2-arylalkanoates, a new group of synthetic pyrethroid esters not containing cyclopropanecarboxylates

Although structure modifications of natural pyrethrin constituents have disclosed a variety of potent synthetic analogues, all known examples are cyclopropanecarboxylate esters, a grouping that appeared to be essential for insecticidal activity. Some new substituted 2‐phenylalkanoates, whose biological activities are of a similar nature and potency to those of conventional pyrethroids, are now reported. 5‐Benzyl‐3‐furylmethyl and 3‐phenoxybenzyl 3‐methyl‐2‐phenylbutyrates and their analogues are potent insecticides. Activity is increased on the introduction of appropriate groups into the 3 and/or 4‐positions of the aryl ring and the (S)‐2‐phenylalkanoates are far more active than their (R)‐enantiomorphs. Structure/activity relationships are compared with those for conventional pyrethroids. Some of the new series compare favourably with typical insecticides in tests against Musca domestica, Spodoptera litura and Plutella xylostella.