FR2663321A1 - Process for the preparation of aldehydes from secondary alpha -trihalogenated alcohols - Google Patents

Abstract

The subject of the present invention is a process for the preparation of aldehydes from secondary alpha -trihalogenated alcohols. The distinguishing feature of the process of the invention consists in carrying out the cleavage reaction of the secondary alpha -trihalogenated alcohol to the corresponding aldehyde and trihalomethane in a solvent consisting, at least in part, of a polar aprotic solvent and in the presence of a tertiary amine.

Description

PROCESS FOR THE PREPARATION OF ALDEHYDES
FROM a-TRIHALOGEN SECONDARY ALCOHOLS
The subject of the present invention is a process for the preparation of aldehydes from a-trihalogenated secondary alcohols or trihalogenomethylcarbinols.

 A-trihalogenated secondary alcohols are known products and various processes for the transformation of these compounds, either into α-hydroxy acids or into aldehydes are described in the state of the art.

AKTIENGESELLSCHAFT FUR ANILIN patent FR-A 583856
FABRIKATION describes a process for preparing vanillin (3-methoxy-4-hydroxy-4-benzaldehyde) from 3-methoxy-4-hydroxy-phenyltrichloromethylcarbinol by reflux heating in aqueous solution in the presence of large amounts of copper acetate.

Such preparation is long (12 hours in general) and requires prohibitive amounts of copper acetate, which makes the process expensive and not transferable to industrial scale. In addition, we operate with significant dilutions.

 Patent FR-A 727165 to IG FARBENINDUSTRIE describes another method for splitting 3-methoxy-4-hydroxy-4-phenyltrichloromethylcarbinol and 3-hydroxy-4-phenyltrichloromethylcarbinol leading to the corresponding aldehydes. Said method consists in treating said phenyltrichloromethylcarbinols with an alkali metal alkoxide or an alcoholic hydrate of an alkali or alkaline earth metal, in methanol, under reflux.

Yields of about 50 to 75% of aldehydes are thus obtained, but the isolation of this product requires a long succession of operations: treatment with an acid to release the aldehyde obtained in the form of phenate, elimination of the solvent, extraction with chloroform, then rectification of the aldehyde.

It has also been proposed according to patent FR-A 791818 to
RHONE-POULENC and its addition certificates FR-A 46789 and FR-A 47291, a process for the preparation of aldehydes from aryltrichloromethylcarbinols which consists in carrying out the saponification and oxidation of aryltrichloromethylcarbinols with an alkaline aqueous solution to boiling (or at higher temperature) of alkali or alkaline earth metal chromate, manganese dioxide, lead dioxide, barium peroxide, hydrogen peroxide, alkali perborate or persulfate, possibly in the presence of copper metallic.

According to this process, it is necessary to operate in a very dilute medium and by-products of the reaction are formed, which must then be separated from the reaction medium.

Another process mentioned in GB-A 453 482 of
MONSANTO CHEMICALS LIMITED consists in carrying out the simultaneous or successive hydrolysis and oxidation of certain phenyltrichloromethylcarbinols by heating in an aqueous solution of alkali hydroxide with a nitrated aromatic compound such as nitrobenzene, m-dinitrobenzene or m-nitrotoluene.

More recently, SHELL INTERNATIONALE patent FR-A 2244743
RESEARCH MAATSCHAPPIJ BV describes the synthesis of hydroxybenzaldehydes, by cleavage of trichloromethylcarbinols, in polar aprotic solvents, in the presence of a base chosen from hydrides, alcoholates or carbonates of an alkali or alkaline-earth metal. The reaction time remains fairly high (4 to 24 hours). The recovery treatment of the aldehydes obtained is not easy, all the more since the acidification required in an aqueous medium generates the difficulties of subsequent separation of the polar aprotic solvent from the water, if it is desired not to lose large quantities of these expensive solvents.

 BAYER patent application EP-A 44009 describes, as new compounds, [3-hydroxy (2,2,2-trichloro-1 ethyl-hydroxy) -4] 1-phenyl-1,2,3-triazole and indicates that they can be transformed into corresponding aldehydes by the action of an alkali or alkaline earth metal hydroxide or alcoholate, in a polar aprotic medium.

The operation of isolating the aldehyde obtained from the reaction medium poses the same problems as for the previous process.

 A characteristic common to all these processes is that they are not suitable for compounds other than the hydroxyphenyltrichloromethylcarbinols derivatives. It seems that the presence of the phenol function is necessary. In addition, the operations for separating the aldehydes obtained from the reaction medium are relatively long and complex.

dans ladite formule, Q représente un radical hydrocarboné monovalent, éventuellement substitué ayant de 1 à 40 atomes de carbone et X symbolise un atome d'halogène, chlore, fluor, brome, iode et, de préférence, le chlore.An object of the invention is therefore to provide a very general process for obtaining aldehydes from a-trihalogenated secondary alcohols corresponding to the general formula (I)

in said formula, Q represents a monovalent hydrocarbon radical, optionally substituted having from 1 to 40 carbon atoms and X symbolizes a halogen, chlorine, fluorine, bromine, iodine and, preferably, chlorine atom.

sera appelé "trihalogénométhylcarbinol".In formula (I), the group

will be called "trihalomethylethylcarbinol".

 The characteristic of the process of the invention consists in effecting the splitting of the a-trihalogenated secondary alcohols into corresponding aldehydes and trihalogenethane in a solvent constituted at least in part, by a polar aprotic solvent and in the presence of a tertiary amine.

In accordance with the process of the invention, the cleavage reaction of the a-trihalogenated secondary alcohol corresponding to formula (I) takes place according to the general equation
adequate solvent

amine

amine

More specifically, the a-trihalogenated secondary alcohols or trihalomethylethylcarbinols serving as starting materials for the preparation of aldehydes correspond to the general formula (I) in which
Q represents a monovalent hydrocarbon radical, substituted or unsubstituted which can be an acyclic saturated or unsaturated, linear or branched aliphatic radical; a saturated, unsaturated or aromatic, monocyclic or polycyclic carboxyclic or heterocyclic radical.

