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 1H 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 μg/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. Keywords: Diacylhydrazine, pyrazole, synthesis, herbicidal activity.