Novel phosphine ligands

Abstract

The present invention relates to compounds of formula (I) and (IV) and to a method for producing a compound of formula (I) and / or (IV) as defined herein. Furthermore, the present invention relates to a coordination complex comprising one, two, three, four or more compound(s) of formula (I) and / or (IV) as defined herein as ligand(s) and to a method for producing a coordination complex as defined herein. The present invention further relates to the use of a compound of formula (I) and / or (IV) as defined herein for producing a coordination complex as defined herein and to the use of a coordination complex as defined herein as a catalyst. Finally, the present invention relates to a method, preferably a hydrogen transfer reaction, more preferably for the isomerization of a double bond in a substrate, as defined herein.

Description

[0001] Novel phosphine ligands

[0002] The present invention primarily relates to compounds of formula (I) and (IV) and to a method for producing a compound of formula (I) and / or (IV) as defined herein. Secondly, the present invention relates to a coordination complex comprising one, two, three, four or more compound(s) of formula (I) and / or (IV) as defined herein as ligand(s) and to a method for producing a coordination complex as defined herein. The present invention further relates to the use of a compound of formula (I) and / or (IV) as defined herein for producing a coordination complex as defined herein and to the use of a coordination complex as defined herein as a catalyst. Finally, the present invention relates to a method, preferably a hydrogen transfer reaction, more preferably for the isomerization of a double bond in a substrate, as defined herein.

[0003] Further aspects of the present invention will arise from the description below, in particular from the examples, whereby these are not to be understood as limiting, as well as from the attached patent claims. In the last decades, noble metal complexes have been used as catalysts due to their high selectivity and superior reactivity. But due to the low relative abundance of and the increasing demand for noble metals like rhodium, ruthenium, iridium or palladium from different industry sectors, earth-abundant transition metals have become more interesting for industrial applications. Especially, the price difference between earth-abundant metals like cobalt, iron and nickel compared to noble metals makes the former interesting for industrial applications. Besides this, earth-abundant metals have a significantly lower toxicity.

[0004] Despite the rising demand and the steady academic research for new more sustainable and environmentally friendly catalysts, earth-abundant metal catalysts often show a considerably lower activity and selectivity compared to noble metal catalysts. Therefore, the development of highly efficient earth-abundant metal catalysts is of particularly great interest.

[0005] A large number of chemical reactions can be accelerated by homogeneous metal catalysts. The benefit of such metal catalysts is that they lead to better results compared to noncatalyzed reactions. In particular, the use of metal catalysts can achieve higher yields and better selectivities compared to non-catalyzed chemical reactions.

[0006] Examples of this include the regioselective hydroformylation of olefins with rhodium catalysts, the asymmetric hydrogenation of olefins or ketones with rhodium or ruthenium complexes or the regio- and chemoselective isomerization of double bonds in olefins.

[0007] Homogeneous metal catalysts may contain a metal atom or ion and one or more ligand(s) that is / are coordinated to the central atom. Due to their steric effects and electronic properties, the ligand(s) have a major influence on the reactivity and selectivity of the catalyst. Through targeted ligand synthesis, for example, the yield of the target product can be significantly increased.

[0008] The catalytic isomerization of double bonds in olefins is a highly efficient method in organic chemistry. The implementation is characterized by a high atom economy and has therefore attracted great interest both in academic research and in industrial applications due to its sustainable character. Recently, catalysts with transition metals such as iron, cobalt or nickel have attracted particular attention, as they are significantly more sustainable than rare earth metals due to their better availability, and because of their low costs. The following publications provide good overviews on this topic: "Base-metal-catalyzed Olefin Isomerization Reaction", X. Liu, B. Li, Q. Liu, Synthesis 2019, 51, 1293; "Hydride transfer reactions catalyzed by cobalt complexes" W. Ai, R. Zhong, X. Liu, Q. Liu, Chem. Rev. 2019, 119, 2876-2953; "Cobalt-catalyzed isomerization of alkenes", S. Zhang, M. Findlater, Synthesis 2021 , 53 (16), 2787-2797. In terms of sustainability and saving resources, the catalytic isomerisation of double bonds in olefins represents a nearly ideal transformation, because it is an energy efficient and atomically economic redox reaction, which produces no waste output. In this respect, transition metal catalysed olefin isomerization obeys several rules of the twelve principles of green chemistry at once. In consequence, catalytic isomerisation of olefins has attracted great interest both in academic research and industrial applications.

[0009] The reaction of molecules with heteroatoms such as nitrogen atoms represents an especially challenging form of isomerization reactions. Numerous noble metal catalysts (especially rhodium catalysts) have been reported for the isomerization of allylamines. Overviews and examples can be found in: Krompiec, S. et al. Coord. Chem. Rev. 2008, 252, 1819; Escoubet, S. et al. Eur. J. Org. Chem. 2005, 3855; Cadierno, V. et al. Inorg. Chim. Acta 2017, 455, 398.

[0010] Another even more specific form of isomerizations are reactions wherein the substrate not only contains one or more heteroatoms but also two or more double bonds and only one of the double bonds is to be selectively (regio-)isomerized. The following reaction is a prominent example of this type of reaction (Scheme 1):

[0011] Scheme 1 : Reaction of / V, / V-diethylgeranylamine to citronellal enamine

[0012] This reaction has high commercial relevance because it is an important key step in a synthetic menthol production process. Particularly challenging in this synthesis is the selective isomerization of only one of the two double bonds present.

[0013] Both enantioselective and racemic catalysts have been described for this reaction (see: H. Kumobayashi, S. Akutagawa, S. Otsuka, J. Am. Chem. Soc. 1978, 100, 3949; "Enantioselective isomerization of allylamine to enamine: practical asymmetric synthesis of (-)-menthol by Rh-BINAP catalysts. S. Akutagawa. Top. Catal., 1997, 271-274; "Catalytic Asymmetric Synthesis: Asymmetric Isomerization of Allylamines", I. Ojima (Edt.), Wiley- VCH, 1993, 41-61 ; "Discoveries of the catalysis of Asymmetric Isomerization of Allylamines and its Significance in Science and Industry. S. Otsuka. Acta Chem. Scan., 1996, 50, 353- 360; "Mechanism of the asymmetric isomerization of allylamines to enamines catalyzed by 2,2'-bis(diphenylphosphino)-1 ,1 'binaphthyl-rhodium complexes. R. Noyori et al. J. Am. Chem. Soc. 1990, 112, 4897-4905).

[0014] Despite the homogeneous metal catalysts described in the literature, there is still a need for further catalysts, as most of those described so far have significant disadvantages. For example, although the rhodium compounds described in the literature show good enantio- and regioselectivity, they are very sensitive to atmospheric oxygen, water and traces of chemical side components that poison the catalyst. In addition, the availability of rhodium has fallen sharply due to higher demand from other industries, which has led to a significant price increase. Furthermore, many of the literature-known catalysts are limited to simple olefins and cannot isomerize molecules that contain heteroatoms or multiple double bonds. On the other hand, the more readily available cobalt catalysts to date show significantly lower regioselectivity (55%, see below).

[0015] It was therefore the primary object of the present invention to provide compounds suitable for the formation of novel coordination complexes, which represent suitable catalysts, especially for the isomerization of / V, / V-diethylgeranylamine to citronellal enamine. Such novel catalysts preferably provide superior conversion and selectivity rates compared to catalysts known from the literature for this process. Thereby, preferably a better contribution to green chemistry shall be achieved. Furthermore, high turnover numbers for the isomerization process shall be obtained.

[0016] Furthermore, it was an object of the present invention to provide a method for the isomerization of olefins, especially of allylamines to enamines, which proceeds in economically useful or reasonable yields.

[0017] Further objects underlying the present invention follow from the description below and the present patent claims.

[0018] According to a first aspect of the present invention, the stated object is achieved by a compound of formula (I) (I), wherein R1is a residue independently selected from the group consisting of wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4, preferably a benzene ring, and / or R4forms an aromatic ring with R5, preferably a benzene ring, and wherein R2is a residue selected from the group consisting of

[0019] or R2is a residue according to formula (II) wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4, preferably a benzene ring, and / or R4forms an aromatic ring with R5, preferably a benzene ring, and wherein ,

[0020] Surprisingly, it was found that the new compounds of formula (I) are suitable for the formation of novel coordination complexes for the above mentioned purposes. The compounds of formula (I) according to the invention advantageously provide more electron rich systems resulting in superior conversion and selectivity rates when used as ligands in catalytic reactions. Furthermore, high turnover numbers for isomerization processes can be achieved.

[0021] Another surprising observation was that monodentate ligands advantageously were more suitable for the formation of novel catalysts, especially for the isomerization of N,N- diethylgeranylamine to citronellal enamine, and which advantageously provide superior conversion and selectivity rates compared to catalysts bearing bi- or tridentate ligands. In the course of the investigations underlying the present invention, it was found that (benzo)furyl-decorated phosphine ligands preferably showed the best results for isomerizations of double bonds. However, it should be emphasized that bi- or tridentate ligands also provide good results in the context of the present invention.

[0022] So far, phosphine ligands have only rarely been described in combination with cobalt as a coordination centre for isomerization reactions, examples of which are "Cobalt-catalyzed asymmetric hydrogenation of ketones: A remarkable additive effect on enantioselectivity", Du et al, Chinese Chemical Leters 2021 , 32, 3, 1241-1244; "Cobalt-Catalyzed, Room- Temperature Addition of Aromatic Imines to Alkynes via Directed C-H Bond Activation", Lee et al, J. Am. Chem. Soc. 2011 , 133, 43, 17283-17295; "Cobalt-Catalyzed Regioselective Carbo-amidation of Alkynes with Imides Enabled by Cleavage of C-N and C-C Bonds", Min et al., Org. Lett. 2020, 22, 3386-3391 .

[0023] No cobalt complexes with furylphosphine ligands for isomerizations of olefins have been described to date. Furthermore, only a few furylphosphine derivatives are known at all, all of which are different to the compounds of formula (I) as defined herein.

[0024] Certain furylphosphine ligands have been described in the literature in combination with noble metals, e.g. in a publication in combination with Pd as the coordination centre for use in the Stille coupling: "Large rate accelerations in the Stille reaction with tri-2-furylphosphine and triphenylarsine as palladium ligands: mechanistic and synthetic implications", J. Am. Chem. Soc. 1991 , 113, 9585-9595. The following publications describe other noble metal furylphosphine catalysts: "Rhodium catalyzed hydroboration of terminal alkynes using pinacolborane promoted by Tri(2-furyl)phosphine" Synthesis 2017, 49(12); "2- Furylphosphines as ligands for transition-metal-mediated organic synthesis", N. Andersen, B. Keay, Chem. Rev. 2001 , 101 (4), 997-1030.

[0025] For tri(benzofuran-2-yl)phosphine, however, only very few publications have been published to date. One example is the publication by C. Santelli-Rouvier, C. Coin, L. Toupet, M. Santelli, Journal of Organometallic Chemistry 1995, 495, 91-96, which only describes the complex chemistry. Significantly, only one example is known to date in which tri(benzofuran-2-yl)phosphine was used in a catalytic reaction ("A highly efficient procedure for hydroformylation and hydroamino-vinylation of methyl acrylate", M. L. Clarke and G. J. Roff, Green Chem., 2007, 9, 792-796).

