Method for intraring double bond isomerization

Abstract

The present invention relates to the field of organic synthesis. More specifically, the present invention provides a method for preparing 1-(cycloalk-1-en-1-yl)acyl derivatives or 1-(cycloalkadien-1-yl)acyl derivatives, which involves the isomerization of conjugated intracyclic carbon-carbon double bonds in the presence of a catalyst system comprising palladium (Pd) and molecular hydrogen or a hydrogen source.

Description

Technical Field

[0001] The present invention relates to the field of organic synthesis. More particularly, the present invention provides a process for preparing 1-(cycloalk-1-en-1-yl)acyl derivatives or 1-(cycloalkadien-1-yl)acyl derivatives, which involves conjugated intracyclic carbon-carbon double bond isomerization in the presence of a catalyst system comprising palladium (Pd) and molecular hydrogen or a hydrogen source.

[0002] Background Many 1-(cycloalk-1-en-1-yl)acyl derivatives or 1-(cycloalkadien-1-yl)acyl derivatives defined by formula (I) are useful products in themselves or useful intermediates for the preparation of other important raw materials. Compounds of formula (I) are of particular interest to the fragrance industry, and in particular 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one is an important intermediate for the preparation of industrially important compounds such as Dynascone® (1-(5,5-dimethyl-1-cyclohexen-1-yl)-4-penten-1-one; manufactured by Firmenich SA). Most of the preparations of 1-(cycloalk-1-en-1-yl)acyl 1-(cycloalkadien-1-yl)acyl derivatives result in unwanted positional isomers or mixtures of positional isomers where the double bond is not in the correct position and require additional isomerization reactions. However, the isomerization reaction of conjugated intracyclic carbon-carbon double bonds to obtain 1-(cycloalk-1-en-1-yl)acyl derivatives or 1-(cycloalkadien-1-yl)acyl derivatives has not been reported so far. Therefore, it is necessary to develop such an isomerization method.

[0003] The present invention enables the high-selectivity production of 1-(cycloalk-1-en-1-yl)acyl derivatives or 1-(cycloalkadien-1-yl)acyl derivatives through intramolecular double bond isomerization in the presence of a catalyst system comprising palladium (Pd) and molecular hydrogen or a hydrogen source.

[0004] Description of the Invention Here, the present inventors have found that 1-(cycloalk-1-en-1-yl)acyl derivatives or 1-(cycloalkadien-1-yl)acyl derivatives can be advantageously produced by the catalytic isomerization as described, minimizing by-product formation and providing high productivity.

[0005] Accordingly, a first object of the present invention is a process for preparing a 1-(cycloalk-1-en-1-yl)acyl derivative or a 1-(cycloalkadien-1-yl)acyl derivative, which comprises isomerization of an intra-ring carbon-carbon double bond, wherein the isomerization is carried out by contacting a substrate containing a conjugated intra-ring carbon-carbon double bond with i) palladium (Pd) and ii) a catalyst system comprising molecular hydrogen or a hydrogen source.

[0006] For the sake of clarity, the expression "hydrogen source" is intended to have its ordinary meaning in the art, i.e., a compound capable of generating molecular hydrogen (i.e., H 2 ) in the reaction medium, hydrogen atoms or equivalents.

[0007] For the sake of clarity, the expression "conjugated intra-ring carbon-carbon double bond" is intended to have its ordinary meaning in the art, i.e., it is understood that the substrate contains at least one double bond conjugated with an acyl functional group.

[0008] According to any embodiment of the present invention, the 1-(cycloalk-1-en-1-yl)acyl derivative or 1-(cycloalkadien-1-yl)acyl derivative is in the form of any one of its stereoisomers, or a mixture thereof, and is a compound of the following formula,

Chemical formula

[0009] According to any embodiment of the present invention, the substrate is a compound of the following formula in the form of any one of its stereoisomers, or a mixture thereof:

Chemical formula

[0010] According to any embodiment of the present invention, the 1-(cycloalk-1-en-1-yl)acyl derivative or 1-(cycloalkadien-1-yl)acyl derivative is, in the form of any one of its stereoisomers, or a mixture thereof, a compound of the following formula: [Chemical formula] In the formula, one dotted line is a carbon-carbon single bond, and the other is a carbon-carbon single bond or a carbon-carbon double bond; m is an integer from 0 to 7; n is an integer from 1 to 8; R 1 is a C 1-6 alkyl group, C 2-6 alkenyl group or C 1-6 alkoxy group; each R 2 represents, simultaneously or independently, a substituent of the ring, and is a C 1-6 alkyl group or C 2-6 alkenyl group; or two R 2 groups, or an R 1 and one R 2 group together form, each being optionally substituted by one or more C 1-6 alkyl groups, C 2-6 alkenyl groups or C 1-6 alkoxy groups, a C 5-8 cycloalkyl group or C 5-8 forms a cycloalkenyl group.

[0011] According to any embodiment of the present invention, the substrate is, in the form of any one of its stereoisomers, or a mixture thereof, a compound of the following formula: [Chemical formula] In the formula, one of the dotted lines is a carbon-carbon single bond, and the other is a carbon-carbon single bond or a carbon-carbon double bond; m is an integer from 0 to 7; n is an integer from 1 to 8; R 1 is a C 1-6 alkyl group, C 2-6 alkenyl group or C 1-6 alkoxy group; each R 2 represents, simultaneously or independently, a substituent of the ring and is a C 1-6 alkyl group or C 2-6 alkenyl group; or two R 2 groups, or an R 1 and one R 2 group together form a C 1-6 cycloalkyl group or C 2-6 cycloalkenyl group which may each be substituted by one or more C 1-6 alkyl groups, C 5-8 alkenyl groups or C 5-8 alkoxy groups.

[0012] For the sake of clarity, expressions such as "any one of its stereoisomers, or a mixture thereof" are understood by those skilled in the art to have their ordinary meaning, i.e., it means that the compound of formula (I) or the compound of formula (II) can be a pure enantiomer or diastereomer. In other words, the compound of formula (I) or the compound of formula (II) can have several stereocenters, and each of these stereocenters can have two different stereochemistries (e.g., R or S). The compound of formula (I) or the compound of formula (II) can be in the form of a pure enantiomer, or in the form of a mixture of enantiomers or diastereoisomers. The compound of formula (I) or the compound of formula (II) can be a racemate or a scalemic form. Therefore, the compound of formula (I) or the compound of formula (II) can be one stereoisomer, or can be in the form of a composition containing or consisting of various stereoisomers.

