CS197286B2 - Process for preparing alpha-cyanobenzylesteres of alkanoic and cycloalkanoic acids - Google Patents

Abstract

The preparation of the esters of general formula I, having a pesticidal action, in which R is an optionally substituted alkyl or cycloalkyl group and A is a phenoxy, phenylthio or benzyl radical, is carried out by reacting a correspondingly substituted benzaldehyde with an acid halide of the formula R.CO.Hal in the presence of water, a water-soluble cyanide and a water-insoluble aprotic solvent. In accordance with the invention, the yield is increased by the presence of a phase-transfer catalyst, for example an onium compound. <IMAGE>

Description

The invention relates to a process for the preparation of α-cyanobenzyl esters of alkanoic and cycloalkanoic acids, i.e. esters of the so-called "synthetic pyrethroid" type. These esters have insecticidal effects.

It is known in the art, for example from DAS 2,231,312, that synthetic pyrethroid compounds can be prepared by reacting substituted cyclopropanecarbonyl halides with 3-substituted benzaldehydes in the presence of an aqueous solution of sodium cyanide or potassium cyanide. This procedure produces pyrethroids of the type represented by the general formula (I)

It has now been discovered that the yields of esters of the above type of formula (I), as well as other esters belonging to the group of "synthetic pyrethoid" compounds, can be increased and these compounds can be prepared more efficiently if special catalysts are used. .

The invention therefore provides a process for the preparation of the α-cyanobenzyl esters of the alkanoic and cycloalkanoic acids of the general formula II

where

R represents an alkyl group having 1 to 10 carbon atoms and an optionally substituted phenyl group substituted by halogen, or a cycloalkyl group having 3 to 6 carbon atoms, optionally substituted by at least one alkyl, alkenyl or haloalkyl group each having up to 6 atoms carbon and

A represents a phenoxy group, a methylthio group or a benzyl group by reaction of the benzaldehyde of general formula III

where

A is as defined above, with an acid halide of formula IV

R = COHal (IV) wherein

Hal represents a bromine or chlorine atom, in the presence of a water-soluble cyanide and a water-immiscible aprotic solvent, characterized in that the reaction is carried out in the presence of a quaternary onium compound of formula V

R ^{1 —} — X— R ¹ * μ

Y ~ (V) where

X represents a nitrogen, phosphorus or arsenic atom,

R 1, R ^2, R ³ and R ⁴ each represents an alkyl, aralkyl, alkaryl or aryl group and

Y represents a single ion, or sulphonium compounds ^and the Formula, VI

R * _- ¹ . rR — s — rR

Y ~ (VI) where

R ⁵ , R ⁶ and R ⁷ are each alkyl and

Y denotes a monovalent ion as an interfacial catalyst.

The interfacial catalyst may generally be any reagent that is capable of accelerating the phase-to-phase reaction in a two-phase system consisting of water and an organic substance or substances.

In the compounds of formulas V and VI, Y is a monovalent ion, for example a halide ion, such as a chloride, bromide or iodide ion, or an alkyl sulfate ion, such as a methyl sulfate or ethyl sulfate ion.

In a preferred embodiment of the process of the invention, in the compounds of formula (V) and (VI), the alkyl group contains 1 to 18 carbon atoms and the aralkyl and alkaryl groups contain no more than 10 carbon atoms, the aryl group preferably being a phenyl group.

Examples of suitable onium compounds include tetra-n-butylammonium bromide, tetra-n-butylammonium chloride, methyltri-2-methylphenylammonium chloride, tetramethylphosphonium iodide, tetra-n-butylphosphonium bromide, methyltriene-methyl-methylsulfonyl-2-iodide, ethyl-2-iodide. onium methylsulfate, methyldinOnylsulfonium methylsulfate, methyldinonylsulfonium methylsulfonate and n-hexadecyldimethylsulfonium iodide.

Very good results are obtained with the use of quaternary ammonium compounds.

