Design, synthesis, and properties of a six-membered oligofuran macrocycle

Herein, we present the synthesis and properties of an ester-functionalized macrocyclic sexifuran (C6FE). This molecule was prepared in a single step from a furan-3-carboxylate dimer using a commercially available palladium catalyst (SPhos-Pd-G3) and isolated in 34% yield. DFT calculations predict the macrocyclic ring is planar, with minimal ring strain. The macrocycle is partially crystalline, as evidenced by powder X-ray diffraction patterns. Furthermore, the solid-state organization can be altered by modification of the ester side-chain. C6FE can also undergo two electron oxidation and reduction in solution as evidenced by cyclic voltammetry. Quantum chemical investigations revealed how aromaticity along the entire sexifuran macrocycle may play a role in the reversible electrochemistry. Overall, we anticipate that the synthetic approach detailed in this report can serve as a foundation to construct new furan-based conjugated macrocycles.