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在可见光照射下使用1,2-二-1,2,4,5-四-3,6-二氧化物形成可隔离的 [4 + 2] 循环导管

  • 0Faculty of Pharmaceutical Sciences, Hokkaido University, Kita-12 Nishi-6, Kita-ku, Sapporo 060-0812, Japan.
Journal of the American Chemical Society +

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2023年四月13日

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相关概念视频

[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...

Cycloaddition Reactions: Overview 01:16

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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.

The feasibility of cycloaddition reactions under thermal and photochemical conditions can be...

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry 01:29

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Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.

Dienophiles with one or more electron-withdrawing substituents form stereochemically different products in which the substituents are oriented in an endo (towards) or exo (away) configuration relative to the double bond.

The endo isomer is formed faster and is the kinetic product. The exo isomer is more stable and is the thermodynamic...

Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions 01:20

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Arenediazonium substitution reactions occur when the diazonium group is substituted by various functional groups such as halides, hydroxyl, nitrile, etc. For instance, arenediazonium salts react with copper(I) salts of chloride, bromide, or cyanide to form corresponding aryl chlorides, bromides, and nitriles. These reactions are named Sandmeyer reactions. Although the mechanism of this reaction is complicated, as illustrated in Figure 1, they are believed to progress via an aryl copper...

Nucleophilic Aromatic Substitution: Elimination–Addition 01:11

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Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as high temperatures or strong bases. The mechanism of substitution under such conditions involves the highly unstable and reactive benzyne intermediate. Benzyne contains equivalent carbon centers at both ends of the triple bond, each of which is equally susceptible to nucleophilic attack. This 50–50 distribution of products is...

Diels–Alder Reaction Forming Cyclic Products: Stereochemistry 01:28

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The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.

For the electrons to flow seamlessly between the two π systems, specific stereochemical and conformational requirements must be met.
Stereochemical Orbital Symmetry
The frontier molecular orbitals that satisfy the symmetry...