Tetrabutylammonium bromide and K₂CO₃: an eco-benign catalyst for the synthesis of 5-arylidene-1,3-thiazolidine- 2,4-diones via Knoevenagel condensation

Abstract

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°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.

GRAPHICAL ABSTRACT

Keywords:

• phase-transfer catalyst
• Knoevenagel condensation
• 5-arylidene-1,3-thiazolidine-2,4-dione
• OFAT study
• green synthesis

Acknowledgements

The authors are thankful to the President, Gokaraju Rangaraju Educational Society, Hyderabad and the Chairman, Natco Pharma Ltd, Hyderabad, for providing the necessary facilities.

Supplemental data

Supplemental data for this article can be accessed at 10.1080/17415993.2014.970555.