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 c...