FR2577920A1 - Process for the preparation of acetals - Google Patents

Abstract

Process for the preparation of dialkyl acetals of alkanals or oxyalkanals by reaction of an alkyl or arylalkyl halide, an alkanol and a mixture of carbon monoxide and hydrogen, under pressure, in the presence of a carbonylated derivative of cobalt and an inorganic base insoluble in the reaction mixture. This process is particularly well suited to the preparation of lower dialkyl acetals of phenylacetaldehyde used in perfumery.

Description

PROCESS FOR PREPARING ACETALS
The present invention relates to a process for preparing acetals from aliphatic halides.

 Acetals are products that find many uses in organic chemistry, especially as synthesis intermediates or directly in perfumery (phenylacetaldehyde acetals).

In the French patent application No. 80 07333 published under the
No. 2,453,127 and in copending application No. 81 21,174 published under No. 2,493,835 it has been proposed to prepare the acetal dimethyl acetal by reaction of methanol with a mixture of hydrogen / carbon monoxide in the presence of cobalt and nickel, a halogen or a halide and a trivalent phosphorus compound.

Despite the use of a complex catalyst system, obtaining good yields of acetal is subject to the use of pressures of the order of 200 to 500 bar.

On the other hand, obtaining acetals from phenylacetaldehyde and its substitution derivatives is laborious. Thus
SIGMUND et al., Monat. 277 (1928) prepared the diethyl acetal of phenylacetaldehyde directly by reaction of the latter with ethanol using the method of E. FISHER et al., Ber. 39, 3053 (1906); This process leads to an acetal yield of 54% of the theory which robs it of any industrial interest. Other authors such as
FF BLICKE et al., J. Am. Chem. Soc. 65, pages 1967-1969 (1943) have prepared to prepare the diethyl acetal of phenylacetaldehyde from benzyl chloride magnesian.This process involves the preliminary preparation of a benzylmagnesium halide and then the reaction of the latter with the Lcf ethyl orthoformate. also Bull. Soc.

Chim. Fr. (4) 39 pages 914-915 and English patent 823,958]. This process is of limited industrial interest. To overcome the disadvantages of the processes described in US Pat. No. 2,856,431, a process for the preparation of acetals of phenylacetaldehyde by the oxidation of cyclooctatetene to phenylacetaldehyde by means of a paracid followed by the acetalization of the aldehyde with an alcohol in the form of an alcohol. presence of a strong acid; German Pat. No. 1,077,650 has advocated reacting an alcohol with a dialkoxy-7,8-bicyclo (4,2,0) octadiene-2,4 in the presence of a strong acid. disadvantage of starting from uncommon raw materials.

 In European Patent Application No. 0 109 679 there is described a process for the somultaneous preparation of phenylacetaldehyde and alkyl phenylacetate by reaction of a benzyl halide with hydrogen, carbon monoxide and a base in the presence a cobalt carbonyl derivative as catalyst and an aliphatic alcohol, at a temperature of 30 to 80 ° C and at pressures of 2 to 50 bar of a carbon monoxide / hydrogen mixture with a molar ratio between 20/1 eVl0 .

The bases used in this process may be inorganic (sodium hydroxide, potassium hydroxide, alkali carbonates, alkaline carboxylates) or organic (amines or ammonium carboxylates). Under these conditions, and despite the presence of an alkanol, the formation of the phenylacetaldehyde diakyl acetal is not reported.

 Because of the industrial advantages of synthesizing organic carbonyl compounds by reaction of organic halides with carbon monoxide and possibly hydrogen it was particularly interesting to develop a direct process for the preparation of acetals from alkyl or arylalkyl halides. The subject of the present invention is therefore a process for the direct preparation of aliphatic or arylaliphatic aldehyde acetals from an alkyl or arylalkyl halide, an alkanol and a carbon / hydrogen oxide mixture. This method has the advantage of avoiding the implementation of a first step of preparing the aldehydes followed by an acetalization step; in particular, in the case of the preparation of the dialkyl acetals of phenylacetaldehydes, the process according to the invention makes it possible to avoid the sequence of a hydrocarbonylation step of the halides and of a step of acetalization of the aldehyde separation of the latter from the hydrocarbonylation medium. The process according to the invention is particularly advantageous in this respect because phenylacetaldehydes are unstable substances which are difficult to distil.

