The invention relates to the preparation of pyrethroide derivatives in a great purity suitable for controlled crystallization. of the general formula (I),

in the course of which cyanhydrine of the general formula (ID

CN

is acylated with acid chloride of the general formula (III)

(III

aπd the cyanhydrine of the general formula (II) is prepared from benzaldehyde of the general formula (IV)

by reacting the same with alkali-cyanide and water using an amine as catalyst in a way, that in the aqueous solu¬ tion of alkali-cyanide of 7-9 mol benzaldehyde of the general formula (IV) is added in the presence of 0.15- 0.25 mol equivalents of amine calculated on the aldehyde and the cyanhydrine of the general formula (II) formed in the reaction mixture is acylated in statu nascens parallel to the formation of cyanhydrine with an acid chloride of the general formula (III) or with an acid chloride mixture added continuously, controlling the temperature balance of the reaction in a way, that the acylation should be finished between 0.2-4 hours at a temperature of 80-10°C and the cypermetriπe emulsion obtained is extracted advantageously with an apolar solvent and after distillation of the solvent the remain¬ ing oily product is advantageously isolated from a C,_,, alcohol.

In the general formulas

- A is a chlorine atom, a bromine atom or a methyl group

- Y is a hydrogen, a fluor or a chlorine atom

- the wave line means an R respectively S configura¬ tion.

The o--cyano-esters of the general formula (I) are effective insecticides (Hungarian Pat. Specification No. 170 866).

To their preparation several processes are known. This way from - in given case suitable substituted - phenoxy benzaldehyde with potassium cyanide in the presence of sulphuric acid a cyanhydrine derivative of the general formula (II) was obtained and after purifying the product by extraction it was acylated in the presence of pyridine with acid chlorides of the general formula (III) in benzene at 20°C for 18 hours, thereafter the reaction mixture was subjected to chromatographic analysis (Hungarian Pat. Specification No. 170 866, example 20; Pesticide Sci. jS (1975) 537).

Disadvantage of the process is, that because of the known inclination of cyanhydrides to decomposition special storage and reaction circumstances had to be insured to exclude the hydrogen-cyanide generation. To exclude the cyan danger the tosilate of cyanhydrine of the general formula (II) was reacted with the sodium salts of cyclopropane carboxylic acids. Disadvantage is , that - although the cyanhydrine-tosilate is more stable and an intermediate which can be isolated in a crystal¬ line form - its reactivity is weaker and the re-esterif- ication takes 5-10 hours at a temperature of about 70°C.

Thus in the course of the reaction 5-20% of decomposition products are formed, firstly due to the decomposition of the cypermetrine formed (Specification of the EU. Patent No. 67461). The cyanhydrine intermediate is excluded (elim¬ inated) too in a way, that the suitable benzaldehyde derivative was reacted first in the presence of a catalystic quantity of Lewis acid with acid chloride of the general formula (III), and from the^-chloro-ester obtained the c ^» - -cyaπo-ester was formed in a substitution reactin with sodium-cyanide reagent (French Pat. No. 1 407 200). Applying this process e.g. the cypermetrine can be obtained with a yield of about 70%, however because of the weak quality of the product it could not be applied in an industrial scale.

Applying a similar reaction chain the acid chlorides of the general formula (III) were reacted below 10°C with the melt of phenoxy-beπzaldehyde and the ^ -chloro-ester was added to alkali-cyanide and the aqueous solution of a special phase-transfer catalyst (Hungarian Pat.

Specification No. 191 333). The quality of the product is even in this case not satisfying, among others because of the catalyst-traces remaining present.

