Ester Enolates and the Claisen Condensation | Organic Chemistry 3

The acidity of β-dicarbonyl is due to the resonance stabilization of the corresponding anion
 

Claisen Condensation:
 

Mechanism:

1. Ester enolate formation:
   
   
    
2. Nucleophilic addition:
   
   
    
3. Elimination followed by deprotonation:
   
   
    
4. Protonation upon acidic aqueous work-up:
   
   
    

The Claisen condensation is an equilibrium: a retro-Claisen condensation can be observed resulting in 2 ester molecules via a mechanism which is exactly the reverse of the forward reaction

Dieckmann Condensation: Intramolecular Claisen Condensation
 

Mixed Claisen reaction: Ester + Ketone
 

Mechanism:

1. Enolate formation by deprotonation
2. Enolate alkylation via a SN2

Mechanism:

1. Hydrolysis:
   
   
    
2. Decarboxylation:
   
   

Mechanism:

1. Enolate formation
2. Enolate alkylation
3. Hydrolysis
4. Decarboxylation

Mechanism: 1,4-addition