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相关概念视频

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

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

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.
Woodward–Hoffmann Selection Rules and Microscopic Reversibility01:34

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids02:04

Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids

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.
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction01:22

Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction

The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.

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Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
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Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Published on: November 21, 2017

一种可转氧化转换的基于alpha-cyclodextrin的 [2]rotaxane.

Yan-Li Zhao1, William R Dichtel, Ali Trabolsi

  • 1Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.

Journal of the American Chemical Society
|August 6, 2008
PubMed
概括
此摘要是机器生成的。

合成了一种新型的可双相稳定型罗他森,其中包括一个α-环氧德素环和一个氧化还原活性四亚系统. 在 redox刺激时,α-cyclodextrin环可控地在四iafulvalene和 triazole 单位之间移动.

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科学领域:

  • 超分子化学 超分子化学
  • 分子机器分子机器
  • 有机合成 有机合成

背景情况:

  • 罗塔克桑是机械互锁的分子,在纳米技术中具有潜在的应用.
  • 控制分子组件的运动对于开发功能性分子设备至关重要.
  • 反氧活性单元为对分子运动的外部控制提供了一条途径.

研究的目的:

  • 合成一种可二氧化 [2] 罗塔xane,其中包含一个有氧化还原活性的四亚 (TTF) 单元和一个α-cyclodextrin (alpha-CD) 环.
  • 为了阐明TTF和三醇部分之间的α-CD环的氧化还原驱动运动.
  • 量化和半量化确定阿尔法-CD环的首选结合点.

主要方法:

  • 通过Cu(I) 催化的亚酸-基环添加进行合成.
  • 用于结合亲和性研究的微热量计定位.
  • 电化学实验 (循环电压测量) 用于氧化还原驱动的切换.
  • 用光谱和手术测量进行结构确认.

主要成果:

  • 成功合成了与α-cyclodextrin和含有TTF的子一起的可复合[2]rotaxane.
  • 阿尔法-环氧素环优先与TTF单元结合,而不是三醇单元.
  • 反氧化诱导的TFT氧化导致alpha-CD环移动到三醇单元.
  • 在减少氧化TTF物种后,切换是可逆的.

结论:

  • 合成的可二氧化 [2] 罗他森证明了可控制的,可逆的分子切换基于氧化还原刺激.
  • 这项研究提供了量化证据,证明阿尔法-环极素与TTF单元的优先结合.
  • 这项工作有助于开发可回氧定位的分子机器和开关.