EP1753707A1

EP1753707A1 - Method of reducing a functional group in an oxidised form

Info

Publication number: EP1753707A1
Application number: EP05759985A
Authority: EP
Inventors: Gérard Mignani; Mikaël BERTHOD; Marc Lemaire
Original assignee: Centre National de la Recherche Scientifique CNRS; Rhodia Chimie SAS
Current assignee: Centre National de la Recherche Scientifique CNRS; Rhodia Chimie SAS
Priority date: 2004-04-23
Filing date: 2005-04-20
Publication date: 2007-02-21
Also published as: FR2869313B1; WO2005110948A1; US20080214857A1; FR2869313A1; CA2563928A1; JP2007533711A; CN1968914A

Abstract

A novel method of reducing a functional group in an oxidised form. The invention relates more particularly to the reduction of aldehyde, ketone, ester, lactone, nitrile or phosphine oxide groups. The reduction method according to the invention is characterised in that it comprises exposing the substrate including the functional group to be reduced to the presence of a siloxane-type compound of the following formula (I), combined with a Lewis acid-type catalyst. In said formula (I): - R1 and R2, which are the same or different, are an alkyl, cycloalkyle or aryl group, - X is a digit from 0 to 50.

Description

METHOD FOR REDUCING AN OXIDIZED FUNCTIONAL GROUP.

The present invention relates to a new process for the reduction of a functional group in oxidized form. The invention applies more particularly to the reduction of aldehyde, ketone, ester, lactone, nitrile, phosphine oxide groups. The reduction of a functional group is a very important reaction in the field of Organic Chemistry. Thus, the reduction of phosphine oxides to phosphine has been widely described. Aluminum and lithium hydride is often recommended and in particular by Kawakami, Y. et al (Synt. Commun, 1983, 13, 427-434). However, this reagent is not easy to handle because it is dangerous. A new triethyoxysilane / titanium isopropoxide (IV) system has been described by Buchwald (JACS 1991, 113, 5093) but triethoxysilane is not an ideal reagent because it is very toxic and dangerous. Coumbe, T. et al (Tetrahedron Letters 1994, 35, 625-628) have described an alternative which consists in using a polymethylhydrosiloxane (PMHS). Admittedly, the latter is an inexpensive, non-volatile and less toxic reagent but it requires the use of a large excess of titanium (IV) isopropoxide (100 mol%) and the implementation on an industrial scale is difficult due to gel formation. Concerning the reduction of carbonylated functional groups, such as aldehydes, ketones, esters or lactones, it is known according to WO 96/12694 to use a silane derivative and a metal hydride, the latter being obtained in situ or ex situ from a metal salt or complex by reaction with a reducing agent. As silane agents, trialkylsilanes, dialkylsilanes, trialkoxysilanes and polymethylhydrosiloxane (PMHS) are recommended. The disadvantage of the process described is also to use hydride type reducers: lithium hydride, sodium, potassium hydride, boron hydride, metallic borohydride, aluminum hydride or organomagnesium or organolithium which are not easily handled because highly reactive and dangerous. The objective of the present invention is to provide a method which overcomes the aforementioned drawbacks.

It has now been found, and this is what is the subject of the present invention, a process for the reduction of an oxidized functional group present in a substrate, to a lower degree of oxidation, characterized in that it comprises the placing the substrate in the presence of a siloxane type compound corresponding to the following formula (I) associated with an effective amount of a Lewis acid type catalyst.

in said formula: - Ri, R ₂ , identical or different, represent an alkyl, cycloalkyl, aryl group, - x is a number ranging from 0 to 50.

In the context of the invention, the term "alkyl" means a linear or branched hydrocarbon chain having from 1 to 10 carbon atoms and preferably from 1 to 4 carbon atoms. Examples of preferred alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl. By “cycloalkyl” is meant a cyclic, monocyclic hydrocarbon group comprising 5 or 6 carbon atoms, preferably a cyclopentyl or cyclohexyl group. By "aryl" is meant an aromatic mono- or polycyclic group, preferably mono- or bicydic comprising from 6 to 12 carbon atoms, preferably phenyl. The siloxane type compounds which are used in the process of the invention correspond to formula (I) in which R 1 and R ₂ are identical and more particularly represent an alkyl group having from 1 to 4 carbon atoms. Ri and R ₂ preferably represent a methyl group. As regards x, it is preferably between 0 and 10 and even more preferably equal to 0 or 1. Among the compounds of formula (I), the one which is preferred is the following: CH "3, C" H '3, H— Si O Si —H CH ", 3 C ~ H-' 3, known by the abbreviation T DS, tetramethyldisiloxane.

In accordance with the process of the invention, the reduction of various functional groups is carried out and very particularly the following: - functional groups comprising a carbonyl group such as: aldehyde, ketone, carboxylic acid, ester, amide; - functional groups comprising a nitrogen atom such as nitrile, imine, nitro, nitrogen oxide; - functional groups comprising a sulfur atom such as sulfoxide, sulfone; - functional groups comprising a phosphorus atom such as a phosphine oxide or sulfide. The various groups mentioned above can be carried by an aliphatic chain or a cycle but it is also possible that it is included in a cycle such as, for example, a cyclic ketone, a lactone or a lactam. Thus, symbolically, the different substrates comprising the functions capable of being reduced can be represented as follows: R— Ç = O -R,

R; O R- C ≈ O T- C -N \ R, R, H OR, (I) (II) (III) O (IV)

O

R- S = O R— S = O R.

