Systematic synthesis and crystallographic characterisation of p-tert-butylcalix[4]arene derivatives bearing linear, achiral branched, and guerbet-type substituents

A systematic series of p-tert-butylcalix[4]arene derivatives bearing linear, achiral branched and Guerbet-type branched hydrocarbons at the lower rim were synthesised via Williamson etherification. Sodium hydride yielded tetra-substituted products, while potassium carbonate produced 1,3-di-substituted derivatives. All compounds were characterised by NMR, FTIR, and mass spectrometry.. Single crystals were obtained from tetra-O-alkylated derivatives with n-dodecyl, n-tetradecyl and 2-ethylbutyl hydrocarbon chains; Guerbet-type derivatives remained viscous oils, reflecting the inability of racemic β-branched architectures to crystallise. X-ray diffraction revealed invariant calix[4]arene core geometries but distinct supramolecular packing: linear chains form head-to-head bilayers through interdigitation, while 2-ethylbutyl disrupts bilayer packing, adopting staggered arrangements stabilised by C–H···π contacts. The 2-ethylbutyl derivative represents the first crystallographic characterisation of any branched-alkyl calix[4]arene, demonstrating that substituent topology fundamentally alters supramolecular organisation.

通过威廉姆森醚化反应（Williamson etherification），系统性合成了一系列对叔丁基杯[4]芳烃（p-tert-butylcalix[4]arene）衍生物，该类衍生物的下缘分别带有直链、非手性支链与盖贝特型（Guerbet-type）支链烃基。以氢化钠（Sodium hydride）为碱时可得到四取代产物，而以碳酸钾（potassium carbonate）为碱时则仅生成1,3-二取代衍生物。所有目标化合物均通过核磁共振波谱法（NMR）、傅里叶变换红外光谱（FTIR）以及质谱法（mass spectrometry）完成了结构表征。连有正十二烷基、正十四烷基与2-乙基丁基烃链的四-O-烷基化衍生物可制备得到单晶；而盖贝特型衍生物始终为粘稠油状液体，这归因于其外消旋β-支化结构无法结晶。X射线衍射（X-ray diffraction）分析结果显示，杯[4]芳烃核心的几何构型保持恒定，但超分子堆积模式存在显著差异：直链烃基衍生物通过分子插层作用形成头对头双层结构；而2-乙基丁基支链则破坏了双层堆积模式，采取由C–H···π相互作用稳定的交错排列构型。2-乙基丁基修饰的衍生物是首例获得晶体学表征的支链烷基杯[4]芳烃，该研究证明取代基的拓扑结构可从根本上改变超分子组装行为。