Hydrogen‐Bonding‐Mediated Dynamic Covalent Synthesis of Macrocycles and Capsules: New Receptors for Aliphatic Ammonium Ions and the Formation of Pseudo3rotaxanes

Abstract Dynamic covalent synthesis! Intramolecular hydrogen‐bonding induces amino‐ and aldehyde‐appended aryl amides to adopt a rigid “V”‐shaped conformation. As a result, stable two‐layered capsules can be assembled quantitatively through the one‐step formation of six imine bonds. The new capsules form complexes with aliphatic diammonium ions to give unique two‐layered pseudo3rotaxanes (see figure). magnified image This paper describes a novel, highly efficient approach to the self‐assembly of monomacrocycles and two‐layered capsules by using dynamic covalent chemistry. Intramolecular hydrogen‐bonding was used to preorganize aromatic amide‐based monomers that contain aldehyde and tert ‐butoxycarbonylamino units. As a result, in the presence of an excess of trifluoroacetic acid (TFA), four monomers could self‐couple to produce macrocycles selectively through the formation of three imine or hydrazone bonds. Three dipodal precursors were also prepared by connecting two hydrogen‐bonded segments with a flexible linker. In the presence of TFA, these precursors could also self‐couple, leading to the exclusive formation of two‐layered capsules. As a result of intramolecular hydrogen‐bonding, all the macrocycles and capsules were stable in solution and could be purified by simple recrystallization. The new capsules were able to form complexes with linear propylenediammonium derivatives to give unique two‐layered pseudo3rotaxanes.