合成,反应性和计算分析的halophosphines由dianionic guanidinate连接体的支持
Allison L Brazeau1, Mikko M Hänninen, Heikki M Tuononen
1Department of Chemistry, The University of Western Ontario, Chemistry Building, 1151 Richmond Street, London, N6A 5B7 Ontario, Canada.
Journal of the American Chemical Society
|February 23, 2012
概括
酸支持的化合物表现出有限的反应性,抵抗酸的形成,有利于碳胺的消除. 这项研究探讨了它们独特的化学和对它们的结合的计算洞察力.
科学领域:
- 有机化学化学 有机化学
- 主要组 元素化学 元素化学
- 协调化学 协调化学
背景情况:
- 关尼丁酸连接物在稳定金属元素方面已经很成熟.
- 支持瓜尼丁酸的15组元素的化学成分,特别是氧化状态为+3的,仍未得到充分研究.
- 关于这种复合物的反应性,数据有限.
研究的目的:
- 为了合成和表征由瓜尼丁酸连接体支持的新型化复合物.
- 为了全面调查这些瓜尼丁酸支持的化的反应性.
- 阐明控制它们反应路径的因素,包括离子的形成和分解路径.
主要方法:
- 合成 homo- 和异体质的瓜尼丁酸支持的.
- 详细的反应性研究,包括化物抽象试验.
- 热和化学分解分析.
- 计算建模 (密度函数理论) 探测电子结构和反应能量学.
主要成果:
- 成功合成了一系列瓜尼丁酸支持的化素.
- 观察到不愿意形成N-异环酸.
- 主要的分解途径涉及碳胺的消除.
- 通过chloro(imino) phosphine插入,几乎没有观察到环扩张.
- 计算分析证实了目标酸的强P-X键和高电子接受能力,解释了反应障碍.
结论:
- 与其金属对应物相比,瓜尼丁酸支持的化呈现出不同的反应模式.
- P-X 键的固有稳定性和潜在中间体的电子性质限制了某些反应途径.
- 碳二胺的消除代表了这些系统的重要分解途径.
相关概念视频
01:19Diazonium 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.
01:24ortho–para-Directing Deactivators: Halogens
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
01:20Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions
Arenediazonium substitution reactions occur when the diazonium group is substituted by various functional groups such as halides, hydroxyl, nitrile, etc. For instance, arenediazonium salts react with copper(I) salts of chloride, bromide, or cyanide to form corresponding aryl chlorides, bromides, and nitriles. These reactions are named Sandmeyer reactions. Although the mechanism of this reaction is complicated, as illustrated in Figure 1, they are believed to progress via an aryl copper...
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
01:14Nucleophilic 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...