[0013] For the sake of clarity, expressions such as "one of the dotted lines is a carbon-carbon single bond and the other is a carbon-carbon single bond or a carbon-carbon double bond" are understood by those skilled in the art to have their ordinary meaning, that is, the entire bond (solid and dotted lines) between the carbon atoms connected by the dotted line is a carbon-carbon single bond or a carbon-carbon double bond. In other words, the compounds of formulas (I) and (II) are cycloalkenyl derivatives or cycloalkadienyl derivatives. Those skilled in the art fully recognize that when one of the dotted lines is a carbon-carbon double bond, the adjacent dotted line cannot be a double bond. In other words, the compound of formula (I) can be 1-(cycloalken-1-yl)acyl of formula (Ia) or 1-(cycloalkadien-1-yl)acyl of formula (Ib) in any one form of its stereoisomers or as a mixture thereof,

Chemical formula

Chemical formula

[0014] The terms "alkyl", "alkoxyl" and "alkenyl" are understood to include branched and straight-chain alkyl groups, alkoxyl groups and alkenyl groups. The term "alkenyl" or "cycloalkenyl" is understood to include one olefinic double bond. The term "cycloalkyl" or "cycloalkenyl" is understood to include monocyclic groups.

[0015] For the sake of clarity, "R 2Expressions such as "represents a substituent of the ring" are understood by those skilled in the art to have their ordinary meaning, i.e., the group is attached to the ring at any one of the available positions.

[0016] The term "optionally" is understood to mean that a particular group which may be substituted may or may not be substituted by a particular functional group. The term "one or more" is understood to mean substituted by 1 to 7, preferably 1 to 5, preferably 1 to 3, more preferably 1 to 2 of the particular functional groups.

[0017] For the sake of clarity, the expression "two R 2 groups, or R 1 and one R 2 group together form a C 5-8 cycloalkyl group or a C 5-8 cycloalkenyl group" means that the carbon atom to which both groups are attached is included in a C 5-8 cycloalkyl group or a C 5-8 cycloalkenyl group.

[0018] According to any embodiment of the present invention, when the substrate is a compound of formula (IIb), the isomerization results in a composition comprising the preparation of a 1-(cycloalkadien-1-yl)acyl derivative of formula (Ib), or at least 50% of a 1-(cycloalkadien-1-yl)acyl derivative of formula (Ib) and up to 50% of a 1-(cycloalkadien-1-yl)acyl derivative of formula (A) in any one form of its stereoisomers, or a mixture thereof,

Chemical formula

[0019] According to any embodiment of the present invention, the dotted line is a single bond.

[0020] According to any embodiment of the present invention, 1-(cycloalk-1-en-1-yl)acyl is a compound of the following formula in the form of any one of its stereoisomers, or a mixture thereof,

Chemical formula

[0021] According to any embodiment of the present invention, the substrate is a compound of the following formula in the form of any one of its stereoisomers, or a mixture thereof,

Chemical formula

[0022] According to any embodiment of the present invention, the compound of formula (II) is different from the compound of (I). That is, the R 2 group is such that the compound of formula (II) is not the compound of formula (I). In particular, the compound of formula (II') is different from the compound of (I'). That is, the R 2 group is such that the compound of formula (IIa) is not the compound of formula (Ia). More particularly, the compound of formula (IIa) is different from the compound of formula (Ia). That is, the R 2 group is such that the compound of formula (IIa) is not the compound of formula (Ia).

[0023] According to any embodiment of the present invention, the compounds of formula (II), (II') or (IIa), and the compounds of formula (I), (I') or (Ia) may contain at least one R 2 group at the 2, 3, 5 or 6 position, or at the 2, 3, 4 or 5 position. Specifically, the compounds of formula (II), (II') or (IIa), and the compounds of formula (I), (I') or (Ia) may contain at least one R 2 group at the 3 or 5 position, or at the 4 or 5 position. Specifically, the compounds of formula (II), (II') or (IIa), and the compounds of formula (I), (I') or (Ia) may contain at least one R 2 group at the 5 position. Even more specifically, the compounds of formula (II), (II') or (IIa), and the compounds of formula (I), (I') or (Ia) may contain at least two R 2 groups at the 5 position.

[0024] According to any embodiment of the present invention, m may be an integer from 0 to 5. In particular, m may be an integer from 0 to 3. In particular, m may be an integer from 0 to 2. In particular, m may be 0 or 1. Even more particularly, m may be 1.

[0025] According to an optional embodiment of the present invention, R 2 may be used simultaneously or independently, C 1-4 Alkyl group or C 2-4 alkenyl group or two R 2 The groups together form one or more C 1-4 Alkyl group, C 2-4 Alkenyl group or C 1-4 C optionally substituted by an alkoxy group 5-6 Forms a cycloalkyl group. In particular, R 2 may be used simultaneously or independently, C 1-3 Alkyl group or C 2-4 alkenyl group or two R 2 The groups together form one or more C 1-3 Alkyl group, C 2-3 Alkenyl group or C 1-3 Alkoxy-substituted C 5-6 Forms a cycloalkyl group. In particular, R 2 may be used simultaneously or independently, C 1-3 Alkyl group or C 2-4 alkenyl group or two R 2 The groups together form one or more C 1-2 Alkyl C 1-2 Alkoxy-substituted C 5-6 Forms a cycloalkyl group. In particular, R 2 may be used simultaneously or independently, C 1-3 It may be an alkyl group or two R 2 The bases are together, C 5-6 Forms a cycloalkyl group. In particular, R 2 may simultaneously or independently be a methyl or ethyl group. More particularly, R 2 can be a methyl group.

[0026] According to any embodiment of the present invention, n can be an integer from 1 to 6, further from 1 to 4, further from 1 to 3, and even further from 1 to 2. Specifically, n can be 1 or 2 or 3. Even more specifically, n can be 2.

[0027] According to any embodiment of the present invention, the compound of formula (I) is a compound of the following formula in any one form of its stereoisomers or as a mixture thereof,

Chemical formula

[0028] According to any embodiment of the present invention, the compound of formula (III) is not the same as the compound of formula (IV). In other words, the compound of formula (III) is different from the compound of formula (IV).

