Modular Introduction of endo‐Binding Sites in a Macrocyclic Cavity towards Selective Recognition of Neutral Azacycles

Abstract Macrocycles with a functionalized interior, which is a general cavity feature of bioreceptors, are relatively hard to synthesize. Here we report a modular strategy to customize diverse endo ‐binding sites in the macrocycle cavity. Only two steps are needed. First, one V‐shaped functional module bearing an embedded binding site and two 2,5‐dimethoxyphenyls as reaction modules are connected. Then the condensation of the resulting monomer and paraformaldehyde directly produces the designed macrocycle. V‐shaped monomers are deliberately used to guarantee the binding sites equatorially directing inward into the cavity and 2,5‐dimethoxyphenyls standing axially as macrocycle sidewalls. More than a dozen endo ‐functionalized macrocyclic receptors have been constructed. Host–guest complexation studies show that macrocycle BP1‐decorated interior OH moieties can strongly encapsulate neutral azacycles by forming inner hydrogen bonds, giving a high association constant of 4.59×10 4 M −1 in non‐polar media.