Disadvantage of the applied phase-transfer-catalysts is, that they accelarate the reaction, but they are accelaratiπg the side reactions in a similar extent, and this way they further the hydrolysis of the acid chloride of the general formula (III) and in a small extent that

of the cypermetrine too. But without these catalysts the reaction can be realised only with a yield of 64% and the quality of the product obtained is very poor too and requires chromatographic purification (US. Pat. Spec. No. 3 835 176 1). As phase-traπsfer-catalysts "onium" e.g. quaternary ammonium compounds (Hungarian Pat. Spec. No. 181 362, Japanese document laid open to public inspection No. 77 142046), tertiary amines (2 110 727 Brit. Pat. Spec), tertiary amine salts (Hungarian Pat. Spec. No. 189 096), amino-alkyl-sulphonic acids (USP No. 4 322 535 1) were applied.

Reproducing the processes mentioned above we stated, that in the reaction mixture generally three liquid phases are present, namely one aqueous and two organic phases. Accordingly the transport of the substances, the transport of the reagents respectively is slowing down the reaction and it is raising a possibility to the start of side-reactions.

According to the solvation of the present invention only two solvent phases are formed and the coincidence of the reactants is assured too in a way, that in a quick reaction a very pure product can be obtained.

Our recognition is putting the judgement of the reaction in a new light. The role of the medium was examined in details and a statement was achieved accord¬ ing to which (Hungarian Pat. Spec. No, 181 632) the apolar solvents are favourable to the running down of the reaction, while increasing the polarity the yield is

decreasing. According to the data published e.g. in the case of dichloro-methaπe the yield is only 46%, while in the case of dimethyl-sulphoxide it is 0% (during 8-10 hours) . Realizing the present invention because of the aqueous medium the reaction is taking place unanimously under polar circumstances - however - in a dramatic contrast - with an uncommon yield compared to that awaited. A substancial recognition of the present invention is to avoid problems of getting rid of different auxil¬ iaries and that how to remove the byproducts.

In the course of our examinations we examined circumstantially the individual parameters of the reaction.

We examined the scales of the use of organic solvents in the case carrying out the reaction in an aqueous medium. We verified that the organic solvent can be applied only maximum to a 0.1 molar equivalent content. Using more the detectable so called "three phase state", the yield and parallel the quality are becoming worse. It is interesting that this rule relates also to solvents considered as bad ones in the previous literat¬ ure (dichloro-ethaπe, carbon tetrachloride , dichloro- methane) and to those recommended, as aliphatic praffines (hexane, heptane, etc.).

According to the invention secondary or tertiary amines - advantageously - trietyl-amine or imidazole are

applied in a quantity of 0.15-0.25 mol-equivalents calculated on the aldehyde of the general formula (IV). The alkali-cyanide is applied expediently in a 7-9 mol% aqueous solution. It is advantageous to carry out the acylatioπ reaction at a temperature of 5-15°C in the course of 2-3 hours. Using a suitable equipment, reacting the components in a shorter time even a higher temperature is not damaging the reaction. According to the present invention not only the cis- or trans-isomers or mixtures of them of an optional ratio from the possible acid chlorides can be applied, but also the optical is ores too. in the course of the reaction no isomerization occurs. Acylating the 2,2-dimethyl-3-(2 ' ,2 '-dichloro-viπyl)- cyclopropane-carboxylic-acid chloride isomers with a mixture containing acid chlorides in a mass ratio of cis 2 - trans 3, the cipermetrine emulsion obtained is extracted with an apolar solvent and after distilling the apolar solvent the remaining oily product - is crystallized - advantageously from any alcohol C, , a crystalline cipermetrine of 98% purity, melting at 38- 40°C containing the possible isomers in a ration of about is 2:trans' 3 can be isolated. Acccirding to our knowledge up to the present cipermetrine was not prepared in such a pure, crystalline form.

As a product of such a purity is crystallizing spontaneously by recrystallizatioπ a particularly pure

(above 98%) product can be prepared.

Substantial advantage of the process is that because of using an aqueous medium a much more diluted cyanide solution can be applied, which makes the controlability of the pH value much easier.

In the case of industrial manufacture a further advantage is, that the reaction can be carried out very quickly and after the addition the reaction mixture can be worked up immediately. Our method is surpassing the known ones in respect of reliability, simplicity and reπtability and can be applied even in industrial scales.

