Reduced graphene oxide supported chiral Ni particles as magnetically reusable and enantioselective catalyst for asymmetric hydrogenation

A reduced graphene oxide (rGO) supported chiral-modified Ni catalyst was synthesized, characterized and employed for asymmetric hydrogenation. The prepared hybrid catalyst could produce each enantiomer with D- or I.-tartaric acid as chiral modifier and exhibited a high TOF (20160 h(-1)) and enantioselectivity (enantiomeric excess, 98.5%) for asymmetric hydrogenation of methyl acetoacetate. The high catalytic activity and enantioselectivity were mainly attributed to the unique properties of the support rGO, as it had a large specific surface area to sustain and stabilize Ni particles and its high charge carrier mobility could enable the readily transfer of electrons in the reaction process. Besides, the catalyst could also gain an enhanced reactant sorption with the support of rGO, thus achieved a greatly catalysis enhancement. The ferromagnetism of Ni made the catalyst easier for separation and reuse. The catalytic and recycling performance of the prepared chiral Ni catalyst demonstrated that rGO was indeed a promising support to improve activity, enantioselectivity and durability of catalysts, and the prepared catalysts were promising reusable heterogeneous catalysts for asymmetric hydrogenation. (C) 2014 Elsevier Ltd. All rights reserved.