Synthesis and Herbicidal Activity of Some Novel Pyrazole Derivatives

Some novel pyrazole derivatives were designed and synthesized through multi-step reactions from substituted phenol as starting material. Their structures were confirmed by H-1 NMR, FTIR, MS and elemental analysis. All these compounds were evaluated their herbicidal activity. The preliminary bioassay results indicated that some of title compounds displayed moderate herbicidal activity at 200 mu g/mL. Among them, compounds 4-chloro-N'-(2-(2,5-dimethyl-phenoxy) acetyl)-3-ethyl-1-methyl-1H-pyrazole-5-carbohydrazide, 4-chloro-N'-(2-(2,4-dichlorophenoxy) acetyl)-3-ethyl-1-methyl-1H-pyrazole-5-carbohydrazide, 4-chloro-3-ethyl-1-methyl-N'-(2-(m-tolyloxy) acetyl)-1H-pyrazole-5-carbohydrazide and 4-chloro-3-ethyl-1-methyl-N'-(2-(3-nitrophenoxy) acetyl)-1H-pyrazole-5-car-bohydrazide possessed 95%, 100%, 95% and 95% inhibition against Brassica campestris respectively. In the further bioassay, the compound 6l exhibited excellent herbicidal activity either monocotyledon or dicotyledon plant at 150 g/ha.