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 alpha- or beta-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.

Automated summary

In recent years, the TDG-based strategy of C-H activation has gained attention due to its improved efficiency compared to typical C-H activation reactions. Amino acids have been successful TDGs in C-H activation, thanks to their low cost and diverse structures. By controlling the site selectivity and stereo-selectivity through alpha- or beta-amino acids, significant progress has been made in transition-metal-catalyzed C-H bond activation and functionalization. This review summarizes the recent research progress, categorizes it based on different amino acid types, and discusses the limitations and future perspectives of this cutting-edge area.