Dibenzofurans are often found in natural products or biologically active compounds. Many contain electron-rich aryl rings. The central five-membered ring of the dibenzofuran skeleton can be closed via C–C bond formation from a diarylether or via C–O bond formation from a biaryl precursor. Forming the key intramolecular C–C bond via C–H functionalization is an interesting approach, but can be challenging for electron-rich substrates.

Gerard P. McGlacken, University College Cork, Ireland, and colleagues have developed an approach for the synthesis of electron-rich dibenzofurans based on a Pd-catalyzed C–H functionalization (pictured below). Generally, such Pd-mediated catalytic transformations require a base, added ligands, and a solvent, but the team used tetraalkylammonium salts, particularly NBu₄OAc, which can act as solvent, ligand, and base in the reaction, together with Pd(OAc)₂ as the catalyst. The reactions were performed at 125 °C.

 

 

The team obtained a range of dibenzofurans, in particular, difficult-to-access electron-rich examples, in good to excellent yields. Overall, the process provides a simple, efficient, and green route to electron-rich dibenzofurans.

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• Access to Electron‐Rich Dibenzofurans through NBu₄OAc Mediated Palladium Catalysis,
  Mark Power, Katrina Mackey, Mark Light, David Jones, Gerard P. McGlacken,
  Eur. J. Org. Chem. 2023.
  https://doi.org/10.1002/ejoc.202300790