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

Abstract

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.