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

•Highly effective Rh-catalyzed ATH reaction in water was investigated.•The synthesis of ligands is concise and practical.•High substrate to catalyst (S/C) ratio of 500 is achieved.•Only 1.5 equiv. of hydride source HCO2Na is used.•The reaction condition is mild without addition of any surfactants.

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 1.5 equiv. of HCO2Na. The procedure presented is simple and makes this method suitable for practical use.

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