A Convenient Synthesis of Novel Pyrido(1′,2′: 1,2)imidazo[5,4-d]-1,2,3-triazinones from Imidazo[1,2-a]pyridines

The imidazo [1,2-a]pyridine system was investigated as a synthon for the building of very attractive fused triazines, a planar, angular tri-heterocycle with potential biological activity. Thus ethyl 3-nitroimidazo[1,2-a]pyridine-2-carboxylate was treated with ammonia or with an excess of primary amines to generate the corresponding substituted nitro carboxamidoimidazopyridines. The nitro substituent in the latter products, was reduced to yield 3-amino-2-carboxamidoimidazo[1,2-a]pyridine derivatives, which in turn were treated with nitrous acid to furnish 1-oxo-2-substituted pyrido(1′,2′:1,2)imidazo[5,4-d]-1,2,3-triazines.