Trifluoroacetic acid (TFA) catalyzed condensation reaction between tetraaminooxacalix[4]arene and -alkylcarbazole-3,6-dicarbaldehyde in CHCl afforded a single product in 87%–89% yield. Well-defined yet undissolvable H NMR spectra suggested formation of robust and discrete structures in solution. X-ray single crystal analysis further revealed a giant twisted double-layer chiral macrocycle in the solid state, which was formed from [4 + 8] condensation of the two reactants 16 imine bonds. DFT calculations discovered that only the [4 + 8] twisted product is thermodynamically favorable, which accounts for its highly selective and efficient formation out of a library of many other combinations.

中文翻译：

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[4+8]亚胺缩合一锅法合成巨型扭曲双层手性大环化合物及其X射线结构


三氟乙酸（TFA）催化四氨基恶萼[4]芳烃和-烷基咔唑-3,6-二甲醛在CH2Cl2中进行缩合反应，得到单一产物，产率87%–89%。明确但不可溶解的 1H NMR 谱表明在溶液中形成了坚固且离散的结构。 X射线单晶分析进一步揭示了固态下巨大的扭曲双层手性大环，它是由两种反应物16个亚胺键的[4+8]缩合形成的。 DFT 计算发现，只有 [4 + 8] 扭曲产物在热力学上是有利的，这解释了它从许多其他组合库中高度选择性和高效形成的原因。