Synthesis and Herbicidal Activity of 3-Aryloxy-6-chloro(or fluoro) Pyridazines

3-Aryloxy-6-chloropyridazines and 3-aryloxy-6-fluoropyridazines were prepared from the condensation of various substituted phenols with starting material 3,6-dichloropyradazine and its fluorinated derivative, 3,6-difluoropyridazine in high yields. All compounds were characterized by 1H NMR and elemental analyses, and some of the compounds were confirmed by IR. Preliminary bioassay indicates that some of the title compounds showed herbicidal activity to some extents against Brassica napus and Echinochloa crus-gall, for example, at 100 μg/mL, the inhibition of compounds Ⅲ3, Ⅲ8 and Ⅳ2 against E. crus-gall are 95.7%, 96.1% and 91.2%, respectively.