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在pH响应的2-酸纳米载体的结构特征上,二烯中的定位异构的调节作用

  • 0Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark.
Journal of the American Chemical Society +

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2025年八月25日

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Preparation of Diols and Pinacol Rearrangement 01:57

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Compounds bearing two hydroxyl groups are known as diols. When the hydroxyl groups are located on adjacent carbon atoms, the diols are called vicinal diols or glycols. Under acidic conditions, vicinal diols undergo a specific reaction called pinacol rearrangement.
The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.

In the second step, the oxonium ion loses H2O, forming a tertiary carbocation intermediate.

In the...

Stability of Conjugated Dienes 01:28

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Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.

The two main factors contributing to the enhanced stability of conjugated systems are the delocalization of π electrons and the sp2 hybridization of the carbons forming the single bonds.
Planar Conformers of Conjugated Dienes
Conjugated dienes adopt two planar configurations, s-cis and...

Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids 02:04

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Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.

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...

Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide 02:44

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Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.

Syn Dihydroxylation Mechanism
The reaction comprises a two-step mechanism. It begins with the addition of osmium tetroxide across the alkene double bond in a concerted manner forming a...

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...