PREPARATION PROCESS OF AN ENOL BICYCLIC ETHER

Abstract

The present invention relates to the field of organic synthesis and more specifically to a process for preparing a compound of formula (I) from the compound of formula (II) catalyzed by a metal complex.

Description

The present invention relates to the field of organic synthesis and more specifically to a process for preparing a compound of formula (I) catalyzed by a metal complex. Background of the Invention The bicyclic ether enol derivative of formula (I) is a typical intermediate compound towards more valuable compounds, such as saturated or unsaturated cyclic ketones. For example, 16-oxabicyclo[10.3.1]hexadedec-12ene or 14-methyl-16-oxabicyclo[10.3.1]hexadedec-12-ene are key intermediates towards highly prized perfumery ingredients such as exaltenone or Muscenone® (a trademark of Firmenich SA). Such intermediate compounds have been obtained for decades by the double reduction of a macrocyclic dione; for example, 1,5-cyclopentadecandione or 3-methylcyclopentadecan-1,5-dione, to the corresponding macrocyclic diol. For example, 1,5-cyclopentadecandiol or 3-methylcyclopentadecan-1,5-diol, followed by dehydrogenation and dehydration to form a macrocyclic enol ether. Direct formation of the enol ether from the starting material of a dione has never been reported. RRfrQnn / Lznz / E / YILI Ref. 318626 Therefore, there is still a need to develop a simpler process towards the bicyclic ether enol while simultaneously improving the yield. The present invention allows obtaining the compound of formula (I) from the cyclic diketone of formula (II) under transfer hydrogenation conditions using a secondary alcohol as the hydrogen source. Brief Description of the Invention The invention relates to a new process that allows the preparation of the compound of formula (I) starting from the compound of formula (II) avoiding the stage of formation and isolation of the corresponding diol. Therefore, the object of the present invention is a process for the preparation of a compound of formula (I) RRfronn / Lznz / E / YiAi in the form of any of its stereoisomers or a mixture thereof and wherein R1 represents a linear or branched C1-5 alkanediyl or alkenediyl group, optionally substituted with a phenyl group and R2 represents a linear or branched C1-10 alkanediyl or alkenediyl group, optionally substituted with a phenyl group; comprising the reaction of a compound of formula (II) RR^ann / Lznz / B / YiAi in the form of any of its stereoisomers and wherein R1 and R2 have the same meaning as defined in formula (I); with a metallic catalyst, provided that a ruthenium catalyst is excluded, and in the presence of a hydrogen source. Detailed Description of the Invention Surprisingly, it has now been discovered that the compound of formula (I) can be advantageously produced by a one-pot reduction and cyclization-dehydration reaction of the compound of formula (II) under transfer hydrogenation conditions. The conditions of the invention allow for avoiding the difficult handling of the corresponding diol and are highly selective for monoreduction. The process of the invention leads to the formation of a bicyclic ether enol in high yield without compromising the conversion. Furthermore, the process of the invention uses a catalytic system that can be recycled and avoids the use of toxic reagents such as borohydride, making such a transformation more sustainable. Therefore, a first object of the present invention is the process for preparing a compound of formula (I) RRfronn / Lznz / E / YiAi in the form of any of its stereoisomers or a mixture thereof and wherein R1 represents a linear or branched C1-5 alkanediyl or alkenediyl group, optionally substituted with a phenyl group and R2 represents a linear or branched C1-10 alkanediyl or alkenediyl group, optionally substituted with a phenyl group; comprising, or consisting of, the reaction of a compound of formula (II) (II) in the form of any of its stereoisomers and wherein R1 and R2 have the same meaning as defined in formula (I); with a metallic catalyst, provided