红素酸和红素酸Ru复合体之间的反应性和选择性差异. 关于立体选择性烯转化催化剂设计的含义
R Kashif M Khan1, Sebastian Torker, Amir H Hoveyda
1Department of Chemistry, Merkert Chemistry Center, Boston College , Chestnut Hill, Massachusetts 02467, United States.
Journal of the American Chemical Society
|October 1, 2014
概括
甲基酸盐复合物在烯转化过程中意外地获得了高的Z选择性. 与甲基醇酸盐不同,它们保持结构完整性,并在金属循环butan形成过程中确定立体化学,而不是基协调.
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.
- 有机合成 有机合成
背景情况:
- 奥莱芬转化是有机合成中的一个关键反应.
- 实现高立体选择性,特别是Z选择性,仍然是一个挑战.
- 复合物是广泛使用的催化剂,用于olefin转化.
研究的目的:
- 为了阐明Ru catechothiolate复合体中意想不到的Z选择性的起源.
- 了解氨酸转化中的甲基和甲基 Ru 复合物的机制差异.
- 修订现有模型对氨酸转化中的Z选择性.
主要方法:
- 合成和表征Ru catechothiolate和catecholate复合物. 这些复合物中含有:
- 在olefin转化反应中对催化活性和Z选择性的评估.
- 密度函数理论 (DFT) 计算以探测反应机制.
主要成果:
- 鲁甲基酸盐复合物表现出异常的Z-选择性,与甲基酸盐衍生物不同.
- 在反应条件下,catechothiolate复合物保持结构完整性,而catecholates则降解.
- DFT计算显示,立体化学是在甲基环丁酸盐形成期间确定的,与甲基环丁酸盐的基协调形成形成对比.
结论:
- 鲁甲基酸盐复合物的增强Z选择性源于它们独特的机械路径.
- 除了硬体,结构完整性和电子因素对于控制Z选择性至关重要.
- 这项研究需要修订当前的立体选择性模型在olefin转化.
相关概念视频
01:13Olefin Metathesis Polymerization: Overview
1.8K
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
1.8K
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
2.6K
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...
2.6K
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
13.8K
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
13.8K
01:22Heterogeneous Catalysis
134
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
134
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
8.4K
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
8.4K
01:20Radical Reactivity: Concentration Effects
1.1K
In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and an alkene, in the presence of tin hydride and AIBN, begins with the generation of a tin radical. The generated radical then abstracts halogen from the alkyl halide, producing an alkyl radical. This alkyl radical can either react with tin hydride, yielding an alkane, or add to an alkene, generating a nitrile-stabilized radical, eventually...
1.1K