Abstract
Iron is inexpensive, non-toxic and the most abundant transition metal in the Earth’s crust, rendering iron-catalysed C–H activations attractive yet particularly challenging. Despite major advances, iron-catalysed C–H activations have been linked to high reaction temperatures or the use of reactive Grignard reagents. Here we present iron-catalysed ketimine C–H activations at ambient reaction temperature with the help of blue light in the absence of additives, utilizing easily accessible cis-[Fe(H)2(dppe)2] (where dppe is 1,2-bis(diphenylphosphino)ethane) as a single component precatalyst. Mild reaction conditions, high atom economy and the lack of Grignard reagents are distinguishing features of the iron-catalysed C–H alkenylation manifold. Detailed mechanistic investigations by deuterium labelling, isolation of organometallic intermediates and in operando light-emitting diode nuclear magnetic resonance spectroscopy revealed the role of the light and an oxidative addition to an iron(0) complex as the modus operandi for the C–H activation.
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Data availability
The data supporting the findings of this study are available within the article and its Supplementary Information, or from the authors on reasonable request. Crystal structure data have been deposited at the Cambridge Crystallographic Data Centre (CCDC nos. 2192211–2192227 and 2280102–2280104), and crystallographic data are provided in Supplementary Information. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk. Spectroscopic and kinetic data that support the findings of this study are freely available in Zenodo data repository, with https://doi.org/10.5281/zenodo.10138296.
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Acknowledgements
Generous support by the DFG (SPP 1807 Gottfried-Wilhelm-Leibniz award to L.A.), the European Union’s Horizon 2020 research and innovation programme (Marie Skłodowska-Curie grant agreement no. 895404 to A.M.M. and ERC advanced grant agreement no. 101021358 to L.A.) and FCI Kekulé Fellowship no. 110091 (T.v.M.) is gratefully acknowledged. We thank C. Golz (Göttingen University) for assistance with the X-ray diffraction analysis and I. Maksso for measuring inductively coupled plasma mass spectrometry solutions.
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A.M.M. unravelled the photo-promoted iron-catalysed C–H activation of imines, conducted the mechanistic studies, explored the substrate scope assisted by T.v.M. and M.S., and wrote the paper with revisions provided by the other authors. M.S. performed the Grignard studies. L.A. conceived and directed the research programme and revised the paper.
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Supplementary Methods, Figs. 1–52, Tables 1–6 and References.
Supplementary Data 1
CIF file of the crystal structure of compound 4a.
Supplementary Data 2
CIF file of the crystal structure of compound 4b.
Supplementary Data 3
CIF file of the crystal structure of compound 4c.
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CIF file of the crystal structure of compound 4d.
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CIF file of the crystal structure of compound 4e.
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CIF file of the crystal structure of compound 4f.
Supplementary Data 7
CIF file of the crystal structure of compound 4g.
Supplementary Data 8
CIF file of the crystal structure of compound 5a.
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CIF file of the crystal structure of compound 5b.
Supplementary Data 10
CIF file of the crystal structure of compound 5c.
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CIF file of the crystal structure of compound 6a.
Supplementary Data 12
CIF file of the crystal structure of compound 6b.
Supplementary Data 13
CIF file of the crystal structure of compound 6c.
Supplementary Data 14
CIF file of the crystal structure of compound 8.
Supplementary Data 15
CIF file of the crystal structure of compound 10a.
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CIF file of the crystal structure of compound 10b.
Supplementary Data 17
CIF file of the crystal structure of compound E-3aa.
Supplementary Data 18
CIF file of the crystal structure of compound E-3aa″.
Supplementary Data 19
CIF file of the crystal structure of compound E-3aj.
Supplementary Data 20
CIF file of the crystal structure of compound Z-3ea.
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Messinis, A.M., von Münchow, T., Surke, M. et al. Room temperature photo-promoted iron-catalysed arene C–H alkenylation without Grignard reagents. Nat Catal 7, 273–284 (2024). https://doi.org/10.1038/s41929-023-01105-0
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DOI: https://doi.org/10.1038/s41929-023-01105-0