High-Yielding Syntheses of Crown Ether-Based Pyridyl Cryptands

Pyridinium
bis­(trifluoromethylsulfonyl)­imide (PyTFSI)-templated
syntheses of 2,6-pyridyl cryptands of cis(4,4′)-dibenzo-30-crown-10
(3a), the p-bromobenzyloxy derivative 3b, bis­(m-phenylene)-32-crown-10 (5), cis(4,4′)-dibenzo-27S-crown-9 (7), cis(4,4′)-dibenzo-27L-crown-9 (9), and cis(4,4′)-dibenzo-24-crown-8 (11) are reported. Here we provide a fast (12 h), high-yielding
(89%, 74%, 80%, and 62% for 3a, 3b, 5, and 9, respectively) templation method without
the use of a syringe pump. The yields for 7 (19%) and 11 (26%) were lower than with the previous pseudo-high-dilution
method, indicating ineffective templation in these cases. Coupled
with our previously developed templated syntheses of dibenzo crown
ethers, this protocol makes powerful cryptand hosts readily available
in gram quantities in good yields from methyl 4­(or 3)-hydroxy-3­(or
4)-benzyloxybenzoate.

本文报道了以吡啶鎓双(三氟甲磺酰基)酰亚胺(Pyridinium bis(trifluoromethylsulfonyl)imide, PyTFSI)为模板，合成一系列2,6-吡啶基穴醚的方法，涉及产物包括顺式(4,4′)-二苯并30-冠-10型穴醚（3a）、其对溴苄氧基取代衍生物3b、双(间亚苯基)-32-冠-10型穴醚（5）、顺式(4,4′)-二苯并27S-冠-9型穴醚（7）、顺式(4,4′)-二苯并27L-冠-9型穴醚（9）以及顺式(4,4′)-二苯并24-冠-8型穴醚（11）。本研究提供了一种无需注射泵、耗时仅12 h的高产率模板合成策略，其中化合物3a、3b、5与9的产率分别为89%、74%、80%与62%。而化合物7（产率19%）与11（产率26%）的合成结果低于此前拟高稀释法的报道水平，说明此两种体系的模板效应未能有效发挥。结合我们此前开发的二苯并冠醚模板合成方法，该方案可从4(或3)-羟基-3(或4)-苄氧基苯甲酸甲酯出发，以良好的产率便捷制备克级规模的高性能穴醚主体。