O, NH-C(O) or NH-C(O)-O, where phenylene is unsubstituted or substituted by one radical Rcyc4, which is especially methyl, and where R4in case of a compound of formula (I) is a radical of the formula R4aand in case of a compound of formula (II) is of the formula R4c. In particular subgroups (A1e) and (A2e) of groups (A1) and (A2) of embodiments the radical R2in formulae (I) and (II) is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra22, where Ra22has one of the meanings defined herein, in particular one of those mentioned as preferred. According to the group (A1e) of em- bodiment R2is in particular hydrogen or C1-C4alkyl, such as methyl n-propyl or isopro- pyl. In particular subgroups (A1f) and (A2f) of groups (A1) and (A2) of embodiments the radi- cal R2in formulae (I) and (II) is C6-C14aryl which is unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2, where Rcyc2has one of the meanings defined herein, in particular one of those mentioned as preferred. According to this embodiment R2is in particular phe- nyl that may or may not carry one or two, especially one, substituent selected from me- thyl, ethyl, propyl, isopropyl, methoxy, ethoxy, F, fluoromethyl and trifluoromethyl, espe- cially from methyl, F and methoxy. In a particular subgroup (A2g) of group (A2) of embodiments the radical R2in formulae (I) and (II) is a moiety Link-(R4)k, wherein R4is R4bor R4d, k is 1, and Link is a bivalent C6- C14arylene, such as especially phenylene, which is unsubstituted or carries 1 or 2 radicals Rcyc2having one of the meanings defined herein, in particular one of those mentioned as preferred. According to this group of embodiments R2is in particular a moiety Link-R4, wherein Link is phenylene and R4is R4bor R4d, respectively. In a particular subgroup (A1h) of group (A1) of embodiments R1is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra11, where Ra11has one of the meanings defined herein, in particular one of those mentioned as preferred. According to this group (A1h) of embodiments R1is pref- erably hydrogen or C1-C10alkyl, and in particular is hydrogen; R2is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra22, where Ra22has one of the meanings defined herein, in particular one of those mentioned as preferred. According to the group (A1h) of embodiment R2is in par- ticular hydrogen or C1-C4alkyl, such as methyl n-propyl or isopropyl. Examples of compounds of subgroup (A1h) of embodiments include, but are not limited to the compounds (I-1), (II-1), (I-2), (II-2), (I-3), (II-3), (II-4) and (II-4) listed in Scheme A below. In a particular subgroup (A1i) of group (A1) of embodiments R1is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra11, where Ra11has one of the meanings defined herein, in particular one of those mentioned as preferred. According to this group (A1h) of embodiments R1is pref- erably hydrogen or C1-C10alkyl, and in particular is hydrogen; R2is C6-C14aryl which is unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2, where Rcyc2has one of the meanings defined herein, in particular one of those mentioned as preferred, and where R2is in particular phenyl that may or may not carry one or two, especially one, substituent selected from methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, F, fluoromethyl and trifluoromethyl, especially from methyl, F and methoxy. Examples of compounds of subgroup (A1i) of embodiments include, but are not limited to the compounds (I-5), (II-5), (I-6), (II-6), (I-7), (II-7), (II-8) and (II-8) listed in Scheme B below. Scheme B: I-5 I-6 II-5 II-6 In a particular subgroup (A1k) of group (A1) of embodiments R1is C6-C14aryl which is unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1, where Rcyc1has one of the meanings defined herein, in particular one of those mentioned as preferred, and where R1 is in particular phenyl that may or may not carry one or two, especially one, substituent selected from methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, F, fluoromethyl and trifluoromethyl, especially from methyl, F and methoxy; and R2is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra22, where Ra22has one of the meanings defined herein, in particular one of those mentioned as preferred. According to the group (A1k) of embodiment R2is in par- ticular hydrogen or C1-C4alkyl, such as methyl n-propyl or isopropyl. In a particular subgroup (A1l) of group (A1) of embodiments R1is CH2-O-Ra3or CH2-O-ARa4, where A, Ra3and Ra4have one of the meanings de- fined herein, in particular one of those mentioned as preferred. According to these subgroups (A1b) and (A2b), R1is in particular CH2-O-C(O)-R11, CH2-O-C(O)-OR12, CH2-O-C(O)-NHR13, CH2-O-CH2-C(O)-OR12, CH2-O-CH2-CH2-C(O)-OR12or CH2-O-CH2-phenyl, where R11is hydrogen or C1-C4alkyl, such as methyl, and R12and R13are both C1-C4alkyl, such as methyl or tert- butyl, or phenyl which is unsubstituted or carries 1 or 2 radicals Rcyc3, which are es- pecially selected from methyl, phenyl, F and trifluoromethyll; R2is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra22, where Ra22has one of the meanings defined herein, in particular one of those mentioned as preferred. According to the group (A1l) of embodiment R2is in par- ticular hydrogen or C1-C4alkyl, such as methyl n-propyl or isopropyl. Examples of compounds of subgroup (A1l) of embodiments include, but are not limited to the compounds (I-9), (II-9), (I-10), (II-10), (I-11), (II-11), (I-12), (II-12), (I-13), (II-13), (I-14), (II-14), (I-15), (II-15), (I-16), (II-16), (I-17), (II-17), (I-18) and (II-18) listed in Scheme C below. Scheme C: In a particular subgroup (A1m) of group (A1) of embodiments R1is C6-C14aryl which is unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1, where Rcyc1has one of the meanings defined herein, in particular one of those mentioned as preferred, and where R1is in particular phenyl that may or may not carry one or two, especially one, substituent selected from methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, F, fluoromethyl and trifluoromethyl, especially from methyl, F and methoxy; and R2is C6-C14aryl which is unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2, where Rcyc2has one of the meanings defined herein, in particular one of those mentioned as preferred, and where R2is in particular phenyl that may or may not carry one or two, especially one, substituent selected from methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, F, fluoromethyl and trifluoromethyl, especially from methyl, F and methoxy. In a particular subgroup (A2g) of group (A2) of embodiments R1is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra11, where Ra11has one of the meanings defined herein, in particular one of those mentioned as preferred. According to this group (A1h) of embodiments R1is pref- erably hydrogen or C1-C10alkyl, and in particular is hydrogen; R2is a moiety Link-(R4)k, wherein R4is R4bor R4d, k is 1, and Link is a bivalent C6-C14arylene, such as especially phenylene, which is unsubstituted or carries 1 or 2 radi- cals Rcyc2having one of the meanings defined herein, in particular one of those mentioned as preferred. According to this group of embodiments R2is in particu- lar a moiety Link-R4, wherein Link is phenylene and R4is R4bor R4d, respectively. Examples of compounds of subgroup (A26) of embodiments include, but are not limited to the compounds (I-19) and (II-19) listed in Scheme D below. Scheme D: In a particular subgroup (A2h) of group (A2) of embodiments R1is CH2-O-A’-R4, where A’ and R4each have one of the meanings defined herein, in particular one of those mentioned as preferred. According to this embodiment R1is in particular CH2-O-A’-R4, wherein A’ is C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be replaced by phenylene, where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl may be replaced by O, C(O)-O, NH-C(O) or NH- C(O)-O, where phenylene is unsubstituted or substituted by one radical Rcyc4, which is especially methyl, and where R4in case of a compound of formula (I) is a radical of the formula R4aand in case of a compound of formula (II) is of the for- mula R4c; and R2is hydrogen or C1-C10alkyl, which is unsubstituted or substituted by one radical Ra22, where Ra22has one of the meanings defined herein, in particular one of those mentioned as preferred. According to the group (A1h) of embodiment R2is in par- ticular hydrogen or C1-C4alkyl, such as methyl n-propyl or isopropyl. Examples of compounds of subgroup (A1l) of embodiments include, but are not limited to the compounds (I-20), (II-20), (I-21), (II-21), (I-22), (II-22), (I-23), (II-23), (I-24), (II-24), (I- 25), (II-25), (I-26), and (II-26) listed in Scheme E below. Scheme E: I-20 I-21 II-20 II-21 Among the preferred compounds (I-1) to (I-26) of the formula (I) and the preferred compounds (II-1) to (II-26) particular preference is given to the compounds (I-1), (I-2), (I- 3), (I-4), (I-5), (I-6), (I-7), (I-8), (I-12), (I-13), (I-14), (I-15), (I-16), (I-17), (I-18), (I-19) and (I-21) as well as their counterparts of formula (II), i.e. the compounds (II-1), (II-2), (II-3), (II- 4), (II-5), (II-6), (II-7), (II-8), (II-12), (II-13), (II-14), (II-15), (II-16), (II-17), (II-18), (II-19) and (II- 21), as depicted in Schemes A, B, C, E and F above. A particular embodiment (A3) of embodiment (A) relates to the process of the invention, where the substituents R1and R2of the compounds of formulae (I) and (II) have the fol- lowing meanings: R1is CH2-O-Ra33or CH2-O-Link’-(R4)kR2is hydrogen; k is 1 or 2, in particular 1; where Ra33, Link’ and R4are as defined herein, and where Link’ is C1-C10alkandiyl or C1-C10alkantriyl, where one of the CH2groups of C1-C10al- kandiyl and C1-C10alkantriyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene; and where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl and C1-C10alkantriyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where C6-C14arylene and C3-C10cycloalkylene are unsubstituted or carry 1, 2 or 3 radicals Rcyc4; Ra33is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-al- kyl)3, A-Ra4, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl or C3-C14hetaryl, where the 4 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; and R4is a radical of the formulae (R4a), (R4b), (R4c) or (R4d) as defined herein, where Ra4, A are as defined herein, and where Ra4, A especially have alone or in combi- nation the following meanings: Ra4is selected from H, CN, C1-C6-alkyloxy, C1-C6-fluoroalkoxy, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)-OR12, O-C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last men- tioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; A is C1-C9alkandiyl, where one of the CH2groups of C1-C9alkandiyl may be re- placed by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C9alkandiyl may be replaced by O and where C3-C10cy- cloalkylene and C6-C14arylene are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc4. In embodiment (A2) of the process of the invention the variables k, Link’, Ra33, A, Ra4, R11, R12, R13, Rcyc3, Rcyc4, and R4have the following preferred meanings: k is 1; Link’ is C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be re- placed by one phenylene, and where 1, 2 or 3 of the CH2groups of C1-C10al- kandiyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH- C(O)-NH, and where phenylene is unsubstituted or carries 1 or 2 radicals Rcyc4; and Link’ is in particular selected from C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be replaced by phenylene, and where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl may be replaced by O, C(O)-O, NH-C(O) or NH-C(O)-O, and where phenylene is unsubstituted or substituted by 1 radi- cal Rcyc4; Ra33is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, A-Ra4and phenyl which is un- substituted or substituted by 1 or 2 radicals Rcyc3; more preferably from