EP3250577A1

EP3250577A1 - Hydrosilane/lewis acid adduct, particularly aluminum, iron, and zinc, method for preparing same, and use of said same in reactions for reducing carbonyl derivatives

Info

Publication number: EP3250577A1
Application number: EP16707853.4A
Authority: EP
Inventors: Claude Grison; Vincent ESCANDE
Original assignee: Centre National de la Recherche Scientifique CNRS; Universite de Montpellier I; Universite de Montpellier
Current assignee: Centre National de la Recherche Scientifique CNRS; Universite de Montpellier I; Universite de Montpellier
Priority date: 2015-01-30
Filing date: 2016-01-29
Publication date: 2017-12-06
Also published as: WO2016120574A1; US10099986B2; US20180009730A1

Abstract

The present invention relates to: - an adduct between a Lewis acid, preferably aluminum trichloride, iron trichloride, or zinc dichloride, and a hydrosilane; - a method for preparing same; and - use of same in a reaction for reducing, particularly, an aldehyde, a ketone, an α,β-unsaturated ketone, an imine, or an α,β-unsaturated imine.

Description

HYDROSILANE / LEWIS ACID ADDUCT, IN PARTICULAR ALUMINUM, IRON AND ZINC, PROCESS FOR PREPARING THE SAME AND USE THEREOF

REDUCING REACTIONS OF CARBONYL DERIVATIVES

The present invention relates to the field of the synthesis of aicoofs, ketones and ethers by reduction of a ketone or an enone by an adduct between a Lewis acid, advantageously aluminum trichioride, iron trichloride. or zinc dichloride, and a hydride donor silane.

The synthetic chemistry industry is experiencing a paradigm shift. The current craze of "all natural", "all organic" creates a new market oriented towards "green" products. At the same time, the hardening of the REACH regulation and the bad perception of chemistry by public opinion are converging towards a new approach to chemistry, which today wants to be eco-responsible. This rapid evolution is reflected in the development of new environmentally friendly synthesis processes focused on the preparation of bio-sourced products. This situation is a real scientific and technical challenge, which requires innovation and integration of new synthesis strategies. The cosmetics industries are the first to be part of this approach and clearly demonstrate their interest in ecological organic chemistry and bioinspired processes.

The reduction of carbonyl compounds, such as ketones, aldehydes, and esters and their nitrogenous derivatives such as imines and nitrates is a fundamental reaction of organic chemistry.

The reduction of these compounds thus makes it possible to obtain alcohols or amines.

There are a large number of reagents capable of carrying out these reactions, in particular aluminum or boron hydrides.

Among the hydride sources available, hydrosilanes have been used more rarely to carry out the reduction of carbonyl groups, because of their relative inertia vis-à-vis these groups.

The reduction of carbonyl groups indeed requires their concomitant activation by Lewis acid, such as, for example, tris- (pentafluorophenyl) borane, or the activation of the hydride by a transition metal, such as copper or rhodium.

It is also possible to reduce carbonyl groups by activation of the hydrosilane by a nucleophile, such as a fluoride. Polymethylhydrosiloxane (PMHS) is a waste product of the silicone industry. It is an abundant and inexpensive compound having the property of being a hydride donor, already used in halide reduction reactions in the presence of transition metals or as a hydride donor for the reduction of carbonyl groups in the presence of a Lewis acid.

Hydrosilanes, such as triethylsilane (C _zH ₆ ) ₃ Si-H are also used as reducing agents. These species are not intrinsically nucleophilic and only react with highly positively polarized compounds. Their use therefore requires the use of catalysts based on transition metals such as rhodium or Lewis acids capable of generating a cationic species sufficiently reactive.

Definitions:

For the purposes of the present invention, the term "adduct" means the product of the reaction between an appropriate amount of the Lewis acid and the hydrosilane. The adduct differs from the product formed when the same amount of the Lewis acid and the hydrosilane is introduced directly into the reaction medium! wherein the reduction reaction of the carbonyl compound is carried out. This difference in structure is reflected in particular by a different reactivity and can be detected by analytical methods such as NMR or infra-red spectroscopy. The adduct, within the meaning of the present invention is thus preformed, that is to say prepared before the implementation of an organic synthesis reaction and can be isolated.

The term "aprotic polar solvent" is used in this application in the conventional sense for the skilled person. Such solvents include, for example, dimethylsulfoxide, dimethylformamide, linear or cyclic ethers and chlorinated solvents.

For the purposes of the present invention, the term "carbocycic ary" means an unsaturated, mono or polycyclic aromatic ring of 5 to 14 members. Among the aryls, mention may be made of phenyl, naphthyl and phenanthrenyl groups.

For the purposes of the present invention, the term "heterocyclic aryl" means an unsaturated, mono or polycyclic aromatic ring of 5 to 10 members in which one or more of the CH groups have been replaced by one or more heteroatoms. Among the heteroaryls, there may be mentioned pyridyl, pyrrolydinyie, furyl, pyrimydinyl, tienyl, imidazolyl and pyrrolyl groups.

For the purposes of the present invention, the term "saturated or unsaturated cycioakyl having from 3 to 7 carbon atoms and optionally comprising one or more heteroatoms selected from nitrogen, sulfur or oxygen atoms; a 3- to 7-membered mono or polycyclic saturated ring. Among the cycloalkyls, there may be mentioned morphoiinyie, pyrrolidinyl, piperidinyl, tetrahydrofuranyl, tetrahydropyranyie and tetrahydrothiophenyl rings.

For the purposes of the present invention, the term "araikyl" means an unsaturated ring, mono or polycyclic aromatic 5 to 14 members linked to the rest of the molecule by an alkyl chain of 1 to 6 carbon atoms. Among the aralkyls, mention may especially be made of benzyl and phenylethyl groups.

For the purposes of the present invention, the term "linear or branched alkylene having at most 12 carbon atoms" an alkyl chain of 2 to 12 carbon atoms in which is present at least one double bond. Among the alkylenes, there may be mentioned the ethenyl, propenyl, butenyl and heptenyl groups.

For the purposes of the present invention, the term "optionally substituted" means that one or more hydrogen atoms present on the alkyl or alkylene chain, on the aryl or heteroaryl ring may be replaced by an atom or a functional group such as an alkyl group, in particular methyl, ethyl, propyl or butyl, amino, hydroxy, alkoxy, in particular methoxy, ethoxy, propoxy, a halogen, in particular a fluorine atom or a CF ₃ group.

The present invention relates to an adduct between a Lewis acid, preferably aluminum trichioride, iron trichioride or zinc dichloride and a hydrosilane.

The inventors of the present invention have discovered that such an adduct between a Lewis acid and a hydrosilane, has an increased reactivity compared to the simple mixture of Lewis acid and hydrosilane in the reaction medium used for the reduction. an aldehyde, a ketone, an α, β-unsaturated ketone, an imine, or an α, β-unsaturated imine, advantageously an α, β-ketone or ketone; unsaturated.

This increased reactivity is reflected in particular by a better yield and an improved selectivity.

The adduct between aluminum trichioride and a hydrosilane also has, in addition to its improved reactivity, the advantage of being stable to moisture and air, unlike, for example, aluminum trichioride which must be handled in strict anhydrous conditions with known toxicity. The hydrosilane may be chosen from monomeric, oligomeric or polymeric compounds comprising in their structure at least one Si-H group. Examples of hydrosilanes are trialkylsilanes, such as triethylsilane (Et ₃ SiH) and tri (isopropyl) silane, tris (trimethylsilyl) silane, triphenylsilane, hydrosiloxanes such as polymethylhydrosiloxanes (PMHS), polydimethylsiloxanes having a terminal SiH group, such as tetramethyldisiloxane, methylhydro-dimethylsiloxane copolymer, methylhydrophenyl-methylsiloxane copolymer, methylhydrocyanopropylsiloxane copolymer, methylhydroethyloctylsiloxane copolymer, poly (1,2-dimethylhydrosilazane), 1-methyl-hydrosilazane copolymer) (1 2- (dimethylhydrosilazane) and methylhydrocyclosiloxane.

Advantageously, the hydrosilane is chosen from triethylsilane, polymethylhydrosiloxanes and polydimethylsiloxanes having a terminal Si-H group. Polymethylhydrosiloxanes and polydimethylsiloxanes having a terminal Si-H group are in particular PMHS or tetramethyldisiloxane.

The Lewis acid is advantageously chosen from zinc (II), tin (11) or (IV), iron (11) or iron (III), copper (I) and palladium (II) salts. ), titanium (III) or (IV), bismuth (III) or aluminum (III), or a mixture of these Lewis acids, advantageously aluminum (NI), iron (III) or zinc (11).

