Johnson–Corey–Chaykovsky reaction

Johnson–Corey–Chaykovsky Reaction

Overview of the Johnson–Corey–Chaykovsky reaction.

The Johnson–Corey–Chaykovsky reaction is a chemical reaction used in organic chemistry to convert carbonyl compounds into epoxides or cyclopropanes. This reaction is named after the chemists Avery A. Johnson, E.J. Corey, and Michael Chaykovsky.

Reaction Overview

The Johnson–Corey–Chaykovsky reaction involves the use of a sulfur ylide to transform a carbonyl group into an epoxide or a cyclopropane. The reaction is particularly useful for the synthesis of epoxides from ketones and aldehydes.

Example of the Johnson–Corey–Chaykovsky reaction.

Mechanism

The mechanism of the Johnson–Corey–Chaykovsky reaction involves the generation of a sulfur ylide, which then reacts with the carbonyl compound. The ylide is typically generated from a sulfonium salt precursor.

Step 1: Formation of the Ylide

The first step involves the deprotonation of a sulfonium salt to form the sulfur ylide. This is usually achieved using a strong base.

Structure of a typical sulfur ylide used in the reaction.

Step 2: Nucleophilic Attack

The sulfur ylide acts as a nucleophile and attacks the carbonyl carbon, forming a betaine intermediate.

Step 3: Ring Closure

The betaine intermediate undergoes an intramolecular reaction to form the epoxide or cyclopropane, depending on the nature of the starting materials.

Mechanism of the Johnson–Corey–Chaykovsky reaction.

Applications

The Johnson–Corey–Chaykovsky reaction is widely used in the synthesis of complex organic molecules, particularly in the pharmaceutical industry. It provides a straightforward method for the formation of epoxides, which are valuable intermediates in the synthesis of various biologically active compounds.

Variations

There are several variations of the Johnson–Corey–Chaykovsky reaction, depending on the type of ylide and carbonyl compound used. These variations allow for the selective formation of different epoxide or cyclopropane products.

General structure of ylides used in the reaction.

Related Reactions

The Johnson–Corey–Chaykovsky reaction is related to other ylide-based reactions, such as the Wittig reaction and the Horner–Wadsworth–Emmons reaction, which also involve the formation of carbon-carbon bonds through ylide intermediates.

Related Pages

• Epoxide
• Cyclopropane
• Sulfur ylide
• Carbonyl compound
• E.J. Corey