Academy of Scientific and Innovative Research (AcSIR)Physical/Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr.HomiBhabha Road, Pune-, 411008, India.
Angew Chem Int Ed Engl. 2017 Feb 13;56(8):2123-2126. doi: 10.1002/anie.201611260. Epub 2017 Jan 18.
Amine-linked (C-NH) porous organic cages (POCs) are preferred over the imine-linked (C=N) POCs owing to their enhanced chemical stability. In general, amine-linked cages, obtained by the reduction of corresponding imines, are not shape-persistent in the crystalline form. Moreover, they require multistep synthesis. Herein, a one-pot synthesis of four new amine-linked organic cages by the reaction of 1,3,5-triformylphloroglucinol (Tp) with different analogues of alkanediamine is reported. The POCs resulting from the odd diamine (having an odd number of -CH groups) is conformationally eclipsed, while the POCs constructed from even diamines adopt a gauche conformation. This odd-even alternation in the conformation of POCs has been supported by computational calculations. The synthetic strategy hinges on the concept of Schiff base condensation reaction followed by keto-enol tautomerization. This mechanism is the key for the exceptional chemical stability of cages and facilitates their resistance towards acids and bases.
胺连接的（C-NH）多孔有机笼（POC）比亚胺连接的（C=N）POC 更受欢迎，因为它们具有增强的化学稳定性。通常，通过还原相应的亚胺获得的胺连接的笼在晶态下不是形状持久的。此外，它们需要多步合成。本文报道了通过 1,3,5-三醛基苯并三嗪（Tp）与不同的烷二胺类似物反应一锅法合成了四个新的胺连接的有机笼。由奇数二胺（具有奇数个-CH 基团）得到的 POC 是构象重叠的，而由偶数二胺构建的 POC 则采用 gauche 构象。POC 构象中的奇偶交替得到了计算计算的支持。该合成策略基于席夫碱缩合反应随后是酮-烯醇互变异构的概念。该机制是笼状化合物具有异常化学稳定性的关键，并使其能够抵抗酸和碱。