that a ruthenium catalyst is excluded, and in the presence of a hydrogen source. According to any modality of the invention, the invention process is a one-step process. According to any modality of the invention, the process of the invention is a complete conversion process. By complete conversion process, the normal meaning in the art is understood; i.e., the process of the invention is carried out until the complete transformation of the compound of formula (II). According to any embodiment of the invention, a compound of formula (III) in a form of any of its stereoisomers and wherein R1 and R2 have the same meaning as defined in formula (I); it has not been formed. In other words, the process of the invention allows obtaining the compound of formula (I) in one step without the formation of the double reduction product of formula (III). The process of the invention primarily allows obtaining the compound of formula (I) without the formation of the unwanted overhydrogenated diol of formula (III); that is, the process of the invention is highly selective. According to any embodiment of the invention, and regardless of the specific aspects, compound (I) as well as the corresponding compound (II) may be in the form of any of its stereoisomers or mixtures thereof. For clarity, the term stereoisomer refers to any diastereomers, enantiomers, or racemates. In fact, compound (I) or (II) may have at least one stereogenic center that may have a different stereochemistry (i.e., when two stereogenic centers are present, compound (I) or (II) may have an (R,R) or (R,S) configuration). Each of such stereogenic centers may be in a relative or absolute R or S configuration or in a mixture thereof; in other words, such a compound of formula (II) or (I) may be in the form of the pure enantiomer or diastereomer, or in the form of a mixture of stereoisomers. According to any of the preceding embodiments of the invention, the compounds of formula (II) are compounds of C7-C20. According to any of the above embodiments of the invention, the compound (I) can be a compound of the formula RRhann / ιζηζ / E / γίΛΐ in a form of any of its stereoisomers and wherein R2 has the same meaning as defined in formula (I) and R3 represents a hydrogen atom or a methyl group. According to any of the above embodiments of the invention, the compound (II) can be a compound of the formula in the form of any of its stereoisomers and wherein R2 has the same meaning as defined in formula (I) and R3 represents a hydrogen atom or a methyl group. According to any embodiment of the invention, R1 represents a linear or branched C1-5 alkanediyl or alkenediyl group optionally substituted with a phenyl group. Preferably, R1 represents a linear or branched C1-4 alkanediyl group. Preferably, R1 represents a linear or branched C2-3 alkanediyl group. Even more preferably, R1 represents a 1,2-propanediyl group or a 1,2-ethanediyl group. Even more preferably, R1 represents a 1,2-propanediyl group. According to any embodiment of the invention, R2 represents a linear or branched C1-10 alkanediyl or alkenediyl group optionally substituted with a phenyl group. Preferably, R2 represents a linear or branched C1-10 alkanediyl group. Preferably, R2 represents a linear or branched C4-9 alkanediyl group. Preferably, R2 represents a linear or branched C4-g alkanediyl group. Even more preferably, R2 represents a 1,8-octanediyl group. According to any embodiment of the invention, R3 represents a hydrogen atom or a methyl group. Preferably, R3 may represent a methyl group. Non-limiting examples of suitable compounds of formula (I) may include 12oxabicyclo[6.3.1]dodec-8-ene, 10-methyl-12oxabicyclo[6.3.1]dodec-8-ene, 13-oxabicyclo[7.3.1]tridec-9-ene, 11-methyl-13-oxabicyclo[7.3.1]tridec-9-ene, 14oxabicyclo[8.3.1]tetradec-10-ene, 12-methyl-14oxabicyclo[8.3.1]tetradec-10-ene, 15oxabicyclo[9.3.1]pentadec-11-ene, 13-methyl-15-oxabicyclo[9.3.1]pentadec-11-ene, 16oxabicyclo[10.3.1]hexadec-12-ene, 14-methyl-1,16-oxabicyclo[10.3.1]hexadec-12-ene, 17oxabicyclo[11.3.1]heptadec-13-ene, or 