Enantioselective Hydrogenation with Racemic and Enantiopure Binap in the Presence of a Chiral Ionic Liquid

摘要

There is growing interest in the use of chiral ionic liquids (cILs) in asymmetric catalysis as the reaction media or as an additive. Whereas chiral solvents have shown limited success in enantioselective synthesis the use of cILs have recently resulted in generating significant enantioselectivity in organocatalysis, heterogeneous catalysis, and transition-metal-catalyzed reactions. As part of our interest in this area, we investigated the Rh-catalyzed homogeneous hydrogenation in amino-acid-derived cILs. Product enantio-selectivities up to 69% ee were obtained by using rhodium catalysts derived from tropoisomeric phosphine ligands in combination with cILs as the only source of fixed chirality.