一个帕拉催化基化的对的研究
Joaquín López-Serrano1, Simon B Duckett, Stuart Aiken
1Department of Chemistry, University of York, Heslington, York, U.K.
Journal of the American Chemical Society
|May 2, 2007
概括
帕拉复合物与bcope和tbucope连接体催化了二乙烯转化. 对的研究揭示了磁化转移机制和中间物种,为催化通路提供了洞察力.
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.
- 反应机制 反应机制
背景情况:
- 复合物是有机合成中的关键催化剂.
- 了解反应中间体是优化催化过程的关键.
- 准 (PH) 是NMR光谱学中机械学研究的宝贵工具.
研究的目的:
- 通过使用新型复合体,研究二乙烯的催化转化.
- 通过对和NMR光谱学阐明反应机制.
- 描述在催化循环中形成的关键中间体.
主要方法:
- 复合物的合成和表征 [Pd(bcope) ((OTf) 2) (1a) 和 [Pd(tbucope) ((OTf) 2) (1b).
- 催化转化二甲乙烯.
- 超诱导极化 (PHIP) NMR光谱用于研究反应中间体和磁化转移.
主要成果:
- 复合物1a和1b有效地催化了二乙烯的转化为 stilbenes 和 diphenylethane.
- 使用PHIP的NMR进行中介物[Pd(bcope) ((CHPhCH2Ph) ] ((OTf) (2a) 和[Pd(tbucope) ((CHPhCH2Ph) ] ((OTf) (2b) 的表征.
- 详细分析了从连接体质子到产品的磁化转移途径,揭示了不同溶剂和像皮里丁这样的添加剂中的不同的机制.
结论:
- 这项研究为催化乙烯转化提供了机械洞察力.
- 准NMR光谱在识别短暂的中间体和绘制磁化传输路径方面是有效的.
- 连接体和溶剂的性质显著影响了催化途径和中间体的形成.
相关概念视频
Reduction of Alkenes: Catalytic Hydrogenation
Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Radical Anti-Markovnikov Addition to Alkenes: Overview
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.


