Synthesis of 3-(Alditol-1-yl)triazolo[4′,3′:2,3]-1,2,4-triazino[5,6-b]indoles

A series of the hydrazones were prepared by the reaction of 3-hydrazino-5H-1,2,4-triazino[5,6-b]indole (1) with monosaccharides, and their acetylation was studied. Cyclodehydrogenation of the hydrazones gave 3-(substituted)-10H-1,2,4-triazolo[4′,3′:2,3][1,2,4]triazino[5,6-b]indole, whose acetylation and partial acetylation were carried out. The ring-chain tautomerism of the hydrazones promoted their heterocyclization. The linear structure, and not that of the angular isomer, has been selected for the products. This structure has been confirmed from a model study of the cyclization of the acetaldehyde derivative of 1, which was found to be identical with that product obtained from the reaction of 4,5-diamino-3-methyl-1,2,4-triazole with isatin. Periodate oxidation of the hydrazones and their cyclized products was also studied.