Particularly advantageously, the Lewis acid is aluminum trichloride, iron trichloride or zinc dichloride.

The ratio between the Lewis acid and the hydrosilane depends on the nature of the compound to be reduced and can be adjusted by those skilled in the art. Advantageously, the ratio between the Lewis acid, advantageously aluminum trichloride, iron trichloride or zinc dichloride and the hydrosilane in the adduct is from 1: 1 to 1: 50, advantageously from 1: 1 at 1:10, more preferably from 1: 1 to 1: 5 and especially from 1:20, 1:10, 1: 3 or 1: 5.

The adduct as described above may also contain one or more additives capable of improving the reactivity of the Lewis acid. The additive may be selected from a second Lewis acid (different from the first Lewis acid of the adduct), preferably in a ratio of 1: 1 with respect to the hydrosilane, a metal salt, a alcohol, advantageously Γ-n-propanol or tert-butanol, preferably in a ratio of 2/1 relative to the Lewis acid or a dihalogene, especially cuprous iodide.

Advantageously, the additive is an alcohol selected from among n-propanol and n-butanol, preferably in a ratio of 2: 1 with respect to the Lewis acid. In a first embodiment, the present invention relates to an adduct between aluminum trichioride and a hydrosilane. The adduct may in particular be an adduct between aluminum trichioride and PMHS, preferably in a molar ratio of 1/1 or 1 / 5. The adduct may also be an adduct between aluminum trichioride and the triethylsilane, preferably in a molar ratio of 0.3 / 1.

The aluminum adduct may also contain one or more additives capable of modulating the reactivity of the Lewis acid, for example by increasing the selectivity in the reduction reactions. The additive may be chosen from a second Lewis acid, advantageously zinc dichloride, preferably in a ratio of 1: 1 with respect to hydrosilane, a metal salt, an alcohol, advantageously 1/1 ^'n-propanol or ie / t-butanol, preferably in a ratio of 2/1 with respect to the aluminum or dihalogen, particularly cuprous iodide.

Advantageously, the additive is an alcohol selected from 7α-propanol and β-butanol, preferably in a ratio of 2: 1 with respect to the Lewis acid.

In a preferred embodiment, the present invention relates to an adduct as described above between aluminum trichloride ie, ie triethylsilane and I ^'/' n-propanol, preferably in a molar ratio of 0.3 / 1 / 0.6.

In a second embodiment, the present invention relates to an adduct between iron trichioride and a hydrosilane. The adduct may in particular be an adduct between iron trichioride and PMHS or an adduct between iron trichioride and triethylsilane. Advantageously, the molar ratio FeCl ₃ / TES or PMHS may vary from 0.01 / 1 to 1/1, advantageously from 0.05 / 1 to 0.3 / 1. An adduct in which the ratio Fe / TES or PMHS is 0.3 / 1 or 0.15 / 1 is preferred.

The iron adduct may also contain one or more additives capable of modulating the reactivity of the Lewis acid, for example by increasing the selectivity in the reduction reactions. The additive may be chosen from a second Lewis acid, advantageously zinc dichloride, preferably in a ratio of 1: 1 with respect to hydrosilane, a metal salt, an alcohol, advantageously I '/ ^'n-propanol or fe / f-butanol, preferably in a ratio of 2/1 with respect to the aluminum or dihalogen, particularly cuprous iodide.

Advantageously, the additive is an alcohol chosen from P / so-propano! and tert-butanol, preferably in a ratio of 2 / with respect to the Lewis acid.

In a preferred embodiment, the present invention relates to an adduct between trichloride iron, triethylsilane and an alcohol, in particular chosen from the ^'/' so- propanol and ie fe / t-butanol. The ratio of FeCl _{3 to} alcohol is advantageously 1 2. The present invention therefore relates very particularly to a TES / FeCl ₃ / -PrOH or f-BuOH adduct in a 1 / x / 2x molar ratio where X varies from 0.01 to 1, advantageously from 0.05 to 0.3 and is preferably 0.05.

The adduct defined above is advantageously obtained by a process comprising heating the Lewis acid, preferably aluminum trichloride and the hydrosilane in an aprotic polar solvent or in the absence of a solvent.

Advantageously, the solvent is anhydrous.

Advantageously, the aprotic polar solvent is chosen from linear and cyclic ethers. It is advantageously diethyl ether, eryth-butyl ether and methyl, tetrahydrofuran, cyclopentyl methyl ether and 2-methyltetrahydrofuran, especially 2-methyl-tetrahydrofuran or cyclopentyl methyl ether. . 2-methyl-tetrahydrofuran, because it is a solvent obtained from biomass, respecting the principles of green chemistry, and cyclopentyl methyl ether, for its stability and its ability to limit the formation of peroxides, are the preferred solvents.

The reactions can also advantageously be carried out without a solvent.

Advantageously, the adduct is obtained at a temperature of 10 to 120 ° C, more preferably 30 to 100 ° C, especially 55 to 80 ° C. The reaction time is a function of the temperature and is from 10 minutes to 180 minutes. The reaction time is typically between 0 and 40 minutes at a temperature of 70 ° C. The reduction of the temperature leads to an increase in this reaction time.

In a particular embodiment, the adduct is obtained in 2-methyl tetrahydrofuran at a temperature of approximately 70 ° C. for a period of 30 minutes.

The present invention also relates to an adduct between a Lewis acid as obtained by the method described above.

In a first embodiment, the present invention relates to an adduct between aluminum trichloride and a hydrosilane chosen from PMHS, triethylsilane and tetramethyldisilane, and optionally an additive, as defined above, obtained by heating at a temperature of a temperature of 50 to 80 ° C in an aprotic polar solvent, advantageously an ether such as 2-methyltetrahydrofuran, cyclopentyl methyl ether, or without solvent.

In a second embodiment, the present invention also relates to an adduct between iron trichloride and a hydrosilane chosen from PMHS, triethylsilane and tetramethyldisilane and optionally an additive, as defined above. above, obtained by heating at a temperature of 50 to 80 ° C in an aprotic polar solvent, advantageously an ether such as 2-methyltetrahydrofuran, cydopentyl methyl ether, or without solvent,

The present invention also relates to the use of an adduct between a Lewis acid, preferably aluminum trichtoride or iron trichloride, a hydrosilane and optionally an additive, as defined above in a reduction reaction, in particular the reduction of an aldehyde, a ketone, an α, β-unsaturated ketone, an imine, or an α, β-unsaturated imine, advantageously an α-ketone or ketone. , β-unsaturated.

Advantageously, the amount of adduct is chosen so as to comprise 1 to 5 equivalents of hydrides per mole of aldehyde, α, β-unsaturated aldehyde, ketone, α, β-unsaturated ketone, imine, or of α, β-unsaturated imine, advantageously of α, β-unsaturated ketone or ketone.

Advantageously, the amount of adduct is chosen so as to comprise from 1 to 1.5 hydride equivalents per mole of α, β-unsaturated aldehyde, α, β-unsaturated ketone or α, β-unsaturated imine. advantageously α, β-unsaturated ketone or 4 to 5 equivalents of hydrides per mole of aldehyde, ketone or imine, advantageously ketone.

The number of equivalents of hydrides can be easily calculated by the skilled person. When the hydrosilane is a monomeric compound such as triethylsilyane, the number of equivalents of hydrides corresponds to the number of equivalents of the monomeric hydrosilane. For example, in the case of triethylsilyane, 1 mole of hydride will correspond to 1 mole of triethylsilyane present in the adduct. When the hydrosilane is an oligomeric or polymeric silane such as PMHS, the number of hydrides is calculated on the basis of the hydride content of the polymer, determined by assay.

This content is also given in the case of commercial products. For example, PMHS is marketed in a form containing 1 mmol of hydride per 60 L volume of PMHS.

Of course, its amount of adduct can be determined by the skilled person depending on the substrate and the desired product. For example, to obtain an alcohol from an α, β-unsaturated ketone, at least two equivalents of hydrides per mole of α, β-unsaturated ketone are required.

The reduction is carried out at a temperature of 0 to 100 ° C, preferably 15 to 80 ° C. The reduction is carried out in a polar aprotic solvent, advantageously a linear or cyclic ether, especially diethyl ether, tert-butyl methyl ether, tetrahydrofuran, cyclopentyl methyl ether and 2-methyl tetrahydrofuran, preferably 2-methyl-tetrahydrofuran or cyclopentyl methyl ether or in the absence of solvent. The solvent may also be an ester, for example an acetic acid ester, such as ethyl acetate or butyl acetate.

The adduct may be used alone or in admixture with another Lewis acid, with a metal salt, with a dihalogen or with an alcohol.

