Enantioselective Addition Reaction of Azlactones with Styrene Derivatives Catalyzed by Strong Chiral BrOnsted Acids

An enantioselective intermolecular addition reaction of azlactones, as carbon nucleophiles, with styrene derivatives, as simple olefins, was demonstrated using a newly developed chiral BrOnsted acid catalyst, namely, F10BINOL-derived N-triflyl phosphoramide. Addition products having vicinal tetrasubstituted carbon centers, one of which is an all-carbon quaternary stereogenic center, were formed in good yields with moderate to high stereoselectivities. Extremely high acidity of the new chiral BrOnsted acid was confirmed by its calculated pK(a) value based on DFT studies and is the key to accomplishing not only high catalytic activity but also efficient stereocontrol in the intermolecular addition.