Chapter 21: Ester Enolates

Summary

• Diester compounds can be used to give an intramolecular Claisen condensation which is known as the Dieckmann condensation.
• This means the enolate component and the carbonyl component are parts of a single, larger molecule.
• Reagents : most commonly the base would be the alkoxide, RO^-, matching the alcohol portion of the ester (why ?)
• Remember enolates are good nucleophiles and the ester carbonyl C are electrophilic.
• The products of these reactions are cyclic b-ketoesters which are important, useful synthetic intermediates
• Favours the formation of the more stable 5- or 6-membered rings (review)

1. Form the enolate  (there two possible equivalent enolates either at C2 or C5)
2. Make the enolate attack the other carbonyl.

• Claisen Condensation
• Intramolecular Aldol Condensations

© Dr. Ian Hunt, Department of Chemistry