Amongst the recognitions forming the base of the present invention the preparation and the mood of reacting on the cyanhydride takes a very important place. The suitable aldehyde is reacted in a diluted aqueous solution with cyanide, to avoid the Canizzaro-reaction in the presence of at most 0.3 moles amine (calculated on aldehyde) . The cyanhydride formed in the equilibrium reaction is reacted in statu nascens, in the aqueous medium, quickly - and accordingly at a suitable temperature - with the added acid chloride parallel to its formation. This way the equilibrium is shifted and the formation of cyanhydride is made complete - on the other hand by the immediate a cylation it is prevented that cyanhydrine should be subject in a basic-cyanic medium to side- reactions. This way the process is becoming so selective

that the side-products - among them products of the general formulas (V) and (VI) - , their formation respectively - are practically completely supressed.

Summarized it can be stated, that according to the invention the amine catalyst is selective, that is it catalyses only the main reaction, while the ionic phase- -transfer catalysts are not selective: but decreasing the surface tension they are catalysing in the same degree the undesirable e.g. hydrolytic side processes, as the main reaction. The process according to the invention thus differs from the simple phase-transfer-catalysis. The symptoms are: a) A very quick reaction, b) A very pure product (a 97% purity, usual in the laboratory) and this way: c) Cipermetrine is crystallized with a nearly quantitative yield (91%) even in case of 8 isomers - while a crystalline product was not known up to the present. d) The reaction can be carried out practically without a solvent, with polar solvents respectively which was considered as impossible previously. This accentuates the surprising character of the invention. The process according to the invention is detailed in the following examples. The products were determined by gaschromatographic and fluidchromatographic methods of high pressure. (Analytical Methods for Pesticides and

Plaπt Growth Regulators XIII. Ed. by: Guπter Zweig and Joseph Sherma, Academic Press 1984). As analytical data the results are published always in mass%. Exapmle 1 (R,S) g^-cyano-3-phenoxybenzyl-(lR,5)-cis-trans-3- (2 ' ,2 '-dichloro-vinyl)2,2-dimethyl-cyclopropane- carboxylate

To 210.10 1 of water and 51.1 kg of sodium-cyanide weighed in a 3000 1 duplicator 27.4 1 of triethylamine are let to flow. To the mixture 198.2 kg of m-phenoxy- benzaldehyde are added and while stirring and cooling in 2 hours continuously 238.9 kg of 2,2-dimethyl-3-(2 ' ,2 ' - .dichloro-vinyl)-cyclopropaπe-carboxylic-acid chloride (cis-trans isomer ration 42:58) are added. After the reaction the mixture is post reacted at room temperature for 1 hour, whereafter the mixture is extracted with a mixture of 200 1 water and of 800 1 1 ,2-dichloro-ethane . The solution is evaporated and thus 414.2 kg of a pale yellow viscous oil.are obtained. Yield related to the m- phenoxy-benzaldehyde active ingredient content 99,5%.

According to gaschromatographic determination the active ingredient content of the product is 97%.

400 kg of the oil thus obtained is dissolved in 720 1 of methyl alcohol and after filtration and inoculation the solution is cooled and crystallized. The product is filtered and dried at room temperature. 372 kg of snow white crytals are obtained. Yield related to the weighed oil is 93%.

Analysis : lRcis R and IScis S 23 .5

(HPLC) lRcis S and IScis R 18 .1

IRtrans R and IS trans S 34 . 3 total 99.0% impurities 1.0%

Melting point: 42-46%

^C 22 ^H 19 ^C1 2 ^N0 3

Calculated: C: 63.47% H: 4.60% N: 3.36%

Found: C: 64.20% H: 4.80% N: 3.21% Example 2

(R,S) o -cyano-3-phenoxybenzyl-(lR,S-trans-3-)

(2' ,2 ' -dichloro-vinyl 2 ,2-dimethyl-cyclopropane- carboxylate

In a fourπecked spherical flask provided with a thermometer and dropping funnel 210 ml of water are weighed and 51.5 g of sodium-cyanide, after total solution 27.4 ml of triethylamine and 198.2 g of m- phenoxy-benzaldehyde are added. While stirring and cooling in the course of 2 hours 238.9 g (-)-trans-3- (2' ,2 '-dichloro-vinyl)-2,2-dimethyl-cyclopropane- carboxylic-acid chloride are added.

