IE44059B1

IE44059B1 - Preparation of pesticidal benzyl esters

Info

Publication number: IE44059B1
Application number: IE426/77A
Authority: IE
Original assignee: Shell Int Research
Priority date: 1976-03-01
Filing date: 1977-02-28
Publication date: 1981-07-29
Also published as: DE2708590C2; PT66242B; SE442633B; FR2342960B1; YU53477A; HU181632B; IL51567A; IE44059L; JPS52105148A; FI65989B; SU685145A3; NO145234B; DK87977A; ATA132777A; SE7702168L; PH13719A; NL7702022A; IN143789B; YU40667B; AR227121A1

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.

Description

This invention relates to a process for the preparation of certain inseeticidally-active esters of the so-called synthetic pyrethroid type.

It is known, according to D.A.S. 2,231,312, that some synthetic pyrethroids may be prepared hy the reaction of a substituted cyclopropanecarbonyl halide with a 3-substituted benzaldehyde in the presence of aqueous sodium or potassium cyanide. Such a process yields pyrethroids of the following type :- The Applicant has found that the esters of the type depicted in formula I as well as other esters falling within the synthetic pyrethroid field may be prepared more efficiently and with higher yields by the use of a particular catalyst.

Accordingly, the present invention provides a process for the preparation of an ester of general formula:A wherein R is an optionally-substituted alkyl or cycloalkyl group and A is phenoxy, phenylthio or benzyl, which comprises reacting - 3 44059 a benzaldehyde of the formula: A OCH III with an acyl halide of the formula R.CO.Hal (wherein Hal is bromine or chlorine) in the presence of water, a watersoluble cyanide, a substantially water-immiscible aprotic solvent and a phase transfer catalyst.

The phase transfer catalyst may be any reagent which is capable of accelerating interphase reactions in aqueous/ organic two-phase systems.

The phase transfer catalyst may be an onium compound, particularly a quaternary onium compound of the general formula Y" R1 R2-X-Ri| r R3 wherein X represents a nitrogen, phosphorus or arsenic atom, 3 4 R , R , R and R each an alkyl, aralkyl, alkaryl or aryl group and Y a monovalent ion, e.g. a halide such as chloride, bromide or iodide, or an alkylsulphate such as methylsulphate or ethylsulphate or a sulphonium compound of the general formula R6 R5-S-R7 6 7 wherein R , R and R' each represent an alkyl group and Y a monovalent ion, e.g. a halide such as chloride, bromide 40 59 - 4 or iodide, or an alkylsulphate such as methylsulphate or ethylsulphate. Preferahly the alkyl groups contain 1 to 18 carbon atoms and the aralkyl and alkaryl groups contain up to 10 carbon atoms; the aryl group is preferably phenyl.

Examples of suitable onium compounds are tetra-nbutylammonium bromide, tetra-n-butylammonium chloride, methyltri-2-methylphenyl-arnmonium chloride, tetramethylphosphonium iodide, tetra-n-butylphosphonium bromide, methyltriphenylarsonium iodide, ethyl-2-methylpentadecyl2-methylundecylsulphonium ethylsulphate, methyldinonylsulphonium methylsulphate and n-hexadecyldimethylsulphonium iodide. Very good results have been obtained with quaternary ammonium compounds.

The onium compound may be a hydroxide or a salt and can be employed as the functional portion of a stronglybasic anion exchange resin having a structural portion (polymer matrix) and a functional portion (ion-active group).

Of special importance are polystyrene resins, such as copolymers of aromatic monovinyl compounds and aromatic polyvinyl compounds particularly styrene/divinylbenzene copolymers. The functional portion is a quaternary ammonium, phosphonium or arsonium group. Examples of strongly-basic anion exchange resins which may be employed are those derived from trimethylamine (such as the products known under the trade names of Amberlite IRA-kOO, Amberlite IRA-kOl, Amberlite IRA-k02, Amberlite IRA-900, Duolite A-101-D, Duolite ES-lll, Dowex 1, Dowex 11, Dowex 21K and Ionac A-405)(Amberlite, Duolite andDowex are registered Trade Marks), and those derived from dimethylethanolamine (such as the products known under the trade names of Amberlite IRA-410, Amberlite IRA-911, Dowex 2, Duolite A-1O2-D, Ionac A-542 and Ionac A-550). - 5 Very good results have been obtained with those derived from tr:methylamine.