The onion compound may be in the form of a hydroxide or a salt and may be used as a functional part of a lightly basic anion exchange resin that contains a structural moiety (polymer matrix) and a functional moiety (ionic active group). Of particular interest in this regard are polystyrene resins such as copolymers * aromatic monovinyl compounds ^; aromatic polyvinyl compounds, especially styrenedivinylbenzene copolymers. The functional moiety is a quaternary ammonium, phosphonium or arson group. Examples of these strongly basic anion exchange resins that may be used in the process of the present invention are trimethylamine-derived compounds (such as those known under the trade names "Amberlit IRA-400", Aberllt IRA-401 "," Amberlit IRA-402 ',' Amberlit IRA-900 ',' Duollt A-101-D ',' Duolith ES-111 ',' Dowex 11 ',' Dowex 21K 'and' Ionac A-450 '), and the compounds derived from dimethylethanolamine (such as products known under the trade names "Amberlite IRA-410", "Amberlit IRA-911", "Dowex 2", "Duolite A-102-D-", "Ionac A-542" and "Ionac A-550"). Very good results were obtained with trimethylamine-derived compounds.

Other suitable interfacial catalysts are macrocyclic polyethers, known as krowm ethers (crown or ring ethers). These compounds, as well as their preparation, are described in the prior art literature, for example in Tetrahedron Letters No. 18 (1972), pp. 1793 to 1796, generally referred to by the total number of atoms that forms a macrocyclic species, and by indicating the number of oxygen atoms present in the ring. These macrocyclic. polymers whose normal chemical designation is 1,4,7,10,13,16-hexaoxacyclooctadecane * are therefore referred to as "18-ring-6" as described above. Other examples of suitable macrocyclic polyethers are 3,4-benzo-1,6,9,12,15,18,21-heptaoxacyclotricos-3-ene and 3,4-benzo-1,6,9,12-tetraoxacyclotetradec-3. -en. A particularly suitable compound is 18-ring-6.

Other suitable interfacial catalysts are surfactants. These surfactants are defined in Kirk-Othmer, "Encyclopedia of Chemical Technology," Second Edition, Vol. 19 (1969), p. 508, as: "organic compounds containing two different structural groups in the same molecule, one it is soluble in water and the other is insoluble in water '.

The surfactants are preferably nonionic agents, such as poly (alkyleneoxy) derivatives, prepared by reaction of higher alcohols, alkylphenols or fatty acids with ethylene oxide or propylene oxide. Suitable alcohols, alkylphenols or fatty acids contain from 8 to 20 carbon atoms in the alkyl group and the number of alkyleneoxy units ranges from 1 to 50. A particularly preferred nonionic surfactant of the present invention (referred to as "Dobanol 91-6" in the Examples) ) is an agent prepared from a C0-C11 n-alkanol mixture, and also contains an average of six ethyleneoxy units. The nonionic type surfactant mentioned above may be an alkylbenzene containing a straight alkyl chain. Suitable alkylbenzenes for the process of the present invention contain 8 to 20 carbon atoms in the alkyl group.

The molar ratio of the amount of the interfacial catalyst to the amount of the benzaldehyde of formula III can vary within a very wide range, but a ratio ranging from 1: 5 to 1: 500 is preferred. Using low molecular weight ratios requires longer reaction times to complete. while the use of high molar ratios naturally increases the cost of producing a given amount of ester. From the foregoing, it is clear that the choice of reaction time and mole ratio of catalyst to benzaldehyde are interdependent, and will depend on local economic factors in each individual case. Very good results are usually obtained using molar ratios ranging from 1:10 to 1: 100.

A further advantage of the process of the invention is that the molar ratio of the amount of acyl halide (R.CO.Hal) to the amount of benzaldehyde is 1: 1 or slightly exceeds this ratio. The molar ratio is preferably from 1.1: 1.0 to 1.0: 1.0.

The molar ratio of the amount of water-soluble cyanide to the amount of aromatic aldehyde is preferably from 1.5: 1 to 1.0: 1.0, more preferably from 1.3: 1 to Ι, θ ² ? : 1.00. The term "water-soluble cyanide" refers to? water-soluble hydrogen cyanide salt. Of these water-soluble cyanides, alkali metal and alkaline earth metal cyanides are preferred for carrying out the process of the invention. Sodium cyanide is particularly preferred since esters of formula (II) can be prepared in the shortest reaction time.

