Mechanistic Insights into Rh-Catalyzed Asymmetric Si–H/O–H Dehydrocoupling: Unraveling the Origins of Reactivity and Enantioselectivity in Si-Stereogenic Silanes Synthesis

Through combined kinetic studies and DFT calculations, we elucidate the mechanistic origins of the reactivity and enantioselectivity in rhodium-catalyzed asymmetric dehydrogenative coupling between dihydrosilanes and alcohols. An S_N2-type oxidative proton-hydride transfer (S_N2-OPHT) pathway was identified as the dominant mechanism, exhibiting a lower energy barrier compared to conventional oxidative addition and σ-bond metathesis pathways. Crucially, the second Si–H bond in dihydrosilanes was revealed to play a unique role, as evidenced by the complete suppression of the reactivity in monohydrosilane control experiments. Distortion/interaction analysis further demonstrated that the high enantioselectivity arises from differential steric distortions between competing transition states. These findings not only rationalize the stereochemical outcomes in Si-stereogenic silane synthesis but also establish a framework for designing enantioselective transformations through precise transition state modulation.