Chiral Phosphoric Acid-Catalyzed Enantio- and Diastereoselective Allylboration of Aldehydes with ß,γ-Substituted Allylboronates.

The catalytic asymmetric addition of ß,γ-substituted allylboronates to aldehydes has been described. Promoted by 5 mol % chiral phosphoric acid, the reactions were broadly applicable, scalable, and efficient, allowing for the formation of 3,4-anti/syn-homoallylic alcohols bearing adjacent tertiary or quaternary stereogenic centers in a highly enantio- and diastereoselective manner (≤99% ee and dr >20:1). The rigid chairlike transition state involving the chiral phosphoric acid contributed to the highly controlled reaction.