Ligand Relay Cobalt Catalysis for Vicinal Si,O-Alkanes from Terminal Alkynes

Construction of valuable vicinal Si,O-alkanes, which
exhibit potential
utility in pharmaceuticals and materials science, has yet to be restricted
to prefunctionalized reactants. Plenty of efforts have been made,
using alkenes as nonprefunctionalized starting materials. Despite
that, methodology starting from easily accessible alkynes has been
rarely developed, and vicinal Si,O-alkanes containing Si–H
have seldom been explored. Here, we report one-pot two-step cobalt-catalyzed
sequential hydrosilylation/hydroxylation of terminal alkynes with
commercially available TEMPO and diphenylsilane via ligand relay catalysis,
featuring low catalyst loading (1 mol %), mild conditions, and broad
substrate scope. The successful execution of the double hydrofunctionalization
protocol ensures that the vicinal Si,O-alkanes with characterized
Si–H are obtained smoothly in good yields and regioselectivity.
The derivatizations of the Si–H bond are also demonstrated,
delivering silanol, siloxane, and tetra-substituted silane. The possible
mechanism has been proposed based on control experiments and computational
studies.