Abstract: Crystallizable pyrethroid isomers or enantiomer pairs are converted to more pesticidally active isomers by contacting a hydrocarbon slurry of the starting isomers with a base and a catalyst, the catalyst being substantially soluble in the slurry and selected from a quaternary ammonium compound, a quaternary phosphonium compound and a crown ether, agitating the slurry while maintaining a temperature effective for conversion, and recovering the resulting isomers. The tendency to form benzoin ester by-product is reduced by including in the slurry a weak base, an aldehyde scavenger such as a metabisulfite, and/or a tetraalkyl (C.sub.1 -C.sub.5) ammonium halide catalyst dissolved in an aprotic solvent such as an organic nitrile. The process typically is effective for enriching cypermethrin, cyfluthrin and (cyano (3-phenoxyphenyl)methyl 3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropanecarboxylate in the more active species.

Abstract: 2-Methallyloxyphenol is produced selectively in good yield, high purity and without having to separate and recycle large amounts of catechol, in the reaction of methallyl chloride with catechol, by forming a substantially non-aqueous mixture of an alkali metal catecholate and a molar excess of methallyl chloride perferably in a polar organic solvent in which the methallyl chloride is substantially insoluble, agitating the mixture to produce a two-phase system comprising an organic first phase containing product 2-methallyloxyphenol dissolved in methallyl chloride and a polar second phase containing unreacted catecholate, and recovering product 2-methallyloxyphenol from the first plase. The presence of a quaternary ammonium or phosphonium catalyst in the reaction mixture further reduces undesired ring-alkylated by-products.