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Videos de Conceptos Relacionados

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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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

Heteroacoplamiento enolado intermolecular: alcance, mecanismo y aplicación.

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
Resumen
Este resumen es generado por máquina.

Los investigadores desarrollaron métodos escalables de acoplamiento oxidativo para compuestos carbonílicos como amidas y cetonas. Este avance ofrece nuevas rutas sintéticas, demostradas por aplicaciones en la síntesis de moléculas complejas.

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Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks (MOFs)
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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
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Área de la Ciencia:

  • Química orgánica es la química orgánica.
  • Metodología sintética de la metodología sintética.
  • La catálisis de la catálisis.

Sus antecedentes:

  • El acoplamiento intermolecular oxidativo de compuestos carbonílicos es una transformación crucial en la síntesis orgánica.
  • Los métodos existentes a menudo carecen de generalidad o escalabilidad para crear diversas arquitecturas moleculares.
  • La comprensión de las vías mecánicas de estos acoplamientos es esencial para un mayor desarrollo.

Objetivo del estudio:

  • Desarrollar protocolos confiables y escalables para el acoplamiento intermolecular oxidativo de varias especies de carbonilo.
  • Para aclarar los detalles mecánicos de los acoplamientos enolados oxidativos mediados por cobre (II) y hierro (III).
  • Demostrar la utilidad de la metodología desarrollada en la síntesis de moléculas complejas.

Principales métodos:

  • Optimización de las condiciones de reacción utilizando sales solubles de cobre (II) y hierro (III) como oxidantes.
  • Investigaciones mecanicistas extensas, incluidos estudios sobre las vías de transferencia de un solo electrón y de heterodimerización.
  • Aplicación de los protocolos desarrollados a una amplia gama de sustratos (40 ejemplos) y estudios a escala.

Principales resultados:

  • Estableció protocolos eficientes y escalables para el acoplamiento oxidativo de amidas, imidas, cetonas y oxindoles.
  • Proporcionó conocimientos mecanicistas en profundidad, diferenciando entre los procesos mediados por el cobre (transferencia de un solo electrón) y el hierro (heterodimerización).
  • Aplicó con éxito el método a la síntesis total de (-) -bursehernina y un derivado de succinato médicamente relevante.

Conclusiones:

  • El método de heteroacoplamiento de enolato oxidativo desarrollado es robusto, escalable y de amplia aplicación.
  • Los estudios mecánicos proporcionan una comprensión crítica de las reacciones de acoplamiento oxidativo mediadas por metales.
  • Esta metodología representa un avance significativo para la construcción de moléculas orgánicas complejas.