Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Synthesis of strained, air-stable boracycles via boron–carbon-centred diradicals

Nature Chemistry volume 17, pages 663–671 (2025)Cite this article

Subjects

Abstract

Boracycles are important functional scaffolds, often exhibiting superior or unique performance compared with their carbon analogues. Five-membered oxaboracycles are key pharmacophores in Food and Drug Administration-approved boron drugs. Meanwhile, six-membered boron-doped polycyclic aromatic hydrocarbons enhance the diversification and functionality of molecular materials. However, boron-containing four-membered rings are less studied owing to limited preparative approaches. Their inherent ring strain makes their synthesis thermodynamically unfavourable and hinders the exploration of their properties and applications. Here we report a triplet energy transfer catalysis for crafting air-stable benzoboretenes through intramolecular coupling of boron–carbon-centred diradicals. In addition, by modulating substrate π-conjugation structures and excitation energies, boron–carbon-centred diradicals can undergo formal 1,6- and 1,5-cyclization to deliver dihydroborinine and dihydrocyclopropaborole derivatives, respectively. The metal-free neutral reaction conditions ensure a broad reaction scope, resulting in structurally diverse boracycles that are stable enough to be purified via column chromatography. Further modification of the boracycles enables the facile synthesis of oxaborabicycles and dihydroborinine-fused polycyclic aromatic hydrocarbons with unique optoelectronic properties.

Access through your institution
Buy or subscribe

This is a preview of subscription content, access via your institution

Access options

Access through your institution

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Applications and synthesis of boracycles.
Fig. 2: Synthetic elaborations.
Fig. 3: Experimental mechanistic studies.
Fig. 4: Theoretical mechanistic studies.

Similar content being viewed by others

Data availability

The data supporting the findings of this study are available within the article and its Supplementary Information. Crystallographic data for the structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition numbers CCDC 2352027 (2), 2352030 (22S), 2352031 (55), 2352034 (56), 2352033 (62) and 2352035 (70). Copies of the data can be obtained free of charge at https://www.ccdc.cam.ac.uk/structures/.

References

  1. McConnell, C. R. & Liu, S. Y. Late-stage functionalization of BN-heterocycles. Chem. Soc. Rev. 48, 3436–3453 (2019).

    CAS  PubMed  PubMed Central  Google Scholar 

  2. Su, Y. & Kinjo, R. Small molecule activation by boron-containing heterocycles. Chem. Soc. Rev. 48, 3613–3659 (2019).

    CAS  PubMed  Google Scholar 

  3. Su, X. et al. 9-Borafluorenes: synthesis, properties, and reactivity. Chem. Rev. 121, 4147–4192 (2021).

    CAS  PubMed  Google Scholar 

  4. Braunschweig, H., Chiu, C.-W., Radacki, K. & Kupfer, T. Synthesis and structure of a carbene-stabilized π-boryl anion. Angew. Chem. Int. Ed. 49, 2041–2044 (2010).

    CAS  Google Scholar 

  5. Tian, D., Jiang, J., Hu, H., Zhang, J. & Cui, C. One-step access to luminescent pentaaryldiazaboroles via C–C double bond formation from imidoylstannanes. J. Am. Chem. Soc. 134, 14666–14669 (2012).

    CAS  PubMed  Google Scholar 

  6. Longobardi, L. E., Liu, L., Grimme, S. & Stephan, D. W. Stable borocyclic radicals via frustrated Lewis pair hydrogenations. J. Am. Chem. Soc. 138, 2500–2503 (2016).

    CAS  PubMed  Google Scholar 

  7. Sun, Q. et al. Borole/borapyramidane relationship. J. Am. Chem. Soc. 144, 7815–7821 (2022).

    CAS  PubMed  Google Scholar 

  8. Kirkpatrick, P. & Ellis, C. Chemical space. Nature 432, 823–823 (2004).

    CAS  Google Scholar 

  9. Dobson, C. M. Chemical space and biology. Nature 432, 824–828 (2004).

    CAS  PubMed  Google Scholar 

  10. Grams, R. J. et al. The rise of boron-containing compounds: advancements in synthesis, medicinal chemistry, and emerging pharmacology. Chem. Rev. 124, 2441–2511 (2024).

    CAS  PubMed  Google Scholar 

  11. Graham, B. J., Windsor, I. W., Gold, B. & Raines, R. T. Boronic acid with high oxidative stability and utility in biological contexts. Proc. Natl Acad. Sci. USA 118, e2013691118 (2021).

    CAS  PubMed  PubMed Central  Google Scholar 

  12. Lyu, H., Kevlishvili, I., Yu, X., Liu, P. & Dong, G. Boron insertion into alkyl ether bonds via zinc/nickel tandem catalysis. Science 372, 175–182 (2021).

