Highly Enantioselective Synthesis of a-Trifluoromethyldi- hydropyrans Using a Chiral Trifluoroethyl-substituted Thiourea Catalyst Derived from Amino Acid

An enantioselective Michael addition of ethyl 4,4,4-trifluoro-3-oxobutanoate to α,β-unsaturated ketone esters using a chiral alkyl-substituted thiourea catalyst is reported. Excellent levels of stereo-induction （up to 98% ee） under mild reaction conditions were obtained to afford the corresponding α-trifluoromethyldihydropyrans.