Chiral arylene-ethynylene macrocycles (AEMs) were synthesized via alkyne metathesis-mediated depolymerization of BINOL-based polymers. Homochiral dimers are selectively obtained from metathesis of heterochiral polymers. Thermodynamic analysis and computational modeling suggests the homochiral self-sorting to be entropy-driven due to the greater symmetry of the homochiral dimers over the heterochiral dimer. This symmetry-controlled reaction is a novel approach to achieving high selectivity in dynamic covalent macrocycle synthesis. Importantly, the result describes a new paradigm in dynamic covalent chemistry that will enable efficient synthesis of new chiral architectures.

The preparation of functional macrocycles via dynamic covalent chemistry (DCC) is an attractive synthetic strategy due to its thermodynamic control over the products. The use of alkyne metathesis has emerged as an efficient DCC method for synthesis of conjugated arylene-ethynylene macrocycles (AEMs), but the scope has been mostly limited to rigid and angle-persistent benzenoid-based structures. Introducing functional groups to macrocycle backbones increases flexibility by relaxing conformational constraints, which often leads to broad product distributions. Here we expand the scope of alkyne metathesis to functionalized macrocycles by systematically exploring how conformation and connectivity interplay to affect product distribution. With a divergent approach, we prepared a series of conjugated polymer analogues and synthesized the corresponding macrocycles via depolymerization. The importance of conformational constraints was reinforced by the results, but it was discovered that minimizing the monomer’s torsional axes provides high yields of functional macrocycles, even those with increased flexibility. We believe that this strategy is applicable in other areas of DCC and self-assembly to enable efficient preparation of organic materials with flexible functional groups.

Macrocyclic oligomers possessing direction-defining ester linkages were synthesized via metathesis of the nondirectional alkyne functional group. Alkyne metathesis is expected to scramble the relative orientation of adjacent ester groups, potentially leading to a complex mixture of macrocyclic products. We wondered whether a narrow product distribution would be achievable with a proper choice of the building block structure. Here we show that the shape of the building block determines whether the macrocyclic products are directionally uniform or scrambled. Specifically, two isomeric arylene-ethynylene polyesters afforded significantly different product distributions upon being subjected to depolymerization-macrocyclization. These results underscore the importance of learning how the shape and geometry of the building blocks affect the macrocyclization energy landscape.