Synthesis of dihydropyrimidinone and dihydropyridine derivatives by a GQDs-based magnetically nanocatalyst under solvent-free conditions

A novel and heterogeneous catalyst were prepared of magnetic nanoparticles Fe3O4 coated with silicate modified with graphene quantum dot-copper (GQD/Cu) and used as an efficient catalyst in the multicomponent reactions of Biginelli and Hantzsch. The nanocatalyst was examined by Fourier Transform Infrared (FTIR), thermogravimetric-differential thermal, X-ray powder diffraction (XRD), vibrating sample magnetometer (VSM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM) analysis. A wide range of 3, 4-dihydro pyrimidine-2-(1 H)-one (DHPM) and 1, 4-dihydro-pyridine (DHP) derivatives were synthesized with good-to-excellent efficiencies in the presence of the catalyst using a combination of aldehydes, 1, 3-dicarbonyls, and urea/ammonium acetate. The catalyst was taken out and recovered from the reaction mixture by an external magnetic field and reused after six runs with minimal activity loss.