 More specifically, the subject of the present invention is a process for preparing dialkyl acetals of alkanals or arylalkanes, characterized in that an alkyl or arylalkyl halide, an alkanol and an oxide mixture are reacted. of carbon and hydrogen under pressure, in the presence of a carbonyl derivative of cobalt of a mineral base insoluble in the reaction medium and the reaction conditions being chosen so that throughout the duration of the reaction a reaction at least part of the cobalt is present in the form of dicobaltoctacarbonyl.

dans laquelle
- n est un nombre entier de 1 à 3,
- R1 représente un atome d'hydrogène ou un radical alkyle inférieur (ayant de là 4 atomes de carbone) ; un radical halogéno- ou perhalogénoalkyle inférieur ; un radical alkoxy inférieur ; un groupe nitro, hydroxy, hydroxycarbonyle, alcoxycarbonyle ; un atome d'halogène.The starting halides can be represented by the general formula
R - CHz - X (I) in which
X represents a halogen atom such as chlorine, bromine and iodine;
R represents a hydrogen atom; an alkyl radical having from 10 carbon atoms; a naphthyl radical; a phenyl radical of general formula

in which
n is an integer from 1 to 3,
R1 represents a hydrogen atom or a lower alkyl radical (having from 4 to 4 carbon atoms); a halogeno- or perhalo-lower alkyl radical; a lower alkoxy radical; nitro, hydroxy, hydroxycarbonyl, alkoxycarbonyl; a halogen atom.

Examples of R 1 radicals that may be mentioned include methyl, ethyl, isopropyl, isobutyl, chloromethyl, trichloromethyl, trifluoromethyl, methoxy, ethoxy, methoxycarbonyl, ethoxycarbonyl and the chlorine, bromine and fluorine atoms. When n is greater than 1, the radicals R1 may be identical or different.

 Among the radicals R, mention may be made more particularly of the methyl, ethyl, n-butyl, isobutyl, n-pentyl, n-hexyl, o-naphthyl, 13-naphthyl, phenyl, 2-methylphenyl and 4-methylphenyl radicals. 2-ethylphenyl, 3-trichloromethylphenyl, 3-trifluoromethyl-phenyl.

 As specific examples of halides suitable for carrying out the process according to the invention, mention may be made of: methyl chloride, methyl iodide, ethyl bromide, benzyl chloride, benzyl bromide, bensyl iodide, trichloromethyl-3-benzyl chloride, trifluoromethyl-3-benzyl chloride, methyl-3-benzyl chloride.

dans laquelle R a la signification donnée ci-avant et R2 représente un reste alkyle comportant de là 10 atomes de carbone et, de préférence, de 1 à 4 atomes de carbone ; comme exemples de radicaux R2 on peut citer les groupes méthyle, éthyle, n-propyle, isopropyle, n-butyle, isobutyle, n-pentyle, éthyl-o2 hexyle, n-décyle.The process according to the invention makes it possible to prepare acetals of general formula

wherein R has the meaning given above and R2 represents an alkyl radical having from 10 carbon atoms and preferably from 1 to 4 carbon atoms; examples of radicals R 2 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, ethyl-o 2 hexyl, n-decyl.

dans laquelle R1, R2 et n ont la signification donnée ci-avant.The process according to the invention is particularly well suited to the preparation of 1,1-dialkoxy-2-arylethanes and more especially to that of 1,1-dialkoxy-2-phenylethanes of general formula

in which R1, R2 and n have the meaning given above.

 Examples of acetals which may be prepared by the process of the invention include: dimethyl and diethyl acetals of acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde; 1,1-dimethoxy-2-phenylethane; diethoxy-1,1-phenyl-2-ethane; 1,1-diisopropyloxy-2-phenylethane; 1,1-diethoxy (2-chlorophenyl) ethane; 1,1-diethoxy (3-chlorophenyl) ethane; 1,1-diethoxy (4-methylphenyl) ethane; 1,1-diethoxy (3-methoxyphenyl) ethane; 1,1-diisopropyloxy (4-methoxyphenyl) ethane; diethoxy-1,1,4-tert-butylphenyl-2-ethane; 1,1-diethoxy (2-hydroxyphenyl) ethane; diethoxy-1,1-trichloromethyl-3-phenyl-2-ethane; 1,1-diethoxy (4-trifluoromethylphenyl) -2 ethane.

The alkanols which are involved in the process according to the invention preferably correspond to the general formula
R2 - OH (v) in which R2 has the meaning given above. Inferior alkanols are more particularly used, and preferably alkanols containing from 2 to 4 carbon atoms.

