Asymmetric hydrogenation of 1,1-diarylethylenes and benzophenones through a relay strategy

Abstract

AbstractHomogenous transition-metal catalysts bearing a chiral ligand are widely used for asymmetric hydrogenation of unsaturated compounds such as olefins and ketones, providing efficient concise access to products with chiral carbon centers. However, distinguishing thereandsiprochiral faces of a double bond bearing two substituents that are sterically and electronically similar is challenging for these catalysts. Herein, we report a relay strategy for constructing compounds with a chiralgem-diaryl carbon center by means of a combination of selective arene exchange between 1,1-diarylethylenes or benzophenones with (naphthalene)Cr(CO)3and subsequent asymmetric hydrogenation. During the hydrogenation, the Cr(CO)3unit facilitate differentiation of the two prochiral faces of the substrate double bond via formation of a three-dimensional complex with one of the aromatic rings by selective arene exchange. Density functional theory calculations reveal that during the hydrogenation, chromium coordination affected π–π stacking of the substrate and the catalyst ligand, leading to differentiation of the prochiral faces.