Wang Yulei, Oliveira João C A, Lin Zhipeng, Ackermann Lutz
Institut für Organische und Biomolekulare Chemie, and Wöhler Research Institute for Sustainable Chemistry, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany.
Angew Chem Int Ed Engl. 2021 Mar 15;60(12):6419-6424. doi: 10.1002/anie.202016895. Epub 2021 Feb 8.
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.
涉及温和过渡金属催化的C-H活化的电氧化环化反应已成为快速构建五元及六元杂环的变革性策略。相比之下，我们在此描述了首例电化学金属催化的[5+2]环加成反应，通过C-H/O-H活化来组装有价值的七元苯并氧杂环庚烷骨架。这种高效的炔烃环化反应底物范围广泛，仅以电作为唯一的氧化剂。机理研究有力地支持了铑(III/I)机制，其中涉及一种苯并氧杂环庚烷配位的铑(I)夹心配合物作为催化剂的静止状态，该配合物通过阳极氧化重新氧化为铑(III)。
