Chiral Phosphoric Acid Catalyzed Highly Enantioselective Friedel–Crafts Alkylation Reaction of C3-Substituted Indoles to β,γ-Unsaturated α-Ketimino Esters

Abstract

A highly enantioselective C2 Friedel-Crafts alkylation reaction of 3-substituted indoles to β,γ-unsaturated α-ketimino esters has been developed. This reaction was efficiently catalyzed by a chiral phosphoric acid catalyst. The corresponding C2-substituted indole derivatives, bearing an α-ketimino ester motif, were obtained in moderate to high yields (up to 93%) and with high enantioselectivities (up to >99% ee).