The inventors have demonstrated an improvement in the selectivity of the reduction reactions in which the adduct between aluminum trichloride or iron trichloride and a hydrosilane is employed when an additive is used. that another Lewis acid, a metal salt, a dihalogen or an alcohol is introduced into the reaction medium or when an adduct between aluminum trichloride or iron trichloride, a hydrosilane and an additive is used. In the case of the reduction of an α, β-unsaturated ketone, this improvement results in a total selectivity for the saturated ketone resulting from the reduction 1, 4 of said α, β-unsaturated ketone.

Advantageously, the further Lewis acid is -titanium trichloride 'or zinc dichloride, the metal salt comprises at least an iodide ion, preferably cuprous f'iodure, the dihalogen is ₂ or diiodine the alcohol is isopropanol or ierf-butanol.

In one embodiment, the adduct between aluminum trichloride or iron trichloride and hydrosilane is used in combination with diiodine, copper iodide, zinc dichloride, propanol and the like. or Fe / f-butanol. Advantageously, an adduct is used between iron trichloride or aluminum trichloride, hydrosilane and n-propanol or tert-butanol.

When another Lewis acid, a metal salt, a dihalogen or an alcohol is used with the adduct, the ratio between the hydrosilane and the other Lewis acid, the metal salt or the dihalogen varies from 1: 3 to 1: 1, especially 1: 1, 2.

When the compound to be reduced is an α, β-unsaturated ketone, an α, β-unsaturated imine or an α, β-unsaturated aldehyde, advantageously an α, β-unsaturated ketone, the adduct is advantageously an adduct between an acid of Lewis, advantageously aluminum chloride or iron trichloride and a trialkylisilane, advantageously triethylsilane. Particularly advantageously, the adduct is an adduct prepared with another Lewis acid, advantageously zinc dichloride, preferably in a ratio of 1: 1 with respect to the hydrosilane, metallic, an alcohol, advantageously isopropanol! or Fe-butanol, preferably in a ratio of 2: 1 with respect to aluminum trichloride or iron trichloride, or a dihalogen, especially cuprous iodide or diiodine.

When the compound to be reduced is a ketone, an imine or a saturated aldehyde, advantageously a ketone, the adduct is advantageously an adduct between a Lewis acid, advantageously aluminum trichloride, iron trichloride or zinc dichloride and a hydrosilane, advantageously PMHS, TMDS or triethylsiiane, preferably triethylsiiane.

The inventors have been able to demonstrate that the choice of the adduct makes it possible to control the product obtained by the reaction. In the case of saturated ketones in which the carbons adjacent to the carbonyl group C = O are CH ₂ groups, the use of an adduct between a Lewis acid, advantageously aluminum trichloride or iron trichloride and PMHS or triethylsiiane selectively provides an ether and the use of an adduct between the zinc dichloride and the tréthylsilane can selectively obtain an alcohol.

The selectivity of the reaction, and therefore the product obtained, depend on the adduct used and the solvent. For example, in the case of cyclohexanone, [PMHS-AICI ₃ ] adducts, [TMDS-AIC! ₃ ], [TES-AICI ₃ ], preferably [TES-AICI ₃ ], promote the formation of ether in Se 2-methyl-tetrahydrofuran. Adducts such as [TES-ZnCi ₂ ] make it possible to control the reduction to the corresponding alcohol in cyclopentyl methyl ether.

The present invention advantageously relates to the use as described above of an adduct between a Lewis acid, advantageously aluminum trichloride, iron trichloride or zinc dichloride and a hydrosilane for the reduction of a compound comprising a cyclopentanone, cyclopentenone, cyclohexanone or cyclohexenone unit or an aryl vinyl ketone unit. These compounds are commonly used in the cosmetics industry for their odor and / or aromatic properties, especially in the preparation of perfumes. Examples that may be mentioned include jasmone and dihydrojasmone for cyclopentanones and cyclopentenones, pulegone and menthone for cyclohexenones and cyclohexanones, or frambinone for aryl vinyl ketones. Other compounds possessing this type of structure and possessing odorant and / or aromatic properties having such a structure known to those skilled in the art can be reduced according to the method described above and hereinafter. Advantageously, the compound to be reduced is a ketone, α, β-unsaturated ketone, imine or imine α, β-unsaturated linear of formula (la):

(la) in which:

X represents O or NR _a , R _a being chosen from linear or branched alkyl having at most 12 carbon atoms, linear or branched alkyl having not more than 6 carbon atoms, carbocyclic or heterocyclic aryl, an alkyl radical, each of these Alkyl, alkyl, aralkyl or aryl radicals being optionally substituted, represents a single bond or a double bond.

R 1 represents a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkyl having not more than 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising one or more selected heteroatoms; among the nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, arylene, aryl, aralkyl or cycloalkyl radicals being optionally substituted,

R ₂ represents hydrogen, linear or branched alkyl having at most 12 carbon atoms, linear or branched alkyl having not more than 6 carbon atoms, carbocyclic or heterocytic aryl, each of these alkyl, alkyene or aryl radicals being optionally substituted,

R ₃ and R _{4j, which are} identical or different, represent hydrogen, linear or branched alkyl having at most 12 carbon atoms, linear or branched alkylene having at most 6 carbon atoms, carbocyclic or heterocyclic aryl, an aralkyl radical, each of these alkyl radicals; alkylene, aralkyl or aryl being optionally substituted, and when represents a single bond,

R ₅ represents hydrogen, linear or branched alkyl _, having at most 12 carbon atoms, linear or branched alkyl having not more than 12 carbon atoms, carbocyclic or heterocyclic aryl, an aralkyl radical, each of these alkyl, alkyene, aralkyl or aryl radicals; being optionally substituted, and R ₆ represents hydrogen, linear or branched alkyl having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, carbocyclic or heterocytic aryl, an aralkyl radical, each of these radicals alkyl, alkylene, aralkyl or aryie being optionally substituted,

or a cyclic ketone, α, β-unsaturated ketone, imine or imine α, β-unsaturated ketone of formula (Ib):

(Ib)

in which :

n = 0 or 1, X and are as defined above,

R ₇ represents a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and possibly containing one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocytic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl, aryl or cycloalkyl radicals being optionally substituted, advantageously an alkyl radical having at most 2 carbon atoms,

R ₉ represents a hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising a or a plurality of heteroatoms selected from nitrogen, sulfur or oxygen, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of which alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, or a CHR ₁₂ - COORi ₃ ,

in which R _¾2 represents hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms and R ₃ represents a radica! linear or branched alkyl radical having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally containing one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, and when represents a single bond,

R ₃ and R _{10, which may be} identical or different, represent a hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocytic aryl radical or an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, or a group CHR ₂ - COOR ₁₃ ,

in which R ₁₂ represents hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms and R ₁₃ represents a linear or branched alkyl radical having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 atoms of carbon and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic aryl radical,

R _¾! represents hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, advantageously an alkyl radical having at most 12 atoms of carbon, or when ^~ represents a single bond, R ₇ and R _B together represent a group = CH-R _7a where R _7a represents hydrogen, a linear or branched alkyl radical having at most 11 carbon atoms, a saturated cycloalkyl radical or unsaturated having from 3 to 7 carbon atoms and optionally having one or more heteroatoms selected from nitrogen, sulfur or oxygen, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, advantageously an alkyl radical having at most 11 carbon atoms. Thus, in the compounds of formula (Ia) and (Ib) in which

represents a double bond, the groups R ₅ and R ₆ are absent from the compound of formula (Ia) and the groups Ra and R ₀ are absent from the compound of formula (Ib).

The compound to be reduced is in particular an α, β-unsaturated ketone or an α, β-unsaturated imine, advantageously an α, β-unsaturated ketone of formula (Ia1) below:

(Ia1)

wherein X, R 1, R ₂ , R 3 and R 4 are as defined above,

or a cyclic α, β-unsaturated ketone of formula (Ib1):

(Ib)

in which :

n = 0 or 1,

X, R ₇ , R ₈ , R ₈ , R 10 and R 11 are as defined above, is a double bond.

When the compound is a compound of formula (Ia1) or (Ib1), the adduct may advantageously be an adduct between aluminum trichioride, a hydrosilane, especially chosen from triethylsilane and PMHS, preferably triethylsane and an alcohol chosen from isopropanol and tert-butanol, advantageously in a ratio 0.3 / 1 / 0.6. The reduction of the α, β-unsaturated ketone with an adduct between aluminum trichioride and a hydrosilane may also be carried out in the presence of another Lewis acid, preferably zinc dichloride, advantageously in a ratio of 1: 1 relative to aluminum and in the absence of solvent. The adduct may also advantageously be an adduct between iron trichioride, a hydrosilane, in particular selected from triethylsilarte and PMHS, preferably triethylsilane, and an alcohol chosen from 1 '/ so-propanol and ierf-butanol, advantageously in a ratio x / / 2x where X varies from 0.01 to 1, advantageously from 0.05 to 0.3 and is preferably 0.05.

