KADETHRIN

Kadethrin is used to control household pests, particularly houseflies, mosquitoes and cockroaches. It is normally used in combination with other pyrethroid insecticides and synergists.

Kadethrin is used almost wholly indoors and therefore little has been published on its environmental fate. Information on its photodegradation and metabolism in rats has been reported.

Kadethrin is unstable to heat and it is rapidly decomposed by light. It is hydrolysed in aqueous alkaline solution to (E)-(1R)-cis-2,2-dimethyl-3- (2-oxothiolan-3-ylidenemethyl)cyclopropanecarboxylic acid (2), 5-benzyl- 3-furylmethanol (3) and its thiolactone ring-opened derivative (5) (Scheme 1).
Products of photodecomposition have been reported by Ohsawa and Casida (1979). Photo-hydrolysis of kadethrin occurs on sunlight irradiation affording 2 and 5 and 5-benzyl-3-furancarboxylic acid (4), presumably via the alcohol (3). cis-trans Isomerisation of the cyclopropane ring and E-Z interconversion about the double bond was also noted. Thus, from the lRcisE isomer (kadethrin), all of the possible isomers were found to varying degrees (ie. 1RScis-trans-E-Z mixtures).
Photo-hydrolysis products (e.g. 2 and 5) were also found aS isomers. The facility of the isomerisation process was considered to be due to resonance stabilisation of a triplet diradical, one form of which (6) is shown in Scheme 1. Kadethrin also yielded a lactone (7) derived from the cyclopropane ring. Photo-oxidation of the alcohol moiety analogous to that reported for resmethrin was also found. The hydroxylactone (8) and the benzyloxylactone (9) were reported (but the hydroxycyclopetenolone [resmethrin, 61) was absent.