C–C or C–O coupling reaction of two aryls is typically carried out using transition metal catalysts (Cu or Pd). For example, Ullmann aryl ether synthesis (Cu mediated) is one of the most reliable methods used for the preparation of this chemical motif.^[1] Other routes require preparation of multi-step staring compounds to obtain halogenated or boron aryl derivatives to carry out the C-O coupling with phenols; here again palladium- and/or copper are present as catalyst.^[2,3] Diarylethers are important scaffold in pharmaceuticals and natural products, therefore an alternative, direct, and more sustainable access to such structural features is highly desired. In the last years, Waldvogel research group has proven that the anodic C-C homo and cross coupling of phenols, using boron-doped diamond electrodes (BDDE) and hexafluoroisopropanol (HFIP), is a robust and reliable method that can be used in multi-gram scale and with a green chemistry vision.^[4] In this contribution, is shown the dramatic effect of tertiary amines, which modify the reaction pathway and favor the C-O phenol homo coupling, instead of the classical C-C phenol homo coupling. With this small change in the electrochemical protocol of the anodic oxidation of phenols now it is possible to obtain diarylethers in good yields directly form the phenols.

References.

[1] Evano, G.; Blanchard, N.; Toumi, M. Chem. Rev. 2008, 108, 3054. [2] Fan, M.; Zhou, W.;Jiang, Y.; Ma, D. Angew. Chem., Int. Ed. 2016, 55, 6211. [3] Salvi, L.; Davis, N. R.; Ali, S. Z.; Buchwald, S. L. Org.Lett. 2012, 14, 170. [4] A. Wiebe, B. Riehl, S. Lips, R. Franke, S. R. Waldvogel, Sci. Adv. 2017, 3, eaao3920/1–7.

Acknowledgements.

S.R.W. thanks the DFG (Wa1276/14-1) for financial support and the research network ELYSION,. B. A. F.-U. thanks the Impulsfonds Pre-HIKE (JGU Mainz), PASPA-DGAPA UNAM, and CONACYT-Mexico for the support.