A unique binary chiral phosphoric acid 1a/MgF2 catalyst that enables effective catalysis of asymmetric Friedel−Craftsreactions 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.
AgAsF<sub>6</sub>/Sm(OTf)<sub>3</sub> Promoted Reversal of Enantioselectivity for the Asymmetric Friedel−Crafts Alkylations of Indoles with β,γ-Unsaturated α-Ketoesters
The first example of central metal controlled reversal of enantioselectivity in asymmetric Friedel-Crafts alkylation of Indoles and beta,gamma-unsaturated alpha-ketoesters has been developed. Using the same chiral starting material derived N,N'-dioxides 1 a and 1 b as ligands, various indole esters 4 were obtained In good to excellent yields and enantioselectivities. The reaction also featured mild reaction conditions and remarkably low catalyst loading (down to 0.01 mol %).