The pyrethrins and related compounds. XIX Geometrical and optical isomers of 2,2‐dimethyl‐3‐(2,2‐dichlorovinyl)‐cyclopropanecarboxylic acid and insecticidal esters with 5‐benzyi‐3‐furylmethyi and 3‐phenoxybenzyl alcohols

Abstract

Abstract Esters of 2,2‐dimethyl‐3‐(2,2‐dichlorovinyl)‐cyclopropanecarboxylic acid with appropriate alcohols are more active insecticides than the corresponding 3‐isobutenyl compounds (chrysanthemates). (±)‐ Cis and (±)‐ trans forms of the dichloro acid are obtained by fractional crystallisation of the mixed acids or by hydrolysis of the ethyl esters separated by fractional distillation. The (±)‐ cis and (±)‐ trans acids are resolved into their (+)‐ and (‐)‐forms with α‐methyl‐benzylamine and threo‐l‐ p ‐nitrophenyl‐2‐N,N‐dimethyiamino‐propane‐1,3‐diol respectively. As for the corresponding chrysanthemates, the (+)‐ cis and (+)‐ trans acids give esters more active as insecticides than their enantiomers.