METHOD FOR PRODUCING MIXTURES OF CYOPERMETHRINE OR CYPHLUTHRINE ISOMERS CONTAINING IMPROVED QUANTITY OF EFFICIENT ISOMERS

摘要

A mixture of isomers of cypermethrin or cyfluthrin enriched in the more insecticidally active c2 or t2 isomer, or both, is prepared by adding alpha -hydroxy-3-phenoxyphenylacetonitrile or its 4-fluoro analog to a refluxing solution of 3-(2,2-dichloroethenyl)-2-2-dimethylcyclopropanecarbonyl chloride in a hydrocarbon solvent boiling in the range of about 75 DEG to 115 DEG C. in an inert atmosphers, without an acid acceptor being present in the reaction mixture. The product is recovered by washing the reaction mixture with aqueous base.