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Related Concept Videos

Reactivity of Enolate Ions01:23

Reactivity of Enolate Ions

Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, leading to a resonance-stabilized enolate ion where one of the contributing structures is an oxyanion, which imparts additional stability. Therefore, the proton on the α carbon is more acidic in nature than that of other sp3-hybridized C–H bonds but less acidic than those in O–H bonds where the negative charge in the conjugate base is localized on the oxygen...
Enolate Mechanism Conventions01:15

Enolate Mechanism Conventions

When a carbonyl compound is treated with a strong base, the α position gets deprotonated to give a resonance-stabilized intermediate called an enolate. Enolates are ambident nucleophiles because they possess two nucleophilic sites that can attack an electrophile owing to the delocalization of the negative charge between the α carbon and oxygen atoms. When the oxygen atom attacks an electrophile, it is called O-attack, whereas electrophilic attack via the α carbon is known as C-attack.
C-attack...
Regioselective Formation of Enolates01:33

Regioselective Formation of Enolates

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.
Reactivity of Enols01:18

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...
Stereochemical Effects of Enolization01:12

Stereochemical Effects of Enolization

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.
α-Alkylation of Ketones via Enolate Ions01:10

α-Alkylation of Ketones via Enolate Ions

Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the strong interaction...

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Related Experiment Video

Updated: Jul 3, 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

Intermolecular enolate heterocoupling: scope, mechanism, and application.

Michael P DeMartino1, Ke Chen, Phil S Baran

  • 1Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.

Journal of the American Chemical Society
|August 6, 2008
PubMed
Summary
This summary is machine-generated.

Researchers developed scalable oxidative coupling methods for carbonyl compounds like amides and ketones. This advancement offers new synthetic routes, demonstrated by applications in complex molecule synthesis.

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A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
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A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis

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Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks (MOFs)
08:25

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks (MOFs)

Published on: January 17, 2020

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Last Updated: Jul 3, 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

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
07:06

A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis

Published on: February 16, 2020

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks (MOFs)
08:25

Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks (MOFs)

Published on: January 17, 2020

Area of Science:

  • Organic Chemistry
  • Synthetic Methodology
  • Catalysis

Background:

  • Oxidative intermolecular coupling of carbonyl compounds is a crucial transformation in organic synthesis.
  • Existing methods often lack generality or scalability for creating diverse molecular architectures.
  • Understanding the mechanistic pathways of these couplings is essential for further development.

Purpose of the Study:

  • To develop reliable and scalable protocols for the oxidative intermolecular coupling of various carbonyl species.
  • To elucidate the mechanistic details of copper(II)- and iron(III)-mediated oxidative enolate couplings.
  • To demonstrate the utility of the developed methodology in complex molecule synthesis.

Main Methods:

  • Optimization of reaction conditions using soluble copper(II) and iron(III) salts as oxidants.
  • Extensive mechanistic investigations, including studies on single-electron transfer and heterodimerization pathways.
  • Application of the developed protocols to a broad scope of substrates (40 examples) and scale-up studies.

Main Results:

  • Established efficient and scalable protocols for the oxidative coupling of amides, imides, ketones, and oxindoles.
  • Provided in-depth mechanistic insights, differentiating between copper(II)- (single-electron transfer) and iron(III)-mediated (heterodimerization) processes.
  • Successfully applied the method to the total synthesis of (-)-bursehernin and a medicinally relevant succinate derivative.

Conclusions:

  • The developed oxidative enolate heterocoupling method is robust, scalable, and broadly applicable.
  • Mechanistic studies provide critical understanding of metal-mediated oxidative coupling reactions.
  • This methodology represents a significant advancement for constructing complex organic molecules.