Synthesis of Pyridazine Derivatives. VIII. N-Oxidation of 3, 4-Dimethylpyridazine Derivatives.

抄録

N-Oxidation of 6-chloro-3, 4-dimethylpyridazine afforded two kinds of product (V and VI), the latter being in a very low yield. 6-Methoxy-3, 4-dimethylpyridazine gave sole N-oxide (VIII). Catalytic dehalogenation of V and VI yielded 3, 4-dimethylpyridazine N-oxide, II from V and III from VI respectively, both II and III being also obtained by N-oxidation of 3, 4-dimethylpyridazine. V was derived to VIII. N-Oxide group in II, V and VIII was concluded to be in the position adjacent to the methyl group from the derivation of V into 1, 3, 4-trimethyl-6 (1H)-pyridazinone 2-oxide (X) by hydrolysis with dilute sodium hydroxide, followed by methylation with dimethyl sulfate and dilute alkali hydroxide. The structure of X was confirmed by the formation of 1, 3, 4-trimethyl-6 (1H)-pyridazinone (XI) by catalytic reduction which was prepared by methylation of 3, 4-dimethyl-6 (1H)-pyridazinone. Consequently, the nitrogen further removed from the methyl group is oxidized in III and VI.