in said formulas, - Ri to Rs represent a hydrocarbon group having from 1 to 20 carbon atoms, - R ₃ , R and R5 also represent a hydrogen atom, - at most one of the groups R ₆ , R ₇ and Rs represent a hydrogen atom, - Ri and R ₂ , R-, and R ₅ , R ₆ and R _7, Rγ and R ₈ , R ₆ and R _8, can be linked together to form a ring. It should be noted that the substrate can be mono- or polyfunctional (most often bifunctional). Thus, the same function may be present several times (for example, diketone, diphosphine in the form of dioxide or disulfide) or functions of different nature (for example nitrile and phosphine oxide function). In said formulas (I) to (XII), R _t and R2 represent a hydrocarbon group of any kind. In the present text, preferred meanings will be specified but without any limiting character. More specifically, Ri and R ₂ represent a hydrocarbon group having from 1 to 20 carbon atoms which may be a saturated or unsaturated, linear or branched acyclic aliphatic group; a saturated, unsaturated or aromatic, monocyclic or polycyclic carbocyclic or heterocyclic group; a saturated or unsaturated, linear or branched aliphatic group, carrying a cyclic substituent. Ri and R ₂ preferably represent a linear or branched acyclic aliphatic group preferably having from 1 to 12 carbon atoms, saturated The invention does not exclude the presence of another unsaturation on the hydrocarbon chain such as one or more double bonds which can be conjugated or not or else a triple bond. The hydrocarbon chain can be optionally interrupted by a heteroatom (for example, oxygen or sulfur) or by a functional group insofar as the latter does not react and mention may in particular be made of a group such as in particular ether or alcohol . The hydrocarbon chain may optionally carry one or more substituents insofar as they do not react under the reaction conditions and there may be mentioned in particular a halogen atom, a trifluoromethyl group. The acyclic, saturated or unsaturated, linear or branched aliphatic group may optionally carry a cyclic substituent. By cycle is meant a carbocyclic or heterocyclic, saturated, unsaturated or aromatic cycle. The acyclic aliphatic group can be linked to the ring by a valential bond, a heteroatom or a functional group such as oxy, carbonyl, carboxy, sulfonyl, etc. As examples of cyclic substituents, cycloaliphatic, aromatic or heterocyclic substituents can be considered, in particular cycloaliphatics comprising 6 carbon atoms in the ring or benzene, these cyclic substituents themselves being optionally carriers of any substituent insofar as they do not interfere with the reactions involved in the process of the invention. Mention may in particular be made of alkyl or alkoxy groups having from 1 to 4 carbon atoms. Among the linear or branched aliphatic groups, particular mention is made of alkyl groups having from 1 to 10 carbon atoms. Among the aliphatic groups carrying a cyclic substituent, consideration is more particularly given to aralkyl groups having from 7 to 12 carbon atoms, in particular benzyl or phenylethyl. In the formulas, Ri and R ₂ can represent a carbocyclic, monocyclic group. The number of carbon atoms in the ring can vary widely from 3 to 8 carbon atoms but it is preferably equal to 5 or 6 carbon atoms. The carbocycle can be saturated or comprising 1 or 2 unsaturations in the cycle, preferably from 1 to 2 double bonds. As preferred examples of groups R 1 and R ₂ , mention may be made of cyclohexyl or cyclohexene-yl groups. Ri and R ₂ can also represent, independently of one another, a polycyclic hydrocarbon group consisting of at least 2 saturated and / or unsaturated carbocycles or by at least 2 carbocycles, only one of which is aromatic and forms between them ortho- or ortho- and pericondensed systems. Generally, the cycles are in C ₃ to Ce, preferably in C _e . As more specific examples, mention may be made of the bomyl group or the tetrahydronaphthalene group. R 1 and R ₂ may represent an aromatic carbocyclic group, having from 4 to 8 carbon atoms, preferably a phenyl group. Ri and R ₂ can also represent a polycyclic aromatic carbocyclic group; the cycles being able to form between them systems ortho-condensed, ortho- and peri-condensed. Mention may more particularly be made of a naphthalene group. In the case where Ri and R represent a carbocyclic, monocyclic, saturated or unsaturated group, it is possible that one or more of the carbon atoms of the ring are replaced by a heteroatom, preferably oxygen, nitrogen or sulfur or by a functional group, preferably carbonyl or ester, thus leading to a heterocyclic, monocyclic compound. The number of atoms in the ring can vary widely from 3 to 8 but it is preferably equal to 5 or 6 atoms. Ri and R ₂ can also represent a polycyclic aromatic heterocyclic group defined as being either a group consisting of at least 2 aromatic or non-aromatic heterocycles containing at least one heteroatom in each cycle and forming between them ortho- or ortho- and pericondensed systems or either a group consisting of at least one aromatic or non-aromatic hydrocarbon ring and at least one aromatic or non-aromatic heterocycle forming between them ortho- or ortho- and pericondensed systems. As examples of groups R 1 and R ₂ of heterocyclic type, there may be mentioned, inter alia, the furyl, thienyl, isoxazolyl, furazannyl, isothiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrannyl and quinolyl, napthyridinyl, benzopyrannyl, benzofurannyl groups. . It should be noted that if the groups Ri and R ₂ comprise any cycle, it is possible that this cycle carries a substituent. The nature of the substituent is arbitrary insofar as it does not interfere with the desired product. The substituents most often carried by the ring are one or more alkyl or aikoxy groups preferably having from 1 to 4 carbon atoms, preferably methyl or methoxy, an alkenyl group, preferably an isopropene-yl group, an atom of halogen, preferably chlorine or bromine, a trihalomethyl group, preferably trifluoromethyl and functional groups more particularly nitrile or ester (preferably lower C ₁ -C ₄ alkyl). Among all the groups Ri and R ₂ mentioned above, Ri and R ₂ preferably represent a phenyl group optionally carrying an alkyl or aikoxy group having from 1 to 4 carbon atoms, a trifluoromethyl group. Ri and R ₂ may be linked by a saturated or unsaturated aliphatic chain so as to constitute a carbocycle or a heterocycle having from 3 to 20 atoms, saturated, unsaturated, monocyclic or polycyclic comprising two or three rings: the adjacent rings may be of a nature aromatic. In the case of polycyclic compounds, the number of atoms in each cycle preferably varies between 3 and 6. R 1 and R ₂ can form an alkylene or alkenylene chain having from 4 to 6 atoms and preferably 5 carbon atoms. In this case, a cyclic ketone corresponding to formula (II) is obtained, a lactone for formula (III) and a lactam for formula (IV). It is also possible for formulas (IX) and (X) that the sulfoxide and sulfone group are also included in a cycle. Concerning the groups R ₃ , R ₄ and R 5, they represent a hydrogen atom or an alkyl, alkenyl, aryl, arylalkyl group. As regards RΘ R7, Rs, it is more particularly an alkyl, alkenyl, aryl, arylalkyl group. Examples of substrates capable of being reduced are given below. As examples of aldehyde type substrates and illustrated by formula (I), mention may be made of saturated aldehydes such as butanal, pentanal, hexanal, heptanal, octanal, decanal, dodecanal; unsaturated aldehydes such as acrolein, methacrolein, crotonaldehyde, prenal, citral, retinal, campholenic aldehyde, cinnamic aldehyde, hexylcinnamic aldehyde, formylpinane and nopal; aromatic aldehydes such as benzaldehyde, salicylic aldehyde, vanillin, veratraldehyde. As examples of ketones corresponding to formula (11), mention may in particular be made of hexan-2-one, octan-2-one, nonan-4-one, dodecan-2-one, methylvinyl ketone, l mesityl oxide, acetophenone, cyclopentanone, cyclohexanone, cyclododecanone, cyclohex-1-en-3- one, isophorone, oxyphorone, carvone and camphor. As examples of substrates illustrating formula (III), mention may be made of acids and their ester derivatives (alkyl, preferably methyl or aryl) of the following acids: acetic, propionic, butyric, isobutyric, lactic, tartaric, benzoic acid , salicylic, p-hydroxybenzoic, vanillic, veratric, acrylic, methacrylic, crotonic, hexenoic, fumaric, citraconic, cinnamic. Mention may also be made of saturated fatty acids such as lauric, myristic, palimitic, stearic and sebacic acid; unsaturated fatty acids and more particularly unsaturated fatty acids having a single double bond such as linderic acid, myristoleic acid, palmitoleic acid, oleic acid, petroselenic acid, doeglic acid, gadoleic acid, erucic acid; unsaturated fatty acids having two double bonds such as linoleic acid; unsaturated fatty acids having 3 double bonds such as linolenic acid; unsaturated fatty acids having more than 4 double bonds such as isanic acid, stearodonic acid, arachidonic acid, chypanodonic acid; the unsaturated fatty acids carrying a hydroxyl group such as ricinoleic acid and their mixtures With regard to the amides of formula (IV), there may be mentioned in particular N-alkyl- or N-benzylcarboxamides such as in particular N-ethylacetamide, N-benzylacetamide. The lactones used as starting substrates are more particularly the lactones having from 3 to 12 carbon atoms, in the cycle, preferably, γγ-valerolactone or 4-methylbutyrolactone, δδ- valerolactone or 2-methylbutyrolactone, εδ -valerolactone, ωδ- valerolactone, 3-ethylpropiolactone, 2-ethylpropiolactone, 2,3-dimethyllactone, caprolactone, 12-dodecanelactone. As lactams, mention may be made of lactams having 3 to 12 atoms in the ring and more particularly caprolactam, δδ-valerolactam, εδ-valerolactam, γδ-valerolactam, ωδ-valerolactam, 11- undecalactam and 12 -dodécanelactame. As examples of substrates corresponding to formula (V), mention may especially be made of alphatic or aromatic nitriles, preferably acetonitrile, propionitrile, butanenitrile, isobutanenitrile, pentanenitrile, 2-methylglutaronitriy, adiponitrile, benzonitrile, tolunitrile, malonitrile, 1, 4-benzonitrile. The process of the invention is entirely suitable for effecting the reduction of phosphine oxides or diphσsphine oxides: whether the phosphines are chiral or not. Examples of phosphine oxides which can be reduced according to the invention are given below, examples which are not limiting insofar as the process of the invention applies to any substrate comprising the group

