Peterson Olefination

Definition

The Peterson olefination is a method for the synthesis of alkenes from carbonyl compounds and stabilized phosphorus ylides. It is a variation of the well-known Wittig reaction, which involves the nucleophilic addition of phosphorus ylides to carbonyl groups.

5 Must Know Facts For Your Next Test

1. The Peterson olefination is a variation of the Wittig reaction, where the phosphorus ylide is stabilized by an adjacent silicon atom.
2. The stabilized phosphorus ylide in the Peterson olefination is more reactive and selective compared to the traditional Wittig reaction, allowing for better control over the stereochemistry of the alkene product.
3. The Peterson olefination typically proceeds through the formation of a cyclic intermediate, which then undergoes elimination to form the desired alkene.
4. The Peterson olefination is particularly useful for the synthesis of trisubstituted and tetrasubstituted alkenes, which can be challenging to obtain using other methods.
5. The Peterson olefination is a valuable tool in organic synthesis, especially in the construction of complex natural products and pharmaceuticals.

Review Questions

• Explain the key difference between the Peterson olefination and the Wittig reaction.
  • The key difference between the Peterson olefination and the Wittig reaction is the nature of the phosphorus ylide used. In the Peterson olefination, the phosphorus ylide is stabilized by an adjacent silicon atom, making it more reactive and selective compared to the traditional Wittig reaction. This allows for better control over the stereochemistry of the alkene product, making the Peterson olefination particularly useful for the synthesis of trisubstituted and tetrasubstituted alkenes.
• Describe the mechanism of the Peterson olefination and how it differs from the Wittig reaction.
  • The Peterson olefination proceeds through the formation of a cyclic intermediate, which then undergoes elimination to form the desired alkene product. This differs from the Wittig reaction, which involves the direct nucleophilic addition of the phosphorus ylide to the carbonyl group, followed by elimination. The stabilization of the phosphorus ylide by the adjacent silicon atom in the Peterson olefination makes the cyclic intermediate more reactive and selective, leading to improved control over the stereochemistry of the alkene product.
• Discuss the synthetic applications of the Peterson olefination and how it complements the Wittig reaction in organic synthesis.
  • The Peterson olefination is a valuable tool in organic synthesis, particularly for the construction of complex natural products and pharmaceuticals. Its ability to selectively form trisubstituted and tetrasubstituted alkenes makes it a complementary method to the Wittig reaction, which is more suitable for the synthesis of disubstituted alkenes. The Peterson olefination is often used in the later stages of multistep synthetic sequences, where the improved stereochemical control and reactivity of the stabilized phosphorus ylide are crucial for the successful completion of the target molecule.

Related terms

Wittig Reaction:

The Wittig reaction is a method for the synthesis of alkenes from carbonyl compounds and phosphorus ylides. It involves the nucleophilic addition of the phosphorus ylide to the carbonyl group, followed by elimination to form the alkene product.

Phosphorus Ylide: A phosphorus ylide is a highly reactive species containing a positively charged phosphorus atom bonded to a negatively charged carbon atom. Phosphorus ylides are commonly used in organic synthesis reactions, such as the Wittig and Peterson olefination reactions.

Nucleophilic Addition:

Nucleophilic addition is a type of organic reaction where a nucleophile (a species with a high electron density) adds to an electrophilic carbon center, such as a carbonyl group, to form a new product.