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Creation of negatively curved polyaromatics enabled by annulative coupling that forms an eight-membered ring


The discoveries of new forms of carbon have always opened doors to new science and technology. In 1991, three-dimensional (3D) periodic carbon crystals with negative Gaussian curvatures that consist of six- and eight-membered rings were proposed. To realize these 3D periodic carbon crystals (known as Mackay crystals), methods for creating polyaromatic structures embedding eight-membered rings must be developed. Here we report two annulative coupling reactions that form an eight-membered ring through catalytic C–H functionalization. We have discovered that bay-chlorinated polyaromatics undergo either annulative dimerization or cross-coupling with biphenylene in the presence of a palladium catalyst to form various hitherto inaccessible polyaromatics embedding an eight-membered ring. The threefold annulative cross-coupling of 1,5,9-trichlorotriphenylene allowed construction of a highly curved nanocarbon. The present work not only demonstrates the potential of annulative coupling for constructing octagonal nanocarbons but also provides a conceptual pathway for the synthetic realization of 3D periodic carbon crystals.

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Fig. 1: Overview of the study.
Fig. 2: Annulative dimerization of bay-chlorinated polycyclic aromatic hydrocarbons.
Fig. 3: Proposed reaction mechanism of annulative dimerization.
Fig. 4: Development of annulative cross-coupling of bay-chlorinated polyaromatics.
Fig. 5: Products of threefold annulation.
Fig. 6: Annulative cross-coupling of bay-trichlorinated triphenylene.

Data availability

Materials and methods, experimental procedures, detailed optimization studies, mechanistic studies, photophysical studies and NMR spectra are available in the Supplementary Information or from the corresponding authors upon reasonable request. The atomic coordinates of the optimized models are provided in Supplementary Data 1. Crystallographic data for compounds 5d, 5e and 8a are available free of charge from the Cambridge Crystallographic Data Centre under deposition numbers 1898108, 1898109 and 1898106. Copies of the data can be obtained free of charge via


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This work was supported by JST ERATO grant number JPMJER1302 (K.I.); JSPS KAKENHI grant numbers 19H05463 (K.I.), JP17H04868 (K.M.), JP19H02700 (K.M.), JP19H02701 (Y.S.) and JP19K22183 (Y.S.); Shorai Foundation for Science and Technology (K.M.); and the Noguchi Institute (Y.S. and K.M.). We thank Rigaku Co for assistance with the X-ray analysis. Calculations were performed using resources of the Research Center for Computational Science, Okazaki, Japan. ITbM is supported by the World Premier International Research Center Initiative (WPI), Japan.

Author information




K.I. and K.M. conceived the concept and directed the project. Y.K. and S.M. conducted experiments. Y.S. performed X-ray crystallography. K.I and K.M. prepared the manuscript with feedback from the other authors.

Corresponding authors

Correspondence to Kei Murakami or Kenichiro Itami.

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Competing interests

K.I., K.M. and Y.K. are inventors on a patent application (JP 2019-091748) submitted by Nagoya University that covers the synthetic methods and its applications included in this paper.

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Supplementary information

Supplementary Information

Supplementary Methods, Discussion, Tables 1–10, Figs. 1–16, and References.

Supplementary Data 1

Cartesian coordinates.

Supplementary Data

CIF file of compound 5d.

Supplementary Data

CIF file of compound 5e.

Supplementary Data

CIF file of compound 8a.

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Matsubara, S., Koga, Y., Segawa, Y. et al. Creation of negatively curved polyaromatics enabled by annulative coupling that forms an eight-membered ring. Nat Catal 3, 710–718 (2020).

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