Catalytic Asymmetric Allenylation: Regulation of the Equilibrium Between Propargyl- and Allenylstannanes During the Catalytic Process.

Achiral substrates 1 and 2 can be regioselectively converted into chiral allenyl alcohols 3 through the title reaction [Eq. (1)] with the synergetic reagent iPrSBEt2 and a chiral TiIV catalyst. The dramatic regioselectivity originates from the regulation of the equilibrium between propargyl- and allenylstannanes during the catalytic process.