 Particularly suitable for carrying out the process of the invention, the trihalomethylethylcarbinols of general formula (I) in which Q represents a monocyclic or polycyclic aromatic hydrocarbon radical; the radicals being able to form between them orthocondensed (for example the naphthyl) or ortho and pericondensed systems.

dans ladite formule (II) - n est un nombre entier de 0 à 5, de préférence de 0 à 3, - R représente R1, l'un des groupes ou fonctions suivantes
un radical alkyle, linéaire ou ramifié, ayant de 1 à 6 atomes
de carbone, de préférence de 1 à 4 atomes de carbone, tel que
méthyle, éthyle, propyle, isopropyle, butyle, isobutyle, sec
butyle, tert-butyle,
un radical alcényle linéaire ou ramifié ayant de 2 à 6 atomes
de carbone, de préférence, de 2 à 4 atomes de carbone, tel que
vinyle, allyle,
un radical alkoxy linéaire ou ramifié ayant de 1 à 6 atomes de
carbone, de préférence de 1 à 4 atomes de carbone tel que les
radicaux méthoxy, éthoxy, propoxy, isopropoxy, butoxy,
un radical de formule -R2-OH
-R2-COOH
-R2-CHO -R2-NO2
-R2-CN -R2 -NH2
-R2-SH
-R2-X
-R2-CF3
dans lesdites formules R2 représente un lien valentiel ou un
radical hydrocarboné divalent, linéaire ou ramifié, saturé ou
insaturé, ayant de 1 à 4 atomes de carbone tel que par exemple,
méthylène éthylène, propylène, isopropylène, isopropylidène et X
symbolise un atome d'halogène, notamment un atome de chlore ou
de brome.Q preferably represents an aryl radical corresponding to the general formula (II)

in said formula (II) - n is an integer from 0 to 5, preferably from 0 to 3, - R represents R1, one of the following groups or functions
an alkyl radical, linear or branched, having from 1 to 6 atoms
carbon, preferably from 1 to 4 carbon atoms, such as
methyl, ethyl, propyl, isopropyl, butyl, isobutyl, dry
butyl, tert-butyl,
a linear or branched alkenyl radical having from 2 to 6 atoms
carbon, preferably from 2 to 4 carbon atoms, such as
vinyl, allyle,
a linear or branched alkoxy radical having from 1 to 6 atoms of
carbon, preferably from 1 to 4 carbon atoms such as
methoxy, ethoxy, propoxy, isopropoxy, butoxy radicals,
a radical of formula -R2-OH
-R2-COOH
-R2-CHO -R2-NO2
-R2-CN -R2 -NH2
-R2-SH
-R2-X
-R2-CF3
in said formulas R2 represents a valential link or a
divalent, linear or branched, saturated or
unsaturated, having from 1 to 4 carbon atoms such as for example,
methylene ethylene, propylene, isopropylene, isopropylidene and X
symbolizes a halogen atom, in particular a chlorine atom or
bromine.

ians lequel R1 et R2 ont la signification donnée précédemment et m est un nombre entier de 0 à 3, un radical R2-A-R4 dans lequel R2 a la signification donnée précédemment, R4 représente un radical alkyle linéaire ou ramifiée ayant de 1 à 6 atomes de carbone, de préférence, de 1 à 4 atomes de carbone ou un radical

et A symbolise l'un des groupes suivants -O-, -COF,

- R represents R3 one of the more complex radicals following a radical

i in which R1 and R2 have the meaning given above and m is an integer from 0 to 3, a radical R2-A-R4 in which R2 has the meaning given above, R4 represents a linear or branched alkyl radical having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms or a radical

and A symbolizes one of the following groups -O-, -COF,

-S-, -SO2-,
in these formulas R5 represents a hydrogen atom or a
linear or branched alkyl radical having from 1 to 4 atoms of
carbon, preferably a methyl or ethyl radical.

 When n is greater than 1, the radicals R can be identical or different and 2 successive carbon atoms of the benzene ring can be linked together by a ketal bridge such as the extranuclear methylene dioxy or ethylene dioxy radicals.

 Preferably, n is equal to (0) -1-2 or 3.

Among all the abovementioned radicals Q, very preferably in the process of the invention, the trihalomethylethylcarbinols corresponding to the general formula (I) in which Q represents an aryl radical corresponding to the general formula (II) in which
- n is equal to 0, 1, 2 or 3,
- R represents one of the following function groups
. a linear or branched alkyl radical having from 1 to 4
carbon atoms,
a linear or branched alkoxy radical having from 1 to 4 atoms
of carbon,
a methylene or ethylene dioxy radical,
. a group H,
a -CHO group,
a phenyl or benzyl radical,
. a halogen atom.

 As examples of trihalomethylethylcarbinols corresponding to the general formula (I) in which Q represents an aryl radical of general formula (II), there may be mentioned: 2-hydroxy-1-phenyl trichloromethylcarbinol, 1-hydroxy-3-phenyl- 1 trichloromethylcarbinol, 4-hydroxyphenyl-1 trichloromethylcarbinol, 2-hydroxy-3-methylphenyl-1 trichloromethylcarbinol, 2-hydroxy-4-methylphenyl-1 trichloromethylcarbinol, 1 '2-hydroxy-5-methylphenyl-1 trichloromethylcarbinol, 3-hydroxy-4-methyl-1-phenyl trichloromethylcarbinol, 2-methoxy-phenyl-1 trichloromethylcarbinol, 3-methoxy-phenyl-1 trichloromethylcarbinol, 4-methoxy-phenyl-1 trichloromethylcarbinol, 5-methoxy-phenylcarbinol , 1 '3-hydroxy-4-methoxy-phenyl-1 trichloromethylcarbinol, 4-hydroxy-3-methoxy-phenyl-1 trichloromethylcarbinol, 1' 3-hydroxy-dimethoxy-4,5 phenyl-1 trichloromethylcarbinol, 1 '4-hydroxy-dimethoxy-3 , 5-phenyl-1 trichloromethylc arbinol, 1-hydroxy-phenyl-1,3 bis (trichloromethylcarbinol), hydroxy-2 amino-3 phenyl-1 trichloromethylcarbinol, hydroxy-2 amino-4 phenyl-1 trichloromethylcarbinol, 2-hydroxy-5 amino phenyl -1 trichloromethylcarbinol, 3-hydroxy-2-amino-phenyl-1 trichloromethylcarbinol, 1-hydroxy-3-nitro-3-phenyl-1 trichloromethylcarbinol, 3-hydroxy-4-nitro-phenyl-1 trichloromethylcarbinol, 4-hydroxy-nitro- 3 phenyl-1 trichloromethylcarbinol, hydroxy-3 methyl-4 nitro-2 phenyl-1 trichloromethylcarbinol, hydroxy-2 diiodo-3,5 phenyl-1 trichloromethylcarbinol, 2,3-dihydroxy phenyl-1 trichloromethylcarbinol, dihydroxy -2, 4 phenyl-1 trichloromethylcarbinol, dihydroxy-2,5 phenyl-1 trichloromethylcarbinol, dihydroxy-2,6 phenyl-1 trichloromethylcarbinol, dihydroxy-3,4 phenyl-1 trichloromethylcarbinol, dihydroxy-3,5 phenyl- 1 trichloro methylcarbinol, 3,5-dihydroxy-4-methyl-1-phenyl trichloromethylcarbinol, 2,3,4-trihydroxy-1-phenyl tri chloromethylcarbinol, 2,4,6-trihydroxy phenyl-1 trichloromethylcarbinol, 3,4,5-trihydroxy phenyl-1 trichloromethylcarbinol.