- P = O

As phosphine oxides capable of being reduced, there may be mentioned in particular those of formula:

in said formula: - q is equal to 0 or 1. the groups R ₆ , R7, Rs, R9, identical or different, represent:. an alkyl group having from 1 to 12 carbon atoms,. a cycloalkyl group having 5 or 6 carbon atoms,. a cycloalkyl group having 5 or 6 carbon atoms, substituted by one or more alkyl groups having 1 to 4 carbon atoms, aikoxy having 1 or 4 carbon atoms,. a phenylalkyl group of which the aliphatic part contains from 1 to 6 carbon atoms,. a phenyl group,. a phenyl group substituted by one or more alkyl groups having 1 to 4 carbon atoms or aikoxy group having 1 to 4 carbon atoms, one or more halogen atoms, a trifluoromethyl group or by a solubilizing group, the group R ₁₀ represents :. a valential bond or a divalent, linear or branched, saturated or unsaturated hydrocarbon group having from 1 to 6 carbon atoms,. an aromatic group of formula:

in which: + Z represents an alkyl group having from 1 to 10 carbon atoms, a halogen atom or a trifluoromethyl group, _* X an oxygen, sulfur atom or a linear or branched alkylene group having from 1 to 3 carbon atoms, _* if r is equal to 1, X 'represents a valential bond, an oxygen, sulfur or silicon atom or a linear or branched alkylene group having from 1 to 3 carbon atoms, "if r is equal to 0, the two rings are not linked, carbon atoms, It is also possible that at least one of the three hydrocarbon groups linked to phosphorus carries a solubilizing group S which may be one or more hydroxyl groups and or anionic functional groups, in particular SO ₂ W, SO3W or COOW in which W represents a hydrogen atom or an alkali metal, preferably sodium, a phosphonate group or an ammonium group N ⁺ R3 or phosphonium P ⁺ 3 in which R groups represent most often an alkyl group having 1 to 4 carbon atoms or a benzyl group. As examples of phosphine oxides, there may be mentioned, without limitation: phosphine oxides derived from the following phosphines: tricyclohexylphosphine, trimethylphosphine, triethylphosphine, tri-π-butylphosphine, triisobutylphosphine, tri-terf- butylphosphine, tribenzylphosphine, dicyclohexylphenylphosphine, triphenylphosphine, dimethylphenylphosphine, diethylphenylphosphine, d \ -tert- butylphenylphosphine, tri (p-tolyl) phosphine, isopropyldiphenylphenophosphine triphenylphosphine) tolyl) phosphine, bis-diphenylphosphinomethane, bis-diphenylphosphinoethane, bis-diphenylphosphinopropane, bis-diphenylphosphinobutane, bis-diphenylphosphinopentane, bis - [(2-diphenylphosphino) phenyl] ether

(DPEPHOS), 4,5-bis (diphenylphosphino) -9,9-dimethylxanthene (XANTPHOS), sodium triphenylphosphinotrimetasulfonate (TPPTS). Another type of phosphine oxides capable of being reduced are those which correspond to the formula (Xlb) and which are partly described in WO-A 00/52081:

(Xlb) in which: - An, Ar ₂ independently represent a saturated or unsaturated, linear or branched aliphatic hydrocarbon group; a saturated, unsaturated or aromatic carbocycle; - Ru, R ₁ 2 independently represent a hydrogen atom; a group Z; or a group -XZ where X represents O, S or -NT; and - Z and T are independently chosen from a saturated aliphatic hydrocarbon group optionally interrupted by O, S and / or N; a saturated, unsaturated or aromatic carbocyclic group; or a saturated aliphatic hydrocarbon group substituted by one or more saturated, unsaturated or aromatic carbocyclic groups, in which the aliphatic group is optionally interrupted by O, S and or N; it being understood that T can also represent a hydrogen atom; or - Two groups Ru and R ₁₂ attached to the same phenyl ring together form an unsaturated or aromatic carbocycle, or else together form an unsaturated or aromatic heterocycle. In the context of the invention, the term “saturated or unsaturated, linear or branched aliphatic hydrocarbon group” means a linear or branched group, saturated or unsaturated, optionally substituted, of C1-C25, preferably C ₁ -C-12 and by “carbocyclic group”, an optionally substituted monocyclic or polycyclic group, preferably of C ₃ -C ₅₀ and more preferentially of When the carbocyclic group comprises more than one cyclic nucleus (in the case of polycyclic carbocycles), the cyclic nuclei can be condensed (o- or pericondensed) two by two or linked two by two by σ bonds. The carbocyclic group can comprise a saturated part and / or an aromatic part and / or an unsaturated part. Examples of saturated carbocyclic groups are cycloalkyl groups. Preferably, the cycloalkyl groups are C ₃ -C 8, better still C ₃ ~ Cιo. Mention may in particular be made of the cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, adamantyl or norbornyl groups. The unsaturated carbocycle or any unsaturated part has one or more ethylenic unsaturations. It preferably has from 6 to 50 carbon atoms, better still from 6 to 20, for example from 6 to 18. Examples of unsaturated carbocycles are the cycloalkenyl groups in Examples of aromatic carbocyclic groups are the groups

(C ₆ -C-ι _δ ) aryl and in particular phenyl, naphthyl, anthryl and phenanthryl. By aliphatic hydrocarbon group is meant a linear or branched, saturated, optionally substituted, C1-C25 group, preferably C Cι ₂ and even more preferably Ci-Ce. The substituents of the carbocyclic groups (St1) can be saturated aliphatic hydrocarbon groups optionally interrupted by O, S and / or N or groups -XZ in which X and Z are as defined above. The substituents of the aliphatic hydrocarbon groups (St2) are saturated or unsaturated carbocyclic groups, themselves optionally substituted by one or more of the substituents (St1) defined above. Preferably, Ari and Ar ₂ independently represent (C ₃ - Cs) cycloalkyl or (C ₆ -Cι ₈ ) aryl, optionally substituted by one or more (Cι-C ₆ ) alkyl and or (Cι-C ₆ ) alkoxy; and Ru and R ₁₂ independently represent a hydrogen atom; (C ₃ -C ₈ ) cycloalkyl; (Cι-C ₆ ) alkyl; (Cι-C ₆ ) alkoxy or (C ₆ - C ₁₈ ) aryl, the cycloalkyl and aryl groups being optionally substituted by (Cι-C ₆ ) alkyl and / or (CC ₆ ) alkoxy. When Ru and R-ι ₂ together form an unsaturated carbocycle or heterocycle, the latter preferably has a single unsaturation which is that shared with the phenyl nucleus carrying the Ru and Rι _{2 groups} . The aromatic carbocycles which together form Ru and R ₁₂ are preferably as defined above. The unsaturated carbocycles which together form Ru and R ₁₂ are mono- or polycyclic, the definition of these terms being as proposed above. These carbocycles preferably comprise from 6 to 50 carbon atoms, better still from 6 to 20 carbon atoms. Examples are in particular C ₆ -C ₁₀ cycloalkenyl. By heterocycle is meant according to the invention mono- or polycyclic groups, and in particular mono-, bi- or tricyclic groups comprising one or more heteroatoms chosen from O, S and / or N, preferably 1 to 4 heteroatoms. When the heterocycle is polycyclic, it can consist of several condensed unicycles two by two (orthocondensed or pericondensed) and / or several monocycles attached two by two by σ bonds. Preferably, the unicycles or the unicycle constituting the heterocycle, has from 5 to 12 links, better still from 5 to 10 links, for example from 5 to 6 links. When Ru and R ₁₂ form a heterocycle, the latter comprises an unsaturated part and / or an aromatic part, it being understood that the unsaturated part preferably comprises a single double bond. Particularly preferred heterocycies are in particular pyridine, furan, thiophene, pyrrole, benzofuran and benzothiophene.

