Copper-Catalyzed Asymmetric 1,4-Hydroboration of Coumarins with Pinacolborane: Asymmetric Synthesis of Dihydrocoumarins

An efficient asymmetric addition of pinacolborane to 4-substituted coumarins proceeded with high enantioselectivity in the presence of a copper(I)-QuinoxP complex as a catalyst to produce the corresponding 1,4-hydroboration products Treatment of the intermediates with electrophiles, without isolation, resulted in enantioenriched dihydrocoumarins The utility of this protocol was demonstrated in the formal synthesis of biologically active molecules.