Enantioselective synthesis of bulky planar-chiral pillar[n]arenes through dynamic kinetic resolution

The precise synthesis of planar chiral pillar[n]arenes (PAs) faces significant challenges due to their inherent dynamic racemization induced by rapid molecular flipping. To address this issue and enhance conformational stability of these macrocycles, we have developed a strategic approach involving the introduction of sterically bulky aryl (sp²) substituents at the molecular rims through dynamic kinetic resolution (DKR). A series of robust and chirality-aligned homo- and hetero-diaryl PAs (n = 5, 6) were achieved with excellent enantioselectivity (>95 % ee) via Pd-catalyzed asymmetric Suzuki–Miyaura coupling reactions. Mechanism study revealed axial steric hindrance, rather than radial substitution, governs conformational chirality-locking in pillar[n]arenes. This work not only provides an attractive protocol for the enantioselective synthesis of planar chiral pillar[n]arenes, but also enriches the library of macrocycles for promising applications in chiral molecular machines, enantioselective sensors, and chiral luminescent materials.