2-Pyridone ligands as a design platform for palladium-catalyzed C(sp²)-H functionalization reactions

2-Pyridone ligands have emerged as uniquely powerful promoters in transition-metal-catalyzed C-H functionalization, enabling transformations that are often inaccessible with conventional ligand classes. Despite their growing impact, their role is frequently treated only implicitly within broader ligand surveys. This review provides a focused analysis of 2-pyridone ligands as a distinct ligand design platform, emphasizing how they actively participate in C-H activation. We highlight the mechanistic roles of 2-pyridone ligands in key elementary steps, including concerted metalation-deprotonation, weak and dynamic metal coordination, and stabilization of reactive catalytic intermediates. Particular attention is devoted to structure-function relationships, illustrating how substitution patterns on the 2-pyridone scaffold govern basicity, coordination behavior, reactivity, and selectivity in C(sp²)-H functionalization. By extracting unifying design principles from diverse catalytic systems, this review aims to provide practical guidelines for the rational development of next-generation 2-pyridone ligands, with relevance to C-H functionalization.