Studies in the heterocyclic series XVII. A new type of triazaphenothiazine heterocycle

The synthesis of derivatives of 1,4,6‐benzo[ b ]triazaphenothiazine, a novel aza‐analog of phenothiazine, is described. The parent compound was obtained by base‐catalysed condensation of 3‐amino‐2‐mercaptopyridine with 2,3‐dichloroquinoxaline in aqueous DMF. Several derivatives were also prepared by using the appropriately substituted aminomercaptopyridines and dichloro‐quinoxalines. Nitration with mixed nitric and sulfuric acids gave the corresponding 13‐nitro‐1,4,6‐benzo[ b ]triazaphenothiazine derivatives. The structures were elucidated by chemical evidence and by a study of their infrared, ultraviolet, pmr and mass spectra.