Synthesis of 5,6-Diaryl-1,2,4-triazines
AbstractThe synthesis of 6-(4-methoxyphenyl)-5-phenyl-3-oxo-2,3-dihydro-1,2,4-triazine (5a) from 4-methoxybenzoin, 4-methoxybenzil, or 4-methoxybenzoin semicarbazone and semi-carbazide hydrochloride is reported. The condensation of 4-methoxybenzil with thiosemi-carbazide yielded 6-(4-methoxyphenyl)-5-phenyl-3-thioxo-2,3-dihydro-I,2,4-triazine (5b) which was converted to its 3-oxo analogue 5 a with acetic anhydride. Reduction of 5 a and 5 b with zinc and aqueous acetic acid led to the corresponding 2,3,4,5-tetrahydro-1,2,4-triazines 6 a and 6b, respectively. Oxidation of 5 b with iodine in sodium carbonate solution afforded bis [6-(4-methoxyphenyl)-5-phenyl-1,2,4-triazin-3-yl]disulphide (7). Analogous triazines were prepared by condensing 3,3'-diiodobenzil with semicarbazide hydrochloride or thiosemicarbazide.