Asymmetric Silaboration of Terminal Allenes Bearing α-Stereogenic Centers:  Stereoselection Based on “Reagent Control”

A highly enantioface-selective silaboration of allenes having stereogenic centers at the alpha-positions of the double bonds has been achieved using a combination of a chiral silylborane (-)-2 and a chiral Pd/(R)-3 catalyst. The chiral reagent system efficiently controlled the stereochemistry of the new stereogenic centers even in the reactions of mismatched combinations. [reaction: see text]