Chiral-Supported Ionic Liquids in Asymmetric Synthesis

Abstract

Supported ionic liquids (SILs) have been engaged in asymmetric synthesis, providing better recoverability, enantioselectivity, catalytic action, and economical and environmentally benign paths. SILs have minimized the limitations of previous homogeneous and heterogeneous systems and also opened new routes to design chiral heterogeneous systems with improved catalytic efficiency, including stability and recyclability. To carry out asymmetric reactions, both chiral catalysts and ILs have been supported onto a single support material, generally through a physical immobilization approach. In some cases, chiral ionic liquids have been grafted onto supports to obtain chiral SIL. The chirality has also been transferred into the resulting heterogeneous catalyst by covalently grafting chiral catalysts onto catalytic centers of supports by using ionic liquids as linkers. In this chapter, the potential catalytic role of all types of chiral SILs in several asymmetric organic reactions, such as hydrogenation, Mannich, epoxidation, Michael addition, Strecker, Diels-Alder reaction, etc., has been discussed.