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Updated: May 25, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
08:12

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

Published on: August 16, 2018

Ketonization of enols in aqueous solution: is carbon protonation always rate-determining?

Anna Paola Pelliccioli1, Peter Šebej, Jakob Wirz

  • 1Department of Chemistry, University of Basel, CH-4056 Basel, Switzerland. anna.pelliccioli@novartis.com

Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology
|January 27, 2012
PubMed

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Reactivity of Enols

Enols are a class of compounds where a hydroxyl group is attached to a carbon–carbon double bond, which implies that it is a vinyl alcohol. A carbonyl compound with an α hydrogen undergoes keto–enol tautomerism and remains in equilibrium with its tautomer, the enol form. Usually, the keto tautomer is present in a higher concentration than the enol tautomer due to the higher bond energy of C=O compared to C=C. Moreover, the direction of the keto–enol equilibrium is governed by factors like...
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As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.
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