Labelled organophosphorus pesticides. III. Synthesis of carbon-14 labelled o-(2,6-dichloro-4-methylphenyl) O,O-dlmethyl phosphorothioate

O- (2,6-Dichloro-4-methylphenyl) O,O-dimethyl phosphorothioate (5-3349) (1), a fungicide in soil, was labelled with carbon-14 individually at the aryl methyl and the phenyl ring for use in metabolic studies. The synthetic procedures are illustrated in Fig. 1. 4-Cyano-14C-phenol was quantitatively converted to 4-methyl-14C-Phenol (3a) by catalytic hydrogenation using 10% Pd-C as a catalyst. Dichlorination of 3a with chlorine gave 2,6-di-chloro-4-methyl-14C-phenol (4a). Condensation of 4a with O,O-dimethyl phosphorochloridothioate gave S-3349-(aryl methyl-14C) (1a) in the overall yield of 22% from potassium cyanide-14C. By the similar procedures, 4-methylphenol-14C6 (3b) was converted to S-3349-(Phenyl-14C6) (1b) in 70% yield.