[0026] Since 1980, tri(furan-2-yl)phosphine (TFP) has been used in palladium catalyzed crosscoupling reactions due to its exceptional chemical properties as a relatively poor o-donor and less bulky ligand. In many cases, the TFP ligand allows to perform cross-coupling reactions with higher selectivity and under milder reaction conditions than triphenylphosphine.

[0027] To date, furylphosphine ligands have regularly been described with noble metals, while cobalt furylphosphine complexes have been less investigated. Previous publications disclosing cobalt furylphosphine catalysts mainly used the standard tri(furan-2- yl)phosphine ligand (cf. Scheme 2, left side), which is commercially available and does not fall under the definition of the compounds of formula (I) according to the present invention. Accordingly, the new compounds of formula (I) according to the present invention, which can be used for the preparation of hitherto unknown metal catalysts, satisfy the ongoing demand for new catalysts for research and industrial applications.

[0028] T ri(benzofuran-2-yl)phosphine

[0029] Scheme 2: Chemical structures of tri(furan-2-yl)phosphine and tri(benzofuran-2- yl)phosphine

[0030] Applicant is only aware of one publication where tri(benzofuran-2-yl)phosphine is used as a ligand for rhodium catalyzed hydroformylation and hydroamino-vinylation of methyl acrylates. Furthermore, also bis-benzofuran-phosphine compounds have hardly been described in the literature. Based on the very limited number of publications on benzofuran phosphines, it was particularly surprising to find the new compounds of formula (I) according to the present invention.

[0031] In general, the coordination complexes comprising one, two, three, four or more compound(s) of formula (I) according to the present invention can be used as catalysts in catalytic reactions in the form of isolated coordination complexes (i.e. having been isolated after their synthesis) or as in situ generated coordination complexes (i.e. not having been isolated after their synthesis). From an industrial perspective, in situ generated catalysts have several advantages for large scale applications compared to the use of isolated catalysts. The production of isolated catalysts takes a considerable amount of time and leads to increased chemical waste, likewise isolated catalysts are much more unstable against atmospheric oxygen and water. In comparison, the handling of precursors and the compounds of formula (I) according to the present invention for the in situ generation of catalysts is generally less challenging (cf. the methods described further below).

[0032] According to a preferred embodiment of the present invention, the alkyl residue(s) in formula (II) is / are selected from the group consisting of methyl, ethyl, propyl, and butyl and / or the aryl residue(s) in formula (II) is / are selected from the group consisting of phenyl and benzyl. Furthermore, according to a preferred embodiment of the compound of formula (I), R1and R2are the same. According to another preferred embodiment of the compound of formula (I), R1and R2are different from one another.

[0033] A preferred embodiment according to the present invention is a compound of formula (I) as defined herein,

[0034] wherein both R1and R2are wherein both R1and R2are wherein both R1and R2are wherein both R1and R2are wherein both R1and R2are

[0035] According to another preferred embodiment of the present invention, the compound of formula (I) as defined herein is selected from the group consisting of

[0036]

[0037] The compound(s) of formula (I) as defined above are particularly advantageous in the context of the present invention as they give high conversion rates in catalytic reactions when used as ligands in coordination complexes according to the present invention.

[0038] What has been stated herein for the compounds of formula (I) according to the invention applies accordingly to the compounds of formula (IV) according to the invention (cf. further below).

[0039] According to a second aspect of the present invention, the stated object is achieved by a coordination complex comprising one, two, three, four or more compound(s) of formula (I) and / or (IV) as defined herein (cf. further below for the compounds of formula (IV)) as ligand(s), preferably as monodentate or bidentate ligand(s).

[0040] The inventors of the present invention surprisingly were able to create a broad library of new coordination complexes, in particular in situ generated coordination complexes, with the compounds of formula (I) and / or (IV) according to the present invention as ligands. For methods for producing the coordination complexes according to the present invention see further below.

[0041] According to one embodiment, in a coordination complex according to the invention all of the compounds of formula (I) and / or (IV) according to the invention contained therein are bound to the coordination centre in the form of monodentate ligands.

[0042] According to another embodiment, in a coordination complex according to the invention all of the compounds of formula (I) and / or (IV) according to the invention contained therein are bound to the coordination centre in the form of bidentate ligands.

[0043] According to another embodiment, in a coordination complex according to the invention one or more of the compounds of formula (I) and / or (IV) according to the invention contained therein are bound to the coordination centre in the form of monodentate ligands while the remaining compounds of formula (I) and / or (IV) according to the invention contained therein are bound to the coordination centre in the form of bidentate ligands or vice versa.

[0044] A preferred embodiment according to the present invention is a coordination complex as defined herein, wherein the coordination centre is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel atom or is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel ion or is a 3d transition metal atom or ion, preferably wherein the coordination centre is a manganese, iron, cobalt, or nickel atom or a manganese, iron, cobalt, or nickel ion, more preferably wherein the coordination centre is a cobalt atom or ion.

[0045] Surprisingly, it has been found that a range of 3d, 4d and 5d transition metal atoms or ions can be used to produce the coordination complexes according to the present invention.

[0046] Most preferably, the coordination centre is a Co(lll) ion, a Co(ll) ion, a Co(l) ion or a Co(0) atom.

[0047] Even more surprisingly, it was found that the inclusion of cobalt atoms or ions into the coordination complexes according to the present invention allows the creation of a range of new cobalt catalysts that are particularly suitable for hydrogen transfer reactions such as isomerization reactions.

[0048] According to another aspect of the present invention, the stated object is achieved by a method for producing a compound of formula (I) as defined herein comprising or consisting of the following steps: a) Providing furan or a furan derivative, preferably wherein the furan derivative is selected from the group consisting of 2,3-dimethylfuran, benzofuran, 3- bromobenzofuran, 5-bromobenzofuran, 7-bromobenzofuran, 3-methylbenzofuran, benzo[1 ,2-b:4,5-b']difuran, 2-bromoanisol, (1 ,3-dioxolan-2-yl)tri-n-butylstannane, and dibenzofuran, b) performing a lithiation reaction on the furan or furan derivative provided in step a) with a lithiation reagent, preferably wherein the lithiation reagent is selected from the group consisting of n-butyllithium, sec-butyllithium, and te / Y-butyllithium, to obtain a lithiated species of the furan or furan derivative, c) reacting the lithiated species of the furan or furan derivative obtained in step b) with phosphorus trichloride or with a compound according to formula (III)

[0049] (HI), wherein R1is a residue independently selected from the group consisting of or R1is a residue according to formula (II) wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4, preferably a benzene ring, and / or R4forms an aromatic ring with R5, preferably a benzene ring, preferably wherein R1is a residue independently selected from the group consisting of

[0050] A preferred embodiment according to the present invention is a method as defined herein, wherein the lithiation reaction in step b) is performed under a argon atmosphere and / or at temperatures in the range of from 0 °C to -80 °C, preferably in the range of from -20 °C to -80 °C, preferably at -78 °C.

[0051] Within the framework of the present text, 1 ,3-dioxolan-2-yl)tri-n-butylstannane and 2- bromoanisole are considered to be furan derivatives.

[0052] Surprisingly, it has been found that the method(s) as defined herein is / are particularly advantageous for the synthesis of the compounds of formula (I) according to the present invention.

[0053] A preferred embodiment according to the present invention, and especially of this aspect of the present invention, is a method for producing a compound of formula (I) as defined herein, wherein the compound of formula (I) that is produced is selected from the group consisting of

[0054]

[0055] Another aspect of the present invention is a method for producing a compound of formula (I) as defined herein comprising or consisting of the following steps: a) Providing a compound according to formula (III)

[0056] (HI), wherein R1is a residue independently selected from the group consisting of or R1is a residue according to formula (II) wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4, preferably a benzene ring, and / or R4forms an aromatic ring with R5, preferably a benzene ring, preferably wherein R1is selected from the group consisting of and b) reacting the compound provided in step a) with a hthiated compound, preferably wherein the lithiation compound is selected from the group consisting of isobutyllithium, methyllithium, and phenyllithium.

[0057] A preferred embodiment according to the present invention, and especially of this aspect of the present invention, is a method for producing a compound of formula (I) as defined herein, wherein the compound of formula (I) that is produced is selected from the group consisting of

[0058] Another aspect of the present invention is a method for producing a compound of formula (I) as defined herein comprising or consisting of the following steps: a) Providing a compound according to formula (III) wherein R1is a residue independently selected from the group consisting of

[0059] or R1is a residue according to formula (II) wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4, preferably a benzene ring, and / or R4forms an aromatic ring with R5, preferably a benzene ring, preferably wherein and b) reacting the compound provided in step a) with an alkoxide, preferably with an ethoxide, more preferably with sodium ethoxide. According to a preferred embodiment of the present invention, a method for producing a compound of formula (I) as defined herein comprises the following further and optional step:

[0060] Purification of the compound(s) of formula (I) obtained in step b) or c) - as applicable - by crystallization and / or by (high) vacuum distillation.

[0061] A preferred embodiment according to the present invention, and especially of this aspect of the present invention, is a method for producing a compound of formula (I) as defined herein, wherein the compound of formula (I) that is produced is

[0062] According to another aspect of the present invention, the stated object is achieved by a method for producing a compound of formula (I) as defined herein comprising or consisting of the following steps: a) Providing an alkyl halogenide, preferably wherein the alkyl halogenide is selected from the group consisting of ethylbromide, n-propylbromide, and neo-pentylbromide, b) reacting the alkyl halogenide provided in step a) with magnesium in a solvent, preferably wherein the solvent is diethyl ether, c) cooling the reaction mixture obtained in step b) to a temperature in the range of from 0 to -100 °C, preferably of from 0 to -90 °C, more preferably of from -70 to -90 °C, most preferably to -78°C, d) reacting the cooled reaction mixture obtained in step c) with a compound according to formula (III) or (V), (Ill) wherein R1is a residue independently selected from the group consisting of or R1is a residue according to formula (II) wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4, preferably a benzene ring, and / or R4forms an aromatic ring with R5, preferably a benzene ring, preferably wherein R1is a residue independently selected from the group consisting of preferably wherein in case R1is , the alkylhalogenide is not methylhalogenide, n- butylhalogenide or te / Y-butylhalogenide.

[0063] Surprisingly, it has been found that the method(s) as defined herein is / are particularly advantageous for the synthesis of the compounds of formula (I) according to the present invention.

[0064] Preferably, the magnesium reacted in step b) is in the form of powder or turnings and is essentially free of water. Furthermore, it is particularly advantageous to perform the method described above under a protective gas atmosphere.

[0065] A preferred embodiment according to the present invention, and especially of this aspect of the present invention, is a method for producing a compound of formula (I) as defined herein, wherein the compound of formula (I) that is produced is selected from the group consisting of

[0066] According to another aspect of the present invention, the stated object is achieved by using a compound of formula (I) and / or (IV) as defined herein or as obtained according to a method as defined herein for producing a coordination complex, preferably a coordination complex as defined herein.

