Studies of Acenaphthene Derivatives. XVII. The Reaction of Benzylideneacenaphthenone with Hydrazines

The reactions of benzylideneacenaphthenones with hydrazines are reported. The reaction of benzylideneacenaphthenone with hydrazine hydrate in methanol at 40°C gave 1-hydroxy-2-hydrazinobenzylacenaphthylene, which was then cyclized to the 1-acetylpyrazoline by treating it with acetic anhydride. The hydrazino compound reacted with phenyl isocyanate to give the 1:2-adduct, which, when then treated with hydrochloric acid, suffered ring closure to the pyrazoline compound. Under severe conditions with hydrazine hydrate, however, the reductive cleavage reaction took place, giving the hydrazones of both acenaphthenone and benzaldehyde. Similar phenomena were also observed in the reaction with p-substituted benzylideneacenaphthenones. On the other hand, the reaction with phenylhydrazines in ethanol containing sulfuric acid afforded directly the expected pyrazolines, from which pyrazoles were then prepared by treating them with lead tetraacetate. Furthermore, the corresponding pyridazine was formed in the reaction of phenacylideneacenaphthenone with hydrazine hydrate, while the reaction with 2,4-dinitrophenyl-hydrazine gave the pyrazoline compound.