Publication

Cycloaddition and Annulation Reactions with Donor‐Acceptor Cyclobutanes

2025

Abstract

Donor‐acceptor (DA) cyclobutanes are emerging as valuable synthetic intermediates due to their ring strain and polarized C─C bonds, which allow for 1,4‐dipolar reactions. This review highlights recent advances in DA cyclobutane reactivity, particularly (4+2) annulation reactions used to construct six‐membered rings. It discusses the development of annulations involving carbon‐, oxygen‐, and nitrogen‐based donor groups, initiated by Lewis acid catalysis, Brønsted acid, and electrocatalysis. Additionally, enantioselective transformations and the challenges associated with diester acceptor motifs and their replacement with monoester groups are presented. Overall, this review provides a comprehensive overview of annulation reactions with donor‐acceptor cyclobutanes and emphasizes their potential in stereoselective syntheses of functionalized carbo‐ and hetero‐cycles embedded in complex natural product frameworks.

Official source

https://infoscience.epfl.ch/entities/publication/686a116d-ee26-483b-b82b-5a6ab144a414

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2025

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/686a116d-ee26-483b-b82b-5a6ab144a414

About this result

Related concepts (32)

Lewis acids and bases

A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid to form a Lewis adduct. For example, NH3 is a Lewis base, because it can donate its lone pair of electrons.

Ring strain

In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are substantially smaller than the idealized value of approximately 109°. Because of their high strain, the heat of combustion for these small rings is elevated. Ring strain results from a combination of angle strain, conformational strain or Pitzer strain (torsional eclipsing interactions), and transannular strain, also known as van der Waals strain or Prelog strain.

Acid catalysis

In acid catalysis and base catalysis, a chemical reaction is catalyzed by an acid or a base. By Brønsted–Lowry acid–base theory, the acid is the proton (hydrogen ion, H+) donor and the base is the proton acceptor. Typical reactions catalyzed by proton transfer are esterifications and aldol reactions. In these reactions, the conjugate acid of the carbonyl group is a better electrophile than the neutral carbonyl group itself. Depending on the chemical species that act as the acid or base, catalytic mechanisms can be classified as either specific catalysis and general catalysis.

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Cycloaddition and Annulation Reactions with Donor‐Acceptor Cyclobutanes

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