Borane-Catalyzed Intermolecular\nAryl Transfer between\nHydrosilanes: Shifting the Equilibrium by Removal of a Gaseous Hydrosilane

The preparation of organosilanes is indeed far from trivial,\ndespite\ntheir vast application. Herein, we report a straightforward and general\nhydrosilane iterative evolution system for the on-demand synthesis\nof heteroleptic-substituted hydrosilanes. A series of previously difficult-to-prepare\nhydrosilanes with two or three diverse substituents were readily obtained.\nOur process is achieved just by using a catalytic amount of BH<sub>3</sub> to initiate a selective hydrosilane redistribution process\nvia aryl group migration. Thus, our work represents sporadic examples\nof the application of hydrosilane redistribution procedures for synthetic\napplications, whereas hydrosilane redistribution is often found as\nan unwanted side reaction; its synthetic value has rarely been explored.\nFurthermore, an unprecedented and challenging cross-redistribution\nof aryl hydrosilanes with alkyl hydrosilanes is achieved. Mechanistic\nstudies and density functional theory (DFT) calculations revealed\nthat this process was attained via a BH<sub>3</sub>-catalyzed C–Si\nbond cleavage and selective intermolecular aryl group migration from\naryl hydrosilanes to alkyl hydrosilanes.