Copper-Catalyzed Formal Dihydrosilylation of Terminal Alkynes: A C(sp)-H Silylation-Hydrosilylation-Hydrogenation Sequence

Copper-catalyzed regioselective double anti-Markovnikov hydrosilylation of terminal alkynes has been developed by employing a copper catalyst generated from readily available CuOAc and 1,3-bis(diphenylphosphino)propane (dppp). A wide range of alkyl- and arylacetylenes undergo this dihydrosilylation reaction to afford gem-disilylalkanes in high isolated yields with high selectivity. Mechanistic studies, including identification and isolation of reactive intermediates, control experiments, deuterium-labeling reactions, and stoichiometric organometallic reactions, reveal that this copper-catalyzed formal dihydrosilylation of terminal alkynes proceeds through a reaction sequence combining C(sp)-H silylation of alkynes to form alkynylsilanes, hydrosilylation of alkynylsilanes to provide gem-disilylalkenes, and hydrogenation of gem-disilylalkenes to afford gem-disilylalkanes. Both copper hydride and copper acetylide species are key active intermediates for this copper-catalyzed dihydrosilylation process.