1. Lecture 34 – Chapter 21 : Ester Enolates
Ester enolate formation – a-deprotonation
Ester enolate reacting with ester – Claisen condensation

2. Chapter 21: Deprotonation of a-H in Esters
Choice of base is important
Saponification competes with deprotonation when hydroxide used
Last step of saponification is irreversible, leads to carboxylate salt
Use the base that corresponds to the OR’ group on the ester

3. Claisen: Same setup as the simple aldol reaction
Both enolate and ester present in mixture:
Claisen condensation results:
b-keto ester

4. Examples 2 a-H required to send reaction to the Claisen product
Always need acid in second step to quench anion

5. Intramolecular Condensation – the Dieckmann Reaction
Both the nucleophile (enolate) and electrophile are now in same system
Intramolecular Claisen condensation results – cycle formed
Protonation still required to isolate b-keto ester product

6. Crossed (Mixed) Claisen Reactions
Problem:
Solution:

7. From alcohols to a,a-disubstituted ketones

8. Examples: