Synthesis and biological activities of some novel aminomethyl derivatives of 4-substituted-5-(2-thienyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones

A novel series of compounds were synthesized by cyclic condensation reaction of substituted isothiocyanate (2a–c) with 2-thiophenecarboxylic acid hydrazide (1) in the presence of ethyl alcohol, to obtain intermediate thiosemicarbazides (3a–c), which were further treated with sodium hydroxide in the presence of ethanol to obtain triazole derivatives (4a–c). The latter were refluxed with substituted secondary amines and formaldehyde for 6–10 h to afford Mannich bases (5a–k). The synthesized compounds were characterized on the basis of their spectral (IR, 13C and 1H NMR) data and evaluated for biological activities. Some of the compounds were found to exhibit significant antimicrobial and antioxidant activity.

Graphical abstractA series of some new Mannich bases of 4-substituted-5-(2-thienyl)-2,4-dihydro-3H-1,2,4-triazole-3-thiones (5a–k) were synthesized using appropriate synthetic route and tested for the biological activities.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Mannich bases of 4-substituted-5-(2-thienyl)-1,2,4-triazole-3-thiones were prepared. ► Synthesis compounds were confirmed by IR, NMR and elemental analysis. ► The compounds have been tested in vitro for biological effects.