Without the scope of the present invention being limited to a particular mechanism, the present process can be represented by the following reaction scheme

+ H2O + BH + + X (1)
The choice of the base is one of the critical factors for the orientation of the reaction towards the preponderant formation of acetal. The presence of a base is necessary to cause formation in the reaction medium tetracarboylcobaltate ion (-l) necessary for the course of the hydrocarbonylation reaction.However it has been found that the orientation of the reaction to the preponderant formation of acetal also depends on the presence in the reaction medium of tetracarbonylcobelt hydride [HCO (CO) 4]. The base should therefore be selected from those which do not cause the rapid disappearance of the tetracarbonylcobalt hydride formed under the reaction conditions from the carbonyl derivative of cobalt; the absence of this species in the resonance medium directs the reaction towards the predominant formation of ester by carbonylation of the halide and / or towards the predominant formation of aldehyde by hydrocarbonylation. On the other hand a base reacting too slowly with the tetracarbonylcobalt hydride to form the corresponding salt causes the loss of a portion of the catalyst, which results in a stop of the reaction. The bases which meet the requirements formulated above are mineral bases which are practically insoluble in the reaction medium and in particular those taken in the group of alkaline carbonates and bicarbonates, basic alkali metal phosphates and alkaline earth hydroxides. among the bases which are suitable for carrying out the process according to the invention: sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, lithium carbonate, lime, disodium and dipotassium phosphates such as
Na2HPO4; Na2HPO4, 12H2O; Na2HPO4, 7H2O; N 8H 2 O; Na2HPO4, 2H2O; K2HPO4; K2HPO4, 3H2O
K2HPO4, 1H2O; hydrated trisodium and tripotassium phosphates such as Na3PO4, 0.5H2O; Na3PO4, 6H2O; Na3PO4, 8H2O Na3PO4, 12H2O. Alkaline carbonates and bicarbonates and alkaline phosphates are preferably used. The aforementioned bases are used in the form of particles of varying average size depending on their nature. The particle size of the base is chosen so as not to provoke under the conditions of the reaction too rapid neutralization of the tetracarbonylcobalt hydride. The appropriate particle size can readily be determined according to the other reaction conditions and the nature of the base by simple tests in each particular case.

 The amount of base, expressed in equivalents per mole of alkyl halide or arylalkyl, is preferably close to the stoichiometry of the reaction as represented by the reaction scheme (1), that is to say close to one equivalent of base per mole of halide. However, it is possible to deviate substantially from the stoichiometric quantity; thus the amount of base can be between 0.8 and 4 equivalents of base per mole of halide.

 The carbonyl derivatives of cobalt used as catalysts in the process of the invention are among those capable of generating, under the reaction conditions, the catalytic species which make it possible and which direct it towards the predominant formation of acetals. , ie, dicobaltoctacarbonyl, tetracarbonylcobalt hydride and salts thereof. Suitable carbonyl derivatives of cobalt for this purpose may be selected from the group consisting of tetracobaltdodecarbonyl, dicobaltoctacarbonyl, alkaline salts, alkaline -terrous or onium of tetracarbonyl hydrobromide such as tetracarbonylcobaltate (-l) sodium, lithium, potassium, ammonium or quaternary phosphonium.

2 HCo(CO)4 (2) XCb(CO)4 + MB

The amount of catalyst expressed in atomgram of metal per mole of halide is preferably at least 0.001 at-g of metal per mole of halide. There is no critical upper value of the amount of catalyst; however, it is of no interest to use more than 0.5 gram atom of metal per mole of halide. In practice, a quantity of catalyst representing from 0.01 to 0.1 μg of metal per mole of halide is suitable. Whatever the nature of the catalyst used, it has been found that it is important for the orientation of the reaction towards the predominant formation of the reaction that at least part of the cobalt present in the reaction medium is in the form of dicobaltoctacarbonyl. Indeed, under the conditions of the reaction, this compound gives rise to the tetracobaltoctacarbonyl hydride and its salts necessary for the course of the reaction and its orientation. the formation of these catalytic entities is illustrated by the following reaction schemes
Co2 (CO) 8 + H2

2 HCo (CO) 4 (2) XCb (CO) 4 + MB

MCo (CO) 4 + BH (3) in which MB represents the base used. It is therefore preferable that at least 5% by weight of the cobalt present in the medium, and preferably at least 10%, remains in the form of dicobaltoctacarbonyl for the duration of the reaction.

 the amount of alkanol used to carry out the present process may vary within wide limits. It is at least close to the stoichiometric amount, that is to say 2 moles of ethanol per mole of organic halide. However, it is generally preferable to use an excess of alcohol to promote the formation of the acetal; the minimum amount of alkanol is preferably at least twice the stoichiometric amount. The maximum amount of alkanol depends on its nature. Thus, there is no upper limit of the amount of alkanol when the latter has a dielectric constant at 200 ° C lower than 30. In this case the alkanol can be used as the reaction medium. when the starting alcohol has a dielectric constant greater than 30, which is the case of methanol, it is preferable not to carry out an excessive excess of alcohol so as not to give the reaction medium a dielectric constant at 200C exceeding the value of 30.

