Synthesis and herbicidal activity of novel pyrimidine substituted pyrazolecarboxamides

A number of novel pyrimidine substituted pyrazolecarboxamides 5a-5o were synthesized, and their structures were confirmed by 1H NMR and MS analysis. The preliminary herbicidal activity indicated that Stellaria media growth inhibition rate was over 90% for the compounds(R)-N-1-(4-chlorophenyl)ethyl-3-(difluoromethyl)-1-(4,6-dimethoxypyrimidin-2-yl)-1H-pyrazole-4-carboxamide(5c), N-(1-(4-chlorophenyl)ethyl)-1-(4,6-dimethoxypyrimidin-2-yl)-N-methyl-3-(trifluoromethyl)-1H-pyrazole-4-carboxamide(5i) and N-(1-(4-chlorophenyl)ethyl)-1-(4,6-dimethoxypyrimidin-2-yl)-3-(trifluoromethyl)-1H-pyrazole-4-carboxamide(5k) by postemergence foliar spray processing at 150 g/hm2; and the compounds N-1-(4-chlorophenyl)ethyl-3-(difluoromethyl)-1-(4,6-dimethoxy-pyrimidin-2-yl)-1H-pyrazole-4-carboxamide(5b) and 5c showed inhibition rate of 100% against S.media by preemergence soil spray processing at the same dose. Compounds of this structure can be potentially used as lead compounds for herbicide.