Reactions of pyridine N-oxides with 3,6-dichloropyridazine

Abstract

The main products of the reaction of 3,6-dichloropyridazine with 2-methylpyridine 1-oxide were 6-chloro-2-(2-pyridylmethyl)pyridazin-3(2H)-one (XII; R = H), 6-chloro-4-(2-pyridylmethyl)pyridazin-3(2H)-one (XIV; R = H), and 6-chloropyridazin-3-yl 2-pyridylmethyl ether (XVI). 2,6-Dimethylpyridine 1-oxide gave homologues corresponding to the pyridazinones (XII) and (XIV), and, in addition, 6-chloropyridazin-3-yl 2,6-dimethyl-3-pyridyl ether (XIX). No compound corresponding to the methyl ether (XVI) was isolated. The reactions are discussed in the light of earlier studies of the action of 2-bromopyridine on pyridine 1-oxide, and it is suggested that initial formation of a 1-(pyridazinyloxy)pyridinium salt is followed by loss of a proton to give an anhydro-base.