 As indicated above, the smooth running of the reaction depends on the presence of at least a portion of the cobalt in the form of Co 2 (CO) 8.

2/3 Co2+ + 4/3 -Co(O0)4 + 8/3 oe (4)
lorsque les conditions de cette dismutation sont réunies, la présence de la base nécessaire au déroulement de la réaction contribue à déplacer l'équilibre de cette réaction vers la droite et favorise la disparition du dicobaltoctacarbonyle sous forme de sel ou d'hydroxyde de cobalt(2+) qui précipite et de sel de l'hydrure de tétracarbonylcobalt insuffisant à lui seul pour favoriser la formation de l'acétal.Le maintien de la constante diélectrique du milieu réactionnel mesurée à 20 C à une valeur inférieure ou égale à 30 environ et de préférence à une valeur inférieure ou égale à 25 environ est une mesure qui permet précisément de limiter, voire même d'éviter, la dismutation du dicobaltoctacarbonyle nécessaire à la formation des entités catalytiques que sont l'hydrure de tétracarbonylcobalt et ses sels. La valeur de la constante diélectrique du milieu dépend de celles des réactifs en présence et en particulier de celle de l'alcanol et de la présence d'eau. It is therefore necessary to avoid or limit any parasitic reaction of transformation of dicobaltoctacarbonyl under the conditions of the reaction, and in particular the disproportionation of dicobaltoctacarbonyl according to the reaction scheme Co2 (oe) 8

2/3 Co2 + + 4/3 -Co (O0) 4 + 8/3 oe (4)
when the conditions of this disproportionation are met, the presence of the base necessary for the progress of the reaction contributes to shift the equilibrium of this reaction to the right and favors the disappearance of dicobaltoctacarbonyl in the form of salt or cobalt hydroxide (2 +) which precipitates and salt of tetracarbonylcobalt hydride insufficient alone to promote the formation of the acetal.The maintenance of the dielectric constant of the reaction medium measured at 20 C to a value less than or equal to about 30 and Preferably at a value of less than or equal to about 25 is a measure which makes it possible precisely to limit, or even to avoid, the disproportionation of the dicobaltoctacarbonyl necessary for the formation of the catalytic entities that are tetracarbonylcobalt hydride and its salts. The value of the dielectric constant of the medium depends on those of the reagents in the presence and in particular that of the alkanol and the presence of water.

 Although it is preferable to operate in the absence of water, it is difficult to conduct the reaction in a completely anhydrous medium. Indeed variable amounts of water can be provided by the reagents and are added to the water resulting from the reaction; this is particularly true of the water of crystallization provided by the trisodium and tripotassic phosphates. In this case, the decrease in the base concentration in the medium would make it possible to reduce the dielectric constant, but this measure would result in a decrease in the productivity of the reaction. The use of a solvent with a dielectric constant of less than or equal to about 30 and preferably less than or equal to 10 is therefore a particularly suitable measure for the solution of this problem. Aliphatic or cyclocaliphatic hydrocarbons are particularly particularly suitable for this purpose. saturated aromatic hydrocarbons and halogenated aromatic hydrocarbons. more specifically: alkanes and cycloalkanes such as n-heptane, n-hexane, n-octane, cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylenes; halogenated aromatic hydrocarbons such as chlorobenzene and chlorotoluenes. The amount of the solvent third is determined so as to obtain both a dielectric constant at 20 ° C. of less than 30 ° C. and preferably less than 25 ° C. and a productivity as high as possible of the reaction.

 The temperature at which the reaction is conducted can vary within wide limits. In general, this temperature may be in a range of from 20 to 150 ° C. and preferably from 50 to 120 ° C.

 The total pressure at which the reaction is carried out is at least 30 bars and preferably 43 bars. The best results are obtained for total pressures of at least 50 bar. The partial pressures of hydrogen and carbon monoxide are selected to promote the formation of tetracarbonylcobalt hydride according to the reaction scheme (2) and to contribute to the limitation of the disproportionation reaction of dicobaltoctacarbonyl according to the reaction scheme. (4).