Other suitable phase transfer catalysts are macrocyclic polyethers known as crown ethers. These compounds, together with their preparation, are described in the literature, for example in Tetrahedron Letters No. 18(1972) pp. 1793-1796, and are commonly designated by reference to the total number of atoms forming the macrocyclic ring together with the number of oxygen atoms in that ring. Thus the macrocyclic polyether whose formal chemical name is 1,4,7,10,13,16-hexaoxacyclooctadecane is designated as l8-crown-6. Other examples of suitable macrocyclic polyethers are 3,4-benzo-l,6,9,12,15,l8,21heptaoxacyclotrieos-3ene and 3,4-benzo-l,6,9,12,-tetraoxacyclotetradec-3-ene. l8-Crown-6 is particularly suitable.

Other suitable phase transfer catalysts are surfaceactive agents. A surface-active agent is defined as in Kirk-Othmer, Encyclopedia of Chemical Technology, second edition, volume 19(1969), page 508: An organic compound that encompasses in the same molecule two dissimilar structural groups, one being water-soluble and one being water-insoluble.

The surface-active agent is preferably non-ionic, such as a poly(alkyleneoxy) derivative af a higher alcohol, alkylphenol or fatty acid formed by reacting a higher alcobol^alkylphenol or fatty acid with ethylene oxide or propylene oxide. Suitable alcohols, alkylphenols or fatty acids contain an alky£. group of 8-20 carbon atoms and the number of alkyleneoxy units is in the range of 2-50. A particularly suitable non-ionic surface-active agent (referred to in the examples as Dobanol 91-6) is formed from a n-alkanol mixture and contains an average of six ethyleneoxy units. The non-ionic surface-active agent may be an alkylbenzene containing a straight alkyl group. Suitable alkylbenzenes contain an alkyl group of 8-20 carbon atoms.

The molar ratio of the amount of phase transfer catalyst to the amount of benzaldehyde of the general formula III may vary within wide limits, but is suitably from 1:5 to 1:500. The use of low molar ratios will require a longer time to complete the reaction, whilst the use of higher molar ratios naturally increases the cost to produce a given quantity of ester. Thus, the choice of reaction time and molar ratio catalyst to benzaldehyde are mutually interdependent, and in any individual instance will depend on the local economic factors. Very good results are usually obtained at molar ratios from 1:10 to 1:100.

Another advantage of the process according to the present 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 in excess thereof. This molar ratio is preferably in the range of 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 suitably from - 7 44089 1.5:1 to 1.0:1,0 and preferably from 1.3:1 to 1.02:1.00.

By water-soluble cyanide is meant a water-soluble salt of hydrogen cyanide. Of the water-soluble cyanides alkalimetal cyanides and alkaline-earth-metal cyanides are preferred. Sodium cyanide is particularly preferred, because it affords the esters of the general formula II in the shortest reaction time.

The temperature at which the process is conducted is suitably above 0°C and is preferably in the range 10°C to 50°C. Very good results have been obtained at temperatures in the range 15°C to 40°C, The process has the advantage that ambient temperatures are very suitable.

Examples of suitable substantially water-immiscible aprotic solvents are alkanes or cycloalkanes or a mixture thereof} particular examples being n-hexane, n-heptane, noctane, n-nonane, n-decane and their isomers (for example 2-methylpentane, 3-methylpentane, 2-methylhexane, 3-methylhexane and 2,4,4-trimethylpentane) and cyclohexane and methylcyclohexane. Gasolines rich in alkanes are also very suitable, for example with a boiling range at atmospheric pressure between 40 and 65°C, 60 and 80°C or 80 and 110°C. Very good results have been obtained with nyheptane and cyclo hexane.