C(O)-R11, C(O)-OR12and A-Ra4; A is C1-C9alkandiyl, where one of the CH2groups of C1-C9alkandiyl may be re- placed by one phenylene, and where 1, 2 or 3 of the CH2groups of C1-C9al- kandiyl may be replaced by O, and where phenylene is unsubstituted or carries 1 or 2 radicals Rcyc4; and A is preferably C1-C4alkandiyl; and in particular is C1-C2alkandiyl, such as methylene or 1,2-ethandiyl; Ra4is selected from C1-C4-alkyloxy, C1-C4-fluoroalkoxy, C(O)-R11, C(O)-OR12, C3-C6cycloalkyl and phenyl, where the 2 last mentioned radicals are unsubsti- tuted or substituted by 1 or 2 radicals Rcyc3; more preferably from C(O)-R11, C(O)-OR12, C3-C6cycloalkyl and phenyl, where the 2 last mentioned radicals are unsubstituted or substituted by 1 or 2 radicals Rcyc3; and in particular from C(O)-OR12and phenyl which is unsubstituted or substituted by 1 or 2 radicals Rcyc3; R11is selected from hydrogen, C1-C4alkyl, C2-C4alkenyl and C1-C4fluoroalkyl; more preferably from methyl, ethyl, C2-C4alkenyl and C1-C2fluoroalkyl; and in partic- ular is methyl, ethyl, ethenyl or 1-propen-2-yl; R12, R13independently of each other are selected from C1-C6alkyl and C1-C4fluoroalkyl; more preferably from C1-C4alkyl and C1-C2fluoroalkyl; and in particular from C1-C4alkyl; Rcyc3, Rcyc4independently of each other are selected from F, Cl, CN, C1-C4-alkyl, C1-C4- fluoroalkyl, C1-C4-alkyloxy, C1-C4-fluoroalkoxy and phenyl; more preferably from F, C1-C2-alkyl, C1-C2-fluoroalkyl, C1-C4-alkyloxy and phenyl; and in particular from F, methyl, fluoromethyl, trifluoromethyl, methoxy and phenyl; and R4in case of a compound of formula (I) is a radical of the formula R4aand in case of a compound of formula (II) is a radical of the formula R4c. The process of this embodiment (A3) enables the preparation of novel endo-unsatu- rated 1,3-dioxol-2-one compounds of formula (I), i.e. the compounds of formula (I) de- fined in embodiment (A3) are novel over the prior art. In a particular embodiment (A3a) of embodiment (A3) the radical R1in formulae (I) and (II) is CH2-O-Ra33, where Ra33is C(O)-R11, C(O)-OR12, C(O)-NHR13or A-Ra4, wherein A, R11, R12, R13and Ra4each have one of the meanings defined herein, in particular one of those mentioned as preferred. According to this embodiment R1is in particular CH2-O-C(O)-R11, CH2-O-C(O)-OR12, CH2-O-C(O)-NHR13, CH2-O-CH2-C(O)-OR12, CH2-O-CH2-CH2-C(O)-OR12or CH2-O-CH2-phenyl, where R12is C1-C4alkyl, such as me- thyl or tert-butyl, and phenyl is unsubstituted or carries 1 or 2 radicals Rcyc3, which are especially selected from methyl, phenyl, F and trifluoromethyl. Accordingly, preferred compounds (I) and (II) of this embodiment (A3b) are the com- pounds of formulae (I-9), (II-9), (I-10), (II-10), (I-11), (II-11), (I-12), (II-12), (I-13), (II-13), (I-14), (II-14), (I-15), (II-15), (I-16), (II-16), (I-17), (II-17), (I-18) and (II-18) as depicted in Scheme C above. In a particular embodiment (A3b) of embodiment (A3) the radical R1in formulae (I) and (II) is CH2-O-Link’-(R4)k, where Link’, k and R4each have one of the meanings defined herein, in particular one of those mentioned as preferred. According to this embodi- ment R1is in particular CH2-O-Link’-(R4)k, wherein k is 1, Link’ is C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be replaced by phenylene, where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl may be replaced by O, C(O)-O, NH-C(O) or NH- C(O)-O, where phenylene is unsubstituted or substituted by one radical Rcyc4, which is especially methyl, and where R4in case of a compound of formula (I) is a radical of the formula R4aand in case of a compound of formula (II) is of the formula R4c. Accordingly, preferred compounds (I) and (II) of this embodiment (A3b) are the com- pounds of formulae (I-20), (II-20), (I-21), (II-21), (I-22), (II-22), (I-23), (II-23), (I-24), (II-24), (I-25), (II-25), (I-26), and (II-26) as depicted in Scheme E above. The process of the invention for preparing an endo-unsaturated 1,3-dioxol-2-one com- pound (1) can be regarded an isomerization of the corresponding 4-methylene-1,3-di- oxol-2-one compound (2). The conversion is effected by reacting the 4-methylene-1,3- dioxol-2-one compound (2) in the presence of a base and the phenolic compound (3). In the process according the invention, the phenolic compounds (3) are generally those of the formula (III), where m is 0, 1, 2 or 3, in particular 0 or 1; n is 0, 1, 2, 3, 4 or 5, in particular 0 or 1; m+n is 0, 1, 2, 3, 4 or 5, in particular 0 or 1; R is selected from the group consisting of halogen, CN, NO2, C1-C10alkyl, C1-C10fluoroalkyl, C1-C10alkoxy, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl, C3-C14hetaryl, C3-C10cycloalkyloxy, C6-C14aryloxy, C3-C10heterocyclyloxy and C3-C14he- taryloxy, where C1-C10alkyl, C1-C10fluoroalkyl, C1-C10alkoxy are unsubstituted or substituted by one or more radicals Raand where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl, C3-C14hetaryloxy, C3-C10cycloalkyloxy, C3-C10heterocyclyloxy, C6-C14aryloxy and C3-C14hetaryloxy are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc, where Rais selected from Cl, Br, CN, and where one of Ramay be C1-C4-alkoxy, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc; and Rcycis selected from the group consisting of F, Cl, Br, CN, NO2, C1-C4-alkyl and C1-C4-alkoxy. Preference is given to phenolic compounds of the formula (III) wherein the variables m, n and R, and if present the radicals Raand Rcyc, have the following meanings: m is 0 or 1, in particular 0; n is 0 or 1; m+n is 0 or 1; R is selected from the group consisting of F, Cl, CN, NO2, C1-C4alkyl, C1-C4fluoroal- kyl and C1-C4alkoxy, in particular from F, Cl, methyl, ethyl, fluoromethyl and meth- oxy, and specifically from F, Cl, methyl and methoxy; Raif present, is selected from Cl and CN, and in particular is Cl; Rcycif present, is selected from F, Cl, Br CN, NO2, methyl and methoxy, and in particu- lar from F, Cl, methyl and methoxy. As apparent from the foregoing, preference is given to phenolic compounds (III) which are unsubstituted, i.e. m = n = 0, or carry either one substituent R or a further hydroxyl group, i.e. m = 1 and n = 0, or m = 0 and n = 1. I n case the phenolic compound of formula (III) bears a substituent R and / or a further hy- droxyl group, i. e. n+m ≠ 0, the further substituent is preferably not located in the ortho position of the OH group. In particular, if n+m = 1, the further substituent R or the hy- droxyl group are preferably in position 4 of formula (III). The phenolic compound (3) used in the process of the invention preferably has a pKa of at least 16.5, and in particular a pKa in the range of 16.5 to 20, where the pKa is deter- mined as a solution of the phenolic compound in dimethylsulfoxide at 25°C and 1 bar. Typically the pKa values of the phenolic compounds (3) are measured spectrophotomet- rically against indicator in analogy to the methods described e.g. in W. S. Matthews et al., J. Am. Chem. Soc. 1975, 97, 7006-7014 and W. N. Olmstead et al., J. Org. Chem. 1980, 45, 16, 3295-3299. Correspondingly determined experimental pKa values of some phe- nolic compounds potentially suitable as phenolic compounds (3) for the process of the invention can be taken for example from the following references: F. G. Bordwell et al., J. Org. Chem. 1991, 56, 4218-4223; B. Valter et al., Collect. Czech. Chem. Commun. 1985, 50, 834-839; F. G. Bordwell, Acc. Chem. Res. 1988, 21, 456-463; F. G. Bordwell et al., J. Org. Chem. 1981, 46, 632-635. If no experimentally determined pKa values for potential phenolic compounds (3) are available, corresponding pKa values in DMSO were calculated via DFT calculations ac- cording the following method: Geometry optimizations and Hessian calculations were carried out with the TURBOMOLE program (TURBOMOLE Version 7.5.2, 2021, a devel- opment of University of Karlsruhe and Forschungszentrum Karlsruhe GmbH, TURBO- MOLE GmbH, available from http: / / www.turbomole.com using the meta-GGA M06-L (see: Y. Zhao et al., J. Chem. Phys. 2006, 125) in combination with the def2-SVP basis set and the D3 dispersion correction with zero-damping ( see e.g.: F. Weigend et al., Phys. Chem. Chem. Phys. 2005, 7, 3297-3305; and S. Grimme et al., J. Chem. Phys. 2010, 132). These calculations were performed with the COSMO solvation model applying default parameters and an infinite dielectric constant (see e.g.: A. Klamt et al., J. Chem. Soc., Per- kin Trans. 21993, 799-805). Stationary points were verified via analysis of the vibrational frequencies at the same level of theory. Final electronic single point energies were ob- tained using the M06-2X functional along with the def2-QZVPP basis set (see e.g.: F. Weigend et al., Phys. Chem. Chem. Phys. 2005, 7, 3297-3305; Y. Zhao et al. Theor. Chem. Acc. 2007, 120, 215-241; and F. Weigend et al., J. Chem. Phys. 2003, 119, 12753- 12762). The resolution-of-identity (RI) approximation and the corresponding auxiliary basis sets were applied throughout all calculations (see e.g.: P. Deglmann et al., Chem. Phys. Lett. 2004, 384, 103-107; K. Eichkorn et al., Chem. Phys. Lett. 1995, 240, 283-290; O. Vahtras et al., Chem. Phys. Lett. 1993, 213, 514-518; and F. Weigend, Phys. Chem. Chem. Phys. 2006, 8, 1057-1065). For the computation of Gibbs free energies, zero-point vibrational energies and thermo- dynamic corrections were obtained at the level of geometry optimization (at T = 298.15^K and p = 1^bar). The solvation contribution was calculated using the COSMO-RS model in the COSMOtherm program (Version 18.0.0; Revision 4360) for infinite dilution in DMSO (see e.g.: A. Klamt, J. Phys. Chem. 1995, 99, 2224-2235; A. Klamt et al., J. Phys. Chem. A 1998, 102, 5074-5085; and COSMOtherm Version 18.0.0 (Revision 4360), COS- MOlogic GmbH & Co KG, available from http: / / www.cosmologic.de. All pKa values were calculated using a proton exchange scheme referenced to phenol (pKa=18.0) using the following equations (see e.g.: J. Ho et al., J. Phys. Chem. B 2016, 120, 1319-1329; and J. Ho et al., J. Org. Chem. 2017, 82, 10732-10736): ∆ ^^^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ ^^ℎ ^^ ^^ ^^ ^^= ∆ ^^^^ ^^ ^^ ^^+ ∆ ^^^^−− ∆ ^^^^ ^^ ^^−− ∆ ^^^^ ^^ The phenolic compound (3) used in the process of the invention is preferably selected from phenol, 4-methylphenol, 4-methoxyphenol, 4-fluorophenol and 4-chlorophenol and combinations of phenolic compounds (3) comprising at least one of phenol, 4- methylphenol, 4-methoxyphenol, 4-fluorophenol and 4-chlorophenol. Specific prefer- ence is given to phenolic compounds (3) selected from phenol, 4-methylphenol, 4-fluor- ophenol and mixtures thereof. Especially, the phenolic compound (3) in the process of the invention is unsubstituted phenol. The base used in the process according the invention is preferably selected from amines, alkalimetal carbonates and mixtures thereof. Suitable amines are bases wherein the site of basicity is a nitrogen atom. Suitable amines are compounds of the formula A, described hereinafter, NRxRyRz(A) where Rxis C1-C10alkyl, C5-C10cycloalkyl, C2-C10alkenyl, C2-C10alkinyl, C5-C10aryl or C3-C10hetaryl, Ryis hydrogen, C1-C10alkyl, C5-C10cycloalkyl, C2-C10alkenyl, C2-C10alkinyl, C5-C10aryl or C3-C10hetaryl, Rzis hydrogen, C1-C10alkyl, C5-C10cycloalkyl, C2-C10alkenyl, C2-C10alkinyl, C5-C10aryl or C3-C10hetaryl, or Rxand Rytogether with the nitrogen atom may form a 5 to 10 membered, saturated or unsaturated N-heterocycle, which is monocyclic and may additionally have 1, 2 or 3 ring member selected from O, N and NRzz, and where the carbon atoms of the N-heterocy- cle may be unsubstituted or substituted by 1, 2, 3 or 4 C1-C4alkyl radicals; or Rx, Ryand Rztogether with the nitrogen atom may form a 5 to 10 membered, saturated or unsaturated N-heterocycle, which is bicyclic or tricyclic and may additionally have 1, 2 or 3 ring member selected from O, N and NRzz, and where the carbon atoms of the