Sulfonated-polyvinyl amine coated on Fe3O4 nanoparticles: a high-loaded and magnetically separable acid catalyst for multicomponent reactions

In this study, a PVAm-bearing SO3H groups/Fe3O4 nanocomposite was prepared via a simple and in situ polymerization of acrylamide onto the surface of magnetic nanoparticles without using organosilane precursors. In order to obtain amine-functionalized magnetic, Hofmann degradation was carried out. In the following, sulfonated-polyvinyl amine coated on Fe3O4 nanoparticles was prepared by covalent grafting of chlorosulfonic acid on amine groups. The introduction of polymer to the surface of magnetic nanoparticles increases the loading content with functional groups extremely. The resulting hybrid material was effectively employed as an unprecedented acid magnetic catalyst for the one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions. High yields, mild reaction conditions, short reaction times, operational simplicity with reusability are the notable features of the catalyst. The structure of the newly developed catalyst was characterized using TGA, FT-IR, SEM, TEM, VSM, EDX, CHNS, and XRD analysis. Magnetic separation and recycling of the catalyst for at least 8 runs is possible without any significant deterioration in catalytic activity. This work is the first report of employing PVAm as a linker for immobilizing liquid acid on a support.