[0029] According to any embodiment of the present invention, p is 1. In other words, the compound of formula (III) is in any one form of its stereoisomers or as a mixture thereof and is a compound of the following formula: [Chemical formula] In the formula, R 1 is a C 1-6 alkyl group, a C 2-6 alkenyl group or a C 1-6 alkoxy group; each R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 and R 10 are, independently of one another, a hydrogen atom, a C 1-6 alkyl group or a C 2-6 alkenyl group; or two of the groups of R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 and R 10 join together to form a C 1-6 cycloalkyl group or a C 2-6 cycloalkenyl group, each of which may be substituted by one or more C 1-6 alkyl groups, C 5-8 alkenyl groups or C 5-8 alkoxy groups; or R 3 and R 1 join together to form a C 1-6 cycloalkyl group or a C 2-6 cycloalkenyl group, each of which may be substituted by one or more C 1-6 alkyl groups, C 5-8 alkenyl groups or C 5-8 alkoxy groups; or R 4 and R 1 join together to form a C 1-6 cycloalkyl group or a C 2-6 cycloalkenyl group, each of which may be substituted by one or more C 1-6 alkyl groups, C 5-8 alkenyl groups or C 5-8 alkoxy groups, provided that R 3 , R 4 , R5 , R 6 , R 7 , R 8 , R 9 and R 10 are such that the compound of formula (V) is different from the compound of formula (VI) defined below.

[0030] The compound of formula (IV) is in any one form of its stereoisomers, or as a mixture thereof, and is of the following formula: [Chemical formula] wherein R 1 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 and R 10 have the same meaning as defined above.

[0031] According to any embodiment of the present invention, the compound of formula (V) is not the same as the compound of formula (VI). In other words, the compound of formula (V) is different from the compound of formula (VI).

[0032] According to any embodiment of the present invention, at least one of the groups of R 4 , R 3 ; R 10 and R 9 is not a hydrogen atom, and compounds of formula (III) or (V) in which R 3 is the same as R 10 , R 4 is the same as R 9 , and R 5 is the same as R 8 are excluded. Specifically, at least one of the groups of R 4 and R 9 is not a hydrogen atom.

[0033] According to any embodiment of the present invention, R 3 , R 4 , R 5 , R7 and R 10 each independently represents a hydrogen atom, C 1-4 alkyl group or C 2-4 alkenyl group. Specifically, R 3 , R 4 , R 5 , R 7 and R 10 each independently represents a hydrogen atom or C 1-3 alkyl group. Specifically, R 3 , R 4 , R 5 , R 7 and R 10 each independently represents a hydrogen atom or C 1-2 alkyl group. Even more specifically, R 3 , R 4 , R 5 , R 7 and R 10 can represent a hydrogen atom.

[0034] According to any embodiment of the present invention, the compound of formula (V) is a compound of the following formula in any one form of its stereoisomers or as a mixture thereof,

Chemical formula

Chemical formula

[0035] According to any embodiment of the present invention, at least one of the groups of R 9 , R 8 and R 6 is not a hydrogen atom.

[0036] According to any embodiment of the present invention, R 6 may represent a hydrogen atom, a C 1-4 alkyl group or a C 2-4 alkenyl group. Specifically, R 6 may represent a hydrogen atom or a C 1-3 alkyl group. Specifically, R 6 may represent a hydrogen atom or a C 1-2 alkyl group. Specifically, R 6 may represent a hydrogen atom or a methyl group. Even more specifically, R 6 may represent a hydrogen atom.

[0037] According to any embodiment of the present invention, the compound of formula (VII) is not the same as the compound of formula (VIII).

[0038] According to any embodiment of the present invention, the compound of formula (VII) is in any one form of its stereoisomers, or as a mixture thereof, and is a compound of the following formula:

Chemical formula

Chemical formula

[0039] According to any embodiment of the present invention, at least one of the groups of R 9 and R 8 is not a hydrogen atom.

[0040] According to any embodiment of the present invention, R 8 represents a hydrogen atom, C 1-4 alkyl group or C 2-4 alkenyl group. Specifically, R 8 represents a hydrogen atom, C 1-3 alkyl group or C 2-3 alkenyl group. Specifically, R 8 represents a hydrogen atom or C 1-2 alkyl group. Even more specifically, R 8 may represent a methyl group.

[0041] According to any embodiment of the present invention, R 9 represents a hydrogen atom, C 1-4 alkyl group or C 2-4may represent an alkenyl group. Specifically, R 9 is a hydrogen atom, C 1-3 alkyl group or C 2-3 may represent an alkenyl group. Specifically, R 9 is a hydrogen atom or C 1-2 alkyl group. Even more specifically, R 9 may represent a methyl group.

[0042] According to any embodiment of the present invention, R 1 is C 1-4 alkyl group, C 2-4 alkenyl group or C 1-4 alkoxy group. Specifically, R 1 is C 1-3 alkyl group, C 2-3 alkenyl group or C 1-3 alkoxy group. Specifically, R 1 is C 1-3 alkyl group. Specifically, R 1 may be a methyl group, an ethyl group or a propyl group. Even more specifically, R 1 may be a methyl group.

[0043] Non-limiting examples of suitable compounds of formula (I) may include 1-(5,5-dimethylcyclohex-1-en-1-yl)ethan-1-one, 1-(5-ethyl-5-methylcyclohex-1-en-1-yl)ethan-1-one, 1-(5,5-dimethylcyclohex-1,3-dien-1-yl)ethan-1-one, 1-(4,5,5-trimethylcyclohex-1-en-1-yl)ethan-1-one, 1-(4-isopropyl-4-methylcyclopent-1-en-1-yl)ethan-1-one.

[0044] Non-limiting examples of suitable compounds of formula (II) can include 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one, 1-(3-ethyl-3-methylcyclohex-1-en-1-yl)ethan-1-one, 1-(3,3-dimethylcyclohex-1,4-dien-1-yl)ethan-1-one, 1-(3,3,4-trimethylcyclohex-1-en-1-yl)ethan-1-one, 1-(3-isopropyl-3-methylcyclopent-1-en-1-yl)ethan-1-one.