N- heterocycle may be unsubstituted or substituted by 1, 2, 3 or 4 C1-C4alkyl radicals; or Rx, Ryand Rztogether with the nitrogen atom may form a 6 or 10 membered, aromatic N-heterocycle, which may have 1, 2 or 3 further nitrogen atoms ring member and where the carbon atoms of the aromatic N-heterocycle may be unsubstituted or substituted by 1, 2, 3 or 4 C1-C4alkyl radicals; and where Rzzis hydrogen or C1-C10alkyl. Specific examples of suitable amines of the formula (A) include, but are not limited to, ethylamine, n-propylamine, diethylamine, diisopropylamine, triethylamine, dimethylcy- clohexylamine, diisopropylethylamine, pyrollidine, piperidine, morpholine, piperazine, N- methyl pyrrolidine, N-methyl piperidine, N-methyl morpholine, N,N'-dimethyl pipera- zine, pyridine, 2-picoline, 3-picoline, 4-picoline, 5-ethyl-2-methylpyridine, 2-ethylpyri- dine, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4-lutidine, 3,5-lutidine, 2,4,6- collidine, 2,3,5-collidine, pyrimidine, 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,8-diazabi- cyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,5,7-triazabicy- clo[4.4.0]dec-5-ene (TBD) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MeTBD). Suitable alkalimetal carbonates are typically lithium carbonate, sodium carbonate, potas- sium carbonate and cesium carbonate, and in particular cesium carbonate. For use as the base in the process according to the invention, preference is given to amine bases selected from the group of amidine bases and guanidine bases. Preferred amidine bases and guanidine bases are those of the formula B where the curved line together with the NRq-CRP=N indicates a 6-membered heterocy- cle which is aromatic or non-aromatic, such as pyrimidinyl or 1,4,5,6-tetrahydropyrimi- dine-1,2-diyl, where Rpis hydrogen or C1-C4alkyl, such as methyl, and Rqhas the following meanings: (a) if the nitrogen to which Rqis bound is a non-aromatic heterocycle Rqis C1-C4alkyl or Rqtogether with Rpand the N-C group to which Rpand Rqare bound form a 5- to 7-membered saturated heterocycle, which in addi- tion to the carbon atoms and the N atom forming the heterocycle may bear a group NRsas a further ring member where Rsis hydrogen or C1-C4alkyl, such as methyl; (b) if the nitrogen to which Rqis bound is an aromatic heterocycle Rqis absent. Preferred amidine bases and guanidine bases, in particular those of the formula B in- clude pyrimidine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non- 5-ene (DBN), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 7-methyl-1,5,7-triazabicy- clo[4.4.0]dec-5-ene (MeTBD), and mixtures thereof. Especially preferred bases for the process of the invention are selected from the group consisting of DBU, DBN, TBD, MeTBD and mixtures thereof. Particular preference is given in this context to TBD. Also preferred are carbonate bases, in particular alkalimetal carbonates and especially cesium carbonate. In process of the invention the isomerization reaction of the compound (2) into the compound (1) is typically carried out in catalytic amounts of the phenolic compound (3) and the base. Catalytic amount means that the relative amount of both the phenolic compound (3) and the base is less than 0.8 mol per 1 mol of the compound 2, typically at most 0.5 mol, preferably at most 0.2 mol or 0.15 mol per one mol of the 4-meth- ylene-1,3-dioxol-2-one compound (2) and typically at least 0.00001 mol, especially at least 0.0001 mol or 0.001 mol per 1 mol of the 4-methylene-1,3-dioxol-2-one compound (2) It was found beneficial if the phenolic compound (3) is used in an amount of 0.001 to 0.5 mol, preferably 0.001 to 0.2 mol, and in particular 0.01 to 0.15 mol, per 1 mol of the 4- methylene-1,3-dioxol-2-one compound (2). It was found beneficial if the base is used in an amount of 0.00001 to 0.5 mol, preferably 0.0001 to 0.1 mol, and in particular 0.001 to 0.05 mol, per 1 mol of the 4-methylene-1,3- dioxol-2-one compound (2). In the process of the invention the molar ratio of the phenolic compound (3) to the base used in the isomerization reaction is preferably in the range of 50:1 to 1:10, preferably 20:1 to 1:10 and in particular 10:1 to 1:7. The reaction of process according to the invention may be carried out in an organic sol- vent, such as especially an aprotic organic solvent, or without solvent. Preferably, the re- action is carried out in an organic solvent. It has generally been found to be advantageous to use an aprotic organic solvent for the reaction of the process of the invention. Useful aprotic organic solvents here include aliphatic hydrocarbons, such as pentane, hexane, heptane, octane and cyclohexane; aro- matic hydrocarbons, such as benzene, toluene, the xylenes, ethylbenzene, mesitylene and benzotrifluoride; halogenated hydrocarbons, such as dichloromethane; amides, such as dimethylformamide, diethylformamide, N-methylpyrrolidone, N-ethylpyrroli- done and dimethylacetamide; ureas, such as tetramethylurea, N,N-dimethylimidazoli- none (DMI) and N,N-dimethylpropyleneurea (DMPU); nitriles, such as acetonitrile and propionitrile; sulfoxides, such as dimethyl sulfoxide; sulfones, such as sulfolane; esters, such as methyl acetate, ethyl acetate and t-butyl acetate; carbonates, such as diethyl carbonate, ethylene carbonate and propylene carbonate; ethers, for example aliphatic C3-C10-ethers having 1, 2, 3, or 4 oxygen atoms, such as ethylene glycol dimethyl ether (glyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), diethyl ether, diisopropyl ether, dibutyl ether, methyl isobutyl ether, tert-butyl methyl ether and tert-butyl ethyl ether, alicyclic C4-C6-ethers, such as tetrahydrofuran (THF), tetrahydropyran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran and 1,4-diox- ane; and mixtures of these solvents with one another. The solvent for the reaction of the process of the invention is preferably selected from dichloromethane, dimethylformamide, acetonitrile, diethylether, THF and 2-methyltetra- hydrofuran, and more preferably from acetonitrile, diethylether, THF and 2-methyltetra- hydrofuran, and in particular is acetonitrile. The total amount of the solvent used in the reaction of the process according to the in- vention is typically in the range from 0.2 to 7 kg and preferably in the range from 0.5 to 5 kg, based on 1 mol of the compound (2). Preference is given to using solvents which are essentially anhydrous, i.e. have a water content of less than 1000 ppm and especially not more than 200 ppm. The reactants can in principle be contacted with one another in any desired sequence. For example, the phenolic compound (3) and the base, if appropriate in dissolved or dis- persed form, can be initially charged and mixed with each other. The obtained mixture can then be admixed with the 4-methylene-1,3-dioxol-2-one compound (2). Conversely, the 4-methylene-1,3-dioxol-2-one compound (2), if appropriate in dissolved or dis- persed form, can be initially charged and admixed with a mixture of the phenolic com- pound (3) and the base. Alternatively, all reactants can also be added simultaneously to the reaction vessel. As an alternative to the joint addition of the phenolic compound (3) and the base, they can also be added separately to the reaction vessel. Both of them can independently of one another be added, either in a solvent or in bulk, before or af- ter the addition of the 4-methylene-1,3-dioxol-2-one compound (2). It has been found to be beneficial to initially charge the reaction vessel with the 4-meth- ylene-1,3-dioxol-2-one compound (2) as such or in dissolved form, then to successively add a phenolic compound (3) and the base each in dispersed or preferably in dissolved form, and finally to admix the obtained mixture with the remaining amount of the sol- vent. In general, the reaction of process of the invention is performed under temperature control. The reaction is typically effected in a reaction vessel with stirring apparatus. The reaction temperature of reaction of process A depends on different factors, such as the reactivity of the phenolic compound (3), and can be determined by the person skilled in the art in the individual case, for example by simple preliminary tests. In general, the conversion of process of the invention is performed at a temperature in the range from -10 to 120°C, preferably in the range from 0 to 100°C, more preferably in the range from 10 to 80°C and specifically in the range from 10 to 50°C. Depending on the solvent used, on the reaction temperature and on whether the reac- tion vessel possesses a vent, a pressure of generally 1 to 5 bar and preferably of 1 to 2 bar is established during the reaction. The isomerization reaction of the process according to the present invention as de- scribed herein may be carried out continuously or batchwise. The isomerization reaction is usually carried out in a reaction vessel customary for such reactions. Suitable reactors for a continuous and batchwise reaction are known to those skilled in the art and are described, for example, in Ullmanns Enzyklopädie der technischen Chemie, vol. 1, 3rd Edition, 1951, p. 743 ff. Preference is given to using a cascade of stirred vessels or a tube reactor for the continuous variant of the process of the present invention. Suitable reac- tors for the semicontinuous or continuous embodiment, which may be pressure-rated, are known to those skilled in the art and are described, for example, in Ullmanns En- zyklopädie der technischen Chemie, volume 1, 3rd Edition, 1951, p. 769 ff. According to a one embodiment an autoclave is employed for the reaction which may have an internal stirrer and an internal lining. The reaction can be carried out in a continuous, semicon- tinuous or batchwise manner. Preference is given to a continuous process. In principle, the reaction can be performed under a pressure in the range of 0.1 to 50 bar, preferably in the range of 0.5 to 2 bar and more preferably under ambient pressure. It may be benefical to run the reaction under the atmosphere of an inert gas, such as carbon dioxide, nitrogen, argon or a mixture thereof. The work-up of the reaction mixtures obtained in the reaction of process of the inven- tion and the isolation of the endo-unsaturated 1,3-dioxol-2-one compound (1), are ef- fected in a customary manner, for example by an aqueous extractive work-up or by re- moving the solvent, for example under reduced pressure. The endo-unsaturated 1,3-di- oxol-2-one compound (1) may be obtained in sufficient purity by applying such measures or a combination thereof. In this case, additional purification steps, in particu- lar elaborated ones such as chromatography or distillation are usually not necessary. Al- ternatively, further purification can be effected by methods commonly used in the art, such as chromatography. Preferably the reaction mixture obtained in the reaction of the process of the invention, for work-up, is concentrated by removing all or most of the solvent and then the ob- tained raw product is subjected to one or more purification steps, such as especially sil- ica gel column chromatography using a gradient eluent, such as e.g. 2 to 10%, 5 to 30% or 10 to 50% of ethyl acetate in hexane. In one embodiment the work-up of the reaction mixture obtained in the reaction of the process according to the invention involves recycling of the phenolic compound (3) and / or the base. The 4-methylene-1,3-dioxol-2-one compounds of the formula (II) employed in the pro- cess of the invention as starting materials are accessible by different synthetic routes known from the prior art. In the context of the present invention the compounds of for- mula (II) are preferably prepared via carboxylation of the corresponding propargylic al- cohols as described for example in C. Johnson et al., ChemCatChem 2021, 13, 353-361; S. Dabral et al., Green Chem. 2020, 22, 1553-1558; S. Dabral et