Carboxylic acids are a class of chemicals with abundant sources, structural diversity, stability, and cost- effectiveness, representing the second largest class of commercially available organic building blocks after amines. The past decade has witnessed the rapid development of photoinduced radical decarboxylative transformation of alkyl carboxylic acids. However, the progress in the decarboxylative transformation of aryl carboxylic acids is slow, mianly due to the relatively reluctant decarboxylation of O-centered aryl carboxylate radicals and the subsequent very reactive aryl radicals, suffering severe competitive pathways. In the latest five years, ligand-to-metal charge transfer (LMCT)-driven photoinduced metal- catalyzed/mediated decarboxylative transformation of aryl carboxylic acids (carboxylates) has gained some achievements, such as copper-catalyzed/mediated halogenation, hydroxylation, sulfoximination, borylation, halosulfonylation, thianthrenation, allylation, thiolation and hydrogenation, iron-catalyzed thiolation and bromination. Further development is highly expected to realize new types of reactions through smart design and control of reaction conditions. For instance, the merger of LMCT and transition metal catalysis might provide an opportunity to achieve the decarboxylative cross-coupling of aryl carboxylic acids.

Key words: ligand-to-metal charge transfer (LMCT)-driven, photoinduced, metal catalysis, aryl carboxylic acid, decarboxylative transformation, radical reaction