In an advantageous embodiment, the present invention relates to the use of an adduct as described above for the reduction of a linear α, β-unsaturated ketone (X = O) of formula (Ia1) in which R ₂ represents hydrogen or a linear or branched alkyl radical having at most 12 carbon atoms, advantageously hydrogen and one of the substituents R ₃ or R ₄ is hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms, and Another substituent is an optionally substituted carbocyclic aryl radical.

The present invention relates more particularly to the use of an adduct between a Lewis acid, advantageously aluminum trichloride, iron trichloride or zinc dichloride and a hydrosilane for the reduction of a compound of formula (IIa) next :

in which :

Rie and R ₁₆ represent, independently of one another, hydrogen, a linear or branched alkyl radical having at most 12 optionally substituted carbon atoms, advantageously chosen from methyl; ethyl; propyl, advantageously isopropyl; and butyl, advantageously tert-butyl; a linear or branched alkylene radical having at most 12 optionally substituted carbon atoms, a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, advantageously chosen from methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, preferably tert-butoxy; OH ; COOR ₃ where R13 is as defined above; CF ₃ ; halogen selected from F, Cl, Br and I, Sa said substituents R ₁₅ and R ₁₆ being positioned in the ortho, meta or para position of the ring, advantageously in the meta and para positions,

R ₁₅ and R ₁₈ being advantageously chosen from a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, in particular methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, advantageously ierf-butoxy; a linear or branched alkyl radical having at most 12 optionally substituted carbon atoms, advantageously chosen from methyl; ethyl; propyl, advantageously isopropyl; and butyl, preferably tert-butyl; and OH, and

R ₁₇ represents a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, advantageously an alkyl group chosen from methyl; ethylie; propyl, advantageously isopropyl; and butyl, preferably ter-butyl; especially methyl.

Advantageously, the compound of formula (IIa) is a ketone of formula (Mal) as follows:

in which :

R ₁₅ and R ₆ are independently of each other hydrogen, a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, especially methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, advantageously, but-butoxy; methyl; ethyl; propyl, advantageously isopropyl; and butyl, advantageously fert-butyl; and oh,

R ₁₇ represents a radical chosen from methyl, ethyl and butyl, especially methyl.

The present invention further relates to a process for the preparation of a compound of formula (illb) below: in which :

R ₆ represent, independently of one another, hydrogen, a linear or branched alkyl radical having at most 12 optionally substituted carbon atoms, advantageously chosen from methyl, ethyl, isopropyl and tert-butyl, a linear or branched alkyl radical. having at most 12 optionally substituted carbon atoms, a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, preferably selected from methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, advantageously, but-butoxy; OH ; COOR ₁₃ wherein R ₁₃ is as defined above; CF ₃ ; halogen chosen from F, Cl, Br and I, said substituents R ₁₅ and R ₁₆ being positioned in the ortho, meta or para position of the ring, advantageously in the meta and para positions,

Wherein R 1 and R 5 are preferably selected from a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, especially methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, preferably iert-butoxy; and oh,

R ₁₇ represents a linear or branched alkyl radical having at most 12 carbon atoms, advantageously an alkyl group selected from methyl; ethyl; propyl, advantageously isopropyl; and butyl, advantageously tert-butyl; especially methyl.

comprising the step of contacting a compound of formula (Ma)

with an adduct between a Lewis acid, advantageously aluminum trichioride, iron trichioride or zinc dichioride and a hydrosilane as defined above.

Advantageously, the compound of formula (IIa) is brought into contact with an adduct between a Lewis acid, advantageously aluminum trichioride, iron trichioride or zinc dichioride and a hydrosilane in the presence of an iodinated derivative, such as than cuprous diiodine or iodide or an alcohol such as isopropanol or terbutanol.

Advantageously, the adduct is an adduct between aluminum trichioride or iron trichioride and a hydrosilane chosen from PMHS, triethylsilane and tetramethyldisilane, especially triethylsilane as defined above in the presence of a derivative. iodine, such as the diiod or cuprous iodide, of an alcohol te! as isopropanol or butyl iron or a Lewis acid, especially zinc dichioride.

In a particularly advantageous manner, the adduct between aluminum trichioride or iron trichioride and a hydrosilane is used in the presence of tert-butanol or isopropanol or zinc dichioride.

Preferably, the process is carried out in an aprotic polar solvent as defined above, preferably methyl tetrahydrofuran.

The present invention further relates to a process for the preparation of a compound of the following formula (! Ila1):

in which :

R ₁₅ and R ₆ represent independently of each other hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms optionally substituted, advantageously selected from methyl, ethyl, isopropyl and tert-butyl, a linear alkylene radical or branched group having at most 12 optionally substituted carbon atoms, a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, advantageously chosen from methoxy, ethoxy, propoxy, advantageously isopropoxy, or butoxy, advantageously tert-butoxy, OH , COOR ₁₃ where R ₃ is as defined above, CF _3s halogen selected from F, Cl, Br and I, said substituents R ₅ and R ₁₆ being positioned in the ortho, meta or para position of the ring, advantageously in the meta and para positions,

R ₁₅ and R ₁₈ being advantageously chosen from a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, in particular methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, preferably tert-butoxy; and oh,

R 1 is a linear or branched alkyl radical having at most 12 carbon atoms, preferably selected from methyl; ethylie; propyl, advantageously isopropyl; and butyl, preferably i-butyl.

comprising the step of contacting a compound of formula (liai)

with an adduct between a Lewis acid, advantageously aluminum trichloride, iron trichloride or zinc dichloride, and a hydrosilane.

In a particular embodiment, the compound of formula (IIa) is a ketone of formula (IIa) as follows:

in which :

R ₁₅ is a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, especially methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, advantageously, β-butoxy;

R ₁₆ is OH,

R-17 represents a radical chosen from methyl, ethyl and butyl.

The compound of formula Mal a is especially chosen from those in which R ₁ is methoxy, R ₆ is OH and R ₁₇ is methyl; R ₁₅ is ethoxy, R ₁₆ is OH and R ₁₇ is methyl; R ₁₅ is / propoxy, R ₆ is OH and R ₁₇ is methyl; R ₁₅ is / -propoxy, R ₁₆ is OH and R ₁₇ is methyl; R ₁₅ is n-butoxy, R ₆ is OH and R ₇ is methyl; R ₁₅ is i-butoxy, R _1e is OH and R ₁₇ is methyl; and R ₁₅ is ί-butoxy, R ₁₆ is OH and R ₁₇ is methyl; R ₁₅ is methoxy, R ₁₆ is OH and R ₁₇ is ethyl; R ₁₅ is ethoxy, R ₆ is OH and R 1 is ethyl; R ₁₅ is n-propoxy, R ₁₆ is OH and R ₇ is ethyl; R ₁₅ is -propoxy, R ₁₆ is OH and R ₇ is ethyl; R ₁₅ is n-butoxy, R ₁₆ is OH and R ₁₇ is ethyl; R ₅ is / -butoxy, R ₁₆ is OH and R ₁₇ is ethyl; and R ₁₅ is f-butoxy, R ₁₆ is OH and R ₇ is ethyl; R _i5 is methoxy, R ₁₆ is OH and R _i7 is prapyie; R ₁₅ is ethoxy, R ₁₈ is OH and R ₁₇ is propyl; R ₅ is n-propoxy, _ie R is OH and R ₇ is propyl; R 1 _S is / -propoxy, R ₁₆ is OH and R ₁₇ is propyl; R ₅ is / 7-butoxy, R _1e is OH and R ₁₇ is propyl; R ₁₅ is / -butoxy, R ₆ is OH and R ₁₇ is propyl; and R ₅ is f-butoxy, R ₁₆ is OH and R ₁₇ is propyl; R ₁₅ is methoxy, R _1e is OH and R ₁₇ is butyl; R ₁₅ is ethoxy, R ₁₆ is OH and R ₇ is butyl; R ₅ is n-propoxy, R ₁₆ is OH and R ₁₇ is butyl; R ₁₅ is / -propoxy, R- | ₆ is OH and R ₁₇ is butyl; R ₁₅ is n-butoxy, R- | ₆ is OH and R ₇ is butyl; R ₁₅ is / -butoxy, R ₁₆ is OH and R ₁₇ is butyl; and R ₁₅ is f-butoxy, R ₆ is OH and R ₁₇ is butyl.

