Dakin–West reaction
Reaction that converts amino acids into a keto-amides
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Through Chemical reaction, Amino acid and Ketone
With pyridine as a base and solvent, refluxing conditions are required. However, with the addition of 4-dimethylaminopyridine (DMAP) as a catalyst, the reaction can take place at room temperature.
With some acids, this reaction can take place even in the absence of an α-amino group.
This reaction should not be confused with the Dakin reaction.
Reaction mechanism
The reaction mechanism involves the acylation and activation of the acid 1 to the mixed anhydride 3. The amide will serve as a nucleophile for the cyclization forming the azlactone 4. Deprotonation and acylation of the azlactone forms the key carbon-carbon bond. Subsequent ring-opening of 6 and decarboxylation give the final keto-amide product.
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General ketone synthesis
Modern variations on the Dakin–West reaction permit many enolizable carboxylic acids – not merely amino acids – to be converted to their corresponding methyl ketones. For example, β-aryl carboxylic acids can be efficiently converted to β-aryl ketones by treatment of an acetic anhydride solution of the acid with catalytic N-methylimidazole. This reactivity is attributed in part to generation of acetylimidazolium, a powerful cationic acetylating agent, in situ.