Abstract:
Benzoylation of 1-benzoyl-thiosemicarbazide (2) or dibenzoylation of thiosemicarbazide (1) with benzoyl chloride, in the presence of pyridine, gave a mixture of 1,2-dibenzoyl-thiosemicarbazide (4) and 1,4-dibenzoyl-thiosemicarbazide (5). Treating the mixture of isomers with Na2CO3 5% solution, at boiling temperature, gave 4H-5-mercapto-3-phenyl-1,2,4-triazole (3) (and not 4H-4-benzoyl-5-mercapto-3-phenyl-1,2,4-triazole (6), as it was expected), formed from 1,4-dibenzoyl-thiosemicarbazide, and 1,2-dibenzoyl-hydrazine (8), formed from 1,2-dibenzoyl-thiosemicarbazide. The structure of the isomeric 1,4-dibenzoyl-thiosemicarbazide was confirmed by IR and NMR spectroscopy.
Keywords:
4H-5-mercapto-3-phenyl-1,2,4-triazole, dibenzoyl-thiosemicarbazide, cyclisation
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