PHOTOCHEMISTRY OF THE POTENT KNOCKDOWN PYRETHROID KADETHRIN

Kadethrin, 5-benzyl-3-furylmethyl (1R, cisE)-2, 2-dimethyl-3-(2ʹ-oxo-3ʹ-thiacyclopentylidenemethyl)-1-cyclopropanecarboxylate, is rapidly photoisomerized to a 1RS, cis, trans(E, Z) mixture, probably via triplet diradicals generated by direct or sensitized photolysis for each of the cyclopropanecarboxylate and vinylcarboxylate isomerizations. A thiolactone lactone is formed by attack of the carbonyl oxygen at C-3 of the cyclopropane ring. Other products originate from hydrolysis of the thiolactone and cyclopropanecarboxylate ester groupings, from oxidation of the furan ring and rearrangement of the intermediate peroxide to a benzyloxylactone derivative, and from oxidation of the alcohol moiety to benzylfuroic acid. Minor photoproducts are (1ʹR, 2ʹS) and (1ʹS, 2ʹR)-epoxykadethrin, phenylacetic acid, benzyl alcohol, and benzoic acid. Kadethrin is more toxic to houseflies and mice than isomerized esters and photodecomposed products derived from it. d-2-Octyl (1R, trans)-chrysanthemate undergoes sensitized photoisomerization much slower than d-2-octyl pyrethrate, which in turn is slower than the d-2-octyl esters of the kadethrin acid moiety and the corresponding lactone. © 1979, American Chemical Society. All rights reserved.