Novel heterocyclic systems of pyridazines

Abstract

Heterocycles very often play an important role in Medicinal Chemistry. Pyridazines represent a heterocyclic system of remarkable pharmacological efficiency. In view of these facts and in continuation of our systematic work on the synthesis and reactivity of pyridazine compounds, the pyridazin-3(2H)-ones 1 reacted with phosphorus oxytrichloride to give 3-chloropyridazines 2 which on treatment with hydrazine hydrate gave the hydrazino derivatives 3. The reactivity of the hydrazino compounds 3 towards some reagents namely, formic acid, acetic acid, benzoyl chloride, p-nitrobenzaldehyde, 2-naphthaldehyde, carbon disulpide, and ethyl chloroformate were investigated. The 3-hydrazino derivatives 3 undergo cyclization to afford the triazolo[4,5-b]-pyridazines (4, 5, 6, 9, 10, 11 and 14). Fusion of 3 with malononitrile and ethyl cyanoacetate afforded the pyrazolone derivatives 15 and 17 respectively. On the other hand the hydrazino derivatives 3 reacted readily with oxalyl chloride to produce 1,2,5-triazino-2(H)-3,4-dione derivatives (18). The chemical structures of the synthesized heterocylic derivatives were determined through chemical reactions and spectral data using modern spectroscopic techniques.