Ohno_2004_J.Pestic.Sci_29_96

A series of novel 1-alkyl-3-aryloxypyrazole-4-carboxamide derivatives were synthesized and their herbicidal activity and crop safety examined under flooded conditions. Introduction of an aryloxy group at the 3-position of the pyrazole ring was accomplished with a nucleophilic substitution reaction of 3-hydroxypyrazoles with halobenzenes which were activated by electron-withdrawing groups such as a nitro group. The 3-trifluoromethylphenoxy analogs provided good results. The level of activity also varied with the N-substituents of the carbamoyl group, especially the 2,4-difluorophenyl group which provided the best combination of herbicidal activity and crop selectivity. Among the compounds synthesized, N-(2,4-difluorophenyl)-1-ethyl-3-(3-trifluoromethylphenoxy)pyrazole-4-carboxamide (KPP-856) showed good herbicidal activity against various annual lowland weeds and excellent crop safety at 33 g a.i./ha.