Chemoselective Cross-Coupling between Two Different and Unactivated C(aryl)–O Bonds Enabled by Chromium Catalysis
Jinghua Tang, Liu Leo Liu, Shangru Yang, Xuefeng Cong, Meiming Luo, Xiaoming Zeng
Abstract
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.