Stereodivergent Synthesis of β-Heteroatom-Substituted Vinyl­silanes by Sequential Silylzincation–Copper(I)-Mediated Electrophilic­ Substitution

Sulfur-, oxygen-, and phosphorus-substituted terminal alkynes undergo regio- and stereoselective silylzincation by reaction with (Me₂PhSi)₂Zn, (Me₃Si)₃SiH/Et₂Zn or [(Me₃Si)₃Si]₂Zn/Et₂Zn. The addition across the C–C triple bond always occurs with β-regioselectivity but the stereoselectivity is tunable: (Me₂PhSi)₂Zn for cis and (Me₃Si)₃SiH/­Et₂Zn or [(Me₃Si)₃Si]₂Zn/Et₂Zn for trans. The procedures making use of the zinc reagents (Me₂PhSi)₂Zn and [(Me₃Si)₃Si]₂Zn can be combined in one-pot with a subsequent stereoretentive copper(I)-mediated electrophilic substitution of the intermediate C(sp²)–Zn bond. These stereodivergent protocols offer a regio- and stereoselective access to trisubstituted vinylsilanes decorated with sulfur-, oxygen-, and phosphorus substituents with either double-bond geometry.