From this point of view it is preferable that the partial pressure of carbon monoxide is at least 10 bars, the hydrogen partial pressure must then be at least equal to that required to reach the minimum total pressure specified above. . There is no critical upper value of the total pressure. From a practical point of view, it is generally not necessary to use a total pressure greater than 120 bar
Depending on the conditions of the reaction, the formation of the acetal is accompanied by that of varying amounts of the corresponding aldehyde and the ester resulting from the oxyalkoxycarbonylation of the halide and, if appropriate, an alcohol (phenyl- 2 ethanols for example).

 On a practical level, the mixture obtained at the end of the reaction is treated with an aqueous solution of hydrochloric acid and an oxidant (hydrogen peroxide for example) in order to oxidize the cobaltcarbonyl derivatives to cobalt chloride and then the aqueous phase containing the latter is separated from the organic phase which is treated by the usual processes (distillation, extraction) to recover the acetal formed. Alternatively the catalyst may be separated from the reaction mass by passage over an anion exchange resin.

 The process according to the invention is particularly suitable for continuous use.

 The following examples illustrate the invention and show it can be put into practice.

EXAMPLES 1 and 2
In a stainless steel autoclave 125 ml capacity, equipped with a dip tube for withdrawal of the reaction medium, it is charged
. 50 mM benzoyl chloride
. ethanol 24 ml
toluene 16 ml
Co2 (CO) 8 3.45 m.at.g
.base 25 mM.

 A total pressure of 41 bars of an equimolar mixture of carbon monoxide and hydrocene is admitted and the contents of the autoclave are then heated to 80 ° C. by means of an annular furnace while maintaining stirring. the pressure rises to 50 bar and is maintained at this value by feeding an equimolar mixture of carbon monoxide and hydrogen.

When 44 mM of carbon monoxide and hydrogen had been absorbed, the gas supply was cut off and then the autoclave was cooled to room temperature. By keeping the contents under pressure from CO and
H2 is made of reaction mass samples which are subjected to analysis by infra-red spectrometry. In this way it is possible to detect and assay the cobaltcarbonyl derivatives present in the medium. The analysis shows the presence of CD2 (CD) 8, Co (CO) 4 and C6H5-CH2CO-Co (CO) 4 resulting from the reaction of sodium tetracarbonylcobaltate (-1) with carbon monoxide. analysis allows to calculate the molar ratio of Co2 (CO) 8 present relative to the anion tetracarbonylcobestate (-1) free and in the form of
C6H5-CH2-CO-Co (CO) 4 and the molar ratio of diethoxy-1,1-phenylethane formed (DPE) to formed phenylacetaldehyde (PA). The tetracarbonylcobalt hydride, an intermediate necessary for orienting the reaction to the predominant formation of acetal, can not be assayed on the samples taken because the analysis is carried out at normal pressure, which causes the hydride to be converted into dicobaltoctacarbonyl.

The results obtained are recorded in the following table

<tb> EXAMPLES <SEP> BASE <SEP> DPE / PA <SEP> Co2 (CO) 8 <SEP> / <SEP> A (1)
<tb> 1 <SEP> Na2CO3 <SEP> 10.6 <SEP> 0.30
<tb> 2 <SEP> Na3PO4 · 0.5H2O <SEP> 6.2 <SEP> 0.33
<tb> (1) A = Co (CO) 4 total including tetracarbonylcobaltate anion (-1)
free and that combined in the form of C6H5-CH2-CO-Co (CO) 4.

 By way of comparison, Examples 1 and 2 were repeated after replacing sodium carbonate and sodium phosphate with an equivalent amount of lime having an average particle size of less than 0.2 mm. In these circumstances the ratio DPE /? A. a - was about 0.003 and the ratio Co2 (CO) 8 / Co (CO) 4 expressed as above zero.

EXAMPLE 3
In an autoclave with a capacity of 80 ml, 4.76 g of sodium carbonate (44.9 mMol) having a particle size distribution are charged.
between 0.4 and 0.8 μm - 32 ml of absolute ethanol - 4.07 g of distilled benzyl chloride (32.2 mmoles) - 0.4 g of dicobalt octacarbonyl (2.34 mgtg).

 A total pressure of 79 bar of an equimolar mixture of carbon monoxide and hydrogen (CO / H 2 = 1) is admitted and the autoclave is then heated to 800 ° C. by means of an annular furnace, with stirring at 20 ° C. about min.

 The temperature pressure is maintained constant and equal to 95 bars by continuously feeding an equimolar mixture of carbon monoxide and hydrogen.

 After cooling and degassing the autoclave, the reaction mixture is analyzed by gas chromatography. The results show a complete conversion of benzyl chloride and a major formation of diethoxy-1, 1-phenyl-2-ethane.

