Synthesis of N-benzoyl-N-alkyl-2-aminothiazole Heliothis virescens proinsecticides
Wilkes, M.C. | Lavrik, P.B. | Greenplate, J.
N-Benzoyl-2-amino-5-chloro-4-(trifluoromethyl)thiazole amides 1 were as potential Heliothis virescens [tobacco budworm (TBW)] insecticides. The insecticidal compound 1a (R = H) also exhibited phytotoxic and rat toxicity effects, diminishing its utility as a crop insecticide. To improve selectivity, a series of N-benzoyl-N-alkyl-2-aminothiazoles were synthesized by varying the N-alkyl substituent via nucleophilic substitution or preintegration into the thiazole. Introduction of an N-alkyl substituent such as N-methyl at the amide nitrogen greatly improved selectivity by eliminating phytotoxicity and reducing acute rat toxicity. In the amide N-methyl case, the effect of deuterium incorporation in the N-methyl group on TBW mortality was investigated. The NCH3 derivative 1b exhibited a diet incorporation LC50 of 109 ppm (+/- 20 ppm) against TBW, whereas the NCD3 derivative 1j was inactive against TBW, suggesting a deuterium isotope effect in abstraction of the hydrogen atoms by cytochrome P450 enzymes.
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