Synthesis, Structures, and CPL Property of Inner‐Wall Modified Pagoda[5]Arenes Driven by Cavity Microenvironment
Yu‐Jie Long, Wei‐Chen Guo, Junfeng Xiang, Ying Han, Zhi‐Qiang Hu, Chuan‐Feng Chen
Abstract
Macrocyclic arenes with large cavities and chirality are attractive in supramolecular chemistry, but fixing their conformation and obtaining stable chirality remain significant challenges. The method of rim functionalization with bulky groups often involves multiple reactive sites, leading to poor selectivity and efficiency. Herein, the inner-wall modification as a promising yet underexplored strategy for achieving fixed conformation and stable chirality of pagoda[5]arene (P5) was developed. Consequently, a series of inner-wall modified P5 derivatives were obtained in high yields under mild conditions by the highly efficient and selective Diels-Alder (D-A) cycloadditions of P5 with (E)-1,2-bis(N-alkyl-4-pyridinium)ethylene guests, enabled by the guest pre-organization in the cavity microenvironment of P5. In contrast, reactions of 2,6-dimethoxyanthracene and the guests are not observed even at 170 °C due to the absence of the cavity microenvironment. Moreover, a neutral inner-wall modified derivative (P5py) was obtained by post-reaction demethylation. P5py exhibited stable planar chirality, and its enantiomers were efficiently resolved by chiral HPLC. Notably, the enantiomers showed mirror-imaged CD signals and strong CPL property. This work provides a new facile strategy for fixing the conformation and achieving the stable chirality of macrocyclic arenes with chiral large cavities, and thereby broadens their prospects for applications in supramolecular and materials chemistry.