 The area of the peak of the chromatogram corresponding to the DPE represents 89% of the total area of the peaks and that corresponding to phenylacetaldehyde 7% of the total area.

The reaction solution is treated by passing through 20 ml of a quaternary ammonium resin (known under the trademark
AMBERLYST A 26) under argon to remove the catalyst. The filtrate thus obtained is then subjected to distillation under approximately 20 mm of mercury in order to expel methanol and then under a reduced pressure of 5 mM of mercury to recover diethoxy-1, 1-phenylethane. This gives a fraction weighing 3 g of a product distilling between 85 and 900C consisting of 1,1-diethoxy-phenylethane identified by proton NMR.

EXAMPLE 4
The procedure is as in Example 3 after replacing benzyl chloride with 4-methyl benzoyl chloride. The conditions and the results obtained are recorded below - ethanol 50 ml - 4-methyl-benzyl chloride 7.03 g (50 mMoles) - 70 mMoles Na2CO3 (particle size of 0.2
0.315 mm) - Co2 (CO) 8 0.49 g (2.92 m.at-g cobalt) - temperature 80 C - total pressure 95 bar - time 45 min - conversion rate of methyl-4-benzyl chloride : 100%
The distribution of the different products formed expressed as percentage of peak area is as follows - 1,1-diethoxy (4-methylphenyl) ethane: 90% - 4-methylphenylacetaldehyde: 8% - ethyl-4-methylphenylacetate : 2%.

EXAMPLES 5 to 6
It was operated as in Example 3 but by varying the temperature. The results obtained are recorded in the following table

<tb>: <SEP>: Distribution <SEP> of <SEP> products <SEP> formed <SEP> (2):
<tb> Examples <SEP>: <SEP> TOC <SEP>: <SEP> Time <SEP>: <SEP> TT <SEP>. <September>
<Tb>

: <SEP>: <SEP>: <SEP> mn <SEP>: <SEP> (1) <SEP>: <SEP> DPE <SEP>% <SEP>: <SEP> PA <SEP>% <SEP> : <SEP> PAE <SEP> (3) <SEP>%
<tb>: <SEP> 5 <SEP>: <SEP> 60 <SEP>: <SEP> 180 <SEP> -: <SEP> 91 <SEP>: <SEP> 79 <SEP>: <SEP> 12 <SEP>:<SEP> 2,4
<tb>: <SEP> 6 <SEP>: <SEP> 100 <SEP>: <SEP> 49 <SEP>: <SEP> 86 <SEP> 9 <SEP><SEP> 83 <SEP>: <SEP> 6.6 <SEP>: <SEP> 1.5
(b) (1) conversion rate of benzyl chloride (2) expressed as in Example 3 (3) ethyl phenylacetate.

EXAMPLES 7 to 8
We operate as in Example 3 by varying the amount of
Co2 (CO) 8. The results obtained are recorded in the following table

<tb> Distribution <SEP> of <SEP> products <SEP>%
<tb> Examples <SEP> Co2 (CO) 8 <SEP> time <SEP> in <SEP> TT <SEP>% <SEP> RT <SEP> DPE <SEP> RT <SEP> PA <SEP> RT <SEP > PAE
<tb> m <SEP> at -g <SEP> of <SEP> Co <SEP> mn
<tb> 7 <SEP> 5 <SEP> 25 <SEP> 100 <SEP> 87 <SEP> 8 <SEP> 1,3
<tb> 8 <SEP> 1 <SEP> 180 <SEP> 100 <SEP> 75 <SEP> 20 <SEP> 1,2
<Tb>
EXAMPLE 9
The procedure is as in Example 1 but in the presence of 20 ml of toluene, an amount of Na2CO3 of 2.65 g (25 mmol) and a pressure of 50 bar (molar ratio H2 / CO = 1).

 The reaction time was 80 minutes and the degree of conversion of benzyl chloride 100%.

 The yields of DEPE, PA and PAE relative to the transformed benzyl chloride (RT) amounted to 73, 11 and 4%, respectively.

EXAMPLE 10
The procedure was as in Example 3 after replacing Na2CO3 with 45 mMoles of NaHCO3. The following results were obtained: 60 minutes. TT: 100%.
The distribution of the formed products expressed as in Example 3 is as follows: DEPE: 79% - PA: 18% - PAE: 1%.

EXAMPLE 11
In a 125 ml autoclave, 50 ml of methyl iodide were charged with ethanol (7.1 g, 50 mMoles), 7.42 g of Na2CO3 (70 mMoles), and Co2 (CO) 8 500 mg (2.92 m.sup.3). g of Co).