A suitable temperature for carrying out the process of the present invention is above 0 ° C, and preferably between 10 and 50 ° C. Very good results were obtained at temperatures ranging from 15 to 40 ° C. The process according to the invention is further advantageous in that it can be carried out at ambient temperature, which is particularly advantageous.

Examples of suitable aprotic solvents that are substantially immiscible with water include alkanes or cycloalkanes or mixtures thereof: Particularly suitable examples are n-hexane, n-heptane, n-octane, n-nonane, n-decane and their isomers (e.g., 2-methylpentane, 3-methylpentane, 2-methylhexane, 3-methylhexane, and 2,4-

4-trimethylpentane) and cyclohexane and methylcyclohexane. Also suitable are alkane-rich naphthas, for example naphthas at atmospheric pressure ranging from 40 to 65 ° C, from 60 to 80 ° C, or from 80 to 110 ° C. Very good results were obtained with n-heptane and cyclohexane.

^J: APPLICABLE very suitable aprotic solvents which are substantially immiscible with water are aromatic hydrocarbons and chlorinated hydrocarbons, for example benzene, toluene, o-xylene, m-xylene, p-xylene, trimethylbenzony, dichloromethane, 1,2-dichloromethane, chloroform, monochlorobenzene, and 1,2-dichlorobenzene and 1,3-dichlorobenzene. Very good results were obtained with toluene and xylene.

The process of the present invention can be carried out starting from a saturated or unsaturated solution of a water-soluble cyanide and the next stage of the process in the presence or absence of a solid water-soluble cyanide. In carrying out the process of the present invention, it has been found that the presence of solid water-soluble cyanide improves yield and reaction time for some solvents.

The use of alkanes or cycloalkanes in combination with an aqueous cyanide solution in the absence of a water-soluble solid cyanide allows the reaction time to be kept to a minimum. The use of aromatic hydrocarbons or chlorinated hydrocarbons in combination with an aqueous cyanide solution in the absence of solid water-soluble cyanide causes the reaction times to be slightly prolonged, but still is preferred in some cases because the resulting reaction mixture can be directly used for preparing pesticidal mixtures without further separating the final ester from the solvent. The use of aromatic hydrocarbons and chlorinated hydrocarbons in combination with solid water-soluble cyanide results in shorter reaction times. Solid water-soluble cyanide can of course also be used in the presence of cycloalkanes.

Appropriate reaction times may be obtained when the molar ratios of the amount of water to the total amount of water-soluble cyanide are greater than 0.05.

Another example of substantially water-immiscible aprotic solvents are dialkyl ethers and substantially water-immiscible alkanones, for example diethyl ether, diisopropyl ether and diisobutyl ketone. Mixtures of solvents, for example alkanes and aromatic hydrocarbons, in particular n-heptane containing up to 10% by weight of benzene and / or toluene, may also be used.

The group A in the abovementioned compound of the formula II is preferably a phenoxy group, since the most active form of pyrethroid pesticides is derived from this substituent.

The group R in the above compound of formula RCOHa1 is defined as an optionally substituted alkyl or cycloalkyl group. The alkyl group can contain both straight and branched chains and each contains 1 to 10 carbon atoms. In a preferred embodiment, the alkyl groups have a tertiary or quaternary carbon atom bonded to the -COHal group. Examples of such alkanoyl halides are 2-methylpropanoyl chloride, 2,2-dimethylpropanoyl chloride and 2-methylbutanioyl bromide. Very good results are obtained with 2-methylpropanoyl chloride. The alkyl group may contain a halogen-substituted phenyl group as a substituent. Very good results are obtained with 1- (4-chlorophenyl) -2-methylpropyl groups. The cycloalkyl group itself contains 3 to 6 carbon atoms and contains, as optional substituents, a group or groups selected from the group consisting of alkyl, alkenyl, haloalkenyl, each containing 1 to 6 carbon atoms. Exemplary cycloalkyl groups include cyclopropyl, cyclobutyl and cyclohexyl. Very good results are obtained with optionally substituted cyclopropanecarbonyl halides, in particular 2,2,3,3-tetramethylcyclopropanecarbonyl halides and 2- [2,2-dichlorvinyl) -3,3-dimethylcyclopropanecarbonyl halides. The latter halides may have a cis- and trans-configuration or a mixture thereof; it may also be a pure optical isomer or a mixture of optical isomers.

