スマイル転位の研究(第13報)3(2H)-Pyridazinoneにおけるスマイル転位の条件

概要

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Reaction conditions for the Smiles rearrangement in the 3(2H)-pyridazinone system were investigated. 5-(o-Acetamidophenylthio)-4-chloro-3(2H)-pyridazinones (IVa, b, c) underwent the base-catalyzed Smiles rearrangement with ease and subsequent cyclization to afford 10H-benzo[b]pyridazino[4,5-e](1,4)-thiazin-4(3H)-ones (IIIa, b, c). Acid treatment of 5-(o-aminophenylthio)-4-chloro-3(2H)-pyridazinones (Ia, b, c) resulted in the preferential formation of 10H-benzo[b]pyridazino[4,5-e](1,4)-thiazin-1(2H)-ones (IIa, b, c) together with a small amount of IIIa, b, c. This result indicates that the acid-catalyzed Smiles rearrangement occurred in part. The thermal Smiles rearrangement of I was also observed. Behavior of I toward sodium ethoxide depends largely on the nature of the substituent at 2-position. While methyl and hydrogen derivatives (Ia, b) are fairly stable, reaction of phenyl derivative (Ic) with sodium ethoxide leads to the formation of IIc, IIIc, 4-(o-aminophenylthio)-5-ethoxy-2-phenyl-3(2H)-pyridazinone (IX) and spiro(2-phenyl-4(3H)-pyrazolone-3,2'-benzothiazoline)(X). It was elucidated that IIIc was formed via unusual displacement followed by cyclization rather than the Smiles rearrangement.
公益社団法人日本薬学会の論文
1973-02-25