Studies on Pyridazines. XXV. The Ring-opening Reactions of N-Methoxypyridazinium Salts with Nucleophiles

Abstract

The reaction of 1-methoxypyridazinium methosulfate (1) with cyanide ion resulted in the ring fission and subsequent elimination of N₂ to give the cyano substituted vinyl acetylenes (2 and 3) and 1, 3-butadienes (4). On the other hand, reactions of the salt (1) with hydroxide and dicyanomethyl anion resulted in the similar ring-opening, followed by elimination of the methoxyl group, to give vinyl diazomethanes (6 and 9), which were easily converted into the corresponding pyrazole derivatives (7 and 10) by an intramolecular 1, 3-dipolar cycloaddition. The reaction mechanism is also discussed.