[0067] According to a further aspect of the present invention, the stated object is achieved by a method for producing a coordination complex, preferably as defined herein, comprising or consisting of the following steps: a) Providing a precursor coordination complex, wherein the coordination centre of the precursor coordination complex is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel atom or is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel ion or is a 3d transition metal atom or ion, preferably wherein the coordination centre is a manganese, iron, cobalt, or nickel atom or a manganese, iron, cobalt, or nickel ion, more preferably wherein the coordination centre is a cobalt atom or ion, more preferably wherein the precursor coordination complex is a cobalt(ll) or cobalt (III) salt, most preferably wherein the precursor coordination complex is selected from the group consisting of cobalt(ll) acetylacetonate, cobalt(lll) acetylacetonate, cobalt(ll) acetate, cobalt(ll) naphthenate, cobalt(ll) benzoate, cobalt(ll) 2-ethylhexanoate, cobalt(ll) chloride, cobalt(ll) bromide, cobalt(ll) trifluoromethanesulfonate, cobalt(ll) dibromo(1 ,2- dimethoxyethane) , cobalt (II) 2,2,6,6-tetramethyl-3,5-heptanedionate, cobalt (II) hexafluoroacetylacetonate and cobalt (II) trifluoroacetylacetonate, b) providing one or more compound(s) of formula (I) and / or (IV) as defined herein (cf. further below for the compound of formula (IV)), preferably obtained according to a method as defined herein, c) producing a solution or suspension comprising the precursor coordination complex provided in step a), the compound(s) of formula (I) and / or (IV) provided in step b), and one or more solvent(s), preferably one or more non-polar solvent(s), more preferably wherein the one or more solvent(s) is / are selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, toluene, cyclohexane, benzene, xylene, dibutyl ether, dioxane, hexane, and heptane, d) adding, preferably dropwise or portionwise, one or more reducing agent(s) to the solution produced in step c), preferably wherein the one or more reducing agent(s) is / are selected from the group consisting of diisobutylaluminium hydride (DIBAL), triethylaluminium, diisobutylaluminium hydride-tetrahydrofuran-solution, diisobutylaluminium hydride-toluene-solution, aluminium hydride (alane), N,N- dimethylethylamine complex, lithium diisobutyl-tert-butoxyaluminium hydride, lithium aluminium hydride, sodium borohydride, and sodium triethylborohydride, e) optionally, isolating the one or more coordination complex(es) formed in step d) from the reaction mixture.

[0068] Preferably, the solvents used in step c) are anhydrous solvents. Preferably, the one or more coordination complex(es) according to the invention is / are generated in situ by method steps a) to d) as defined herein and immediately used as catalyst(s) without any further purification or isolation steps.

[0069] If the precursor coordination complex provided in step a) and / orthe compound(s) of formula (I) and / or (IV) provided in step b) of the method as defined herein is / are already dissolved in or mixed with one or more solvent(s), preferably one or more non-polar solvent(s), more preferably one or more solvent(s) selected from the group consisting of tetrahydrofuran, 2- methyltetrahydrofuran, toluene, cyclohexane, benzene, xylene, dibutyl ether, dioxane, hexane and heptane, then step c) of the method as defined herein may only encompass the mixing of said components to produce a solution or suspension as defined in step c).

[0070] Preferably, at least steps c) and d) of the method as defined herein are carried out under an inert gas, preferably an argon, atmosphere. More preferably, steps a) to d) or steps a) to e), if step e) is present, are carried out under an inert gas, preferably an argon, atmosphere.

[0071] Preferably, the precursor coordination complex provided in step a) and the compound(s) of formula (I) and / or (IV) provided in step b) are mixed together in solid form, preferably under an inert gas, more preferably an argon, atmosphere, before the one or more solvent(s) (as defined herein) are added in step c) of the method as defined herein.

[0072] According to a preferred embodiment of the present invention, the molar ratio of the precursor coordination complex to the compound(s) of formula (I) and / or (IV) in the solution or suspension produced in step c) is in a range of from 0.1 to 10, preferably from 0.5 to 5, more preferably from 1 to 3.

[0073] The molar ratio of the precursor coordination complex to the compound(s) of formula (I) and / or (IV) as defined herein refers the number of coordination centres of the precursor coordination complex to the number of compounds of formula (I) and / or (IV) present in the solution or suspension produced in step c).

[0074] According to a further preferred embodiment of the present invention, the concentration of the precursor coordination complex in the solution or suspension produced in step c) is in a range of from 0.01 to 0.5 mol%, preferably from 0.05 to 0.1 mol%.

[0075] According to another preferred embodiment of the present invention, the concentration of the compound(s) of formula (I) and / or (IV) in the solution or suspension produced in step c) is in a range of from 0.1 to 5 mol%, preferably from 0.5 to 3 mol%, more preferably from 1 to 3 mol%.

[0076] According to a preferred embodiment of the present invention, the concentration of the reducing agent in the reaction mixture obtained in step d) is in a range of from 0.1 to 4 mol%, preferably from 0.5 to 3 mol%, more preferably from 1 to 2 mol%.

[0077] According to another preferred embodiment of the present invention, step d) is carried out at a temperature in the range of from 0 to 150 °C, preferably in the range of from 15 to 125 °C, more preferably in the range of from 25 to 120 °C.

[0078] New in situ generated coordination complexes according to the invention comprising, for instance, a cobalt atom or ion as a coordination centre can be generated from a cobalt precursor complex, for example a cobalt(ll) salt or a cobalt(lll) salt as described in step a) of the method according to the invention. The in situ generated coordination complexes according to the present invention comprising a cobalt atom or ion as a coordination centre can be generated, for instance, by the addition of a reducing agent to the cobalt(ll) or cobalt(lll) precursor in the presence of one or more compound(s) of formula (I) and / or (IV) according to the present invention, which preferably initially generates coordination complexes according to the invention with Co(l) as a coordination centre (cf. step d) of the method). This / these Co(l) species may further react to form coordination complexes according to the invention with Co(0) as a coordination centre.

[0079] Only two cobalt catalysts that were able to catalyze the isomerisation of N,N- diethylgeranylamine to citronellal-enamine have been reported by Noyori et al. in 1978, the cobalt nitrogen complex HCo(N)2(PPfi3)3 and a cobalt in situ system obtained from a cobalt(ll) salt with AIEts or DIBAL-H as reducing agent and triphenylphosphine (with the ratio 1 :3:3). In contrast to the above described rhodium catalyst from Takasago, these cobalt catalysts show significantly lower activity and regioselectivity for the isomerisation of / V, / V-diethylgeranylamine to citronellal-enamine (85% yield). In addition, the required high catalyst loading is a major disadvantage for an industrial application of these cobalt catalysts.

[0080] Moreover, literature-known earth-abundant transition metal catalysts, that are suitable for isomerization reactions, often suffer from elaborate ligand synthesis procedures, which include several synthesis steps. In addition, these earth-abundant transition metal catalysts usually have higher substrate limitations compared to noble metal catalysts. Thus, the method for producing a coordination complex according to the present invention is particularly advantageous for overcoming these issues.

[0081] Catalytic test reactions carried out during the studies underlying the present invention revealed that active coordination complexes according to the invention with Co(l) as a coordination centre are formed in the presence of one as well as two or three equivalents of the compound(s) of formula (I) and / or (IV) according to the invention during step d) of the method, whereby the presence of more than three equivalents of the compound(s) of formula (I) and / or (IV) in step d) of the method may in a few cases lead to a deactivation of the coordination complexes. The low required molar ratio of the compound(s) of formula (I) and / or (IV) to the cobalt precursor coordination complex is a major advantage of the in situ generated coordination complexes according to the present invention in terms of industrial application, because in situ systems often use high molar ratios of phosphine ligands.

[0082] Interestingly, it was observed in crystallisation experiments that the in situ generated coordination complexes according to the invention with Co(l) as a coordination centre can disproportionate, preferably forming coordination complexes according to the invention with Co(0) as a coordination centre with four coordinating compounds of formula (I) and / or (IV) as defined herein as ligands.

[0083] Advantageously, the in situ generated coordination complexes according to the invention with Co atoms or ions, preferably Co(0) or Co(l), as coordination centres are highly active catalysts. Several different active species of the coordination complexes according to the invention may be formed in solution by the method according to the invention. One, two, three, four or more further ligand(s) selected from the group consisting of H, solvent molecules and ligands of the precursor coordination complex can optionally also be bound to the coordination centres of the coordination complexes obtained by the method according to the invention by one, two or more coordinative bond(s), respectively.

[0084] According to another aspect of the present invention, the stated object is achieved by using a coordination complex as defined herein or by using a coordination complex obtained according to a method as defined herein as a catalyst, preferably in a hydrogen transfer reaction, more preferably for the isomerization of a double bond in a substrate.

[0085] Thus, preferably, the isomerization of a double bond in a substrate according to the present invention is a regio-selective isomerization of said double bond. Another preferred embodiment of the present invention is a use as defined herein, wherein the substrate to be isomerized comprises one, two or more double bonds, preferably wherein only one of the double bonds is (regio-)isomerized.

[0086] When a substrate comprises two or more double bonds, it is particularly challenging to selectively manipulate the position of only one of the double bonds in the molecule by catalytic reaction. Advantageously, the coordination complexes according to the present invention enable the catalysis of (regio-)isomerization reactions, wherein the position of only one of the double bonds in a substrate comprising two or more double bonds is selectively changed (cf. below for further details).

[0087] A further preferred embodiment of the present invention is a use as defined herein, wherein the substrate to be isomerized further comprises one or more heteroatom(s), preferably further comprises one or more nitrogen atom(s).

[0088] Furthermore, a preferred embodiment of the present invention is a use as defined herein, wherein the substrate to be isomerized is selected from the group consisting of N,N- dimethylgeranylamine, / , / V-diethylgeranylamine, 1 -[3,7-dimethylocta-2,6- dienyl]pyrrolidine, 4-[3,7-dimethylocta-2,6-dienyl]morpholine, / V, / V-diphenylgeranylamine, / V, / V-diethyl-3-methylbut-2-en-1 -amine, / V, / V-diethyl-3-methylhept-2-en-1 -amine, / V, / V- diethylhex-2-en-1 -amine, 3-cyclohexyl- / V, / V-diethylprop-2-en-1 -amine, / V, / V-diethyl-4,4,4- trifluorobut-2-en-1 -amine, / V, / V-diethyl-2-methylbut-2-en-1 -amine, / V, / V-diethyl-prop-2-en-1- amine, / V, / V-diethyl-but-3-en-1 -amine, / V, / V-diethyl-pent-4-en-1 -amine, A / -[(cyclohex-1-en-

[0089] 1-yl)methyl]- / V-ethylethanamine, / V, / V-diethyl-3-phenylprop-2-en-1 -amine, 3-(4- chlorophenyl)- / V, / V-diethylprop-2-en-1 -amine, 3-(4-trifluoromethylphenyl)-A / ,A / -diethylprop-

[0090] 2-en-1 -amine, 3-(4-methoxyphenyl)-A / ,A / -diethylprop-2-en-1 -amine, 3-(4-te / Y-butylphenyl)- / V, / V-diethylprop-2-en-1 -amine, 3-(4-cyanophenyl)- / V, / V-diethylprop-2-en-1 -amine, / V, N- diethyl-3-phenylbut-2-en-1 -amine, / V, / V-diethyl-3-(4-fluorophenyl)-3-phenylprop-2-en-1- amine, / V, / V-diethyl-3-(1 ,3,5-trimethylphenyl)-3-phenylprop-2-en-1-amine, and (2E,2’E)- 3,3’-(1 ,4-phenylene)bis(N,N-diethylprop-2-en-1 -amine), preferably wherein the substrate to be isomerized is / V, / V-diethylgeranylamine

[0091] The use as defined herein is particularly advantageous for the isomerization of the substrates as defined herein.

