Reductive Cross-Coupling between Unactivated C(aryl)–N and C(aryl)–O Bonds by Chromium Catalysis Using a Bipyridyl Ligand
Jinghua Tang, Fan Fei, Xuefeng Cong, Lixing Zhao, Meiming Luo, Xiaoming Zeng
Abstract
Reductive cross-coupling between two chemically inert bonds remains a great challenge in synthetic chemistry. We report here the reductive cross-coupling between unactivated C(aryl)–N and C(aryl)–O bonds that was achieved by chromium catalysis. The simple and inexpensive CrCl2 salt, combined with important bipyridyl ligand and magnesium reductant, shows high reactivity in the successive cleavage of C(aryl)–N bonds of aniline derivatives and C(aryl)–O bonds of aryl esters, allowing the cross-coupling of these two unactivated and different bonds to occur in a reductive fashion to form a C(aryl)–C(aryl) bond. Mechanistic studies by deuterium-labeling experiments indicate that the C(aryl)–N bonds in anilines are preferentially cleaved by reactive Cr species, in which the ligation of bipyridyl with Cr by adopting a coordination model in 1:1 ratio can be considered.