Green and comparative route to 6-(pyrrolidin-1-yl)-thiazolo [4,5-d] pyrimidines using novel thiazole-based Pd(II) catalysts

Three innovative Pd(II) complexes were synthesized through the reaction of Pd(II)ions with thiazole ligands: BZU, BIU, and BTU. These complexes, along with their ligands, were characterized using a diverse set of analytical methods, including infrared spectroscopy, ¹H and ¹³C NMR spectroscopy, X-ray diffraction, UV-visible spectroscopy, CHN elemental analysis, mass spectrometry, thermogravimetric analysis, and magnetic susceptibility tests. The results indicated that the structures of BZU-Pd, BIU-Pd, and BTU-Pd complexes are square planar. To explore their catalytic properties, the thiazole-based complexes were tested in a four-component condensation reaction under mild and eco-friendly conditions. The study systematically assessed the effects of various catalyst types, such asLewisacids, bases, and ionic liquids, as well as the influence of solvent choice and catalyst concentration. Optimal conditions revealed that all catalysts exhibited notable catalytic effectiveness, with high turnover frequency (TOF) values showcasing their ability to efficiently produce 6-(pyrrolidin-1-yl)-[1,5-a] thiazolo [4,5-d] pyrimidine derivatives. Moreover, the three catalysts retained their efficiency throughout the reaction, with the first catalyst maintaining its effectiveness for eight cycles, while the other two catalysts preserved their efficiency for six cycles each. This method, characterized by its simplicity, safety, stability of the catalysts, rapid reaction times, and high product yields, presents significant promise for future applications in industry.