    CAS  PubMed  Google Scholar 

  13. Yuan, K. & Ingleson, M. J. Haloboration of o-alkynyl phenols generates halogenated bicyclic-boronates. Angew. Chem. Int. Ed. 62, e202301463 (2023).

    CAS  Google Scholar 

  14. Wood, T. K., Piers, W. E., Keay, B. A. & Parvez, M. 9-Boraanthracene derivatives stabilized by N-heterocyclic carbenes. Angew. Chem. Int. Ed. 48, 4009–4012 (2009).

    CAS  Google Scholar 

  15. Zhou, Z., Wakamiya, A., Kushida, T. & Yamaguchi, S. Planarized triarylboranes: stabilization by structural constraint and their plane-to-bowl conversion. J. Am. Chem. Soc. 134, 4529–4532 (2012).

    CAS  PubMed  Google Scholar 

  16. Farrell, J. M. et al. Tunable low-LUMO boron-doped polycyclic aromatic hydrocarbons by general one-pot C–H borylations. J. Am. Chem. Soc. 141, 9096–9104 (2019).

    CAS  PubMed  Google Scholar 

  17. Scholz, A. S. et al. BNB-doped phenalenyls: modular synthesis, optoelectronic properties, and one-electron reduction. J. Am. Chem. Soc. 142, 11072–11083 (2020).

    CAS  PubMed  Google Scholar 

  18. Deng, C. L. et al. Air- and photo-stable luminescent carbodicarbene-azaboraacenium ions. Nat. Chem. 16, 437–445 (2024).

    CAS  PubMed  Google Scholar 

  19. Su, W. et al. Copper-catalysed asymmetric hydroboration of alkenes with 1,2-benzazaborines to access chiral naphthalene isosteres. Nat. Chem. 16, 1312–1319 (2024).

    CAS  PubMed  Google Scholar 

  20. Schacht, W. & Kaufmann, D. Erste Synthese eines Benzodihydroborets. J. Organomet. Chem. 339, 33–39 (1988).

    CAS  Google Scholar 

  21. Hergel, A., Pritzkow, H. & Siebert, W. Synthesis and reactivity of a naphtho[l,8‐bc]boret. Angew. Chem. Int. Ed. 33, 1247–1248 (1994).

    Google Scholar 

  22. Guven, Z. et al. Reactions of a four-membered borete with carbon, silicon, and gallium donor ligands: fused and spiro-type boracycles. Chem. Eur. J. 28, e202200673 (2022).

    PubMed  Google Scholar 

  23. Pues, C., Baum, G., Massa, W. & Berndt, A. Structure of a homoborirene. Z. Naturforsch. 43b, 275–279 (1988).

    Google Scholar 

  24. Zhao, H. & Gabbaï, F. P. A bidentate Lewis acid with a telluronium ion as an anion-binding site. Nat. Chem. 2, 984–990 (2010).

    CAS  PubMed  Google Scholar 

  25. Araneda, J. F., Neue, B., Piers, W. E. & Parvez, M. Photochemical synthesis of a ladder diborole: a new boron-containing conjugate material. Angew. Chem. Int. Ed. 51, 8546–8550 (2012).

    CAS  Google Scholar 

  26. Wang, J., Zhu, S., Ma, W., Lin, Z. & Ye, Q. BN-butafulvenes and their application in the synthesis of highly substituted BN-9,1-naphthalenes. Angew. Chem. Int. Ed. 62, e202219062 (2023).

    CAS  Google Scholar 

  27. Arif, A. M., Cowley, A. H., Pakulski, M. & Power, J. M. Diphospha- and diarsa-diboretanes. Four-membered rings containing boron and phosphorus or arsenic. J. Chem. Soc. Chem. Commun. 11, 889–890 (1986).

    Google Scholar 

  28. Edel, K. et al. The Dewar isomer of 1,2-dihydro-1,2-azaborinines: isolation, fragmentation, and energy storage. Angew. Chem. Int. Ed. 57, 5296–5300 (2018).

    CAS  Google Scholar 

  29. Ishida, Y., Donnadieu, B. & Bertrand, G. Stable four-π-electron, four-membered heterocyclic cations and carbenes. Proc. Natl Acad. Sci. USA 103, 13585–13588 (2006).

    CAS  PubMed  PubMed Central  Google Scholar 

  30. Ian, M. & Peter, P. Formation of the novel neopentylidenoborane Me3Si(tBu)N=B=CHtBu from the tantalum neopentylidene complex [(η-C5H5)Cl2Ta=CHtBu] by metathesis. J. Chem. Soc. Chem. Commun. 3, 183–185 (1988).

  31. Ito, M., Tokitoh, N. & Okazaki, R. 1,3,2,4-Diselenastannaboretane, a novel selenium-containing four-membered boracycle: synthesis, structure and thermal cycloreversion into a selenoxoborane. Chem. Commun. 22, 2495–2496 (1998).

