催化 [4+1] 循环添加的α,β不和碳基化合物与异化物
Masayuki Oshita1, Kohei Yamashita, Mamoru Tobisu
1Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
Journal of the American Chemical Society
|January 13, 2005
概括
(III) 化物 (GaCl3) 有效地催化阿尔法,β不和和异酸盐之间的 [4+1] 循环添加反应,产生乳衍生物. 基质中的绝缘散体显著影响反应效率和产品产量.
科学领域:
- 有机化学 有机化学
- 催化剂是一种催化剂.
- 合成方法论 合成方法论
背景情况:
- 循环添加反应是有机合成中构建循环分子的基础.
- 易斯酸通常用于催化循环添加反应,激活基质.
- 为复杂分子合成开发高效和选择性的催化系统仍然是一个关键的挑战.
研究的目的:
- 为了研究 ((III) 化物 (GaCl3) 作为 [4+1] 循环添加反应的催化剂的实用性.
- 探索从α,β不和和异酸盐中合成乳衍生物.
- 了解基质结构对反应效率和范围的影响.
主要方法:
- 用GaCl3作为路易斯酸催化剂用于 [4+1] 循环添加反应.
- 与各种阿尔法,β不和子与芳香性和异性异酸盐一起反应.
- 在两个反应对象上系统地改变替代剂,以评估结构效应.
主要成果:
- GaCl3在促进 [4+1] 循环添加过程中表现出高的催化活性和效率.
- 这种反应成功地产生了各种乳衍生物.
- 不和子的β位置上的绝缘散体和异酸的电子特性显著影响了反应结果.
- 阿利法性异酸盐没有反应,而固态阻碍的芳香性异酸盐表现出良好的反应性.
结论:
- GaCl3是通过 [4+1] 循环添加合成乳的高效催化剂.
- 反应的成功归因于GaCl3对异原子的亲和力较低,使得有效的催化.
- 基板的硬质和电子因素对于优化这种合成转换至关重要.
相关概念视频
Introduction to Electrophilic Addition Reactions of Alkenes
The double bond in a simple, unconjugated alkene is a region of high electron density that can act as a weak base or a nucleophile. The filled π orbital (HOMO) of the double bond can interact with the empty LUMO of an electrophile. A bonding interaction occurs when the electrophile attacks between the two carbons; the electrophile then accepts a pair of electrons from the π bond and undergoes addition across the double bond, yielding a single product.
Addition and elimination reactions can be...
Addition and elimination reactions can be...
Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
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...
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...
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.
Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
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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