Within the scope of the invention, monocyclic or bicyclic carbocycles and heterocycies are preferred. According to the invention, when Ru and R ₁₂ together form a carbocycle or heterocycle, these can be optionally substituted by one or more substituents (St1) as defined above. It should be noted that the invention does not exclude that the two benzene rings present in the formula (Xlb) carry other substituents. As examples, we can refer to the definition of Xi and X ₂ given for the formula (Xlc). The phosphine oxides preferably used correspond to the formula (Xlb) in which: - Ar _i , Ar ₂ independently represent a (C ₁ -C ₆ ) alkyl group, preferably a t-butyl group; a saturated, unsaturated or aromatic monocyclic carbocycle optionally substituted by one or more (Cι-C ₆ ) alkyl or (Cι-C ₆ ) alkoxy groups and having from 3 to 8 carbon atoms; - Ru and R ₁₂ are independently chosen from a hydrogen atom, a (dC ₆ ) alkyl group or a (CrC ₆ ) alkoxy group; or - R ₁₁ and R ₁₂ together with the carbon atoms which carry them (i) a monocyclic or polycyclic, unsaturated or aromatic carbocycle having from 5 to 13 carbon atoms, or (ii) a monocyclic or polycyclic, unsaturated heterocycle or aromatic have from 4 to 12 carbon atoms and one or more heteroatoms chosen from O, S and N, said heterocycle and carbocycle being optionally substituted by one or more (CrC ^ alkyl or (CrCe ^ lcoxy. Even more preferably, An and Ar ₂ are identical and represent a phenyl group optionally substituted by one or more (Cι ~ C ₆ ) alkyl or (CrC ₆ ) alkoxy; or a (C ₄ -C ₈ ) cycloalkyl group optionally substituted by one or more groups (CrCβ) alkyl. An and Ar ₂ are identical and represent cyclohexyl, phenyl or tolyl. R-π and R ₁₂ are independently chosen from a hydrogen atom, (Cr C ₆ ) alkyl or (Cι-C ₆ ) alkoxy or Ru and Rι ₂ together the with the carbon atoms which carry them a cyclohexenyl, with a single unsaturation optionally substituted by one or more (Cι-C ₆ ) alkyl or (CrC ₆ ) alkoxy; or phenyl optionally substituted by one or more (Cι-Ce) alkyl or (Ci- CeJalcoxy. As examples of phosphine oxides capable of being reduced, a first group of preferred compounds consists of the compounds of formula (Xlb) for which Ru and Rι ₂ are a hydrogen atom, a group (C

C ₆ ) alkyl (preferably methyl), or a group (CrC ₆ ) alkoxy (preferably methoxy). We can cite in particular: A second group of preferred compounds consists of the compounds of formula (Xlb) for which Ru and R ₂ together form (C ₃ -Cn) cycloalkenyl optionally substituted, (C ₆ -Cιo) aryl optionally substituted or (C - C ₈ ) heteroaryl comprising 1 or 2 endocyclic heteroatoms, said heteroaryl being optionally substituted. Ru and Rι ₂ together represent an optionally substituted phenyl group or a cycloalkenyl group. Thus, are particularly concerned, the oxides of diphosphine whose naphthyl groups are substituted in position 4,4 'or 5,5' or 6,6 'by atoms or functional groups and which can be represented by the following formula:

- R ₁₃ , R ₁₄ , identical or different, represent a hydrogen atom or a substituent, - An and Ar ₂ independently represent an alkyl, alkenyl, cycloalkyl, aryl, arylalkyl group, - X _{1 (} X ₂ , identical or different , represent:. an R, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, arylalkyl group,. an alkyl group substituted by one or more halogen atoms, preferably fluorine or by nitro or amino groups,. an atom d halogen selected from bromine, chlorine or iodine. -OH,. -OR _a,. -O-COR _group,. -SR _a,. -SO ₃ M . a -CN group,. a group derived from the nitrile group such as:. a group -CH ₂ -NH ₂ ,. a group -COOH,. a group derived from the carboxylic group such as:. a group -COOR _a ,. a group -CH ₂ OH,. a group -CO-NH-R,. a group derived from the aminomethyl group such as:. a group -CH ₂ -NH-CO-R,. a group -CH ₂ -NH-CO-NH-R _b ,. a group -CH ₂ -N = CH-R _a ,. a group -CH ₂ -NH ⁺ ,. a group comprising a nitrogen atom such as:. an NH ₂ group. a group -NHR _a ,. a group -N (R _a ) ₂ ,. a group -N = CH-R _a ,. a group -NH-NH ₂ ,. a group -N≡N ⁺ ≡N ^" , a magnesium or lithium atom, in the different formulas, R _a represents an alkyl, cycloalkyl, arylalkyl, phenyl group and R _b has the meaning given for R _a and also represents a naphthyl group and M represents a metal cation, preferably alkaline, in particular sodium. In the formula (Xlc), the term "alkyl" means a linear or branched hydrocarbon chain in C 1 and preferably in C-MO. Examples of preferred alkyl groups are in particular methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl. By "alkenyl" is meant a hydrocarbon group, linear or branched in

C ₂ - ₁₅ comprising one or more double bonds, preferably 1 to 2 double bonds. By "alkynyl" is meant a hydrocarbon group, linear or branched at C ₂ - ₁₅ , comprising one or more triple bonds, preferably 1 triple bond. By "cycloalkyl" is meant a cyclic, monocyclic C ₃ - ₈ hydrocarbon group, preferably a cyclopentyl or cyclohexyl or polycyclic (bi- or tricyclic) C ₄ - _{18 group} , in particular adamantyl or norbornyl. By "aryl" is meant a mono- or polycyclic aromatic group, preferably mono- or bicydic in C6 _-2 o, preferably phenyl or naphthyl. When the group is polycyclic, that is to say that it comprises more than one cyclic nucleus, the cyclic nuclei can be condensed two by two or attached two by two by σ bonds. Examples of (C ₆ -Cιs) aryl groups are in particular phenyl, naphthyl, anthryl and phenanthryl. By "arylalkyl" means a hydrocarbon group, linear or branched carrying a monocyclic aromatic ring in C _7- ι ₂ , preferably benzyl. The different groups ^ and X2 are advantageously in the 6.6 'or 5.5' or 4.4 'position. As examples of substrates, mention may be made of the oxides corresponding to the diphosphines substituted in position 6 and 6 ′ and which are described in patents WO-A 00/49028 and WO-A 01/74828. For the oxides of diphosphines substituted in position 5 and 5 ', reference may be made to those corresponding to the diphosphines described in applications FR-03/04392 and FR-02/16086 For the oxides of diphosphines substituted in position 4 and 4', reference may be made to those corresponding to the diphosphines described in applications FR-03/04391 and FR-02/16087. The process is particularly applicable to diphosphine oxides which have one or two nitrile groups because there is both a reduction of the nitrile groups and of the diphosphine oxide function. Examples of said diphosphine oxides are given.

