Synthesis of functionalized hydrosilanes via titanium-catalyzed hydroboration and hydrogenation of C(sp³)-Si bonds in silacyclobutanes.

Abstract

The design and synthesis of molecules featuring both boron and silicon moieties hold significant promise for delivering unique reactivity patterns and material properties. Herein, a titanium-catalyzed selective hydroboration of the C(sp³)-Si bonds in silacyclobutanes for the synthesis of boryl-functionalized hydrosilanes is developed. Our protocol accommodates a broad range of structurally distinct silacyclobutanes, affording a diverse library of boryl-functionalized hydrosilanes (R₂B~link~Si-H). The free Si-H and boryl functional groups allow for their seamless integration into synthetic chemistry and many other research areas. The facile synthesis of sila-substituted drug molecules via our strategy is also demonstrated. Furthermore, our methodology is successfully extended to the hydrogenation of the C(sp³)-Si bond using H₂ gas, offering a general route to synthesize a broad spectrum of heteroleptic-substituted hydrosilanes, including their deuterated derivatives. Mechanistic investigations, complemented by DFT calculations, reveal an unusual two-electron process at the titanium metal center. The essence of the selective activation of C(sp³)-Si bonds over C(sp²)-Si in silacyclobutanes by titanium catalyst is elucidated.