Ring‐Expansion Reactions in the Synthesis of Macrocycles and Medium‐Sized Rings

• Published in: Chemistry : a European journal 2017-07, Vol.23 (37), p.8780-8799
• Main Authors: Donald, James R., Unsworth, William P.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical synthesis; Chemistry; Damage; Expansion; macrocycles; medium-sized rings; Nanotechnology; rearrangements; ring enlargement; ring expansion
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201700467

Functionalised macrocycles and medium‐sized rings have applications in a number of scientific fields, ranging from medicinal chemistry and supramolecular chemistry, to catalysis and nanotechnology. However, their value in these areas can be undermined by a simple, but important limitation: large ring systems are very often difficult to make. Traditional end‐to‐end cyclisation reactions of long linear precursors are typically unpredictable and impractical processes, mainly due to unfavourable enthalpic and entropic factors. Most published methods to make large rings focus on minimising the damage inflicted by performing the difficult cyclisation step; in contrast, ring‐expansion reactions enable it to be avoided altogether. In this Review article, it is highlighted how “growing” rings from existing cyclic systems via ring expansion can expedite the efficient, practical and scalable synthesis of macrocycles and medium‐sized rings. The right to grow: In this review, it is highlighted how “growing” rings from existing cyclic systems via ring‐expansion reactions can expedite the efficient, practical and scalable synthesis of important macrocyclic and medium‐sized ring compounds.