King of the ring: S‐(trifluoromethyl)benzo[b]thiophenium salts 1, as analogues of Yagupolskii–Umemoto type reagents, were synthesized by novel triflicacidcatalyzedintramolecularcyclization of ortho‐ethynylaryltrifluoromethylsulfanes 2. 1 j is especially useful for the electrophilic trifluoromethylation of β‐ketoesters and dicyanoalkylidenes.