(with w between 1 and 5) The invention is particularly applicable to BINAP, namely 2,2'-bis (diphenylphosphino) -1, 1'-binaphthyle and its derivatives substituted in position 6 and 6 ', 5 and 5' or 4 and 4 ' . The method of the invention is also suitable for diphosphine oxides corresponding to the following formula: Ri5Rι ₆ OP-A-POR ₁₅ Ri6 (Xld) in which: - A represents a saturated divalent aliphatic hydrocarbon group; a divalent saturated or aromatic carbocyclic group; or a saturated divalent aliphatic hydrocarbon group interrupted by a saturated or aromatic divalent carbocyclic group; - R ₁₅ and Ri ₆ are different and represent a saturated aliphatic hydrocarbon group; an aromatic or heterocyclic aromatic carbocyclic group. Saturated aliphatic hydrocarbon groups, aromatic carbocyclic and heterocyclic groups representing R ₁ 5 and Rι ₆ are as defined above. They can be substituted by one or more substituents -Z or -XZ in which X and Z are as defined above. In the formula (Xld), the different symbols represent more particularly: - A represents a CC ₆ alkylene chain optionally substituted by one or more (CC ₆ ) alkoxy, d CrC 4 alkylamino or (CC ₆ ) alkylthio groups; a (C ₃ -C ₈ ) cycloalkylene group optionally substituted by one or more (CC ₆ ) alkoxy, di (CC ₆ ) alkylamino or (CC ₆ ) alkylthio groups; an (C ₆ -Cι ₀ ) arylene group optionally substituted by one or more (C C6) alkoxy, di (Cι-C ₆ ) alkylamino or (CC ₆ ) alkylthio groups; or a group - (CH ₂ ) _r B "- (CH ₂ ) _r where j represents an integer from 1 to 3 and B" represents (C ₃ -C ₈ ) cycloalkylene optionally substituted by one or more (Cι-C ₆ ) alkoxy, di (Cι-C ₆ ) alkylamino or (CC ₆ ) alkylthio or (C ₆ -Cι ₀ ) arylene optionally substituted by one or more (C ₁ -C ₆ ) alkoxy, di (Cι-C ₆ ) alkylamino or (Cι-C ₆ ) alkylthio; - R ₁₅ and Rie are different and represent an aromatic monocyclic heterocycle having from 3 to 7 carbon atoms and one or more heteroatoms chosen from O, N and S; an (C ₆ -C ₁₀ ) aryl group, said heterocycle and said aryl group being optionally substituted by one or more (CrC ₆ ) alkyl or (C ₁ -C ₆ ) alkoxy groups; or (Cι-C ₆ ) alkyl optionally substituted by one or more (Cι-C ₆ ) alkoxy. Even more preferably, A represents ethylene and R ₁₅ and Rie are independently chosen from phenyl optionally substituted by one or more (CC ₆ ) alkyl or (CrC ₆ ) alkoxy. A more specific example is given below:

Another type of substrate which can be reduced are those which correspond to the following formula:

(Ar ₃ ) ₂ OR_ (CH ₂ ) i (CH ₂ ) i— _PO (Ar ₃ ) ₂ *. ^* _{(χ | e)} in which: - * denotes an asymmetric center; - i represents 0 or 1; - R ₁₇ and R18 independently represent a hydrogen atom or a saturated aliphatic hydrocarbon group, or alternatively the Rι ₈ groups are as defined above and the groups R ₁₇ together form a saturated divalent aliphatic hydrocarbon chain optionally interrupted by two groups X, X being as defined above for the formula (Xlb), preferably by two identical groups X; - B represents a bond or is as defined above for A in the formula (Xld); - Ar ₃ is as defined above for R ₁₅ and Rie- In the formula (Xle), the different symbols represent more particularly: - R ₁₇ and Ris are independently chosen from a hydrogen atom and a group (Cι- Ce) alkyl; or else the two groups R-ι ₇ together form a chain (CrC _δ Jalkylene possibly interrupted by two oxygen or sulfur atoms, and Ris is as defined above; - B represents a bond or else is as defined above for A; - Ar ₃ represents an aromatic monocyclic heterocycle having from 3 to 7 carbon atoms and one or more heteroatoms chosen from O, N and S; a (C ₆ -Cι ₀ ) aryl group, said heterocycle and said aryl group being optionally substituted by one or more (Cι-C _ô ) alkyl or (Cι-C ₆ ) alkoxy groups, or (Cι-C ₆ ) alkyl optionally substituted by one or more (C-ι_C ₆ ) aIcoxy. more preferably, Ar ₃ represents a phenyl group optionally substituted by one or more (Cι-C ₆ ) alkyl or (Cι-Cβ) alkoxy, examples of said diphosphine oxides are given.

where Ph represents phenyl, or one of the enantiomeric forms of these structures. Another type of substrate which can be reduced are those which correspond to the following formula:

in which: - D is as defined above for A in the formula (Xld); - Fi and F ₂ are identical and represent a saturated aliphatic hydrocarbon group, said group carrying at least one chiral center; a saturated carbocyclic group carrying at least one chiral center; or - Fi and F ₂ together form a saturated divalent aliphatic hydrocarbon chain, optionally interrupted by two groups X, X being as defined above for the formula (Xlb); two of the carbons of said chain constituting asymmetric centers. In the formula (Xlf), the different symbols represent more particularly: - D represents a Cι-C ₆ alkylene chain optionally substituted by one or more (Cι-Ce) alkoxy, di (C ₁ -C ₆ ) alkylamino or ( Cl-C ₆ ) alkylthio; a (C ₃ -C ₈ ) cycloalkylene group optionally substituted by one or more (Cι-C ₆ ) alkoxy, di (Cι-C ₆ ) alkylamino or (C ^ Ce) alkylthio groups; a group (C ₆ -Cι ₀ ) arylene optionally substituted by one or more groups (Ci-CβJalcoxy, di (Cι-C ₆ ) alkylamino or (Ci- C _δ jalkylthio; or a group - (CH2) jB "- (CH2 ) j- where j represents an integer between 1 and 3 and B "represents (C ₃ -C ₈ ) cycloalkylene (optionally substituted by one or more (Cι-C ₆ ) alkoxy, di (Cι- C ₆ ) alkylamino or (Cι-C ₆ ) alkylthio) or (C ₆ -Cι ₀ ) arylene (optionally substituted by one or more (C ₁ -Ce) alkoxy, di (CC ₆ ) alkylamino or (CC ₆ ) alkylthio) groups; - Fi and F2 are identical and represent (Cι-Cβ) alkyl optionally substituted by one or more (CrCe) alkoxy, said alkyl group carrying at least one chiral center; (C ₃ -C ₈ ) cycloalkyl substituted by one or more (CrC ₆ ) alkoxy or (Cι-C ₆ ) alkyl, said cycloalkyl carrying at least one chiral center; or else Fi and F ₂ together form a chain (Ci- C _δ ) alkylene optionally interrupted by two oxygen or sulfur atoms, ladi the chain being substituted by one or more (C ₁ - Ce) alkyl or (Cι-Ce) alkoxy groups, two of the carbons of said chain constituting asymmetric centers. An example of diphosphine oxide corresponding to the formula (Xlf) is:

or some diastereoisomeric form. According to another embodiment of the invention, the diphosphine oxide corresponds to one of the following formulas:

Ph PO PO Ph (Xlh)

These compounds and their preparation methods are described in particular in application EP-A 1 064 244. According to yet another embodiment, the formula:

in which :

- Gi, G ₂ , G ₃ , G ₄ , G ₅ , identical or different, represent a hydrogen atom or a hydrocarbon group, optionally substituted, having from 1 to 40 carbon atoms which may be a saturated acyclic aliphatic group or unsaturated, linear or branched; a saturated, unsaturated or aromatic, monocyclic or polycyclic carbocyclic or heterocyclic group; a saturated or unsaturated, linear or branched aliphatic group, carrying a cyclic substituent,

- G ₂ and G ₃ can form together with the carbon atoms which carry them, a saturated or unsaturated cycle,

- G ₅ can represent a type group in which Gù G ₂ 'and G ₃ ' have the same meaning as that given for Gi, G ₂ and G ₃ , - G ₄ and G ₅ cannot simultaneously represent a phenyl group. These compounds and their preparation methods are described in application EP-A 0 968 220. Examples of diphosphines corresponding to the formula (Xli) above are more precisely the following:

