Imidazolium ion tethered TsDPENs as efficient water-soluble ligands for rhodium catalyzed asymmetric transfer hydrogenation of aromatic ketones

Abstract

An imidazolium ion tethered TsDPEN has been synthesized readily and used as a water-soluble ligand for [Cp*RhCl2]2 catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones in water. This process provided the secondary alcohols in moderate to excellent conversions (up to 100%) with high enantioselectivities (up to 98% ee) under mild reaction conditions without adding any surfactants. The catalytic system is highly effective with the substrate to catalyst (S/C) ratio of 500 and low hydride donor loading of 1.5equiv. of HCO2Na. The procedure presented is simple and makes this method suitable for practical use.