Z‑Selective Hydrostannylation of Terminal and Internal C–C Triple Bonds Initiated by the Trityl Cation

A metal-free method for the anti-addition of n-Bu3SnH across terminal and internal alkynes, including related α,β-unsaturated carboxyl compounds, is reported. The reaction is initiated by the trityl salt [Ph3C]+[B­(C6F5)4]− and proceeds through β-tin-stabilized vinyl cations. Their reduction by hydride transfer from n-Bu3SnH explains the high Z-selectivity in the formation of the vinyl stannanes.