Electrooxidative Rhodium‐Catalyzed [5+2] Annulations via C−H/O−H Activations

• Published in: Angewandte Chemie International Edition Vol. 60; no. 12; pp. 6419 - 6424
• Main Authors: Wang, Yulei, Oliveira, João C. A., Lin, Zhipeng, Ackermann, Lutz
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 15.03.2021; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: [5+2] cycloaddition; Alkynes; Anodizing; benzoxepine; Catalysts; Chemical reactions; Chemistry; Chemistry, Multidisciplinary; Communication; Communications; C−H activation; Electrochemistry; electrooxidative annulation; Oxidants; Oxidation; Oxidizing agents; Physical Sciences; Rhodium; Science & Technology; Substrates; Transition metals; ELECTROSYNTHESIS; electrochemistry; benzoxepine; electrooxidative annulation; OXIDATIVE ANNULATION; CLEAVAGE; STRATEGIES; [5+2] cycloaddition; BODIPY DYES; FUNCTIONALIZATION; ANILINES; REGIOSELECTIVE SYNTHESIS; H activation; C− CYCLIZATION; C−H activation
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202016895

Electrooxidative annulations involving mild transition metal‐catalyzed C−H activation have emerged as a transformative strategy for the rapid construction of five‐ and six‐membered heterocycles. In contrast, we herein describe the first electrochemical metal‐catalyzed [5+2] cycloadditions to assemble valuable seven‐membered benzoxepine skeletons by C−H/O−H activation. The efficient alkyne annulation featured ample substrate scope, using electricity as the only oxidant. Mechanistic studies provided strong support for a rhodium(III/I) regime, involving a benzoxepine‐coordinated rhodium(I) sandwich complex as the catalyst resting state, which was re‐oxidized to rhodium(III) by anodic oxidation. Electrochemical rhodium‐catalyzed [5+2] cycloadditions to assemble seven‐membered benzoxepines have been accomplished guided by detailed mechanistic insights.