al., Org. Lett.2019, 21, 1422- 1425, WO 2021 / 144162, WO 2019 / 219469 and WO 2019 / 034648. Such a carboxylation reaction for preparing the compounds of formula (II) of the present invention starting from corresponding propargylic alcohols of formula (III) is shown in Scheme 1 below. Scheme 1: The process of the present invention allows for the straightforward and efficient prepa- ration of high-quality endo-unsaturated 1,3-dioxol-2-one compounds of the formula (I) in high purity. Thus, the compounds of formula (I) obtained this way are useful for a va- riety of applications, such as electrolyte additives in electrochemical storage systems, as building blocks in organic synthesis of active compounds for pharmaceutical and agri- cultural applications, as reactive diluent in the manufacture of epoxy resins, or as mono- mers in polymer applications. The present invention further relates to endo-unsaturated 1,3-dioxol-2-one compounds (1), which are compounds of the formula (Ia), where R5is Ra33or Link’-(R4)k; k is 1 or 2, in particular 1; Link’ is as defined above in the context of the formula (I) and in particular C1-C8al- kandiyl or C1-C8alkantriyl, where one of the CH2groups of C1-C8alkandiyl and C1-C8alkantriyl may be replaced by one of C6-C14arylene and C3-C10cycloal- kylene; and where 1, 2 or 3 of the CH2groups of C1-C8alkandiyl and C1-C8alkantriyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where C6-C14arylene and C3-C10cycloalkylene are unsubstituted or carry 1, 2 or 3 radicals Rcyc4; Ra33is as defined above in the context of the formula (I) and e. g. selected from C(O)- R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, A-Ra4, C3-C10cyclo- alkyl, C6-C14aryl, C3-C10heterocyclyl or C3-C14hetaryl, where the 4 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; and Ra4is as defined above in the context of the formula (I) and e. g selected from H, CN, C1-C6-alkyloxy, C1-C6-fluoroalkoxy, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)- OR12a, O-C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; A is C1-C9alkandiyl, where one of the CH2groups of C1-C9alkandiyl may be re- placed by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C9alkandiyl may be replaced by O and where C3-C10cy- cloalkylene and C6-C14arylene are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc4; R4is a radical of the formula (R4aa) and where Rcyc3, Rcyc4are as defined above in the context of formula (I) and in particular, inde- pendently of each other, selected from the group consisting of F, Cl, Br, CN, NO2, C1-C10alkyl, C1-C10fluoroalkyl, C1-C10alkyloxy, C1-C10fluoroalkoxy, C(O)-R11, O-C(O)-R11, C(O)-OR12a, O-C(O)-OR12, C(O)-NHR13and O-C(O)-NHR13and C6-C14aryl; R11is selected from hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl; and R12, R12a, R13independently of each other are selected from C1-C10alkyl, C1-C10fluoroalkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl, where R12amay also be hydrogen. The endo-unsaturated 1,3-dioxol-2-one compounds of the formula (Ia) can be obtained by the process of the present invention, starting from the 4-methylene-1,3-dioxol-2-one compounds of formula (II) which are defined in the group (A3) of embodiment of the in- vention described above. Compounds of the formula (Ia) which bear a radical C(O)-OR12a, where R12ais hydrogen, can be obtained from the compounds of the formula (Ia) which bear a radical C(O)- OR12a, where R12ais different from hydrogen, e. g. C1-C10alkyl or C2-C10alkenyl by hydro- lytic or thermolytic cleavage of the ester groups according to conditions well known in the art. Preferred meanings of k, Link’, Ra33, A, Ra4, R11, R12, R12a, R13, Rcyc3, and Rcyc4defined in the context of the formula (I) apply in the same way to formula (Ia). A preferred group (B) of embodiments of the invention relates to those endo-unsatu- rated 1,3-dioxol-2-one compounds of the formula (Ia), wherein the variables k, Link’, Ra33, A, Ra4, R11, R12, R13, Rcyc3, and Rcyc4have the following meanings: k is 1; Link’ is C1-C8alkandiyl, where one of the CH2groups of C1-C8alkandiyl may be re- placed by one phenylene, and where 1, 2 or 3 of the CH2groups of C1-C8al- kandiyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH- C(O)-NH, and where phenylene is unsubstituted or carries 1 or 2 radicals Rcyc4; and Link’ is in particular selected from C1-C8alkandiyl, where one of the CH2groups of C1-C8alkandiyl may be replaced by phenylene, and where 1, 2 or 3 of the CH2groups of C1-C8alkandiyl may be replaced by O, C(O)-O, NH-C(O) or NH-C(O)-O, and where phenylene is unsubstituted or substituted by 1 radical Rcyc4; Ra33is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, A-Ra4and phenyl which is un- substituted or substituted by 1 or 2 radicals Rcyc3; more preferably from C(O)-R11, C(O)-OR12and A-Ra4; A is C1-C9alkandiyl, where one of the CH2groups of C1-C9alkandiyl may be re- placed by one phenylene, and where 1, 2 or 3 of the CH2groups of C1-C9al- kandiyl may be replaced by O, and where phenylene is unsubstituted or carries 1 or 2 radicals Rcyc4; and A is preferably C1-C4alkandiyl; and in particular is C1-C2alkandiyl, such as methylene or 1,2-ethandiyl; Ra4is selected from C1-C4-alkyloxy, C1-C4-fluoroalkoxy, C(O)-R11, C(O)-OR12, C3-C6cycloalkyl and phenyl, where the 2 last mentioned radicals are unsubsti- tuted or substituted by 1 or 2 radicals Rcyc3; more preferably from C(O)-R11, C(O)-OR12, C3-C6cycloalkyl and phenyl, where the 2 last mentioned radicals are unsubstituted or substituted by 1 or 2 radicals Rcyc3; and in particular from C(O)-OR12and phenyl which is unsubstituted or substituted by 1 or 2 radicals Rcyc3; R11is selected from hydrogen, C1-C4alkyl, C2-C4alkenyl and C1-C4fluoroalkyl; more preferably from methyl, ethyl, C2-C4alkenyl and C1-C2fluoroalkyl; and in partic- ular is methyl, ethyl, ethenyl or 1-propen-2-yl; R12ais selected from hydrogen, C1-C6alkyl and C1-C4fluoroalkyl; more preferably from hydrogen, C1-C4alkyl and C1-C2fluoroalkyl; and in particular from hydro- gen and C1-C4alkyl; R12, R13independently of each other are selected from C1-C6alkyl and C1-C4fluoroalkyl; more preferably from C1-C4alkyl and C1-C2fluoroalkyl; and in particular from C1-C4alkyl; Rcyc3, Rcyc4independently of each other are selected from F, Cl, CN, C1-C4-alkyl, C1-C4- fluoroalkyl, C1-C4-alkyloxy, C1-C4-fluoroalkoxy and phenyl; more preferably from F, C1-C2-alkyl, C1-C2-fluoroalkyl, C1-C4-alkyloxy and phenyl; and in particular from F, methyl, fluoromethyl, trifluoromethyl, methoxy and phenyl; and R4in case of a compound of formula (I) is a radical of the formula R4aand in case of a compound of formula (II) is a radical of the formula R4c. A particularly preferred subgroup (B1) of the group (B) of embodiments relates to com- pounds (Ia) wherein the radical R1is CH2-O-Ra33where Ra33is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13and A-Ra4, wherein A, Ra4, R11, R12, R12aand R13each have one of the meanings defined herein, in particular one of those mentioned as preferred. Accord- ing to this embodiment R1is in particular CH2-O-C(O)-R11, CH2-O-C(O)-OR12, CH2-O-C(O)-NHR13, CH2-O-CH2-C(O)-OR12a, CH2-O-CH2-CH2-C(O)-OR12aor CH2-O-CH2-phenyl, where R11is as defined above, and where R11is especially hydrogen or C1-C4alkyl, such as methyl, ethyl or tert.-butyl, R12and R13are as defined above and are especially both C1-C4alkyl, such as methyl or tert-butyl, and phenyl, which is unsub- stituted or carries 1 or 2 radicals Rcyc3, which are especially selected from methyl, phenyl, F and trifluoromethyl and R12ais as defined above, and where R12ais especially hydrogen or C1-C4alkyl, such as methyl, ethyl or tert.-butyl. Accordingly, preferred compounds (Ia) of this embodiment (B1) are the compounds of formulae (I-9), (I-10), (I-11), (I-12), (I-13), (I-14), (I-15), (I-16), (I-17) and (I-18) as depicted in Scheme D above, and the compounds of the formulae (I-11a) and (I-12a): I-11a II-12a A further particularly preferred subgroup (B2) of the group (B) of embodiments relates to compounds (Ia) wherein the radical R1is CH2-O-Link’-(R4)k, where R4is a moiety R4aaand Link’ and k each have one of the meanings defined herein, in particular one of those mentioned as preferred. According to this embodiment R1is in particular CH2-O-Link’-(R4aa)k, wherein k is 1, Link’ is C1-C8alkandiyl, where one of the CH2groups of C1-C8alkandiyl may be replaced by phenylene, where 1, 2 or 3 of the CH2groups of C1-C8alkandiyl may be replaced by O, C(O)-O, NH-C(O) or NH-C(O)-O, where phe- nylene is unsubstituted or substituted by one radical Rcyc4, which is especially methyl. Accordingly, preferred compounds (Ia) of this embodiment (B3) are the compounds of formulae (I-20), (I-21), (I-22), (I-23), (I-24), (I-25), and (I-26) as depicted in Scheme E above. The compounds (I) and in particularly also the novel compounds (Ia) of the invention are readily accessible by the process of the invention in excellent quality and high purity. Ac- cordingly, they are valuable for various uses, such as electrolyte additives in batteries, as building blocks for synthesizing pharmaceutical and agricultural actives, as monomers in polymerization reactions and as reactive diluent in the manufacture of epoxy resins. Hence, a further aspect of the present invention is the use of the endo-unsaturated 1,3- dioxol-2-one compounds of the formula (I) as electrolyte additives in electrochemical storage systems, as reactive diluent, as synthetic building blocks and as monomers in polymerisations. It was surprisingly found that endo-unsaturated 1,3-dioxol-2-one compounds (1) of the formula (Ia), where R5is a moiety Link’-(R4)kas described above are susceptible to react with poly- functional compounds having at least 2, e. g. 2, 3 or 4 functional groups FG selected from the group of hydroxyl groups, i. e. OH, primary amino groups, i. e. NH2, secondary amino groups, i. e. NHRN, with RNbeing e. g. C1-C8-alkyl, C1-C4-alkoxy-C1-C4-alkyl, C3-C6- cycloalkyl-C1-C4-alkyl or C3-C8-cycloalkyl, and mercapto groups SH, to form oligomers or polymers by a polyaddition reaction of the functional groups FG to the 1,3-dioxol-2-one moiety. The polyfunctional compounds having at least 2, e. g. 2, 3 or 4 functional groups FG are hereinafter also referred to as polyfunctional compounds or simply as compounds PFC. Therefore, a further aspect of the present invention is the use of a compound of the for- mula (Ia), where R5is a moiety Link’-(R4)kas monomer in the polymerization with at least one polyfunctional compound PFC as described herein. The polyaddition reaction is typically followed by a ring-opening reaction and optionally a ring-closing reaction in case of FG being a primary amino group. For k = 1 the com- pound of the formula (Ia) forms repeating units of the following formula (IIIa) which alternate with repeating units formed by the polyfunctional compound, where Link’ is as defined for the formula (Ia) and where X is O, S, NH or NRN. Typical polyfunctional compounds having at least 2, e. g. 2, 3 or 4 functional groups FG are ,for example, selected from the group of - aliphatic diols and triols, such as 1,2-ethandiol, 1,2- and 1,3-propandiol, 1,4-bu- tandiol, diethylene glycol, dipropylene glycol, triethylene glycol, trimethylol pro- pane, pentarerythrit, - aliphatic diols and triols, such as 1,4-cyclohexanediol, 1,2-, 1,3- or 1,3-bis(hy- droxymethyl)cyclohexane, - polyetherglycols, such as polyethylene glycol, polypropylene glycol and polytet- rahydrofurane having molecular weights in the range of 150 to 5000 dalton (number average), - aliphatic diamines, such as ethylene diamine, 1,3-propanediamine, 1,4-butanedi- amine, 1,5-pentanediamine, 1,6-hexanediamine, 1,8-octanediamine and the cor- responding N,N’-dialkyl derivatives thereof, such as N,N’-dimethyl-1,2-dia- minoethane, N,N’-dimethyl-1,2-diaminopropane, N,N’-dimethyl-1,3-diaminopro- pane, N,N’-dimethyl-1,4-diaminobutane, N,N’-dimethyl-1,4-diaminobutane, N,N’-dimethyl-1,4-diaminopentane, N,N’-dimethyl-1,6-diaminohexane, - polyetheramines and Jeffamines, - cycloaliphatic diamines, such as 1,2- or 1,4-diaminocyclohexane, 1,2-, 1,3- or 1,3- bis(aminomethyl)cyclohexane, isophorone diamine, bis(4-aminomethylcyclo- hexyl)methane. The polymererization of the compound of formula (Ia) with the compound PFC can be carried out in substance or in an inert organic solvent. Typical inert organic solvents are aprotic solvents including hydrocarbon solvents, such alkanes, e.. g. hexane, heptanes or octanes, cycloalkanes, such as cyclohexane, cycloheptane and cyclooctane, aromatic hy- drocarbons, such as benzene, toluene or hexane, halogenated hydrocarbons, such as dichloromethane, dichloroethane, polar aprotic solvents, such as nitriles, e. g. acetoni- trile, propionitrile, butyronitrile, aliphatic and alicyclic ethers, such as tetrahydrofurane, dioxane, cyclic carbonates, such as ethylene carbonate and propylene carbonate and mixtures of the aforementioned solvents. The polymerization may be catalized by basic catalysts, such amidine bases and tertiary amines. The following examples serve as further illustration of the invention. 