 In the general formula (I) of trihalomethylethylcarbinols, Q may represent a carbocyclic radical saturated or comprising 1 or 2 unsaturations in the ring, generally having 3 to 7 carbon atoms, preferably 6 carbon atoms in the ring; said ring possibly being substituted by 1 to 5 radicals R1, preferably 1 to 3, R1 having the meanings stated above for the substituents of the aryl radical of general formula (II).

 As preferred examples of radicals Q, mention may be made of cyclohexyl or cyclohexene-yl radicals, optionally substituted by linear or branched alkyl radicals, having from 1 to 4 carbon atoms.

 As examples of trihalomethylcarbinols of formula (I) in which Q is a cycloaliphatic radical, there may be mentioned in particular (trichloromethylcarbinol) -1 cyclohexene-1, (trichloromethylcarbinol) -1 cyclohexane, methyl-1 (trichloromethylcarbinol) - 2 cyclohexene-1, methyl-1 (trichloromethylcarbinol) -2 cyclohexane, methyl-1 isopropyl-4 (trichloromethylcarbinol) -2 cyclohexene-1, methyl-1 isopropyl-4 (trichloromethylcarbinol) -2 cyclohexane.

 As mentioned previously, Q can represent an acyclic aliphatic radical, saturated or unsaturated, linear or branched.

 More precisely, Q represents an alkyl, alkenyl, alkadienyl, alkynyl, linear or branched radical preferably having from 1 to 12 carbon atoms.

The hydrocarbon chain can optionally be interrupted by one of the following groups
+, -CO-, -COO-,

-S-, -S02-, in these formulas R6 represents hydrogen or a linear or branched alkyl radical having from 1 to 4 carbon atoms, preferably a methyl or ethyl radical, - and / or carrying one of the following substituents
-OH, OOH, -CHO, NO2, -CN, -NH2, -5H, -X, -CF3
The acyclic, saturated or unsaturated, linear or branched aliphatic radical may optionally carry a cyclic substituent.

By cycle is meant a carbocyclic or heterocyclic, saturated, unsaturated or aromatic cycle.

The acyclic aliphatic radical can be linked to the ring by a valential bond or by one of the following groups
-O-, -CO-, -COO-,

 -S-, -S02-, in these formulas, R6 having the meaning given above.

 As examples of cyclic substituents, it is possible to envisage cycloaliphatic, aromatic or heterocyclic, in particular cycloaliphatic substituents comprising 6 carbon atoms in the ring or benzenic, these cyclic substituents themselves being optionally carriers of 1, 2, 3, 4 or 5 radicals R1, identical or different, R1 having the meaning given above.

 As examples of trihalomethylcarbinols of formula (I) in which Q represents an aliphatic radical, there may be mentioned in particular: nitro-3, 1,1,1-trichloro-2-butanol, trifluoro-1,1,1 pentanol -2, nitro-3, 1,1,1-trichloro-pentanol-2, methyl-4-trichloro-1,1,1 pentanol-2, trifluoro-1,1,1 hexanol-2, dimethyl-3 , 3 trifluoro-1,1,1 butanol-2, 1 'hydroxy-2, methoxy-4-trichloro-1,1,1 pentanol-5, trichloro-1,1,1 heptanol-2, 1' hydroxy-5 4-methyl-6,6,6-trichloro-hexanone-3, 1 '2-hydroxy-1,1,1-trichloro-octanone-4, 1' 2-hydroxy-6-methyl-1,1-trichloro-4,1-heptanone '4-ethyl-1,1,1-trichloro-hexanol-2, 1' 3-ethyl-trichloro-1,1,1 heptanol-2, hydroxy-2, 1,1-trichloro nonanone-4, 1 ' hydroxy-2 methyl-7,1-trichloro-1,1,1 octanone-4, trichloro-1,1,1 trimethyl-4,6,6 heptanol-2 trichloro-1,1,1 nonanol-2, hydroxy -2 trichloro-1,1,1 decanone-4, hydroxy-2 trichloro-1,1,1 undecanone-4, trichloro-1,1,1 dodecanol-2; 1,1,1-trichloro-butene-3 ol-2, 1,1,1-trichloro-pentene-3 ol-2, 3-methyl-trichloro-1,1,1 butene-3 ol-2, trichloro -5.5.5 pentene-1 ol-4, methyl-4 trichloro-1,1,1 pentene-3 ol-2, methyl-3 trichloro-1,1,1 pentene-3 ol-2, 4-methyl-1,1,1-3,1-pentene-ol-2, 3,4-dimethyl-1,1,1-3-pentene-ol-2, 4-ethyl-1,1,1-trichlorohexene -3 ol-2, trichloro-1,1,1 nonene-3 ol-2, tetrachloro-1,1,1,4 nonene-3 ol-2, trichloro-1,1,1 dodecene-3 ol -2; 7-bromo-1,1,1-trichloro-octene-7 yne-3 ol-2, 8-trichloro-1,1,1-octene-7 yne-3 ol-2, trichloro-1,1,1 nonyne-3 ol-2, trichloro-1,1,1 decyne-3 ol-2; 1,1,1 trichloro (4-methylcyclohexene-3 yl-1) -4 pentene -3 o1-2; trichloroethylol-9 limonene, (tetrahydro-3,4,5,6) nonatolyl-4 trichloro-1,1,1 pentanol-2, trichloroéthylol-9 paramenthane, phenyl-4 trichloro-1,1,1 pentene -3 ol-2, 4-phenyl-1,1,1-trichloro-2, pentanol-2, 4,6,6-trimethyltrichloro-1,1,1, heptene-3 ol-2, trimethyl-4,6 , 6, 1,1,1-trichloro-heptanol-2, 5-methyl-1,1,1-trichlorohexene-5 ol-2, 5-methyl-1,1,1-trichloro-2-hexanol, dimethyl-3 , 4, 1,1,1 trichloro, 2-pentanol, 4,6-dihydroxy, 5-nitro (3,3,3-2-hydroxy-propyl trichloro) -2 pyrimidine.

