Reaction of 2-Arylhydrazono-3-oxonitriles with Hydroxylamine. Synthesis of 3-Amino-4-arylazoisoxazoles

Whereas the 2-arylhydrazono-3-oxonitriles 1a-e react with hydroxylamine hydrochloride and sodium acetate in refluxing ethanol to yield the amidoximes 2a-e, 3-amino-4-arylazo 5-substituted isoxazoles (3a-e) are formed when 1a-e are treated with hydroxylamine in aqueous ethanol. On the other hand, treatment of 1a-e with hydroxylamine in the presence of excess methanolic sodium methoxide has resulted in the formation of the 5-amino-4-arylazo 3-substituted isoxazoles 4a-e, Ethyl arylazocyanoacetate (11a-e) reacts with hydroxylamine hydrochloride and sodium acetate to yield the amidoximes 12a-e, which could be readily cyclized into the 3-aminoisoxazoles 13a-e by the action of methanolic sodium methoxide. The behavior of 2 toward the action of thionyl chloride, benzaldehyde, and hydrazines is reported. © 1975, American Chemical Society. All rights reserved.