trans-2,5-Hexadien-l-yl Chrysanthemates and Related Esters

As a simplified model of natural pyrethrins, trans-2,5-hexadien-l-yl chrysanthemate (V), and its 2- or 3-methyl substituted homologues (III and IV), were prepared and tested for insecticidal activities against houseflies. All these compounds retained sufficient insect toxicity to illustrate an interesting relationships between chemical structure and insecticidal activity.

The cis isomer (XII) of compound V and two positional isomers, 2-methylene-4-penten-l-yl and 1,5-hexadien-3-yl chrysanthemates (XIII and XIV), were also synthesized. Of these isomers, XIII was very slightly active, but the other isomers (XII and XIV) were completely ineffective.

On the other hand, the insecticidal activity of 5-hexen-2-yn-l-yl ester (XV), en-yne analogue of V, was almost the same as that of V.