Facile Preparation of Indoles and 1,2‐Benzothiazine 1,1‐Dioxides: Nucleophilic Addition of Sulfonamides to Bromoacetylenes and Subsequent Palladium‐Catalyzed Cyclization

Bromine as a double agent: The bromine atom in 1-bromo-1-alkynes works as an electron-withdrawing group to effect the nucleophilic addition of sulfonamides. It again plays a pivotal role in the palladium-catalyzed cyclization of the resultant (Z)-2-(sulfonylamino)-1-bromoalkenes into nitrogen heterocycles (see scheme).