 Q can also represent a monovalent heterocyclic radical, saturated or not, comprising in particular 5 or 6 atoms in the ring including 1 or 2 heteroatoms such as nitrogen, sulfur and oxygen atoms, carbon atoms of the heterocycle may optionally be substituted, in their entirety or for a part of them only by radicals R1, R1 having the meaning given above for the substituents of the aryl radical of formula (II).

 Q can also represent a polycyclic heterocyclic radical defined as being either a radical constituted by 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 is a radical constituted by at least an 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 trihalomethylcarbinols of formula (I) in which Q represents a heterocyclic radical, mention may be made of 2-furyl trichloromethylcarbinol, 2-nitrofuryl trichloromethylcarbinol, (methylfuryl-5) -1 trichloromethylcarbinol, (N, N -diethylfuramide-5) -1 trichloromethylcarbinol, 1-amino-4-hydroxy-4-methyl-6 (trichloromethylcarbinol) -5 pyrimidine, 1 'hydroxy-4-methyl-6 methylamino-2 (2,2,2-hydroxy-1-trichloro ) -5 pyrimidine, 2-dimethylamino-4-hydroxy-methyl-6 (2,2,2-trichloro-1-hydroxy-ethyl) -5 pyrimidine.

The trihalomethylethylcarbinol compounds which can be subjected to cleavage into aldehydes according to the process of the invention are obtained by processes described in the literature. In particular, they can be prepared by any of the methods of preparation mentioned by
JHT LEDRUT and G. COMBES in "Belgian chemical industry" nO 6 (1962) p. 635 to 652.

 Among these various processes for obtaining trihalomethylethylcarbinols, some are more suitable than others for the preparation of certain families of this type of compound.

 Thus, for example, compounds having mobile hydrogen can react with chloral (or bromal) to give the corresponding trihalomethylethylcarbinol.

An acid catalyst such as aluminum chloride can be used to react aromatic hydrocarbons such as veratrole (or 1,2-dimethoxy benzene) with chloral. For this type of preparation, we can refer, in addition to the previously cited article, to the article by R. QUELET in the Bulletin de la Société Chimique de
France (1954), p. 932.

Starting from phenols, the chloral can be reacted in the presence of anhydrous potassium carbonate [see M. PAULY Berichte der
Deutschen Gesellschaft 56, 979 (1923)].

 The amine of which the pka measured at 250 ° C. is preferably greater than or equal to 6.0 is also involved in the process of the invention.

dans ladite formule Rg, Rg, R10 identiques ou différents représentent - un radical aliphatique linéaire ou ramifié, saturé ou insaturé ayant de 1 à 12 atomes de carbone et/ou un radical cycloaliphatique saturé ou insaturé ayant de 3 à 7 atomes de carbone dans le cycle, - les radicaux Rg, Rg, R10 peuvent former ensemble un radical alkylène, alcénylène ou alcadiénylène comportant de 4 à 6 atomes dont, éventuel lement un à trois atomes d'azote et constituant ainsi un hétérocycle azoté, monocyclique ou polycyclique, saturé ou insaturé.According to the invention, use is preferably made of a tertiary amine corresponding to the general formula (III)

in said formula Rg, Rg, R10, identical or different, represent - a linear or branched, saturated or unsaturated aliphatic radical having from 1 to 12 carbon atoms and / or a saturated or unsaturated cycloaliphatic radical having from 3 to 7 carbon atoms in the ring, - the radicals Rg, Rg, R10 may together form an alkylene, alkenylene or alkadienylene radical comprising from 4 to 6 atoms of which, optionally one to three nitrogen atoms and thus constituting a nitrogen heterocycle, monocyclic or polycyclic, saturated or unsaturated.

 When Rg, Rg, R10 are aliphatic radicals, the hydrocarbon chain can be interrupted by an oxygen or nitrogen atom or be carrying a halogen atom and / or a substituent such as an organic function especially -OH or -NH2.

 Among the amines corresponding to formula (III), those which are perfectly suitable for the invention are those in which the radicals Rg, Rg and R10 which are identical or different are linear or branched alkyl radicals having from 1 to 6 carbon atoms, preferably , from 1 to 4 carbon atoms.

 As examples of radicals Rg, Rg and R10, mention may be made of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl radicals. isohexyl, octyl, isooctyl, decyl, dodecyl, cyclohexyl.

