2-Aminoimidazo[1,5-a]pyridinium salts: some further oxidations

Oxidation of 1-substituted 2-aminoimidazo[1,5-a]pyridinium salts with an excess of concentrated nitric acid gave the corresponding 2-pyridylmethylenecarbamic acid hydro-salts. Oxidation of 3-substituted -2-aminoimidazo[1,5-a]pyridinium bromide with nitric acid in acetic acid gave the corresponding 1-nitro-3-substituted imidazo[1,5-a]-pyridines. The parent 2-aminoimidazo[1,5-a] pyridinium bromide yielded either type of product depending upon the reaction conditions.Oxidation of 2-amino-1-phenylimidazo[1,5-a]pyridinium bromide with lead(IV) acetate in acetic acid solution gave 2-acetamido-3-oxo-1-phenyl-2,3-dihydroimidazo[1,5-a] pyridine.