AgAsF6/Sm(OTf)3 promoted reversal of enantioselectivity for the asymmetric Friedel-Crafts alkylations of indoles with beta,gamma-unsaturated alpha-ketoesters.

ABSTRACT

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 1a and 1b 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 %).