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Related Concept Videos

Stereochemical Effects of Enolization01:12

Stereochemical Effects of Enolization

2.8K
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound undergoes racemization under an acidic or basic condition, an achiral enol is formed.
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Reactivity of Enols01:18

Reactivity of Enols

4.4K
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...
4.4K
Dehydration of Aldols to Enals: Base-Catalyzed Aldol Condensation01:14

Dehydration of Aldols to Enals: Base-Catalyzed Aldol Condensation

7.5K
This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy aldehyde formed in a base-catalyzed aldol addition reaction dehydrates on heating to yield an unsaturated carbonyl product, which is commonly referred to as an enal.
7.5K
Keto–Enol Tautomerism: Mechanism01:14

Keto–Enol Tautomerism: Mechanism

8.3K
The keto and enol forms are known as tautomers and they constantly interconvert (or tautomerize) between the two forms under acid or base catalyzed conditions. Both the reactions involve the same steps—protonation and deprotonation— although in the reverse order.
8.3K
Regioselective Formation of Enolates01:33

Regioselective Formation of Enolates

3.7K
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.
3.7K
Dehydration of Aldols to Enones: Acid-Catalyzed Aldol Condensation00:43

Dehydration of Aldols to Enones: Acid-Catalyzed Aldol Condensation

3.2K
As shown in Figure 1, under acidic conditions, the β-hydroxy ketone undergoes dehydration via an E1 elimination reaction to form an enone.
3.2K

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Updated: Apr 4, 2026

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators
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Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

Published on: November 27, 2015

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Diastereomer Interconversion via Enolization: A Case Study.

Andrea Renzetti1, Antonello Di Crescenzo2, Feilin Nie1

  • 1Department of Chemistry, University of Cambridge, Cambridge, UK.

Chirality
|September 5, 2015
PubMed
Summary
This summary is machine-generated.

This study explores the diastereoselectivity in a three-component reaction involving indole. It reveals that crystallization-induced asymmetric transformation drives the exclusive formation of a single diastereomer through an enolization mechanism.

Keywords:
HPLCMSNMRasymmetriccrystallizationdeuterationketo-enolkineticsmulticomponenttautomerization

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Area of Science:

  • Organic Chemistry
  • Stereochemistry
  • Reaction Mechanisms

Background:

  • Three-component reactions offer efficient synthetic routes to complex molecules.
  • Controlling diastereoselectivity is crucial for synthesizing specific stereoisomers.
  • Indole derivatives are important scaffolds in medicinal chemistry.

Purpose of the Study:

  • To investigate the origin of diastereoselectivity in the reaction of indole, isobutyraldehyde, and methyl acetoacetate.
  • To elucidate the thermodynamic and kinetic aspects of diastereomer interconversion.
  • To understand the mechanism leading to the exclusive formation of a single diastereomer.

Main Methods:

  • Nuclear Magnetic Resonance (NMR) spectroscopy for structural and dynamic analysis.
  • High-Performance Liquid Chromatography (HPLC) for separation and quantification of diastereomers.
  • Mass Spectrometry (MS) for molecular weight determination.
  • Deuteration experiments to identify stereolabile centers.

Main Results:

  • The reaction yields methyl 2-(acetyl)-3-(1H-indol-3-yl)-4-methylpentanoate as a single diastereomer.
  • Diastereomer interconversion is catalyzed by both acid and base.
  • The alpha carbon is identified as the sole stereolabile center.
  • An enolization mechanism is proposed for the interconversion process.

Conclusions:

  • The observed diastereoselectivity arises from an enolization mechanism.
  • Selective precipitation of one diastereomer drives the equilibrium towards exclusive formation (crystallization-induced asymmetric transformation).
  • This work provides insights into controlling stereochemistry in complex organic reactions.