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Related Concept Videos

Aldehydes and Ketones with Amines: Enamine Formation Mechanism01:14

Aldehydes and Ketones with Amines: Enamine Formation Mechanism

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Enamine formation involves the addition of carbonyl compounds to a secondary amine through a series of reactions. The mechanism begins with the generation of carbinolamine, a nucleophilic attack followed by several proton transfer reactions. The hydroxyl group of the carbinolamine is converted into water to make a better leaving group that can push the reaction forward by eliminating a water molecule. In enamine formation, the last step involves the abstraction of a proton from the α carbon to...
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α-Alkylation of Ketones via Enolate Ions01:10

α-Alkylation of Ketones via Enolate Ions

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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...
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Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

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Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
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Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction01:26

Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction

3.9K
α-Substituted ketones or aldehydes can be synthesized from enamines by the Stork enamine reaction, named after its pioneer Gilbert Stork. Enamines are useful synthetic intermediates where the lone pair on nitrogen is in conjugation with the C=C bond. They resemble enolate ions, as the resonance forms of both species have a nucleophilic α carbon.
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Acid-Catalyzed α-Halogenation of Aldehydes and Ketones01:21

Acid-Catalyzed α-Halogenation of Aldehydes and Ketones

4.6K
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
4.6K
Regioselective Formation of Enolates01:33

Regioselective Formation of Enolates

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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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Updated: Dec 17, 2025

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
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Cobaloxime Catalysis for Enamine Phosphorylation with Hydrogen Evolution.

Tao Lei1,2, Ge Liang1,2, Yuan-Yuan Cheng1,2

  • 1Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, P.R. China.

Organic Letters
|June 26, 2020
PubMed
Summary

Visible-light-driven cobaloxime catalysis enables direct phosphorylation of enamines and enamides. This method efficiently produces diverse β-phosphinoyl products, with selective conversion of Z/E enamine mixtures into single Z-products.

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Area of Science:

  • Organometallic Chemistry
  • Photocatalysis
  • Organic Synthesis

Background:

  • Enamines and enamides are versatile synthetic intermediates.
  • Direct C-P bond formation remains a synthetic challenge.
  • Cobaloxime catalysts are effective in radical-mediated transformations.

Purpose of the Study:

  • To develop a novel method for direct phosphorylation of enamines and enamides.
  • To explore the mechanism of cobaloxime-catalyzed phosphorylation under visible light.
  • To achieve stereoselective synthesis of β-phosphinoyl compounds.

Main Methods:

  • Visible-light photoredox catalysis using a cobaloxime catalyst.
  • Radical generation via reductive quenching of the excited catalyst.
  • Cross-coupling reaction between phosphinoyl radicals and enamines/enamides.

Main Results:

  • Direct phosphorylation of various enamines and enamides was achieved with hydrogen evolution.
  • Diverse β-phosphinoyl products were obtained in good to excellent yields.
  • Stereoselective synthesis of Z-isomers from Z/E enamine mixtures was demonstrated.

Conclusions:

  • Cobaloxime catalysis under visible light provides an efficient route for β-phosphinoyl compound synthesis.
  • The reaction proceeds via a reductive quenching pathway generating phosphinoyl radicals.
  • The method offers a valuable tool for constructing complex organophosphorus compounds with stereochemical control.