Borane-Catalyzed Intermolecular Aryl Transfer between Hydrosilanes: Shifting the Equilibrium by Removal of a Gaseous Hydrosilane

The preparation of organosilanes is indeed far from trivial, despite their vast application. Herein, we report a straightforward and general hydrosilane iterative evolution system for the on-demand synthesis of heteroleptic-substituted hydrosilanes. A series of previously difficult-to-prepare hydrosilanes with two or three diverse substituents were readily obtained. Our process is achieved just by using a catalytic amount of BH₃ to initiate a selective hydrosilane redistribution process via aryl group migration. Thus, our work represents sporadic examples of the application of hydrosilane redistribution procedures for synthetic applications, whereas hydrosilane redistribution is often found as an unwanted side reaction; its synthetic value has rarely been explored. Furthermore, an unprecedented and challenging cross-redistribution of aryl hydrosilanes with alkyl hydrosilanes is achieved. Mechanistic studies and density functional theory (DFT) calculations revealed that this process was attained via a BH₃-catalyzed C-Si bond cleavage and selective intermolecular aryl group migration from aryl hydrosilanes to alkyl hydrosilanes.