When the compound is of formula (Ia), (IIa), (IIa) or (IIIa) above, advantageously a ketone, the adducts between a Lewis acid, advantageously aluminum trichloride or iron trichloride or zinc dichioride and a hydrosilane selected from trialkylsilanes, such as triethylsilyl (Et ₃ SiH) and tri (isopropyl) silane, tris (trimethylsilyl) silane, triphenylsilane and hydrosiloxanes such as polyethyl hydrosiloxanes (PMHS) and tetramethyldisioxane are used.

Particularly advantageously, the ketone is reduced with an adduct comprising another Lewis acid, a metal salt, a dihalogen or an alcohol, especially cuprous iodide, diiodine, isopropanol or ierf-butanol. In the case of low reactive α, β-unsaturated ketones such as those of formula (IIa) or (IIIa), the alcohol is preferably isopropanol.

When the adduct is an adduct of FeCl ₃ , the reduction is advantageously carried out in an ester of acetic acid as a solvent, for example ethyl acetate or butyl acetate. Even more advantageously, the reduction is carried out at a substrate concentration ranging from 1 M to 5 M, in particular from 2 to 4 M. The implementation temperature depends on the substrate and can be easily determined by Man of the Occupation. Typically, the temperature is 20 to 100 ° C, especially 30 to 80 ° C.

Advantageously, the invention relates to the use of an adduct as described above for the reduction of a ketone or an imine, advantageously a cyclic ketone of formula (Ib 1) below: wherein X, R ₇ , R ₈ , R ₉ and R- | ₀ are as defined above,

or of formula (Ib2):

wherein X, R ₇ , R _a and Ru are as defined above.

Among the compounds of formula (Ib2), mention may especially be made of the puiégone, in which R ₇ and R ₈ together represent a group = CHR _7a , where R _7a represents hydrogen, the reduction of which makes it possible to obtain menthone and / or ie menthoi, widely used in the agri-food industry.

The present invention thus relates, in a particular embodiment, to the use of an adduct between aluminum trichioride or iron trichioride, a hydrosilane chosen from triethylsilane and PMHS and an aicoof chosen from isopropanol and ierf-butanol, advantageously in a ratio 0.3 / 1 / 0.6 for the reduction of the puiongone menthone and / or menthol, preferably menthol. Preferably, the reduction of the putegone is carried out in the presence of zinc dichloride in a ratio of 1/1 relative to aluminum trichioride in the absence of solvent.

In an advantageous embodiment, the present invention relates to the use of an adduct as described above for the reduction of a cyclic ketone (X = O) of formula (Ib1) in which:

One of the substituents R ₇ or R ₈ is hydrogen and the other substituent is a linear or branched radical having at most 12 carbon atoms, akylene linear or branched chain having at most 12 carbon atoms, especially a linear alkyl radical having at most 12 carbon atoms,

One of the substituents R _g or R ₀ is hydrogen and the other substituent is a linear or branched alkyl radical having at most 12 carbon atoms or a CHR ₁₂ -COORi _{3 group} as defined above, advantageously in which R ₁₂ represents hydrogen and R- | ₃ represents a linear or branched alkyl radical having at most 12 carbon atoms, especially a methyl, ethyl, propyl or butyl radical.

The present invention relates more particularly to the use of an adduct between a Lewis acid, advantageously aluminum trichioride, iron trichloride or zinc dichloride and a hydrosilane for the reduction of a compound of formula (IIb) next :

in which: represents a single bond or a double bond,

R-14 represents a linear or branched alkyl radical having at most 11 carbon atoms, linear or branched alkylene having at most 11 carbon atoms, in particular a linear alkyl radical having at most 1 carbon atoms or a COOR ₁₃ group as defined above, advantageously in which R ₁₃ represents a linear or branched alkyl radical having at most 12 carbon atoms, in particular a methyl, ethyl, propyl or butyl radical.

The present invention further relates to a process for the preparation of a compound of formula (IIIb) below: in which: represents a single bond or a double bond,

R ₄ represents hydrogen, a linear or branched alkyl radical having at most 11 carbon atoms, linear or branched alkylene having at most 11 carbon atoms, in particular a linear alkyl radical having at most 11 carbon atoms or a COOR ₁₃ group such that defined above, advantageously in which R ₁₃ represents a linear or branched alkyl radical having at most 12 carbon atoms, in particular a methyl, ethyl, propyl or butyl radical.

comprising the step of contacting a compound of formula (IIb)

with an adduct between a Lewis acid, advantageously aluminum trichloride, iron trichloride or zinc dichloride and a hydrosilane as defined above.

When the compound is of formula (Ib 1), (Ib 2) or (IIb) above, advantageously a ketone, an adduct is preferably used between a Lewis acid, advantageously aluminum trichloride, iron trichloride or the zinc dichloride and a hydrosiloxane, especially a polymethylhydrosiloxane (PMHS) or tetramethyldisiloxane. Preferably, the reduction of the compounds of formula (Ib1), (Ib2) or (IIb) is carried out with an adduct A! CI ₃ / TES / / -PrOH in a molar ratio of 0.3 / 1/0 , 6; FeCl ₃ / TES / iPrOH in a molar ratio x / 2 / 2x; or FeCl ₃ / TES / t-BuOH in a molar ratio x / 2 / 2x, where X ranges from 0.01 to 1, advantageously from 0.05 to 0.3 and is preferably 0.05. For the reduction of these compounds with a FeCl _3i adduct, 2 equivalents of triethylsilane are preferably used. When the adduct is an adduct of FeCl ₃ , the reduction is advantageously carried out in an ester of acetic acid as a solvent, for example ethyl acetate or butyl acetate.

The inventors have demonstrated that if the substrate to be reduced is not very crowded, the high reactivity of the adducts can be used to form ethers.

The present invention also relates to the use of an adduct between a Lewis acid, advantageously aluminum trichloride or iron trichloride, preferably aluminum trichloride and a hydrosilane, advantageously a hydrosilane such as PMHS or triethylsilane for the reduction of a compound of formula (IV) below:

in which R ₁₈ and R ₁₉ independently of one another represent a linear or branched alkyl radical having at most 11 carbon atoms, optionally substituted or Ri ₈ and Ri ₉ are bonded together to form a saturated or unsaturated cycloalkyl radical having of 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms,

in a dialkyl ether of formula (V) below: Advantageously, the present invention relates to the use of an adduct between a Lewis acid, advantageously aluminum trichloride or iron trichloride, preferably aluminum trichloride and a hydrosilane, for the reduction of a cyclic ketone. of formula (IVa) below:

in which n = 1 to 4, advantageously 2 or 3, and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms,

in a dicycioakyl ether of formula (Va) below:

Advantageously, the reduction of the compound of formula (IVa) or (Va) is carried out with an adduct between aluminum trichloride and a hydrosilane, in particular PMHS or triethylsilane, preferably in methyl-THF.

The use of an adduct between aluminum trichioride and a hydrosilane, advantageously PMHS or triethylsilane for the reduction of a ketone in the presence of an alcohol, allows the formation of a mixed ether between the said ketone and the said alcohol. .

The present invention therefore also relates to the use of an adduct between a Lewis acid, advantageously aluminum trichloride or iron trichioride, preferably aluminum trichloride and a hydrosilane, advantageously PMHS or triethylsilane for the preparation of a compound of formula (Vb):

in which R ₈ and R ₁₉ represent, independently of one another, a linear or branched radical having at most 11 carbon atoms, optionally substituted or Ri and Ri _B are bonded together to form a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally having one or more heteroatoms selected from nitrogen, sulfur or oxygen, and R ₂₀ represents a linear or branched alkyl radical having at most 11 carbon atoms, advantageously from 1 to 3 carbon atoms.

Preferably, the adduct is an adduct between aluminum trichloride and triethylsilane, advantageously in a ratio of 0.3 / 1.

Advantageously, the reaction is carried out in methyl tetrahydrofuran.

In a particular embodiment, the present invention relates to the use of an adduct between aluminum trichloride, triethylsilyl, advantageously in a ratio 0.3 / 1 for the preparation of cydopenthy! methyl! ether or cyciopentyl ethyl ether.

The present invention also relates to a process for preparing an ether of formula (Vb):

wherein R1 and ₈ i ₉ independently of one another a linear or branched alkyl radical having at most 11 carbon atoms, optionally substituted or R1 ₈ and R ₁₉ are bonded together to form a cycloalkyl radical which is saturated or unsaturated of 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, and R ₂₀ represents a linear or branched alkyl radical having at most 11 carbon atoms, advantageously 1 at 3 carbon atoms.

comprising the step of bringing into contact a ketone of formula (IV) below: with an alcohol of formula R ₂₀ -OH and an adduct between aluminum trichloride and a hydrosiiane, advantageously ie triethylsiiane.