The autoclave is closed and then 79 bars of a mixture are introduced
H2 / CO containing 2 moles of hydrogen per 1 mole of CO. The autoclave is stirred and the temperature raised to 80 C. The pressure is maintained at 95 bars by continuous admission of an equimolecular mixture of hydrogen and oe. After 30 minutes the absorption of CO / H2 ceases. The autoclave is cooled and degassed. The reaction mass is analyzed as in Example 1. The analysis shows the following results - TT methyl iodide: 100% - acetaldehyde acetaldehyde RT: 73% - RU acetaldehyde: 8% - RT acetate ethyl: 19%.

EXAMPLES 12 to 17
The procedure of Example 3 was carried out under the following conditions by varying the nature of the benzyl chloride base 50 mM - ethanol 24 ml (412 mM) - toluene 16 ml - Co2 (CO) 8 3 , 45 m.at.g - temperature 800C - pressure 50 bar H2 / CO ratio = 1
The nature and quantity of the base, the duration of the reaction and the results obtained are recorded in the following table

: <SEP><SEP>:<SEP>:<SEP>.<SEP> Repair <SEP> of <SEP> products
<tb>: <SEP>: <SEP> BASE <SEP>: <SEP>: <SEP>: <SEP> formed
<tb> EXAMPLES <SEP> Time <SEP> TT
<tb> Nature <SEP> Quantity <SEP> in <SEP>% <SEP> DPE <SEP> PA <SEP> PAE
<tb> in <SEP> mM <SEP> mn <SEP>% <SEP>% <SEP>%
<tb> 12 <SEP> Ca (OH) 2 * <SEP> 25 <SEP> 90 <SEP> 24 <SEP> 90 <SEP> 10 <SEP>
<tb> 13 <SEP> Na2CO3 <SEP> 25 <SEP> 60 <SEP> 100 <SEP> 92 <SEP> 8 <SEP>
<tb> 14 <SEP> NaHPO4 <SEP> 50 <SEP> 150 <SEP> 65 <SEP> 93 <SEP> 7 <SEP>
<tb> 15 <SEP> NaPO4,
<tb> 0.5H2O <SEP> 25 <SEP> 80 <SEP> 100 <SEP> 89 <SEP> 11 <SEP>
<tb> 16 <SEP> Na3PO4,
<tb>: <SEP> 1H2O <SEP>: <SEP> 25 <SEP>: <SEP> 80 <SEP>: <SEP> 100 <SEP>: <SEP> 70 <SEP>: <SEP> 25 <SEP >:
<tb>: <SEP> 17 <SEP>: NaPO4, <SEP>: <SEP>: <SEP>: <SEP>: <SEP>: <SEP>:
<tb>: <SEP>: 12H2O <SEP>: <SEP> 25 <SEP>: <SEP> 110 <SEP>: <SEP> 55 <SEP>: <SEP> 50 <SEP>: <SEP> 50 <SEP>:
<tb> * in the form of grains 5 to 6 mm in diameter.

EXAMPLE 18
Example 13 was repeated after replacing dicobaltoctacarbonyl with sodium tetracarbonylcobaltate (-1) (3.43 m.at.g).

 The absorption time was 100 minutes, the degree of conversion of benzyl chloride 100% and the distribution of products formed diethoxy-l, 1 phenyl-2 ethane 87% and phenylacetaldehyde 13%.

EXAMPLES 19 to 21
By operating according to the procedure of Example 3, various examples were made by varying the total pressure and the partial pressures of CO and H 2 as indicated in the following table.

The other conditions of the reaction were as follows: 100 mM benzyl chloride - ethanol 24 ml - toluene 16 ml - dicobaltoctacarbonyl 3.45 m.at.g - Na3PO4, 0.5H2O 50 mM - temperature 80 C

<tb> EXAMPLES <SEP> PRESSURES <SEP> IN <SEP> BARS <SEP> DURATION <SEP> TT <SEP> RT <SEP>%
<tb><SEP> in <SEP>%
<tb> H2 <SEP> CO <SEP> total <SEP> min <SEP> DPE <SEP> PA <SEP> PAE <SEP> PE (1)
<tb> 19 <SEP> 25 <SEP> 25 <SEP> 50 <SEP> 270 <SEP> 100 <SEP> 41 <SEP> 39 <SEP> 1 <SEP> 8
<tb> 20 <SEP> 25 <SEP> 12 <SEP> 37 <SEP> 100 <SEP> 67 <SEP> 24 <SEP> 54 <SEP> 1 <SEP> 9
<tb> 21 <SEP> 38 <SEP> 12 <SEP> 50 <SEP> 220 <SEP> 100 <SEP> 47 <SEP> 35 <SEP> 1 <SEP> 8
<tb> (1) phenylethanol EXAMPLES 22 to 23
Example 21 was repeated first by increasing the proportion of ethanol relative to toluene (30 ml of ethanol per 10 ml of toluene) and then simultaneously decreasing the amount of base (25 mM instead of 50 mM). and benzoyl chloride (50 mM instead of 100) so as to reduce the amount of water provided by the trisodium phosphate. The other conditions are those of Example 21. The results are given in the following table.

