易斯酸介导的选择性化烯酸酸的选择性化
Yanhua Zhang1, Kazutaka Shibatomi, Hisashi Yamamoto
1Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, USA.
Journal of the American Chemical Society
|November 19, 2004
概括
使用易斯酸和二二尼尔控制器开发了一种新型的化方法. 这种高效的技术实现了高反应性和选择性,特别是在二化马洛尼 Ester.
科学领域:
- 有机化学 有机化学
- 合成化学 合成化学
背景情况:
- 阿尔法化是有机合成中的一个关键转化.
- 开发高效和选择性的α-化方法仍然是一个活跃的研究领域.
研究的目的:
- 报告一种新的,高效的,广泛适用的,高度选择性的化乙酸的α-方法.
- 为了研究发达反应的二元选择性和二元选择性.
主要方法:
- 使用了易斯酸催化剂.
- 采用一个α,α-二chloro-1,3-dicarbonyl化合物作为控制单元.
- 研究了使用alpha,alpha-dichlorinated malonic ester来提高反应性和选择性.
主要成果:
- 在α-化反应中实现了高反应性和选择性.
- 证明了二化马龙乙烯控制器的有效性.
- 成功调查了该过程的二聚体选择性和酶选择性.
结论:
- 开发的方法提供了一种高效和有选择的途径,用于化西乙烯酸盐的α-化.
- 使用alpha,alpha-dichlorinated malonic ester对于实现高性能至关重要.
- 这种反应对不对称合成应用非常有希望.
相关概念视频
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
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.
02:27Preparation of Alkynes: Alkylation Reaction
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.
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.
01:13Relative Reactivity of Carboxylic Acid Derivatives
Carboxylic acid derivatives such as acid halides, anhydrides, esters, and amides undergo nucleophilic acyl substitution reactions with varying degrees of reactivity.
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
01:15Nucleophilic Acyl Substitution of Carboxylic Acid Derivatives
Nucleophilic acyl substitution is an important class of substitution reactions involving a nucleophile and an acyl compound, such as carboxylic acids and their derivatives. In these reactions, the leaving group attached to the acyl group is substituted by a nucleophile. The general mechanism proceeds via two steps.
01:33Regioselective Formation of Enolates
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.