15-methyl-17oxabicyclo[11.3.1]heptadec-13-ene. Preferably, the compound of formula (I) may be 16oxabicyclo[10.3.1]hexadec-12-ene, 14-methyl-1,16-oxabicyclo[10.3.1]hexadec-12-ene, 17oxabicyclo[11.3.1]heptadec-13-ene, or 15-methyl-17oxabicyclo[11.3.1]heptadec-13-ene. Preferably, the compound of formula (I) can be 16oxabicyclo[10.3.1]hexadec-12-ene or 14-methyl-16oxabicyclo[10.3.1]hexadec-12-ene. Even more preferably, the compound of formula (I) can be 14-methyl-16oxabicyclo[10.3.1]hexadec-12-ene. Non-limiting examples of suitable compounds of formula (II) may include cycloundecan-1,5-dione, 3-methylcycloundecan-l,5-dione, cyclododecan-1,5-dione, 3-methylcyclododecan-l,5-dione, cyclotridecan-1,5-dione, 3-methylcyclotridecan-l,5-dione, cyclotetradecan-1,5-dione, 3-methylcyclotetradecan-l,5-dione, cyclopentadecan-1,5-dione, 3-methylcyclopentadecan-l,5-dione, cyclohexadecan-1,5-dione or 3-methylcyclohexadecan-l,5-dione. Preferably, the compound of formula (II) can be cyclopentadecan-1,5-dione, 3-methylcyclopentadecan-1,5-dione, cyclohexadecan-1,5-dione, or 3-methylcyclohexadecan-1,5-dione. Even more preferably, the compound of formula (II) can be 3-methylcyclopentadecan-1,5-dione. The compound of formula (II) is a commercially available compound or can be prepared by various methods, such as that reported in Helvetica Chimica Acta 1967, 50, 705, or in WO2016104474 or WO2016184948. According to any embodiment of the invention, the catalyst is a metallic catalyst. Preferably, the metallic catalyst may be of the formula [M(0)m(X)n] (IV) wherein M is a metal selected from the group consisting of a transition metal or a post-transition metal, m is 0, 1 or 2, X represents an anionic ligand; yn is an integer between 1 and 6. According to any of the preceding embodiments of the invention, M may be a metal selected from the group consisting of metals in columns IIIA (such as Al), IVA, IIIB, IVB (such as Ti or Zr), VB (such as V), VIB, and VIIB of the periodic table. Preferably, M may be selected from the group consisting of aluminum, titanium, zirconium, and vanadium. RRfront / Lznz / E / YiAi According to any of the preceding embodiments of the invention, n can be an integer between 1 and 4. Preferably, n can be an integer between 2 and 4. Even more preferably, n can be 3 or 4. According to any of the preceding embodiments of the invention, X represents an anionic ligand. A non-limiting list of anionic ligands includes a hydrogen or halogen atom, a hydroxy, oxy, or beta-diketonate group, or an alkoxy or carboxylic radical. By the term beta-diketonate, the normal meaning in the technique is understood; that is, a group of the formula Ra(COCHCO) ~Raen where the Rasons are, independently of each other, an alkyl group from Ci to Cig and the negative charge is de-iocalized. According to any of the preceding embodiments of the invention, in formula (III), each X represents, simultaneously or independently, a hydrogen or fluorine atom, chlorine, bromine, or iodine, a hydroxy or acetylacetonate group, an alkoxy radical from Ci to Gis, such as a methoxy, ethoxy, or isopropoxy radical, sec-butoxy, or a carboxylic radical from Ci to Gis, such as an HCOO, CH3COO, CH3CH2COO, or phenylCOO radical. Preferably, each X represents, simultaneously or independently, a hydroxy, methoxy, ethoxy, propoxy, butoxy, isopropoxy, or acetylacetonate radical. Non-limiting examples of a suitable metal catalyst of formula (III) may include [A1(OR)3], RRhQnn / Ιζηζ / E / YΙΛΙ [A1(OAc)3], [Al(acac)s], [Ti(OR)4], [Ti(O)[acach], [Zr(OR)4], [Zr(acac)4], [V(O)[acac)2], [V(acac)3], [V(O)[ORH]; R is a Ci-e alkyl group, preferably R is a Cl-4 alkyl group. The metal catalyst can be added to the reaction medium of the process of the invention at a wide range of concentrations. As non-limiting examples, metal concentration values ​​ranging from 1000 ppm to 100000 ppm can be cited, with respect to the total amount of substrate. Preferably, the metal concentration will be between 5000 ppm and 15000 ppm. Needless to say, the process also works with more catalyst. However, the optimum concentration of the metal will depend, as