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 (Me 2 PhSi) 2 Zn, (Me 3 Si) 3 SiH/Et 2 Zn or [(Me 3 Si) 3 Si] 2 Zn/Et 2 Zn. The addition across the C–C triple bond always occurs with β-regioselectivity but the stereoselectivity is tunable: (Me 2 PhSi) 2 Zn for cis and (Me 3 Si) 3 SiH/­Et 2 Zn or [(Me 3 Si) 3 Si] 2 Zn/Et 2 Zn for trans . The procedures making use of the zinc reagents (Me 2 PhSi) 2 Zn and [(Me 3 Si) 3 Si] 2 Zn can be combined in one-pot with a subsequent stereoretentive copper(I)-mediated electrophilic substitution of the intermediate C(sp 2 )–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.