Other very suitable substantially water-immiscible aprotic solvents are aromatic hydrocarbons and chlorinated hydrocarbons, for example benzene, toluene, ο-, m- and - 8 £-xylene, the trimethylbenzenes, dichloromethane, 1,2-dichloromethane, chloroform, monochlorobenzene and 1,2and 1,3-dichlorobenzene. Very good results have been obtained with toluene and xylene.

The process according to the present invention may be conducted starting from unsaturated or saturated aqueous solutions of water-soluble cyanide and, in the latter case xn the presence or absence of solid water-soluble cyanide. With some solvents it has been found that the presence of solid water-soluble cyanide improves the yield and reaction time.

The use of alkanes or cycloalkanes in combination with aqueous solutions of cyanide in the absence of solid water-soluble cyanide enables the reaction time to be kept to a mihimum. The use of aromatic hydrocarbons or chlorinated hydrocarbons in combination with aqueous solutions of cyanide in the absence of solid water-soluble cyanide produces slightly longer reaction times but nevertheless is sometimes preferred because the resulting reaction mixture can be used directly for pesticidal formulations without further separation of the ester.from the solvent. The use of aromatic hydrocarbons and chlorinated hydrocarbons in combination with solid water-soluble cyanide produces short reaction times. Solid .water-soluble 44050 - 9 cyanide may however also be used in the presence of (cyclo)alkanes.

Useful reaction times can be obtained when molar ratios of the amount of water to the total amount of water-soluble cyanide is higher than 0.05.

Other examples of substantially water-immiscible aprotic solvents are dialkyl ethers and substantially water-immiscible alkanones, for example difethyl ether, diisopropyl ether and diisobutyl ketone. Mixtures of solvents, for example of alkanes and aromatic hydrocarbons may be employed for example of n-heptane containing up to 10? by weight of benzene and/or toluene.

The group A in the general formula II is preferably phenoxy because this substituent gives rise to the most active form of the pyrethroid pesticides.

The group R in the general formula RC(0)Hal is defined as an optionally-substituted alkyl or cycloalkyl group. The alkyl group may be straight or branched and preferably contains up to 10 carbon atoms. The alkyl groups preferably have a tertiary or quaternary carbon atom bound to the group -C(O)Hal Examples of such alkanoyl halides are 2-methylpropanoyl chloride, 2,2-dimethylpropanoyl chloride and 2-methylbutanoyl bromide. Very good results have been obtained with 2-methylpropanoyl chloride. The alkyl group may carry as substituents, for example, hydrocarbyloxy or substituted phenyl groups, e.g. a halophenyl group. Very good results have been obtained with l-(4-chlorophenyl)-2-methylpropyl groups. The cycloalkyi group itself preferably contains 3 to 6 carbon atoms and has as optional substituents a group or groups selected from alkyl, alkenyl and haloalkenyl each of which suitably contains up to 8 carbon atoms. Examples of cycloalkyl groups are cyclopropyl, cyclobutyl and cyclohexyl groups. Very good results have been obtained with optionally substituted cyclopropanecarbonyl halides, particularly with 2,2,3s3-tetramethylcyclopropanecarbonyl halides and 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropanecarbonyl halides. The latter halides may have a cis or trans structure or may he a mixture of such structures and may be a pure optical isomer or a mixture of optical isomers.

The substituent Hal in the general formula RC(0)Hal is preferably a chlorine atom.

The process according to the invention may be carried out by gradual addition of the acyl halide to a mixture, preferably a stirred mixture, of the other starting compounds (particularly advantageous when R in the general formula RC(0)Hal represents a 2,2,3,3-tetramethylcyclopropyl.group a 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropyl group, or a l-(4-ehlorophenyl)-2-methylpropyl group. Alternatively the total amounts of the starting materials may be placed together and the reaction allowed to take place with 440 59 vigorous stirring of the reaction mixture.

