Abstract

Background: Thiazolidinone and pyrazoles are promising heterocyclic systems enormously contributing to medicinal chemistry and when pyrazole nucleus was incorporated in other biodynamic heterocycles, the resulting molecules have displayed an increased spectrum of biological activities. There are several synthetic routes for the synthesis of thiazolidinone molecules but are having certain lacunas like, need of catalysts and desiccants, higher reaction temperature, longer reaction time, organic solvents and tedious work up procedure.

Methods: Here an ultrasound promoted one pot multicomponent protocol is developed for 2-[(1-phenyl-3-(substituted phenyl) -pyrazol-4-yl)] methylene hydrazolyl-4-thiazolidinones (6a-g). Here freshly prepared substrates, 3-(4-substituted phenyl)-1-phenyl-1H-pyrazole-4-carbaldehydes (5a-g), have been condensed with thiosemicarbazide (2) and ethylbromo acetate (3) in aqueous emulsion of surfactant, CTAB under ultrasonication.

Results: In our study the titled compounds 2-[(1-phenyl-3-(substituted phenyl) -pyrazol-4-yl)] methylene hydrazolyl-4- thiazolidinones obtained with good to excellent yields using 20 mol% aqueous emulsion of CTAB under ultrasound irradiation at 60°C.

Conclusion: First time we have provided an environmentally friendly ultrasound promoted synthetic route to 2- hydrazolyl-4-thiazolidinones (4a-g) and biologically significant 2-[(1-phenyl-3-(substituted phenyl) -pyrazol-4-yl)] methylene hydrazolyl-4-thiazolidinones (6a-g) using aqueous emulsion of CTAB as reaction medium. The method offered several advantages such as operational simplicity, easy work-up procedure, shorter reaction times and high yields. The protocol is safe, economic and convenient for obtaining library of 2-hydrazolyl/imino-4-thiazolidinones rapidly.

Keywords: 2-Hydrazolyl-4-thiazolidinones, 4-Thiazolidinones. aqueous emulsion, pyrazoles, surfactant, ultrasonication.

Graphical Abstract