A convenient synthesis of novel pyridazino[3,4‐b]quinoxaline and pyrazolo[3,4‐b]quinoxaline utilizing 1,3‐dipolar cycloaddition reaction

Abstract The reaction of 2,6‐dichloroquinoxaline 4‐oxide 4 with methylhydrazine gave 6‐chloro‐2‐(1‐methylhydrazino)quinoxaline 4‐oxide 5, whose reaction with dimethyl acetylenedicarboxylate or 2‐chloroacrylonitrile resulted in the 1,3‐dipolar cycloaddition reaction to afford 7‐chloro‐3,4‐bismethoxycarbonyl‐1‐methyl‐1,2‐dihydropyridazino[3,4‐b]quinoxaline 6 or 6‐chloro‐3‐hydroxymethylene‐1‐methyl‐2,3‐dihydro‐1H‐pyrazolo[3,4‐b] quinoxaline hydrochloride 7, respectively.