3-Silyl-3-Borylhex-4-Enoate: A Chiral Reagent for Asymmetric Crotylboration of Aldehydes.

A nonracemic 3-silyl-3-borylhex-4-enoate reagent has been developed. Its asymmetric crotylboration of aldehydes provides <i>Z</i>-<i>anti</i>-homoallylic alcohols possessing a trisubstituted vinylsilane in high yields with excellent stereo- and enantioselectivity. Diverse decoration of vinylsilane and ester groups, as well as formation of functionalized THF rings, showcase the potential of the approach in the synthesis of polyketide natural products.