Synthesis of Cycloparaphenylenes Bearing Furan‐2,5‐diyl or 2,2’‐Bifuran‐5,5’‐diyl Units in the Macrocyclic Structures

Synthetic pathways to furan-containing cycloparaphenylenes (CPPs) as molecular nanohoops bearing 10, 12, and 15 aromatic units including furan-2,5-diyl or 2,2′-bifuran-5,5′-diyl units have been developed. A [4 + 2]cycloaddition reaction, homo- or cross-coupling reactions, and an oxidative aromatization reaction are the key steps of the synthetic pathways. The X-ray structures of a partially hydrogenated bifuran-containing CPP precursor and the corresponding fully aromatized bifuran-containing CPP were obtained to allow the determination of their conformational arrangements in the crystal lattice. The optical and electrochemical properties of the furan-containing CPPs were investigated.