Reducing rotatable bonds in one substrate accelerates a bimolecular Diels–Alder reaction in a bis-calix[4]pyrrole cage

Abstract

We report the quantitative self-assembly of an endohedrally functionalized octa-imine cage from two calix[4]pyrrole scaffolds via dynamic covalent chemistry. The cavity combines size and shape complementarity with enzyme-like directional guest binding. Acting as a molecular flask, the cage stereoselectively promotes a bimolecular Diels–Alder reaction, shifting the equilibrium toward the product. Restricting substrate rotation enhanced the reaction rate dramatically (k_included/k_bulk ≈ 600 M).