Catalytic reactions for C–H functionalizations are very commonly used in organic synthesis. For example, arene C−H borylations and C−H silylations can be employed. Catalytic arene C−H functionalizations that install more electropositive main group elements are less well-developed.

Stuart A. Macgregor, Heriot-Watt University, Edinburgh, UK, and University of St Andrews, UK, Michael J. Ingleson, University of Edinburgh, UK, and colleagues have developed a method for the transition-metal-free catalytic C–H zincation or C–H alumination of heteroarenes using β-diketiminate metal complexes (general reactions pictured below). Almost all C–H metalation routes to form Al/Zn organometallics require stoichiometric, strong Brønsted bases, but the team’s new reaction requires only sub-stoichiometric amounts of an amine/ammonium salt (Et₃N/Et₃NH⁺).

 

They reacted NacNacZnH or NacNacAlMe₂ (NacNac = {(2,6-ⁱPr₂C₆H₃)N(CH₃)C}₂CH) with different heteroarenes such as thiophenes, furans, benzothiophenes, pyrroles, or indoles in the presence of either [Et₃NH][B(Ar^CF3)₄] (B(Ar^CF3)₄ = B{3,5-C₆H₃(CF₃)₂}₄) or [Et₃NH][B(C₆F₅)₄].

The desired products were obtained in moderate to excellent yields. The approach couples the endergonic C–H metalation with an exergonic dehydrocoupling. The only byproducts are H₂ or CH₄. According to the team, the approach might be transferable to other main group metals and ligand sets.

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• Transition Metal‐Free Catalytic C−H Zincation and Alumination,
  Milan Kumar Bisai, Justyna Losiewicz, Lia Sotorrios, Gary Nichol, Andrew Dominey, Michael Cowley, Stephen Thomas, Stuart Macgregor, Michael Ingleson,
  Angew. Chem. Int. Ed. 2024.
  https://doi.org/10.1002/anie.202404848