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Acid-Catalyzed α-Halogenation of Aldehydes and Ketones01:21

Acid-Catalyzed α-Halogenation of Aldehydes and Ketones

By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
Base-Promoted α-Halogenation of Aldehydes and Ketones00:51

Base-Promoted α-Halogenation of Aldehydes and Ketones

α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base.  The reaction begins with the abstraction of  α hydrogen by the base to produce a nucleophilic enolate ion. This intermediate undergoes a subsequent nucleophilic substitution with the halogen to produce a monohalogenated carbonyl compound. If the starting substrate has more than one α hydrogen, it is difficult to stop the reaction at the stage of...
Base-Catalyzed Aldol Addition Reaction01:08

Base-Catalyzed Aldol Addition Reaction

As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy carbonyl compound.
Conjugate Addition to α,β-Unsaturated Carbonyl Compounds01:09

Conjugate Addition to α,β-Unsaturated Carbonyl Compounds

α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon.
Aldehydes and Ketones with Amines: Imine Formation Mechanism01:23

Aldehydes and Ketones with Amines: Imine Formation Mechanism

Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Acid-Catalyzed Aldol Addition Reaction01:15

Acid-Catalyzed Aldol Addition Reaction

The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The acid-catalyzed aldol reaction is depicted in Figure 1.

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相关实验视频

Updated: Jul 5, 2026

Modification and Functionalization of the Guanidine Group by Tailor-made Precursors
09:45

Modification and Functionalization of the Guanidine Group by Tailor-made Precursors

Published on: April 27, 2017

黑米拉比尔阿米多莫诺氨酸连接物- ((I) 复杂催化不对称的1,4-添加阿里尔酸到循环基.

Masami Kuriyama1, Kazushige Nagai, Ken-Ichi Yamada

  • 1Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.

Journal of the American Chemical Society
|July 26, 2002
PubMed
概括
此摘要是机器生成的。

这项研究引入了一种 ((I) 催化剂,用于酸和环基之间不对称的1,4-添加反应. 这种新型的阿米多蒙氨酸连接体使得在合成3 - - 烯基环醇时具有高产量和反选择性.

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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

Published on: October 18, 2019

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center
07:11

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center

Published on: September 28, 2022

相关实验视频

Last Updated: Jul 5, 2026

Modification and Functionalization of the Guanidine Group by Tailor-made Precursors
09:45

Modification and Functionalization of the Guanidine Group by Tailor-made Precursors

Published on: April 27, 2017

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
09:37

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

Published on: October 18, 2019

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center
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Constructing Cyclic Peptides Using an On-Tether Sulfonium Center

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科学领域:

  • 有机金属化学 有机金属化学
  • 不对称的催化剂.
  • 有机合成 有机合成

背景情况:

  • 在有机化学中,开发高效的用于不对称合成的催化系统至关重要.
  • 1,4-添加反应是碳-碳键形成的基本转换.
  • 金属催化反应通常依赖于连接体的精确协调行为.

研究的目的:

  • 开发一种新型的 (((I) 催化剂,用于对循环基子进行非对称的1,4-添加甲基酸.
  • 研究开发系统的催化活性,酶选择性和产量.
  • 为了阐明阿米多蒙啡因配体的协调行为和hemilabile性质.

主要方法:

  • 不对称的1,4-添加反应被1mol%的阿米多摩诺 - (I) 复合物催化.
  • 在10:1的1,4-二氧化和水混合物中,在100°C进行反应.
  • 通过核磁共振 (NMR),红外 (IR) 光谱和X射线晶体学获得的结构和机制见解.

主要成果:

  • 催化剂有效地提供了相当高的反选择性和高产量的3-基环.
  • 谱学研究证实了二酸胺蒙氨酸作为一个hemilabile连接体的作用.
  • 发现胺碳基氧与的协调对反应效率至关重要.

结论:

  • 一种新型的阿米多蒙 - (I) 催化剂能够有效的不对称的1,4-添加阿里尔酸到环基.
  • 连接体的半性质,特别是性胺碳基氧,是催化过程的关键.
  • 这种方法提供了一条有价值的途径,以致于以反聚合物丰富的3-arylcycloalkanones.