Recent advances in catalytic synthesis of medium-ring lactones and their derivatives

Medium-sized lactones are widely found in various natural products and pharmaceuticals. However, the efficient synthesis of these structures remains as a challenging topic in organic synthesis due to the disfavored kinetic and thermodynamic factors. The recent development of palladium-catalysed dipolar cycloaddition, electrophilic halolactonization, NHC-catalysed cyclization, ring expansion reactions, transition metal-catalysed coupling reactions, etc. provides a powerful platform for the construction of these important scaffolds. In light of the ever-increasing significance of medium-sized lactones across a range of chemical sciences, the present review aims to summarize the main achievements in the field of catalytic synthesis of medium-ring lactones with emphasis on reaction mechanism and scope as well as synthetic application.