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相关概念视频

Base-Catalyzed Ring-Opening of Epoxides02:26

Base-Catalyzed Ring-Opening of Epoxides

10.0K
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
10.0K
Acid-Catalyzed Ring-Opening of Epoxides02:24

Acid-Catalyzed Ring-Opening of Epoxides

8.6K
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
8.6K
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

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

7.2K
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...
7.2K
Nucleophilic Aromatic Substitution: Elimination–Addition01:11

Nucleophilic Aromatic Substitution: Elimination–Addition

5.0K
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...
5.0K
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

3.1K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
3.1K
Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)01:30

Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)

4.6K
Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the leaving group. The reaction proceeds via two steps: the addition of the nucleophile and the elimination of the leaving group.
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between...
4.6K

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Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
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通过核性催化剂进行应力环功能化的一般方法.

Ping Wang1,2, Cheng Deng3, Zihao Luo3

  • 1Eastern Institute for Advanced Study, Eastern Institute of Technology, Ningbo, Zhejiang 315200, P. R. China.

JACS Au
|November 28, 2025
PubMed
概括

这项研究引入了一种新的核性催化策略,用于带有张力环的反应. 它使各种C-H键和无外部基的异原子核友的直接,二重选择性添加成为可能,扩大了合成的可能性.

关键词:
没有基的无基.生物同位素是一种生物同位素.一种共价中间体.在 diastereo控制.核友的添加是核友的添加.核友性催化作用的核友性催化作用sp3 在CH债券中.紧张的戒指 紧张的戒指

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科学领域:

  • 有机化学 有机化学
  • 合成化学 合成化学
  • 催化剂是一种催化剂.

背景情况:

  • 核性添加应力环对于合成用于药物发现中的生物异构体的小性环至关重要.
  • 现有的方法往往需要固态度基,添加剂或苛刻核友,限制反应范围和实用性.
  • 在这个领域,实现 diastereocontrol 和直接功能化惰性 sp3 C-H 债券仍然是重大挑战.

研究的目的:

  • 开发一种新的核性催化策略,用于直接和二重选择性地将核类添加到应力环中.
  • 克服现有方法的局限性,包括需要外部基础和C-H债券功能化的困难.
  • 扩大核友和C-H键的范围,适应应力环系统的反应.

主要方法:

  • 开发一种核性催化方法,利用一种催化剂,该催化剂与张力环形成共价中间体.
  • 催化系统的应用,用于直接添加各种 sp3 C-H 键和异原子核 (碳酸,胺,氧化物,硫醇).
  • 通过机理学研究来研究反应机制,以阐明共价中间体的作用.

主要成果:

  • 演示一种通用和高效的核性催化策略,用于应力环功能化.
  • 成功的直接和二重选择性添加了广泛的sp3 C-H键和异构原子核友.
  • 消除对外部基或添加剂的要求,提高反应的实用性和兼容性.
  • 在催化循环中确定一个关键的共价中间体.

结论:

  • 开发的核性催化策略为紧张环的直接和二重选择性功能化提供了前所未有的途径.
  • 这种方法显著扩大了对应变环的核友性添加反应的范围,包括具有挑战性的C-H键添加.
  • 这些发现为合成宝贵的小形环和药物开发中的生物异构体提供了实用和多功能工具.