单羟基-葫芦 [n] 脲 (n= 5, 6, 7, 8) 的综合合成：高纯度和高转化率,Journal of the American Chemical Society

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单羟基-葫芦 [n] 脲 (n= 5, 6, 7, 8) 的综合合成：高纯度和高转化率
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2015-08-05 , DOI: 10.1021/jacs.5b04553
Mehmet M. Ayhan _{1,

2} , Hakim Karoui ₁ , Micaël Hardy ₁ , Antal Rockenbauer ₃ , Laurence Charles ₁ , Roselyne Rosas ₄ , Konstantin Udachin ₅ , Paul Tordo ₁ , David Bardelang ₁ , Olivier Ouari ₁

Affiliation

我们描述了一种光化学方法，直接在葫芦 [n] 脲 (n = 5, 6, 7, 8) 上引入单一醇功能，使用过氧化氢和紫外线的转化率为 95-100%。对于 CB[6] 和 CB[7]，反应很容易放大到 1g。葫芦脲自由基的自旋捕获结合 MS 实验使我们能够深入了解反应机理并表征 CB[5]、CB[6]、CB[7] 和 CB[8] 单官能化合物。涉及 (18)O 同位素标记水的实验表明，该机制很复杂，并显示出自由基和离子中间体的迹象。DFT 计算允许估算 CB 系列中每种氢原子类型的键解离能 (BDE)，从而解释了 CB[n] 化合物的“赤道”CH 位置的较高反应性。这些结果还表明，对于 CB[8]，葫芦脲骨架上的直接官能化更加困难，因为其中一个亚甲基氢原子 (Hb) 在系列内的 BDE 降低并接近 Hc，从而开辟了道路CB[8] 骨架上产生的其他类型的自由基导致几种副产物。然而，由于这里介绍的软方法，CB[5]-(OH)1 和 CB[8]-(OH)1，第一个 CB[8] 衍生物，以极好的收率获得。

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Comprehensive Synthesis of Monohydroxy–Cucurbit[n]urils (n= 5, 6, 7, 8): High Purity and High Conversions

We describe a photochemical method to introduce a single alcohol function directly on cucurbit[n]urils (n = 5, 6, 7, 8) with conversions of the order 95-100% using hydrogen peroxide and UV light. The reaction was easily scaled up to 1 g for CB[6] and CB[7]. Spin trapping of cucurbituril radicals combined with MS experiments allowed us to get insights about the reaction mechanism and characterize CB[5], CB[6], CB[7], and CB[8] monofunctional compounds. Experiments involving (18)O isotopically labeled water indicated that the mechanism was complex and showed signs of both radical and ionic intermediates. DFT calculations allowed estimating the Bond Dissociation Energies (BDEs) of each hydrogen atom type in the CB series, providing an explanation of the higher reactivity of the "equatorial" C-H position of CB[n] compounds. These results also showed that, for CB[8], direct functionalization on the cucurbituril skeleton is more difficult because one of the methylene hydrogen atoms (Hb) has its BDE lowering within the series and coming close to that of Hc, thus opening the way to other types of free radicals generated on the CB[8] skeleton leading to several side products. Yet CB[5]-(OH)1 and CB[8]-(OH)1, the first CB[8] derivative, were obtained in excellent yields thanks to the soft method presented here.

更新日期：2015-08-05

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