As examples of amine of formula (III) which are particularly suitable for the invention, there may be mentioned, in particular: trimethylamine,
N, N-dimethylethylamine, amino-1 N, N-dimethylamino-2 ethane,
N, N-diethylmethylamine, N, N, N-dimethylisopropylamine, N, N, N -dimethylpropylamine, 1,1,3,3 tetramethyl guanidine, 1-amino
N, N-dimethylamino-2 propane, 2-amino N, N-dimethylamino-1 propane, triethylamine, N, N-dimethylisobutylamine, N, N-dimethyl amino-1 butane, N, N-dimethyl amino-2 butane, N, N-dimethyl tert-butylamine, amino-2 N, N-dimethyl amino-3 butane, amino-1
N, N-dimethylamino-2-methyl-2-propane, 1-amino-2 N, N-dimethylamino-1-methyl-2-propane, N, N-diallylmethylamine, N, N-diethylamino-3-trifluoro-1, 1, 1-propanol-2, N, N-dimethyl tertiopentylamine, 3-amino, 2-N-dimethylamino-2-methyl-butane, N, N-dimethyl-amino-1 cyclohexane, tripropylamine, tri-isobutylamine, tributylamine, tetramethylethylenediamine, ethyldipropylamine, (diisopropylamino) -2 ethanol, triethylene diamine.

 Triethylamine and tributylamine are used in a completely preferential manner.

 According to the method of the invention, the cleavage of the trihalomethylethylcarbinol into the corresponding aldehyde is carried out in an organic solvent consisting in part of a polar aprotic solvent.

 Examples of polar aprotic solvents which can be used in the process of the invention include, in particular, N-methylpyrrolidone (NMP), diethylformamide (DMF), dimethylsulfoxide (DMSO), hexamethylphosphotriamide (HMPT), dimethylacetamide (DMAC), tetramethylurea, sulfolane, nitromethane.

 In a practical manner, the polar aprotic solvent can constitute the entire solvent medium. It can also be mixed with one or more third-party solvents. This third solvent must be miscible with the polar aprotic solvent and allow at least partial dissolution of the a-trihalogenated secondary alcohol and the amine.

 By way of example of third solvents which can be used, mention may be made of aliphatic or aromatic hydrocarbons, halogenated or not.

 As aliphatic or aromatic hydrocarbons, there may be mentioned hexane, heptane, octane, nonane, decane or cyclohexane, toluene, xylene.

 As aliphatic or aromatic halogenated hydrocarbons, one can mention: perchlorinated hydrocarbons such as in particular carbon tetrachloride, tetrachlorethylene, hexachloroethane, hexachloropropene and hexachlorobutadiene, partially chlorinated hydrocarbons such as methylene chloride , dichloroethane, tetrachloroethane, trichloroethylene, 1-chloro butane, 1,2-dichloro butane; monochlorobenzene, 1,2-dichloro-benzene, 1,3-dichloro-benzene, 1,4-dichloro-benzene or mixtures of different chlorobenzenes; monobromobenzene or mixtures of monobromobenzene with one or more dibromobenzenes.

 Generally, the third solvent represents from 0 to 100% by weight of the polar aprotic solvent and, preferably, from 0 to 50% by weight.

 In accordance with the process of the invention, the reaction for splitting trihalomethylethylcarbinols into corresponding aldehydes is carried out in the presence of an amine, in an organic solvent constituted at least in part by a polar aprotic solvent, the various compounds being used in the proportions defined below.

 The concentration of trihalomethylethylbinol in the organic solvent can vary within wide limits, for example from 0.1 to 10 mol / liter. However, a concentration chosen between 1 and 2 mol / liter is preferred.

 As regards the quantity of amine involved, expressed relative to the trihalomethylethylcarbinol, it is such that the molar ratio of tertiary amine / trihalogenethylcarbinol varies from 0.1 to 10, preferably from 0.5 to 2.0. To have a total and rapid conversion rate, it is desirable that said ratio be greater than 0.5.

 The reaction temperature can be between 1000C and 2000C and preferably between 1400C and 1700C.

 The reaction can be carried out under atmospheric pressure or alternatively under reduced pressure, preferably between 10 and 500 millibars.

 The duration of the reaction can be very variable. Among other things, it depends on the nature of the trihalomethylethylcarbinol, its conversion rate and the reaction temperature. It is most often between 1 hour and 50 hours, preferably between 2 hours and 5 hours.

 From a practical point of view, the reaction is easily carried out by loading the organic solvent, the trihalomethylcarbinol and the amine into the apparatus, then bringing the reaction mixture with stirring to the desired temperature, optionally under reduced pressure, for the duration necessary for the completion of the reaction.

 Another practical embodiment of the invention consists in first charging the amine and part of the reaction solvent, for example, half, then in gradually introducing, by casting, the trihalomethylethylcarbinol in solution into the other part of the reaction solvent. .

At the end of the reaction, the reaction mixture comprises the aldehyde formed, the unreacted trihalomethylethylcarbinol, the amine and the reaction solvent
The aldehyde formed is recovered, most often by distillation under atmospheric pressure or under reduced pressure (10 to 500 millibars) if the aldehyde is a heavy aldehyde with a high boiling point (for example greater than or equal to 1500C).

 The amine can also be separated from the mixture by distillation and it will be chosen so that its boiling point is higher or lower than that of the aldehyde formed.

 If the aldehyde formed is light and is the first to distill, it is possible to recycle the distillation pellet which contains the amine, the unreacted trihalomethylethylcarbinol and the reaction solvent.

 An advantage of the process of the invention is that it makes it possible to prepare an aldehyde, without polluting effluent because the trihalogenomethane formed can be recovered.

 Examples of the invention are given below.

 The following examples are given, by way of illustration, without limitation.

EXAMPLE 1
In a 100 ml three-necked glass flask equipped with a half-moon type glass stirrer, a right cooler, a nitrogen circulation, a thermometer and a heating bath, the charge is made.
- 50 g of N-methylpyrrolidone
- 11.42 g of veratrole trichloromethylcarbinol (0.04 mol) of
formula

-14.8 g of tributylamine
The reaction medium is stirred, a stream of nitrogen is passed through and the mixture is heated to 1500C in the mass.

 The chloroform is distilled off as the reaction progresses.

 After 1 hour of heating at 1500C, it is cooled to 250C.

 The reaction mixture is determined by gas chromatography (C.P.G.).

 6.75 g (0.04 mol) of veratric aldehyde (dimethoxy3,4 benzaldehyde) are obtained, ie a yield of 100%.

EXAMPLE 2
Example 1 is reproduced with the only difference that 2 g of tributylamine are loaded.

 The reaction medium is stirred and heated for 3 hours at 1500C.

 5.25 g of veratric aldehyde dosed by C.P.G are obtained, ie a yield of 79%.

