Multiligand-enabled, copper-catalyzed Hiyama coupling of arylsilanes with unactivated secondary alkyl halides: reaction development and mechanistic insights.

Construction of carbon-carbon bonds is the cornerstone in organic synthesis, and Hiyama coupling is the representative synthetic approach for realizing linkages between silyl compounds and organohalides. In previous literature, such couplings are mainly utilized for the bond formations of arylsilanes with sp2-aryl halides, yet Hiyama couplings with sp3-hybridized alkyl halides still remain scarce. Copper catalysis has recently been scrutinized in several important transformations of unactivated secondary alkyl halides, whereas their conversions with organosilanes are far less developed. Herein, we leverage a multiligand catalysis to offer a solution for efficient copper-catalyzed Hiyama couplings with such unactivated alkyl halides. Detailed mechanistic studies disclosed that the incorporation of an NHC ligand with a phenanthroline-copper system would dramatically enhance the reaction efficiency, where the copper species with NHC and phenanthroline-type ligands were most likely to account for the C(sp2)-Si bond activation and C(sp2)-C(sp3) bond formation process, respectively.