Synthesis and Elaboration of Medium-Sized Ring Building Blocks Prepared via Cascade Ring Expansion Reactions

A general approach is described for the synthesis and elaboration of medium-sized ring mono- and difunctionalized 8- or 9-membered ring lactone building blocks. The lactones are prepared via cascade ring expansion reactions and elaborated via Suzuki-Miyaura cross coupling and various <i>N</i>-functionalization reactions. This enables efficient access to diverse, medium-sized ring building blocks in a synthetically challenging and under-represented area of the pharmaceutical chemical space.