One-Pot Synthesis of 3,4-Dihydropyrimidine-2-one Derivatives via Biginelli Reactions Catalyzed by SnCl2@MNPs

The magnetic Fe3O4 nanoparticles were prepared by a co-precipitation method. The magnetic nanoparticles (MNPs) with core-shell structure were constructed by alkali-catalyzed hydrolysis of tetraethyl orthosilicate, and SnCl2 grafted on MNPs (SnCl2@MNPs) was successfully synthesized by a co-precipitation method. Then the catalyst of SnCl2@MNPs was further analyzed by a series of modern characterization methods for exploring the microstructure and composition. The results showed that SnCl2 was uniformly dispersed on the surfaces of MNPs and there were strong interaction forces between SnCl2 and MNPs. Subsequently, the Biginelli reaction was performed to investigate the catalyst performance, the results showed that 3,4-dihydropyrimidin-2(H-1)-ones were efficiently synthesized by a three component one-pot reactions of aromatic aldehydes or heterocyclic aldehydes, carbamide or thiourea, and alpha,beta-dicarbonyl compounds with high yields of 78%similar to 96%. The active fraction of SnCl2 in SnCl2@MNPs is uniformly distributed on the surface of MNPs and in the form of microcrystalline that increases the effective contact area with substrates. The highly activity of SnCl2@MNPs is ascribed to the synergistic effect of SnCl2 and the abundant hydroxyl cluster in MNPs. In addition, the catalyst can be recovered using an external magnetic field and reused at least 7 times without a considerable decrease in its catalytic activity.