Microwave Assisted and Efficient Synthesis of Substituted Thiazole Acid Derivatives

Background: An effective approach to the synthesis of some new (Z)-2-((5-(4-chlorobenzylidene)-4-oxo-4,5-dihydrothiazol-2-yl)amino) substituted acids 7a-l is reported under microwave irradiation as well as conventional conditions. The method provides rapid and easy access to thiazolidinone compounds in good to excellent yields. Methods: In a 100 mL round bottom flask, the compound (Z)-5-(4-chlorobenzylidene)-2-thioxothiazolidin-4-one 3 (0.5 gm, 1 mmol), triethylamine (0.2 gm, 1.2 mmol) and dichloromethane (1 mL) was added at room temperature. To the stirred reaction mixture with iodomethane (0.3 gm, 1.2 mmol) was added and stirred for 1 h at room temperature. Results: This study synthesized (Z)-5-(4-chlorobenzylidene)-2-(methylthio)thiazol-4(5H)-one 5 (Scheme 2) and screening of model reaction (Z)-2-((5-(4-chlorobenzylidene)-4-oxo-4,5-dihydrothiazol-2-yl)amino) propanoic acid 7a (Scheme 3, Table 1). This study developed the protocol for the synthesis of compound 7a by condensation of compounds 5 and 6a. After the initial success with ethanol, various solvents and bases were screened and the results are shown in Table 1. The reactions of compound 5 (1 mmol) and compound 6a (1.2 mmol), catalyzed by various bases and various solvents were selected as a model reaction to optimize the reaction conditions. Conclusion: In conclusion, we successfully developed an easy access to a new series of (Z)-2-((5-(4-chlorobenzylidene)-4-oxo-4,5-dihydrothiazol-2-yl)amino) substituted acid derivatives. This method provides an easy and rapid access to pharmaceutical important thiazolidinone derivatives. We reported here shorter reaction time, cleaner reaction profile and excellent yield of the products, by MW irradiation as well as conventional method synthesis.