Asymmetric Catalysis with Substitutionally Labile yet Stereochemically Stable Chiral-at-Metal Iridium(III) Complex

Abstract

A metal-coordination-based high performance asymmetric catalyst utilizing metal centrochirality as the sole element of chirality is reported. The introduced substitutionally labile chiral-at-metal octahedral iridium­(III) complex exclusively bears achiral ligands and effectively catalyzes the enantioselective Friedel–Crafts addition of indoles to α,β-unsaturated 2-acyl imidazoles (19 examples) with high yields (75%–99%) and high enantioselectivities (90–98% <i>ee</i>) at low catalyst loadings (0.25–2 mol %). Counterintuitively, despite its substitutional lability, which is mechanistically required for coordination to the 2-acyl imidazole substrate, the metal-centered chirality is maintained throughout the catalysis. This novel class of reactive chiral-at-metal complexes will likely be of high value for a large variety of asymmetric transformations