Kinetics of Palladium(0)‐Allyl Interactions in the Tsuji‐Trost Reaction, derived from Single‐Molecule Fluorescence Microscopy
Kinetics of Palladium(0)‐Allyl Interactions in the Tsuji‐Trost Reaction, derived from Single‐Molecule Fluorescence Microscopy
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DOI：
10.1002/cctc.202000032
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发表时间：
2020-04
期刊：
影响因子：
4.5
通讯作者：
Johannes Menges;Alexander Grandjean;Anne Clasen;G. Jung
中科院分区：
文献类型：
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作者：
Johannes Menges;Alexander Grandjean;Anne Clasen;G. Jung
单分子（SM）化学致力于揭开隐藏在比色皿实验中的反应步骤。关于Tsuji-Trost脱烯丙基化过程中底物活化的争议促使我们在单分子水平上使用我们最近设计的双色荧光探针研究催化剂前体Pd（PPh 3）4的动力学。通过光谱分离的单分子TIRF显微镜和最先进的分析程序的组合，发现并考虑了光化学、无金属旁路反应。非选择性的π-复合物形成（KD = 103 M−1）先于活性催化剂插入C-OR键（RO−=离去基团），这通过荧光颜色的缺乏立即变化来表示。然后，形成的中间体在≥2 - 3 s的时间尺度上分解为脱烯丙基化产物。
Single‐molecule (SM) chemistry is devoted to unravel reaction steps which are hidden in cuvette experiments. Controversies about the substrate activation during the Tsuji‐Trost deallylation motivated us to study, on the single‐molecule level, the kinetics of the catalyst precursor Pd(PPh3)4 with our recently designed two‐color fluorescent probes. Photochemical, metal‐free bypass reactions were found and taken into account by the combination of spectrally separated single‐molecule TIRF‐microscopy and state‐of‐the art analysis procedures. Unselective π‐complex formation (KD≈103 M−1) precedes the insertion of the active catalyst into the C−OR bond (RO−=leaving group), indicated by the lacking immediate change of fluorescence color. The formed intermediate then decomposes on a time scale of≥2 – 3 s to the deallylated product.