Stable Chiral Ruthenium Complex Catalyst Based on Polymer Ionic Liquid for Asymmetric Transfer Hydrogenation of Aliphatic Ketones in Water

The development of heterogeneous chiral metal catalysts which maintain efficiency and stability in the aqueous phase is significant for applications in many industries. On the basis of a series of polymer ionic liquids (PILs) that contain coexisting Cl– and [NTf2]− anions, the stable heterogeneous chiral Ru catalysts with controllable hydrophobic surface were successfully prepared. PIL-functionalized structure ensured that the catalysts could be well dispersed as micelles in a pure water medium, and enhance the adsorption of organic substrate, thereby significantly improving the reactivity in water. The catalyst successfully catalyzed the asymmetric hydrogenation transfer reaction of alkyl ketones in water with high activity and selectivity. Importantly, the catalyst can be easily and efficiently recovered and recycled at least nine times without significant loss of activity and enantioselectivity. This formation of a catalyst from PIL could provide an important approach to the design of environmentally friendly catalysts and the development of green reactions in the water.