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相关概念视频

Preparation of Alkynes: Alkylation Reaction02:27

Preparation of Alkynes: Alkylation Reaction

10.1K
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
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Reduction of Alkynes to trans-Alkenes: Sodium in Liquid Ammonia02:10

Reduction of Alkynes to trans-Alkenes: Sodium in Liquid Ammonia

9.2K
Alkynes can be reduced to trans-alkenes using sodium or lithium in liquid ammonia. The reaction, known as dissolving metal reduction, proceeds with an anti addition of hydrogen across the carbon–carbon triple bond to form the trans product. Since ammonia exists as a gas (bp = −33°C) at room temperature, the reaction is carried out at low temperatures using a mixture of dry ice (sublimes at −78°C) and acetone. 
When dissolved in liquid ammonia, an alkali metal,...
9.2K
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration02:34

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration

8.4K
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
8.4K
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

3.3K
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
3.3K
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation02:24

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

7.7K
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
7.7K
Nucleophilic Aromatic Substitution: Elimination–Addition01:11

Nucleophilic Aromatic Substitution: Elimination–Addition

4.0K
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...
4.0K

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Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
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由一个超基胺基催化的基异构.

Andreu Tortajada1, Gian Luca Righetti1, Ana McGinley2

  • 1Department für Chemie, Biochemie und Pharmacie, Universität Bern, Freiestrasse 3, 3012, Bern, Switzerland.

Angewandte Chemie (International ed. in English)
|June 17, 2024
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概括

这项研究引入了一种新型的催化异构化方法,使用地球上丰富的胺 (NaTMP) 和PMDETA. 这种方法在温和条件下高效地异构化各种终端烯,为过渡金属催化剂提供了可持续的替代方案.

关键词:
胺酸的化物.阿尔肯斯 (Alkenes) 是一种类型.催化剂是一种催化剂.密度函数理论密度函数理论异构化的异构化

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科学领域:

  • 有机金属化学 有机金属化学
  • 催化剂是一种催化剂.
  • 有机合成 有机合成

背景情况:

  • 烯异构化通常依赖于过渡金属,通常需要恶劣的条件或活性基质.
  • 主组试剂对基异构的探索较少,原因是对未激活基质和高试剂固态度的限制.
  • 在温和条件下开发土壤丰富的催化系统,用于在温和条件下进行基异构化是一个重大挑战.

研究的目的:

  • 探索使用大型胺基 (NaTMP) 与易斯捐赠体 (PMDETA) 进行催化异构的应用.
  • 在温和反应条件下研究未激活的终端烯酸的异构.
  • 阐明开发的催化系统的机制和选择性.

主要方法:

  • 使用胺胺 (NaTMP) 和N,N,N',N'',N''-甲基二乙烯胺 (PMDETA) 的催化基异构化反应.
  • 基质范围评估,包括未激活的烯酸,氨酸和氨酸.
  • 使用X射线晶体学,实时核磁共振 (NMR) 监测和密度函数理论 (DFT) 计算的机械研究.

主要成果:

  • 在温和条件下,成功的催化异构化各种终端烯酸,包括未激活的烯酸.
  • 证明该系统与胺和乙烯的有效性,展示其广泛的适用性.
  • 机理学研究揭示了现场生成的TMP (H) 的关键作用以及金属选择对异构化效率和E/Z选择性的影响.
  • 实现了未激活环基的同位素交换和化,突出显示了该方法的多功能性.

结论:

  • 与PMDETA合作的大量胺 (NaTMP) 提供了一个有效的催化系统,用于终端烯的异构化.
  • 开发的方法在温和条件下运行,并展示了广泛的基质范围,为过渡金属催化提供了可持续的替代方案.
  • 机理学的洞察力澄清了反应途径和控制选择性的因素,为进一步发展主群介导催化剂铺平了道路.