[0092] According to another aspect of the present invention, the stated object is achieved by a method, preferably hydrogen transfer reaction, more preferably for the (regio-)isomerization of a double bond in a substrate, comprising or consisting of the following steps: a) Providing a coordination complex as defined herein or a coordination complex obtained according to a method as defined herein, b) providing a substrate to be isomerized, preferably wherein the substrate to be isomerized comprises one, two or more double bonds, c) contacting the coordination complex provided in step a) with the substrate provided in step b), and d) carrying out an isomerization reaction on the substrate catalyzed by the coordination complex.

[0093] Preferably, the substrate to be isomerized provided in step b) comprises two or more double bonds.

[0094] More preferably, the substrate to be isomerized provided in step b) comprises two or more double bonds and by applying the steps of the method according to the invention only one of the double bonds in the substrate is (regio-)isomerized while the position of the other double bond(s) remains unchanged.

[0095] Preferably, the solvent (if present) used in the method as defined herein, more preferably used in step d) of the method, is selected from the group consisting of tetrahydrofuran, 2- methyltetrahydrofuran, toluene, cyclohexane, benzene, xylene, dibutyl ether, dioxane, hexane, and heptane.

[0096] A further preferred embodiment of the present invention is a method as defined herein, wherein the substrate provided in step b) comprises one or more heteroatom(s), preferably comprises one or more nitrogen atom(s), most preferably wherein the substrate provided in step b) is selected from the group consisting of A / ,A / -dimethylgeranylamine, N,N- diethylgeranylamine, 1-[3,7-dimethylocta-2,6-dienyl]pyrrolidine, 4-[3,7-dimethylocta-2,6- dienyl]morpholine, N, AAdiphenylgeranylamine, A / , A / -diethyl-3-methylbut-2-en-1 -amine, / V, / V-diethyl-3-methylhept-2-en-1 -amine, / V, / V-diethylhex-2-en-1 -amine, 3-cyclohexyl-A / ,A / - diethylprop-2-en-1 -amine, A / , A / -diethyl-4,4,4-trifluorobut-2-en-1 -amine, N, A / -d iethy I-2- methylbut-2-en-1 -amine, / V, / V-diethyl-prop-2-en-1 -amine, / V, / V-diethyl-but-3-en-1 -amine, / V, / V-diethyl-pent-4-en-1 -amine, A / -[(cyclohex-1-en-1-yl)methyl]-A / -ethylethanamine, A / , A / - d iethy l-3-ph e ny I pro p-2-en- 1 -amine, 3-(4-chlorophenyl)- / V, / V-diethylprop-2-en-1 -amine, 3- (4-trifluoromethylphenyl)- / V, / V-diethylprop-2-en-1 -amine, 3-(4-methoxyphenyl)-A / ,A / - diethylprop-2-en-1 -amine, 3-(4-te / Y-butylphenyl)- / V, / V-diethylprop-2-en-1 -amine, 3-(4- cyanophenyl)- / V, / V-diethylprop-2-en-1 -amine, A / , / V-diethyl-3-phenylbut-2-en-1 -amine, / V, / V- diethyl-3-(4-fluorophenyl)-3-phenylprop-2-en-1 -amine, N, A / -d iethy l-3-(1 ,3,5- trimethylphenyl)-3-phenylprop-2-en-1 -amine, and (2E,2’E)-3,3’-(1 ,4-phenylene)bis(N,N- diethylprop-2-en-1 -amine).

[0097] Most preferably, the substrate provided in step b) is / V, / V-diethylgeranylamine.

[0098] Advantageously, the coordination complexes according to the present invention can be used for the selective (regio-)isomerisation of one of the double bonds of N,N- diethylgeranylamine.

[0099] According to another aspect of the present invention, the stated object is achieved by a compound of formula (IV) , wherein R1is a residue independently selected from the group consisting of

[0100] wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, and wherein R2is a residue selected from the group consisting of

[0101] or R2is a residue according to formula (II) wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, and preferably wherein

[0102] What has been stated herein for the compounds of formula (I) according to the invention applies accordingly to the compounds of formula (IV) according to the invention.

[0103] A preferred embodiment according to the present invention is a compound of formula (IV) as defined herein, wherein

[0104] According to another preferred embodiment of the present invention, the compound of formula (IV) as defined herein is

[0105] According to another aspect of the present invention, the stated object is achieved by a method for producing a compound of formula (IV) as defined herein comprising or consisting of the following steps: a) Providing a compound of formula (I) (or producing a compound of formula (I) according to any one of the methods as described herein)

[0106] (I), wherein R1is a residue independently selected from the group consisting of or R1is a residue according to formula (II) wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, and wherein R2is a residue selected from the group consisting of wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, preferably wherein b) reacting the compound of formula (I) provided (or produced) in step a) with hydrogen peroxide in a solvent, preferably in dichloromethane.

[0107] Surprisingly, it has been found that the method(s) as defined herein is / are particularly advantageous for the synthesis of the compounds of formula (IV) according to the present invention.

[0108] A preferred embodiment according to the present invention, and especially of this aspect of the present invention, is a method for producing a compound of formula (IV) as defined herein, wherein the compound of formula (IV) that is produced is selected from the group consisting of

[0109] (Preferred) embodiments of the compounds of formula (I) according to the invention correspond to or can be derived from the (preferred) embodiments of the coordination complexes according to the invention which are explained above or vice versa. (Preferred) embodiments of the compounds of formula (I) or coordination complexes according to the invention correspond to or can be derived from the (preferred) embodiments of the methods according to the invention which are explained above or vice versa. (Preferred) embodiments of the compounds of formula (I) or coordination complexes according to the invention correspond to or can be derived from the (preferred) embodiments of the uses according to the invention which are explained above or vice versa. (Preferred) embodiments of the compounds of formula (I) according to the invention correspond to or can be derived from the (preferred) embodiments of the compounds of formula (IV) according to the invention which are explained above or vice versa. Moreover, the (preferred) embodiments described herein can be arbitrarily combined with each other as long as technically sensible.

[0110] The invention will now be described in more detail hereinafter with references to the examples. Further aspects of the present invention are disclosed in the accompanying claims.

[0111] Examples:

[0112] I. Synthesis of the compounds of formula (I) according to the invention

[0113] 1.1 Synthesis of tris(4,5-dimethylfuran-2-yl)phosphine

[0114] Under argon atmosphere, 2,3-dimethylfuran (787 mg, 8.19 mmol, 3 eq.) was weighted in a flame dried Schlenk flask. Then, 20 mL anhydrous diethyl ether was added, and the solution was cooled to -78°C. Under stirring, n-Buli (2.5 M, 3.3 mL, 8.19 mmol, 3 eq.) was slowly added with a syringe and the temperature was kept for 1 h at -78 °C. Afterwards, the reaction mixture was allowed to warm up to room temperature and stirred for 2 h. Then, the lithiated dimethylfuran solution was cooled again to -78 °C and phosphorus trichloride (375 mg, 2.73 mmol, 1 eq.) was slowly added with a syringe. The solution was warmed up to room temperature and stirred overnight. To remove the lithium chloride, the orange / brown suspension was filtrated with a syringe filter. Next, the solvent was removed in vacuo, which yielded an orange oil. Finally, a colourless oil (1.41 g, 5.58 mmol, q (yield): 82%) was obtained by high vacuum distillation.1H-NMR (400 MHz, THF) 6 = 6.44 (dt, J=0.9, 0.4, 3H), 2.17 (s, 9H), 1 .88 (s, 9H).

[0115] 13C-NMR (101 MHz, THF) 6 = 152.83 (d, J=3.4), 147.49 (d, J=3.5), 124.15 (d, J=19.3), 115.93 (d, J=5.0), 1 1.39, 9.52.

[0116] 31P-NMR (162 MHz, THF) 6 = -76.01 .

[0117] HRMS (ESI): m / z calcd. for C18H21O3P: 317.1306 [M+H]+, found: 317.1306.

[0118] 1.11 Synthesis of bis(furan-2-yl)(isobutyl)phosphine

[0119] Under argon atmosphere, bis(2-furyl)-phosphine chloride (0.55 g, 2.74 mmol, 1 eq.) was weighted in a flame dried Schlenk flask. Then, 15 mL anhydrous diethyl ether were added and the solution was cooled to -78 °C. Isobutyllithium (1.7 M, 1.61 mL, 2.74 mmol, 1 eq.) was slowly transferred to the stirring solution and the temperature was kept at -78 °C for 1 h. The reaction mixture was allowed to warm up to room temperature and stirred overnight. Afterwards, the lithium chloride was removed from the reaction mixture by anaerobic filtration with a syringe filter, the solvent was removed in vacuo. Finally, the received yellow oil was purified by vacuum distillation, which yielded the target product as a colourless oil (0.49 g, 2.21 mmol, q: 81 %).

[0120] 1H-NMR (400 MHz, THF) 6 = 7.66 (dd, J = 1 .9, 0.8, 2H), 6.85 - 6.54 (m, 2H), 6.53 - 6.13 (m, 2H), 2.09 (d, J = 7.0, 2H), 1.61 (ddp, J = 13.5, 9.5, 6.7, 1 H), 0.97 (d, J = 6.7, 6H).

[0121] 13C-NMR (101 MHz, THF) 6 = 153.01 (d, J=17.0), 147.52 (d, J=1 .8), 120.13 (d, J=24.2), 111 .00 (d, J=5.5), 35.89 (d, J=2.6), 26.84 (d, J=14.4), 23.93 (d, J=9.9).

[0122] 31P-NMR (162 MHz, THF) 6 = -64.88.

[0123] HRMS (ESI): m / z calcd. for C12H15O2P: 223.0888 [M+H]+, found: 223.0884.

[0124] 1.111 Synthesis of ethoxydi(furan-2-yl)phosphine

[0125] A flame dried Schlenk flask was charged with sodium ethoxide (0.39 g, 5.76 mmol, 1.05 eq.) and 10 mL anhydrous THF. In another Schlenk flask, bis(2-furyl)-phosphine chloride (1.10 g, 5.48 mmol, 1 eq.) was dissolved in 10 ml anhydrous THF. At -20 °C, the sodium ethoxide solution was added dropwise to the bis(2-furyl)-phosphine chloride solution and the resulting reaction mixture was then allowed to stir at same temperature for 1 h. After the solution was warmed up to room temperature, the solvent was removed in vacuo. Finally, the obtained oil was purified by vacuum distillation, which yielded the target product as a colourless oil (0.75 g, 3.56 mmol, q: 65%).