1. Abbreviations: equiv.: molar equivalent(s) THF: tetrahydrofuran MeOH: methanol CH3CN: acetonitrile EtOAc: ethyl acetate DCM: dichloromethane DMF: dimethylformamide AgOAc: silver(I) acetate DavePhos: 2-dicyclohexylphosphino-2’-(N,N-dimethylamino)-biphenyl TBD: 1,5,7-triazabicyclo[4.4.0]dec-5-ene MeTBD: 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene DBN: 1,5-diazabicyclo[4.3.0]non-5-ene DABCO: 1,4-diazabicyclo[2.2.2]octane DMAP: 4-dimethylaminopyridine protone sponge: 1,8-bis(dimethylamino)naphthalene Et3N: triethylamine Cs2CO3: cesium carbonate NaOH: sodium hydroxide 1,1,1,3,3,3-hexafluoro-2-propanol: HFP NH4Cl: ammonium chloride Na2SO4: sodium sulfate HCl: hydrochloric acid n.d.: not determined rt:: room temperature (22-25°C) 2. Analytic methods NMR-spectra were recorded on Bruker AV-300, AV-400, AV-500 or AV-600 spectrome- ters. The residual solvent signals were used as references for1H- and13C-NMR spectra (CDCl3: δH = 7.26 ppm, δC = 77.16 ppm, CD2Cl2: δH = 5.32 ppm, δC = 53.84 ppm).19F- NMR spectra were not calibrated by an internal reference. FT-IR measurements were carried out on a Mettler Toledo React IR 10 spectrometer. Ex- act mass analyses were performed by the Mass Spectrometry Laboratory at the Institute of Organic Chemistry / Heidelberg University. 3. Preparation Examples 3.1 Preparation of a propagylic alcohol of formula (III) III-19 A solution of ethynylmagnesium bromide (0.5 M in THF, 40 mL, 20 mmol, 2.7 equiv.) was added at 0 °C to a solution of terephthalaldehyde (1.006 g, 7.5 mmol) in THF (75 mL). After the mixture had been stirred for 4 h at room temperature, a saturated solu- tion of NH4Cl (40 mL) was added and the THF was evaporated under vacuum. The aqueous phase was extracted three times with ethyl acetate and the organic layers were washed with water and brine and then dried with Na2SO4. After evaporation of the sol- vent, the resulting crude product was purified by column chromatography (cyclohex- ane / ethyl acetate 2:1) to give the expected diol in pure form as a yellow solid (1.229 g, 6.6 mmol). Yield 88 %.1H NMR (500 MHz, MeOD) δ 7.53 (s, 4H), 5.41 (d, J = 2.3 Hz, 2H), 3.01 (d, J = 2.3 Hz, 2H);13C NMR (126 MHz, MeOD) δ 142.37, 127.81, 85.06, 75.38, 64.41. 3.2 Preparation of 4-methylene-1,3-dioxol-2-one compounds of formula (II) The 4-methylene-1,3-dioxol-2-one compounds of formulae II-3, II-5, II-6, II-7, II-8, II-19, II-17 and II-18 (see Schemes A, B, C and E above) were prepared starting from the corre- sponding propargylic alcohol of formula III-2, III-3, III-5, III-6, III-7, III-8, III-19, III-17 and III-18, respectively, using the following general procedure. (III) (II) Propargylic alcohol of formula III-3, III-5, III-6, III-7, III-8, III-9, III-18 or III-19 (2 mmol), AgOAc (3.3 mg, 1 mol%), DavePhos (7.8 mg, 1 mol%) and CH3CN (4 mL) were added in an 8 mL microwave vial with a crimp cap and septum that was pierced with a needle. This vial was then put into a stainless-steel multi-reactor (from HEL Ltd.). The reactor was purged twice with carbon dioxide (20 bar) and then charged with carbon dioxide (20 bar). The reaction mixture was stirred at 30 °C for 16-24 h and then carefully depressur- ized. The solvent was removed in vacuo and the resulting crude product was purified by flash chromatography employing 20-30% EtOAc in hexane as a gradient eluent. By means of this general procedure the following compound of formula (II) were obtained: Compound (II-3) Colorless oil, 213.1 mg (yield: 75%); Rf(EtOAc / hexane 1:5) = 0.5;1H NMR (301 MHz, CDCl3) δ 5.02 (dt, J = 3.7, 2.1 Hz, 1H), 4.90 (dd, J = 3.9, 2.3 Hz, 1H), 4.35 (dd, J = 3.8, 1.9 Hz, 1H), 2.02 (ddp, J = 10.5, 6.9, 3.6 Hz, 1H), 1.08 (d, J = 6.9 Hz, 3H), 0.99 (d, J = 6.9 Hz, 3H);13C NMR (76 MHz, CDCl3) δ 152.27, 87.58, 84.32, 32.84, 17.68, 15.11. Compound (II-5) Yellow oil, 300 mg (yield: 85%); Rf(EtOAc / hexane 1:5) =0.37;1H NMR (301 MHz, CDCl3) δ 7.51 - 7.35 (m, 5H), 6.08 (t, J = 2.3 Hz, 1H), 4.98 (dd, J = 4.0, 2.5 Hz, 1H), 4.31 (dd, J = 4.0, 2.1 Hz, 1H);13C NMR (76 MHz, CDCl3) δ 153.20, 151.91, 134.93, 130.40, 129.34, 127.44, 89.39, 81.48. Compound (II-6) White solid, 330.9 mg (yield: 87%); Rf(EtOAc / hexane 1:5) =0.51;1H NMR (400 MHz, CDCl3) δ 7.35 - 7.23 (m, 4H), 6.07 (t, J = 2.3 Hz, 1H), 4.99 (dd, J = 3.9, 2.5 Hz, 1H), 4.31 (dd, J = 3.9, 2.1 Hz, 1H), 2.41 (s, 3H);13C NMR (101 MHz, CDCl3) δ 153.45, 151.97, 140.65, 132.00, 129.99, 127.56, 89.19, 81.57, 21.41; HRMS (ESI+; MeOH): m / z calcd. (C11H10NaO3) 213.0522 (M+Na)+: found: 213.0525; IR (ATR): ^^ [cm-1] = 2922, 1944, 1926, 1837, 1797, 1736, 1688, 1613, 1536, 1518, 1385, 1349, 1309, 1261, 1203, 1186, 1144, 1134, 1116, 1039, 1022, 954, 928, 901, 859, 846, 826, 778, 755, 744, 717, 645. Compound (II-7) Colorless oil, 376.6 mg (yield: 96%); Rf(EtOAc / hexane 1:2) = 0.8.1H NMR (400 MHz, CDCl3) δ 7.45 – 7.36 (m, 2H), 7.19 - 7.09 (m, 2H), 6.07 (t, J = 2.3 Hz, 1H), 5.01 (dd, J = 4.0, 2.5 Hz, 1H), 4.30 (dd, J = 4.0, 2.1 Hz, 1H);19F NMR (471 MHz, CDCl3) δ -109.93;13C NMR (101 MHz, CDCl3) δ 163.94 (d, J = 250.5 Hz), 153.08, 151.66, 130.83 (d, J = 3.3 Hz), 129.74 (d, J = 8.8 Hz), 116.53 (d, J = 22.1 Hz), 89.65, 80.81; HRMS (ESI+; MeOH): m / z calcd. (C10H7FNaO3) 217.2071 (M+Na)+: found: 217.2076; IR (re- flection): ^^ [cm-1] = 3647, 3129, 3080, 3024, 2448, 2400, 2267, 2174, 2030, 1933, 1816, 1684, 1606, 1509, 1425, 1384, 1305, 1261, 1223, 1199, 1161, 1128, 1101, 1028, 968, 930, 898, 829, 792, 763, 746, 641. Compound (II-8) White solid, 342.3 mg (yield: 83%); Rf(EtOAc / hexane 1:2) =0.31;1H NMR (400 MHz, CDCl3) δ 7.39 – 7.30 (m, 2H), 6.95 (d, J = 8.8 Hz, 2H), 6.04 (t, J = 2.3 Hz, 1H), 4.97 (dd, J = 3.9, 2.6 Hz, 1H), 4.27 (dd, J = 3.9, 2.1 Hz, 1H), 3.83 (s, 3H);13C NMR (101 MHz, CDCl3) δ 161.31, 153.53, 151.93, 129.46, 126.79, 114.70, 89.26, 81.62, 55.55; HRMS (ESI+; MeOH): m / z calcd. (C11H10NaO4) 229.0471 (M+Na)+: found: 229.0475; IR (ATR): ^^ [cm-1] = 3025, 2965, 2914, 2843, 1915, 1820, 1801, 1694, 1616, 1587, 1517, 1455, 1382, 1319, 1273, 1249, 1215, 1178, 1131, 1020, 954, 927, 901, 871, 848, 831, 771, 750, 715, 645. Compound (II-17) Colorless oil, 333.5 mg (yield: 70%); Rf(EtOAc / hexane 1:2) =0.47;1H NMR (500 MHz, CDCl3) δ 7.34 - 7.28 (m, 2H), 7.07 - 7.00 (m, 2H), 5.00 (q, J = 1.7 Hz, 2H), 4.96 (tt, J = 7.1, 2.1 Hz, 1H), 4.47 (s, 2H), 4.18 (dt, J = 7.1, 1.6 Hz, 2H);19F NMR (471 MHz, CDCl3) δ -114.48;13C NMR (101 MHz, CDCl3) δ 162.58 (d, J = 245.9 Hz), 152.33, 144.23, 133.69 (d, J = 3.2 Hz), 129.75 (d, J = 8.1 Hz), 115.46 (d, J = 21.6 Hz), 100.24, 72.12, 67.45, 63.45 HRMS (ESI+; MeOH): m / z calcd. (C12H11FNaO4) 261.0534, (M+Na)+: found: 261.0542; IR (reflec- tion): ^^ [cm-1] = 2924, 2868, 1835, 1724, 1603, 1510, 1467, 1378, 1297, 1269, 1221, 1157, 1100, 1085, 1044, 1015, 955, 824, 764, 733. Compound (II-18) Colorless oil, 288.2 mg (yield: 50%); Rf(EtOAc / hexane 1:2) =0.431H NMR (500 MHz, CDCl3) δ 7.61 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 8.0 Hz, 2H), 5.01 (q, J = 1.7 Hz, 2H), 4.98 (tt, J = 7.0, 2.0 Hz, 1H), 4.57 (s, 2H), 4.22 (dt, J = 7.1, 1.5 Hz, 2H);19F NMR (471 MHz, CDCl3) δ -62.50;13C NMR (101 MHz, CDCl3) δ 152.28, 144.47, 142.07 (d, J = 1.2 Hz), 130.09 (q, J = 32.3 Hz), 127.82, 127.69, 125.61, 125.52 (q, J = 3.9 Hz), 122.91, 120.20, 99.97, 71.91, 67.44, 63.80; HRMS (ESI+; MeOH): m / z calcd. (C13H11FNaO4) 311.0502, (M+Na)+: found: 311.0511; IR (reflection): ^^ [cm-1] = 2956, 2917, 2850, 1831, 1721, 1620, 1534, 1463, 1420, 1377, 1322, 1261, 1210, 1161, 1095, 1063, 1043, 1018, 958, 821, 0763, 731, 642. Compound (II-19) White solid, 160 mg (yield: 58%); Rf(EtOAc / hexane 1:2) =0.24;1H NMR (301 MHz, CDCl3) δ 7.50 (s, 4H), 6.11 (t, J = 2.3 Hz, 2H), 5.02 (dd, J = 4.1, 2.5 Hz, 2H), 4.34 (dd, J = 4.1, 2.1 Hz, 2H);13C NMR (76 MHz, CDCl3) δ 152.53, 151.60, 137.06, 128.21, 89.88, 80.50; HRMS (ESI+; MeOH): m / z calcd. (C14H10NaO6) 297.0370 (M+Na)+: found: 297.0371; IR (reflection): ^^ [cm-1] = 3129, 3020, 1939, 1818, 1687, 1530, 1439, 1350, 1304, 1264, 1210, 1137, 1035, 968, 943, 901, 867, 844, 829, 761, 743, 720, 644. The 4-methylene-1,3-dioxol-2-one compounds of formula (II), for instance those of for- mulae II-1, II-2, II-4, II-12, II-13, II-14, II-15, II-16 and II-21 can also be prepared using alter- native procedures known in the art, as described for example in S. Dabral et al., Org. Lett. 2019, 21, 1422-1425 or A. Cervantes-Reyes et al., Green Chem. 2021, 23, 889-897. 3.3 Preparation of endo-unsaturated 1,3-dioxol-2-one compounds of formula (I) 3.3.1 Examples 3.3.1-1 to 3.3.1-15 In the following series of reactions 3.3.1-1 to 3.3.1-15, the conversion of compound (II-13) to compound (I-13) was used to demonstrate the suitability of various solvents and ba- ses in the process of the invention. (II-13) (I-13) Reactions 3.3.1-1 to 3.3.1-15 were carried out according to the following general proce- dure: Compound II-13 (44 mg, 0.2 mmol), base (20 or 40 µL of a 0.1 mmol / mL solution, 1 or 2 mol%), additive (i.e. a phenolic compound) (20 or 40 µL of a 0.5 mmol / mL solution, 5 or 10 mol%), and solvent (1 mL) were added to a 10 mL oven-dried glassware vial un- der argon. The mixture was stirred at 30°C for 2 h. Afterwards the solvent was removed in vacuo and the resulting product was optionally purified by flash chromatography (sil- ica gel 70-230 mesh) employing 10-30% EtOAc in hexane as a gradient eluent. For each reaction, the solvent and base used as well as the amounts of base and additive em- ployed are listed in Table 1 below. The conversion rates and yields shown in Table 1 were determined from the crude product by1H NMR using CH2Br2as an internal standard, unless otherwise indicated. Table 1: Example Base (mol%) Additive Solvent Conversion Yield c)(mol%)c)3.3.1-1a)TBD (2) - DCM 0% 0% 3.3.1-2a)- phenol (10) DCM 0% 0% 3.3.1-3 TBD (2)phenol (10)DCM 100% 80% b)3.3.1-4 DBU (2) phenol (10) DCM 53% 22% 3.3.1-5 DBN (2) phenol (10) DCM 11% 0% 3.3.1-6 DABCO (2) phenol (10) DCM 0% 0% 3.3.1-7 DMAP (2) phenol (10) DCM 0% 0% 3.3.1-8 protone phenol (10) DCM 0% 0% sponge (2) 3.3.1-9 ET3N (2) phenol (10) DCM 0% 0% 3.3.1-10 Cs2CO3(2) phenol (10) DCM 73% 73% 3.3.1-11 NaOH (2) phenol (10) DCM 20% 0% 3.3.1-12 TBD (2) phenol (10) CH3CN 100% 65% 3.3.1-13 TBD (2) phenol (10) DMF 100% 49% 3.3.1-14 TBD (1) phenol (10) DCM 100% 59% 3.3.1-15 TBD (2) phenol (5) DCM 57% 10%a)not according to the invention;b)Yield of isolated product.c)based on compound (II-13) As can be seen from Table 1, best results were obtained with reaction 3.3.1-3 using DCM as solvent 2 mol% of TBD as base and 10 mol% of phenol. 