The Knoevenagel condensation uses a catalytic base such as piperidine to convert an aldehyde or ketone and an activated methylene compound to a α,β-unsaturated dicarbonyl or related compound. The base deprotonates the methylene compound, creating a resonance stabilized enolate, which reacts with an iminium ion made from the carbonyl compound and the 1° or 2° amine to yield a tetrahedral intermediate. A 1,2-elimination affords the desired α,β-unsaturated dicarbonyl or related compound.
- Reagents: Weak Catalytic Base (1°, 2°, 3° Amine, TiCl4/Et3N, KF, etc.), Dipolar Aprotic Solvent (e.g. DMF)
- Reactant: Aliphatic/Aryl Aldehyde or Ketone, Activated Methylene Compound (Malonic Ester, Acetoacetic Ester, etc.)
- Product: α,β-Unsaturated Dicarbonyl or Related Compound
- Type of Reaction: Base-Catalyzed Aldol Condensation
Mechanism
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Original Paper
Related Reactions
- Acetoacetic Ester Synthesis
- Malonic Ester Synthesis