[0045] According to any embodiment of the present invention, the catalyst system contains palladium (Pd) in the form of a homogeneous complex or in the form of elemental metal. Specifically, the catalyst system contains palladium (Pd) in the form of elemental metal. Suitable forms of such metals for carrying out chemical reactions are well known to those skilled in the art.

[0046] According to any one of the above embodiments of the present invention, the palladium (Pd) is supported on a support material.

[0047] For the sake of clarity, the support material is intended to be a material on which such a metal can be deposited and which is inert to the hydrogen source and the substrate.

[0048] According to any one of the above embodiments of the present invention, specific and non-limiting examples of the support material are carbon, silica or aluminum oxide. Such supports are well known to those skilled in the art.

[0049] The supported palladium (Pd) is a known compound and is commercially available. Those skilled in the art can select the preferred type of metal as the method by which it is deposited on the support, as the proportion of the metal on the support material, as the form (powder, granule, pellet, extrudate, paste....), and as the surface area of the support.

[0050] According to any one of the above embodiments of the present invention, the amount of the metal with respect to the support can range from 0.05% to 25% w / w, or even from 1% to 6% with respect to the weight of the support used.

[0051] Palladium (Pd) can be added in a wide range of concentrations to the reaction medium of the process of the present invention, either in a supported form or by itself. As a non-limiting example, as the metal concentration, values in the range of 0.01 mol% to 10 mol% with respect to the total amount of the substrate can be mentioned. Preferably, the metal concentration is 0.02 mol% to 5 mol%, or even more preferably 0.04 mol% to 2 mol%. As is known to those skilled in the art, the optimal concentration of the metal depends on the nature of the metal, the nature of the substrate, the temperature and pressure of H 2 used during the process, and the desired reaction time when the process is carried out batchwise or continuously.

[0052] The supported palladium may be recycled at the end of the process of the present invention. In other words, the supported palladium may be recovered at the end of the process of the present invention and used several times in the process of the present invention.

[0053] The process according to the present invention is carried out in the presence of molecular hydrogen or a hydrogen source.

[0054] According to any one of the above embodiments of the present invention, the hydrogen source can be a transfer hydrogenating agent. Specific and non-limiting examples of catalytic transfer hydrogenating agents are tetralin, formic acid, formates (e.g., sodium formate, potassium formate or ammonium formate), limonene or mixtures thereof. Specifically, the transfer hydrogenating agent may be tetralin, formic acid, formates, limonene or mixtures thereof. Even more specifically, the transfer hydrogenating agent may be formic acid, formates, limonene or mixtures thereof.

[0055] The mobile hydrogen agent can be added to the reaction medium of the process of the present invention at a wide range of concentrations. As non-limiting examples, as the hydrogen source concentration, values in the range of 0.01 mol% to 100 mol%, or even 0.01 mol% to 10 mol%, or still further 0.01 mol% to 5 mol% with respect to the amount of the substrate can be mentioned. When a small part of the mobile hydrogenating agent generates molecular hydrogen, it is used in a large amount. For example, about 10% of tetralin is converted to molecular hydrogen. As is known to those skilled in the art, it goes without saying that the optimal concentration of the hydrogen source depends on the nature of the hydrogen source, the nature of the substrate, the temperature and catalyst used in the process, and the desired reaction time.

[0056] According to any one of the above embodiments of the present invention, as an alternative to the mobile hydrogenating agent, pure or molecular hydrogen mixed with an inert gas can be used. Specific and non-limiting examples of such inert gases are nitrogen or argon. H 2 / inert gas volume ratio is 1 / 1 to 0.01 / 1, and more preferably the ratio is 0.05 / 1.

[0057] Molecular hydrogen can be added to the reaction medium of the process of the present invention at a wide range of concentrations. As non-limiting examples, as the molecular hydrogen concentration, values in the range of 0.01 mol% to 100 mol% with respect to the amount of the substrate can be mentioned. Preferably, the hydrogen source concentration is 0.01 mol% to 10 mol% with respect to the amount of the substrate. Preferably, the hydrogen source concentration is 0.01 mol% to 8 mol% with respect to the amount of the substrate. Still more preferably, the hydrogen source concentration is 0.01 mol% to 5 mol% with respect to the amount of the substrate. Of course, those skilled in the art can sufficiently adjust the pressure or flow rate of molecular hydrogen (for example, in a continuous process) batchwise or continuously to obtain this concentration range as a function of the process. Those skilled in the art can also sufficiently adjust the concentration of molecular hydrogen as a function of the catalyst load and the dilution of the substrate in the solvent.

[0058] In the process of the present invention, a hydrogen source or molecular hydrogen is present in an amount of 0.01 mol% to 10 mol%, more preferably 0.01 mol% to 8 mol%, and even more preferably 0.01 mol% to 5 mol% based on the amount of the substrate.

[0059] The process of the present invention can be carried out under batch or continuous conditions. According to a particular embodiment of the present invention, the process is continuous as it allows for an increase in productivity.

[0060] The reaction can be carried out in the presence or absence of a solvent. If a solvent is required or used for practical reasons, in such reaction types, any conventional solvent can be used for the purposes of the present invention. Non-limiting examples include C 6-12 aromatic solvents such as toluene, 1,3 - diisopropylbenzene, paraxylene, cumene, pseudocumene, benzyl acetate, xylene or mixtures thereof, C 3-16 alkanes such as hexadecane, ether solvents such as tetrahydrofuran, butyl ether, methyltetrahydrofuran or mixtures thereof. Specifically, the solvent has a boiling point above 100 °C. The choice of solvent is a function of the nature of the substrate and the complex, and a person skilled in the art can adequately select the most convenient solvent for each case in order to optimize the reaction.

[0061] The temperature at which isomerization can be carried out is from 120 °C to 300 °C. More preferably, in a continuous process, it is in the range of 150 °C to 250 °C, and in a batch process, it is in the range of 150 °C to 200 °C. Of course, a person skilled in the art can also select a preferred temperature as a function of the melting and boiling points of the starting and final products and the desired time of the reaction or conversion.

