Transition-metal- and solvent-free regioselective hydrosilylation of alkenes and allenes enabled by catalytic sodium tert-butoxide

Abstract

β-Selective hydrosilylation products of alkenes are of industrial importance, and the development of methods with Markovnikov selectivity is a growing area of research and still relatively rare. Herein, we have developed a convenient, transition-metal- and solvent-free method involving the alkali metal Lewis base NaO^tBu as a catalyst and diphenyl silane (Ph₂SiH₂) as a silane reagent for the regioselective Markovnikov hydrosilylation of vinyl arenes and aliphatic alkenes in high yields with good functional group compatibility. Importantly, the hydrosilylation of allenes with Ph₂SiH₂ proceeds in a regioselective manner to afford (E)-allylsilane products. The utilization of the Earth-abundant sodium cation as a catalyst for hydrosilylation reactions appears to be unprecedented. We postulated the formation of a pentacoordinate silicon “ate” intermediate as evidenced by IR and mass spectrometry. Radical clock and trapping experiments support a radical mediated catalytic process.