Recent advances in transition metal-catalyzed alkyne annulations: applications in organic synthesis.

Transition metal-catalyzed alkyne annulation has emerged as a powerful strategy for constructing diverse cyclic frameworks with high efficiency and selectivity. This methodology exploits the unique reactivity of transition metals to activate alkynes, enabling the formation of carbocycles and heterocycles. Recent advances-including cooperative catalysis, dual-catalyst systems, and electrochemical transformations-have significantly broadened the scope of achievable structures. The development of novel catalysts and optimized conditions has facilitated the synthesis of complex architectures relevant to pharmaceuticals, natural products, and materials science. Mechanistic studies have enhanced the understanding of reaction pathways, improving control over regio- and stereoselectivity. Incorporating green chemistry principles has further increased the sustainability of these protocols. This review highlights key mechanistic insights, synthetic applications, and future directions in the evolving field of transition metal-catalyzed alkyne annulations.