[0126] 1H-NMR (400 MHz, THF) 6 = 7.78 (dd, J=1 .7, 0.7, 2H), 6.92 - 6.78 (m, 2H), 6.47 (dt, J=3.2, 1 .6, 2H), 3.79 - 3.72 (m, 2H), 1 .08 - 1 .04 (m, 3H).

[0127] 13C-NMR (101 MHz, THF) 6 = 155.44 (d, J=23.4), 148.20 (d, J=3.4), 121.75 (d, J=23.3), 111 .01 (d, J=4.9), 65.31 , 16.84 (d, J=5.0).

[0128] 31P-NMR (162 MHz, THF) 6 = 55.63. 2.

[0129] A flame dried Schlenk flask was charged with benzofuran (0.99 g, 8.42 mmol, 1 eq.) and 10 mL anhydrous diethyl ether. At -20 °C, n-BuLi (2.5 M, 3.37 mL, 8.42 mmol, 1 eq.) was added dropwise to the solution and the temperature was kept for 1 h. Then, the reaction mixture was allowed to slowly warm up to room temperature and stirred for 2 h. Bis(2-furyl)- phosphine chloride (1.69 g, 8.42 mmol, 1 eq.) was weighted in a separate Schlenk flask and was dissolved in 15 mL anhydrous diethyl ether. The lithiated benzofuran solution was transferred into a Schlenk dropping funnel and the orange solution was slowly added to the phosphine chloride at -78 °C. After complete addition of the benzofuran solution, the reaction mixture was warmed up to room temperature. Next, the lithium chloride was removed from the reaction mixture by anaerobic filtration with a syringe filter and the solvent was removed in vacuo. Then, a vacuum distillation of the crude oil was performed, yielding a colourless oil (1 .86 g, 6.59 mmol, q: 78%) as the desired product. The received oil started crystallising after the distillation was finished.

[0130] 1H-NMR (400 MHz, THF) 6 = 7.76 (dt, J = 1 .9, 0.9, 2H), 7.57 - 7.51 (m, 1 H), 7.45 (dd, J = 8.3, 1.0, 1 H), 7.26 (ddd, J = 8.3, 7.2, 1.4, 1 H), 7.17 (td, J = 7.5, 1.1 , 1 H), 7.00 (t, J = 1.1 , 1 H), 6.93 - 6.88 (m, 2H), 6.47 (dt, J = 3.4, 1 .7, 2H).

[0131] 13C-NMR (101 MHz, THF) 6 = 158.70 (d, J=3.9), 154.15, 148.84 (d, J=2.5), 148.73 (d, J=2.8), 128.87 (d, J=4.6), 125.67, 123.42, 122.46 (d, J=24.2), 121 .78, 1 16.79 (d, J=18.0), 111 .85, 111.48 (d, J=6.2).

[0132] 31P-NMR (122 MHz, THF) 6 = -73.92.

[0133] HRMS (ESI): m / z calcd. for C16H11O3P: 305.0338 [M+Na]+, found: 305.0335.

[0134] I.V Synthesis of tri(benzofuran-3-yl)phosphine

[0135] Under argon atmosphere, 3-bromobenzofuran (450 mg, 2.28 mmol, 3 eq.) was weighted in a flame dried Schlenk flask. Then, 12 mL anhydrous diethyl ether were added, and the solution was cooled to -78 °C. Next, n-BuLi (2.5 M, 1 ml, 2.50 mmol, 3.3 eq.) was added dropwise to the solution, which resulted in a fast colour change to yellow. After stirring the solution for 1 h at -78 °C, phosphorus trichloride (104 mg, 0.76 mmol, 1 eq.) was added slowly. The reaction mixture was allowed to warm up to room temperature and stirred overnight. A light-yellow solution was obtained after the suspension was filtrated. The solvent was removed in vacuo, whereby a yellow solid was obtained. The desired product was isolated by column chromatography using n-hexane and 1 % ethyl acetate as eluents. After the solvent was removed in vacuo, a light-yellow solid was obtained (226 mg, 0.59 mmol, r|: 78%). The phosphine was stored under argon.

[0136] 1H-NMR (400 MHz, THF) 6 = 7.70 (d, J=1 .5, 1 H), 7.59 - 7.54 (m, 1 H), 7.52 (dq, J=8.3, 1.1 , 1 H), 7.29 (ddd, J=8.3, 7.2, 1 .3, 1 H), 7.19 - 7.13 (m, 1 H).

[0137] 13C-NMR (101 MHz, THF) 6 = 156.30 (d, J=5.4), 149.51 (d, J=19.0), 128.88 (d, J=15.3), 124.67, 122.88, 120.84 (d, J=2.6), 111.36, 111.28.

[0138] 31P-NMR (122 MHz, THF) 6 = -86.33.

[0139] HRMS (ESI): m / z calcd. for C24H15O3P: 383.0837 [M+H]+, found: 383.0828.

[0140] I. VI Synthesis of tri(benzofuran-5-yl)phosphine

[0141] First, 5-bromobenzofuran (520 mg, 2.64 mmol, 3 eq.) was dissolved in 15 mL of anhydrous diethyl ether in a flame dried Schlenk flask. At -78 °C, t-BuLi (2.73 mmol, 3.1 eq.) was added slowly to the solution and the reaction mixture was kept for 1 h at this temperature. Then, phosphorus trichloride (121 mg, 0.88 mmol, 1 eq.) was added dropwise to the lithiated benzofuran compound at -78 °C. After warming up to room temperature, the white suspension was filtrated with a syringe filter to remove the lithium chloride, yielding a colourless solution. Next, the solvent was removed under reduced pressure and a white solid was received. Crystallization of the target phosphine was achieved by a concentrated dichloromethane (DCM) solution yielding colourless platelets. Finally, the obtained crystals were dried under reduced pressure overnight (180 mg, 0.47 mmol, q: 53%).

[0142] 1H-NMR (400 MHz, THF) 6 = 7.74 (d, J = 2.2, 1 H), 7.53 (dd, J = 7.3, 1 .7, 1 H), 7.51 - 7.45

[0143] (m, 1 H), 7.33 - 7.24 (m, 1 H), 6.76 (dd, J = 2.3, 1 .0, 1 H).13C-NMR (101 MHz, THF) 6 = 156.21 , 146.51 , 133.10 (d, J=11 .7), 130.55 (d, J=24.1), 128.96 (d, J=8.1), 127.51 (d, J=20.6), 11 1.96 (d, J=8.4), 107.19.

[0144] 31P-NMR (122 MHz, THF) 6 = -3.79.

[0145] HRMS (ESI): m / z calcd. for C24H15O3P: 383.0837 [M+H]+, found: 383.0836.

[0146] I.VII Synthesis of tri(benzofuran-7-yl)phosphine

[0147] First, 7-bromobenzofuran (1 .00 g, 5.07 mmol, 3 eq.) was weighted in a flame dried Schlenk flask. Then, 10 mL anhydrous diethyl ether were added and the solution was cooled to -78 °C, followed by the slow addition of n-BuLi (5.07 mmol, 3 eq.). After the reaction mixture stirred for approximately 2 h at -78 °C, phosphorus trichloride (0.23 g, 1.69 mmol, 1 eq.) was transferred dropwise to the lithiated benzofuran compound. The solution was allowed to slowly warm up to room temperature. Next, the suspension was filtrated with a syringe filter and a colourless solution was obtained. Then, the solvent was removed under vacuum, yielding a white solid. Finally, crystals of the target product (401 mg, 1 .05 mmol, q: 62%) were obtained from a concentrated dichloromethane phosphine solution at -30 °C.

[0148] 1H-NMR (400 MHz, THF) 6 = 7.67 (d, J=2.2, 3H), 7.61 (dd, J=7.7, 1.2, 3H), 7.08 (ddd, J=7.8, 7.4, 0.5, 3H), 6.83 (t, J=2.2, 3H), 6.80 - 6.74 (m, 3H).

[0149] 13C-NMR (101 MHz, THF) 6 = 157.98 (d, J=17.6), 146.17, 129.64 (d, J=3.6), 127.93 (d, J=2.8), 123.70 (d, J=1 .5), 122.83, 118.52 (d, J=16.9), 106.96 (d, J=1 .8).

[0150] 31P-NMR (162 MHz, THF) 6 = -44.82.

[0151] HRMS (ESI): m / z calcd. for C24H15O3P: 405.0651 [M+Na]+, found: 405.0649. I. VI 11 Synthesis of tris(3-methylbenzofuran-2-yl)phosphine

[0152] Under argon atmosphere, 3-methylbenzofuran (1.05 g, 7.91 mmol, 3.1 eq.) was dissolved in 20 mL of anhydrous diethyl ether. Then, n-BuLi (2.5 mM, 3.16 mL, 7.91 mmol, 3.1 eq.) was added slowly to the solution at -78 °C. The reaction mixture was kept at -78 °C for 1 h, before the solution was warmed up to room temperature. The solution stirred 2 h at room temperature. At -78 °C, phosphorus trichloride (0.35 g, 2.55 mmol, 1 eq.) was added dropwise to the lithiated benzofuran compound. After that, the solution was allowed to slowly warm up to room temperature and a white suspension was obtained, which was filtrated with a syringe filter to remove the lithium chloride. The solvent was removed in vacuo and a white solid was obtained. Finally, the desired phosphine was obtained after column chromatography was performed using n-hexane and 0.5% ethyl acetate (0.93 g, 2.19 mmol, q: 86%).

[0153] 1H-NMR (400 MHz, THF) 6 = 7.57 - 7.50 (m, 3H), 7.45 (dt, J=8.2, 0.9, 3H), 7.28 (ddd, J=8.3, 7.1 , 1.4, 3H), 7.19 (td, J=7.4, 1 .0, 3H), 2.38 (s, 9H).

[0154] 13C-NMR (101 MHz, THF) 6 = 158.08 (d, J=2.6), 146.54 (d, J=9.9), 130.09 (d, J=6.2), 127.58 (d, J=28.6), 126.16, 122.96, 120.29 (d, J=1 .8), 1 12.00, 8.95 (d, J=9.9).

[0155] 31P-NMR (122 MHz, THF) 6 = -88.93.

[0156] HRMS (ESI): m / z calcd. for C27H21O3P: 447.1120 [M+Na]+, found: 447.1 119. I. IX Synthesis of tris(benzo[1 ,2-b:4,5-b'1difuran-2-yl)phosphine

[0157] First, benzo[1 ,2-b:4,5-b']difuran (433 mg, 2.74 mmol, 3 eq.) was dissolved in 15 mL anhydrous diethyl ether in a Schlenk flask. Then, the solution was cooled to -78 °C and n- BuLi (2.5 M, 1 .1 mL, 2.75 mmol, 3 eq.) was added dropwise with a Schlenk dropping funnel. After the complete addition of n-BuLi, the reaction mixture was slowly warmed up to room temperature and stirred for 2 h. The yellow solution was cooled again to -78 °C and phosphorus trichloride (125 mg, 0.91 mmol, 1 eq.) was transferred dropwise to the reaction mixture. Then the solution was allowed to warm up to room temperature. As the next step, the light-yellow suspension was filtrated with a syringe filter to remove the lithium chloride. The solvent of the received yellow solution was removed in vacuo. Finally, the desired product was obtained after column chromatography was performed using n-hexane and 5% ethyl acetate (211 mg, 0.42 mmol, q: 46%).