Advantageously, the ketone is a cyclic ketone of formula (IVa) below:

in which n = 1 to 4, advantageously 2 or 3, and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms. ¾

Advantageously, the adduct is an adduct between aluminum trichioride and a hydrosilane chosen from PMHS and triethylsilane.

Advantageously, the solvent is 2-methyltetrahydrofuran or the contacting step is carried out in the absence of a solvent.

In a particular embodiment, the present invention relates to a process for the preparation of cyclopentyl methyl ether comprising the step of contacting cyclopentanone, methanol and an adduct between aluminum trichioride and a hydrosilane, advantageously the triethylsilane, preferably in methyl tetrahydrofuran or in the absence of solvent.

In a particular embodiment, the present invention relates to a process for preparing cyclopentyl ethyl ether comprising the step of contacting cyclopentanone, ethanol, and the like. and an adduct between aluminum trichioride and triethylsilane, preferably in methyl tetrahydrofuran or in the absence of solvent.

Description of the figures:

Figure 1 shows the infra-red spectrum of an adduct between aluminum trichioride and tetramethyldisilane (top curve) compared to that of methyl-THF (bottom curve) and tetramethyldisilane (middle curve). In the adduct spectrum, peak intensity of tetramethyldisilane is decreased and peaks at different displacements occur, indicating the presence of a new species in the adduct between aluminum trichioride and tetramethyldisilane.

Examples

Example 1; Preparation of the PMHS-AICia adduct:

131 mg (1 mmol) of anhydrous AlCl ₃ and then 500 μL of Me-THF are introduced into a flask equipped with a magnetic stirring bar. The mixture is stirred at 25 ° C for 10 minutes. Moderate heating is observed due to the dissolution of AlCl ₃ in Me-THF. A clear pale pink to red solution is obtained. 300 pL (volume equivalent to 5 mmol of hydride) of PMHS are then introduced with stirring at 25 ° C. A cloudy solution is obtained, which consists of two immiscible phases. Heating at 70 ° C for 30 minutes causes the lightening of the solution, which then becomes colorless, clear and perfectly homogeneous. The PMHS-AICI adduct ₃ is ready for use in this form. This is stored in a closed bottle without an inert atmosphere being necessary.

Other hydrosilanes may be used in place of PMHS.

For example, tetramethyldisiloxane (TMDS) has also been used to prepare a TMDS-AICI ₃ adduct that is just as reactive as the PMHS-AICI adduct ₃ without the need for an excess of hydrosiloxane during its preparation.

Example 2 Preparation of adducts

Example 2.1. Preparation of the triethylsiiane-AICh adduct:

133 mg (1 mmol) of anhydrous AlCl ₃ are added in 250 ml of Me-THF. Once AICI ₃ solubilized, 800 μΙ (5 mmol) of triethylsilane are added. A cloudy solution is obtained having two immiscible phases. After heating for 2 hours at 80 ° C., a clear and homogeneous solution is obtained. The adduct Et ₃ SiH-AlCl ₃ is then ready for use. Its concentration in Al is 1.086 mo! / L.

Example 2.2. Preparation of the triethylsilane-AlCl 2 - / PrQH adduct:

2- eTHF

AIC adduct And ₃ SiH / AIC! ₃ // - PrOH

OH

0 ° C - 25 ° C (1: 0.3: 0.6)

Flight.

Mass n Vol.

Cumulated product M d

(g) (mmol) (mL)

(ML)

AICI ₃ 133.34 - 1.000 7.5 - -

2-MeTHF 86.13 0.860 5.375 62.4 6.250 6.250

And ₃ SiH 116.28 0.728 2,912 25.0 4,000 10,250

/ -PrOH 60.10 0.785 0.902 15.0 1.149 11.399 In a 25 ml ground flask equipped with a magnetic bar and an internal thermometer, 2-MeTHF is introduced. 2-MeTHF is cooled to 0 ° C. by means of an ice bath, with stirring at 800 rpm (stirring maintained throughout the preparation of the adduct).

At 0 ° C, AICI ₃ is added in 10 portions, one serving every 3 minutes. After each addition, a temperature rise of 5 to 8 ° C is observed. When the temperature of the reaction mixture has returned to 0 ° C, a new addition can be made. A clear pale yellow solution is obtained. After the additions are made, the temperature of the reaction mixture is allowed to rise to 25 ° C.

And ₃ SiH is then added all at once using a syringe. The temperature remains stable at 25 ° C. The resulting mixture is stirred for 10 minutes at 25 ° C. L7-PrOH is then added all at once using a syringe. The temperature remains stable at 25 ° C. The resulting mixture is stirred for 30 minutes at 25 ° C. The mixture fades gradually to become very pale yellow. The clear solution of the adduct And ₃ SiH / AlCl ₃ / PrOH (1: 0.3: 0.6) thus obtained is stored under argon at 25 ° C and can be used as it is. The adduct can be stored for several months without changing its reactivity.

Example 3 Reduction of Methyl Jasmmonate by the PMHS-AIC Adduct

1 h, 25 ° C

Conversion: 95%

Selectivity: 93%

11, 2 (0.05 mmol) of methyl jasmonate, 54 ί of adduct PMHS-AICI ₃ (prepared with 5 equivalents of hydrides from PMHS) are introduced into a flask equipped with a magnetic bar (54 μί). corresponding to 0.06 mmol of Al and 0.3 mmol of h ^"). The resulting solution was stirred at 25 ° C for 1 h. 500 μί of HCI 1 M _aq solution are then introduced. The solution is stirred at 25 ° C. for 5 minutes and then extracted with ethyl ether An analysis of the ether extract in GC-MS indicates a 95% conversion of the starting cyclopentanone with a selectivity of 93% for the product resulting from the reduction of C = 0 in CH-OH.

Example 4: Reduction of 4- (4-hydroxyphenyl) but-3-en-2-one: 2

In a flask fitted with a magnetic bar, 8.11 mg (0.05 mmol) of 4- (4-hydroxyphenyl) but-3-en-2-one are introduced, followed by 200 μl of Me-THF. A clear yellow solution is obtained. To this is then added 32.4 μL of the adduct PMHS-ASCi ₃ (prepared with 1 equivalent of hydride from PMHS) (32.4 μL corresponds to 0.05 mmol Ai and 0.05 mmol h ^"). the resulting solution was stirred at 70 ° C for 3 hours. 500 μΙ_ of a solution 1 M _aq HCS are then introduced. the solution is stirred for 5 min at 25 ° C, then extracted with ether An analysis of the ether extract in GC-MS indicates a conversion of 94% of the starting enone and a selectivity of 73% for the reduction product 1, 4. The other products observed are reduction products 1 , 2 or double reduction 1,4 and 1,2 or complete reduction of the side chain to butyl radical.

The reduction of 4- (4-hydroxyphenyl) but-3-en-2-one to frambinone was evaluated by comparing a generated adduct with aluminum trichloride and PMHS, an adduct generated with aluminum trichloride and a mixture of aluminum trichloride and PMHS that have not been pre-combined in the form of an adduct. The results obtained after 3 hours at 70 ° C. in 2-methyl-tetrahydrofuran are shown in Table 1:

As these results show, the use of a mixture of PMHS and aluminum trichloride leads to the formation of a complex mixture of products and no selectivity for the ketone is observed.

The use of an adduct between aluminum trichloride and a hydrosilane leads to the formation of saturated ketone with a very high yield and selectivity. The adduct according to the present invention is therefore particularly effective for the selective reduction of α, β-unsaturated ketones and ketones, and selectively.

In addition to being more efficient in terms of yield and selectivity, the PMHS-AICI ₃ adduct is also more suitable for handling in non-drastic conditions, since it is stable in the air and does not hydrolyze not spontaneously, unlike AIC! ₃ must be handled with care, under a hood, in a glove box, which is deliquescent and reacts violently with water.

Example 5: Reduction of 4- (4-hydroxyphenyl) but-3-en-2-one in the presence of an iodinated derivative

The reduction of 4- (4-hydroxyphenyl) but-3-en-2-one was also repeated under the conditions of Example 3 with a triethylsilyl / aluminum trichloride adduct in the presence of an iodinated derivative, either Cul, or the diiodine the ₂ or in the presence of an alcohol or isopropanol.

The results are shown in Table 2:

The adduct between aluminum trichloride and triethylsilane makes it possible to obtain the saturated ketone with high selectivity. 3

The selectivity of the reduction 1, 4 can be further increased if padduite and ₃ SiH / AlCl _{3 are used} in the presence of cuprous iodide, diiodine, or isopropanol.

