Chemistry with Electrochemically Generated N-Centered Radicals

作者：Peng Xiong, Hai‐Chao Xu · 发表于：Accounts of Chemical Research · 年份：2019 · DOI：10.1021/acs.accounts.9b00472 · 被引用次数：1064 · 研究领域：Radical Photochemical Reactions、Catalytic C–H Functionalization Methods、Sulfur-Based Synthesis Techniques

Conspectus N-centered radicals are versatile reaction intermediates that can react with various π systems to construct C–N bonds. Current methods for generating N-centered radicals usually involve the cleavage of an N–heteroatom bond; however, similar strategies that are applicable to N–H bonds prove to be more challenging to develop and therefore are attracting increasing attention. In this Account, we summarize our recent efforts in the development of electrochemical methods for the generation and synthetic utilization of N-centered radicals. In our studies, N-aryl amidyl radical, amidinyl radical and iminyl radical cation intermediates are generated from N–H precursors through direct electrolysis or indirect electrolysis assisted by a redox catalyst. In addition, an electrocatalytic method that converts oximes to iminoxyl radicals has also been developed. The electrophilic amidyl radical intermediates can participate in 5- exo or 6- exo cyclization with alkenes and alkynes to afford C-centered radicals, which can then undergo various transformations such as H atom abstraction, single-electron transfer oxidation to a carbocation, cyclization, or aromatic substitution, leading to a diverse range of N-heterocyclic products. Furthermore, amidinyl radicals, iminyl radical cations, and iminoxyl radicals can undergo intramolecular aromatic substitution to afford various N-heteroaromatic compounds. Importantly, the electrochemical reaction can be channeled toward a specific produc...