is known to those skilled in the art, on the nature of the catalyst and the nature of the substrate. of the desired temperature and reaction time. According to any of the preceding embodiments of the invention, the hydrogen source is a hydrocarbon comprising at least one secondary alcohol functional group and having a boiling point equal to or greater than 80 °C, preferably equal to or greater than 110 °C, and even more preferably equal to or greater than 120 °C. Such a hydrogen source absorbs hydrogen while generating ketone. The hydrogen source that performs the absorption may be a secondary alcohol. In particular, the hydrogen source that performs RR^ann / Lznz / B / YiAi The absorption can be of the formula where R4 and R5, independently of each other, represent a linear C1-10 alkyl group optionally substituted with a hydroxy or aryl group, a linear C2-10 alkenyl group optionally substituted with a hydroxy or aryl group, a branched or cyclic C3-10 alkyl or alkenyl group optionally substituted with a hydroxy or aryl group, or a phenyl group optionally substituted with one to five C1-3 alkyl or alkoxy groups, hydroxy groups, or halogen atoms; or R4 and R5, when taken together, represent a linear or branched C2-10 alkanediyl or alkenediyl group optionally substituted with a hydroxy or aryl group. The hydrogen source of formula (V) is a C4-10 compound. The term aryl group has the standard meaning in the art; that is, an aromatic hydrocarbon group such as an optionally substituted phenyl or naphthyl group. Non-limiting examples of the optional substituent of the aryl group may include a C1-3 alkyl or alkoxy group, a hydroxyl group, or a halogen atom. According to any of the above embodiments, R4 may represent a linear C1-10 alkyl group optionally substituted with a hydroxy or aryl group, or a branched or cyclic C3-10 alkyl group optionally substituted with a hydroxy or aryl group, or a phenyl group optionally substituted with one to five C1-3 alkyl or alkoxy groups, a hydroxy group, or a halogen atom. Preferably, R4 may represent a linear C1-10 alkyl group optionally substituted with a hydroxy group, or a branched or cyclic C3-10 alkyl group optionally substituted with a hydroxy group. Preferably, R4 may represent a linear or branched C3-8 alkyl group optionally substituted with a hydroxy group. Even more preferably, R4 may represent a methyl, ethyl, propyl, isopropyl, butyl, or octyl group optionally substituted with a hydroxy group. According to any of the above embodiments, R5 may represent a linear C1-10 alkyl group optionally substituted with a hydroxy or aryl group, or a branched or cyclic C3-10 alkyl group optionally substituted with a hydroxy or aryl group. Preferably, R5 may represent a methyl, ethyl, or propyl group. According to any of the above embodiments, R4 and R5, when taken together, may represent a linear C4-7 branched alkanediyl or alkenediyl optionally substituted with a hydroxy group. Preferably, R4 and R5, when taken together, may represent a RR^ann / Lznz / B / YiAi C4-7 linear alkanedyl. Even more preferably, R4 and R5, when taken together, can represent a C4-5 linear alkanedyl. A non-limiting example of a suitable hydrogen source may include 1-phenylethan-1-ol, 2-methyl-2,4-pentanediol, cyclohexanol, 4-methylpentan-2-ol, cyclopentanol, or octan-2-ol. Preferably, the hydrogen source may be cyclopentanol or 4-methylpentan-2-ol. The hydrogen source can be added to the reaction medium of the process of the invention at a wide range of concentrations. Non-limiting examples include hydrogen source concentrations ranging from 1 equivalent to 50 equivalents, or even from 1 equivalent to 5 equivalents, with respect to the amount of compound of formula (II). It is unnecessary to mention that the optimum concentration of the hydrogen source will depend, as is known to those skilled in the art, on the nature of the source, the nature of the substrate, the temperature and catalyst used during the process, and the desired reaction time. According to any embodiment of the invention, the process of the invention can be carried