Seven N2- and N3-ligands (L1–L7) were developed for the ligand-assisted CuI-catalyzed coupling reactions of aryl halides with phenols. The structural and electronic effects were studied for various combinations of pyridine and/or imine nitrogen binding sites in the ligands. 2-(1-Pyrazolyl)pyridine (L1) featuring two types of binding sites gave the best results, with yields of up to 90% at 100 °C at a catalyst loading of 10 mol% (CuI/L in 1:1 ratio). A non-radical mechanism, proposed for the L1-promoted coupling reaction, well explained the different effects of electronic nature of the substituent and steric hindrance on phenols and aryl halides.
Keywords: 2-(1-Pyrazolyl)pyridine; CuI; Diaryl ether; Cross coupling; non-radical mechanism
When a peer-reviewed version of this preprint is available in the Beilstein Journals, this information will be updated in the information box above. If no peer-reviewed version is available, please cite this preprint using the following information:
Zhao, Y.; Wang, X.; Kaneyama, R.; Kodama, K.; Hirose, T. Beilstein Arch. 2019, 201994. doi:10.3762/bxiv.2019.94.v1
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