Synthesis of 2-Acyltryptamines through an Unexpected Brønsted Acid Catalyzed Formal 1,5-Migration of Functional Group from Indole-Tethered Ynamides

Herein, we have developed a Brønsted acid catalyzed 1,5-migration of functional groups from indole-tethered ynamides to prepare a variety of 2-acyltryptamines in good to excellent yields with high site-selectivity at the C2-position of indoles. Mechanistic studies revealed that the reaction underwent an intramolecular cyclization, 1,2-migration of the vinyl group, and C–N bond cleavage by hydrolysis in a one pot. The reaction features broad substrate scope, good functional group compatibility, 1,5-migration of functional groups, Csp–N bond cleavage to form Csp2–Csp2 bond, and diverse 2-acyltryptamine scaffolds.