COMPARATIVE EXAMPLE 3
Example 1 is reproduced but the tributylamine is not loaded.

 The reaction medium is stirred and heated for 4 hours at 1500C.

 In the absence of amine, there is no reaction.

EXAMPLE 4
Example 1 is repeated but the N-methylpyrrolidone is replaced by 50 g of dimethylformamide.

 The reaction medium is stirred and heated for 4 hours at 1500C.

 We measure the veratric aldehyde by C.P.G.

 A 91% yield of veratric aldehyde is obtained.

EXAMPLE 5
Example 1 is repeated but the N-methylpyrrolidone is replaced by 50 g of sulfolane.

 The reaction medium is stirred and heated for 1 hour 30 minutes at 1500C.

 We measure the veratric aldehyde by C.P.G.

 A yield of 82% in veratric aldehyde is obtained.

EXAMPLE 6
In a reactor as described in Example 1, the charge is
- 50 g of N-methylpyrrolidone
- 13.62 g of guaiacol trichloromethylcarbinol (0.05 mol)
from the addition of chloral to the guaiacol and having the
formula

- 18.54 g of tributylamine
It is heated to 1700C for 1 hour, while distilling the chloroform.

 The vanillin is measured by high pressure liquid chromatography (C.L.H.P.).

 We obtain a yield of 57% in vanillin.

EXAMPLE 7
Example 6 is repeated, but heating at 1500C for 6 hours 30 minutes.

 Vanillin is measured by C.L.H.P.

 We obtain a vanillin yield of 59%.

EXAMPLE 8
A 250 ml glass reactor equipped as in Example 1 is charged
- 50 g of N-methylpyrrolidone,
- 13.62 g of guaiacol trichloromethylcarbinol (0.05 mol)
Heated to 1600C and poured in 45 minutes7 27.8 g of tributylamine.

The temperature is maintained at 1600C for another 1 hour then cooled to 250C
We dose the vanillin by CPG

 A transformation rate of the guaiacol trichloromethylcarbinol is obtained of 85% and a vanillin yield of 71% expressed relative to the trichloromethylcarbinol of transformed guaiacol.

EXAMPLE 9
Example 8 is reproduced with the only difference that the temperature of 1600C is maintained for 6.45 hours (instead of 1 hour).

 Vanillin is measured by C.L.H.P.

 A transformation rate of guaiacol trichloromethylcarbinol of 100% is obtained and a vanillin yield of 54%.

EXAMPLE 10
In a reactor as described in Example 8, the charge is
- 50 g of N-methylpyrrolidone
- 20 g of chlorobenzene
- 10.9 g of guaiacol trichloromethylcarbinol (0.04 mol)
- 14.8 g of tributylamine
The reaction medium is stirred and heated for 6 hours at 1600C.

 Vanillin is measured by C.P.G.

 A yield of vanillin of 49% is obtained.

EXAMPLE 11
Example 10 is repeated but the chlorobenzene is not charged.

 The same results are obtained.

EXAMPLE 12
In a reactor as described in Example 8, the charge is
- 25 g of N-methylpyrrolidone
- 20 g of chlorobenzene
- 14.8 g of tributylamine
Heated to 1700C and poured in 1 hour, a solution of 10.9 g of guaiacol trichloromethylcarbinol (0.04 mol) in 25 g of N-methylpyrrol idone
The temperature of 1700C is maintained for another 30 minutes and then cooled to 250C.

 Vanillin is measured by C.P.G.

 A conversion rate of the guaiacol trichloromethylcarbinol is obtained of 87% and a vanillin yield of 53% expressed relative to the trichloromethylcarbinol of transformed guaiacol.

EXAMPLE 13
In a reactor as described in Example 8, the charge is
- 50 g of N-methylpyrrolidone
- 10 g of chlorobenzene,
- 10.9 g of guaiacol trichloromethylcarbinol (0.04 mol)
Heated to 1800C and poured in 40 minutes 14.8 g of tributylamine.

 The temperature is maintained at 1800C for another 30 minutes and then cooled to 250C.

 Vanillin is measured by C.P.G.

 A transformation rate of the guaiacol trichloromethylcarbinol is obtained of 88% and a vanillin yield of 55% expressed relative to the trichloromethylcarbinol of transformed guaiacol.

EXAMPLE 14
Example 13 is reproduced with the difference that the chlorobenzene is removed and a reaction temperature of 1600C is chosen.

 A conversion rate of the guaiacol trichloromethylcarbinol is obtained of 88% and a vanillin yield of 63% expressed relative to the trichloromethylcarbinol of transformed guaiacol.

COMPARATIVE EXAMPLE 15
Example 11 is repeated, replacing the N-methylpyrrolidone with 50 g of chlorobenzene.

 The temperature is limited by the reflux temperature of chlorobenzene.

 We therefore maintain a temperature of 1300C for 5 hours.

 A transformation rate of guaiacol trichloromethylcarbinol of 90% is obtained, but only traces of vanillin are formed (yield ~ 3%).

COMPARATIVE EXAMPLE 16
Example 15 is repeated, replacing the chlorobenzene with 50 g of butoxyethanol.

 After 14 hours of heating at 1400C, a yield of vanillin is obtained of only 5%.

COMPARATIVE EXAMPLE 17
In this example, tertiary amine is used as the reaction solvent in place of the polar aprotic solvent.

In a reactor as described in Example 8, the charge is
- 50 g of tributylamine
- 10.9 g of guaiacol trichloromethylcarbinol (0.04 mol)
Maintaining a temperature of 1600C for 5 hours.

 Vanillin is measured by C.P.G.

 A degree of transformation of the guaiacol trichloromethylcarbinol is obtained of 90% and a vanillin yield of 14%.

EXAMPLE 18
In a reactor as described in Example 8, the charge is
- 50 g of N-methylpyrrolidone
- 12.08 g of phenol trichloromethylcarbinol (0.06 mol) of formula

- 18.54 g of tributylamine
The mixture is heated to 1600C for 5 hours 30 minutes then cooled to 250C.

 The aldehyde formed by C.P.G.

 A yield of p-hydroxybenzaldehyde of 69% is obtained.

