Abstract
1-Carbamoyl-4-acylthiosemicarbazide (II) was prepared by the reaction of semicarbazide and acyl isothiocyanate, and its cyclization reaction was examined. Treatment of (II) with sodium hydroxide solution afforded 3-aryl (or alkyl)-1H-1, 2, 4-triazole-5-thiol (III), with acetic anhydride gave 2-acylamido-5-methyl-1, 3, 4-thiadiazole, and reaction of (III) with methyl iodide gave the S-methylated compound. Treatment of (II) with conc. sulfuric acid or conc. hydrochloric acid gave a substance assumed to be 2-acylamido-1, 3, 4-thiadiazol-5-ol (VIII), besides (III). Hydrolysis of 2-benzamido-1, 3, 4-thiadiazol-5-ol (VIIIa) with conc. hydrochloric acid afforded benzoic acid and thiosemicarbazide hydrochloride, and 2-amino compound was not isolated. The benzoate of (VIIIa) agreed completely with the dibenzoylated compound of m.p. 177°, obtained by hydrochloric acid hydrolysis of 1-carbamoylthiosemicarbazide of 1-(N-phenylcarbamoyl) thiosemicarbazide.
