Recent Advances in Sonogashira Coupling for the Synthesis of Heterocyclic and Fused Heterocyclic Compounds (2020–2025)

ABSTRACT The Sonogashira cross‐coupling reaction remains one of the most powerful and versatile methodologies for the construction of carbon–carbon bonds in modern organic synthesis. Owing to its exceptional functional group tolerance, mild reaction conditions, and broad substrate scope, this transformation has emerged as a key synthetic tool for the preparation of structurally diverse heterocyclic and fused heterocyclic compounds of significant importance in medicinal chemistry, natural product synthesis, materials science, and pharmaceutical research. In recent years, substantial progress has been achieved in Sonogashira coupling‐enabled heterocycle synthesis through the development of tandem, domino, cascade, and one‐pot protocols that integrate cross‐coupling with cyclization, annulation, carbonylation, hydroamination, electrophilic cyclization, and related transformations. This review summarizes the major advances reported between 2020 and 2025 in the application of Sonogashira coupling reactions toward the synthesis of heterocyclic and fused heterocyclic frameworks. Particular emphasis is placed on the construction of nitrogen‐, oxygen‐, and sulfur‐containing heterocycles, including isoquinolines, pyrimidines, pyrazoles, triazoles, indoles, benzofurans, chromones, coumarins, thiophenes, quinolines, fused polyheterocycles, and other structurally complex scaffolds. Recent developments involving palladium‐free methodologies, copper‐catalyzed systems, recyclable catalysts, microwave‐assisted protocols, carbonylative Sonogashira reactions, and sequential coupling–cyclization strategies are also highlighted. Mechanistic aspects of representative transformations, including regioselective 5‐ exo ‐dig and 6‐ endo ‐dig cyclizations, hydroamination, lactonization, electrophile‐promoted cyclization, and Nicholas‐type reactions, are discussed to illustrate the synthetic versatility of Sonogashira‐derived intermediates. By compiling and critically analyzing recent literature, this review demonstrates the continuing evolution of Sonogashira coupling from a classical cross‐coupling reaction into a multifunctional platform for the rapid assembly of complex heterocyclic architectures. The survey is expected to provide valuable insights for researchers engaged in heterocyclic synthesis, catalyst development, and the design of biologically relevant molecular frameworks.