EXAMPLE 19
In a reactor as described in Example 8, the charge is
- 50 g of N-methylpyrrolidone
- 10.3 g of pyrocatechol trichloromethylcarbinol (0.04 mol) of formula

 It is heated to 1500C for 2 hours and then cooled to 250C.

 The aldehyde formed by C.P.G.

 A conversion rate of pyrocatechol trichloromethylcarbinol is obtained of 90% and a yield of Protocatechic aldehyde of 20%.

EXAMPLE 20
In this example, the preparation of heliotropin is carried out.

en faisant réagir 0,2 mol de méthylènedioxy-1,2 benzène et 0,2 mol de chloral.In a first step, the 1,2-methylenedioxy benzene trichloromethylcarbinol of formula is prepared

by reacting 0.2 mol of 1,2-methylenedioxy-benzene and 0.2 mol of chloral.

 After usual treatment, a crude product is obtained, the dosage of which by C.P.G. shows that only 50% of the 1,2-methylenedioxy-benzene is transformed, ie 0.1 mole.

 To this crude product, 60 g of N-methylpyrrolidone and 37 g of tributylamine are added.

 The reaction medium is heated to 1600C for 6 hours and then cooled to 250C.

 The aldehyde formed by C.P.G.

 0.07 mol of heliotropin is obtained, an overall yield over the two stages of 70% in aldehyde relative to the transformed 1,2-methylenedioxy benzene.

EXAMPLE 21
In a reactor as described in Example 8, the charge is
- 50 ml of N-methylpyrrolidone
- 8.12 g of 4-methyl-1,1,1-trichloro-3-pentene-ol-2
- 14.8 g of tributylamine
The reaction medium is heated to 1600C for 5 hours.

 We highlight by C.P.G. the presence of 3-methyl-2-butene al.

EXAMPLE 22
In a reactor as described in Example 8, the charge is
- 80 ml of N-methylpyrrolidone
- 5.65 g of p-tertiobutylbenzene trichloromethylcarbinol
(0.02 mol)
- 7.8 g of tributylamine
The reaction medium is heated to 1500C for 5 hours then cooled to 250C.

 The aldehyde formed by C.P.G.

 A yield of p-tert-butylbenzaldehyde of 87% is obtained.

EXAMPLE 23
Example 22 is repeated, but 1.85 g are loaded instead of 7.8 g of tributylamine.

 The aldehyde formed by C.P.G.

 A yield of p-tert-butylbenzaldehyde of 58% is obtained.

EXAMPLE 24
Example 22 is repeated, but 3.7 g of tributylamine and 80 ml of hexamethylphosphotriamide are loaded.

 The aldehyde formed by C.P.G.

 A yield of p-tert-butylbenzaldehyde of 47% is obtained.

EXAMPLE 25
Example 22 is repeated, but 8.52 g of dihexylethylamine are loaded in place of tributylamine.

 The aldehyde formed by C.P.G.

 A yield of p-tert-butylbenzaldehyde of 73% is obtained.

EXAMPLE 26
Example 22 is repeated but 4.5 g of triethylenediamine are loaded in place of the tributylamine.

 The aldehyde formed by C.P.G.

 A yield of p-tert-butylbenzaldehyde of 81% is obtained.

EXAMPLE 27
Example 22 is reproduced with the only difference that the trimethylcarbinol of p-disopropylbenzene is used in place of the trimethylcarbinol of p-tertiobutylbenzene.

 A yield of p-isopropylbenzaldehyde of 71% is obtained.

Claims (23)

1 - Process for the preparation of an aldehyde by cleavage of the corresponding a-trihalogenated secondary alcohol characterized in that the reaction is carried out in a solvent constituted at least in part by a polar aprotic solvent and in the presence of a tertiary amine . 2 - Process according to claim 1 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I)

 in said formula, Q represents a monovalent hydrocarbon radical, optionally substituted having from 1 to 40 carbon atoms and X symbolizes a halogen, chlorine, fluorine, bromine, iodine and, preferably, chlorine atom. 3 - Method according to one of claims 1 and 2 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents a monovalent hydrocarbon radical, substituted or not which can be an aliphatic radical acyclic saturated or unsaturated, linear or branched; a saturated, unsaturated or aromatic, monocyclic or polycyclic carboxyclic or heterocyclic radical. 4 - Method according to one of claims 1 to 3 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents an aryl radical corresponding to the general formula (II)

 in said formula (II) - n is an integer from 0 to 5, preferably from 0 to 3, - R represents R1, one of the following groups or functions  a linear or branched alkyl7 radical having from 1 to 6  carbon atoms, preferably from 1 to 4 carbon atoms,  a linear or branched alkenyl radical having from 2 to 6  carbon atoms, preferably from 2 to 4 carbon atoms,  a linear or branched alkoxy radical having from 1 to 6 atoms  carbon, preferably from 1 to 4 carbon atoms,  a radical of formula -R2-OH  -R2-COOH  -R2-CHO  -R2-N02  -R2-CN  -R2-NH2  -R2-SH  -R2-X  -R2-CF3  in said formulas R2 represents a valential link or a  divalent, linear or branched, saturated or  unsaturated, having from 1 to 4 carbon atoms and X symbolizes a  halogen atom, especially a chlorine or bromine atom. - R represents R3 one of the more complex radicals following a radical

 in which R1 and R2 have the meaning given above and m is an integer from 0 to 3,. a radical -R2-A-R4 in which R2 has the meaning given above, R4 represents a linear or branched alkyl radical having from 1 to 6 carbon atoms, preferably from 1 to 4 carbon atoms or a radical

