Efficient construction of complex and high value organic molecules from simple and readily available starting materials is a core objetive of organic synhthesis. In recent years, transition metal-catalyzed C—H bond activation, facilitated by directing groups, has been demonstrated as a powerful strategy for achieving site-selective functionalization. Among various substrates, arylcarboxylic acids have gained significant attention as ideal starting materials due to their structural diversity, high stability, and easy accessibility. Notably, the carboxyl group can serve as a traceless directing group, eliminating the need for additional directing group installation and removal steps, thereby significantly enhancing atomic and step economy. Benefiting from these advantages, transition metal-catalyzed decarboxylative C—H bond mono-functionalization of aryl carboxylic acids has achieved remarkable progress. However, the development of difunctionalization remains underdeveloped, despite its significant synthetic value and application potential in rapidly constructing complex organic structures. This review summarizes the recent advances in traceless carboxyl-directed C—H monofunctionalization and difunctionalization, and discusses the challenges and future directions in this field.

Key words: arylcarboxylic acids, transition metal catalysis, C—H bond activation, traceless directing, difunctionalization