Synthesis of a Möbius carbon nanobelt
Yasutomo Segawa,* Tsugunori Watanabe, Kotono Yamanoue, Motonobu Kuwayama, Kosuke Watanabe, Kenichiro Itami*
Nature Synth. 2022, DOI: 10.1038/s44160-022-00075-8
ChemRxiv 2021, DOI: 10.26434/chemrxiv-2021-w09lc
New technologies for the creation of topological carbon nanostructures have significantly advanced synthetic organic chemistry and materials science. While simple molecular nanocarbons with a belt topology have been constructed recently, analogous carbon nanobelts with a twist, i.e., Möbius carbon nanobelts (MCNBs), have not yet been synthesized due to their high intrinsic strain. Herein, we report the synthesis, isolation, and characterization of a MCNB. Calculations of strain energies suggested that large MCNBs are synthetically accessible. Designing a macrocyclic precursor with an odd number of repeat units led to a successful rational synthetic route via Z-selective Wittig reactions and nickel-mediated intramolecular homocoupling reactions, which yielded (25,25)MCNB over 14 steps. NMR and theoretical calculations revealed that the twist moiety of the Möbius band moves quickly around the MCNB molecule in solution. The topological chirality originating from the Möbius structure was confirmed experimentally using chiral HPLC separation and CD spectroscopy.