The amount of the compound of formula (I) to be used, expressed relative to the amount of the substrate to be reduced, is at least equal to the stoichiometry. Thus, the ratio between the number of moles of the substrate to be reduced and the number of moles of the compound of formula (I) can vary widely between 1 and 1000, preferably between 1 and 50. Intervenes in the process of the invention, a Lewis acid. In the present text, “Lewis acid” means a compound comprising a metallic or metalloid cation accepting electronic doublets, which reacts with the compound of formula (1). As metallic or metalloid cations suitable for the invention, mention may be made in particular of those of metallic or metalloid elements of groups (IVa), (Vlla), (Ib), (llb), (lllb) and (Vlll) of the periodic table elements. In this text, reference is made below to the Periodic Table of Elements published in the Bulletin of the Société Chimique de France, No. 1 (1966). By way of examples of cations that are well suited to the process of the invention, mention may be made more particularly of those of group (IVa), titanium, zirconium, hafnium; of the group (Vlla), manganese; of group (Ib), copper; from group (llb), zinc; from the group (IIIb) boron and aluminum; of the group (Vlll), iron, cobalt, nickel. Among the abovementioned cations, titanium is preferably chosen. As more specific examples of anions, mention may in particular be made of organic anions such as carboxylates, preferably acetate, propionate, benzoate: sulfonates preferably methanesulfonate, trifluoromethanesulfonate: alcoholates preferably methylate, ethylate, propylate, isopropylate; Tacétylacétonate. As regards inorganic anions, mention may in particular be made of chloride, bromide, iodide, carbonate. An organic anion is advantageously chosen. There may also be the presence of hydrocarbon groups by alkyl groups preferably having from 1 to 4 carbon atoms or cyclopentadienyl. As catalysts, use is preferably made of anhydrous compounds. Examples of compounds capable of being used in the process of the invention are given below: - iron compound:. iron (II) acetate. iron (II) acetylacetonate. iron bromide (H). iron bromide (III). iron (III) chloride. iron (III) ethoxide . iron i-propoxide (III). iron (III) stearate. iron (III) trifluoroacetylacetonate

- composed of cobalt:. cobalt (II) acetate. cobalt (II) acetylacetonate. bis (cyclopentadienyl) cobalt (II). cobalt (II) bromide. cobalt (II) chloride. cobalt (II) citrate. cobalt (II) cyclohexanebutyrate. Cobalt (II) 2-ethylhexanoate. (1R, 2R) - (-) - 1, 2-cyclohexanediamino-N, N'-bis (3,5-di-t-butylsalicylidene) cobalt (II) - nickel compound:. nickel (II) acetylacetonate. nickel (II) bromide. nickel (II) chloride. nickel (II) hexafluoroacetylacetonate - composed of titanium:. titanium bis (cyclopentadienyl) dichloride. titanium bis (ethylcyclopentadienyl) dichloride. titanium triisopropoxide chloride. titanium cyclopentadienyl trichloride. titanium pentamethylcyclopentadienyl trimethoxide. titanium bromide (IV). titanium n-butoxide (IV). titanium t-butoxide (IV). titanium (IV) chloride. titanium (di-i-propoxide) bis (acetylacetonate). titanium ethoxide. titanium (III) fluoride. titanium i-propoxide (IV)

- composed of zirconium:. bis (cyclopentadienyl) zirconium dichloride. bis (tretramethylcyclopentadienyl) zirconium dichloride. n-butyl dichloride (cyclopentanedienyl) of zirconium. cyclopentadienyl zirconium trichloride . zirconium (IV) acetylacetonate. zirconium n-butoxide (IV). zirconium t-butoxide (IV). zirconium n-propoxide (IV). zirconium (IV) trifluoroacetylacetonate

- composed of hafnium:. hafnium (IV) acetylacetonate. hafnium bromide (IV). hafnium (IV) t-butoxide. hafnium (IV) chloride. hafnium ethoxide (IV). hafnium (IV) monoisopropylate propoxide

- composed of boron:. boron bromide. tri-n-amylborate. tri-n-butylborate

- composed of copper:. copper (II) acetate,. copper (II) acetylacetonate. copper (II) bromide. copper (II) ethylacetoacetate. copper (II) ethylhexanoate. copper (II) fluoride. copper (II) formate. copper (II) oxalate. copper (II) tartrate. copper (II) trifluoroacetylacetonate. copper (II) trifluoromethanesulfonate

- composed of aluminum:. aluminum ethoxide. aluminum fluoride. aluminuim hexafluoroacetylacetonate. aluminuim i-propoxide

- composed of zinc:. zinc acetate. zinc acetylacetonate. zinc bromide. zinc chloride . zinc cyclohexanebutyrate. Zinc 2-ethylhexanoate. zinc fluoride. zinc iodide. zinc trifluoromethanesulfonate - manganese compound:. bis (cyclopentadienyl) manganese. bis (ethylcyclopentadienyl) manganese. bis (pentanemethylcyclopentadienyl) manganese. bis (i-propylcyclopentadienyl) manganese. bis (tetramethylcyclopentadienyl) manganese. chloride ^" / f?, 2r? J - (-) - [1, 2-cyclohexanediamino-N, N'-bis (3,5-di-t-butylsalicylidene)] manganese (III). (7S chloride, 2SJ - (+) - [1, 2-cyclohexanediamino-N-N'-bis (3,5-di-t-butylsalicylidene)] manganese (lll). Cyclopentadienyl manganese tricarbonyl. Manganese acetylacetonate (lll). Manganese bromide (II). Manganese carbonate (II). Manganese chloride (II). Manganese cyclohexanebutyrate (II). Manganese 2-ethylhexanoate (II). Manganese fluoride (II). Manganese iodide (II). Pentacarbonyl bromide manganese phthalocyanine (lll) tricarbonylmethylcyclopentadienylmanganese As more specific examples of Lewis acids, we can mention titanium isopropoxide or zinc trifluoroacetate The amount of catalyst used expressed by the ratio between the number of moles of Lewis acid and the number of moles of substrate to be reduced varies between 0.1 and 1, preferably around 0.5.

