Synthesis of pyrazole, 1,3,4-thiadiazole,and 1,2,4-triazole derivatives by condensatoin of 1,3-dioxo compounds with thiosemicarbazide derivatives

The reaction of -diketones with 2-unsubstituted thiosemicarbazides leads to the formation of the corresponding 1-thiocarbamoyl-5-hydroxy-2-pyrazolines, which readily undergo aromatization to give pyrazoles, while the reaction of benzoylacetaldehyde leads to the formation of the corresponding hydrazone. Acetylacetone 2-methyl- and 2,4-dimethylthiosemicarbazones are inclined to undergo tautomerization and, depending on the conditions, can exist in enehydrazine, hydrazone, 1,2,4-triazoline, and 1,3,4-thiadiazoline forms or mixtures of these forms. Upon heating these substances are converted to mixtures of the 1,3,5-trimethylpyrazole and the corresponding 1,2,4-triazoline-5-thione. The structures of the compounds were studied by means of IR and ¹H, ¹³C, and ¹⁵N NMR spectroscopy and mass spectrometry.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1260–1270, September, 1990.