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 nucleophilicaddition 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).