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Updated: Jan 20, 2026
Keto–Enol Tautomerism: Mechanism
Theoretical Study on the Epimerization of Azlactone Rings: Keto-Enol Tautomerism or Base-Mediated Racemization?
Pedro P de Castro1, Gabriel M F Batista1, Hélio F Dos Santos1
1Chemistry Department, Federal University of Juiz de Fora, Campus Martelos, Juiz de Fora, Minas Gerais 36036-900, Brazil.
Abstract:
Azlactones are versatile heterocycles employed in a diversity of transformations; the main drawback of these cycles consists in the epimerization of the α-carbonyl stereocenter during its preparation. We hereby present a theoretical study to explain how the racemization occurs. Two hypotheses were investigated: the keto-enol tautomerism and the base-mediated racemization, through an enolate intermediate. The results showed that the latter is consistent with the experimental data and can spontaneously occur at room temperature. The same pathway was evaluated for 2-alcoxy azlactone, showing a slower epimerization ratio, consistent with the literature data.
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