Department of Organic Chemistry, University of Geneva, Geneva, Switzerland.
Angew Chem Int Ed Engl. 2020 Aug 24;59(35):15093-15097. doi: 10.1002/anie.202000681. Epub 2020 Mar 17.
Anion-π catalysis functions by stabilizing anionic transition states on aromatic π surfaces, thus providing a new approach to molecular transformation. The delocalized nature of anion-π interactions suggests that they serve best in stabilizing long-distance charge displacements. Aiming therefore for an anionic cascade reaction that is as charismatic as the steroid cyclization is for conventional cation-π biocatalysis, reported here is the anion-π-catalyzed epoxide-opening ether cyclizations of oligomers. Only on π-acidic aromatic surfaces having a positive quadrupole moment, such as hexafluorobenzene to naphthalenediimides, do these polyether cascade cyclizations proceed with exceptionally high autocatalysis (rate enhancements k /k >10 m ). This distinctive characteristic adds complexity to reaction mechanisms (Goldilocks-type substrate concentration dependence, entropy-centered substrate destabilization) and opens intriguing perspectives for future developments.
阴离子-π 催化通过在芳香族 π 表面稳定阴离子过渡态而起作用，从而为分子转化提供了一种新方法。阴离子-π 相互作用的离域性质表明，它们最适合稳定远距离的电荷位移。因此，本研究旨在实现阴离子级联反应，就像甾体环化反应对于传统的阳离子-π 生物催化一样具有吸引力，报道了寡聚物的环氧化物开环醚环化反应。只有在具有正四极矩的 π 酸性芳族表面上，如六氟苯与萘二亚胺之间，这些聚醚级联环化反应才能以异常高的自动催化（速率增强 k /k >10 m）进行。这种独特的特性增加了反应机制的复杂性（类黄金比例型底物浓度依赖性，熵中心的底物失稳），并为未来的发展开辟了有趣的前景。
