Electrically Driven C-H Functionalization with CuII/CuIII Redox Catalysts

点击翻译按钮获取中文摘要

Project Summary This proposal aims to develop new synthetic methods that utilize electrical energy for C-H functionalization re- actions. Electrically driven C-H functionalization is significant since it eliminates superstoichiometric amounts of strong oxidants that often contribute to high costs and poor site selectivity. The innovation of the proposed work is the development of CuIII/CuII-Nu redox catalysts, where Nu represents various carbon and heteroatom-based nucleophiles. These CuIII-Nu complexes feature inverted ligand fields, where LUMO resides on the ligand instead of the Cu center. Therefore, electrochemically generated CuIII-Nu complexes can serve as tamed sources of Nu radical to enable hydrogen atom transfer and radical interception. Our method separates two-electron C-H func- tionalization processes into two parallel, single-electron oxidation events with fast electrode kinetics. As a result, the CuII/CuIII mediated C-H functionalization occurs at much lower potentials (by 0.5-2 V) than those of traditional electrochemical C-H functionalization methods, significantly improving energy efficiency and selectivity. Prelim- inary result shows selective functionalization of C(sp3)-H bonds with a wide range of simple nucleophiles that are otherwise incompatible with chemical oxidants typically used in conventional C-H functionalization reactions, For example, fluoride, which is known to cause decomposition of a wide range of oxidants, can be directly used as F source under our electrochemical condition. The only side products are readily manageable metal salts, significantly reducing the cost. Moreover, all CuIII-Nu intermediate can be isolated and characterized at low tem- peratures to reveal fundamental properties and reactivity, e.g., redox potentials, hydrogen atom transfer, radical capture, alkene addition, and other unproductive reactivity. This information is used to select suitable electro- chemical/chemical conditions, e.g., voltage, current, temperature, ligand, to rationally improve the reaction effi- ciency and selectivity.