The selective activation of inert C–H bonds has emerged as a promising tool for avoiding the use of wasteful traditional coupling reactions. Oxidative coupling of simple aromatics allows for a cost-effective synthesis of biaryls. However, utilization of this technology is severely hampered by poor regioselectivity and by the limited stability of state-of-the-art homogeneous Pd catalysts. Here, we show that confinement of cationic Pd in the pores of a zeolite allows for the shape-selective C–H activation of simple aromatics without a functional handle or electronic bias. For instance, out of six possible isomers, 4,4′-bitolyl is produced with high shape selectivity (80%) in oxidative toluene coupling on Pd-Beta. Not only is a robust, heterogeneous catalytic system obtained, but this concept is also set to control the selectivity in transition-metal-catalysed arene C–H activation through spatial confinement in zeolite pores.
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The findings of this study are available in the main text or the supplementary materials. Atomic coordinates of optimized computational models and initial and final configurations of molecular dynamics trajectories are supplied in a Supplementary Data file. All data are available from the authors upon reasonable request.
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We thank N. Van Velthoven for discussion. The XAS experiments were performed on beamline BM26A at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. This work was funded by grants from FWO (1S17620N for J.V.; project G0D0518N, G0F2320N, G078118N; EoS BioFACT), the Flemish government (CASAS Methusalem programme for D.D.V.). V.V.S., J.H. and M.B. acknowledge the Research Board of Ghent University (BOF) and funding from the European Union’s Horizon 2020 research and innovation programme (consolidator ERC grant agreement No. 647755 – DYNPOR (2015-2020)). The computational resources and services used were provided by Ghent University (Stevin Supercomputer Infrastructure) and the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO). A.S. and A.B. acknowledge the funding from Russian Science Foundation (joint RSF-FWO grant No. 20-43-01015). A.K. and G.M. acknowledge the financial support from the Slovenian Research Agency (research core funding No. P1-0021 and project No. N1-0079).
J.V., P.T. and D.D.V. filed a patent application GB1804905.6 prior to an international patent application PCT/EP2019/057746.
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Vercammen, J., Bocus, M., Neale, S. et al. Shape-selective C–H activation of aromatics to biarylic compounds using molecular palladium in zeolites. Nat Catal 3, 1002–1009 (2020). https://doi.org/10.1038/s41929-020-00533-6