a On 0.1 mmol scale. Yields were determined by 1 H NMR spectroscopy of the crude reaction mixture, using 1,1,2,2-tetrachloroethane as the internal standard, DCE: 1,2-dichloroethane. b Yield and enantioselectivity of isolated product (0.2 mmol scale, 2 M) in parentheses. c NP: no desired product observed, ND: not determined. d Et3SiH and TfOH were mixed and stirred for 5 min before adding to the reaction mixture.