3.3.2 Effect of additives In the following series of examples 3.3.2-1 to 3.3.2-15, the conversion of compound (II- 13) to compound (I-13) the effect of different additives, such as especially phenolic com- pounds, in the process of the invention was demonstrated. Reactions 3.3.2-1 to 3.3.2-15 were carried out according to the following general proce- dure: Compound II-13 (44 mg, 0.2 mmol), TBD (40 µL of a 0.1 mmol / mL solution, 2 mol%), additive (40 µL of a 0.5 mmol / mL solution, 10 mol%), and DCM (1 mL) were added to a 10 mL oven-dried glassware vial under argon. The mixture was stirred at 30°C for 2 h. Afterwards the solvent was removed in vacuo and the resulting product was optionally purified by flash chromatography (silica gel 70-230 mesh) employing 10- 30% EtOAc in hexane as a gradient eluent. For each reaction, the additive used and its pKa value are listed in Table 2 below. The conversion rates and yields shown in Table 2 were determined from the crude product by1H NMR using CH2Br2as an internal stand- ard, unless otherwise indicated. Table 2: Reaction pKa Additive Conversion Yield unknown by-product 3.3.2-1 18.0 phenol 100% 80%b)22% 3.3.2-2 14.9 4-hydroxyphenol 15% 0% 15% 3.3.2-3 18.9 4-methylphenol 100% 82%b)18% 3.3.2-4 15.5 4-bromophenol 11% 0% trace 3.3.2-5 16.7 4-chlorophenol 70% 43% 25% 3.3.2-6 18.0 4-fluorophenol 100% 82%b)17% 3.3.2-7 15.3 4-(trifluoromethyl)phenol 0% 0% 0% 3.3.2-8a)10.3 thiophenol 0% 0% 0% 3.3.2-9a)17.9 HFP 0% 0% 0% 3.3.2-10a)19.9 carbazole 48% 0% n.d. 3.3.2-11a)18.6 imidazole 38% 0% n.d. 3.3.2-12a)19.8 pyrazole 46% 0% n.d. 3.3.2-13a)16.4 benzimidazole 27% 0% n.d. 3.3.2-14a)16.2 1-naphthol 22% 0% n.d. 3.3.2-15a)17.2 2-naphthol 39% 0% n.d.a)not according to the invention;b)Yield of isolated product. As can be seen from Table 2 best results were obtained with phenol, 4-methylphenol and 4-fluorophenol as additive (see reactions 3.3.2-1, 3.3.2-3 and 3.3.2-6). 3.3.3 Effect of bases, additives and solvents in the preparation of a disubstituted com- pound (I) In the following series of reactions 3.3.3-1 to 3.3.3-37, the conversion of compound (II-5) to compound (I-5) was used to test different bases, solvents and additives, such as espe- cially phenolic compounds, regarding their suitability for the process of the invention. (II-5) (I-5) Reactions 3.3.3-1 to 3.3.3-37 were carried out according to the following general proce- dure: Compound II-5 (35.2 mg, 0.2 mmol), base (20 or 40 µL of a 0.1 mmol / mL solution, 1 or 2 mol%), additive (20 or 40 µL of a 0.5 mmol / mL solution, 5 or 10 mol%), and solvent (1 mL) were added to a 10 mL oven-dried glassware vial under argon. The mixture was stirred at 30°C for 2 h. Afterwards the solvent was removed in vacuo and the resulting product was optionally purified by flash chromatography (silica gel 70-230 mesh) em- ploying 10-30% EtOAc in hexane as a gradient eluent. For each reaction, the base, addi- tive and solvent used as well as the amounts of base and additive employed are listed in Table 3 below. The conversion rates and yields shown in Table 3 were determined from the crude product by1H NMR using CH2Br2as an internal standard, unless otherwise in- dicated. Table 3: Reaction Base (mol%) Additive (mol%)c)Solvent Con- Yield c)version.3.3-1a)TBD (2) - CH3CN 6% trace.3.3-2a)- phenol (10) CH3CN 0% 0% .3.3-3 TBD (2) phenol (10)CH3CN100% 96% (94%)b).3.3-4 MeTBD (2) phenol (10) CH3CN 100% 94% .3.3-5 DBU (2) phenol (10) CH3CN 100% 72% .3.3-6 DBN (2) phenol (10) CH3CN 100% 71% .3.3-7 DABCO (2) phenol (10) CH3CN 0% 0% .3.3-8 DMAP (2) phenol (10) CH3CN 0% 0% .3.3-9 protone phenol (10) CH3CN 0% 0% sponge (2) .3.3-10 Et3N (2) phenol (10) CH3CN 0% 0% .3.3-11 Cs2CO3(2) phenol (10) CH3CN 100% 77% .3.3-12 NaOH (2) phenol (10) CH3CN 0% 0% .3.3-13 TBD (2) phenol (10) 2-CH3-THF 54% 43% .3.3-14 TBD (2) phenol (10) DCM 31% 19% .3.3-15 TBD (2) phenol (10) DMF 36% 31% .3.3-16 TBD (2) phenol (10) diethyl ether 55% 35% .3.3-17 TBD (2) phenol (10) THF 77% 55% .3.3-18 TBD (1) phenol (10) CH3CN 48% 40% .3.3-19 TBD (2) phenol (5) CH3CN 13% 11% Reaction Base (mol%) Additive (mol%)c)Solvent Con- Yield c)version.3.3-20 TBD (2) 4-hydroxyphenol (10) CH3CN 60% 43%.3.3-21 TBD (2) 4-methoxyphenol (10) CH3CN 31% 20%.3.3-22 TBD (2) 4-methylphenol (10) CH3CN 29% 14% .3.3-23 TBD (2) 3-methylphenol (10) CH3CN 30% 15% .3.3-24 TBD (2) 2-methylphenol (10) CH3CN 31% 14% .3.3-25 TBD (2) 2,6-dimethylphenol CH3CN 26% 14% (10) .3.3-26 TBD (2) 4-bromophenol (10) CH3CN 24% 13% .3.3-27 TBD (2) 4-chlorophenol (10) CH3CN 30% 11% .3.3-28 TBD (2) 4-fluorophenol (10) CH3CN 100% 84%.3.3-29 TBD (2) 4-(trifluoromethyl)- CH3CN 0% 0% phenol (10) .3.3-30a)TBD (2) thiophenol CH3CN 0% 0% .3.3-31a)TBD (2) HFP CH3CN 0% 0% .3.3-32a)TBD (2) carbazole (10) CH3CN 37% 0% .3.3-33a)TBD (2) imidazole (10) CH3CN 24% 0% .3.3-34a)TBD (2) pyrazole (10) CH3CN 20% 0% .3.3-35a)TBD (2) benzimidazole (10) CH3CN 23% 0% .3.3-36a)TBD (2) 1-naphthol (10) CH3CN 22% 0% .3.3-37a)TBD (2) 2-naphthol (10) CH3CN 35% 0%a)Not according to the invention;b)Yield of isolated product;c) based on compound (II-5) As can be seen from Table 3 all tested combinations are suitable for achieve the conver- sion. Best results were obtained with TBD or MeTBD as base, phenol and fluorophenol as additive and acetonitrile as solvent (see reactions 3.3.3-3, 3.3.3-4 and 3.3.3-28). 3.3.4 Effect of reaction times and temperatures for preparation of disubstituted com- pounds (I) In the following series of reactions 3.3.4-1 to 3.3.4-7, the conversions of compounds (II- 2), (II-4) or (II-3) to compounds (I-2), (I-4) or (I-3) were used to investigate which reac- tion times and temperatures give the best results in the process of the invention. Reactions 3.3.4-1 to 3.3.4-7 were carried out according to the following general proce- dure: Compound II-2, II-4 or II-3 (0.2 mmol), TBD (40 µL of a 0.1 mmol / mL solution, 2 mol%), phenol (40 µL of a 0.5 mmol / mL solution, 10 mol%), and acetonitrile (1 mL) were added to a 10 mL oven-dried glassware vial under argon. The mixture was stirred at 30 to 80°C for 2 to 16 h as specified in Tables 4.1, 4,2 and 4.3 below. Afterwards the solvent was removed in vacuo and the resulting product was optionally purified by flash chro- matography (silica gel 70-230 mesh) employing 2-10% diethyl ether in hexane as a gra- dient eluent. The conversion rates and yields shown in Tables 4.1, 4.2 and 4.3 were de- termined from the crude product by1H NMR using CH2Br2as an internal standard, un- less otherwise indicated. (II-2) (I-2) Table 4.1: Conversion of compound (II-2) to compound (I-2) Reaction Reaction time Temperature Conversion Yield 3.3.4-1 2 h 30 °C 63% 60% 3.3.4-2 4 h 30 °C 100% 92% (66%)b)b)Yield of isolated product. Table 4.2: Conversion of compound (II-4) to compound (I-4) Reaction Reaction time Temperature Conv. Yield 3.3.4-3 2 h 30oC 28% 24% 3.3.4-4 16 h 80oC 100% 91% (61%)b)b)Yield of isolated product. (II-3) (I-3) Table 4.3: Conversion of compound (II-3) to compound (I-3) Reaction Reaction time Temperature Conversion Yield 3.3.4-5 2 h 60oC 18% 11% 3.3.4-6 16 h 60oC 60% 50% 3.3.4-7 16 h 80oC 100% 58% (23%)b)As can be seen from Tables 4.1 to 4.3, the conversions of the 4-methylene-5-alkyl-1,3- dioxol-2-one compounds of formulae (II-2) to (II-4), especially compounds (II-3) and (II- 4), require much longer reaction times and higher reaction temperatures for complete conversion than other 4-methylene-1,3-dioxol-2-one compounds of formula (II). 3.3.5 Preparation of the endo-saturated 1,3-dioxol-2-one compounds of formulae I-1 to I-8, I-12 to I-19 and I-21 The preparations of the compounds I-1 to I-8, I-12 to I-19 and I-21 (see Schemes A, B, C, E and F above) were carried out according to the following general procedure: A com- pound II-1 to II-8, II-12 to II-19 or II-21 (0.2 mmol, see Schemes A, B, C, E and F above), TBD (40 µL of a 0.1 mmol / mL solution, 2 mol%), phenol (40 µL of a 0.5 mmol / mL solu- tion, 10 mol%), and solvent (1 mL) were added to a 10 mL oven-dried glassware vial un- der argon. The mixture was stirred at 30 or 80°C for 2, 4 or 16 h as specified in Table 5 below. Afterwards the solvent was removed in vacuo and the resulting product was pu- rified by flash chromatography (silica gel 70-230 mesh) employing 10-50% EtOAc in hexane as a gradient eluent. The yields given in Table 5 refer to the isolated product. Also given in Table 5 for same cases are the yields that were determined from the crude product by1H NMR using CH2Br2as an internal standard. Table 5: Reaction Solvent Reaction time Temperature Yielda)Yieldb)I-1c)DCM 2 h 30 °C 67% 20% I-2 CH3CN 4 h 30 °C 92% 66% I-3 CH3CN 16 h 80 °C 58% 23% I-4 CH3CN 16 h 80 °C 91% 61% I-5 CH3CN 2 h 30 °C - 94% I-6 CH3CN 2 h 30 °C - 98% I-7 CH3CN 2 h 30 °C - 96% I-8 CH3CN 2 h 30 °C - 99% I-12 DCM 2 h 30 °C - 69% I-13 DCM 2 h 30 °C - 80% (72%)d)I-14 DCM 2 h 30 °C - 66% I-15 DCM 2 h 30 °C - 62% I-16 DCM 2 h 30 °C - 65% I-17 DCM 2 h 30 °C - 78% I-18 DCM 2 h 30 °C - 47% I-19 CH3CN 2 h 30 °C - 91% I-21 DCM 2 h 30 °C - 61%a)Yield by1H NMR using CH2Br2as an internal standard;b)Yield of isolated product;c)Reaction conducted on a 10 mmol scale with purification by vacuum distillation;d)Yield of isolated product for reaction on a 10 mmol scale. Analytical data of the prepared compounds I-1 to I-9, I-13 to I-19 and I-21: Compound I-1: Preparation was conducted on a 10 mmol scale and crude product was purified by vac- uum distillation (0.45 mbar 36-38oC), 200 mg (yield: 20%);1H NMR (300 MHz, CDCl3) δ 6.78 (q, J = 1.8 Hz, 1H), 2.10 (d, J = 1.6 Hz, 3H);13C NMR (75 MHz, CDCl3) δ 153.56, 141.26, 126.12, 10.00. Compound I-2: Preparation was conducted on a 0.5 mmol scale and crude product was purified by crys- tallization, white solid, 38 mg (yield: 66%);1H NMR (300 MHz, CDCl3) δ 2.02 (s, 6H);13C NMR (75 MHz, CDCl3) δ 153.30, 134.85, 9.10. Compound I-3: Flash chromatography was done with 5% diethyl ether in hexane as gradient eluent. Colorless oil; Rf(EtOAc / hexane 1:5) = 0.50;1H NMR (301 MHz, CDCl3) δ 2.75 (p, J = 7.0 Hz, 1H), 2.07 (s, 3H), 1.22 (d, J = 6.9 Hz, 6H);13C NMR (76 MHz, CDCl3) δ 153.42, 142.81, 133.11, 24.60, 20.24, 9.37; HRMS (EI+; MeOH): m / z calcd. (C7H11O3) 142.06245 (M)+: found: 142.06717; IR (reflection): ^^ [cm-1] = 2925, 2855, 1816, 1729, 1504, 1463, 1390, 1272, 1076. Compound I-4: Flash chromatography was done with 5% diethyl ether in hexane as gradient eluent. Colorless oil; Rf(EtOAc / hexane 1:5) = 0.50;1H NMR (301 MHz, CDCl3) δ 2.32 (td, J = 7.2, 1.0 Hz, 2H), 2.04 (t, J = 0.9 Hz, 3H), 1.60 (h, J = 7.3 Hz, 2H), 0.94 (t, J = 7.4 Hz, 3H);13C NMR (76 MHz, CDCl3) δ 153.45, 138.39, 134.94, 25.50, 20.22, 13.45, 9.16; HRMS (EI+; MeOH): m / z calcd. (C7H11O3) 142.06245 (M)+: found: 142.05514; IR (reflection): ^^ [cm-1] = 2965, 2935, 2877, 2052, 1815, 1738, 1546, 1504, 1460, 1433, 1393, 1288, 1254, 1211, 1187, 1088, 1027, 968, 940, 772, 624. Compound I-5: White solid, 33.1 mg (yield: 94%); Rf(EtOAc / hexane 1:2) = 0.37;1H NMR (301 MHz, CDCl3) δ 7.42 - 7.22 (m, 5H), 2.27 (s, 3H);13C NMR (76 MHz, CDCl3) δ 152.32, 137.54, 135.21, 129.14, 129.10, 125.71, 125.21, 10.86. Compound I-6: White solid, 37.2 mg (yield: 98%); Rf(EtOAc / hexane 1:2) = 0.73;1H NMR (400 MHz, CDCl3) δ 7.38 - 7.29 (m, 2H), 7.30 - 7.21 (m, 2H), 2.39 (s, 3H), 2.35 (s, 3H);13C NMR (101 MHz, CDCl3) δ 152.45, 139.35, 137.73, 134.56, 129.79, 125.23, 122.90, 21.47, 10.81; HRMS (ESI+; MeOH): m / z calcd. (C11H13NaO3) 213.0522 (M+Na)+: found: 213.0528; IR (reflection): ^^ [cm-1] = 2949, 2923, 1809, 1738, 1517, 1435, 1365, 1290, 1246, 1190, 1127, 1064, 1040, 983, 934, 842, 821, 768, 711, 647, 632, 612. Compound I-7: White solid, 37.0 mg (yield: 96%); Rf(EtOAc / hexane 1:2) = 0.71;1H NMR (500 MHz, CDCl3) δ 7.49 - 7.42 (m, 2H), 7.15 (t, J = 8.6 Hz, 2H), 2.36 (s, 3H);19F NMR (471 MHz, CDCl3) δ -110.67;13C NMR (126 MHz, CDCl3) δ 162.94 (d, J = 250.3 Hz), 152.17, 136.86, 134.93, 127.33 (d, J = 8.6 Hz), 121.94 (d, J = 3.4 Hz), 116.42 (d, J = 22.0 Hz), 10.81; HRMS (ESI+; MeOH): m / z calcd. (C10H7FNaO4) 217.0271 (M+Na)+: found: 217.0276; IR (reflection): ^^ [cm-1] = 3076, 1957, 1903, 1858, 