在室温下将1,2-二二基烯分解为二基烯
Katsunori Suzuki1, Tsukasa Matsuo, Daisuke Hashizume
1Functional Elemento-Organic Chemistry Unit, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Journal of the American Chemical Society
|November 15, 2011
概括
在室温下,绝缘保护的二基烯与基烯建立了动态平衡. 这种平衡促进了像Grignard试剂替代等反应,由4-pyrrolidinopyridine加速.
科学领域:
- 有机化学 有机化学
- 动态共价化学 动态共价化学
- 反应性中间体的反应性中间体
背景情况:
- 双基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基基
- 西利烯是类似于碳的双价物种.
- 稳定反应性中间体对于它们的研究和应用至关重要.
研究的目的:
- 为了证明二基烯和基烯之间的室温动态平衡.
- 为了研究这些物种的反应性.
- 为了分离和描述新的化合物.
主要方法:
- 合成大型的林德替代二基烯.
- 使用伪第一阶分析捕捉反应的动力学研究.
- 交叉实验与不同的二基烯.
- 反应产品的光谱表征,包括PPy-bromosilylene添加物.
主要成果:
- 在dibromodisilenes和bromosilylenes之间建立并保持在室温下的动态平衡.
- 通过动力捕捉和交叉反应证实了Si=Si双键的同解裂.
- 一个基烯-PPy附加物被成功分离和表征.
- 添加PPy显著加快了用格里格纳德试剂替代二基基原子的速度.
结论:
- 大量的化环替代剂 (Rind组) 有效地稳定反应性物种.
- 动态平衡提供了一条路径,以在现场产生和反应基烯.
- PPy起到催化剂的作用,增强了二基在替代反应中的反应性.
相关概念视频
Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.
Halogenation of Alkenes
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Formation of Halohydrin from Alkenes
An alkene, such as propene, reacts with bromine in the presence of water to yield a halohydrin. Halohydrins contain a halogen and a hydroxyl group attached to adjacent carbons. When the halogen is bromine, it is called a bromohydrin, while a chlorohydrin has chlorine as the halogen.
Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene
The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.
Radical Substitution: Allylic Bromination
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...
Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.


