Copper(I)-Catalyzed Regio- and Chemoselective Single and Double Addition of Nucleophilic Silicon to Propargylic Chlorides and Phosphates

Copper(I)-catalyzed propargylic substitution of linear precursors with (Me₂PhSi)₂Zn predominantly yields the γ isomer independent of the propargylic leaving group. The thus formed allenylic silane reacts regioselectively with another equivalent of (Me₂PhSi)₂Zn, yielding a bifunctional building block with allylic and vinylic silicon groups. The reaction rates of both steps are well-balanced for chloride (γ:α ≥ 99:1) where the propargylic displacement occurs quantitatively prior to the addition step. Substitutions of α-branched propargylic phosphates are also reported