Enantioselective Hydrosilylation of Ketones Catalyzed by a Readily Accessible N‐Heterocyclic Carbene–Ir Complex at Room Temperature

Abstract

AbstractA series of functionalized azolium compounds were synthesized from chiral α‐amino acid derivatives such as β‐amino alcohols. Reaction of hydroxy‐amide‐functionalized azolium salts thus obtained with Ag2O afforded N‐heterocyclic carbene‐Ag (NHC–Ag) complexes. Subsequent treatment of the resulting silver compound with [IrCl(cod)]2 yielded monodentate IrCl(cod)(NHC), which was stable in air. The NHC–Ir complex facilitated efficient asymmetric hydrosilylation of ketones using (EtO)2MeSiH under ambient conditions. A chiral ligand containing an isobutyl stereodirecting group was found to be the best ligand for the functionalized NHC–Ir complexes that were examined. A linear relationship was found between the catalyst ee and the product ee. The hydroxy functional group on the NHC ligand side‐arm not only induced stereocontrol but also enhanced the reaction rate.