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

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 CrCl2 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.