Synthesis and chiral resolution of a triply twisted Möbius carbon nanobelt

Atomically precise synthesis of topological molecular carbons such as Möbius carbon nanobelts (MCNBs) represents a big challenge in synthetic organic chemistry as it requires careful control of both twist and strain. So far, only one singly twisted MCNB has been reported and the MCNBs with more than two twists remain unknown. Herein, we report the facile synthesis of the first triply twisted MCNB by rational design and via a synthetic route involving Suzuki coupling-mediated macrocyclization, Bi(OTf)3-catalyzed cyclization of vinyl ethers, followed by oxidative dehydrogenation. The Möbius band-like structure was unambiguously confirmed by X-ray crystallographic analysis, which also revealed coexistence of (P,P,P)- and (M,M,M)- enantiomers. The racemic isomers were resolved by chiral HPLC and the isolated enantiomers exhibited a large absorption dissymmetry factor (|gabs| = 0.019) according to circular dichroism spectroscopy, which can be explained by the fully conjugated structure and the desirable orientation of the electric and magnetic transition moments.