Synthesis of Magnetic Nanoparticles and Polymer Supported Imidazolidinone Catalysts for Enantioselective Friedel-Crafts Alkylation of Indoles

Abstract

The copper catalyzed Huisgen cycloaddition has been used for the immobilization of enantiopure tbutyl-imidazolidin-4-one on magnetic nanoparticles (MNP-A, MNP-B) at two different anchoring sites and a Merrifield resin support (PS). The obtained catalysts have been characterized by FTIR, elemental analysis, XRD and TEM. These catalysts have been used in alkylation of indoles with α,β-unsaturated aldehydes affording the desired products in high yields with excellent enantioselectivities. MNP-A with the magnetic nano-functionalization at the amide nitrogen (N3) position shows relatively lower catalytic efficiency compared to MNP-B with nanoparticles anchored at the O-aryl residue. The PS, owing to its high loading of the catalyst, shows higher catalytic activity than MNP-A and MNP-B but the magnetic nanocatalysts show higher recycling efficiency than the PS as they can be easily separated from the reaction medium through simple magnetic decantation.