Hal in the compound of formula (IV) is chloro or bromo and preferably chloro.

The process according to the invention can be carried out by gradually adding the acyl halide to the mixture, preferably to a stirred mixture, of the other starting compounds.

2,2,3,3-tetramethylcyclopropyl, 2- (2,2-dichlorvinyl) -3,3-dimethylcyclopropyl or 1- (4-chlorophenyl) -2 (4-ethylpropyl)]. Alternatively, the total amount of starting compounds may be simultaneously placed in the reaction vessel, and the reaction is allowed to proceed with vigorous stirring.

The process of the present invention is particularly important at the point where 3-phenoxybenzaldehyde is used as the aromatic aldehyde and the acyl halide is 2- (4-chlorophenyl) -3-methylbutanoyl chloride, 2,2,3,3-tetamamethylcyclopropanecarbonyl chloride or 2- [2,2-11 (4-methyl) -3,3-dimethylcyclopropanecarbonyl] -acetide, since in this case they exhibit the esters thus prepared, i.e. α-ethano-3-fetenoxybenzyl-2- (4 Chlorophenyl] -3-methylbutanoate, cyanobutylphenoxybenzyl 2,2,2,3,3-tetrate methylcyclopropanecarboxylate and α-cyano-3-phenoxybenzyl-2t (2,2-dichlorvinyl) -3,3-methylmethylcyclopropanecarboxylate, in particular of significant pesticidal activity.

The following examples further illustrate the process of the present invention. All experiments were performed at 23 ° C. The reaction mixtures were vigorously stirred and analyzed by gas-liquid chromatography to determine the yield of the ester formed. The reaction mixtures were filtered to remove the precipitated sodium chloride and solid sodium cyanide, if any, and the solution was dried with anhydrous sodium sulfate. The solvent was removed in a film evaporator at 2 kPa. All yields are based on the starting aldehyde.

He did

Preparation of α-cyano-3-phenoxybenzyl 2- (4-chlorophenyl) -3,4-methyl-butanoate in the presence of n-heptane.

In a 50 ml round-bottomed flask equipped with a magnetic stirrer was charged 10 mmol of 3-phenoxybenzaldehyde, 10 mmol of 2- (4-chlorophenyl) -3-methylbutanoyl chloride, 12 mmol of sodium amide. , then water, catalyst, if used in the experiment, and 20 ml of n-heptane to the mixture thus formed was stirred. in this example, experiments were performed seven, ^BC? whereby the results of these experiments are shown · in table I.

Table I

Experiment no. Catalyst Added water (ml) _ Reaction time (h) Ester yield (%) -name amount % mole per aldehyde) 11 ' - ¹ - 1.0 3 86 18 more than 99 2 methyl tri-2-methyl-heptylammonium chloride 5 1.0 2 96 3 tetra-n-butylammonium chloride 2 1.0 5 99 4 tetra-n-butylammonium chloride 2 , 2.0 5 99 5 tetra-n-butylphosphonium bromide 2 1.0 3 99 6 n-hexadecyldimethylsulfonium iodide 2 1.0 3 97 7 1,4,7,1'0,13,16-hexaoxacyclo- 2 1.0 3 94

octadecane

1) the process was not carried out according to the present invention.

Column 1 of Table I lists the experiment number, Column 2 refers to the catalyst, Column 4 indicates the amount of water added to the starting mixture (excluding water present in sodium cyanide), and Column 5 indicates the required rupture time. The yield of the desired ester is given in column 6. Sodium cyanide was completely dissolved.

Example 2

Preparation of α-cyano-3-phenoxybenzyl 2- (2,2-diclorvinyl) -3,3-dimethylcyclopropanecarboxylate in the presence of n-heptane

In a 50 ml round-bottom flask equipped with a magnetic stirrer, 10 mmol of 3-phenoxybenzaldehyde was charged. amount of 2- (2,2-dichlorvinyl) -3,3-dimethylcyclopropanecarbonyl chloride, 12 mmol. sodium cyanide, water, catalyst, if used in the experiment, and 20 mL of n-heptane. The mixture was stirred. In this way, six experiments were performed, which are summarized in Table II. Columns 3, 4 and 5 show the amount of catalyst, water and acyl chloride that was added to the reaction mixture. The yields of the desired ester are shown in column 7.

