14C-labelling of fenpropathrin, α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate

α-Cyano-3-phenoxybenzyl 2, 2, 3, 3-tetramethylcyclopropanecarboxylate (fenpropathrin), a new potent synthetic pyrethroid, was labelled with carbon-14 at the cyclopropyl group for studies on its metabolism in mammals, fishes, plants and soils. Condensation of potassium cyanide-14C (2) with 1,3-diphenyl-2-thiourea (3) in the presence of basic lead carbonate gave 1-cyano-14C-N,N'-diphenylformamidine (4). Reduction of 4 followed by hydrolysis with barium hydroxide afforded glycine-2-14C (6). Esterification of 6 with ethanol in the presence of anhydrous hydrogen chloride gave ethyl glycinate-2-14C hydrochloride (7). Diazotization of 7 followed by condensation with 2, 3-dimethyl-2-butene yielded ethyl 2, 2, 3, 3-tetramethylcyclopropane-1-14C-carboxylate (8). Hydrolysis of 8 gave 2, 2, 3, 3-tetramethylcyclopropane-1-14C-carboxylic acid (9), which was esterified with α-cyano-3-phenoxybenzyl bromide (10) to afford fenpropathrin(cyclopropyl-1-14C) (1) in 13 % yield from 2. (author)