Asymmetric binary-acid catalysis with chiral phosphoric acid and MgF(2): catalytic enantioselective Friedel-Crafts reactions of beta,gamma-unsaturated alpha-ketoesters

A unique binary chiral phosphoric acid 1a/MgF2 catalyst that enables effective catalysis of asymmetric Friedel−Crafts reactions of phenols with up to 82% yield and >99% ee is presented. A dramatic synergistic effect has been observed in the combinations of two types of acids, wherein a highly active binary-acid catalyst can be generated from two individually inert acids.