SYNTHESIS OF PYRAZOLE, 1,3,4-THIADIAZOLE, AND 1,2,4-TRIAZOLE DERIVATIVES BY CONDENSATION OF 1,3-DIOXO COMPOUNDS WITH THIOSEMICARBAZIDE DERIVATIVES

Article abstract of DOI:10.1007/BF00472492

The reaction of β-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.