 and A symbolizes one of the following groups -O-, -CO-,

 -S-, -SO2-, in these formulas R5 represents a hydrogen atom or a linear or branched alkyl radical having from 1 to 4 carbon atoms. 5 - Process according to claim 4 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents an aryl radical corresponding to the general formula (II) in which n is greater than 1 and the radicals R are identical or different and two successive carbon atoms of the benzene ring are linked together by a ketal bridge, preferably by a methylene or ethylene extranuclear radical. 6 - Method according to one of claims 4 and 5 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents an aryl radical corresponding to the general formula (II) in which  - n is equal to 0, 1, 2 or 3,  - R represents one of the following function groups  . a linear or branched alkyl radical having from 1 to 4  carbon atoms,  . a linear or branched alkoxy radical having from 1 to 4  carbon atoms,  . a methylene or ethylene dioxy radical,  . an -OH group,  . a -CHO group,  . a phenyl or benzyl radical,  . a halogen atom. 7 - Method according to one of claims 1 to 3 characterized in that the a-trihalogenated secondary alcohol corresponds to formula (I) in which Q represents a saturated carbocyclic radical or comprising 1 or 2 unsaturations in the cycle, having generally from 3 to 7 carbon atoms, preferably 6 carbon atoms in the ring, said ring possibly being substituted by 1 to 5 radicals R1, preferably 1 to 3, R1 having the meanings set out previously in claim 4. 8 - Process according to claim 7 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents a cyclohexyl or cyclohexene-yl radical, optionally substituted by linear or branched alkyl radicals, having from 1 to 4 carbon atoms. 9 - Method according to one of claims 1 to 3 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents an alkyl, alkenyl, alkadienyl, alkynyl, linear or branched radical having preferably from 1 to 12 carbon atoms; the hydrocarbon chain possibly being interrupted by one of the following groups -O-, -COO-,

 -S-, -SO2-, in these formulas R6 represents hydrogen or a linear or branched alkyl-- radical having from 1 to 4 carbon atoms, preferably a methyl or ethyl radical - and / or carrying l '' one of the following substituents  -OH, OOH, -CHO, NO2, -CN, -NH2, -5H7 -X, -CF3 10 - Process according to claim 9 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents an acyclic, saturated or unsaturated, linear or branched aliphatic radical carrying a cyclic substituent, said acyclic aliphatic radical possibly being linked to the ring by a valential bond or by one of the following groups  +, -CO-, -COO-,

 -S-, -502-, in these formulas, R6 having the meaning given previously in claim 9. 11 - Process according to claim 10 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents an acyclic aliphatic radical, saturated or unsaturated, linear or branched carrying a cycloaliphatic substituent, aromatic or heterocyclic optionally carrying from 1 to 5 R1 radicals, identical or different, as defined in claim 4. 12 - Method according to one of claims 1 to 3 characterized in that the a-trihalogenated secondary alcohol corresponds to the general formula (I) in which Q represents a monovalent heterocyclic radical, saturated or not, comprising in particular 5 or 6 atoms in the ring including 1 or 2 heteroatoms such as nitrogen, sulfur and oxygen atoms, the carbon atoms of the heterocycle possibly being substituted, in whole or in part only by radicals R1, R1 having the meaning given previously in claim 4. 13 - Method according to one of claims 1 to 12 characterized in that the a-trihalogenated secondary alcohol is  - 3,4-dimethoxyphenyltrichloromethylcarbinol  - 3-methoxy-4-hydroxyphenyltrichloromethylcarbinol  - 4-hydroxyphenyltrichloromethylcarbinol  - 3,4-dihydroxyphenyltrichloromethylcarbinol  - 3,4-methylenedioxyphenyltrichloromethylcarbinol  - 4-methyl-1,1,1-trichloro-3-pentene-ol-2  - 4-tert-butylphenyltrichloromethylcarbinol  - 4-isopropylphenyltrichloromethylcarbinol 14 - Method according to one of claims 1 to 13 characterized in that the tertiary amine corresponds to the general formula (III)

 in said formula Rg, Rg, R10, identical or different, represent - a linear or branched, saturated or unsaturated aliphatic radical having from 1 to 12 carbon atoms and / or a saturated or unsaturated cycloaliphatic radical having from 3 to 7 carbon atoms in the ring, - the radicals Rg, Rg, R10 can together form an alkylene, alkenylene or alkadienylene radical comprising from 4 to 6 atoms including, optionally one to three nitrogen atoms and thus constituting a nitrogen heterocycle, monocyclic or polycyclic, saturated or unsaturated . 15 - Process according to claim 14 characterized in that the tertiary amine corresponds to the general formula (III) in which the radicals Rg, Rg, R10 are aliphatic radicals, the hydrocarbon chain can be interrupted by an oxygen atom or nitrogen or be carrying a halogen atom and / or a substituent such as an organic function, in particular -OH or -NH2. 16 - Method according to one of claims 14 and 15 characterized in that the tertiary amine corresponds to the general formula (III) in which the radicals Rg, Rg and R10 identical or different are linear or branched alkyl radicals having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. 17 - Method according to one of claims 1 to 16 characterized in that the tertiary amine used has a pka measured at 250C greater than or equal to 6.0. 18 - Method according to one of claims 1 to 17 characterized in that the tertiary amine corresponding to the general formula (III) is triethylamine, tributylamine, N, N-dihexylethylamine, triethylenediamine. 19 - Method according to one of claims 1 to 18 characterized in that the polar aprotic solvent is N-methylpyrrolidone (NMP), diethylformamide (DMF), dimethylsulfoxide (DMSO), hexamethylphosphotriamide (HMPT), dimethylacetamide (DMAC), tetramethylurea, sulfolane, nitromethane. 20 - Method according to one of claims 1 to 19 characterized in that the third solvent is an aliphatic or aromatic hydrocarbon, a halogenated aliphatic or aromatic hydrocarbon. 21 - Method according to one of claims 19 and 20 characterized in that the third solvent represents from 0 to 100% by weight of the polar aprotic solvent and, preferably, from 0 to 50 by weight. 22 - Method according to one of claims 19 to 21 characterized in that the organic solvent is N.M.P., H.M.P.T., D.M.F., sulfolane, optionally mixed with chlorobenzene. 23 - Method according to one of claims 1 to 22 characterized in that the concentration of a-trihalogenated secondary alcohol in the organic solvent varies between 0.1 and 10 mol / liter, preferably between 1 and 2 mol / liter. 24 - Method according to one of claims 1 to 23 characterized in that the tertiary amine / a-trihalogenated secondary alcohol molar ratio varies from 0.1 to 10, preferably from 0.5 to 2.0. 25 - Method according to one of claims 1 to 24 characterized in that the reaction temperature is between 1000C and 2000C, preferably between 1400C and 1700C.