Chemoselective Cross-Coupling between Two Different and Unactivated C(aryl)–O Bonds Enabled by Chromium Catalysis

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We report here the first example of cross-coupling between two different and unactivated C(aryl)–O bonds with chromium catalysis. The combination of a low-cost Cr(II) salt, 4,4′-di- tert -butyl-2,2′-dipyridyl (dtbpy) as the ligand, and magnesium as the reductant shows high reactivity in promoting the reductive cross-coupling of aryl methyl ether derivatives with aryl esters by cleavage and coupling of two different C(aryl)–O bonds under mild conditions. The formation of active low-valent Cr species by reduction of CrCl 2 with Mg can be considered, which prefers to initially activate the C(aryl)–O bond of phenyl methyl ether with the chelation help of dtbpy and an o -imine auxiliary. The subsequent consecutive reduction, second C(aryl)–O activation, and reductive elimination allow for the achievement of selective cross-coupling of C(aryl)–O/C(aryl)–O bonds.