Ir-Catalyzed Enantioselective, Intramolecular Silylation of Methyl C-H Bonds.

We report highly enantioselective intramolecular, silylations of unactivated, primary C(sp3)-H bonds. The reactions form dihydrobenzosiloles in high yields with excellent enantioselectivities by functionalization of enantiotopic methyl groups under mild conditions. The reaction is catalyzed by an iridium complex generated from [Ir(COD)OMe]2 and chiral dinitrogen ligands that we recently disclosed. The C-Si bonds in the enantioenriched dihydrobenzosiloles were further transformed to C-Cl, C-Br, C-I, and C-O bonds in final products. The potential of this reaction was illustrated by sequential C(sp3)-H and C(sp2)-H silylations and functionalizations, as well as diastereoselective C-H silylations of a chiral, natural-product derivative containing multiple types of C-H bonds. Preliminary mechanistic studies suggest that C-H cleavage is the rate-determining step.