Microwave induced synthesis of the thiazolidine-2,4-dione motif and the efficient solvent free-solid phase parallel syntheses of 5-benzylidene-thiazolidine-2,4-dione and 5-benzylidene-2-thioxo-thiazolidine-4-one compounds
作者:B. R. Prashantha Kumar、M. J. Nanjan、B. Suresh、M. D. Karvekar、L. Adhikary
DOI:10.1002/jhet.5570430413
日期:2006.7
Novel microwave induced method for the synthesis of thiazolidine-2,4-dione motif under solvent phase conditions is developed. Further we report an efficient, microwave assisted method for the parallel syntheses of biologically important 5-benzylidene-thiazolidine-2,4-dione and 5-benzylidene-2-thioxothiazolidine-4-one compounds under solid-phase and solvent-free conditions. A comparative study between
Tetrabutylammonium bromide and K<sub>2</sub>CO<sub>3</sub>: an eco-benign catalyst for the synthesis of 5-arylidene-1,3-thiazolidine- 2,4-diones via Knoevenagel condensation
Phase-transfer catalyzed, energy-efficient and facile synthesis of 5-arylidene-1,3-thiazolidine-2,4-diones was developed. Three independent variables (temperature, bases and phase-transfer catalyst (PTC)) were screened through one-factor-at-a time (OFAT) study. The optimum reaction conditions suggested by the OFAT analysis were the use of tetrabutylammonium bromide (8 mol%) and potassium carbonate (1 mmol) for the reaction at 100 degrees C. The nitrogen of PTC stabilizes carbonyl groups of thiazolidine-2,4-dione (TZD). The active methylene hydrogen of TZD forms potassium salt with potassium carbonate and generates 5-arylidene-1,3-thiazolidine-2,4-diones (1-16) through nucleophilic attack on the carbonyl carbon of arylaldehydes. The prominent advantages of this new process are economic viability, shorter reaction time (15 min), simple product isolation (non-chromatographic method), good to excellent yields (78-96%) and solvent-free conditions.