New Nano-Silica Supported Basic Ionic Liquids-Catalyzed Multicomponent Synthesis of imidazo [1,2-a] Pyridines Under Solvent-Free Conditions

Recently, the development of supported ionic liquid on magnetic nanoparticles (MNP) and multicomponent reactions in industry and academia has been a matter of intense study. In this new and environmentally benign synthetic methodology, a dihydroxyl functionalized basic ionic liquid precursor was immobilized onto the magnetic silica nanoparticles via covalent bonding to prepare a novel powerful basic catalyst (DHBIL@Si-MNPs). The synthesized catalyst was characterized extensively by various techniques. Also, the alkalinity of the DHBIL@Si-MNPs catalyst (pKb value) was obtained at 9.23. The catalytic activity of the prepared catalyst was investigated in a one-pot and three-component reaction between pyridine, phenacyl bromide, and thiocyanate to afford corresponding substituted imidazo [1,2-a] Pyridine derivatives under solvent-free conditions. Different spectroscopic methods were used to establish the structures of target compounds. The imidazopyridines were generated in excellent yields (80–98%) under the optimum conditions utilizing 10% by weight of DHBIL@Si-MNPs to pyridine, a molar ratio of 1.2: 1.2: 1 mmol (mmol), and a temperature of 100 °C. The present developed synthetic protocol permits the production of interesting medicinal compounds with high purity and different functional group tolerating abilities. Also, the other significant advantages of this protocol are highlighted by less reaction time, cleaner reaction profiles, avoidance of toxic catalysts, simplicity of the process, benign reaction conditions, use of available raw materials, and easy separation of products. The catalyst could be easily recycled from the reaction mixture using an external magnet thanks to its superparamagnetic and reused several times without any appreciable decrease in its reactivity and product yield. Graphical Abstract