[0158] 1H-NMR (400 MHz, THF) 6 = 7.78 (d, J=2.3, 3H), 7.72 - 7.66 (m, 6H), 7.42 - 7.36 (m, 3H), 6.89 (dd, J=2.2, 1.0, 3H).

[0159] 13C-NMR (101 MHz, THF) 6 = 155.99 (d, J=4.4), 153.02, 152.57 (d, J=3.6), 147.57, 127.85, 126.77 (d, J=5.4), 119.16, 118.96, 107.40, 102.75 (d, J=1 .8).

[0160] 31P-NMR (122 MHz, THF) 6 = -65.79.

[0161] HRMS (ESI): m / z calcd. for C30H15O6P: 503.0685 [M+H]+, found: 503.0684. I.X Synthesis of di(benzofuran-2-yl)(methyl)phosphine

[0162] Under argon atmosphere, di(benzofuran-2-yl)chlorophosphine (601 mg, 2 mmol, 1 eq.) was charged in a 100 mL Schlenk flask. Then, 25 mL of anhydrous diethyl ether were added and the solution was cooled to -78 °C. A methyllithium solution (1 .6 M, 1 .25 mL, 2 mmol, 1 eq.) was injected dropwise under stirring and the solution was allowed to stir for 1 h at -78 °C. The reaction mixture was slowly warmed up to room temperature and stirred overnight. After the suspension was anaerobically filtrated with a syringe filter, a light-yellow solution was obtained. Next, the solvent was removed in vacuo. The obtained yellow solid was recrystallized in dichloromethane, yielding colourless crystals (398 mg, 1 .42 mmol, q: 71 %).

[0163] 1H-NMR (400 MHz, THF) 6 = 7.55 (ddd, J=7.7, 1 .4, 0.8, 2H), 7.45 (dq, J=8.3, 1 .0, 2H), 7.28 - 7.21 (m, 2H), 7.20 - 7.16 (m, 2H), 7.15 (dd, J=1 .7, 1 .0, 2H), 1 .82 (d, J=4.1 , 3H).

[0164] 13C-NMR (101 MHz, THF) 6 = 158.63 (d, J=2.1), 156.59 (d, J=19.3), 128.97 (d, J=5.5), 125.62, 123.40, 121.74, 116.04 (d, J=21.9), 111 .79, 8.31 (d, J=5.5).

[0165] 31P-NMR (162 MHz, THF) 6 = -63.12.

[0166] HRMS (ESI): m / z calcd. for C17H13O2P: 281 .0731 [M+H]+, found 281 .0726.

[0167] I.XI Synthesis of di(benzofuran-2-yl)(phenyl)phosphine

[0168] The synthesis was carried out following the same procedure as described for di(benzofuran-2-yl)(methyl)phosphine above with phenyllithium (1.9 M, 1 .05 mL, 2 mmol, 1 eq.) instead of methyllithium. The desired product was obtained after column - M - chromatography was performed using n-hexane and 5% ethyl acetate (322 mg, 0.94 mmol, q: 47%).

[0169] 1H-NMR (400 MHz, THF) 6 = 7.67 - 7.59 (m, 2H), 7.57 (ddd, J=7.7 , 1 .4, 0.7, 2H), 7.48 (dq, J=8.3, 1.0, 2H), 7.41 - 7.35 (m, 3H), 7.32 - 7.24 (m, 2H), 7.23 - 7.15 (m, 2H), 7.11 (dd, J=1 .5, 1.0, 2H).

[0170] 13C-NMR (75.49 MHz, THF) 6 = 159.02 (d, J=3.0), 154.79 (d, J=11 .1), 134.21 (d, J=21.0), 133.63 (d, J=2.9), 130.36, 129.35 (d, J=7.7), 128.83 (d, J=5.3), 125.91 , 123.54, 121.91 , 118.30 (d, J=20.2), 1 11.96.

[0171] 31P-NMR (162 MHz, THF) 6 = -44.83.

[0172] HRMS (ESI): m / z calcd. for C22H15O2P: 343.0888 [M+H]+, found: 343.0888.

[0173] I . X 11 Synthesis of di(benzofuran-2-yl)(2-methoxyphenyl)phosphine

[0174] Under argon atmosphere, di(benzofuran-2-yl)chlorophosphine (301 mg, 1 mmol, 1 eq.) was charged into a 100 mL Schlenk flask together with 15 mL of anhydrous THF and the solution was cooled to -78 °C. Then, another Schlenk flask was charged with degassed 2- bromoanisole (206 mg, 1 .1 mmol, 1.1 eq.) and 10 mL anhydrous THF were added. At -78 °C, n-BuLi (2.5 M, 0.44 mL, 1.1 mmol, 1 eq.) was added dropwise to the 2-bromoanisole solution and the temperature was kept for 1 h. Then, the lithiated anisole compound was transferred dropwise to the phosphine chloride solution at -78 °C. The reaction mixture was slowly warmed up to room temperature and stirred overnight. After the solvent was removed in vacuo, a column chromatography was performed using n-hexane and 15% ethyl acetate, yielding a white solid (156 mg, 0.42 mmol, q: 42%).

[0175] 1H-NMR (400 MHz, THF-c / s): 6 = 7.55 (ddd, J=7.7, 1.4, 0.7, 2H), 7.46 (dq, J=8.3, 0.9, 2H), 7.41 - 7.32 (m, 1 H), 7.30 - 7.22 (m, 2H), 7.21 - 7.15 (m, 2H), 7.14 - 7.08 (m, 1 H), 7.01 (q, J=1 .3, 2H), 7.00 - 6.96 (m, 1 H), 6.89 (tt, J=7.5, 0.9, 1 H), 3.76 (s, 3H).13C-NMR (75.49 MHz, THF-c / s): 6 = 162.16 (d, J=16.6), 158.93 (d, J=3.3), 155.13 (d, J=11 .3), 134.07, 131 .83, 129.05 (d, J=5.1), 125.57, 123.37, 122.01 (d, J=4.0), 121 .75, 121 .71 , 117.83 (d, J=18.5), 111 .91 , 111 .33 (d, J=2.1), 55.83.

[0176] 31P-NMR (162 MHz, THF-c / s): 6 = -44.83.

[0177] HRMS (ESI): m / z calcd. for C23H17O3P: 373,0993 [M+H]+, found: 373.0992.

[0178] I .X 111 Synthesis of di(benzofuran-2-yl)(furan-2-yl)phosphine

[0179] Degassed furan (142 mg, 2.1 mmol, 1.05 eq.) was charged into a 100 mL Schlenk flask together with 20 mL anhydrous diethyl ether. At -78 °C, n-BuLi (2.5 M, 0.8 mL, 2 mmol, 1 eq.) was added dropwise to the solution under stirring. The reaction mixture was allowed to slowly warm up to room temperature and stirred for 2 h. A separate Schlenk flask was charged with bis(benzofuran-2-yl)-phosphine chloride (601 g, 2 mmol, 1 eq.) and 15 ml anhydrous diethyl ether. The lithiated furan solution was transferred into a Schlenk dropping funnel and the solution was added dropwise to the phosphine chloride solution at -78 °C. After the reaction mixture was warmed up to room temperature and stirred for 2 h, the suspension was filtrated with a syringe filter. Then the solvent was removed in vacuo, which yielded a yellow oil. Finally, a colorless oil of the target product was received after vacuum distillation. (1 .86 g, 6.59 mmol, q: 78%).

[0180] 1H-NMR (400 MHz, THF) 6 = 7.83 (dt, J=1 .6, 0.7, 1 H), 7.57 (ddd, J=7.7, 1 .4, 0.7, 2H), 7.48 (dq, J=8.3, 0.9, 2H), 7.28 (ddd, J=8.4, 7.2, 1.4, 2H), 7.22 - 7.13 (m, 4H), 7.05 (ddd, J=3.3, 2.0, 0.7, 1 H), 6.52 (dt, J=3.4, 1.7, 1 H).

[0181] 13C-NMR (101 MHz, THF) 6 = 158.85 (d, J=3.8), 152.98 (d, J=3.0), 149.23 (d, J=3.0), 128.82 (d, J=5.4), 125.96, 123.62, 123.55, 123.28, 121.95, 117.86 (d, J=19.9), 111.97, 111.68 (d, J=6.6).

[0182] 31P-NMR (122 MHz, THF) 6 = -70.87. HRMS (ESI): m / z calcd. for C20H13O3P: 355.0494 [M+Na]+, found: 355.0500.

[0183] I .XIV Synthesis of di(benzofuran-2-yl)(1 ,3-dioxolan-2-yl)phosphine

[0184] According to the procedure of Shiner et al., 2-lithio-1 ,3-dioxolan was prepared from (1 ,3- dioxolan-2-yl)tri-n-butylstannane (381 mg, 1 .05 mmol, 1 eq.) by the addition of n-BuLi (2.5 M, 0.42 mL, 1.05 mmol, 1 eq.) at -78 °C. A separate Schlenk flask was charged with bis(benzofuran-2-yl)-phosphine chloride (301 g, 1 mmol, 1 eq.) and 10 mL anhydrous THF. At -78 °C, the 2-lithio-1 ,3-dioxolan THF solution was added slowly to phosphine chloride solution and the temperature was kept for 1 h. Then the reaction mixture was allowed to warm up to room temperature and stirred overnight. After the solvent was removed in vacuo, the received yellow solid was dissolved in anhydrous dichloromethane. The obtained yellow solution was filtrated with a syringe filter to remove the lithium chloride. Finally, colorless crystals (115 mg, 0.34 mmol, q: 34%) were received from a concentrated DCM solution at -32 °C.

[0185] 1H-NMR (400 MHz, THF-ds): 6 = 7.58 (ddd, J=7.7, 1.4, 0.7, 2H), 7.49 (dq, J=8.3, 0.9, 2H), 7.34 - 7.23 (m, 4H), 7.23 - 7.15 (m, 2H), 6.41 (d, J=8.6, 1 H), 4.14 - 3.86 (m, 4H).

[0186] 13C-NMR (101 MHz, THF-da): 6 = 158.68 (d, J=2.4), 153.06 (d, J=16.5), 128.78 (d, J=5.8), 125.87, 123.45, 121.86, 118.36 (d, J=19.5), 111.90, 106.94 (d, J=16.5), 66.02 (d, J=3.0).

[0187] 31P-NMR (161 .98 MHz, THF-da): 6 = -62.86.