The process is of particular interest when the aromatic aldehyde is 3-phenoxybenzaldehyde and the acyl halide is 2-(4-chlorophenyl)-3~methylbutanoyl chloride, 2,2,3,3-tetra5 methylcyclopropanecarbonyl chloride or 2-(2,2-dichlorovinyl )-3,3-dinethylcyclopropanecarbonyl chloride, because the esters then formed, a-cyano-3-phenoxybenzyl 2-(4-chlorophenyl)-3-methylbutanoate, a-cyano-3-phenoxybenzyl 2,2,3,3" tetramethylcycloprbpanecarboxylate and a-cyano-3-phenoxy10 benzyl 2-(2,2-dichlorovihyl)-3,3-dimethylcyclopropanecarboxylate, respectively, are especially active pesticidal compounds.

The Examples further illustrate the invention. All experiments were conducted at a temperature of 23°C. The reaction mixtures were stirred vigorously and analysed by gas-liquid chromatography to determine the yield of the ester formed. Reaction mixtures were filtered to remove pre cipitated sodium chloride and solid sodium cyanide, if any, and drying of solutions was carried out over anhydrous sodium sulphate. Plashing of the solvent took place in a film evaporator at a pressure of 15 mm Hg. All yields are calcu-: lated on starting aromatic aldehyde* EXAMPLE I Preparation_of_a;;cyano2;5-Ehenoxybenzyl_2;;£4;;ehloro|3henyl2;;2z_ S£^!32i6utanoate_in_the_2resence_of_n;he2tane 440 59 A 50 ml round-bottomed flask equipped with a magnetic stirrer was charged with 10 mmol of 3-phenoxybenzaldehyde, mmol of 2-(4-chlorophenyl)-3-methylbutanoyl chloride, 12 mmol of sodium cyanide, water, a catalyst, if any, and 20 ml of n-heptane and the mixture thus formed was stirred. Seven experiments were carried Out in this manner, see Table I. 1 2 Table I 3 4 5 6 Exp, Catalyst Water Reaction time, Yield of ester, no. tsame amount added h %mol on ml aldehyde I1) - - 1.0 3 86 more than 99 2 methyl-tri-2- 5 methyl-heptylammonium chloride 1.0 2 96 3 tetra-n-butylammo- 2 niumchToride 1.0 5 99 4 ditto 2 2.0 5 99 5 tetra-n-butyl- 2 phosphonium bromide 1.0 3 99 6 n-hexadecyldimethyl 2 sulptonium iodide 1.0 3 97 7 1,4,7,10,13,16- 2 hexaoxacyclooctadecane 1.0 3 94 1) not according to the invention.

Column 1 in Table I states the number of the experiment, column 2 the catalyst, column 4 the amount of water added to the starting mixture (excluding the water present in the sodium cyanide) and column 5 the reaction time. The yield of the - 13 44059 desired ester is presented in column 6. The sodium cyanide was completely dissolved.

EXAMPLE II Pre2aratic>n_of_a;cyano;2zEheS222SSD22i_^zl2j2xSi£5i2E23 5 yiSiilz2i2z2i5?S£22i£££l2EE2ESDS£SE22i5!iS2S_i2_£i?2-EE2§§2£2 2£_SzE2ESSS2 A 50 ml round-bottomed flask equipped with a magnetic stirrer was charged with 10 mmol of 3-phenoxybenzaldehyde, an amount of 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropanecar bonyl chloride, 12 mmol of sodium cyanide, water, a catalyst, if any and 20 ml of n-heptane. The mixture thus formed was stirred. Six experiments were carried out in this manner, see Table II. Column 3,4 and 5 state the amounts of catalyst, water and acyl chloride added. The yield of the desired ester is presented in column 7. - 14 Table XI 2 3 4 5 6 7 Exp no. Catalyst Water Acyl Reaction Yield of , time, h ester, % name amount %mol oi aldehyc ie mmol I15 - 1.0 10.2 3 49 21 94 44 99 2 methyl-tri-2r- 5 methyIheptylammonium chloride 1.0 10.2 1 96 3 tetba-n-butyl- 2 1.0 10.5 1 90 ammonium chloride 4 99 4 Amberlite IRA '· (1 gram)1.0 10.5 5 95 4002) 5 Dobanol 91-6^ 2 1.0 10.0 2 80 6 1,4,7,10,13,16- 2 hexaoxacycloocta- 1.0 10.0 2 76 decane 1) not according to the Invention 2) a trade mark for a strongly basic anion exchange resin having a styrene/divinylbenzene copolymer as polymer matrix and a quaternary ammonium group as ion-active group.

