Center of Chemistry for Frontier Technologies, Department of Chemistry, Zhejiang University, Hangzhou, 310027, China.
Angew Chem Int Ed Engl. 2023 Mar 6;62(11):e202218533. doi: 10.1002/anie.202218533. Epub 2023 Feb 1.
In recent years, the merging of electrosynthesis with 3d metal catalyzed C-H activation has emerged as a sustainable and powerful technique in organic synthesis. Despite the impressive advantages, the development of an enantioselective version remains elusive and poses a daunting challenge. Herein, we report the first electrooxidative cobalt-catalyzed enantio- and regioselective C-H/N-H annulation with olefins using an undivided cell at room temperature (up to 99 % ee). Bu-Salox, a rationally designed Salox ligand bearing a bulky tert-butyl group at the ortho-position of phenol, was found to be crucial for this asymmetric annulation reaction. A strong cooperative effect between Bu-Salox and 3,4,5-trichloropyridine enabled the highly enantio- and regioselective C-H annulation with the more challenging α-olefins without secondary bond interactions (up to 96 % ee and 97 : 3 rr). Cyclovoltametric studies, and the preparation, characterization, and transformation of cobaltacycle intermediates shed light on the mechanism of this reaction.
近年来，电合成与 3d 金属催化的 C-H 活化相结合，在有机合成中作为一种可持续且强大的技术出现。尽管具有令人印象深刻的优势，但对其对映选择性版本的开发仍然难以捉摸，构成了一项艰巨的挑战。在此，我们报道了首例使用非分隔电池在室温下（最高 99%ee）进行的电氧化钴催化的对映选择性和区域选择性 C-H/N-H 稠合反应，其中包括烯烃。经过合理设计的 Salox 配体 Bu-Salox 在苯酚的邻位带有庞大的叔丁基，被发现是这种不对称环合反应的关键。Bu-Salox 和 3,4,5-三氯吡啶之间的强烈协同效应使更具挑战性的α-烯烃能够进行高度对映选择性和区域选择性的 C-H 环合，而无需次级键相互作用（最高 96%ee 和 97:3rr）。循环伏安研究以及钴配合物中间体的制备、表征和转化揭示了该反应的机理。
