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興奮状態の銅触媒 [4 + 1] 解消反応はα,β-不飽和γ-ラクトムのモジュール合成を可能にします.

  • 0Department of Chemistry, State University of New York, Stony Brook, New York 11794-3400, United States.

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Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation 01:27

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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).

The ring-forming reaction occurs in two stages: Michael addition and the subsequent...

Conjugate Addition to α,β-Unsaturated Carbonyl Compounds 01:09

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α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon.

A simple nucleophilic attack at the carbonyl center results in an alkoxy intermediate, which gives the direct or 1,2-addition product upon further protonation.

When the nucleophile attacks the β carbon,...

Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction 01:26

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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.

However, enamines are neutral and less reactive than enolates, which bear a net negative charge. Consequently, enamines are effective Michael donors...

Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism 01:26

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The Hofmann and Curtius rearrangement reactions can be applied to synthesize primary amines from carboxylic acid derivatives such as amides and acyl azides. In the Hofmann rearrangement, a primary amide undergoes deprotonation in the presence of a base, followed by halogenation to generate an N-haloamide. A second proton abstraction produces a stabilized anionic species, which rearranges to an isocyanate intermediate via an alkyl group migration from the carbonyl carbon to the neighboring...

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In the presence of an aqueous base and a halogen, primary amides can lose the carbonyl (as carbon dioxide) and undergo rearrangement to form primary amines. This reaction, called the Hofmann rearrangement, can produce primary amines (aryl and alkyl) in high yields without contamination by secondary and tertiary amines.

In the Curtius rearrangement, acyl azides are converted into primary amines under thermal conditions, accompanied by the loss of gaseous N2 and CO2. The loss of nitrogen acts as...

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction 01:16

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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.

From a molecular orbital perspective, the interacting lobes of the two π systems must be in phase...