Efficient Access to Extended Yagupolskii–Umemoto‐Type Reagents: Triflic Acid Catalyzed Intramolecular Cyclization of ortho‐Ethynylaryltrifluoromethylsulfanes

King of the ring: S-(trifluoromethyl)benzobthiophenium salts 1, as analogues of Yagupolskii–Umemoto type reagents, were synthesized by novel triflic acid catalyzed intramolecular cyclization of ortho-ethynylaryltrifluoromethylsulfanes 2. 1 j is especially useful for the electrophilic trifluoromethylation of β-ketoesters and dicyanoalkylidenes.