[0062] According to any one of the above embodiments of the present invention, the compound of formula (II) can be prepared according to several methods known in the art, such as the Diels - Alder reaction, cyclization reaction or Friedel - Craft reaction. A person skilled in the art would be able to select the best conditions for preparing the compound of formula (II). Specifically, the process of the present invention further comprises the preparation of the compound of formula (IIa) from the compound of the following formula in the form of any one of its stereoisomers, or a mixture thereof, [Chemical formula] wherein n, R 1 and R 2 have the same meaning as defined above, and m' is an integer from 0 to 7. The preparation of the compound of formula (IIa) from the compound of formula (XI) can be carried out under normal conditions known to those skilled in the art, i.e., in the presence of an acid such as a Bronsted acid or a Lewis acid. The preparation of the compound of formula (IIa) from the compound of formula (XI) may include the step of treating the compound of formula (XI) with an acid. According to a specific embodiment of the present invention, the acid used in the preparation of the compound of formula (IIa) may have a pKa of less than 3. Specific and non - limiting examples of Bronsted acids may be selected from the group consisting of phosphoric acid, p - toluenesulfonic acid, methanesulfonic acid, camphorsulfonic acid, methanedisulfonic acid, methanetrissulfonic acid, 2,4 - dinitrobenzenesulfonic acid. Specifically, the Bronsted acid may be phosphoric acid. Specific and non - limiting examples of Lewis acids are metal triflates, such as Al(OTf) 3 , lanthanide triflates, such as Sc(OTf) 3 , Bi(OTf) 3 , metal tetrafluoroborates, such as Zn(BF 4 ) 2 , and metal halides, such as AlX 3 , RAlX 2 , R 2 AlX, BX 3 (wherein X is a halide and R is a C 1-3 alkyl group), ZnCl 2 , ZnBr 2may be selected from the group consisting of.

[0063] According to any embodiment of the present invention, m' may be an integer from 0 to 5. Specifically, m' may be an integer from 0 to 3. Specifically, m' may be an integer from 0 to 2. Even more specifically, m' may be 1.

[0064] According to any one of the above embodiments of the present invention, the compound of formula (XI) is in the form of any one of its stereoisomers, or a mixture thereof, and is of the following formula:

Chemical formula

[0065] Non-limiting examples of suitable compounds of formula (XII) may include 3,7-dimethyloct-6-en-1-yn-3-ol, 3,6,7-trimethyloct-6-en-1-yn-3-ol. The compound of formula (IIa) starting from 3,6,7-trimethyloct-6-en-1-yn-3-ol is 1-(3-isopropyl-3-methylcyclopent-1-en-1-yl)ethan-1-one, 1-(3,3,4-trimethylcyclohex-1-en-1-yl)ethan-1-one or a mixture thereof.

[0066] The acid can be added to the reaction medium of the process of the present invention at a wide range of concentrations. As non-limiting examples, as the acid concentration, values in the range of 0.01 to 10 equivalents, preferably 0.1 to 2 equivalents, relative to the amount of the substrate can be mentioned. As known to those skilled in the art, the optimal concentration of the acid depends on the nature of the acid, the nature of the substrate, and the temperature used in the process, as well as the desired reaction time.

[0067] The reaction can be carried out in the presence or absence of a solvent. If a solvent is required or used for practical reasons, in such reaction types, any conventional solvent can be used for the purposes of the present invention. Non-limiting examples include C 6-12 aromatic solvents such as toluene, 1,3 - diisopropylbenzene, cumene, pseudocumene, benzyl acetate, xylene or mixtures thereof, C 3-16 alkanes such as hexadecane, hexane, heptane, cyclohexane, ether solvents such as tetrahydrofuran, methyltetrahydrofuran or mixtures thereof. The choice of solvent is a function of the nature of the substrate and the acid, and one skilled in the art can sufficiently select the most convenient solvent in each case to optimize the reaction.

[0068] The temperature at which the compound of formula (IIa) can be prepared from the compound of formula (XI) is from 50 °C to 180 °C. More preferably, it is in the range of 70 °C to 120 °C. Of course, one skilled in the art can also select the preferred temperature as a function of the melting and boiling points of the starting and final products and the desired time of the reaction or conversion.

[0069] According to any embodiment of the present invention, the compound of formula (I) which is 1-(5,5 - dimethylcyclohex - 1 - en - 1 - yl)ethan - 1 - one can be further converted to 1-(5,5 - dimethyl - 1 - cyclohexen - 1 - yl)-4 - penten - 1 - one. The preparation of 1-(5,5 - dimethyl - 1 - cyclohexen - 1 - yl)-4 - penten - 1 - one from 1-(5,5 - dimethylcyclohex - 1 - en - 1 - yl)ethan - 1 - one is well known in the art under allylation conditions etc. One skilled in the art will be able to select the best conditions for preparing 1-(5,5 - dimethyl - 1 - cyclohexen - 1 - yl)-4 - penten - 1 - one.

[0070] Accordingly, another object of the present invention is a process for preparing 1-(5,5 - dimethyl - 1 - cyclohexen - 1 - yl)-4 - penten - 1 - one, comprising a) Isomerizing 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one by contacting it with a catalyst system comprising i) palladium (Pd) and ii) molecular hydrogen or a hydrogen source, to obtain 1-(5,5-dimethylcyclohex-1-en-1-yl)ethan-1-one; and b) converting 1-(5,5-dimethylcyclohex-1-en-1-yl)ethan-1-one to 1-(5,5-dimethyl-1-cyclohexen-1-yl)-4-penten-1-one.

[0071] A typical manner for carrying out the process of the present invention is reported below in the Examples.

Examples

[0072] Herein, the present invention will be described in more detail by the following examples. Abbreviations have their usual meanings in the art, and temperatures are indicated in degrees Celsius (°C). NMR spectra were acquired using either a Bruker Avance II Ultrashield 400 plus operating at 400 MHz ([[]]END]] 1 H) and 100 MHz ([[]]END]] 13 C), or a Bruker Avance III 500 operating at 500 MHz ([[]]END]] 1 H) and 125 MHz ([[]]END]] 13 C), or a Bruker Avance III 600 cryoprobe operating at 600 MHz ([[]]END]] 1 H) and 150 MHz ([[]]END]] 13 C). Spectra were internally referenced to 0.0 ppm of tetramethylsilane. 1The \(^1H\) NMR signal shift is expressed in δ ppm, and the coupling constant (J) is expressed in Hz together with the following multiplicities: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; b, broad (indicating unresolved coupling), and was interpreted using Bruker Topspin software. 13 The \(^{13}C\) NMR data are the chemical shift δ ppm, as well as from DEPT 90 and DEPT 135 experiments, C, quaternary (s); CH, methine (d); CH 2 , methylene (t); CH 3 , methyl (q) hybridization.

