Enantioselective Friedel-Crafts Alkylation of Indoles with Trifluoroethylidene Malonates by Copper-Bis(oxazoline) Complexes: Construction of Trifluoromethyl-Substituted Stereogenic Tertiary Carbon Center

An enantioselective alkylation of indoles with trifluoroethylidene malonates catalyzed by copper(II) bis (oxazoline) complexes has been developed. The expected adducts with a stereogenic tertiary carbon center bearing a trifluoromethyl group were obtained in excellent yields (up to 99%) and ee values (up to 96% ee). The synthetic utility of this asymmetric catalytic reaction was demonstrated by the preparation of beta-CF3-tryptophan and 4-CF3-beta-carboline in high ee.