Solvent free regioselective cyclization of 3-allylmercapto-1,2,4-triazoles to thiazolo[3,2-b]1,2,4-triazoles over sulfuric acid adsorbed on silica gel

3-mercapto-1,2,4-triazoles were condensed with allyl bromide in the presence of a base to afford the corresponding 3-allyl compounds 2. The latter were cyclized regioselectively to give 2,3-dihydro-3-methylthiazolo[3,2-b]1,2,4-triazoles 3.