Synthesis of C3-Alkynyl Pyrroloindolines via Intermolecular Cascade Dearomatization/1,2-Migration of Tryptamine Derivatives with Alkynyliodonium Salts.

We report a straightforward and efficient method for the construction of structurally diverse C3-alkynyl pyrroloindolines, enabled by an intermolecular cascade dearomatization/1,2-migration of tryptamine derivatives with alkynyliodonium salts. This method features readily accessible starting materials, a broad substrate scope, and straightforward scalability. A series of C3-alkynyl-functionalized pyrroloindolines were obtained in up to an 88% yield under mild reaction conditions. Furthermore, the alkynyl group can undergo diverse downstream transformations. Mechanistic studies revealed that the reaction proceeds via initial nucleophilic attack at the C3 position of indole rather than direct involvement of amine nitrogen.