A series of N‐alkyl‐ and N‐aryl‐viologens has been studied in alkaline solutions. In this work, we evaluated the deuteration rate of the viologens in D2O solutions of pH values ranging from 7.3 to 12.7. Kinetic experiments and computational calculations showed the high reactivity of H‐C(2) bonds toward deprotonation of N‐aryl‐pyridinium moieties compared to N‐alkyl‐pyridinium moieties, even in hybrid N‐aryl/N‐alkyl dissymmetric viologens. However this high H‐C(2) reactivity in liquid phase contrasted with the proton fragmentation mechanism observed in the gas phase by mass spectrometry. The H/D exchange rate of viologens in very strong alkaline conditions could be significantly reduced using cucurbit[7]uril (CB[7]) as supramolecular protecting group. Ultimately, CB[7] inclusion led to a selective protection of H‐C(2) group of N‐aryl‐pyridinium of dissymmetric viologens, and induced a supramolecular regioselective deuteration.

中文翻译：

---

通过葫芦[7]脲络合控制紫罗碱在碱性溶液中的反应性


在碱性溶液中研究了一系列 N-烷基-和 N-芳基-紫精。在这项工作中，我们评估了紫精在 pH 值范围为 7.3 至 12.7 的 D2O 溶液中的氘化速率。动力学实验和计算计算表明，与 N-烷基-吡啶鎓部分相比，H-C(2) 键对 N-芳基-吡啶鎓部分的去质子化具有高反应性，即使在混合 N-芳基/N-烷基不对称紫精中也是如此。然而，液相中的这种高 H-C(2) 反应性与通过质谱在气相中观察到的质子碎裂机制形成鲜明对比。使用葫芦[7]脲(CB[7])作为超分子保护基团可以显着降低紫精在强碱性条件下的H/D交换率。最终，CB[7]的包含导致了不对称紫精的N-芳基吡啶鎓的H-C(2)基团的选择性保护，并诱导了超分子区域选择性氘化。