The chloride form was used. 3) a trade mark for a non-ionic surface-active agent formed from a Cgalcohol mixture and containing an average of 6 ethyleneoxy units; the alcohol mixture consists of 85% n-alkanols and 15% 2-alkylalkanols. 4059 EXAMPLE III Preparation_of_a;cyano;3;Ehengxybenzyl_2J2i^Aj;tetramethyl; SYEl2EE2ESS££SEE°2yI&££_iQ_ibS_ErSsence_of_n2hegtane.

Methods A and B as indicated below were employed to prepare this ester. This example demonstrates that a gradual addition of the acid chloride to the reaction mixture during a period of 0.5 to 2 hours produces marked increases in yield at the end of that period.

Method A A 50 ml round-bottomed flask equipped with a magnetic stirrer was charged with 10 mmol of 3-phenoxybenzaldehyde, mmol of 2,2,3,3-tetramethylcyclopropanecarbonyl chloride, 12 mmol of sodium cyanide, 1.00 ml of water, a catalyst, if any, and 20 ml of n-heptane. The molar ratio of water to NaCN was 4.64, solid NaCN being absent. The catalyst was added in an amount of 0.20 mmol. The mixture thus formed was stirred for 1.5 hours and analysed.

Method B (gradual addition of acid chloride) The flask used for method A was charged with 10 mmol of 3-phenoxybenzaldehyde, 12 mmol of sodium cyanide, ml of n-heptane, 1.00 ml of water and 0.20 mmol of a catalyst, if any, the molar ratio of water to NaCN being 4.64. An amount of 10 mmol of 2,2,3,3-tetramethyleyclopropanecarbonyl chloride dissolved in 10 ml of n-heptane Was introduced into the flask during a period of 70-75 min.

The yield of the ester was determined at the end of this period. - 16 Five experiments were carried out in this manner.

Table III states the catalysts used, if any. This Table also presents the yield of the desired ester.

Table III Exp. no. Catalyst Yield of Method A ester, ? Method B 1‘) none 17 40 2 1,4,7,10,13,16-hexaoxacyclooctadecane 18 97 3 tetra-n-butylammonium chloride 20 98 4 methyl-tri-2-methylheptylammonium chloride 18 96 5 Dobanol 91-6 ' 44 9 8 *) not according to the invention **) for explanation of this word, see Table II.

The amounts of the catalysts used were 2%m in the experiments 2-4 and 10 ?m in experiment 5, calculated on 3-phenoxybenzaldehyde.

The reaction mixture obtained in experiment 4, method 1 B, was filtered and the filtrate washed twice with 20 nl of a 1 M aqueous solution of sodium bicarbonate and once with 20 ml of water. The washed filtrate was dried and the n-heptane was flashed from the dried filtrate to obtain the ester as a pale yellow oil. This oil was dissolved in 2.5 ml of methanol at 23°C and the solution obtained was cooled to a temperature of -20°C to give a precipitate of the ester. The ester was filtered and had a purity of more than 98?.

EXAMPLE IV £E£ES£5£i22_2£_Sl£Z2-D°l2;;]3henoxybenzyl_2-.(4-chloroEheny I);]!;; 'SSEEliiEliE2S2S£2_2D_SU_2i}i&£E22_§£&i2 Methods A (not according to the invention), B and C were compared for the preparation of the desired ester.

Method_AA in the absence of a phase transfer catalyst.

