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