Density functional theory calculations have been performed to investigate the copper-catalyzed borocyanation of 1-aryl-1,3-butadienes. The computations show that the regio-and enantioselectivity is determined by the borocupration step. The π-electron withdrawing aryl group at the C1 atom makes the C4 atom more electrophilic than the other carbon atoms, which together with the steric repulsion around the forming C--B bond, results in the experimentally observed exclusive 4,3-regioselectivity. The origins of the enantioselectivity were attributed to the steric effect and π-π stacking interaction between the butadiene moiety and the ligand.