The pyrethrins and related compounds. Part XXIX: Haloallylbenzyl esters

Synthesis and bioassay of a series of esters based on pyrethroidal acids established that the activity of halosubstituted allylbenzyl esters depends on the position and stereochemistry of substitution in the allyl side‐chain, on the substitution pattern on benzyl, on the esterifying acid, and, to a lesser extent, on the nature of the halogen substituent itself. The most powerful combination of the first four parameters for activity against houseflies is in ( Z )‐3‐haloallylbenzyl esters of the (1 R )‐ cis 3‐(2,2‐dibromovinyl) acid. Other combinations have moderate to low activity. Some aspects of the variation conform to previously recognised patterns, others define more precisely the requirements for the side‐chain to confer activity. The pattern of response of activity to cyano‐substitution at the α‐position, noted earlier, persists in the current compounds, and is here analysed quantitatively.