Pillararene-Catalyzed Kemp Elimination: High Efficiency through Orthogonal Self-Sorting Binding and Ion Modulation

Enhancing the efficiency and versatility
of supramolecular
catalysis
remains a central research goal. Water-soluble pillar[6]arenes (H1),
per-substituted with quaternary ammonium groups, catalyze the aqueous-phase
Kemp elimination of 1,2-benzisoxazole (R1), achieving kcat/kuncat ratio up to 1.5
× 105 at pH 8, surpassing previously reported macrocycles
for the reaction and rivaling the remarkable rate enhancements (up
to 2 × 105-fold) of coordination cages. Orthogonal
self-sorting binding enables R1 to anchor in the hydrophobic cavity
while OH– enriches at the positively charged portals,
facilitating substrate preorganization and enrichment. Ions, including
OH–, selectively weaken the binding of the anionic
product while strengthening substrate R1 association, mitigating product
inhibition and boosting turnover. Robust catalysis at pH 6–7
and recyclability provide a sustainable, enzyme-mimetic catalytic
strategy.