[0073] [Example 1] Preparation of 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one 500 g (0.6 eq) of 85% phosphoric acid and 4400 g of heptane were placed in a reactor. The mixture was stirred and heated to reflux via a Dean-Stark apparatus. 1100 g (1 eq) of 3,7-dimethylocta-6-en-1-yn-3-ol was fed over 6 hours, and then reflux was continued for an additional 4 hours. The reaction mixture was cooled to 60 °C and water was added. The acid phase was drained and the organic phase was washed with water at 60 °C. The solvent was concentrated under vacuum. 1050 g of crude material was obtained, and after fractional distillation (Bp 80 °C / 10.9 mbar), 605 g of 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one with a purity of 95% was obtained. 1 \(^1H-NMR\) (500 MHz, CDCl 3 ), δ (ppm): 6.53 (t, 1H); 2.27 (s, 3H); 2.15 (td, 2H); 1.61 (m, 2H); 1.43 (m, 2H); 1.06 (s, 6H) 13 \(^{13}C-NMR\) (125 MHz, CDCl 3 ), δ (ppm): 199.9; 149.7; 137.3; 36.3; 32.7; 29.1; 25.2; 23.1; 19.1

[0074] [Example 2] Preparation of 1-(3-Ethyl-3-methyl-cyclohexen-1-yl)ethan-1-one According to the procedure of Example 1, 3,7-Dimethylnona-6-en-1-in-3-ol (310.0 g) was converted to 1-(3-Ethyl-3-methyl-cyclohexen-1-yl)ethan-1-one (170.5 g, purity 94%) after fractional distillation (Bp 98 °C / 12.0 mbar). 1 H-NMR(500MHz,CDCl 3 ),δ(ppm):6.55(t,1H);2.28(s,3H);2.12 - 2.05(m,1H);1.69 - 1.63(m,1H);1.52 - 1.33(m,4H);1.02(s,3H);0.87(t,3H) 13 C-NMR(125MHz,CDCl 3 ),δ(ppm):199.8;149.3;138.0;35.7;34.5;33.2;26.1;25.3;23.3;18.9;8.4

[0075] [Example 3] Preparation of 1-(3-Isopropyl-3-methyl-cyclopent-1-en-1-yl)ethan-1-one According to the procedure of Example 1, 3,6,7-Trimethylocta-6-en-1-in-3-ol (310.0 g) was converted to 1-(3-Isopropyl-3-methyl-cyclopent-1-en-1-yl)ethan-1-one (165.8 g, purity 96%) after fractional distillation (Bp 96 °C / 12.0 mbar). 1 H-NMR(500MHz,CDCl 3 ),δ(ppm):6.52(t,1H);2.55 - 2.51(m,2H);2.31(s,3H);1.89 - 1.83(m,1H);1.71 - 1.65(m,1H);1.59 - 1.53(m,1H);1.04(s,3H);0.91(d,3H);0.87(d,3H) 13 C-NMR(125MHz,CDCl 3), δ (ppm): 197.5; 152.2; 143.2; 53.5; 35.9; 33.5; 29.6; 26.7; 22.5; 18.4; 18.0

[0076] [Example 4] Preparation of 1-(3,3-dimethylcyclohexa-1,4-dien-1-yl)ethan-1-one Into an ozonolysis reactor, 20.3 g of Δ 3 -carene, 150 mL of MeOH, and 150 mL of dichloromethane were added. After cooling the resulting solution to -78 °C, O 3 was used to treat it for 2 hours. A solution of triphenylphosphine (40.9 g) in dichloromethane (50 mL) was slowly added over 30 minutes at -35 °C to -25 °C. After stirring the reaction mixture for 45 minutes, the volatile substances were concentrated and then flash distilled to obtain 14.5 g of 2-(3-acetonyl-2,2-dimethyl-cyclopropyl)acetaldehyde with a purity of 95%, which was used without further purification.

[0077] In the next step, 2-(3-acetonyl-2,2-dimethyl-cyclopropyl)acetaldehyde (20.0 g) was poured into an ice-cooled solution of NaOH (18.3 g) in water (170 mL) and EtOH (100 mL). After 16 hours at room temperature, H 2 O was added (250 mL), and the mixture was extracted with ethyl acetate (2 × 100 mL). Then, the combined extracts were washed with 10% citric acid until pH = 5, then washed with 10% KHCO 3 until pH = 8, and finally washed with H 2 O (150 mL). The solvent was removed from the combined organic phases under reduced pressure, and then fractional distillation (Bp 94 °C / 11.0 mbar) was carried out to obtain 14.8 g of 1-(3,3-dimethylcyclohexa-1,4-dien-1-yl)ethan-1-one with a purity of 98%. 1 H-NMR (500 MHz, CDCl 3), δ(ppm): 6.62 (q, 1H); 5.69 (dt, 1H); 5.52 (dq, 1H); 2.80 (m, 2H); 2.33 (s, 3H); 1.14 (s, 6H) 13 C-NMR (125 MHz, CDCl 3 ), δ(ppm): 199.3; 147.2; 133.2; 121.6; 34.5; 29.9; 27.6; 25.1; 24.4

[0078] [Example 5] Catalytic Isomerization of 1-(3,3-Dimethylcyclohex-1-en-1-yl)ethan-1-one Using Pd / C Protocol 1: 1-(3,3-Dimethylcyclohex-1-en-1-yl)ethan-1-one (1430 g, 95%), 28 g of 5% Pd / C (50% water), and 250 g of pCymene were stirred at 175 °C, and then 22.8 g (8% mol) of formic acid was slowly added over 20 hours. The reaction mixture was cooled to 20 °C, filtered, and then subjected to fractional distillation to obtain three fractions: 1-(3,3-Dimethylcyclohexyl)ethan-1-one (114 g, Bp 63 °C / 10 mbar), 1-(3,3-Dimethylcyclohex-1-en-1-yl)ethan-1-one (429 g, Bp 78 °C / 10 mbar), and 1-(5,5-Dimethylcyclohex-1-en-1-yl)ethan-1-one (858 g, Bp 83 °C / 10 mbar).