out in the presence of a cocatalyst. Non-limiting examples of a suitable cocatalyst include a tertiary amine, such as pyridine, bis-pyridine, trimethylamine, lutidine, N,N-diisopropylethylamine, or 1,8-diazabicyclo[5.4.0]undec-7-ene. RRhann / ιζηζ / E / γίΛΐ a tertiary phosphine, or optionally substituted phenols, or optionally substituted bisphenols. Preferably, the cocatalyst can be a tertiary amine or a substituted pyridine or bisphenol. Even more preferably, the cocatalyst can be a methylpyridine or dihydroxybiphenyl ingredient such as 2,2'-dihydroxydiphenylmethane, 2,2'-dihydroxybiphenyl. The cocatalyst can be added to the reaction medium of the process of the invention at a wide range of concentrations. As non-limiting examples, cocatalyst concentrations ranging from 0.1 to 2 equivalents with respect to the catalyst can be cited. It is unnecessary to mention that the optimum cocatalyst concentration will depend, as is known to those skilled in the art, on the nature of the cocatalyst, the nature of the substrate, the temperature and catalyst used during the process, and the desired reaction time. The invention process is carried out under discontinuous or continuous conditions. The reaction can be carried out in the absence of a solvent. The temperature of the process of the invention can be between 120 °C and 300 °C, more preferably in the range between 150 °C and 250 °C. Of course, RRfrQnn / Lznz / E / YILI An expert in the technique can also select the preferred temperature based on the melting and boiling points of the hydrogen source and the starting and ending products, as well as the desired reaction or conversion time. The process of the invention can be carried out at atmospheric pressure or under a slight vacuum. The process of the invention can be carried out in an inert atmosphere such as nitrogen or argon. According to any of the preceding embodiments of the invention, the more volatile compounds generated during the process are continuously removed during the process. The removal of such more volatile compounds, such as water and ketones formed during the process, can be achieved through distillation. Examples The invention will now be described in more detail by means of the following examples, in which abbreviations have their usual meanings in the art, temperatures are given in degrees Celsius (°C); NMR spectral data were recorded in CDCI3 (unless otherwise stated) using a 360 or 400 MHz machine for 3H and 13C, chemical shifts δ are given in ppm with respect to TMS as the standard, coupling constants J are expressed RRfrann / Lznz / E / YiAi in Hz. Example 1 Preparation of the compound of formula (I) from the compound of formula (II). In 11 glass reactors equipped with a mechanical stirrer, packed column, and reflux condenser, 250 g of 3-methyl-1,5-cyclopentadecandione (0.99 mol) were charged with 50 g of the hydrogen source (see Table 1) and V(acac)3 (17.2 g, 0.049 mol) at atmospheric pressure. The mixture was stirred and heated under reflux. The remaining hydrogen source (450 g) was then added over 22 h while the light fraction formed during the reaction (resulting water and ketone) was distilled into a flask. The resulting mixture was cooled to 100 °C, and the remaining solvent was concentrated under vacuum. The residual oil (230 g) was flash distilled (170 °C, 1 mbar), and the distillate was analyzed by GC (see Table 1). RRfrQnn / Lznz / E / YIL Table 1: Preparation of the compound of formula (I) from the compound of formula (II) Hydrogen Source Amount of Hydrogen Source (g) Reaction Temperature (°C) Reaction Pressure (mbar) Compound (I) (%) Compound (II) (%) Yield (%) 2) 4-methylpentan-2-oP 500 170 1000 89.1 3 85.6 Cyclopentanol 1* 500 175 1000 89.6 1 89.7 1) Pre-charge of 10% of the total charge and then add the rest over 16 h. 2) mainly full conversion and high selectivity. Example 2 Preparation of the compound of formula (I) from the compound of formula (II) In 11 glass reactors equipped with a mechanical stirrer, packed column, and reflux condenser, 250 g of 3-methyl-1,5-cyclopentadecandione (0.99 mol), 