[0188] HRMS (ESI): m / z calcd. for C19H15O4P: 366.0600 [M+Na]+, found: 366.0608. I.XV Synthesis of di(benzofuran-2-yl)(dibenzo[b,d1furan-4-yl)phosphine

[0189] A flame dried Schlenk flask was charged with dibenzofuran (353 mg, 2.1 mmol, 1 .05 eq.) and 10 mL anhydrous diethyl ether. At -20 °C, n-BuLi (2.5 M, 0.8 mL, 2 mmol, 1 eq.) was added dropwise to the solution and the temperature was kept for 1 h. Then the reaction mixture was allowed to slowly warm up to room temperature and stirred for 2 h. Bis(2-furyl)- phosphine chloride (601 mg, 2 mmol, 1 eq.) was weighted in a separate Schlenk flask and was dissolved in 15 mL of anhydrous diethyl ether. The lithiated benzofuran solution was transferred into a Schlenk dropping funnel and the orange solution was slowly added to the phosphine chloride at -78 °C. After the complete addition of the benzofuran solution, the reaction mixture was warmed up to room temperature. Next, the lithium chloride was removed from the reaction mixture by anaerobic filtration with a syringe filter and the solvent was removed in vacuo. Then, column chromatography was performed using n-hexane and 0.5% ethyl acetate, yielding a white solid (545 mg, 1.26 mmol, q: 63%) as the desired product.

[0190] 1H-NMR (400 MHz, THF) 6 = 8.10 (dd, J=7.7, 1.3, 1 H), 8.03 (ddd, J=7.7, 1.4, 0.7, 1 H), 7.57 (ddd, J=7.8, 1 .4, 0.7, 2H), 7.55 - 7.46 (m, 4H), 7.46 - 7.40 (m, 1 H), 7.40 - 7.25 (m, 4H), 7.24 - 7.14 (m, 4H).

[0191] 13C-NMR (101 MHz, THF) 6 = 159.12 (d, J=3.5), 158.74 (d, J=17.9), 156.96, 153.39 (d, J=9.4), 132.37 (d, J=2.2), 128.89 (d, J=5.4), 128.22, 125.98, 125.00 (d, J=3.5), 124.51 (d, J=2.3), 124.05 (d, J=1 .8), 123.71 , 123.56, 123.06, 121 .98, 121 .45, 118.81 (d, J=20.6), 116.82 (d, J=8.4), 112.36, 1 12.02.

[0192] 31P-NMR (162 MHz, THF) 6 = -58.49.

[0193] HRMS (ESI): m / z calcd. for C28H17O3P: 455.0807 [M+Na]+, found: 455.0808. I .XVI Synthesis of ethyldi(furan-2-yl)phosphine

[0194] Dry and freshly activated magnesium powder (0.158 g, 6.5 mmol, 1 .3 equiv.) was added to a round bottom flask and the system was flamed under vacuum. After cooling down the system, Et2O (15 mL, 0.33 mol / L) was added under argon. To this stirring solution, ethylbromide (1.1 equiv., 5.5 mmol) was added dropwise. The reaction was stirred for 2h at room temperature, while it was possible to see consumption of powder magnesium and evolution of bubbles (if this is not visible, one can warm up the reactional mixture with hands or with slightly warm water). Then, it was cooled down to -78°C and chlorodi(furan-2- yl)phosphine(1 .028 g, 5 mmol, 1.0 equiv.) was added dropwise. The reaction was slowly warmed up to room temperature and it was stirred overnight. After this period, the reaction was filtered in a 22 pL filter under argon, the solvent was removed under vacuum, and distillation under vacuum afforded the desired product as a colorless oil (652.9 mg, 3.36 mmol; q = 67%).

[0195] 1H NMR (300 MHz, CDCh) 6 = 7.63 (dd, J = 1 .8, 0.8 Hz, 2H), 6.74 (ddd, J = 3.2, 1 .9, 0.8 Hz, 2H), 6.39 (dt, J = 3.2, 1 .6 Hz, 2H), 2.15 (q, J = 7.6, 2H), 1 .05 (dt, J = 18.4, 7.6 Hz, 3H).

[0196] 13C NMR (75 MHz, CDCh) 6 = 151 ,8(d, J = 17.2 Hz), 146.9 (d, J = 1.4 Hz), 120.2(d, J = 24.2 Hz), 110.6(d, J = 6.0 Hz), 18.5, 10.11 (d, J = 15.9 Hz).

[0197] 31P NMR (122 MHz, CDCh) 6 = -57.2.

[0198] HRMS (ESI+) m / z calculated for [C10H11O2PH+] = 195.0570, found 195.0575. I .XVI I Synthesis of propyldi(furan-2-yl)phosphine

[0199] Dry and freshly activated magnesium powder (0.158 g, 6.5 mmol, 1 .3 equiv.) was added to a round bottom flask and the system was flamed under vacuum. After cooling down the system, Et2O (15 mL, 0.33 mol / L) was added under argon. To this stirring solution, n- propylbromide (1 .1 equiv., 5.5 mmol) was added dropwise. The reaction was stirred for 2h at room temperature, while it was possible to see consumption of powder magnesium and evolution of bubbles (if this is not visible, one can warm up the reactional mixture with hands or with slightly warm water). Then, it was cooled down to -78°C and chlorodi(furan-2- yl)phosphine(1 .028 g, 5 mmol, 1.0 equiv.) was added dropwise. The reaction was slowly warmed up to room temperature and it was stirred overnight. After this period, the reaction was filtered in a 22 pL filter under argon, the solvent was removed under vacuum, and distillation under vacuum afforded the desired product as a colorless oil (570.8mg, 2.74 mmol, q: 55%).

[0200] 1H NMR (300 MHz, CDCb) 6 7.62 (dd, J = 1 .8, 0.8 Hz, 2H), 6.73 (ddd, J = 3.3, 1 .9, 0.8 Hz, 2H), 6.38 (ddd, J = 3.3, 1.8, 1 .5 Hz, 2H), 2.19 -2.10 (m, 2H), 1.51 -1.35 (m, 2H), 1.00 (t, J = 7.3 Hz, 3H).

[0201] 13C NMR (75 MHz, CDCb) 6 152.0(d, J = 17.3 Hz), 146.9 (d, J = 1.5 Hz), 120.0 (d, J = 24.6 Hz), 110.6(d, J = 6.3 Hz), 27.7, 19.45 (d, J = 16.1 Hz), 15.6 (d, J = 13.9 Hz).

[0202] 31P NMR (122 MHz, CDCb) 6 -62.0.

[0203] HRMS (ESI+) m / z calculated for [CHHI3O2PH+] = 209.0726, found 209.0728. I .XVI 11 Synthesis of furan-2-yldipropylphosphine

[0204] Dry and freshly activated magnesium powder (0.316 g, 13.0 mmol, 2.6 equiv.) was added to a round bottom flask and the system was flamed under vacuum. After cooling down the system, Et2O (15 mL, 0.33 mol / L) was added under argon. To this stirring solution, n- propylbromide (2.2 equiv., 11.0 mmol) was added dropwise. The reaction was stirred for 2h at room temperature, while it was possible to see consumption of powder magnesium and evolution of bubbles (if this is not visible, one can warm up the reactional mixture with hands or with slightly warm water). Then, it was cooled down to -78°C and furan-2-yl dichloro(furan-2-yl)phosphine (0.8447 g, 5 mmol, 1.0 equiv.) was added dropwise. The reaction was slowly warmed up to room temperature and it was stirred overnight. After this period, the reaction was filtered in a 22 pL filter under argon, the solvent was removed under vacuum, and distillation under vacuum afforded the desired product as a colorless oil (320.9 mg, 1 .74 mmol; q: 35%).

[0205] 1H NMR (300 MHz, CDCb) 6 7.60 (dd, J = 1 .8, 0.7 Hz, 1 H), 6.66 (ddd, J = 3.2, 2.0, 0.7 Hz, 1 H), 6.36 (ddd, J = 3.1 , 1 .8, 1 .1 Hz, 1 H), 1 .90 -1 .76 (m, 2H), 1 .59 (dddd, J = 13.4, 9.7, 6.0, 3.6 Hz, 2H), 1 .50 -1 .29 (m, 4H), 0.96 (t, J = 7.3 Hz, 6H).

[0206] 13C NMR (75 MHz, CDCb) 6 154.9(d, J = 28.4 Hz), 146.4, 119.6 (d, J = 24.4 Hz), 110.3(d, J = 5.9 Hz), 29.1 (d, J = 6.4 Hz), 19.7(d, J = 13.6 Hz), 15.9(d, J = 12.2 Hz).

[0207] 31P NMR (122 MHz, CDCb) 6 -45.1 .

[0208] HRMS (ESI+) m / z calculated for [CIOHI7OPH+] = 185.1090, found 185.1088. I .XIX Synthesis of difuran-2-yl)(neopentyl)phosphine

[0209] Dry and freshly activated magnesium powder (0.158 g, 6.5 mmol, 1 .3 equiv.) was added to a round bottom flask and the system was flamed under vacuum. After cooling down the system, Et2O (15 mL, 0.33 mol / L) was added under argon. To this stirring solution, neopentylbromide (1.1 equiv., 5.5 mmol) was added dropwise. The reaction was stirred for 2h at room temperature, while it was possible to see consumption of powder magnesium and evolution of bubbles (if this is not visible, one can warm up the reactional mixture with hands or with slightly warm water). Then, it was cooled down to -78°C and chlorodi(furan-2- yl)phosphine(1 .028 g, 5 mmol, 1.0 equiv.) was added dropwise. The reaction was slowly warmed up to room temperature and it was stirred overnight. After this period, the reaction was filtered in a 22 pL filter under argon, the solvent was removed under vacuum, and distillation under vacuum afforded the desired product as a colorless oil (279.1 g, 1.18 mmol, q: 24%).

[0210] 1H NMR (300 MHz, CDCb) 6 7.61 (dd, J = 1 .8, 0.7 Hz, 2H), 6.69 (ddd, J = 3.3, 2.0, 0.8 Hz, 2H), 6.36 (dt, J = 3.3, 1 .7 Hz, 2H), 2.24 (d, J = 3.3 Hz, 2H), 0.97 (d, J = 1 .1 Hz, 9H).

[0211] 13C NMR (75 MHz, CDCb) 6 152.8(d, J = 16.3 Hz), 146.7(d, J = 1.5 Hz), 119.6(d, J = 25.8 Hz), 110.7 (d, J = 6.4 Hz), 40.7(d, J = 4.2 Hz), 31 .1 (d, J = 13.2 Hz), 30.5 (d, J = 9.1 Hz).

[0212] 31P NMR (122 MHz, CDCb) 6 -69.1 .

[0213] HRMS (ESI+) m / z calculated for [Ci3Hi7O2PH+] = 237.1039, found 237.1041. I .XX Synthesis of difuran-2-yl)(propyl)phosphine oxide

[0214] To a solution of di(furan-2-yl)(propyl)phosphine (1.0 equiv., 1.7 mmol) in dichloromethane (~15 mL) in a flask with a magnetic stirred bar was slowly added aqueous solution of H2O2 (70 equiv., 30 wt%). The mixture was stirred for 3 hours at room temperature. After that time, the layers were separated and the organic phase was washed with water (2 x 30 mL) and it was dried over Na2SC>4. The solvent was evaporated under reduced pressure and the crude product was purified by column chromatography, resulting in the desired product in 75% yield as a white solid (276.1 mg, 1 .23 mmol, q: 74%).

