Recent Advances in Palladium-Catalyzed Cycloaddition Reactions for the Synthesis of Eight-Membered Rings.

Eight-membered ring skeletons are central to numerous pharmaceutical molecules and biologically active substances. Recent years have witnessed remarkable progress in the construction of these challenging ring systems. Among the various synthetic strategies, transition metal catalysis, particularly palladium-catalyzed cycloaddition reactions, has emerged as an efficient and reliable methodology for generating diverse eight-membered ring frameworks. This review provides a detailed classification and comprehensive summary of palladium-catalyzed cycloaddition modes for constructing eight-membered ring compounds, specifically focusing on the [4 + 4], [5 + 3], and [6 + 2] cycloaddition strategies. This article aims to highlight the latest advancements in the synthesis of eight-membered ring compounds via palladium-catalyzed cycloaddition reactions, thereby stimulating and promoting further exploration of innovative synthetic approaches in this field.