50 g of cyclohexanol, Zr(OPr)4 (4.63 g, 0.0098 mol, 70% in PrOH), and 2,2'-dihydroxydiphenylmethane (1.59 g, 0.0098 mol) were charged at atmospheric pressure. The mixture was stirred and heated under reflux. The remaining hydrogen source (450 g) was then added over 22 h while the light fraction formed during the reaction (water, cyclohexanol, cyclohexanone) was distilled into a flask. The resulting mixture was cooled to 100 °C, and the remaining solvent was concentrated under vacuum. The residual oil (242 g) was flash distilled (170 °C, 1 mbar) and the distillate was analyzed by GC (compound I 92.7% purity, 91.2% yield). 3-Methyl-1,5-cyclopentadecandiol did not form, and 3-methyl-1,5-cyclopentadecandione was completely converted. Example 3 Preparation of the compound of formula (I) from the compound of formula (II) In 11 glass reactors equipped with a stirrer In a mechanical, packed column with a reflux condenser, 250 g of 3-methyl-1,5-cyclopentadecandione (0.99 mol), 50 g of 2-octanol, Zr(OPr)4 (9.26 g, 0.0196 mol, 70% in PrOH), and 2,2'-dihydroxybiphenyl (3.7 g, 0.0196 mol) were charged at 200 mbar. The mixture was stirred and heated under reflux, then the remainder of the hydrogen source (250 g) was added over 16 h while the light fraction formed during the reaction (water, 2-octanol, 2-octanone) was distilled into a flask. The resulting mixture was cooled to 100 °C and the remaining solvent was concentrated under vacuum. The residual oil (230 g) was flash distilled (180 °C, 1 mbar) and the distillate was analyzed by GC (compound I 89.2% purity, 94.1% yield). 3-Methyl-1,5-cyclopentadecandiol did not form and 3-methyl-1,5-cyclopentadecandione was completely converted. Example 4 Preparation of the compound of formula (I) from the compound of formula (II) In 11 glass reactors equipped with a mechanical stirrer, packed column, and reflux condenser, 250 g of 3-methyl-1, 5-cyclopentadecandione (0.99 mol), 50 g of the hydrogen source (see Table 2), Ti(OiPr)4 (5.6 g, 0.02 mol) and 2,2'-dihydroxybiphenyl (3.7 g, 0.02 mol) were charged at the pressure indicated in Table 2. The mixture was stirred and heated under reflux, and then the remainder of the hydrogen source (450 g) was added. RRfronn / Lznz / E / YiAi was dosed for 22 h while the light fraction formed during the reaction (the resulting water and ketone) was distilled into a flask. The resulting mixture was cooled to 100 °C and the remaining solvent was concentrated under vacuum. The residual oil (~230 g) was flash distilled (170 °C, 1 mbar) and the distillate was analyzed by GC (see Table 2). RRfrQnn / Lznz / E / YILI Table 2: Preparation of the compound of formula (I) from the compound of formula (II) Hydrogen Source Amount of Hydrogen Source (g) Reaction Temperature (°C) Reaction Pressure (mbar) Compound (I) (%) Compound (II) (%) Yield (%) 4-Methylpentan-2-oP* 500 170 1000 88.5 1.35 95.6 CyclopentaneP 500 175 1000 84 1 0.9 95.2 Cyclohexanol1 500 170 450 83.8 1.35 93 1) Pre-charge of 10% of the total charge and then add the rest over 16 h. 2) mainly full conversion and high selectivity. Example 5 Preparation of the compound of formula (I) from the compound of formula (II) In 11 glass reactors equipped with a mechanical stirrer, packed column, and reflux condenser, 250 g of 3-methyl-1,1,5-cyclopentadecandione (0.99 mol), cyclopentanol (0.99 g), Al(0Bu)3 (12.3 g, 0.05 mol), and 2,2'-dihydroxydiphenylmethane (8 g, 0.05 mol) were charged at atmospheric pressure. The mixture was stirred and heated under reflux. The remaining hydrogen source (450 g) was then added over 22 h while the light fraction formed during the reaction (water, cyclopentanol, cyclopentanone) was distilled into a flask. The resulting mixture was cooled to 100 °C, and the remaining solvent was concentrated under vacuum. The residual oil (247 g) was flash distilled (170 °C, 1 mbar) and the distillate was analyzed by GC (compound I 85% purity, 85% yield). 3-Methyl-1,5-cyclopentadecandiol did not form, and 3-methyl-1,5-cyclopentadecandione was completely converted. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.

