Organic Chemistry III
	Professor Carl C. Wamser
	Chapter 21 Notes	Chem 336 - Spring 2005

Ester Enolates

The Claisen Condensation

• condensation with a carboxyl derivative gives substitution instead of addition
• the Claisen condensation gives beta-ketoesters

• crossed Claisen reaction - two different esters
  works best of one has no alpha-hydrogens,
  e.g., formate, carbonate, oxalate, or benzoate ester
• Dieckmann condensation - intramolecular Claisen - diester gives cyclic product

Decarboxylation of beta-ketoacids

• Claisen products can be easily hydrolyzed and decarboxylated

Acetoacetic Ester and Malonic Ester Syntheses

• methods for preparing substituted acetones or acetic acids

• if steps 1) and 2) are repeated, two substituents can be attached

Biological Claisen Reactions

• acetyl Co-A often acts as a biological nucleophile at its alpha-position
• formation of acetoacetyl Co-A is the first step in building up fatty acids