Facile synthesis of new 10-substituted-5 H -naphtho[1,2- e ][1,2,4]triazolo[3,4- b ][1,3,4]thiadiazin-5-ones

The reaction of 2-bromo-1,4-naphthoquinone with 4-amino-5-aryl-4H-1,2,4-triazole-3-thiols in ethanol at 50°C gave the corresponding 2-[(4-amino-5-aryl-4H-1,2,4-triazol-3-yl)thio]naphthalene-1,4-diones. Their treatment with EtOH/HCl under reflux conditions produced 10-substituted-5H-naphtho[1,2-e][1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-5-ones through intramolecular cyclization.