Stereochemical Control via Chirality Pairing: Stereodivergent Syntheses of Enantioenriched Homoallylic Alcohols

Abstract

We report herein the development of stereodivergent syntheses of enantioenriched homoallylic alcohols using chiral nonracemic a-CH 2 Bpin-substituted crotylboronate.C hiral phosphoric acid (S)-A-catalyzed asymmetric allyl addition with the reagent gave Z-anti-homoallylic alcohols with excellent enantioselectivities and Z-selectivities.W hen the enantiomeric acid catalyst (R)-A was utilized,t he stereoselectivity was completely reversed and E-anti-homoallylic alcohols were obtained with high E-selectivities and excellent enantioselectivities.B ypairing the chirality of the boron reagent with the catalyst, two complementary stereoisomers of chiral homoallylic alcohols can be obtained selectively from the same boron reagent. DFT computational studies were conducted to probe the origins of the observed stereoselectivity.T hese reactions generate highly enantioenriched homoallylic alcohol products that are valuable for rapid construction of polyketide structural frameworks.