The process of the invention is preferably carried out in an organic solvent. It is also possible that one of the excess reactants serves as a reaction solvent. A solvent is used which is inert under the reaction conditions and which preferably solubilize the reactants. Advantageously, the solvent is chosen so that its boiling point is high (preferably greater than 80 ° C.). As examples of organic solvents suitable for the invention, there may be mentioned in particular aliphatic, cycloaliphatic or aromatic hydrocarbons, halogenated or not; ethers and alcohols. By way of nonlimiting examples of solvents, mention may be made of: - aliphatic and cycloaliphatic hydrocarbons, more particularly paraffins such as, in particular, hexane, heptane, octane, isooctane, nonane, decane, undecane, tetradecane, petroleum ether and cyclohexane; aromatic hydrocarbons such as, in particular, benzene, toluene, xylenes, ethylbenzene, diethylbenzenes, trimethylbenzenes, cumene, pseudocumene, petroleum fractions made up of a mixture of alkylbenzenes, in particular Solvesso® type fractions, - aliphatic halogenated hydrocarbons or aromatic, and one can mention: perchlorinated hydrocarbons such as in particular trichloromethane, tetrachlorethylene; partially chlorinated hydrocarbons such as dichloromethane, dichloroethane, tetrachloroethane, trichlorethylene, 1-chlorobutane, 1,2-dichlorobutane; monochlorobenzene, 1, 2-dichlorobenzene, 1,3- dichlorobenzene, 1, 4-dichlorobenzene or mixtures of different chlorobenzenes, - aliphatic, cycloaliphatic or aromatic ether-oxides and, more particularly, methyl-tert- butyl ether, dipentyl oxide, diisopentyl oxide, dimethyl ether of ethylene glycol (or 1,2-dimethoxyethane), dimethyl ether of diethylene glycol (or 1,5-dimethoxy-3-oxapentane) or cyclic ethers, for example, dioxane, tetrahydrofuran, - aliphatic or cycloaliphatic alcohols more particularly, ethanol, isopropanol, butanol, isobutanol, hexanol, cyclohexanol, ethylene glycol. Toluene is advantageously chosen. The amount of organic solvent used is such that the concentration of the substrate is advantageously between 0.1 and 1 mol / liter, preferably around 0.5 mol / liter. In accordance with the process of the invention, the substrate to be reduced is brought into contact with the compound of formula (I), in the presence of the catalyst and preferably in an organic solvent. Regarding the temperature and pressure conditions, they are advantageously as described below. The reduction reaction is generally carried out at a temperature varying between room temperature and 150 ° C, preferably between 80 and 120 ° C. By ambient temperature is meant a temperature usually between 5 ° C and 25 ° C. The duration of the reduction can vary widely between 2 hours and 24 hours, depending on the amount of catalyst used and the reaction temperature. The process of the invention is carried out at atmospheric pressure but preferably under a controlled atmosphere of inert gases such as nitrogen or rare gases, for example argon. A pressure slightly higher or lower than atmospheric pressure may be suitable. As regards the practical embodiments of the invention, a preferred mode consists in charging the substrate to be reduced, the organic solvent, the catalyst of Lewis acid type, then the reducing compound of formula (I) is introduced. ). At the end of the reaction, the reduced product is recovered. Conventional means can be used for this purpose. If the reduced product is in liquid form, it is possible, for example, to treat the reaction medium at the end of the reaction using a basic solution in order to hydrolyze the hydrides which have not reacted. The base is preferably an alkali metal hydroxide and more preferably, sodium or potassium hydroxide. It is advantageous to use a basic solution having a concentration varying from 1 to 5 N. The amount of base used is at least equal to the stoichiometric amount expressed relative to the reduced product obtained and may be in excess of up to 100% of the stoichiometric quantity. After the basic treatment, the aqueous and organic phases are separated. The organic phase is recovered, which comprises the excess of compound (I) (which is then hydrolyzed) which has not reacted and the reduced product obtained. The organic solvent is evaporated. The reduced product is obtained, for example by distillation. In the case where the product is solid, a basic treatment is carried out as previously described. The aqueous and organic phases are separated. The organic phase is recovered and the organic solvent is evaporated. The solid is washed with an organic solvent in order to remove traces of solvent, for example, an aliphatic hydrocarbon, such as in particular pentane. The product is recovered and then dried. The drying temperature is a function of the melting point of the product obtained. The drying is generally carried out in air at a temperature varying between room temperature and

100 ° C. Thus, in accordance with the process of the invention, the reduction of the compounds I '):

(IV)

R— C - NH— R - CH ₂ - H ₂ 1 | ^ R _Γ NH ₂ R NH— R ₂ (V) ^R2 (VI ') (VU') (Vlll ') (IX) (X) R _c R _c

R - PR - P 7 I 7 RR ⁸ (XI ') ⁸ (XII')

An exemplary embodiment of the invention is given below by way of illustration and without limitation.

In the examples, the yield (RR) is defined as the ratio between the number of moles of product formed and the number of moles of substrate used.

Example 1: 1. Preparation of BINAPO: It is prepared by oxidation of BINAP. In a 250 ml flask, place the (S) - or (j-BINAP (2,2'- bis (diphenylphosphino) -1,1'-binaphthyle) (3 g, 4.81 mmol, 1 eq.) in 100 mL of CH ₂ CI _2. Cool to 0 ° C. and add 0 L of hydrogen peroxide at 35% by weight, stir while allowing to return to ambient temperature for 4 hours, then add 100 mL of The organic phase is separated and the aqueous phase is extracted with CH ₂ CI _2. The combined organic phases are washed with saturated sodium bisulfite, the absence of peroxide is checked and then dried over sodium sulfate. sodium and evaporated. A white solid is obtained (m = 3.14 g, 4.8 mmol, quantitative yield). The characterization of diphosphine in the form of dioxide (BINAPO) is as follows: - ¹ H NMR ( 300 MHz, CDCI3): 6.80 (d, 4H, J = 3.7), 7.2-7.3 (m, 8H), 7.3-7.5

(m, 12H), 7.6-7.7 (m, 4H), 7.8-7.9 (m, 4H). - ³¹ P NMR (81 MHz, CDCI ₃ ): 28.67 - Tf: 256-258 ° C. 2. Reduction of BINAPO: In a reaction tube fitted with a stirrer and under an inert atmosphere, BINAP oxide is placed (300 mg, 0.46 mmol, 1 eq). 2 ml of toluene and (0.5 ml, 2.8 mmol, 6 eq) of tetramethyldisiloxane and (0.065 ml, 0.23 mmol, 0.5 eq) of titanium isopropoxide are then added. The reaction mixture is then heated to 85 ° C and stirred for 20 hours. The mixture is cooled and 1 ml of sodium hydroxide (3N) is added. The mixture is left to stir for 15 minutes and then 5 ml of dichloromethane are added. We filter. The organic phase is recovered then dried and evaporated to obtain 280 mg of a white solid. The solid is taken up in 3 ml of pentane and filtered through a frit. A white solid from BINAP is obtained. 260 mg of product are recovered, which corresponds to a yield of 91%. The product obtained, BINAP has the following NMR characteristics: - m = 260 mg. - ¹ H NMR (300 MHz, CDCI3): 6.80 (d, 4H, J = 3.7), 7.2-7.3 (m, 8H), 7.3-7.5 (m, 12H ), 7.6-7.7 (m, 4H), 7.8-7.9 (m, 4H). - ³¹ P NMR (81 MHz, CDCI3): -14, 63. Example 2: 1. Preparation of 4.4'dicvanoBINAPO: It is prepared by bromination in position 4.4 'of BINAPO then nucleophilic substitution of the bromine atoms by cyano groups. Preparation of 4,4'-dibromoBINAPO: In a 250 ml dry flask, place BINAPO (5 g, 7.64 mmol, 1 eq.) Dissolved in 150 ml of dichloromethane. Pyridine (0.62 mL, 7.64 mmol, 1 eq.) Is then added, followed by the dibrome (1.2 mL, 22.92 mmol, 3 eq.). The mixture is stirred at room temperature for 20 hours. Transfer to a separatory funnel and then treat successively with saturated sodium bisulfite, brine, then saturated sodium bicarbonate. It is dried over sodium sulfate and evaporated. We repeat the procedure twice. The product is recrystallized from methanol to obtain a white solid (m = 4.74 g, 5.8 mmol, ie a yield of 76%). The characterization of diphosphine in dibrominated form is as follows: - ¹ H NMR (300 MHz, CDCI ₃ ): 6.80 (d, 2H, J = 8.3; 8.8'H), 6.85 (ddd , 2H,

