Su Zhi-Ming, Deng Ruohan, Stahl Shannon S
Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
Nat Chem. 2024 Dec;16(12):2036-2043. doi: 10.1038/s41557-024-01627-5. Epub 2024 Sep 6.
Zinc and manganese are widely used as reductants in synthetic methods, such as nickel-catalysed cross-electrophile coupling (XEC) reactions, but their redox potentials are unknown in organic solvents. Here we show how open-circuit potential measurements may be used to determine the thermodynamic potentials of Zn and Mn in different organic solvents and in the presence of common reaction additives. The impact of these Zn and Mn potentials is analysed for a pair of Ni-catalysed reactions, each showing a preference for one of the two reductants. Ni-catalysed coupling of N-alkyl-2,4,6-triphenylpyridinium reagents (Katritzky salts) with aryl halides are then compared under chemical reaction conditions, using Zn or Mn reductants, and under electrochemical conditions performed at applied potentials corresponding to the Zn and Mn reduction potentials and at potentials optimized to achieve the maximum yield. The collective results illuminate the important role of reductant redox potential in Ni-catalysed XEC reactions.
锌和锰在合成方法中被广泛用作还原剂，如镍催化的交叉亲电偶联（XEC）反应，但它们在有机溶剂中的氧化还原电位尚不清楚。在此，我们展示了如何通过开路电位测量来确定锌和锰在不同有机溶剂以及常见反应添加剂存在下的热力学电位。针对一对镍催化的反应，分析了这些锌和锰电位的影响，每个反应对两种还原剂中的一种表现出偏好。然后，在化学反应条件下，使用锌或锰还原剂，以及在对应于锌和锰还原电位的外加电位和优化以实现最大产率的电位下进行电化学条件下，比较了N-烷基-2,4,6-三苯基吡啶试剂（卡特里茨基盐）与芳基卤化物的镍催化偶联反应。这些综合结果阐明了还原剂氧化还原电位在镍催化的XEC反应中的重要作用。
