Accessing Benzoazepine Derivatives via Photoinduced Radical Relay Formal [5 + 2] Reaction of Amide/Alkyne Enabled by Palladium Catalysis
Yu-jia Du, Xia-xin Sheng, Luning Tang, Jia-ming Chen, Guoying Liu, Hao Hu, Sen Yang, Lei Zhu, Ming Chen
Abstract
A novel class of alkyne-tethered amides facilitates an unprecedented photoinduced palladium-catalyzed radical relay formal [5 + 2] reaction. This innovative strategy allows for the rapid construction of diverse fused benzoazepine structures, yielding structurally novel and compelling compounds. With a broad substrate scope and excellent functional group tolerance, the methodology synthesizes biologically active compounds. Notably, the resulting tricyclic benzo[ b ]azepines offer diversification opportunities through simple transformations. DFT calculations elucidate a seven-membered ring closure mechanism involving the alkenyl radical and Pd(I) rebound alongside a concerted metalation–deprotonation (CMD) process.