Facile Development of Chiral Alkenylboranes from Chiral Diynes for Asymmetric Hydrogenation of Silyl Enol Ethers

A facile development of chiral alkenylboranes by the hydroboration of chiral diynes with Piers borane was successfully achieved for the first time. With the combination of the in situ generated chiral alkenylboranes and tri-tert-butylphosphine as frustrated Lewis pair catalysts, the metal-free asymmetric hydrogenation of silyl enol ethers was realized to furnish a wide range of optically active secondary alcohols in high yields and up to 99% ee.