Synthesis of novel pyridazino[3,4-b]quinoxalines

The pyridazino3,4-b]quinoxaline 12 was synthesized by the cyclization of the α-arylhydrazonoacyl-hydrazide 11. The reaction of compound 12 with phosphoryl chloride gave pyridazino3,4-b]quinoxaline 13, whose reactions with sodium azide or cyclic secondary amines provided pyridazino3,4-b]quinoxalines 14,17 and 18, respectively. The acylhydrazide 15 was also cyclized to pyridazino3,4-b]quinoxaline 16.