Enantioselective arylation of 2-methylacetoacetates catalyzed by CuI/trans-4-hydroxy-L-proline at low reaction temperatures

CuI/trans-4-hydroxy-l-proline-catalyzed coupling reaction of 2-iodotrifluoroacetanilides with 2-methylacetoacetates took place at -45 degrees C to create alpha-aryl all-carbon quaternary centers enantioselectively. Up to 93% ee was achieved when tert-butyl ester was used. The combination of ligand, ortho substituent (participation of NHCOCF3), and solvent effects was shown to account for these unprecedentedly mild reaction conditions.