An unprecedented single electron redox process in copper catalysis is confirmed using operando X-ray absorption and EPR spectroscopies. The oxidation state of the copper species in the interaction between Cu(II) and a sulfinic acid at room temperature, and the accurate characterization of the formed Cu(I) are clearly shown using operando X-ray absorption and EPR evidence. Further investigation of anion effects on Cu(II) discloses that bromine ions can dramatically increase the rate of the redox process. Moreover, it is proven that the sulfinic acids are converted into sulfonyl radicals, which can be trapped by 2-arylacrylic acids and various valuable β-keto sulfones are synthesized with good to excellent yields under mild conditions.
利用操作性 X 射线吸收和 EPR 光谱证实了
铜催化过程中前所未有的单电子氧化还原过程。利用操作性 X 射线吸收和 EPR 证据清楚地显示了室温下
铜(II)与
亚硫酸相互作用中
铜物种的氧化态,以及所形成的
铜(I)的准确特征。进一步研究阴离子对 Cu(II) 的影响发现,
溴离子能显著提高氧化还原过程的速率。此外,研究还证明,
亚硫酸可转化为磺酰基自由基,这些自由基可被 2-芳基
丙烯酸捕获,并在温和的条件下合成出各种有价值的 β-酮砜,产量从高到优。