Abstract
Four types of azaindolizines, pyrrolo [1, 2-b] pyridazines (XVIa, b), pyrrolo [1, 2-a]-pyrimidine (XVII), pyrrolo [1, 2-a] pyrazines (XIXa, b) and pyrazolo [1, 5-b] pyridazines (XXIa, b) were synthesized by the 1, 3-dipolar cycloaddition of diazinium dicyanomethy-lides (IVa, b V and VIa, b) and pyridazine N-imines (VII and VIII) with dimethyl acetylenedicarboxylate. Imidazo [1, 2-b] pyridazine (XXII) was synthesized by the intramolecular cyclization of VII and VIII with sodium methoxide. Further, an improved method for VII and VIII by N-amination of pyridazines with hydroxylamine O-sulfonic acid was devised. The nuclear magnetic resonance, ultraviolet and infrared spectra of the ylides and azaindolizines mentioned above were also discussed.