[0079] Protocol 2: 1-(3,3-Dimethylcyclohex-1-en-1-yl)ethan-1-one (200 g, 95%) and 4 g of 5% Pd / C (50% water) were stirred at 175 °C, and then a 2% hydrogen solution in nitrogen (equivalent to 8% mol hydrogen) was bubbled through the suspension over 20 hours. The reaction mixture was cooled to 20 °C, filtered off, and then subjected to fractional distillation to obtain three fractions: 1-(3,3-dimethylcyclohexyl)ethan-1-one (14 g, Bp 63 °C / 10 mbar), 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one (60 g, Bp 78 °C / 10 mbar), and 1-(5,5-dimethylcyclohex-1-en-1-yl)ethan-1-one (120 g, Bp 83 °C / 10 mbar). 1 H-NMR(700MHz,CDCl 3 ),δ(ppm):6.87(m,1H);2.28(m,2H);2.28(s,3H);2.01(q,2H);1.34(t,2H);0.9(s,6H) 13 C-NMR(175MHz,CDCl 3 ),δ(ppm):199.5;139.7;138.7;36.4;34.2;28.5;28.0;25.3;24.1

[0080] [Example 6] Catalytic Isomerization of 1-(3-Ethyl-3-methyl-cyclohex-1-en-1-yl)ethan-1-one Using Pd / C According to Protocol 1 described in Example 5, the catalytic isomerization of 1-(3-ethyl-3-methyl-cyclohex-1-en-1-yl)ethan-1-one was carried out. The final composition was determined by GC-MS analysis and NMR analysis, and a conversion rate of 69% was obtained. The crude reaction mixture was purified using column chromatography to obtain 49% of 1-(5-ethyl-5-methyl-cyclohex-1-en-1-yl)ethan-1-one. No other positional isomers were detected. 1 H-NMR(500MHz,CDCl 3), δ (ppm): 6.89 (m, 1H); 2.29 (s, 3H); 2.28 - 2.25 (m, 2H); 2.01 (td, 2H); 1.37 - 1.35 (m, 2H); 1.29 - 1.24 (m, 2H); 0.85 (t, 3H); 0.83 (s, 3H) 13 C-NMR (125 MHz, CDCl 3 ), δ (ppm): 199.6; 140.1; 138.6; 34.8; 33.5; 31.9; 31.1; 25.4; 23.9; 23.7; 7.8

[0081] [Example 7] Catalytic Isomerization of 1-(3,3-Dimethylcyclohex-1,4-dien-1-yl)ethan-1-one Using Pd / C According to Protocol 2 described in Example 5, 1-(3,3-dimethylcyclohex-1,4-dien-1-yl)ethan-1-one was isomerized. The formation of 1-(5,5-dimethylcyclohex-1,3-dien-1-yl)ethan-1-one was determined by GC-MS analysis and NMR analysis, and a conversion rate of 55% was obtained for a yield of 15%. 1 H-NMR (500 MHz, CDCl 3 ), δ (ppm): 6.88 (d, 1H); 6.01 - 5.95 (m, 2H); 2.36 (s, 2H); 2.33 (s, 3H); 1.01 (s, 6H) 13 C-NMR (125 MHz, CDCl 3 ), δ (ppm): 199.2; 153.2; 136.1; 132.7; 117.5; 41.2; 34.0; 27.7; 27.1

[0082] [Example 8] Catalytic Isomerization of 1-(3-Isopropyl-3-methyl-cyclopenten-1-yl)ethan-1-one Using Pd / C 1-(3-Isopropyl-3-methyl-cyclopent-1-en-1-yl)ethan-1-one was isomerized according to Protocol 2 described in Example 5. The formation of 1-(4-isopropyl-4-methyl-cyclopent-1-en-1-yl)ethan-1-one was determined by GC-MS analysis and NMR analysis, and a conversion rate of 63% was obtained. No other positional isomers were detected.

[0083] [Example 9] Catalytic isomerization of 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one using Pd / C in EtOH (Comparative Example) RhCl 3 .3H 2 The O catalyst was replaced with Pd / C, and the isomerization of 1-(3,3-dimethylcyclohex-1-en-1-yl)ethan-1-one was carried out under the same reaction conditions as described by Takasago (European Patent No. 1162190). After 23 hours, no isomerization occurred.

Claims

1. A method for preparing a 1-(cycloalk-1-en-1-yl)acyl derivative or a 1-(cycloalkadien-1-yl)acyl derivative, comprising isomerization of an intraring carbon-carbon double bond, wherein the isomerization involves a substrate containing a conjugated intraring carbon-carbon double bond, i) Palladium (Pd) and, ii) Molecular hydrogen or a hydrogen source, A method that involves contacting a catalyst system containing [the specified substance].

2. The 1-(cycloalk-1-en-1-yl)acyl derivative or 1-(cycloalkadien-1-yl)acyl derivative is a compound of the following formula in the form of one of its stereoisomers or a mixture thereof: 【Chemistry 1】 In the formula, one dotted line is a carbon-carbon single bond, and the other is a carbon-carbon single bond or a carbon-carbon double bond; m is an integer from 0 to 7; n is an integer from 1 to 8; R １ is C １－６ an alkyl group, C ２－６ an alkenyl group or C １－６ an alkoxy group; each R ２ represents, simultaneously or independently, a substituent of the ring, C １－６ an alkyl group or C ２－６ an alkenyl group; or two R ２ groups, or an R １ and one R ２ group together form a C １－６ cycloalkyl group or C ２－６ cycloalkenyl group which may each be substituted by one or more C １－６ alkyl groups, C ５－８ alkenyl groups or C ５－８ alkoxy groups, the method according to claim 1.

3. The substrate is a compound of the following formula, in the form of one of its stereoisomers or a mixture thereof: 【Chemistry 2】 In the formula, one dotted line represents a carbon-carbon single bond, and the other represents a carbon-carbon single bond or a carbon-carbon double bond; m is an integer from 0 to 7; n is an integer from 1 to 8; R １ However, C １－６ alkyl group, C ２－６ Alkenyl group or C １－６ It is an alkoxy group; each R ２ However, simultaneously or independently, C represents a substituent of the ring. １－６ Alkyl or C ２－６ It is an alkenyl group; or two R groups. ２ Base, or R １ and one R ２ The bases come together, and each has one or more C １－６ alkyl group, C ２－６ Alkenyl group or C １－６ C may be substituted with an alkoxy group. ５－８ Cycloalkyl groups or C ５－８ The method according to claim 1, wherein a cycloalkenyl group is formed.

