Diazotization of 3-amino-2-cMoro pyridine (3) in the presence of dithizone (5)
gave dphenyl-2-phenylazo-4H-pyrid[o3 ,2-e] [1,3,4] thiadiazine (6). Reaction of 2-
chloro-3-nitropyridine (2, G=H) with (5) dfordd 4-phenyl -2-phenylazo -4Hpyrido
[2,3-el [1,3,4] thiadiazine (7). Reduction of the latter with H gas in the
presence of Raney nickel gave the corresponding amino derivative (12). One pot
condensation and cyclization of the latter with phenacyl bromide gave a novel
heterocyclic system (13).