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Iron-catalysed regioselective thienyl C–H/C–H coupling

Nature Catalysis volume 4, pages 631–638 (2021)Cite this article

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Abstract

Regioselective thienyl–thienyl coupling is arguably one of the most important transformations for organic electronic materials. A prototype of ideal organic synthesis to couple two thienyl groups by cutting two C–H bonds requires formal removal of two hydrogen atoms with an oxidant, which often limits the synthetic efficiency and versatility for oxidation-sensitive substrates (for example, donor and hole-transporting materials). Here, we found that diethyl oxalate, used together with AlMe3, acts as a two-electron acceptor in an iron-catalysed C–H activation. We describe the regioselective thienyl C–H/C–H coupling with an iron(III) catalyst, a trisphosphine ligand, AlMe3 and diethyl oxalate under mild conditions. The efficient catalytic system accelerated by ligand optimization polymerizes thiophene-containing monomers into homo- and copolymers bearing a variety of electron-donative π motifs. The findings suggest the versatility of iron catalysis for the synthesis of functional polymers, for which the potential of this ubiquitous metal has so far not been fully appreciated.

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Fig. 1: Iron-catalysed regioselective thienyl C–H/C–H coupling enabled by the TP/AlMe3/DEO system.
Fig. 2: Investigation of reaction parameters.
Fig. 3: Investigation of the ligand effect on polycondensation.
Fig. 4: Scope of iron-catalysed regioselective thienyl C–H/C–H homocoupling.
Fig. 5: Scope of iron-catalysed regioselective thienyl C–H/C–H polycondensation.

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Data availability

All of the data supporting the findings of this study, including experimental procedures and compound characterization, are available within the paper and its Supplementary Information, or from the authors upon reasonable request.

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Acknowledgements

We thank Mitsubishi Chemical Corporation for partial financial support. We thank S. Kobayashi and T. Yasukawa for generous help with the ICP analysis of the contents of metal residues. This research is supported by MEXT KAKENHI grant number 19H05459 (to E.N.) and JSPS KAKENHI grant number 19K15555 (to R.S.). T.D. thanks JSPS for the predoctoral fellowship.

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  1. Laurean Ilies

    Present address: Department of Chemistry, The University of Tokyo, Tokyo, Japan

Authors and Affiliations

  1. Department of Chemistry, The University of Tokyo, Tokyo, Japan

    Takahiro Doba, Wataru Sato, Rui Shang & Eiichi Nakamura

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Contributions

E.N. and R.S. guided the research and wrote the manuscript. T.D. performed the experiments to develop the reaction and study the scope, application and mechanism. L.I. contributed to the optimization of dimerization. W.S. helped with polymer design, purification and characterization of properties. All authors contributed to designing the experiments, analysing the data and editing the manuscript.

Corresponding authors

Correspondence to Rui Shang or Eiichi Nakamura.

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Competing interests

E.N., R.S., T.D. and W.S. are inventors on Japanese patent application number 2020-130678, submitted by The University of Tokyo, which covers synthetic methods described in this manuscript. L.I. declares no competing interests.

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Peer review information Nature Catalysis thanks Filipe Vilela and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Methods, Discussion, Tables 1–6 and Figs. 1–13.

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Doba, T., Ilies, L., Sato, W. et al. Iron-catalysed regioselective thienyl C–H/C–H coupling. Nat Catal 4, 631–638 (2021). https://doi.org/10.1038/s41929-021-00653-7

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