有效地激活芳香C-H键以添加C-C多重键
1Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Hakozaki, Fukuoka, 812-8581, Japan.
Science (New York, N.Y.)
|March 17, 2000
概括
这项研究引入了一种高效的催化方法,用于使用或来功能化芳香C-H键. 该过程使在室温下选择性C-C键与各种和异环形成.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 有机合成 有机合成
背景情况:
- 芳香C-H键的功能化对于合成复杂的有机分子至关重要.
- 开发高效和选择性的催化方法来激活C-H仍然是有机化学的一个重大挑战.
研究的目的:
- 开发一种催化系统,用于芳香C-H键的直接和区域选择性功能化.
- 通过电友金属化和对不和基质的添加来实现新的碳-碳键形成.
主要方法:
- 使用大量的 (II) 或 (II) 化合物的催化剂.
- 使用混合溶剂系统与三酸.
- 在室温下与各种和不和化合物进行反应.
主要成果:
- 使用 (II) 或 (II) 催化剂实现了芳香C-H键的高效电友金属化.
- 证明了对基和基的区域和立体选择性添加,形成新的C-C键.
- 观察到高效率和周转率 (高达4500) 在的转化,包括含电子丰富的基板和异环环.
结论:
- 开发的催化系统提供了一个简单,通用和高效的方法,用于Arene的功能化.
- 该过程产生了热力学上不利的cis-alkene和功能化的异环环.
- 这种方法在有机合成中具有重要的工业应用潜力.
相关概念视频
01:32Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview
Cyanohydrins are compounds that contain –CN and –OH groups on the same carbon atom. They are formed by the nucleophilic addition of the cyanide ions to the carbonyl group. Cyanide ions are highly basic and nucleophilic and can be generated from HCN under aqueous conditions. However, since HCN is a weak acid, the number of cyanide ions generated is very small. Hence, a small amount of base or KCN/NaCN is added to HCN to increase the concentration of the cyanide ions in the reaction mixture.
01:13meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...
01:04Structures of Aldehydes and Ketones
Vanillin—a flavoring agent in vanilla, cinnamaldehyde—a molecule responsible for the distinct smell of cinnamon, and acetone—a strong-smelling ingredient in nail polish removers, all belong to a class of carbonyl compounds called aldehydes and ketones (Figure 1). Although both aldehydes and ketones contain the characteristic carbonyl (C=O) bond, their chemical structures vary with respect to the groups directly attached to the carbonyl carbon.
In aldehydes (Figures 1a and 1b), the carbonyl...
In aldehydes (Figures 1a and 1b), the carbonyl...
01:10Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism
Cyanohydrins are formed when cyanide nucleophiles and carbonyl compounds like aldehydes and ketones react. A strong base, the cyanide ion, catalyzes cyanohydrin formation. The ions are generated from HCN under aqueous conditions. Once the cyanide ions are generated, the first step involves the nucleophilic attack of the cyanide ions on the electrophilic carbonyl carbon. This attack shifts the π electrons from the C=O to the oxygen atom forming the alkoxide ion intermediate. The alkoxide anion...
01:10C–C Bond Formation: Aldol Condensation Overview
Aldol condensation is an important route in synthetic organic chemistry used to generate a new carbon–carbon bond under basic or acidic conditions. The aldol condensation reaction presented in Figure 1 constitutes an aldol addition reaction followed by the dehydration process.
00:57C–C Bond Cleavage: Retro-Aldol Reaction
The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under acidic or basic conditions to form two molecules of carbonyl compounds. The mechanism of the reaction consists of three steps.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.