Favorskii reaction

Favorskii Reaction

Schematic representation of the Favorskii reaction.

The Favorskii reaction is an organic chemical reaction that involves the rearrangement of a cyclopropanone or an _-haloketone to form a carboxylic acid or its derivative. This reaction is named after the Russian chemist Aleksei Yevgrafovich Favorskii, who first reported it in the early 20th century.

Mechanism

The Favorskii reaction proceeds through a series of steps that involve the formation of an enolate intermediate. The general mechanism can be described as follows:

1. Formation of Enolate: The reaction begins with the deprotonation of the _-haloketone by a base, leading to the formation of an enolate ion.
2. Cyclopropanone Intermediate: The enolate undergoes an intramolecular nucleophilic attack on the carbon bearing the halogen, resulting in the formation of a cyclopropanone intermediate.
3. Ring Opening: The cyclopropanone ring opens to form a carbanion, which is stabilized by resonance.
4. Nucleophilic Attack: The carbanion then attacks a carbonyl carbon, leading to the formation of a new carbon-carbon bond.
5. Protonation: Finally, the intermediate is protonated to yield the carboxylic acid or its derivative.

Applications

The Favorskii reaction is widely used in organic synthesis for the preparation of cyclic and acyclic carboxylic acids. It is particularly useful in the synthesis of _-keto esters and _-lactones. The reaction is also employed in the synthesis of various natural products and pharmaceuticals.

Variations

Several variations of the Favorskii reaction have been developed to improve its efficiency and scope. These include the use of different bases, solvents, and reaction conditions to optimize the yield and selectivity of the desired product.

Related Reactions

The Favorskii reaction is related to other rearrangement reactions such as the Wolff rearrangement and the Arndt-Eistert synthesis, which also involve the formation and rearrangement of carbanion intermediates.

Related Pages

• Aleksei Yevgrafovich Favorskii
• Rearrangement reaction
• Cyclopropanone
• Carboxylic acid
• Enolate