197288

Table II

1 2 3 4 5 6 7 try Catalyst Added Acyl- Time - Yield C. name amount water chloride reaction of an ester (% mol per alde- (ml) (mmol) (h) ........ (%) hyd) if' -. - 1.0 10.2 3 49 21 94 44 99 2 methyl-tri-2-methylheptyl- 5 1.0 10.2 1 96 ammonium chloride 3 tetra-n-butylammonium-. 2 1.0 10.5 1 90 chloride 4 99 4 Amberlit IRA 400 ² ' (1 gram) 1.0 10.5 5 95 5 Dobanol 91—63 ' 2 1.0 10.0 2 80 6 1,4,7,10,13,11-hexaoxacyclo- 2 1.0 10.0 2 76

octadecane

(1) this experiment has not been conducted according to the present invention;

2) the trade designation of a strongly basic anion exchange resin which comprises a styrene / divinylbenzene copolymer as a polymer matrix and a quaternary ammonium group as an ionic active group. The chloride form was used,

3) the trade name of a nonionic surfactant prepared from a mixture of alcohols containing from 9 to 11 carbon atoms and containing an average of 6 ethyleneoxy units, the mixture of alcohols containing 85% of n-alkanols and 15% of 2-alkylalkanols.

Example 3

Preparation of α-cyano-3-phenoxybenzyl-2,2,3,3-tetramethylcyclopropanecarboxylate - in the presence of n-heptane

Two methods were used to prepare the above ester, A and B, as described below. The purpose of this example is to demonstrate that the gradual addition of acid chloride to the reaction mixture over a period of from 0.5 to 2 hours results in greatly. increased yield towards the end of the period.

Method A

According to this method, 10 mmol 3-phenoxybenzaldehyde, 10 mmol -2, - were charged into a 50 ml round-bottomed flask equipped with a magnetic stirrer.

2,3,3-tetramethylcyclopropanecarbonyl chloride, 12 mmol sodium cyanide, 1.00 mL water, catalyst if used in the experiment, and 20 mL n-heptane. The molar ratio of water to sodium cyanide was 4.64 with no solid sodium cyanide. The catalyst was added in an amount of 0.20 mmol. The mixture was stirred for 1.5 hours and then analyzed.

Method B (gradual addition of acid chloride)

According to this method, 10 mmol of 3-phenoxybenzaldehyde, 12 mmol of sodium cyanide, 10 ml of n-heptane, 1.00 ml of water and 0.20 mmol of catalyst were charged into a vessel which was the same as in Method A. The mole ratio of water to sodium cyanide was 4.64. A total of 10 mmol of 2,2,3,3-tetramethylcyclopropanecarbonyl chloride, which was dissolved in 10 mL of n-heptane, was added to the flask over a period of 70 to 75 minutes. The ester yield was determined up to the end of this interval.

Five experiments were performed using these methods. The results of these experiments are shown in Table III, which lists the catalyst used, if present, and the yields of the desired esters.

Table IIII

Experiment Catalyst ester yield (%)

No. Method A Method B

1+ none 17 40 2 1,4,7,10,13,16-hexaoxacyclooctadecane 18 97 3 tetra-n-butylammonium chloride 20 May 98 4 methyl tri-2-methylheptylammonium chloride 18 96 5 Dobanol 91-6 + 44 98

+) a procedure that was not performed according to the present invention + +) an explanation of this term is given in Table II.

The amount of catalyst used was. 2% by weight, in experiments 2-4 and 10% by weight, in experiment 5, based on 3-phenoxybenzaldehyde.

The reaction mixture obtained in Experiment 4, Method B, was filtered and the filtrate was washed twice with 20 ml of 1 M aqueous sodium bicarbonate solution and once with 20 ml of water. The washed filtrate was dried and n-heptane was removed from the dried filtrate to give the ester as an oil in pale yellow color. This oil was dissolved in 2.5 mL of methanol at 23 ° C and the resulting solution was cooled to -20 ° C to give an ester precipitate. The ester thus obtained was filtered off and its purity was greater than 98%.

