Chrysanthemum Ester, Halogenated Cyclopropane Stereoisomers

Pyretbroids are bionical pesticide, which have being developed from the basis of study on the chemical structure of natural pyretbrins, They are of?high activity, broad killing, low residue and so on. Pyretbroids have 2 to 8 optical isomers, whose biological activities are closely related to molecular structure. So the study of optical isomers of pyrethroids is very important in industry production and science. Dicbloro-chrysanthemic acid is a key intermediate to prepare permethrin and cypermethrin, it has four stereoisomers. A lot of methods which have been known to prepare cis dichloro-chrysanthemic acid, however, provide less satisfactory results from an industrial point of view concerning yield and cost. This paper describes an industrially acceptable method for the synthesis of cis dichloro-chrysanthemic acid according to sources of materials in our country and conditions in our lab. 3,3-dimethyl-4,6,6,6-tetrachlorohexanoate was obtained in 92.64% by addition of carbon tetrachloride to ehtyl 3,3-dimethyl-4-pentenoate. Then the compound cylized stereoselectively to give 79% ethylcis-2,2-dimethyl-3 -(2,2,2-trichloroethyl)cyclopropanecarboxylate(cis/trans=8.8/ I .2),which hydroly- sised to yield 93% cis dichloro-chrysanthemic acid, whose melt point is 88?9 .c. R(-)-2-(4-chlorophenyl) isobutyl acid which was the by 梡roduct in preparing esfenvalerate in NAU menuofactory, used for the resolution of synthetic (? a -phenylethylamine, R(+) or S(-) a -phenylethylamine was then selected for the resolution of (? cis dichloro-chrysanthemic acid by fractional crystallisation from aqueous alcohol. (+) cis acid has 95 .37% optical purity. This method has not been reported so far at homeland. (+) cis-DV acid was synthesized to (1R,cis) permethrin and (1R,3R) a S-cypermethrin, yield 91% and 91.5% respectively. At present ,single optical isomer of (1R,cis) permethrin and (IR,3R) a S-cypermetbrin has not been put on in market both at home and abroad country market Biological testing shows that toxicity of (IR,cis)perinethrin is 3 to 4 times than ordinary permethrin and the toxicity of(1R,3R) a S cypermethrin is Ii times than ordinary cypermethrin.