Cyclization reactions of 3-hydrazino[1, 2, 4]triazino[5, 6-b]indole

The reaction of 3-hydrazino1, 2, 4]triazino5, 6-b]indole I with nitrous acid affords the azide III which could be cyclized with acetic anhydride to 10-acetyl-10H-tetrazolo5′,1′:3, 4]1, 2, 4]triazino5, 6-b]indole IIb . Cyclization reactions of I with acetic anhydride, ethyl chloroformate, carbon disulphide and aromatic aldehydes to the corresponding fused triazolo derivatives V–VIII are reported. On the other hand cyclization reactions of I with malononitrile, ethyl cyanoacetate, ethyl acetoacetate and acetylacetone to the corresponding condensed pyrazolino derivatives IX–XI are also reported. The reaction of I with α-dicarbonyl compounds to form mono and dihydrazones are reported. The structure of the compounds prepared and their cyclization mechanisms are reported.