Atkins Alexander P, Smith Charlotte A, Ghosh Deborin, Greene Hallam J M, Binyahan Ria G, Greene Ciaran J, Tate Joseph A, Orr-Ewing Andrew J, Lennox Alastair J J
School of Chemistry, University of Bristol Cantock's Close Bristol BS81TS UK
Jealott's Hill International Research Centre Bracknell RG426EY UK.
Chem Sci. 2025 Sep 19. doi: 10.1039/d5sc05561j.
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is a common oxidant used for myriad oxidation reactions, including the functionalisation of electron-rich benzylic C(sp)-H bonds. Under photochemical excitation, DDQ becomes a far more powerful oxidant, though it has scarcely been utilised for C(sp)-H functionalisation nor is the mechanism by which it operates well understood. Here, we report that photochemical excitation of DDQ enables oxidative functionalisation of previously inaccessible electron-poor benzylic C(sp)-H bonds to form benzylic quinol ethers. The methodology is amenable to both batch and flow setups and is demonstrated across a series of primary and secondary benzylic substrates. Transient absorption spectroscopy revealed mechanistic insight into the electron transfer processes involved, indicating a single electron transfer pathway operates under these conditions, contrasting a hydride mechanism previously reported to occur when employing ground-state DDQ.
2,3-二氯-5,6-二氰基-1,4-苯醌（DDQ）是一种常用的氧化剂，可用于多种氧化反应，包括富电子苄基C(sp)-H键的官能团化。在光化学激发下，DDQ成为一种更强大的氧化剂，尽管它几乎未被用于C(sp)-H官能团化，其作用机制也尚未得到很好的理解。在此，我们报告称，DDQ的光化学激发能够实现以前难以实现的贫电子苄基C(sp)-H键的氧化官能团化，以形成苄基喹啉醚。该方法适用于间歇式和连续流动装置，并在一系列伯苄基和仲苄基底物上得到了验证。瞬态吸收光谱揭示了对所涉及的电子转移过程的机理洞察，表明在这些条件下存在单电子转移途径，这与之前报道的使用基态DDQ时发生的氢化物机理形成对比。
