Brønsted Acid-Catalyzed C3-Trifluoroalkylation of Carbazoles with Trifluoromethyl-Substituted 3-Indolymethanols

A catalytic C3-trifluoroalkylation of unprotected carbazoles with trifluoromethyl-substituted 3-indolylmethanols has been developed using DL-10-camphorsulfonic acid as the catalyst. This protocol provides an efficient, metal-free methodology for easily synthesizing trifluoromethylated 3-carbazolyl-3'-indolylmethanes with moderate to excellent yields and remarkable regioselectivity under mild reaction conditions. To demonstrate the applicability of the C3-trifluoroalkylation reaction, the gram-scale preparation and synthetic transformation of trifluoromethylated carbazole were shown.