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

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Abstract
The reaction of 3‐hydrazino[1, 2, 4]triazino[5, 6‐b]indole I with nitrous acid affords the azide III which could be cyclized with acetic anhydride to 10‐acetyl‐10H‐tetrazolo[5′,1′:3, 4][1, 2, 4]triazino[5, 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.