    Google Scholar 

  32. Leifert, D. & Studer, A. The persistent radical effect in organic synthesis. Angew. Chem. Int. Ed. 59, 74–108 (2020).

    CAS  Google Scholar 

  33. Parsaee, F. et al. Radical philicity and its role in selective organic transformations. Nat. Rev. Chem. 5, 486–499 (2021).

    CAS  PubMed  Google Scholar 

  34. Chan, A. Y. et al. Metallaphotoredox: the merger of photoredox and transition metal catalysis. Chem. Rev. 122, 1485–1542 (2022).

    CAS  PubMed  Google Scholar 

  35. Capaldo, L., Ravelli, D. & Fagnoni, M. Direct photocatalyzed hydrogen atom transfer (HAT) for aliphatic C–H bonds elaboration. Chem. Rev. 122, 1875–1924 (2022).

    CAS  PubMed  Google Scholar 

  36. Golden, D. L., Suh, S.-E. & Stahl, S. S. Radical C(sp3)–H functionalization and cross-coupling reactions. Nat. Rev. Chem. 6, 405–427 (2022).

    CAS  PubMed  PubMed Central  Google Scholar 

  37. Parrish, J. D. & Little, R. D. Diradicals in synthesis. in Radicals in Organic Synthesis (eds Renaud, P. & Sibi, M. P.) 383–406 (Wiley-VCH, 2001).

  38. Abe, M. Diradicals. Chem. Rev. 113, 7011–7088 (2013).

    CAS  PubMed  Google Scholar 

  39. Hinz, A., Bresien, J., Breher, F. & Schulz, A. Heteroatom-based diradical(oid)s. Chem. Rev. 123, 10468–10526 (2023).

    CAS  PubMed  Google Scholar 

  40. Kaim, W., Hosmane, N. S., Záliš, S., Maguire, J. A. & Lipscomb, W. N. Boron atoms as spin carriers in two- and three-dimensional systems. Angew. Chem. Int. Ed. 48, 5082–5091 (2009).

    CAS  Google Scholar 

  41. Maiti, A. et al. Anionic boron- and carbon-based hetero-diradicaloids spanned by a p-phenylene bridge. J. Am. Chem. Soc. 143, 3687–3692 (2021).

    CAS  PubMed  Google Scholar 

  42. Walton, J. C. et al. EPR studies of the generation, structure, and reactivity of n-heterocyclic carbene borane radicals. J. Am. Chem. Soc. 132, 2350–2358 (2010).

    CAS  PubMed  Google Scholar 

  43. Zhou, N., Yuan, X. A., Zhao, Y., Xie, J. & Zhu, C. Synergistic photoredox catalysis and organocatalysis for inverse hydroboration of imines. Angew. Chem. Int. Ed. 57, 3990–3994 (2018).

    CAS  Google Scholar 

  44. Xia, P. J. et al. Photoinduced single-electron transfer as an enabling principle in the radical borylation of alkenes with NHC-borane. Angew. Chem. Int. Ed. 59, 6706–6710 (2020).

    CAS  Google Scholar 

  45. Xu, W., Jiang, H., Leng, J., Ong, H. W. & Wu, J. Visible-light-induced selective defluoroborylation of polyfluoroarenes, gem-difluoroalkenes, and trifluoromethylalkenes. Angew. Chem. Int. Ed. 59, 4009–4016 (2020).

    CAS  Google Scholar 

  46. Shu, C., Noble, A. & Aggarwal, V. K. Metal-free photoinduced C(sp3)–H borylation of alkanes. Nature 586, 714–719 (2020).

    CAS  PubMed  Google Scholar 

  47. Kim, J. H. et al. A radical approach for the selective C–H borylation of azines. Nature 595, 677–683 (2021).

    CAS  PubMed  Google Scholar 

  48. Miao, Y.-Q. et al. A general photo-induced wide-scope regioselective hydroboration of alkenes without using a photocatalyst or an external initiator. Green Chem. 24, 7113–7121 (2022).

    CAS  Google Scholar 

  49. Peng, T. Y., Zhang, F. L. & Wang, Y. F. Lewis base-boryl radicals enabled borylation reactions and selective activation of carbon–heteroatom bonds. Acc. Chem. Res. 56, 169–186 (2023).

    CAS  PubMed  Google Scholar 

  50. Tian, Y.-M., Guo, X.-N., Braunschweig, H., Radius, U. & Marder, T. B. Photoinduced borylation for the synthesis of organoboron compounds. Chem. Rev. 121, 3561–3597 (2021).

    CAS  PubMed  Google Scholar 

  51. Grosskopf, J., Kratz, T., Rigotti, T. & Bach, T. Enantioselective photochemical reactions enabled by triplet energy transfer. Chem. Rev. 122, 1626–1653 (2022).