The mixture is stirred for further 30 minutes at room temperature whereafter it is heated with 560 ml of n-heptane to 60°C and extracted. After distillation of the solvent 411.3 g of a yellow oil are obtained. Yield

98.8%. Active ingredient content 97.2%.

Example 3

(R , 5) p -cyano-3-phenoxybenzyl- (lR , 5 cis ) -3-

(2',2'-dichioro-vinyl)2,2-dimethyl-cyclopropane- carboxylate

One proceed according to example 2 with the differ¬ ence, that instead of triethylamine 6.8 g of imidazole and instead of trans acid chloride (—) cis acid chloride are applied. The process of working up, as the product is a crystalline one, differs ^' from that described. The precipitated crystals are filtered, washed with water and isopropaπol and dried. 413.4 g of a white crystalline product are obtained. Yield: 97.8%. Active ingredient content: 98.8%. Melting point: 54°C. Example 4

(R,S) c*N-cyano-3-phenoxybenzyl-(lR ,5 cis)-3- (2',2'-dibromo-vinyl)2,2-dimethyl-cyclopropane- carboxylate

One proceeds according to example 2 with the difference, that instead of 238.9 kg of trans acid chloride 332.1 kg of (—) cis-3-(2 ' ,2 ' -dibromo-viπyl (2, 2-dimethyl-cyclopropaπe-carboxylic-acid chloride are added to the reaction mixture. As a result 489.9 g of a yellow oil are obtained. Yield: 97.0%. Active ingredient content: 97.2%.

^C 22 ^H 19 ^Br 2 ^N0 3 ^{Mw* 505} - ²²

Calculated: C: 52.53% H: 3.79% N: 2.77%

Found: C: 51.8% H: 3.90% N: 2.75%

Example 5

(R,S) t-<-cyano-3-phenoxybenzyl-(lR,S trans)-3-(2- methyl-l-propenyl)-2,2-dimethyl-cyclopropane-

carboxylate

One proceeds according to example 2 with the difference that instead of 238.9 g of trans-permetrinic- acid chloride 195.8 g of (-)-trans-3-(2-methyl-l- propenyl)-2,2-dimethyl-cyclopropane-carboxylic-acid chloride are added drop by drop to the reaction mixture. As a reasult 360.3 g of a yellow oil is obtained. Yield related to 3-phenoxy-benzaldehyde 96.0%. Active ingredient of the oil obtained: 96.8%.

^C 24 ^H 25 ^N0 3 ^Mw ' ^375*471

Calculated: C: 76.77% H: 6.71% N: 3.73%

Found: C: 77.0% H: 6.20% N: 3.70%

Example 6

(R,S) (*!-cyano-3-phenoxybenzyl-(lR,5 cis)-3-(2' , 2 ' - dichloro-vinyl)-2,2-dimethyl-cyclopropane- carboxylate

One proceeds according to example 2 with the difference, that instead of traπs-permetriπic-acid chloride (+)-cis-3-(2 ' ,2 '-dichloro-vinyl)-2 ,2-dirnethyl- cyclopropane-carboxylic-acid chloride is added dropwise to the reaction mixture. As a result 410 g of a yellow oil are obtained. Yield related to 3-phenoxy-beπzaldehyde 98.7%. Active ingredient of the oil obtained: 98.0%. C ₂₂ H ₁₉ C1 ₂ N0 ₃ Mw. 416.307

Calculated: C: 63.47% H: 4.60% N: 3.36% Found: C: 63.90%, H: 4.65% N: 3.30%