The use of the adduct according to the present invention in the presence of an iodinated derivative or an alcohol te! that isopropanol makes it possible to perfectly control the reduction of an α, β-unsaturated ketone in position β.

The same reaction can be carried out with an adduct between iron trichloride and a hydrosilane, especially triethylsilyl. The results with iron trichloride and aluminum trichloride are summarized in Table 3:

Table 3:

The reaction can be carried out on a large scale (10 g) with similar conversion and selectivity (98% conversion and 99% selectivity).

These reaction conditions can be used with the compounds of formula IIa, especially chosen from those in which R ₅ is methoxy, R _1B is OH and R ₇ is methyl; Ris is ethoxy, R ₁₆ is OH and R ₁₇ is methyl; R ₅ is> propoxy, R _1e is OH and R ₇ is methyl; R ₁₅ is / -propoxy, R ₁₆ is OH and R ₁₇ is methyl; R _is n-butoxy, R ₁₆ is OH and R ₁₇ is methyl; R ₁₅ is / ^'-butoxy, R ₆ is OH and R ₁₇ is methyl; and R 15 is f-butoxy, R ₁₆ is OH and ₁₇ is methyl.

Additional tests aimed at improving the reaction conditions and / or reactivity with the FeCl ₃ adduct have also been carried out.

Example 5.1: Modification of the solvent 3

The reduction of 4- {4-hydroxyphenyl) but-3-en-2-one is repeated with the adduct TES-FeCl3-i-PrOH (1 / 0.3 / 0.6). The results are shown in Table 4.

Table 4:

The choice of ethyl acetate as a solvent promotes the selective reduction of 4- (4-hydroxyphenyl) but-3-en-2-one.

Example 5.2. Reduction of the catalytic iron charge

Additional tests to reduce the amount of FeCl ₃ have been carried out.

Input FeCI ₃ Solvent Temperature Conv. (%) Select {%)

1 20% Me-THF 70 ° C 99 92

2 10% Me-THF 70 ° C 83 95

3% Me-THF 70 ° C 16,100

4 20% AcOEt 70 ° C 94 83

5 0% AcOEt 50 ° C 96 80

6 0% AcOEt 70 ° C 97 77

7 5% AcOEt 50 ° C 55 99

8 5% AcOEt 70 ° C 90 88 The amount of iron can be reduced to 5% relative to the amount of substrate while maintaining high conversion and selectivity.

Example 5.3. Post-reaction treatment:

The conditions for isolating the product from the reaction crude have also been studied. Indeed, the isolation of the product is made difficult by the presence of residues siiyiés and the nature of the product (phenol).

The treatment conditions selected are therefore a weakly basic solution during the hydrolysis. The typical procedure for 0.4 mmol of hydrosilane involved is as follows: MeOH (1 ml) added to the base (example: NaHCO ₃ ) (10 ml) is added to the reaction mixture. The resulting mixture is stirred at room temperature for 3 h and then extracted with dichloromethane CH ₂ Cl ₂ ( ^3-20 ml). The organic phases are combined and then dried over MgSO ₄ and the solvent is removed under reduced pressure. The crude product is filtered on silica or dicalite.

Example 6 Preparation of an ether from cyclohexanone

A I'adduit triéthylsiiane-AICI ₃ of Example 2 are added 3.9 mg (4 mmol) of cyclohexanone and the solution was stirred at room temperature for 3 hours. At the end of the reaction, the dicyclohexyl ether is obtained with a selectivity of 100%.

Example 7 Preparation of Cyclopentyl Methyl Ether

Cyclo-opentanone (0.1 mmol, 8.9 ml) is diluted in methanot equivalent and 40 μM Me-THF. [TES-AlCl ₃ ] (1/1) (1 equivalent) prepared in Me-THF is added in 2 portions to cyclohexanone, and after 2 hours at 80 ° C. a total conversion of cyclopentanone is obtained. % CPME are obtained.

Example 8: Reduction of the puivegone:

It is possible to selectively reduce the position 1, 4 by means of the [TES-AICI ₃ ] system, the addition of Cul, I ₂ , or isopropanol, or of zinc dichloride to the adduct [ TES-AlCl ₃ -iPrOH], or of ferf-butanol makes it possible to increase the selectivity in favor of the position 4. It is total with the adducts [TES-A! C! ₃ -iPrOH + ZnCl ₂ ] and especially [TES-AlCl ₃ -tBuOH],

It is preferable to carry out the reaction without adding any solvent other than the one already present in the adduct.

It is also possible to chain the reduction of positions 1, 4, then 1, 2 to obtain menthol. This sharp reduction then necessitates the use of the adduct [TES-AlCI _3] in excess (3 equivalents). reduction 1-4 and 1-2

exclusive 1-4 discount

Exempt 9: Reduction of the Pulegone in Menthone

Pregone Menthone

To the adduct [TES-AlCl ₃ -tBuOH] (molar ratio 1 / 0.3 / 0.6) or [TES-AlCl ₃ -iPrOH-ZnCl ₂ ] (molar ratio 1 / 0.3 / 0.6 / 1) prepared in methyl-THF, 8.2 μί. (0.05 mmol) of pulegone are added and the solution is stirred at 80 ° C for 3 hours. At the end of the reaction, menthone is obtained with a selectivity of 92% and a yield of 73%. No trace of ether is observed.

With the adduct PMHS / FeCl ₃ / iPrOH (3: 0.3: 0.6), menthone is obtained with a yield of 83% and a selectivity of 67%.

The results of the reduction of pulegone with iron trichloride and aluminum trichloride are summarized in Table 5: Water!

It is important to note that PMHS-AÎC adducts! ₃ - / - PrOH (3 / 0.3 / 0.6) and TES-FeC! _3- i-PrOH (3 / 0.3 / 0.6) allows one-pot preparation of menthol from the pulegone.

Example 10 Preparation of 2-Pentylcyclopentanone

With triethylsilane-AIC adduct! _3-I PrOH (molar ratio 1 // 0.3 / 0.6) prepared in the cyclopentymethyl ether, 8.2 μL (0.05 mmol / 1 equivalent / TES) enone are added and the solution is stirred at 80 ° C. ° C for 3 hours. At the end of the reaction, the 2- penty! cyclopentanone is obtained with a selectivity of 100%. No trace of ether or cyclopentanol is observed.

The same reaction, carried out with a triethylsilane-FeCl ₃ -iPrOH adduct (molar ratio 1 / 0.3 / 0.6), triethylsilane-FeCl ₃ -iPrOH (molar ratio 2 / 0.3 / 0.6), triethylsilane- FeCl ₃ -iPrOH (1 / 0.5 / 0.6 molar ratio) or a triethylsilyl-FeCl ₃ adduct (molar ratio 2 / 0.3) leads to the formation of 2-pentylcyclopentanone with a conversion of 67, 84, 78 and 80% and ketone selectivity greater than 90%.

The results with adducts of iron trichloride and aluminum trichloride are summarized in Table 6:

Table 6

Example 11: Preparation of cyclohexanol from cyclohexanone.

To the triethylsilane-ZnCl ₂ adduct (molecular ratio 1/1) prepared in 50 μl cyclopentyl methyl ether, 4.9 mg (0.05 mmol, 1 equivalent / TES) of cyclohexanone are added and the solution is stirred at 90 ° C. C for 4 hours. At the end of the reaction, cyclohexanol is obtained with a selectivity of 00%.

Example 12 Preparation of 2-Dodecanol by Reduction of 2-Dodecacone

Me-THF

To the triethylsilane-2nCl ₂ adduct (1/1 molar ratio) prepared in 50 μl of cyclopentyimethyl ether, 11.2 μl (0.05 mmol, 1 equivalent / TES) of cyclohexanone are added and the solution is stirred at 90 ° C. ° C for 3 hours. At the end of the reaction, cyclohexanol is obtained with a selectivity of 100% and a conversion of 75%. No trace of ether or dodecane is observed.

Claims

1. Preformed adduct between a Lewis acid selected from zinc (II) salts, tin (I!) Or (IV), iron (11) or iron (III), copper (i), palladium (H), titanium (LiI) or (! V), bismuth (III) or aluminum (III) and a hydrosilane.

2. Adduct according to claim 1, wherein the Lewis acid is a zinc salt (11), in particular zinc dichloride, an iron salt (IN), especially iron trichloride, or a salt thereof. aluminum (III), especially aluminum trichloride.

