Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States.
Research Computing Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3420, United States.
J Am Chem Soc. 2022 Aug 24;144(33):15118-15131. doi: 10.1021/jacs.2c04577. Epub 2022 Aug 9.
A mechanistic investigation into the amination of electron-neutral and electron-rich arenes using organic photoredox catalysis is presented. Kinetic and computational data support rate-limiting nucleophilic addition into an arene cation radical using both azole and primary amine nucleophiles. This finding is consistent with both fluoride and alkoxide nucleofuges, supporting a unified mechanistic picture using cation radical accelerated nucleophilic aromatic substitution (CRA-SAr). Electrochemistry and time-resolved fluorescence spectroscopy confirm the key role solvents play in enabling selective arene oxidation in the presence of amines. The synthetic limitations of xanthylium salts are elucidated via photophysical studies. An alternative catalyst scaffold with improved turnover numbers is presented.
本文对有机光氧化还原催化条件下电子中性和富电子芳环的胺化反应进行了机理研究。动力学和计算数据支持使用唑类和伯胺亲核试剂进行芳环正碳离子的限速亲核加成。这一发现与氟化物和亲核试剂一致，支持使用正碳离子加速亲核芳香取代（CRA-SAr）的统一机理。电化学和时间分辨荧光光谱证实了溶剂在胺存在时选择性氧化芳环中的关键作用。通过光物理研究阐明了氧杂蒽鎓盐的合成限制。提出了一种具有改进周转数的替代催化剂支架。