    CAS  PubMed  Google Scholar 

  52. Molloy, J. J. et al. Boron-enabled geometric isomerization of alkenes via selective energy-transfer catalysis. Science 369, 302–306 (2020).

    CAS  PubMed  Google Scholar 

  53. Kleinmans, R. et al. Intermolecular [2π+2σ]-photocycloaddition enabled by triplet energy transfer. Nature 605, 477–482 (2022).

    CAS  PubMed  Google Scholar 

  54. Becker, M. R., Wearing, E. R. & Schindler, C. S. Synthesis of azetidines via visible-light-mediated intermolecular [2+2] photocycloadditions. Nat. Chem. 12, 898–905 (2020).

    CAS  PubMed  Google Scholar 

  55. Blum, T. R., Miller, Z. D., Bates, D. M., Guzei, I. A. & Yoon, T. P. Enantioselective photochemistry through Lewis acid–catalyzed triplet energy transfer. Science 354, 1391–1395 (2016).

    CAS  PubMed  PubMed Central  Google Scholar 

  56. Doan, T. H. et al. Methylene bridging effect on the structures, Lewis acidities and optical properties of semi-planar triarylboranes. Chem. Eur.J. 27, 1736–1743 (2021).

    CAS  PubMed  Google Scholar 

  57. Munster, N., Parker, N. A., van Dijk, L., Paton, R. S. & Smith, M. D. Visible light photocatalysis of 6π heterocyclization. Angew. Chem. Int. Ed. 56, 9468–9472 (2017).

    Google Scholar 

Download references

Acknowledgements

We thank H. H.-Y. Sung and I. Williams for single-crystal X-ray diffraction analyses, and Y. Zuo for quantum efficiency measurement. We acknowledge the start-up funding (project no. R9804 to Y.Q.) from the Hong Kong University of Science and Technology (HKUST), start-up funding (project no. 4933621 to H.L.) from The Chinese University of Hong Kong (CUHK), Early Career Scheme from Research Grants Council of Hong Kong (project nos. 26307123 to Y.Q. and 24307423 to H.L.), General Research Fund from Research Grants Council of Hong Kong (project no. HKUST16300021 to Z.L.), Young Scholar Fund (project no. 22301254 to Y.Q.) from National Natural Science Foundation of China, and the Croucher Foundation for financial support.

Author information

Authors and Affiliations

  1. Department of Chemistry, The Hong Kong University of Science and Technology, Hong Kong SAR, China

    Xinmou Wang, Peiqi Zhang, Zhiyi Yang, Zhenyang Lin & Yangjian Quan

  2. Department of Chemistry, The Chinese University of Hong Kong, Hong Kong SAR, China

    Weixuan Sun & Hairong Lyu

Authors
  1. Xinmou Wang
    View author publications

    Search author on:PubMed Google Scholar

  2. Peiqi Zhang
    View author publications

    Search author on:PubMed Google Scholar

  3. Zhiyi Yang
    View author publications

    Search author on:PubMed Google Scholar

  4. Weixuan Sun
    View author publications

    Search author on:PubMed Google Scholar

  5. Hairong Lyu
    View author publications

    Search author on:PubMed Google Scholar

  6. Zhenyang Lin
    View author publications

    Search author on:PubMed Google Scholar

  7. Yangjian Quan
    View author publications

    Search author on:PubMed Google Scholar

Contributions

X.W., H.L. and Y.Q. conceived and designed the experiments. X.W., Z.Y. and W.S. performed experiments. P.Z. and Z.L. performed DFT calculations. X.W., P.Z., H.L., Z.L. and Y.Q. wrote the paper. H.L., Z.L. and Y.Q. directed the research.

Corresponding authors

Correspondence to Hairong Lyu, Zhenyang Lin or Yangjian Quan.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Chemistry thanks the anonymous reviewers for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–31, Supplementary Table 1–13, experimental details, computational details, data and spectra.

Supplementary Data 1

Crystallographic data for compound 2; CCDC reference 2352027.

Supplementary Data 2

Crystallographic data for compound 22S; CCDC reference 2352030.

Supplementary Data 3

Crystallographic data for compound 55; CCDC reference 2352031.

Supplementary Data 4

Crystallographic data for compound 56; CCDC reference 2352034.

Supplementary Data 5

Crystallographic data for compound 62; CCDC reference 2352033.

Supplementary Data 6

Crystallographic data for compound 70; CCDC reference 2352035.

Supplementary Data 7

The xyz coordinates of DFT calculation results.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Wang, X., Zhang, P., Yang, Z. et al. Synthesis of strained, air-stable boracycles via boron–carbon-centred diradicals. Nat. Chem. 17, 663–671 (2025). https://doi.org/10.1038/s41557-025-01807-x

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue date:

  • DOI: https://doi.org/10.1038/s41557-025-01807-x

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing