Thiazolidinones: novel insights from microwave synthesis, computational studies, and potentially bioactive hybrids

Various 5-arylidene derivatives were prepared via a Knoevenagel condensation-type reaction of aromatic/heteroaromatic aldehydes with rhodanine or thiazolidine-2,4-dione (TZD) catalyzed by EDA/AcOH under microwave heating. This convenient methodology is broad in scope (49 different products were obtained), delivers excellent yields (up to 99%), and requires low catalyst loading (10 mol %). This new approach was successfully applied to the synthesis of eight novel imidazo[1,2-a]pyridine-thiazolidinone hybrids in good to excellent yields (66-99%). A spectroscopic study of compounds 3n and 4n was carried out using torsion angle analysis and ¹³C NMR chemical shift calculations to evaluate the absence of expected signals in the NMR spectra of these compounds. Their photophysical properties were also assessed, confirming a preference for a fluorescence mechanism via an ICT (intramolecular charge transfer) process.