Synthesis of pyridazino[3,4‐b]quinoxalines and pyrazolo[3,4‐b]‐quinoxaline by 1,3‐dipolar cycloaddition reaction

Abstract The pyridazino[3,4‐b]quinoxalines 6a,b and pyrazolo[3,4‐b]quinoxaline hydrochloride 9 were synthesized by the 1,3‐dipolar cycloaddition reaction of 6‐chloro‐2‐(1‐methylhydrazino)quinoxaline 4‐oxide 5 with dimethyl or diethyl acetylenedicarboxylate and 2‐chloroacrylonitrile, respectively. The reaction mechanisms were postulated for the formation of 6a,b and 9.