Synthesis and insecticidal activity of novel 1-alkyl-3-sulfonyloxypyrazole-4-carboxamide derivatives

Abstract

In the course of an agrochemical random screening test of 1-alkylpyrazole-4-carboxamide analogs showing herbicidal activity, it was discovered that some 1-alkyl-3-sulfonyloxypyrazole-4-carboxamides exhibited high insecticidal activity. These derivatives were readily synthesized through the reaction of various amines with mixed anhydrides of pyrazole-4-carboxylic acids. All pyrazole-4-carboxamides synthesized were evaluated for insecticidal activity and their structure-activity relationships are discussed. It was found that introduction of a methyl or an ethyl group at the 1-position of the pyrazole ring increased insecticidal activity, in particular, introduction of a methylsulfonyloxy group on the pyrazole ring at the 3-position induced potent activity. The level of activity varied with N-substituents of the carbamoyl group at the 4-position of the pyrazole ring. An α-branched alkyl group, such as an isopropyl or a sec-butyl group on the amide nitrogen atom, demonstrated the highest level of activity. Among the compounds evaluated, N-sec-butyl-1-methyl-3-methylsulfonyloxypyrazole-4-carboxamide showed the highest activity against Nephotettix cincticeps, and exhibited moderate activity against both adults and eggs of Tetranychus urticae. Interestingly, substitution of a cyano group induced a higher level of acaricidal activity, while N-(3-cyanopentan-3-yl)-1-methyl-3-methylsulfonyloxypyrazole-4-carboxamide gave excellent activity against T. urticae as well as N. cincticeps. © Pesticide Science Society of Japan.