三坐标的arylpalladium胺复合物的合成,结构和还原性消除化学
Makoto Yamashita1, John F Hartwig
1Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA.
Journal of the American Chemical Society
|April 29, 2004
概括
新合成的具有T形结构的复合物很容易形成三胺. 三坐标复合物比四坐标复合物更快地消除,其中一个特定的铁酸复合物表现出最高的反应速率.
科学领域:
- 有机金属化学 有机金属化学
- 协调化学 协调化学
- 催化剂是一种催化剂.
背景情况:
- 胺复合物是各种催化转化中的关键中间体.
- 了解复合物的协调环境和电子特性是控制反应性的关键.
- 硬质障碍和协调数在减小消除中的作用仍然是一个活跃的研究领域.
研究的目的:
- 为了合成和结构性地描述新的三坐标的arylpalladium amido复合体.
- 调查协调数 (三坐标与四坐标) 对减少性消除率的影响.
- 探索固态阻断的素连接体对这些复合物的反应性的影响.
主要方法:
- 使用X射线晶体学分离和结构性特征四个新的arylpalladium胺复合物.
- 动力学研究比较三坐标复合体和四坐标复合体的减小消除率.
- 综合复合物,其中包括一个单一的,固体阻碍的氨酸连接体,包括一个五甲二三丁氨酸衍生物.
主要成果:
- 成功合成和表征了四个具有T形几何形状的三坐标的arylpalladium amido复合体.
- 这些三坐标复合物,有些缺乏C-H键协调,有效地经历了减少性淘汰,形成三胺.
- 与四坐标类似物相比,三坐标复合物的减少消除率明显更快,其中五甲二三丁复合物表现出最高的反应性.
结论:
- 真正的三坐标复合物是三胺合成的高度反应性的中间体.
- 减少协调数增加了减少性消除的速度,为更有效的催化提供了途径.
- 硬质要求高的配体,如五甲酸,可以进一步加快这些重要的C-N键形成反应.
相关概念视频
Preparation 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.
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
Treating arylamines with nitrous acid gives aryldiazonium salts that are effective substrates in nucleophilic aromatic substitution reactions. The diazonio group in these salts can be easily displaced by different nucleophiles, yielding a wide variety of substituted benzenes. The leaving group departs as nitrogen gas, and this easy elimination is the driving force for the substitution reaction.
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview
In the presence of an aqueous base and a halogen, primary amides can lose the carbonyl (as carbon dioxide) and undergo rearrangement to form primary amines. This reaction, called the Hofmann rearrangement, can produce primary amines (aryl and alkyl) in high yields without contamination by secondary and tertiary amines.
Diazonium Group Substitution: –OH and –H
Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.
Aryldiazonium Salts to Azo Dyes: Diazo Coupling
The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the para position.
![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)

