Cobalt‐Catalyzed Hydrosilylation of 1,3‐Enynes for the Synthesis of Conjugated Alkenylalkoxysilanes

Comprehensive Summary The hydrosilylation of unfunctionalized 1,3‐enynes with tertiary alkoxysilanes poses significant challenges in regulating regioselectivity and stereoselectivity. In this study, we achieved highly efficient hydrosilylation of unfunctionalized 1,3‐enynes with tertiary alkoxysilanes using a cobalt catalyst supported by a cyclopropane‐fused bisphosphine ligand. Specifically, arylphosphine ligands enabled highly selective cis ‐α‐hydrosilylation of aryl‐substituted 1,3‐enynes (yields up to 95%, regioselectivity > 95 : 5); in contrast, cyclohexylphosphine ligands promoted cis ‐β‐hydrosilylation of alkyl‐substituted 1,3‐enynes (yields up to 99%, regioselectivity > 95:5). This protocol exhibits excellent functional group tolerance and can be readily scaled up to the gram scale, thus enabling the efficient synthesis of a series of structurally novel conjugated alkenylalkoxysilanes. The resulting products can be efficiently converted into organosilicon material precursors, laying a new material foundation for the development of advanced functional organosilicon materials. Mechanistic investigations reveal that the reaction is initiated by substrate activation via a Co(0) active species, proceeds through a two‐electron redox cycle, and accomplishes hydrosilylation via ligand‐to‐ligand hydrogen transfer (LLHT). Specifically, arylphosphine ligands modulate regioselectivity through π‐π stacking interactions with the aryl moiety of enyne substrates, whereas cyclohexylphosphine ligands dictate regioselectivity via abundant van der Waals interactions with alkyl‐substituted 1,3‐enynes, coupled with the higher polarizability of cobalt‐hydrogen bonds.