J = 0.9; 6.7; 15.1; 7.7'H), 7.2-7.5 (m, 18H, phenyle + H6 and H6 '), 7.6-7.7 (m, 4H; phenyl), 7.75 (s, 2H; 3 , 3'H), 8.23 (d, 2H, J = 8.4; 5.5'H) - ³¹ P NMR (81 MHz, CDCI ₃ ): 27.60 - Tf:> 300 ° C Preparation of 4,4'-dicyanoBINAPO: In an inert atmosphere, in a 50 mL flask fitted with a condenser, place 4,4'-dibromoBINAPO (200 mg, 0.25 mmol, 1 eq.) And copper cyanide (63 mg, 0.7 mmol, 2.8 eq.). The mixture is dissolved in 3 mL DMF and heated to reflux overnight. The mixture is cooled and then treated with a solution of ethylenediamine (1mL) and water (1mL). The mixture is stirred for 2 minutes and then 5 ml of water and 10 ml of toluene are added. The mixture is stirred for 5 minutes and then the aqueous phase is extracted once with toluene. The combined organic phases are washed successively with 1 time of water, 4 times of HCl (0.1 M), 1 time of brine, then 1 time with saturated sodium bicarbonate. The product is then dried over sodium sulfate, then evaporated under reduced pressure (about 8 mm of mercury). The solid obtained is recrystallized from methanol. A white and pure solid is obtained (m = 0.100 g, 0.15 mmol, ie a yield of 60%). The characterization of diphosphine (PO) in dicyane form is as follows: - ¹ H NMR (200 MHz, CDCI ₃ ): 6.73 (d, 2H, J = 8.4), 6.90 (ddd, 2H, J = 1.0, 7.0, 14.3), 7.2-7.8 (m, 22H), 7.85 (d, 2H, J = 1.3), 8.28 (d, 2H , 8.3). - ³¹ P NMR (81 MHz, CDCI ₃ ): 27.77 - Mass (ESI ⁺ ): MH ⁺ = 813.35 - Tf:> 300 ° C 2. Reduction of 44'dicyanoBlNAPO: In a reaction tube fitted with a stirrer and under an inert atmosphere, 4,4'-dicyanoBINAPO (300 mg, 0.44 mmol, 1 eq) is placed. 2 ml of toluene and (0.5 ml, 2.8 mmol, 6 eq) of tetramethyldisiloxane and (0.13 ml, 0.46 mmol, 1 eq) of titanium isopropoxide are then added. The reaction mixture is then heated to 110 ° C and stirred for 20 hours. The mixture is cooled and 1 ml of sodium hydroxide (3N) is added. The mixture is left to stir for 2 hours and then 5 ml of dichloromethane are added. We filter. The organic phase is recovered then dried and evaporated to obtain 289 mg of a white solid. The solid is taken up in 3 ml of pentane and filtered through a frit. A white solid of 4,4'-diamBlNAP is obtained. 272 mg of product are recovered, which corresponds to a yield of 91%. The product obtained, 4,4'-diamBINAP has the following NMR characteristics: - H NMR (300 MHz, CDCI3) 6.64 (d, 2H, J = 9), 6.93- 6.97 (m, 2H), 7.1-7.3 ( m, 20H), 7.54 (t, 2H), 7.98 (s, 2H), 8.23 (d, 2H, J≈8.3). - ³¹ P NMR (81 MHz, CDCI3): -13.30.

EXAMPLE 3 Reduction of Benzonitrile: Benzonitrile (0.103 mL, 1 mmol, 1 eq) is placed in a reaction tube fitted with a stirrer and under an inert atmosphere. 2 ml of toluene and (1.8 ml, 10 mmol, 10 eq) of tetramethyldisiloxane and (0.30 ml, 1 mmol, 1 eq) of titanium isopropoxide are then added. The reaction mixture is then heated to 120 ° C and stirred for 30 hours. The mixture is cooled and 1 ml of sodium hydroxide (3N) is added. The mixture is left to stir for 5 hours and then 5 ml of dichloromethane are added. We filter. The organic phase is recovered then dried and evaporated. The residue obtained is distilled to obtain (64 mg, 60%) of a transparent liquid corresponding to the benzylamine. The product obtained, 4,4'-diamBINAP has the following NMR characteristics - 1 H NMR (300 MHz, CDCI3): 7.2-7.45 (m, 5H), 3.85 (s, 2H), 1 , 77 (s, 2H).

Claims

1 - Process for the reduction of an oxidized functional group present in a substrate, to a lower degree of oxidation, characterized in that it comprises placing the substrate in the presence of a siloxane type compound corresponding to the following formula ( I) associated with an effective amount of a catalyst of Lewis acid type.

in said formula: - Ri, R ₂ , identical or different, represent an alkyl, cycloalkyl, aryl group, - x is a number ranging from 0 to 50, said oxidized group being chosen from the following functional groups: carboxylic acid, ester, amide, nitrile, imine, nitro, nitrogen oxide, sulfoxide, sulfone, phosphine oxide or sulfide.

2 - Process according to claim 1 characterized in that the compound of siloxane type corresponds to formula (I) in which Ri and R ₂ are identical.

3 - Method according to one of claims 1 and 2 characterized in that the compound of siloxane type corresponds to formula (I) in which Ri and R represent an alkyl group having from 1 to 4 carbon atoms.

4 - Method according to one of claims 1 to 3 characterized in that the compound of siloxane type corresponds to formula (I) in which x is between 0 and 10 and preferably equal to 0 or 1.

5 - Method according to one of claims 1 to 4 characterized in that the compound of siloxane type is tetramethyldisiloxane.

6 - Method according to one of claims 1 to 5 characterized in that said groups can be carried by an aliphatic chain or a cycle but also included in a cycle. 7 - Method according to claim 6 characterized in that the substrate comprising the function to be reduced is represented by one of the formulas: in said formulas,

R, R.— C ≡N OR, OR— C = N - R _c 1 I 5 R— NO ₂ R,

R _* Rs O ^R - ^P R. R "- Ri to Rβ represent a hydrocarbon group having from 1 to 20 carbon atoms, - R ₃ , R and R ₅ also represent a hydrogen atom, - at most one groups R ₆ , R ₇ and R ₈ represent a hydrogen atom, - Ri and R ₂ , Ri and R, Rβ and R ₇ , R ₇ and R ₈ , Rβ and R ₈ , can be linked together to form a cycle.

8 - Process according to claim 7 characterized in that the substrate to be reduced is benzonitrile or a phosphine oxide or a diphosphine in the form of dioxide, preferably BINAPO or an oxide derived from BINAP substituted in position 6 and 6 ', 5 and 5 'or 4 and 4', preferably by nitrile groups.

9 - Method according to one of claims 1 to 8 characterized in that the ratio between the number of moles of the substrate to be reduced and the number of moles of the compound of formula (I) varies between 1 and 1000, preferably between 1 and 50.

10 - -Process according to one of claims 1 to 9 characterized in that the catalyst is a compound comprising a metal or metalloid cation metallic or metalloid elements of groups (IVa), (Vlla), (Ib), (llb), (lllb) and (Vlll) of the periodic table.

11 - Process according to claim 10 characterized in that the metallic or metalloid element is chosen from: titanium, zirconium, hafnium; manganese; the copper ; zinc; boron and aluminum; iron, cobalt, nickel.

12 - Method according to one of claims 10 and 11 characterized in that the anion is chosen from carboxylates, preferably acetate, propionate, benzoate: sulfonates preferably methanesulfonate, trifluoromethanesulfonate: alcoholates preferably methylate, ethylate, propylate, isopropylate; acetylacetonate.

13 - Method according to one of claims 10 and 11 characterized in that the anion is chosen from: chloride, bromide, iodide, carbonate.

14 - Method according to one of claims 10 to 13 characterized in that the catalyst is titanium isopropoxide or zinc trifluoroacetate.

15 - Method according to one of claims 10 to 14 characterized in that the amount of catalyst used expressed by the ratio between the number of moles of Lewis acid and the number of moles of substrate to be reduced varies between 0 , 1 and 1, and is preferably around 0.5.

16 - Method according to one of claims 1 to 15 characterized in that the reaction takes place in an organic solvent, preferably an aliphatic, cycloaliphatic or aromatic hydrocarbon halogenated or not; an ether or an alcohol.

17 - Process according to claim 16 characterized in that the solvent is toluene.

18 - Method according to one of claims 1 to 17 characterized in that the reduction reaction is carried out at a temperature varying between room temperature and 150 ° C, preferably between 80 and 120 ° C. 19 - Method according to one of claims 1 to 18 characterized in that the process of the invention is carried out under atmospheric pressure but preferably under a controlled atmosphere of inert gases preferably nitrogen.

20 - Method according to one of claims 1 to 19 characterized in that the substrate to be reduced is loaded, the organic solvent, the catalyst of Lewis acid type, then the reducing compound of formula (I) is introduced. ).

21 - Method according to one of claims 1 to 20 characterized in that one performs a basic hydrolysis at the end of the reaction and the reduced product is recovered.