[0215] 1H NMR (300 MHz, CDCb) 6 7.60 (ddd, J = 2.5, 1.7, 0.7 Hz, 2H), 7.02 (ddd, J = 3.5, 1.8, 0.7 Hz, 2H), 6.43 (ddd, J = 3.5, 1 .7, 1 .3 Hz, 2H), 2.27 -2.15 (m, 2H), 1 .68 -1 .53 (m, 2H), 0.95 (td, J = 7.4, 1.1 Hz, 3H).

[0216] 13C NMR (75 MHz, CDCb) 6 147.9 (d, J = 7.7 Hz), 147.4 (d, J = 138.4 Hz), 121.7 (d, J = 18.6 Hz), 110.9 (d, J = 8.4 Hz), 31 .5 (d, J = 80.1 Hz), 15.3 (d, J = 16.1 Hz), 14.7 (d, J = 4.1 Hz).

[0217] 31P NMR (122 MHz, CDCb) 6 12.2.

[0218] HRMS (ESI+) m / z calculated for [CHHI3O3PH+] = 225.0675, found 225.0672.

[0219] II. In situ synthesis of coordination complexes according to the invention comprising cobalt as a coordination centre and screening of their catalytic activity for the isomerization of / V, / V-diethylgeranylamine to citronellal enamine

[0220] Under argon atmosphere, an oven-dried 25 mL Schlenk tube was charged with a cobalt(ll) precursor coordination complex (kind / amount as indicated in Table 1 below), a selected compound of formula (I) according to the invention (ligands as shown in Scheme 3 below in an amount as indicated in Table 1 below) and a stirring bar. Then, the Schlenk tube was sealed with a rubber septum and 2 mL of anhydrous solvent as indicated in Table 1 were added. The solution was allowed to stir for approximately 2 min. At room temperature, 0.2 mL of a DIBAL-THF-solution (with an amount of DIBAL as indicated in Table 1 below) was injected dropwise to the solution under stirring. The substrate, / V, / V-diethylgeranylamine (0.523 g, 2.5 mmol) was added to the solution and the Schlenk tube was sealed. The solution was heated for 24 h at 80 °C. Afterwards, the solution was cooled down to room temperature and the solvent was removed in vacuo. Finally, vacuum distillation of the obtained brown oil yielded the citronellal-enamine. The conversion of N,N- diethylgeranylamine to citronellal enamine was determined by GC analysis using hexadecane as internal standard. As it becomes apparent from Table 1 below, good conversion rates of N, / V-diethyl- geranylamine to citronellal enamine can be achieved through catalysis by the coordination complexes according to the present invention, even at a low amounts of precursor coordination complex equivalents (Co(X)2).

[0221] Scheme 3: Compounds of formula (I) according to the invention used in the screening

[0222] Table 1 : Results of the screening of the in situ generated coordination complexes according to the invention

Claims

Claims:1 . Compound of formula (I)(I), wherein R1is a residue independently selected from the group consisting ofor R1is a residue according to formula (II)wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, and wherein R2is a residue selected from the group consisting ofor R2is a residue according to formula (II)wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, andwherein,2. Compound of formula (I) according to claim 1 ,whereinwhereinwherein R1isand R is or wherein both R1and R2arewherein both R1and R2arewherein both R1and R2arewherein both R1and R2are, orwherein both R1and R2are3. Coordination complex comprising one, two, three, four or more compound(s) of formula (I) and / or (IV) as defined in claim 1 , 2 or 15 as ligand(s), preferably as monodentate or bidentate ligand(s).

4. Coordination complex according to claim 3, wherein the coordination centre is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel atom or is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel ion or is a 3d transition metal atom or ion, preferably wherein the coordination centre is a manganese, iron, cobalt, or nickel atom or a manganese, iron, cobalt, or nickel ion, more preferably wherein the coordination centre is a cobalt atom or ion.

5. Method for producing a compound of formula (I) as defined in claim 1 or 2 comprising or consisting of the following steps: a) Providing furan or a furan derivative, preferably wherein the furan derivative is selected from the group consisting of 2,3-dimethylfuran, benzofuran, 3- bromobenzofuran, 5-bromobenzofuran, 7-bromobenzofuran, 3- methylbenzofuran, benzo[1 ,2-b:4,5-b']difuran, 2-bromoanisol, (1 ,3-dioxolan- 2-yl)tri-n-butylstannane, and dibenzofuran, b) performing a lithiation reaction on the furan or furan derivative provided in step a) with a lithiation reagent, preferably wherein the lithiation reagent is selected from the group consisting of n-butyllithium, sec-butyllithium, and tert- butyllithium, to obtain a lithiated species of the furan or furan derivative, c) reacting the lithiated species of the furan or furan derivative obtained in step b) with phosphorus trichloride or with a compound according to formula (III)wherein R1is a residue independently selected from the group consisting ofwherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, preferably wherein R1is a residue independently selected from the group consisting of6. Method for producing a compound of formula (I) as defined in claim 1 or 2 comprising or consisting of the following steps: a) Providing a compound according to formula (III)wherein R1is a residue independently selected from the group consisting ofor R1is a residue according to formula (II)wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, preferably wherein R1is selected from the group consisting ofand b) reacting the compound provided in step a) with a lithiated compound, preferably wherein the lithiation compound is selected from the group consisting of isobutyllithium, methyllithium, and phenyllithium. 7 Method for producing a compound of formula (I) as defined in claim 1 or 2 comprising or consisting of the following steps: a) Providing a compound according to formula (III)(HI), wherein R1is a residue independently selected from the group consisting ofor R1is a residue according to formula (II)wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, preferably whereinand b) reacting the compound provided in step a) with an alkoxide, preferably with an ethoxide, more preferably with sodium ethoxide.

8. Use of a compound of formula (I) and / or (IV) as defined in claim 1 , 2 or 15 for producing a coordination complex, preferably a coordination complex as defined in claim 3 or 4.

9. Method for producing a coordination complex, preferably as defined in claim 3 or 4, comprising or consisting of the following steps: a) Providing a precursor coordination complex, wherein the coordination centre of the precursor coordination complex is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel atom or is a rhodium, ruthenium, palladium, iridium, manganese, iron, cobalt, or nickel ion or is 3d transition metal atom or ion, b) providing one or more compound(s) of formula (I) and / or (IV) as defined in claim 1 , 2 or 15, preferably obtained according to a method as defined in any of the claims 5 to 7, c) producing a solution or suspension comprising the precursor coordination complex provided in step a), the compound(s) of formula (I) and / or (IV) provided in step b), and one or more solvent(s), preferably one or more nonpolar solvent(s), more preferably wherein the one or more solvent(s) is / are selected from the group consisting of tetrahydrofuran, 2- methyltetrahydrofuran, toluene, cyclohexane, benzene, xylene, dibutyl ether, dioxane, hexane, and heptane, d) adding, preferably dropwise or portionwise, one or more reducing agent(s) to the solution produced in step c), preferably wherein the one or more reducing agent(s) is / are selected from the group consisting of diisobutylaluminium hydride, triethylaluminium, diisobutylaluminium hydride-tetrahydrofuran- solution, diisobutylaluminium hydride-toluene-solution, aluminium hydride, / V, / V-dimethylethylamine complex, lithium diisobutyl-tert-butoxyaluminium hydride, lithium aluminium hydride, sodium borohydride, and sodium triethylborohydride, e) optionally, isolating the coordination complex formed in step d) from the reaction mixture.

10. Use of a coordination complex as defined in claim 3 or 4 as a catalyst, preferably in a hydrogen transfer reaction, more preferably for the isomerization of a double bond in a substrate.11 . Use according to claim 10, wherein the substrate to be isomerized comprises two or more double bonds, preferably wherein only one of the double bonds is isomerized.

12. Use according to claim 10 or 11 , wherein the substrate to be isomerized further comprises one or more heteroatom(s), preferably further comprises one or more nitrogen atom(s).

13. Method, preferably hydrogen transfer reaction, more preferably for the isomerization of a double bond in a substrate, comprising or consisting of the following steps: a) Providing a coordination complex as defined in claim 3 or 4, b) providing a substrate to be isomerized, preferably wherein the substrate to be isomerized comprises two or more double bonds, c) contacting the coordination complex provided in step a) with the substrate provided in step b), and d) carrying out an isomerization reaction on the substrate catalyzed by the coordination complex.

14. Method according to claim 13, wherein the substrate provided in step b) comprises one or more heteroatom(s), preferably comprises one or more nitrogen atom(s), most preferably wherein the substrate provided in step b) is selected from the group consisting of / V, / V-dimethylgeranylamine, / V, / V-diethylgeranylamine, 1-[3,7- dimethylocta-2,6-dienyl]pyrrolidine, 4-[3,7-dimethylocta-2,6-dienyl]morpholine, N,N- diphenylgeranylamine, / V, / V-diethyl-3-methylbut-2-en-1 -amine, A / , / V-diethyl-3- methylhept-2-en-1 -amine, / V, / V-diethylhex-2-en-1 -amine, 3-cyclohexyl-A / , / V- diethylprop-2-en-1 -amine, / V, / V-diethyl-4,4,4-trifluorobut-2-en-1-amine, A / , / V-diethyl- 2-methylbut-2-en-1 -amine, / V, / V-diethyl-prop-2-en-1 -amine, A / , / V-diethyl-but-3-en-1 - amine, / V, / V-diethyl-pent-4-en-1 -amine, A / -[(cyclohex-1 -en-1 -y I) methyl]- A / - ethylethanamine, A / , / V-diethyl-3-phenylprop-2-en-1 -amine, 3-(4-chlorophenyl)- / V, / V- diethylprop-2-en-1 -amine, 3-(4-trifluoromethylphenyl)-A / ,A / -diethylprop-2-en-1- amine, 3-(4-methoxyphenyl)-A / ,A / -diethylprop-2-en-1 -amine, 3-(4-te / Y-butylphenyl)- / V, / V-diethylprop-2-en-1 -amine, 3-(4-cyanophenyl)- / V, / V-diethylprop-2-en-1 -amine, A / , / V-diethyl-3-phenylbut-2-en-1 -amine, / V, / V-diethyl-3-(4-fluorophenyl)-3- phenylprop-2-en-1 -amine, N, / -d iethy l-3-(1 ,3,5-trimethylphenyl)-3-phenylprop-2-en- 1-amine, and (2E,2’E)-3,3’-(1 ,4-phenylene)bis(N,N-diethylprop-2-en-1-amine).

15. Compound of formula (IV)OR— P— R1i2(IV), wherein R1is a residue independently selected from the group consisting ofor R1is a residue according to formula (II)wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, and wherein R2is a residue selected from the group consisting ofor R2is a residue according to formula (II)wherein R3, R4, and R5are independently selected from the group consisting of hydrogen, alkyl, or aryl, and / or R3forms an aromatic ring with R4and / or R4forms an aromatic ring with R5, andwherein

Images