3. Adduct according to one of claims 1 or 2, wherein the hydrosilane is selected from trialkylsiiennes, such as triethylsilane (Et ₃ SiH) and tri (isopropyl) silane, tris (trimethylsilyl) silane, triphenylisane polymethylhydrosiloxanes (PWIHS), polydimethylsiloxanes having a terminal Si-H group, such as tetramethyldisioxane, methylhydro-dimethylsiloxane copolymer, methylhydrophenylmethylsiloxane copolymer, methylhydrocyanopropylsiloxane copolymer, methylhydromethyloctylsiloxane copolymer, poly (1,2-dimethylhydrosilazane), 1-methyl-hydrosilane copolymer) (1,2-dimethylhydrosilazane) and methylhydrocyclosiloxane.

4. Adduct according to claim 3, wherein the hydrosilane is selected from polymethylhydrosiloxane, tetramethyldisiioxane and triethylsilane.

5. Adduct according to one of claims 1 to 4, further comprising another Lewis acid, a se! metallic, an alcohol, or a dihalogen.

6. Adduct according to claim 5, comprising an alcohol, advantageously isopropanol! or terf-butanol, especially in a molar ratio of Lewis acid / alcohol of 1/2.

7. AlCl ₃ / triethylsilane / isopropanol adduct! in a molar ratio 0.3 / 1 / 0.6.

8. Adduct FeC! ₃ / triethylsilane / so-propano! or FeC! ₃ / triethylsilane / tert-butanol in a molar ratio of x / 1 / 2x where X ranges from 0.01 to 1, preferably from 0.05 to 0.3 and is preferably 0.05.

9. Use of an adduct according to one of claims 1 to 8 in a reduction reaction of an aldehyde, an α, β-unsaturated aldehyde, a ketone, an α, β-unsaturated ketone , an imine, or an α, β-unsaturated imine.

10. The use according to claim 9, for the reduction of an α, β-unsaturated ketone or ketone, in particular a compound comprising a cyclopentanone or cycfopentenone unit, such as jasmone and dihydrojasmone; cyclohexanone or cyclohexenone, such as pulegone or menthone; or an aryl-vinyl-ketone unit, such as rambinone.

11. Use according to claim 9 or 10 for the reduction of a ketone, an α, β-unsaturated ketone, an imine or an α, β-unsaturated imine of formula (la):

in which :

X represents O or NR _a , R _a being chosen from linear or branched alkyl having at most 12 carbon atoms, linear or branched alkylene having at most 6 carbon atoms, carbocyclic or heterocyclic aryl, an aralkyl radical, each of these alkyl radicals; alkylene, aralkyl or aryl being optionally substituted, represents a single bond or a double bond,

R - (represents a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising a or a plurality of heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted,

R ₂ represents hydrogen, linear or branched alkyl having at most 12 carbon atoms, linear or branched alkylene having at most 6 carbon atoms, carbocyclic or heterocyclic aryl, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, R ₃ and R ₄ , which may be identical or different, represent hydrogen, linear or branched alkyl having at most 12 carbon atoms, linear or branched alkylene having at most 6 carbon atoms, carbocytic or heterocyclic aryl, an aralkyl radical, each of these radicals alkyl, alkyl, aralkyl or aryl being optionally substituted, and when represents a single bond,

R _s represents hydrogen, linear or branched alkyl having at most 12 carbon atoms, linear or branched alkyl, having at most 12 carbon atoms, carbocytic or heterocyclic aryl, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, and

R ₆ represents hydrogen, linear or branched alkyl having at most 12 carbon atoms, linear or branched alkyl with at most 12 carbon atoms, carbocytic or heterocyclic aryl, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted,

(Ib)

in which

n = 0 or 1,

X and are as defined above,

R ₇ represents a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocytic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl, aryl or cycloalkyl radicals being optionally substituted, advantageously an alkyl radical having at most 12 carbon atoms,

R ₉ represents a hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising a or a plurality of heteroatoms selected from nitrogen, sulfur or oxygen, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, arylene, aralkyl or aryl radicals being optionally substituted, or a CHR ₂ - COOR ₁₃ ,

in which R _1Z represents hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms and R ₁₃ represents a linear or branched alkyl radical having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 atoms of carbon and possibly comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic aryl radical, an aralkyl radical, each of these alkyl, arylene, aralkyl or aryl radicals being optionally substituted, and when represents a single bond,

R ₈ , and R _{0, which may be} identical or different, represent a hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, or a group CHR ₁₂ - COOR ₁₃ ,

in which R ₂ represents hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms and R ₃ represents a linear or branched alkyl radical having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 atoms of carbon and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic aryl radical,

Ru represents hydrogen, a linear or branched alkyl radical having at most 12 carbon atoms, linear or branched alkylene having at most 12 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and comprising optionally one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocyclic aryl radical, an aralkyl radical, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, advantageously a radica! alkyl having at most 12 carbon atoms, or when represents a single bond, R ₇ and f¾ together represent a group = CH-R _7a where R _7a represents hydrogen, a linear or branched alkyl radical having at most 1 carbon atoms, a saturated or unsaturated cycloalkyl radical having from 3 to 7 carbon atoms and optionally containing one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms, a carbocyclic or heterocyclic aryl radical, a radica! aralkyie, each of these alkyl, alkylene, aralkyl or aryl radicals being optionally substituted, advantageously an alkyl radical having at most 1 carbon atoms.

or for the reduction of a compound of formula (IV) below:

in which R ₈ and R ₁₉ independently of one another represent a linear or branched alkyl radical having at most 1 carbon atoms, optionally substituted or R ₁₈ and R ₁₉ are bonded together to form a saturated or unsaturated cycloalkyl radical having 3 to 7 carbon atoms and optionally comprising one or more heteroatoms chosen from nitrogen, sulfur or oxygen atoms.

12. Process for preparing a compound of formula (IIIb):

in which :

R ₁₅ and R-I represent, independently of one another, a linear or branched alkyl radical having at most 12 carbon atoms, optionally substituted, advantageously selected from methyl; ethyl; propyl, advantageously isopropyl; and butyl, preferably tert-butyl; a linear or branched alkylene radical having at most 12 optionally substituted carbon atoms, a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, advantageously chosen from methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, preferably tert-butoxy; OH, COOR ₁₃ wherein R ₃ is as defined in claim 12, CF ₃ , halogen selected from F, Cl, Br and I, said substituents R ₅ and R ₁₆ being positioned in the ortho, meta or para position of the ring, advantageously in meta and para positions,

R ₅ and R ₁₆ being advantageously chosen from a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, especially methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, preferably tert-butoxy; and oh,

R-17 represents a linear or branched alkyl radical having at most 12 carbon atoms, advantageously an alkyl group chosen from methyl, ethyl, propyl, advantageously isopropyl and butyric, advantageously fert-butyl, in particular methyl,

comprising the step of contacting a compound of formula (IIa)

with an adduct according to one of claims 1 to 8.

The process according to claim 12, wherein the compound has the following formula (IIIll):

in which R ₁₅ and R ₁₆ , independently of one another, represent a linear or branched alkoxy radical having at most 12 optionally substituted carbon atoms, especially methoxy; ethoxy; propoxy, advantageously isopropoxy; and butoxy, preferably tert-butoxy; or oh,

R ₁₇ represents a linear or branched alkyl radical having at most 12 carbon atoms, advantageously chosen from methyl; ethylie; propyl, advantageously isopropyl; and butyl, advantageously ierf-butyl; especially methyl. comprising the step of contacting a compound of formula (Mal)

with an adduct according to one of claims 1 to 8.

14. Process for preparing a compound of formula (II ib) below:

in which: represents a single bond or a double bond,

R ₁₄ represents hydrogen, a linear or branched alkyl radical having at most 11 carbon atoms, linear or branched alkylene having at most 11 carbon atoms, in particular a linear alkyl radical having at most 11 carbon atoms or a COOR ₁₃ group such that defined in claim 12, advantageously in which R ₁₃ represents a linear or branched alkyl radical having at most 12 carbon atoms, in particular a methyl radical; ethylie; propyl, advantageously isopropyl; and butyric, preferably tert-butyl. comprising the step of contacting a compound of formula (IIb)

with an adduct according to one of claims 1 to 8.

15, Process for preparing a dialkyl ether of the following formula (V)

wherein R1 ₈ and R19 independently of one another aikyle a linear or branched radical having at most 11 carbon atoms, optionally substituted or R1 ₈ and R ₉ are linked together to form a saturated or unsaturated cycioalkyle having 3-7 carbon atoms and optionally having one or more heteroatoms selected from nitrogen, sulfur or oxygen, comprising the step of contacting a compound of formula (IV) below: with an adduct according to one of claims 1 to 8.

16. Process for preparing a dicycloalkylether of the following formula (Va)

comprising the step of contacting a cyclic ketone of formula (IVa) as follows:

with an adduct according to one of claims 1 to 8.