Studies of thiobenzoyl isocyanate—I

The reaction of thiobenzoyl isocyanate with hydrazines is reported. With hydrazine hydrate, 4 H -5-phenyl-1,2,4-triazole-3(2 H )-one was obtained in a good yield. In the reaction with mono-substituted phenylhydrazines, 2,3-dihydro-2-aryl-5-phenyl-1,2,4-triazole-3(1 H )-one or 3-hydroxy-1-aryl-5-phenyl-1,2,4-triazole, or both were formed: the relative amount of the triazoles depended on the nature of the substituents. The reaction with 2,4-dinitrophenylhydrazine, however, gave the semicarbazide which, when treated with aqueous sodium hydroxide or polysphosphoric acid, suffered no ring closure to the triazole. Benzoyl isocyanate reacted with benzylhydrazine, yielding the same triazolone as that obtained from the reaction of thiobenzoyl isocyanate with the hydrazine. The products from these reactions have been identified by independent synthesis as well as IR and UV spectra.