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This study aims to propose a simple procedure for the development of enantioselective hydrosilylation of a ketone using catalytic amounts of [Ir(cod)2]BF4 and chiral azolium salt. Previously, catalytic asymmetric hydrosilylation reactions have used well-defined metal-N-heterocyclic carbene (NHC) complexes. The proposed method offers an important advantage of avoiding preparation of NHC-metal species. Several reaction parameters including the amount of reductant, solvent, catalyst loading and ligand structure were evaluated. In addition, the investigation of the reaction progress as a function of time revealed that an iridium species, which was generated after 5 h of reaction time, catalyzed the stereoselective reduction with almost perfect facial selection of the ketone. An attempt to obtain a catalytic active species from the reaction of [Ir(cod)2]BF4 and chiral azolium salt has been made. The newly obtained iridium species promoted the hydrosilylation of a ketone with high yield and enantioselectivity.

Enantioselective reduction of ketones with (EtO) 2 MeSiH catalyzed by an in-situ generated N -heterocyclic carbene (NHC) Ir complex at room temperature has been developed. A series of benzimidazolium salts were synthesized and screened in the asymmetric hydrosilylation reaction. As a result, propiophenone was efficiently reduced by the combined catalytic system of [IrCl(cod)] 2 and NHC–Ag complex derived from N -(1-naphthalenylmethyl)-substituted benzimidazolium salt L12 , affording the corresponding alcohol in 92% yield and with 92% ee. Moreover, the evaluation of an Ir catalyst precursor showed that cationic [Ir(cod) 2 ]BF 4 complex could be used. Furthermore, the introduction of a chiral hydroxyamide side arm into the benzimidazolium salt was critical for the successful design of the NHC ligand.