的o-和C-酸复合物的合成和阿尔多尔反应性
Juan Cámpora1, Celia M Maya, Pilar Palma
1Instituto de Investigaciones Químicas, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Avda, Spain.
Journal of the American Chemical Society
|February 6, 2003
概括
循环复合物阻碍了轻易的分体化,使得不同的反应性研究成为可能. 在室温下,O结合的分离体选择性地与化物反应,形成添加产物.
科学领域:
- 有机金属化学 有机金属化学
- 协调化学 协调化学
- 有机合成 有机合成
背景情况:
- 过渡金属酸盐通常容易经历C-/O-自动化.
- 由于快速的相互转换,研究单个陶托马的独特反应性是具有挑战性的.
- 循环连接体结构可以影响金属复合物的稳定性和反应性.
研究的目的:
- 为了研究周期性乙酸盐的单个分离体的反应性.
- 为了确定阻碍的陶托美化过程对反应通路的影响.
- 探索O结合的乙烯酸盐与的选择性反应.
主要方法:
- 循环乙烯酸复合物的合成 (1和2).
- 复合物的光谱和分析特征.
- 在室温下与化物进行反应研究.
主要成果:
- 易于C-/O-自动化过渡金属乙烯酸盐在循环Ni复合物1和2中受到显著阻碍.
- 在室温下,与O结合的复合体 (2) 显示出对化物有选择性的反应.
- 从与化物反应的O结合型复合体中成功形成了添加产物.
结论:
- 循环结构有效地抑制了分体化,允许隔离和研究单独的酸盐形式.
- 有O结合的乙烯酸具有特定的反应性,特别是在与等电友的反应中.
- 这项工作为使用不同金属酸分离体的受控合成应用提供了基础.
相关概念视频
01:21Acid-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...
01:09Conjugate 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.
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.
01:15Acid-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.
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.
01:33Aldol Condensation vs Claisen Condensation
Aldol condensation is an acid or base-catalyzed condensation between aldehydes or ketones to give an α,ꞵ-unsaturated carbonyl compound. A base-promoted condensation between ester molecules to produce a ꞵ-ketoester is known as the Claisen condensation. In the presence of a base, both reactions involve deprotonation of the acidic α hydrogen to produce the corresponding enolates. The nucleophilic enolates attack their respective nonenolized carbonyl compound forming a tetrahedral intermediate.