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Related Concept Videos

Cycloaddition Reactions: Overview01:16

Cycloaddition Reactions: Overview

2.6K
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
2.6K
Cycloaddition Reactions: MO Requirements for Thermal Activation01:16

Cycloaddition Reactions: MO Requirements for Thermal Activation

3.6K
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
3.6K
Radical Reactivity: Intramolecular vs Intermolecular01:33

Radical Reactivity: Intramolecular vs Intermolecular

1.8K
Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak...
1.8K
Radical Reactivity: Overview01:11

Radical Reactivity: Overview

2.1K
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired...
2.1K
Radical Formation: Addition00:47

Radical Formation: Addition

1.7K
Radicals can be formed by adding a radical to a spin-paired molecule. This is typically observed with unsaturated species, where the addition of a radical across the π bond leads to the production of a new radical by dissolving the π bond. For example, the addition of a Br radical to an alkene yields a carbon-centered radical.
Similar to charge conservation in chemical reactions, spin conservation is implicit for radical reactions. Accordingly, the product formed must possess an...
1.7K
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction01:16

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction

10.3K
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
10.3K

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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
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Recent advances in radical-mediated intermolecular (4 + 2) cycloaddition.

Xue-Er Cai1, Zi-Ying Wang1, Wen-Chan Tian1

  • 1School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang, 315211, China. leikewei@nbu.edu.cn.

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Radical-mediated (4 + 2) cycloaddition reactions offer efficient synthesis of carbocyclic and heterocyclic compounds. This review highlights recent advancements and mechanisms in this versatile organic chemistry tool.

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Area of Science:

  • Organic Chemistry
  • Synthetic Chemistry

Background:

  • The (4 + 2) cycloaddition is a vital reaction for synthesizing carbocyclic and heterocyclic compounds.
  • Radical reactions are increasingly recognized for their mild conditions and functional group compatibility in organic synthesis.

Purpose of the Study:

  • To summarize and highlight recent advancements in radical-mediated (4 + 2) cycloaddition processes.
  • To provide insights into reaction design and mechanisms for future developments.

Main Methods:

  • Classification of radical-mediated (4 + 2) cycloadditions based on the type of radical initiating the reaction.
  • Review of recent literature focusing on reaction design and mechanistic pathways.

Main Results:

  • Categorization of reactions involving alkenyl cations/radicals, aryl radicals, acyl radicals, alkyl radicals, and heteroatom radicals.
  • Emphasis on the mechanistic understanding of these cycloaddition processes.

Conclusions:

  • Radical-mediated (4 + 2) cycloadditions are powerful tools for efficient synthesis.
  • Further exploration of reaction design and mechanisms will drive innovation in intermolecular cycloadditions.