A 500 ml round-bottomed flask equipped with a paddle 10 stirrer was charged with 100 mmol of 3-phenoxybenzaldehyde, 100 mmol of 2-(4-ehlorophenyl)-3-methylbutanoyl chloride, 120 mmol of sodium cyanide, 10 ml of water (which dissolved all sodium cyanide) and 200 ml of n-heptane. After stirring for 45 hours the mixture was warmed to a temperature between 40 and 50°C and filtered. The filtrate was washed twice with 50 ml of a M aqueous sodium bicarbonate solution, once with 5θ ml of water, dried and the n-heptane was flashed from the dried solution to give the desired ester in a yield of 99? and a purity of 96?. Method_B, in the presence of an onium compound..

The experiment described in section A of this example was repeated in the presence of 2 ?m of tetra-n-butylammonium chloride, calculated on 3-phenoxybenzaldehyde. After two hours the ester was obtained in a yield of 99? with a purity of 94?.

Method_C, in the presence of a non-ionic surface-active agent.

The experiment described in section A of this Example was repeated in the presence of 10 ?m of Bobanol 91-6 ( for meaning 4 0 5 9 - 18 of this word, see Table II), calculated on 3-phenoxybenzaldehyde. After three hours’ stirring the reaction mixture was warmed to a temperature between 40 and 50°C and filtered. An amount of 50 ml of ethanol was added (to break the emulsion formed) to the filtrate and the filtrate was washed twice with 50 ml of a 1 M aqueous solution of sodium bicarbonate, once with 50 ml of water, dried and the n-heptane was flashed from the dried solution to give the ester in a yield of 98% and a purity of 97%.

The above results are summarised in the following Table IV.

Table IV Exp. ___________Catalyst________ Reaction yield of Purity of no. name amount, %njol on aldehyde time, h ester, % ester, 1 none 45 99 96 2 tetra-n-butylammo- 2 pium cfiloride. Dobanol 91-61' 10 2 99 94 3 3 98 97 1) for explanation of this word, see Table II.

EXAMPLE V E££ESES£i2D_2£_iil£2S£2::2-Ehenox2benzyl_2-£4-chloro2henj;l};; 2Σ2?2Εδϊ1ίΰΕ§Ε2δ£2_ϊϊ?_έΙ)2_2Ε£2§022_2£_22ϋ5_2Υ3Πί32 A 50 ml round-bottomed flask equipped with a magnetic 5 stirrer was charged with 10 mmol of 3-phenoxybenzaldehyde, 10.5 mmol of 2-(4-ehlorophenyl)-3-methylbutanoyl chloride, 12 mmol of sodium cyanide, 20 ml of toluene, a phase transfer catalyst, and water. The mixture thus formed was stirred for varying periods of time and subsequently analysed. Six experiments were conducted in this manner, and the results are shown in Table V, stating which catalysts and how much water was added, if any. The catalysts were employed in an amount of 0.20 mmol.

Table V 1 2 3 4 5 6 Exp. Catalyst Water Molar ratio Reaction Yield 15 no. added water to time, h ester ml NaCN 1 1,4,7,10,13,16-he- 0.012 2 60 xaoxacyclooctadecane 20 91 80 97 2 ditto 0.02 0.105 3 100 20 3 ditto 1.00* 4.64 2: 95 4 98 20 100 4 tetra-n-butylammonium 0.012 2 30 bromide 22 32 5 ditto 0.02 0.105 2 81 25 18 98 6 ditto 1.00* 4.64 2 71 22 81 For the sake of comparison these 2 experiments had no solid cyanide present. - 20 44069 The sodium cyanide used consisted of particles having a largest dimension of 0.5 mm and contained 0.44?! by weight of water. The molar ratio of water to sodium cyanide has been calculated taking into account the water present in the sodium cyanide and the water added, if any. For comparison it may be stated th8.t the molar ratio of water to sodium cyanide in a saturated aqueous solution of sodium cyanide having a temperature of 23°C is 4.1.

Claims

1. Process for the preparation of an ester of the general formula :10 A II wherein R is an optionally substituted alkyl or cycloalkyl group and A is phenoxy, phenylthio or benzyl , which comprises reacting a benzaldehyde of the formula:OCH III with an acyl halide of the formula R.CO.Hal (wherein Hal is bromine or chlorine) in .the presence of water, a water-soluble cyanide, a substantially water-immiscible aprotic solvent and a phase transfer catalyst,

2. Process as claimed in claim 1, in which the phase transfer catalyst is an onium compound, a macrocyclic polyether, or a surface-active agent.

