Successive Ring Expansion Strategies for the Synthesis of Macrocycles and Medium-Sized Rings.

Macrocycles and medium-sized rings have myriad uses in various applied fields. Effective and scalable methods for their synthesis are therefore of high value. Ring expansion reactions are important in this context, as they allow larger rings to be "grown" from more easily accessible smaller ring systems, while avoiding inefficient end-to-end cyclization reactions. This review is focused on successive ring expansion strategies, in which two (or more) ring expansion steps have been performed in sequence to enable the synthesis of functionalized macrocycles and medium-sized rings.