RT
<tb> EXAMPLES <SEP> Chloride <SEP> of <SEP> Ethanol <SEP> Toluene <SEP> Na3PO4, <SEP> 0.5H2O <SEP> Duration <SEP> TT
<tb> benzyl <SEP> to <SEP> mM <SEP> to <SEP> ml <SEP> to <SEP> ml <SEP> to <SEP> mM <SEP> to <SEP> mn <SEP> DPE <SEP >% <SEP> PA <SEP>% <SEP> PAE <SEP>% <SE> PE <SEP>%
<tb> 22 <SEP> 100 <SEP> 30 <SEP> 10 <SEP> 50 <SEP> 160 <SEP> 94 <SEP> 47 <SEP> 36 <SEP> 1 <SEP> 8
<tb> 23 <SEP> 50 <SEP> 30 <SEP> 10 <SEP> 25 <SEP> 60 <SEP> 99 <SEP> 75 <SEP> 11 <SEP> 1.4 <SEP> 4
<Tb>

Claims (5)

 10) Process for preparing dialkyl alkketals of alkanals or arylalkanes, characterized in that an alkyl or arylalkyl halide, an alkanol and a mixture of carbon monoxide and hydrogen are reacted. under pressure, in the presence of a carbonyl derivative of cobalt of a mineral base insoluble in the reaction medium and the reaction conditions being chosen so that, throughout the duration of the reaction, at least part of the cobalt is present as dicobaltoctacarbonyl.  20) Process according to claim 1, characterized in that a halide of general formula is reacted  R - CH2 - X (I) in which  X represents a halogen atom such as chlorine, bromine and iodine  R represents a hydrogen atom; an alkyl radical having 1 to 10 carbon atoms; a naphthyl radical; a phenyl radical of general formula

 in which :  n is an integer from 1 to 3,  R1 represents a hydrogen atom or a lower alkyl radical; a halogeno- or perhalo-lower alkyl radical; a lower alkoxy radical; nitro, hydroxy, hydroxycarbonyl, alkoxycarbonyl; a halogen atom, with an alcohol of general formula  R2 - OH (V) wherein R2 represents an alkyl radical having 1 to 10 carbon atoms, and a mixture of carbon monoxide and hydrogen to obtain an acetal of general formula  R - CH2 - CH (OR2) 2 (III) in which R and R2 have the meaning given above.  3) Process according to claim 1, characterized in that the dielectric constant of the reaction medium measured at 20 "C is less than or equal to 30.  4) Process according to any one of claims 1 to 3, characterized in that at least 5% by weight of the cobalt present in the medium is in the form of dicobaltoctacarbonyl.  5) Process according to claim 4, characterized in that the base is selected from the group consisting of alkali carbonates and bicarbonates, basic alkali metal phosphates and alkaline earth hydroxides.  60) Process according to any one of claims 1 to 5, characterized in that the amount of base is between 0.8 and 4 equivalents per mole of halide.  7) Process according to any one of claims 1 to 6, characterized in that the cobaltcarbonyl derivative is taken from the group formed by tetracobaltdodecacarbonyl, dicobaltoctacarbonyl, alkaline, alkaline earth or onium salts, of the tetracarbonylcobalt hydrate.  8) Process according to any one of claims 1 to 7, characterized in that the amount of catalyst expressed in gram atom of metal per mole of halide is preferably at least 0.001 at-g of metal per mole of halide.  90) Process according to any one of claims 1 to 8, characterized in that the amount of alkanol is at least close to 2 moles per mole of homehydrogen.  10) Process according to any one of claims 1 to 9, characterized in that the reaction is conducted in the presence of a solvent inert under the reaction conditions and whose dielectric constant at 200C is less than or equal to 30.  11 C) Process according to any one of claims 1 to 10, characterized in that the temperature is between 20 and 150 C.  12) Process according to any one of claims 1 to 11, characterized in that the total pressure of the carbon monoxide / hydrogen mixture is at least 30 bar.