Copper-Catalyzed Asymmetric Three-Component Borylstannation: Enantioselective Formation of C-Sn Bond

In summary, a first copper-catalyzed synthesis of alpha-aryl-beta-borylstannane compounds was accomplished through three-component borylstannation of aryl-substituted alkenes. In the exploration of an asymmetric variant, chiral sulfinylphosphine ligands proved advantageous in controlling stereochemistry of B-Cu addition and in promoting transmetalation of enantioenriched alkyl-Cu species. The stereochemical outcome supported a sequential syn-borylcupration and configuration-retentive transmetalation mechanism. Moreover, alpha-chiral beta-borylstannanes were easily transformed into a diverse array of secondary alkylstannanes and triarylethane with high enantiomeric purity. The applications of chiral sulfinylphosphine ligands to other tandem Cu-B addition reactions are currently under investigation in our group.