AgAsF6/Sm(OTf)(3) Promoted Reversal of Enantioselectivity for the Asymmetric Friedel-Crafts Alkylations of Indoles with beta,gamma-Unsaturated alpha-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 %).