Chiral porous poly(ionic liquid)s: Facile one-pot, one-step synthesis and efficient heterogeneous catalysts for asymmetric epoxidation of olefins

Abstract

Ionic liquids are potential media/solvents for asymmetric synthesis when combined with chiral catalysts, while most reported catalysts are homogenous, making them difficult to separate from the reaction systems. Herein, chiral porous poly(ionic liquid)s (CPPILs) containing chiral salen Mn(III) complex have been successfully synthesized through a simple and one-pot route involving simultaneously occurred Friedel-Crafts alkylation and quaternization. These CPPILs possess large specific surface area, plentiful micro/meso-porosity, and abundant ionic active sites. Consequently, CPPILs can serve as highly efficient heterogeneous catalysts for asymmetric epoxidation of styrene. Excellent catalytic performance with yield of epoxides and enantiomeric excess value comparable with or even higher than that of the homogeneous system was achieved. The high catalytic activity can be further expanded to various substrates of unfunctionalized olefins. These catalysts are stable and could be recycled at least five times without significant loss of reactivity and enantioselectivity.