The pyrethrins and related compounds. Part XXXVIII—optimisation of insecticidal activity in 3‐[(alkoxyimino)methyl]‐4‐fluorobenzyl esters

Abstract

AbstractOptimisation of activity in 3‐[(alkoxyimino)methylbenzyl] esters has been investigated by introducing an α‐cyano group and a fluorine atom in position 4 of the benzylic moiety in conjunction with varying the length and nature of the side chain. Of the five side‐chain variations investigated, the 3‐methoxyiminomethyl was more effective than others. Introduction of fluorine in position 4 of the benzylic moiety generally increased activity, particularly against mustard beetles, as in previous instances. Surprisingly, the effect on insecticidal activity of introducing an α‐CN group ranged from positive to negative depending upon the nature of the alkoxyimino substituent, an effect not observed previously. The most effective esters were derived from α‐cyano‐4‐fluoro‐3‐[(methoxyimino)methyl]benzyl alcohol, which was synthesised from 2‐{4‐fluoro‐3‐[(hydroxyimino)methyl]phenyl}‐1,3‐dioxolane.