Example 4

Production scale of α-cyano-3-phenoxybenzyl 2- (4-chlorophenyl) -3-methylbutanoate

The desired esters were prepared according to Method A (not performed according to the present invention), B and C for comparison.

Method A (no interfacial catalyst was used)

According to this method, 100 mmol of 3-phenoxybenzaldehyde, 100 mmol of 2- (4-chlorophenyl) -3-methylbutanoyl chloride, 120 mmol of sodium cyanide, 10 ml of water were charged into a 500 ml round-bottomed flask equipped with a paddle stirrer. (which was sufficient to dissolve all sodium cyanide) and

200 ml n-heptane. After stirring for 45 hours, the mixture was heated to a temperature in the range of 40 to 50 ° C and filtered. The filtrate was washed twice with 50 ml of 1 M aqueous sodium bicarbonate solution, once with 50 ml of water, then dried and the n-heptane was removed from the dried solution to give the desired ester in 99% yield and 96% purity.

Method B (onium compound was used)

The same procedure as described in Method A was carried out here. was. 2% by weight, tetra-n-butylammonium chloride, based on 3-phenoxybenzaldehyde. The desired ester was recovered after two hours, yield 99% and purity 94%.

Method C (non-ionic surfactant used)

The procedure described in Method A was repeated using 10 wt. "Dobauol 91-6" (the meaning of which is given in Table II) based on 3-phenoxybenzaldehyde. After stirring for three hours, the reaction mixture was warmed to a temperature in the range of 40 to 50 ° C and then filtered. Ethanol (50 ml) was added to precipitate the emulsion and washed twice with 50 ml of 1 M sodium bicarbonate solution in water, and once with 50 ml of water, dried and the filtrate dried. heptane to give the ester in 98% yield and 97% purity.

The results obtained according to the above methods are shown in Table IV below.

Table IV

Experiment no. Catalyst Designation Amount (% mol per aldehyde) Reaction time (hj Ester yield (%) Ester Purity (.%) 1 - - 45 99 96 2 tetra-n-butylammonium chloride 2 2 99 94 3 Dobanol 91—6 ¹ ) 10 3 98 97

4) an explanation of this term is given in Table II

Example 5

Preparation of α-cyano-3-phenoxybenzyl 2- (4-chlorophenyl) -3-methylbutanoate in the presence of various solvents and solid cyanide

In a 50 ml round-bottom flask equipped with a magnetic stirrer, 10 mmol of 3-phenoxybenzaldehyde, 10.0 or

10.5 mmol of 2- (4-chlorophenyl) -3-methylbutanoyl chloride, 12 mmol of sodium cyanide, 0.02 ml of water and 20 ml of aprotic solvent. The molar ratio of water to sodium cyanide was 0.15, with solid sodium cyanide present. The reaction mixture was stirred and analyzed. Thirteen experiments were carried out and the results are shown in Table V, which also shows the solvents used. Experiments 2,3,4, 8 and 9 were carried out with 10.0 mmol and further experiments with 10.5 mmol of 2- (4-chlorophenyl) -3-methylbutanoyl chloride in Experiment 3 using a 97% petroleum ether. its boiling point was at atmospheric pressure in the range of 62 to 82 [deg.] C. In experiments 3 and 4, the ester remained in solution in the reaction The reaction mixture obtained in experiment 4 was filtered and cyclohexane was filtered off. Removal of the filtrate to give the desired ester as a colorless oil in quantitative yield Table V also shows the yields of the desired ester, comparing these yields to show that alkanes and cyclohexane appear to be the best solvents.