Claims

Having described the invention as above, the following claims are claimed as property:

1. A process for the preparation of a compound of formula (I) RRhQnn / IZPZ / E / YILI in the form of any of its stereoisomers or a mixture thereof, wherein R1 represents a linear or branched C1-5 alkanediyl or alkenediyl group, optionally substituted with a phenyl group, and R2 represents a linear or branched C1-10 alkanediyl or alkenediyl group, optionally substituted with a phenyl group; characterized in that it comprises the reaction of a compound of formula (II) in the form of any of its stereoisomers, wherein R1 and R2 have the same meaning as defined in formula (i); with a metal catalyst, provided that a ruthenium catalyst is excluded, and in the presence of a hydrogen source.

2. The process according to claim 1, characterized in that R1 represents a linear or branched Ci-4 alkanediyl group.

3. The process according to claim 1 or 2, characterized in that R1 represents a linear or branched C2-3 alkanedyl group.

4. The process according to any of claims 1 to 3, characterized in that R1 represents a 1,2-propanediyl group or a 1,2-ethanediyl group.

5. The process according to any of claims 1 to 4, characterized in that R2 represents a linear or branched C4-9 alkanedyl group.

6. The process according to any of claims 1 to 5, characterized in that R2 represents a linear or branched Ce-9 alkanediyl group.

7. The process in accordance with any of claims 1 to 6, characterized in that R2 represents a 1,8-octanediyl group.

8. The process according to any one of claims 1 to 7, characterized in that the compound of formula (I) can be selected from the group consisting of 12-oxabicyclo[6.3.1]dodec-8-ene, 10-methyl-12oxabicyclo[6.3.1]dodec-8-ene, 13-oxabicyclo[7.3.1]tridec-9-ene, 11-methyl-13-oxabicyclo[7.3.1]tridec-9-ene, 14-oxabicyclo[8.3.1]tetradec-10-ene, 12-methyl-14-oxabicyclo[8.3.1]tetradec-10-ene, 15-oxabicyclo[9.3.1]pentadec-11-ene, and 15-methyl-17oxabicyclo[11.3.1]heptadec-13-ene.

9. The process according to any one of claims 1 to 8, characterized in that the compound of formula (II) can be selected from the group consisting of cycloundecan-1,5-dione, 3-methylcycloundecan-1,5-dione, cyclododecan-1,5-dione, 3-methylcyclododecan-1,5-dione, cyclotridecan-1,5-dione, 3-methylcyclotridecan-1,5-dione, cyclotetradecan-1,5-dione, 3-methylcyclotetradecan-1,5-dione, cyclopentadecan-1,5-dione, 3-methylcyclopentadecan-1,5-dione, cyclohexadecan-1,5-dione and 3-methylcyclohexadecan-1,5-dione.

10. The process according to any one of claims 1 to 9, characterized in that the metal catalyst is of the formula [M(0)m(X)n] (IV) wherein M is a metal selected from the group consisting of a transition metal or a post-transition metal, m is 0 or 1 or 2, X represents an anionic ligand; and where n is an integer between 1 and 6.

11. The process according to claim 10, characterized in that M is selected from the group consisting of aluminum, titanium, zirconium and vanadium.

12. The process according to any of claims 1 to 11, characterized in that the metal catalyst is selected from the group consisting of [A1(OR)3], [A1(0Ac)3], [Al(acac)3], [Ti(OR)4], [Ti (0) (acach], [Zr(OR)4], [Zr(acac)4], [V(O) (acach], [V(acach] and [V(O) (ORH]; R is a Ci-e alkyl group.

13. The process according to any of claims 1 to 12, characterized in that the hydrogen source is a hydrocarbon comprising at least one secondary alcohol function and having a boiling point equal to or greater than 80 °C.

14. The process according to any one of claims 1 to 13, characterized in that the hydrogen source is of the formula RRfrann / Lznz / E / YiAi where R4 and R5, independently of each other, represent a linear C2-10 alkyl group optionally substituted with a hydroxy or aryl group, a linear C2-10 alkenyl group optionally substituted with a hydroxy or aryl group, a branched or cyclic C3-10 alkyl or alkenyl group optionally substituted with a hydroxy or aryl group, or a phenyl group optionally substituted with one to five C1-3 alkyl or alkoxy groups, hydroxy groups, or halogen atoms; or R4 and R5, when taken together, represent a linear or branched C2-10 alkanediyl or alkenediyl group optionally substituted with a hydroxy or aryl group.

15. The process according to any of claims 1 to 14, characterized in that the hydrogen source is 1-phenylethan-l-ol, 2-methyl-2,4-pentanediol, cyclohexanol, 4-methylpentan-2-ol, cyclopentanol or octan-2-ol.