| abstract |
A method for preparing a pyrethroid insecticide of general formula:n wherein the two hydrogen atoms on the cyclopropane ring are in the cis- configuration, in which an acid of formula:n is neutralised with a water-soluble base and then reacted in the presence of a phase-transfer catalyst with a solution in a substantially water-immiscible organic solvent of an alpha-cyanobenzyl aryl sulphonate of formula:n the substituents in the formulae having the following meanings; A represents an optionally substituted aryl group; R, and R 2 represent hydrogen or halogen; and R 3 and R 4 represent chlorine, bromine, or methyl. |