Regioselective S -> N allylic transposition of 3-allylthio 1,2,4-triazinone without solvent, and catalyst under microwave irradiation

The facile and regioselective cyclization of 3-allylsulfanyl-6-methyl-2H-[1 ,2,4-]triazin-5-one 2 to 3,6-dimethyl-2,3-dihydro-thiazolo [3,2-.b.][1,2,4] triazin-7-one 3has been performed by the catalytic action of H2SO4 Compoun d 2 underwent [3,3] sigmatropic shift under microwave irradiation to afford 4N allyl derivative 5 in fairly good yield. Treatment of 5 with cone, sulp huric acid afforded the corresponding 2-methyl thiazolo[2,3-c] triazinone 7 .