Synthesis of Trifluoromethanesulfanylbenzofulvenes via a Cascade Electrophilic Cyclization under Mild Conditions

The introduction of the (trifluoromethyl) thio moiety into organic molecules has aroused comprehensive interest recently. We describe herein an efficient and chemoselective synthesis of trifluoromethanesulfanylbenzofulvenes through BiCl3- or TsOH-promoted cascade electrophilic cyclization reactions. The presence of the trifluoromethanesulfanyl cation (CF3S+) would facilitate the electrophilic ring closure and nucleophilic attack of chloride or TsOH. This reaction provides a concise method for the synthesis of chlorine-or tosyloxy-substituted trifluoromethanesulfanylbenzofulvenes in good to excellent yields.