A series of novel 3-(substituted benzyloxy)-6-[(un)substituted 1H-pyrazol-1-yl]pyridazine derivatives were synthesized through the condensation of various substituted benzyl alcohols with 3-chloro-6-(3,5-dimethyl-1H-pyrazole-1-yl)pyridazine (2) or 3-chloro-6-(1H-pyrazol-1-yl)pyridazine (4). 2 and 4 were obtained from the cyclization of 3-chloro-6-hydrazinylpyridazine with acetoacetone and/or 3-dimethylamino acrolein. The structures of the title compounds were identified by 1H NMR, IR spectra and elemental analysis. Preliminary bioassay showed that all of them possessed some extent herbicidal activity against Brassica campestris and Echinochloa crusgalli.

Key words: synthesis, herbicidal activity, pyridazine