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Related Concept Videos

Cycloaddition Reactions: Overview01:16

Cycloaddition Reactions: Overview

3.8K
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.
3.8K
Cycloaddition Reactions: MO Requirements for Thermal Activation01:16

Cycloaddition Reactions: MO Requirements for Thermal Activation

5.1K
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.
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[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction01:16

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

13.7K
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.
13.7K
Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene01:14

Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene

3.9K
Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.
3.9K
Conjugate Addition (1,4-Addition) vs Direct Addition (1,2-Addition)01:27

Conjugate Addition (1,4-Addition) vs Direct Addition (1,2-Addition)

4.6K
α,β-Unsaturated carbonyl compounds with two electrophilic sites, the carbonyl carbon, and the β carbon, are susceptible to nucleophilic attack via two modes: conjugate or 1,4-addition and direct or 1,2-addition.
Conjugate addition results in a thermodynamically stable product. The reaction retains the stronger C=O bond at the expense of the weaker C=C π bond. The process is slow as the β carbon is less electrophilic than the carbonyl carbon.
Direct addition products are...
4.6K
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation01:27

Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation

3.1K
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
3.1K

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Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of &#945;-Imino &#947;-Lactones and Alkylidene Pyrazolones
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Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

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Natural 1,3-Dipolar Cycloadditions.

Martin Baunach1, Christian Hertweck2,3

  • 1Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Beutenbergstr. 11a, 07745 Jena (Germany).

Angewandte Chemie (International Ed. in English)
|October 15, 2015
PubMed
Summary
This summary is machine-generated.

Nature utilizes [3+2] cycloadditions, as demonstrated by a modified prenylated flavin cofactor. This cofactor, in its azomethine ylide form, engages in cycloadditions with aromatic acids, facilitating decarboxylation.

Keywords:
[3+2] cycloadditiondecarboxylationflavin coenzymeprenyl transferaseubiquinone biosynthesis

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Area of Science:

  • Biochemistry
  • Organic Chemistry
  • Natural Product Synthesis

Background:

  • 1,3-dipolar cycloadditions are known to occur in nature, supported by biomimetic syntheses and theoretical studies.
  • Prenylated flavin cofactors are heavily modified and play crucial roles in biological processes.

Purpose of the Study:

  • To elucidate the structure, biosynthesis, and function of a novel, heavily modified prenylated flavin cofactor.
  • To investigate the reactivity of this cofactor in cycloaddition reactions.

Main Methods:

  • Structural elucidation techniques (e.g., NMR, mass spectrometry).
  • Biosynthetic pathway analysis.
  • Biochemical assays to determine cofactor function and reaction mechanisms.

Main Results:

  • The structure of the modified prenylated flavin cofactor was determined.
  • Its biosynthetic origins were investigated.
  • The cofactor was shown to exist in an azomethine ylide form.
  • This form undergoes [3+2] cycloadditions with aromatic acids.
  • The cofactor promotes decarboxylation of these aromatic acids.

Conclusions:

  • A heavily modified prenylated flavin cofactor has been structurally and functionally characterized.
  • The cofactor participates in [3+2] cycloaddition reactions in its azomethine ylide form.
  • This cofactor plays a role in the decarboxylation of aromatic acids, highlighting a novel enzymatic mechanism.