1801, 1713, 1603, 1510, 1442, 1413, 1395, 1336, 1305, 1291, 1248, 1229, 1194, 1166, 1103, 1058, 1010, 980, 930, 835, 765, 715, 653, 634, 609. Compound I-8: White solid, 41.0 mg (yield: 99%); Rf(EtOAc / hexane 1:2) = 0.59;1H NMR (400 MHz, CDCl3) δ 7.39 (d, J = 8.9 Hz, 2H), 6.96 (d, J = 9.0 Hz, 2H), 3.84 (s, 3H), 2.33 (s, 3H);13C NMR (101 MHz, CDCl3) δ 160.27, 152.53, 137.60, 133.80, 126.95, 118.22, 114.64, 55.54, 10.72; HRMS (ESI+; MeOH): m / z calcd. (C11H13NaO4) 229.0471 (M+Na)+: found: 229.0476; IR (reflection): ^^ [cm-1] = 3071, 3013, 2969, 2943, 2913, 2843, 1798, 1707, 1609, 1574, 1518, 1447, 1418, 1393, 1342, 1313,1299, 1258, 1197, 1179, 1121, 1067, 1034, 1017, 1002, 986, 933, 843, 817, 767, 648, 636, 611. Compound I-12: Colorless oil, 35.7 mg (yield: 69%); Rf(EtOAc / hexane 1:2) = 0.58;1H NMR (400 MHz, CDCl3) δ 6.91 (t, J = 1.5 Hz, 1H), 3.66 (dt, J = 11.0, 6.1 Hz, 4H), 2.67 (td, J = 6.0, 1.6 Hz, 2H), 2.46 (t, J = 6.1 Hz, 2H), 1.44 (s, 9H);13C NMR (101 MHz, CDCl3) δ 170.93, 153.44, 142.61, 127.31, 80.94, 66.72, 66.47, 36.19, 28.23, 25.48; HRMS (ESI+; MeOH): m / z calcd. (C12H18NaO6) 281.0996 (M+Na)+: found: 281.1000; IR (reflection): ^^[cm-1] = 3162, 2978, 2931, 2875, 2059, 1976, 1836, 187, 1726, 1481, 1383, 1368, 1321, 1257, 1223, 1160, 1120, 1069, 942, 846, 754, 655. Compound I-13: Colorless oil, 35.2 mg (yield: 80%); Rf(EtOAc / hexane 1:2) = 0.55;1H NMR (301 MHz, CDCl3) δ 7.42 - 7.28 (m, 5H), 6.85 (t, J = 1.5 Hz, 1H), 4.53 (s, 2H), 3.67 (t, J = 6.1 Hz, 2H), 2.72 (td, J = 6.1, 1.5 Hz, 2H);13C NMR (76 MHz, CDCl3) δ 153.37, 142.53, 137.66, 128.65, 128.08, 127.85, 127.10, 73.32, 65.61, 25.60; HRMS (EI+; MeOH): m / z calcd. (C12H12O4) 220.0730 (M)+: found: 220.0718; IR (reflection): ^^ [cm-1] = 3164, 3064, 3031, 2868, 2188, 2060, 1978, 1833, 1802, 1693, 1602, 1496, 1454, 1421, 1365, 1319, 1265, 1222, 1186, 1118, 1070, 1028, 943, 914, 736, 697. Compound I-14: Colorless oil, 31.0 mg (yield: 66%); Rf(EtOAc / hexane 1:2) = 0.7;1H NMR (400 MHz, CDCl3) δ 7.24 - 7.12 (m, 4H), 6.83 (t, J = 1.5 Hz, 1H), 4.48 (s, 2H), 3.65 (t, J = 6.1 Hz, 2H), 2.70 (td, J = 6.1, 1.5 Hz, 2H), 2.35 (s, 3H);13C NMR (101 MHz, CDCl3) δ 153.38, 142.60, 137.89, 134.62, 129.35, 128.03, 127.09, 73.24, 65.43, 25.65, 21.29; HRMS (ESI+; MeOH): m / z calcd. (C13H14NaO4) 257.0784 (M+Na)+: found: 257.0786; IR (reflection): ^^ [cm-1] = 3162, 2922, 2864, 1978, 1834, 1805, 1692, 1617, 1516, 1458, 1363, 1319, 1260, 1222, 1184, 1119, 1071, 941, 913, 803, 748, 655. Compound I-15: Colorless oil, 30.6 mg (yield: 62%); Rf(EtOAc / hexane 1:2) = 0.72;1H NMR (400 MHz, CDCl3) δ 6.95 (s, 1H), 6.93 - 6.90 (m, 2H), 6.85 (t, J = 1.5 Hz, 1H), 4.45 (s, 2H), 3.66 (t, J = 6.1 Hz, 2H), 2.71 (td, J = 6.1, 1.5 Hz, 2H), 2.32 (s, 6H);13C NMR (101 MHz, CDCl3) δ 153.39, 142.60, 138.26, 137.52, 129.72, 127.10, 125.78, 73.44, 65.60, 25.64, 21.37; HRMS (ESI+; MeOH): m / z calcd. (C14H16NaO4) 271.0941 (M+Na)+: found: 271.0942; IR (reflection): ^^ [cm-1] = 3161, 3013, 2920, 2663, 1833, 1804, 1692, 1460, 1359, 1319, 1260, 1222, 1185, 1159, 1117, 1070, 943, 912, 841, 743, 655. Compound I-16: White solid, 38.8 mg (yield: 68%); Rf(EtOAc / hexane 1:2) = 0.57;1H NMR (400 MHz, CDCl3) δ 7.63 - 7.56 (m, 4H), 7.48 - 7.41 (m, 2H), 7.41 - 7.33 (m, 3H), 6.87 (t, J = 1.5 Hz, 1H), 4.57 (s, 2H), 3.71 (t, J = 6.1 Hz, 2H), 2.74 (td, J = 6.1, 1.5 Hz, 2H);13C NMR (101 MHz, CDCl3) δ 153.38, 142.56, 141.14, 140.90, 136.69, 128.94, 128.35, 127.54, 127.46, 127.26, 127.13, 73.13, 65.75, 25.69; HRMS (ESI+; MeOH): m / z calcd. (C18H16NaO4) 319.0941 (M+Na)+: found: 319.0942; IR (reflection): ^^ [cm-1] = 3149, 3029, 2887, 1835, 1802, 1737, 1691, 1488, 1405, 1375, 1335, 1312, 1295, 1216, 1184, 1141, 1114, 1058, 1008, 964, 928, 843, 822, 204, 764, 749, 701. Compound I-17: Colorless oil, 36.9 mg (yield: 78%); Rf(EtOAc / hexane 1:2) = 0.51;1H NMR (500 MHz, CDCl3) δ 7.27 (dd, J = 8.5, 5.5 Hz, 2H), 7.04 (t, J = 8.7 Hz, 2H), 6.85 (t, J = 1.4 Hz, 1H), 4.48 (s, 2H), 3.66 (t, J = 6.1 Hz, 2H), 2.71 (td, J = 6.0, 1.3 Hz, 2H);19F NMR (471 MHz, CDCl3) δ -114.30;13C NMR (151 MHz, CDCl3) δ 162.56 (d, J = 246.2 Hz), 153.35, 142.44, 133.44 (d, J = 2.8 Hz), 129.60 (d, J = 8.2 Hz), 127.09, 115.52 (d, J = 21.5 Hz), 72.59, 65.65, 25.56; HRMS (ESI+; MeOH): m / z calcd. (C12H11FNaO4) 261.0534 (M+Na)+: found: 261.0534; IR (reflec- tion): ^^ [cm-1] = 3165, 2957, 2922, 2851, 1835, 1804, 1692, 1603, 1509, 1462, 1362, 1319, 1260, 1221, 1185, 1156, 1119, 1093, 1070, 820, 741. Compound I-18: Colorless oil, 27.1 mg (yield: 47%); Rf(EtOAc / hexane 1:2) = 0.49;1H NMR (500 MHz, CDCl3) δ 7.61 (d, J = 8.1 Hz, 2H), 7.42 (d, J = 8.0 Hz, 2H), 6.87 (t, J = 1.5 Hz, 1H), 4.58 (s, 2H), 3.70 (t, J = 6.1 Hz, 2H), 2.75 (td, J = 6.1, 1.4 Hz, 2H);19F NMR (471 MHz, CDCl3) δ -62.54;13C NMR (126 MHz, CDCl3) δ 153.33, 142.31, 141.78, 130.20 (q, J = 32.4 Hz), 127.69, 127.44, 127.15, 125.61 (q, J = 4.0 Hz), 125.28, 123.12, 121.04, 72.50, 66.13, 25.60; HRMS (ESI+; MeOH): m / z calcd. (C13H11F3NaO4) 311.0502 (M+Na)+: found: 311.0503; IR (reflection): ^^ [cm-1] = 3167, 2918, 2872, 1833, 1803, 1692, 1620, 1482, 1420, 1368, 1321, 1223, 1160, 1100, 1063, 1017, 913, 821, 736, 639. Compound I-19: White solid, 50.0 mg (yield: 91%); Rf(EtOAc / hexane 1:2) = 0.24;1H NMR (600 MHz, CD2Cl2) δ 7.56 (s, 4H), 2.40 (s, 6H);13C NMR (151 MHz, CD2Cl2) δ 152.19, 136.97, 136.72, 126.38, 125.79, 11.16; HRMS (EI+; MeOH): m / z calcd. (C14H10O6) 274.0416 (M)+: found: 274.0472; IR (reflection): ^^ [cm-1] = 2924, 2852, 1820, 1710, 1605, 1491, 1416, 1357, 1245, 1195, 1159, 1041, 1004, 902, 845, 766, 731, 693. Compound I-21: White solid, 22.1 mg (yield: 61%); Rf(EtOAc / hexane 2:1) = 0.52;1H NMR (301 MHz, CDCl3) δ 7.29 (s, 4H), 6.85 (t, J = 1.5 Hz, 2H), 4.52 (s, 4H), 3.67 (t, J = 6.1 Hz, 4H), 2.71 (td, J = 6.1, 1.5 Hz, 4H);13C NMR (76 MHz, CDCl3) δ 153.38, 142.49, 137.47, 128.04, 127.13, 72.99, 65.62, 25.63; HRMS (ESI+; MeOH): m / z calcd. (C11H13NaO3) 213.0522 (M+Na)+: found: 213.0528; IR (reflection): ^^ [cm-1] = 3159, 2924, 2866, 1844, 1802, 1737, 1694, 1519, 1485, 1462, 1443, 1407, 1368, 1331, 1294, 1215, 1184, 1126, 1107, 1080, 1055, 1018, 1007, 965, 926, 803, 775, 746, 711. 3.3.6 Comparative examples A preferred catalytic system according to the present invention, namely 2 mol% TBD and 10 mol% phenol, was compared with catalytic systems known from the prior art and not in accordance with the invention, respectively, using the following isomerization re- actions of compounds (II) to the corresponding endo-unsaturated derivatives (I). Reaction A: (II-2) (I-2) Reaction B: (II-5) (I-5) Reaction C: (II-13) (I-13) The reactions were carried out according to the following general procedure: Com- pound II-2, II-5 or II-13 (0.2 mmol), the catalytic system and solvent (1 mL) were added to a 10 mL oven-dried glassware vial under argon. The components of the catalytic sys- tem used as well as their amounts are listed in Table 6 below. The components were added to the vial in form of solutions or dispersions in the solvent used for the respec- tive reaction. The reactions A, B and C were carried out in acetonitrile, toluene and di- chloromethane, respectively, unless indicated otherwise. The reaction mixtures were stirred at 30°C for 2 h. Afterwards the solvent was removed in vacuo and the conversion rates and yields given in Table 6 were determined from the obtained crude product by 1H NMR using CH2Br2as an internal standard. Table 6: Reaction A Reaction B Reaction C Catalytic System Conversion Yield Conversion Yield Conversion Yield AgOAc (10 mol%) )an.d. 0% 100% 70% 100% 0% + DBU (40 mol%)AgOAc (10 mol%)a)0% 0% 12% 0% 22% 0% DBU (40 mol%)a)48% 32% 100% 63% 100% 0% DBU (2 mol%)a)0% 0 100% 57% 54% 0% TBD (2 mol%)a)0% 0% 100% 61% 7% / 12% 0% TBD (2 mol%)a)0% 0% 6%c)trace n.d. n.d. TBD (2 mol%) b)100% 92% 100% 96% 100% 80% + PhOH (10 mol%) a)Not according to the invention; b)According to the invention; c)Reaction was conducted in acetonitrile as solvent. As can be seen from Table 6, by far the best results were achieved with the catalytic sys- tem according to the invention, i.e. the combination of TBD (2 mol%) and phenol (10 mol%). 4. Calculation of the pKa values of substituted phenols of formula (III): The pKa values listed in Table 7 below were calculated via the DFT modeling method described herein above using the pKa value measured for phenol as reference value. Ta- ble 7 further lists the values determined experimentally using solutions of the phenolic compounds in dimethyl sulfoxide at 25°C and 1 bar. These values were taken from the literature, as described above. Table 7: pKa value phenolic compound calculated measured reference: phenol 18.0 4-hydroxyphenol 14.9 - 4-methylphenol 19.0 18.9 3-methylphenol 17.5 - 2-methylphenol 18.1 - 2,6-dimethylphenol 19.0 - 4-methoxyphenol 19.8 19.1 4-bromophenol 15.5 - 4-chlorophenol 15.9 16.7 4-fluorophenol 17.6 18.0 4-(trifluoromethyl)phenol 12.8 15.3 5. Ring opening polymerization of the endo-unsaturated 1,3-dioxol-2-one compound of formula (I) and a corresponding exo compound of the formula (II) respectively The following polymerization experiments where carried out using the compound I-21 and its exo-isomer, i. e. the compound I-22. 5.1 Ring-Opening Copolymerization (ROCOP) with secondary diamine In a first series, the compounds I-21 and II-21 are reacted with secondary diamine sepa- rately, in order to compare the reactivity difference between these newly obtained mon- omers and the corresponding bis-exo vinylene carbonate monomers. Conditions: exo-monomer (II-21) or endo-monomer (I-21) (25 mg, 69 μmol), N,N’-dime- thyl-1,2-diaminoethane (6.1 mg, 69 μmol) and DBU (if needed, 42 µL of a 7.6 mg / mL in stock solution in CH3CN, 3 mol%) and 2 mL of CH3CN. Conversion was determined by1H NMR. Mnand polydispersity (Ð) values were obtained through GPC analysis in THF using polystyrene (PS) standards. The reaction is summarized in the following scheme. The structure of the resulting polymer was confirmed by spectroscopy (1H and 13C NMR). Table 8 summarizes further reaction conditions and results. Table 8: ROCOP with secondary diamine Monomer T / °C Catalyst Time / h Mn(g / mol) Mw(g / mol) Conv.2Ð II-21 rt1- 24 3903 5384 Full 1.38 I-21 60 - 24 582 587 16% 1.01 I-21 60 - 48 1539 1564 83% 1.02 I-21 rt DBU 3 mol% 24 1837 1992 21% 1.08 I-21 rt DBU 3 mol% 48 2209 2230 64% 1.01 2) Conv.: Conversion based on I-21 / II-21 The exo-monomer II-21 shows higher reactivity compared to the endo-monomer I-21. However, the endo-monomer I-21 is still sufficient reactive to undergo polymerization at higher temperatures or by using a catalyst. This is rather surprising, because the endo double bond is expected to have no reactivity towards nucleophilic attack for steric and electronic reasons. 5.2 Ring-Opening Copolymerization (ROCOP) with diol Conditions: endo-monomer I-21 (25 mg, 69 μmol), 1,4-butandiol (6.2 mg, 69 μmol) and DBU (42 µL of a 7.6 mg / mL in stock solution in CH3CN, 3 mol%) and 2 mL of CH3CN. Conversion was determined by1H NMR. Mnand Ð values were obtained through GPC analysis in THF using polystyrene (PS) standards. The reaction is summarized in the fol- lowing scheme. The structure of the resulting polymer was confirmed by spectroscopy (1H and 13C NMR). Table 9 summarizes further reaction conditions and results. 1) Conv.: Conversion based on I-21 / II-21 5.3 Ring-Opening Copolymerization (ROCOP) with primary diamine Conditions: endo-monomer 9b (25 mg, 69 μmol), 1,4-diaminobutane (6.1 mg, 69 μmol) and 2 mL of CH3CN. Conversion was determined by1H NMR. Mnand Ð values were ob- tained through GPC analysis in THF using polystyrene (PS) standards. The reaction is summarized in the following scheme. The structure of the resulting polymer was con- firmed by spectroscopy (1H and 13C NMR). Table 10 summarizes further reaction condi- tions and results. Table 10: ROCOP with diaminobutane Monomer T / °C Time / h Mn(g / mol) Mw(g / mol) Conv.1Ð I-21 rt 24 2193 2412 Full 1.10

