The Institute for Advanced Studies (IAS), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, Hubei, P. R. China.
National Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, P. R. China.
J Am Chem Soc. 2022 Aug 3;144(30):13895-13902. doi: 10.1021/jacs.2c05520. Epub 2022 Jul 21.
Selective cleavage and functionalization of C-C bonds in alcohols is gaining increasing interest in organic synthesis and biomass conversion. In particular, the development of redox-neutral catalytic methods with cheap catalysts and clean energy is of utmost interest. In this work, we report a versatile redox-neutral method for the ring-opening functionalization of cycloalkanols by electrophotochemical (EPC) cerium (Ce) catalysis. The EPC-Ce-enabled catalysis allows for cycloalkanols with different ring sizes to be cleaved while tolerating a broad range of functional groups. Notably, in the presence of chloride as a counteranion and electrolyte, this protocol selectively leads to the formation of C-CN, C-C, C-S, or C-oxime bonds instead of a C-halide bond after β-scission. A preliminary mechanistic investigation indicates that the redox-active Ce catalyst can be tuned by electro-oxidation and photo-reduction, thus avoiding the use of an external oxidant. Spectroscopic characterizations (cyclic voltammetry, UV-vis, electron paramagnetic resonance, and X-ray absorption fine structure) suggest a Ce(III)/Ce(IV) catalytic pathway for this transformation, in which a Ce(IV)-alkoxide is involved.
选择性地切割和功能化醇中的 C-C 键在有机合成和生物质转化中引起了越来越多的兴趣。特别是，开发使用廉价催化剂和清洁能源的氧化还原中性催化方法具有至关重要的意义。在这项工作中，我们报告了一种通过光电化学（EPC）铈（Ce）催化实现环烷醇开环官能化的通用氧化还原中性方法。EPC-Ce 催化允许不同环大小的环烷醇断裂，同时容忍广泛的官能团。值得注意的是，在氯化物作为抗衡阴离子和电解质的存在下，该方案选择性地导致 C-CN、C-C、C-S 或 C-肟键的形成，而不是β-断裂后形成 C-卤键。初步的机理研究表明，氧化还原活性 Ce 催化剂可以通过电化学氧化和光还原来调节，从而避免使用外部氧化剂。光谱表征（循环伏安法、紫外-可见光谱、电子顺磁共振和 X 射线吸收精细结构）表明，该转化存在 Ce(III)/Ce(IV)催化途径，其中涉及 Ce(IV)-烷氧基。
