Hydrogenation of Quinolines Using a Recyclable Phosphine‐Free Chiral Cationic Ruthenium Catalyst: Enhancement of Catalyst Stability and Selectivity in an Ionic Liquid

Abstract

Liquid assets: The catalyst (S,S)-1 exhibits an unprecedented reactivity and excellent enantioselectivity for the title reaction when it is carried out in neat ionic liquid (see scheme; BMIM=1-n-butyl-3-methylimidazolium, Tf=trifluoromethanesulfonyl, Ts=4-toluenesulfonyl). The ionic liquid facilitates the catalyst recycling and enhances its stability and selectivity.