Copper-Catalyzed Electrochemical C–H Amination of Arenes with Secondary Amines

Electrochemical
oxidation represents an environmentally friendly
solution to conventional methods that require caustic stoichiometric
chemical oxidants. However, C–H functionalizations merging
transition-metal catalysis and electrochemical techniques are, to
date, largely confined to the use of precious metals and divided cells.
Herein, we report the first examples of copper-catalyzed electrochemical
C–H aminations of arenes at room temperature using undivided
electrochemical cells, thereby providing a practical solution for
the construction of arylamines. The use of n-Bu4NI as a redox mediator is crucial for this transformation.
On the basis of mechanistic studies including kinetic profiles, isotope
effects, cyclic voltammetric analyses, and radical inhibition experiments,
the reaction appears to proceed via a single-electron-transfer (SET)
process, and a high valent Cu­(III) species is likely involved. These
findings provide a new avenue for transition-metal-catalyzed electrochemical
C–H functionalization reactions using redox mediators.

电化学氧化相较于需使用化学计量腐蚀性氧化剂的传统工艺，是一种环境友好的解决方案。然而，迄今为止，融合过渡金属催化与电化学技术的C-H官能化反应，在很大程度上仍仅局限于贵金属与分隔式电解池的使用。本文首次报道了以无分隔式电解池为反应装置，在室温下实现铜催化芳烃的C-H胺化反应，为芳胺类化合物的构建提供了切实可行的途径。以四丁基碘化铵（n-Bu4NI）作为氧化还原介质，是该转化反应的关键所在。基于动力学曲线、同位素效应、循环伏安分析以及自由基抑制实验等机理研究，该反应大概率通过单电子转移（SET）路径进行，且可能涉及高价铜(III)活性物种。上述研究成果为采用氧化还原介质的过渡金属催化电化学C-H官能化反应开辟了全新的研究路径。