Research Progress of Amino Acids as Transient Directing Groups in C—H Bond Activation Reactions

In recent years, the transient directing group (TDG)-based strategy of C-H activation has attracted significant attention.Compared with the typical C-H activation reactions, TDG-assisted C-H activation does not require external pre-installation and post-removal steps of directing groups, which significantly improve the atom and step economy.Amino acid-based TDGs for C-H activation have achieved significant successes among the known TDGs.Amino acids have the advantages including low cost, widely existing and diverse structures.The site selectivity of C-H activation can be controlled by using α-or β-amino acids.By using the inherent chirality of amino acids, the stereo-selectivity of reactions can be realized.The research progress of transition-metal-catalyzed C-H bond activation and functionalization with amino acids as TDGs in recent years is summarized, which is classified according to the type of amino acids for C-H activation reactions of various substrates.Finally, the limitations of previous works and perspectives on this cutting-edge area are also described.