Copper-Catalyzed or -Mediated C-H Bond Functionalizations Assisted by Bidentate Directing Groups

Copper salts, which are abundant, relatively inexpensive and possess low toxicity, have long been used as versatile catalysts for various reactions in organic synthesis. Recently, the development of Cu-catalyzed or -mediated C-H functionalization reactions has gained significant attention. Since the pioneering work of Daugulis on the introduction of 8-aminoquinoline and picolinic acid auxiliaries as removable directing groups in transition metal-catalyzed C-H bond activations, the combination of copper salts with these bidentate directing groups has emerged as an innovative strategy for the construction of carbon-carbon or carbon-heteroatom bonds through C-H bond cleavage. In addition to the 8-aminoquinoline and picolinamide systems, several other bidentate directing groups including the 2-aminophenyloxazoline group by Yu and Dai and the PIP system by Shi, have been developed as well. This review intends to cover most of the recent advances on copper-catalyzed or -mediated direct sp(2) and sp(3) C-H bond functionalizations assisted by these bidentate directing groups. The major achievements in this area are discussed and catalogued by the type of bonds formed (C-C, C-O, C-N, C-S, C-P etc.). Special attention is paid to the reaction mechanisms. Selected examples of substrates are listed as well. In addition, a personal outlook is given at the end.