Generating α,β-unsaturated carboxylic acids (cinnamic acid derivatives) in the presence of a weak base from aromatic aldehydes with the anhydrides of aliphatic carboxylic acids is known as the Perkin reaction. An enolate intermediate is made from the anhydride, which undergoes a condensation reaction with benzaldehyde, followed by an intramolecular acyl substitution. Further reaction with the anhydride, the base, and water affords a newly formed, typically (E) double bond.

• Reagents: Weak Base (NaOAc, KOAc, CsOAc, Et₃N, etc.)
• Reactant: Aromatic Aldehyde, Anhydride of Aliphatic Carboxylic Acid (with at least two α-hydrogens)
• Product: α,β-Unsaturated Carboxylic Acid
• Type of Reaction: Mixed Carbonyl Condensation
• Bond Formation: C=C-CO₂H

Lab Tips

This reaction requires high temperatures and long reaction times. Microwave irradiation instead of classical heating reduces reaction times; however, note that some studies suggest that NaOAc is not effective when using microwave irradiation and other bases should be considered. Moreover, studies suggest that if sodium acetate is used, it should be anhydrous.

Mechanism

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Related Compounds