Claims

Claims 1. The process for preparing an endo-unsaturated 1,3-dioxol-2-one (1), bearing an optionally substituted methyl group in the 4-position which comprises the isomer- ization of a 4-methylene-1,3-dioxol-2-one (2) in the presence of a catalyst which is a combination of a base and phenolic compound (3).

2. The process of claim 1, where the phenolic compound (3) is of the formula (III),where m is 0, 1, 2 or 3, in particular 0 or 1; n is 0, 1, 2, 3, 4 or 5, in particular 0 or 1; m+n is 0, 1, 2, 3, 4 or 5, in particular 0 or 1; R is selected from the group consisting of halogen, CN, NO2, C1-C10alkyl, C1- C10fluoroalkyl, C1-C10alkoxy, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl, C3-C14hetaryl, C3-C10cycloalkyloxy, C6-C14aryloxy, C3-C10heterocyclyloxy and C3-C14hetaryloxy, where C1-C10alkyl, C1-C10fluoroalkyl, C1-C10alkoxy are unsubstituted or sub- stituted by one or more radicals Raand where C3-C10cycloalkyl, C3-C10heter- ocyclyl, C6-C14aryl, C3-C14hetaryloxy, C3-C10cycloalkyloxy, C3-C10heterocy- clyloxy, C6-C14aryloxy and C3-C14hetaryloxy are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc, where Rais selected from Cl, Br, CN, and where one of Ramay be C1-C4-alkoxy, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3-C14hetaryloxy,where the 8 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc; and Rcycis selected from the group consisting of F, Cl, Br, CN, NO2, C1-C4-alkyl and C1-C4-alkoxy.

3. The process of any one of the preceding claims, where the phenolic compound (3) has a pKa of at least 16.5, in particular in the range of 16.5 to 20, where the pKa is determined as a solution of the phenolic compound in dimethylsulfoxide at 25°C and 1 bar.

4. The process of any one of the preceding claims, where the phenolic compound (3) is selected from phenol, 4-methylphenol, 4-methoxyphenol, 4-fluorophenol and 4-chlorophenol and combinations of phenolic compounds (3) comprising at least one of phenol, 4-methylphenol, 4-methoxyphenol, 4-fluorophenol and 4-chloro- phenol.

5. The process of any one of the preceding claims, where the base is selected from the group consisting of amines and alkalimetal carbonates.

6. The process of claim 5, where the base is an amine base of the group of amidine bases and guanidine bases.

7. The process of claim 5, where the base is selected from the group consisting of amidine bases, guanidine bases and alkalimetal carbonates.

8. The process of any one of the preceding claims, where the amount of the phenolic compound (3) is in the range of 0.001 to 0.5 mol per 1 mol of the compound (2).

9. The process of any one of the preceding claims, where the amount of the base is in the range of 0.00001 to 0.5 mol per 1 mol of the compound (2).

10. The process of any one of the preceding claims, where the molar ratio of the phe- nolic compound (3) to the base is in the range of 50:1 to 1:

10.

11. The process of any one of the preceding claims, where the isomerization is carried out in an aprotic organic solvent or without solvent.

12. The process of any one of the preceding claims, where the compound (1) is of the formula (I) and the compound (2) is of the formula (II)where R1, R2are identical or different and selected from the group consisting of hy- drogen, an organic radical having 1 to 40 carbon atoms and up to 8 heteroatoms selected from O, S, Si and N, where one of the radicals R1, R2may also be a radical of the formula (IV): Link-(R4)k(IV) where Link is a bi- or trivalent organic radical having 1 to 40 carbon atoms and up to 12 heteroatoms selected from O, S, Si and N, where the organic radical does not contain OH, NH2, COOH or SO3H, k is 1 or 2 and in case of the compound of the formula (I) R4in formula (IV) is a radical of the formulae (R4a) or (R4b) andand in case of the compound of the formula (II) R4in formula (IV) is a radical of the formulae (R4c) or (R4d)(R4c) (R4d) where # indicates the point of attachment of the radicals (R4a), (R4b), (R4c) and (R4d) to Link; R1aand R2aare identical or different and selected from the group con- sisting of hydrogen, an organic radical having 1 to 40 carbon at- oms and up to 6 heteroatoms selected from O, S, Si and N and which are not a radical of the formula (IV).

13. The process of claim 12, where in the formulae (I) and (II) R1is selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl, C3-C14hetaryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra1and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; R2is selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl and C3-C14he- taryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra2and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2; where Ra1, Ra2independently of each other are selected from Cl and Br and where one of Ra1, Ra2may be CN, O-Ra3, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)- OR12, O-C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1- C4-alkyl)3, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy,C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; Ra3is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1- C4-alkyl)3, A-Ra4, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl or C3-C14hetaryl, where the 8 last mentioned radicals are unsubstituted or substi- tuted by 1, 2, 3 or 4 radicals Rcyc3; Ra4is selected from H, CN, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)-OR12, O- C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C1-C6-alkyloxy, C1-C6-fluoroalkoxy, C3-C10cycloalkyl, C3- C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; A is C1-C10alkandiyl, where one of the CH2groups of C1-C10alkandiyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C10alkandiyl may be replaced by O and where C3-C10cycloalkylene and C6-C14arylene are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc4; Rcyc1, Rcyc2, Rcyc3, Rcyc4independently of each other are selected from selected from the group consisting of F, Cl, Br, CN, NO2, C1-C10-alkyl, C1-C10-fluoro- alkyl, C1-C10-alkyloxy, C1-C10-fluoroalkoxy, C(O)-R11, O-C(O)-R11, C(O)-OR12, O-C(O)-OR12, C(O)-NHR13and O-C(O)-NHR13and C6-C14aryl; R11is selected from hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl; R12, R13independently of each other are selected from C1-C10alkyl, C1-C10fluoro- alkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl; or where one of the radicals R1, R2may also be a radical of the formula (IV), Link-(R4)k(IV) wherein k is 1 or 2 R4is a radical of the formulae (R4a), (R4b), (R4c) or (R4d) defined in claim 11 and Link is a bivalent or trivalent radical selected from C1-C10alkandiyl, C1-C10alkant- riyl, bi- or trivalent C6-C14arylene and bi- or trivalent C3-C10cycloalkylene,where one of the CH2groups of C1-C10alkandiyl and C1-C10alkantriyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C10alkandiyl and C1-C10al- kantriyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where C6-C14arylene and C3-C10cycloalkylene are un- substituted or carry 1, 2 or 3 radicals Rcyc4; R1ais selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl, C3-C14hetaryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra1and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; R2ais selected from the group consisting of hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl and C3-C14he- taryl, where C1-C10alkyl is unsubstituted or substituted by one or more radicals Ra2and where C3-C10cycloalkyl, C3-C10heterocyclyl, C6-C14aryl and C3-C14hetaryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2.

14. The process of claim 13, where in the formulae (I) and (II) R1is CH2-O-Ra33or CH2-O-Link’-(R4)kR2is hydrogen; k is 1 or 2; Link’ is C1-C10alkandiyl or C1-C10alkantriyl, where one of the CH2groups of C1- C10alkandiyl and C1-C10alkantriyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene; and where 1, 2 or 3 of the CH2groups of C1-C8alkandiyl and C1-C10alkant- riyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where C6-C14arylene and C3-C10cycloalkylene are un- substituted or carry 1, 2 or 3 radicals Rcyc4; Ra33is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1- C4-alkyl)3, A-Ra4, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl or C3-C14hetaryl, where the 4 last mentioned radicals are unsubstituted or substi- tuted by 1, 2, 3 or 4 radicals Rcyc3; and Ra4is selected from H, CN, C1-C6-alkyloxy, C1-C6-fluoroalkoxy, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)-OR12, O-C(O)-OR12, C(O)-NHR13,O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocyclyloxy, C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last men- tioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; A is C1-C9alkandiyl, where one of the CH2groups of C1-C9alkandiyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C9alkandiyl may be replaced by O and where C3-C10cycloalkylene and C6-C14arylene are unsubstituted or substi- tuted by 1, 2, 3 or 4 radicals Rcyc4; R4is a radical of the formulae (R4a), (R4b), (R4c) or (R4d) defined in claim 11.

15. The process of claim 13 or claim 14, where in the formulae (I) and (II) R1is selected from the group consisting of hydrogen, C1-C10alkyl, CH2-O-Ra3, CH2-O-ARa4, C3-C10cycloalkyl and C6-C14aryl, where C1-C10alkyl is unsubstituted or substituted by one radical Ra11and where C3-C10cycloalkyl and C6-C14aryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; R2is selected from the group consisting of hydrogen, C1-C10alkyl, C3-C10cy- cloalkyl and C6-C14aryl, where C1-C10alkyl is unsubstituted or substituted by one radical Ra22and where C3-C10cycloalkyl and C6-C14aryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2; where A is C1-C8alkandiyl; Ra11, Ra22independently of each other are selected from C1-C4-alkoxy, C3-C10cycloalkyl, C3-C10cycloalkoxy, phenyl, phenoxy, where phe- nyl and phenoxy are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; Rcyc1, Rcyc2, Rcyc3, Rcyc4independently of each other are selected from the group consisting of F, Cl, Br, CN, C1-C6-alkyl, C1-C6-fluoroalkyl, C1-C6-al- kyloxy, C1-C6-fluoroalkoxy and phenyl; Ra3is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3-C10cycloalkyl and phenyl andphenoxy, where C3-C10cycloalkyl and phenyl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; Ra4is selected from H, C1-C6-alkyloxy, C1-C6-fluoroalkoxy, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)-OR12, O-C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3- C10cycloalkyl, C3-C10cycloalkoxy, phenyl and phenoxy, where the 4 last mentioned radicals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3; R11is selected from hydrogen, C1-C6alkyl, C1-C6fluoroalkyl, C2-C6alkenyl, C5-C6cycloalkyl and phenyl; R12, R13independently of each other are selected from C1-C6alkyl, C2-C6alkenyl, C1-C6fluoroalkyl, C5-C6cycloalkyl and phenyl; or where one of the radicals R1, R2may also be a radical of the formula (IV’), CH2-O-A’-R4(IV’) wherein R4is a radical of the formulae (R4a), (R4b), (R4c) or (R4d) defined in claim 11 and A’ is a bivalent radical selected from C1-C10alkandiyl, phenylene and C5-C6cycloalkylene, where one of the CH2groups of C1-C10alkandiyl may be replaced by one of phenylene and C5-C6cycloalkylene; and where 1, 2 or 3 of the CH2groups of C1-C10alkandiyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH-C(O)-NH, and where phenylene and C5-C6cycloalkylene are unsub- stituted or substituted by 1, 2 or 3 radicals Rcyc4; R1ais selected from the group consisting of hydrogen, C1-C10alkyl, CH2-O-A-Ra33, C3-C10cycloalkyl and C6-C14aryl, where C1-C10alkyl is unsubstituted or substituted by one radical Ra11and where C3-C10cycloalkyl and C6-C14aryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc1; R2ais selected from the group consisting of hydrogen, C1-C10alkyl, C3-C10cy- cloalkyl and C6-C14aryl,where C1-C10alkyl is unsubstituted or substituted by one radical Ra22and where C3-C10cycloalkyl and C6-C14aryl are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc2.

16. A compound (1) is of the formula (Ia)where R5is Ra33or Link’-(R4)k; k is 1 or 2; Link’ is C1-C8alkandiyl or C1-C8alkantriyl, where one of the CH2groups of C1-C8alkandiyl and C1-C8alkantriyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene; and where 1, 2 or 3 of the CH2groups of C1-C8alkandiyl and C1-C8alkant- riyl may be replaced by O, C(O), C(O)-O, NH-C(O), NH-C(O)-O or NH- C(O)-NH, and where C6-C14arylene and C3-C10cycloalkylene are unsubstituted or carry 1, 2 or 3 radicals Rcyc4; Ra33is selected from C(O)-R11, C(O)-OR12, C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1- C4-alkyl)3, A-Ra4, C3-C10cycloalkyl, C6-C14aryl, C3-C10heterocyclyl or C3-C14hetaryl, where the 4 last mentioned radicals are unsubstituted or substi- tuted by 1, 2, 3 or 4 radicals Rcyc3; and Ra4is selected from H, CN, C1-C6-alkyloxy, C1-C6-fluoroalkoxy, C(O)-R11, O-C(O)-R11, NH-C(O)-R11, C(O)-OR12a, O-C(O)-OR12, C(O)-NHR13, O-C(O)-NHR13, Si(C1-C4-alkyl)3, Si(O-C1-C4-alkyl)3, C3-C10cycloalkyl, C3-C10cycloalkoxy, C6-C14aryl, C6-C14aryloxy, C3-C10heterocyclyl, C3-C10heterocy- clyloxy, C3-C14hetaryl or C3-C14hetaryloxy, where the 8 last mentioned rad- icals are unsubstituted or substituted by 1, 2, 3 or 4 radicals Rcyc3;A is C1-C9alkandiyl, where one of the CH2groups of C1-C9alkandiyl may be replaced by one of C6-C14arylene and C3-C10cycloalkylene, and where 1, 2, 3 or 4 of the CH2groups of C1-C9alkandiyl may be replaced by O and where C3-C10cycloalkylene and C6-C14arylene are unsubstituted or substi- tuted by 1, 2, 3 or 4 radicals Rcyc4; R4is a radical of the formula (R4aa)and where Rcyc3, Rcyc4independently of each other are selected from selected from the group consisting of F, Cl, Br, CN, NO2, C1-C10alkyl, C1-C10fluoroalkyl, C1- C10alkyloxy, C1-C10fluoroalkoxy, C(O)-R11, O-C(O)-R11, C(O)-OR12a, O-C(O)- OR12, C(O)-NHR13and O-C(O)-NHR13and C6-C14aryl; R11is selected from hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl; R12ais hydrogen, C1-C10alkyl, C1-C10fluoroalkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl; and R12, R13independently of each other are selected from C1-C10alkyl, C1-C10fluoro- alkyl, C2-C10alkenyl, C3-C10cycloalkyl and C6-C14aryl.

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