Mechanistic insight into rhodium-catalyzed intramolecular enantioselective C–H silylation with dihydrosilanes

Although enantioselective C−H silylation has progressed rapidly in recent years, little mechanistic information on these reactions is available, especially for C−H silylation with dihydrosilanes toward silicon-stereogenic silanes. Here, we report a thorough combined experimental and theoretical mechanistic study on the rhodium-/Josiphos-catalyzed intramolecular enantioselective C−H silylation of dihydrosilanes for the construction of silicon-stereogenic centers. A rhodium silyl dihydride complex was identified as the resting state in the catalytic cycle, which was generated via a facile silyl metal migration process. This key resting state was also synthesized and characterized by X-ray crystallographic analysis. Density functional theory calculations were conducted to elucidate the full picture of the mechanism and shed light on the origin of the observed enantioselectivity and the racemization process in the reaction. With the understanding of the mechanism, both enantioenriched tetraorganosilanes and monohydrosilanes could be synthesized with decent yields and enantiomeric excess, respectively.