Recent advances in carbon atom addition for ring-expanding single-atom skeletal editing

Ring architecture not only influences molecular properties, spatial arrangement, and scaffold rigidity but also determines molecular function and regulation. Compared with the traditional construction of ring frameworks that often requires starting from scratch, the development of methods for directly editing the ring skeleton lags far behind, which is largely attributed to the inertness of chemical bonds that constitute the frameworks. This review focuses on recent progress (post 2021) in the development of ring-expanding single-atom skeletal editing via ring expansion or carbon-atom insertion, enabling a more efficient and accurate synthetic strategy for the synthesis of important scaffolds in drug discovery and beyond, as well as its application in late-stage molecular transformations and streamlined synthesis of bioactive molecules.