A Click Strategy for the Immobilization of MacMillan Organocatalysts onto Polymers and Magnetic Nanoparticles

A chemically modified, first generation MacMillan imidazolidin-4-one has been anchored onto 1% DVB Merrifield resin and Fe3O4 (5.3 +/- 1.4 nm) magnetic nanoparticles through copper-catalyzed alkyne azide cycloaddition (CuAAC) reactions. The resulting immobilized catalysts have been successfully used in the asymmetric Friedel-Crafts alkylation of N-substituted pyrroles with alpha,beta-unsaturated aldehydes. The PS-supported catalyst (B) showed higher catalytic activity and enantioselectivity, while the MNP-supported one (A) showed higher recyclability and could be used in a sequential process with intermediate magnetic decantation.