4. The 1-(cycloalk-1-en-1-yl)acyl derivative or 1-(cycloalkadien-1-yl)acyl derivative, in the form of one of its stereoisomers or a mixture thereof, has the following formula: 【Transformation 3】 In the formula, m is an integer from 0 to 7; n is an integer from 1 to 8; R １ However, C １－６ alkyl group, C ２－６ Alkenyl group or C １－６ It is an alkoxy group; each R ２ However, simultaneously or independently, C represents a substituent of the ring. １－６ Alkyl or C ２－６ It is an alkenyl group; or two R groups. ２ Base, or R １ and one R ２ The bases come together, and each has one or more C １－６ alkyl group, C ２－６ Alkenyl group or C １－６ C may be substituted with an alkoxy group. ５－８ Cycloalkyl groups or C ５－８ Forming a cycloalkenyl group, The substrate is a compound of the following formula, in the form of one of its stereoisomers or a mixture thereof: 【Chemistry 4】 In the formula, m is an integer from 0 to 7; n is an integer from 1 to 8; R １ However, C １－６ alkyl group, C ２－６ Alkenyl group or C １－６ It is an alkoxy group; each R ２ However, simultaneously or independently, C represents a substituent of the ring. １－６ Alkyl or C ２－６ It is an alkenyl group; or two R groups. ２ Base, or R １ and one R ２ The bases come together, and each has one or more C １－６ alkyl group, C ２－６ Alkenyl group or C １－６ C may be substituted with an alkoxy group. ５－８ Cycloalkyl groups or C ５－８ The method according to claim 1, wherein a cycloalkenyl group is formed.

5. The method according to any one of claims 2 to 4, wherein m is an integer from 0 to 2, preferably m is 1.

6. Each R ２ However, simultaneously or independently, C １－３ It is an alkyl group or two Rs ２ The bases come together, C ５－６ Forms a cycloalkyl group, preferably R ２ The method according to any one of claims 2 to 4, wherein is a methyl group.

7. The 1-(cycloalk-1-en-1-yl)acyl derivative or 1-(cycloalkadien-1-yl)acyl derivative is a compound of the following formula in any one of its stereoisomers or as a mixture thereof: 【Transformation 5】 wherein R １ is a C １－６ alkyl group, a C ２－６ alkenyl group or a C １－６ alkoxy group; each of R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ , and R １０ are, independently of one another, a hydrogen atom, a C １－６ alkyl group or a C ２－６ alkenyl group; or two of the groups of R ３ , R ４ , R ５ , R ６ , R ７ , R ８ [[ID=四十]], R ９ , and R １０ combine together to form a C １－６ cycloalkyl group or a C ２－６ cycloalkenyl group, each of which may be substituted by one or more C １－６ alkyl groups, C ５－８ alkenyl groups or C ５－８ alkoxy groups; or R ３ and R １ combine together to form a C １－６ cycloalkyl group or a C ２－６ cycloalkenyl group, each of which may be substituted by one or more C １－６ alkyl groups, C ５－８ alkenyl groups or C ５－８ alkoxy groups; or R ４ and R １ combine together to form a C １－６ cycloalkyl group or a C ２－６ cycloalkenyl group, each of which may be substituted by one or more C １－６ alkyl groups, C ５－８ alkenyl groups or C ５－８ alkoxy groups, provided that R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ and R １０ The compound of formula (V) is different from the compound of formula (VI) as defined below. The substrate, in one of its stereoisomers or as a mixture thereof, has the following formula: 【Transformation 6】 In the formula, R １ , R ３ , R ４ , R ５ , R ６ , R ７ , R ８ , R ９ and R １０ The method according to claim 1, having the same meaning as defined above.

8. The compound of formula (V) is, in one of its stereoisomers or as a mixture thereof, a compound of the following formula: 【Transformation 7】 In the formula, R １ However, C １－６ Alkyl alkyl group, C ２－６ Alkenyl group or C １－６ It is an alkoxy group; each R ８ and R ９ However, independently of each other, hydrogen atoms, C １－６ Alkyl or C ２－６ Represents an alkenyl group; or R ８ and R ９ When they come together, each has one or more C １－６ Alkyl alkyl group, C ２－６ Alkenyl group or C １－６ C may be substituted with an alkoxy group. ５－８ Cycloalkyl groups or C ５－８ Forms a cycloalkenyl group; The compound of formula (VI) is, in one of its stereoisomers or as a mixture thereof, of the following formula: 【Transformation 8】 In the formula, R １ , R ８ and R ９ The method according to claim 7, having the same meaning as defined above.

9. R １ C １－３ The method according to any one of claims 2 to 4, wherein the alkyl group is 2.

10. The method according to any one of claims 1 to 4, wherein the palladium is supported on carbon.

11. The method according to any one of claims 1 to 4, wherein the hydrogen source is tetralin, formic acid, formate, limonene, or a mixture thereof.

12. The method according to any one of claims 1 to 4, wherein the process is continuous.

13. The method further comprises preparing the compound of formula (IIa) from a compound of the following formula in the form of one of its stereoisomers or a mixture thereof, 【Chemistry 9】 In the formula, n, R １ and R ２ The method according to claim 4, wherein m' has the same meaning as defined in claim 4, and m' is an integer from 0 to 7.

14. The method according to claim 13, wherein the preparation of the compound of formula (IIa) from the compound of formula (XI) comprises a step of treating the compound of formula (XI) with an acid.

15. A method for preparing 1-(5,5-dimethyl-1-cyclohexen-1-yl)-4-penten-1-one, a) 1-(3,3-dimethylcyclohexa-1-en-1-yl)ethane-1-one, i) Palladium (Pd) and, ii) Molecular hydrogen or a hydrogen source, The process involves isomerizing 1-(3,3-dimethylcyclohexa-1-en-1-yl)ethane-1-one by contacting it with a catalyst system containing the following: b) A step of converting 1-(5,5-dimethylcyclohexa-1-en-1-yl)ethane-1-one to 1-(5,5-dimethyl-1-cyclohexen-1-yl)-4-penten-1-one, A method that includes this.

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