Magnetic Nanoparticles-Supported Chiral Catalyst with an Imidazolium Ionic Moiety: An Efficient and Recyclable Catalyst for Asymmetric Michael and Aldol Reactions

A magnetic nanoparticles-supported chiral aminocyclohexane in combination with sulfamide, which was modified by an imidazolium ionic moiety, was prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermal gravimetric (TG) analysis and elementary analysis. The catalyst was successfully applied not only in the enantioselective Michael addition but also in the asymmetric aldol condensation to afford good to excellent yields (70-94%) and satisfactory stereoselectivity (ee: 92-100%, dr: 91:9-99:1).The role of the ionic moiety was verified by comparison of the catalyst with an ionic moiety-free counterpart. The heterogeneous catalyst was easily separated and recovered using external magnetic force and can be used for up to five times without obvious loss in its catalytic activity.