Heterogeneous Enantioselective Hydrogenation of Ketones by 2-Amino-2′-hydroxy-1,1′-binaphthyl-Modified CeO2-Supported Ir Nanoclusters

Abstract

Modification of supported noble metals with chiral modifiers is a promising strategy for the design of effective heterogeneous chiral catalysts. The chiral compounds are generally introduced on the surface of noble metals, often leading to low enantioselectivity and to low activity. Herein, a unique heterogeneous chiral catalyst where a chiral modifier is introduced at the interface between the metal cluster and the support is presented. Modification of CeO2-supported Ir nanoclusters with 2-amino-2′-hydroxy-1,1′-binaphthyl (NOBIN) as a chiral modifier provided a heterogeneous chiral catalyst where NOBIN is introduced at the interface between Ir nanoclusters and the CeO2 support. The heterogeneous chiral catalyst enabled the asymmetric hydrogenation of acetophenone to provide 1-phenylethanol with moderate enantiomeric excess (ee) (up to 53%). The catalyst characterizations showed that about 1 nm Ir metal nanoclusters are formed on CeO2, and density functional theory calculations presented that NOBIN is adsorbed onto Ir nanoclusters and CeO2 at the NH2 and OH groups, respectively, constructing the asymmetric reaction field among NOBIN, Ir nanoclusters, and CeO2.