Table 'V

Experiment no. Solvent Reaction time (h) Ester yield (%) 1 n-heptane 1.0 more than 99 2 2,4,4-trimethylpentane 1 92 2 99 3 petroleum ether 1 91 2 99 4 cyclohexane 1 80 3 more than 99 5 toluene 3 38 24 98 6 Dichloromethane 2 34 18 46 7 o-dichlorobenzene 2 59 18 72 8 diethyl ether 3 54 20 May 91 9 diisobutylketone 20 May 91 10 nitromethane 20 May 80. 5 5 11 1,4-dioxane 21 13 18 0 12 N, N-dimethylformamide 5 5 21 7 13 dlmethylsulfoxid 2 1 18 0

Example 6

Preparation of α-cyano-3-phenoxybenzyl 2- (4-chlorophenyl) -3-methylbutanoate in the presence of solid cyanide

In a 50 ml round bottom flask equipped with a magnetic stirrer was charged 10 mmol of 3-phenoxybenzaldehyde, 10.5 mmol of 2- (4-chlorophenyl-3-methylbutanoyl chloride, mmol of sodium cyanide, 20 mL of toluene, ^limit, phase catalyst and water. the mixture was stirred for various periods and then analyzed. This procedure was carried out six experiments, and the results are shown in table VI, along with those of catalysts were used, and how much water was added, if The catalysts were used in an amount of 0.20 mmol.

Table VI

2

4 5 6

Experiment no. Catalyst Added water (ml) Molar ratio of water to NaCN Reaction time (h) Yield of ester (%) 1 1,4,7,10,13,16-hexaoxacyclo- - 0.012 2 60 octadecane 20 May 91 80 97 2 1,4,7,10,13,16-hexaoxacyclo- 0.02 0.105 3 100 ALIGN! octadecane 3 1,4,7,10,13,16-hexaoxacyclo- 1.00+ 4.64 2 95 octadecane 4 98 20 May 100 ALIGN! 4 tetra-n-butylammonium- T), 012 2 30 bromide 22nd 32 5 tetra-n-butylammonium- 0.02 0.105 2 81 bromide 18 98 6 tetra-n-butylammonium- 1.00 + 4.64 2 71 bromide 22nd 81

+) For comparison purposes, 2 experiments were performed in which no solid cyanide was present. .

The sodium cyanide used was in the form of particles whose largest dimension was 0.5 mm and contained 0.44% by weight of water. The molar ratio of water to sodium cyanide was determined by taking into account the amount of water contained in sodium cyanide and the amount of water added if added in the experiment. By comparison, the molar ratio of water to sodium cyanide in a saturated aqueous sodium cyanide solution having a temperature of 23 ° C can be said to be 4.1.

Claims (6)

OBJECT OF THE INVENTION A process for the preparation of α-cyanobenzyl esters of alkanoic and cycloalkanoic acids of the general formula II CN AND I R.CO. O-CH3 or - represents a cycloalkyl group having 3 to 6 carbon atoms, optionally substituted by at least one alkyl, alkenyl or haloalkyl group having up to 6 carbon atoms each, and A represents a phenoxy, phenylthio or benzyl group, by reaction of a benzaldehyde of formula III wherein: R represents an alkyl group having 1 to 10 carbon atoms and an optionally substituted phenyl group substituted with haloA (VI) wherein A is as defined above, with an acid halide of formula IV R = COHal (IV) wherein R is as defined above and Hal represents a bromine or chlorine atom, in the presence of a water-soluble cyanide and a water-immiscible apiotic solvent, characterized in that the reaction is carried out in the presence of a quaternary onium compound of the general formula V R — X— R ¹ * Y ~ (V) where X represents a nitrogen, phosphorus or arsenic atom, R @ ¹ , R @ ² , R @ ³ and R ^{@ 4 each} represent an alkyl, aralkyl, alkaryl or aryl group; Y is a monovalent ion, or sulfonium compounds of formula VI R R — S — R ¹ У ~ where R 5, R 6 and R ⁷ are each alkyl and Y denotes a monovalent ion as an interfacial catalyst. 2. A process according to claim 1, wherein a poly (alkyleneoxy) derivative acting as a surfactant is used as the interfacial catalyst. Process according to any one of the preceding claims, characterized in that the molar ratio of the amount of the interfacial catalyst to the amount of the benzaldehyde of the general formula III ranges from 1: 5 to 1: 500. Process according to any one of the preceding claims, characterized in that the reaction is carried out at a temperature ranging from 10 to 50 ° C. Process according to any one of the preceding claims, characterized in that the solvent used is an alkane, a cycloalkane or an aromatic hydrocarbon or a chlorinated hydrocarbon. Process according to any one of the preceding claims, characterized in that the reaction is carried out in the presence of a solid water-soluble cyanide.