Asymmetric Radical Oxyboration of β-Substituted Styrenes via Late-Stage Stereomutation.

Herein, we report an unprecedented copper-catalyzed highly enantio- and diastereoselective radical oxyboration of β-substituted styrenes. The lynchpin of success is ascribed to the development of a late-stage stereomutation strategy, which enables enantioenriched cis-isomers among a couple of early-generated diastereomers to be converted into trans-isomer counterparts, thus fulfilling high diastereocontrol; while the degree of enantio-differentiation is determined by the borocupration process of the C=C bond. This reaction provides an efficient protocol to access enantioenriched trans-1,2- dioxygenation products. The value of this method has further been highlighted in a diversity of follow-up stereospecific transformations and further modifying complex molecules.