Enantioselective turnover in glyoxylate-ene reactions catalyzed by chiral copper complexes

The catalytic, enantioselective carbonyl-ene reaction of ethyl glyoxylate with α-methylstyrene and 4-halo-α-methylstyrene has been investigated in the presence of copper triflate–bisoxazoline complexes. The reaction proceeded smoothly to give γ,δ-unsaturated-α-hydroxy esters in moderate to good yields and with excellent enantioselectivity (up to 100% ee). A hypothesis has been provided to explain the reversal of enantioselectivity in the reaction.