3. Process as claimed in claim 2, in which the onium compound is a quaternary onium compound of the general formula R 1 r 2 -x-r 2 * I Ri - 22 wherein X represents a nitrogen, phosphorus or arsenic 12 3 4 atom, R , R , Ir and R each an alkyl, aralkyl, alkaryl or aryl group and Y a monovalent ion, or a sulphonium compound of the general formula Γ r 6 Π + I _r 5 -s-r 7 y 5 6 7 wherein R , R and R’ each represents an alkyl group and Y a· monovalent ion.

4. Process aq claimed in claim 2 or 3 wherein the phase transfer catalyst is a quaternary ammonium compound.

5. Process as claimed in claim 2, in which the surfaced-active agent is a poly (alkyleneoxy)-derivative of a higher alcohol, alkylphenol or fatty acid.

6. Process as claimed in claim 5, in which the poly(alkyleneoxy)derivative is formed by reacting an alkanol of 8-20 carbon atoms with ethylene oxide or propylene oxide.

7. Process as claimed in any one of the preceding claims, in which the molar ratio of the amount of phase transfer catalyst to the amount of benzaldehyde of the general formula III is from 1:5 to 1:500.

8. Process as claimed in any one of the preceding claims, which is conducted at a temperature in the range of from 10°C to 50°C.

9. Process as claimed in any one of the preceding claims, in which the substantially water-immiscible aprotic - solvent is an alkane or cycloalkane or a mixture thereof, or an aromatic or chlorinated hydrocarbon. 4405a

10. Process as claimed in claim 9, in which the alkane is n-heptane.

11. Process as claimed in claim 9, in which the aromatic hydrocarbon is toluene or xylene. 5

12. Process as claimed in any one of the preceding claims, which is conducted in the presence of solid water-soluble cyanide.

13. Process as claimed in any one of the preceding claims, in which the starting molar ratio of the amount of water tc the total amount of water-soluble cyanide is higher than 0.05. 10 i4. Process as claimed in any one of the preceding claims, in which the molar ratio of the amount of acyl halide of the general formula RC(O)Hal to the amount of the benzaldehyde of the general formula III is in the range of from 1.1:1.0 to 1.0:1.0.

14. 15 15. Process as claimed in claim 14, in which the molar ratio of the amount of acyl halide of the general formula RC(O)Hal to the amount of benzaldehyde is 1:1 or slightly in excess thereof.

15. 16. Process as claimed in any one of the preceding claims, 20 in which the water-soluble cyanide is sodium cyanide.

16. 17. Process as claimed in any one of the preceding claims, in which A in the general formula II and III is a. ohenoxy group,

17. 18. Process as claimed in any one of the preceding claims, in which Hal in the general formula RC(O)Hal represents a chlorine 25 atom.

18. 19. Process as claimed in any one of the preceding claims, 24 44059 in which the group R in the general formula II and in RC(O)Hal is a 1-(4-chlorophenyl)2-2methylpropyl group, a 2,2,3,3-tetramethylcyclopropyl group, or a 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropyl group.

19. 20. Process as claimed in any one of the preceding claims, which is carried out by placing together the total amounts of the benzaldehydej the acyl halide, the water, the watersoluble cyanide, the substantially water-immiscible aprotic solvent and the phase transfer catalyst, and stirring the mixture thus formed.

20. 21. Process as claimed in any one of claims 1 to 19, which is carried out by gradual addition of the acyl halide to a stirred mixture obtained by placing together the benzaldehyde, the water, the water-soluble cyanide, the substantially waterimmiscible aprotic solvent and the phase transfer catalyst.

21.

22. Process as claimed in claim 1, substantially as hereinbefore described and with reference to any one of the Examples.

23. Esters of the general formula II when prepared by a process as claimed in any one of the preceding claims.