Cu(I)‐Catalyzed Enantioselective γ‐Boryl Substitution of Trifluoromethyl‐ and Silyl‐Substituted Alkenes

Abstract

Asymmetric γ‐boryl substitution of trifluoromethyl‐ and silyl‐substituted alkenes has been investigated. A variety of substrates were reacted with bis(pinacolato)diboron in the presence of a copper(I) salt and optically active C₁ symmetric QuinoxP*‐type bisphosphine ligand as the catalyst. The optically active silyl‐substituted gem‐difluoroallylboronates products bearing a stereogenic C−B bond, which have never been synthesized before, were obtained in good yield with high enantioselectivity (up to 83 % and up to 86 % ee, respectively). The resulting allylboron compounds undergo a stereoselective allylboration with a range of aldehydes to afford chiral silyl‐ and difluoromethylene‐containing homoallylic alcohols without significant loss in their enantiomeric purity. The resulting silyl groups in the derivatives can serve as cross‐coupling sites, allowing further transformation into structurally complex fluorinated chiral molecules.