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相关概念视频

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation02:24

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

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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.
8.1K
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation02:47

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation

18.9K
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
18.9K
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation02:17

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

3.4K
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...
3.4K
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.1K
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.
2.1K
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

1.9K
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
1.9K
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

6.3K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
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[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst
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[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

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通过多重脱激活电催化C─H到β-化

Kazuhiro Okamoto1, Simon L Homölle1, Tristan von Münchow1

  • 1Wöhler Research Institute for Sustainable Chemistry (WISCh), Georg-August-Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany.

Angewandte Chemie (International ed. in English)
|September 4, 2025
PubMed
概括

这项研究引入了电催化技术以实现可持续的C-H激活,从而实现直接合成β-酸. 这种方法避免预先功能化的基板,并使用电力作为清洁的氧化剂.

关键词:
电化学不同循环气其他皮罗尔可持续性

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科学领域:

  • 有机化学
  • 电催化
  • 可持续的合成

背景情况:

  • 传统的C-H激活通常依赖于静态氧化剂,造成环境问题.
  • 开发可持续的C-H激活替代品对于绿色化学至关重要.
  • 催化为高效和环保转型提供了一个有前途的途径.

研究的目的:

  • 开发一种新的电催化方法来合成β-化.
  • 在没有预功能化的情况下,在pyrroles和arenes之间实现直接的C-C键形成.
  • 证明电化学作为无痕氧化剂在有机合成中的实用性.

主要方法:

  • 在未分割的细胞中催化电化学.
  • 多重脱C-H激活策略.
  • 循环电压测量用于机械研究.

主要成果:

  • 实现了β-化的高效合成.
  • 证明了 pyrroles 和 arenes 之间的直接 C-C 合.
  • 由机理学研究支持的 (II/III/IV) 催化循环的证据.

结论:

  • 电催化提供了一个可持续的C-H激活平台.
  • 电化学方法提供一种无痕且对环境无害的方法.
  • 这项工作扩大了电催化用于构建复杂的异基框架的范围.