主要和次要表面群体在使用性壁的纳米孔状材料的enantioselective催化作用的影响
Andreas Kuschel1, Sebastian Polarz
1Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
Journal of the American Chemical Society
|April 20, 2010
概括
在半孔有机二氧化上固定性催化剂增强了enantioselective合成. 表面结合的催化剂表现出更好的性能,这是由于与性支持的合作效应.
科学领域:
- 材料科学 材料科学 材料科学
- 催化剂是一种催化剂.
- 有机化学 有机化学
背景情况:
- 半孔材料是催化剂固定化的有效支.
- 固定化后催化剂性能增强,特别是在enantioselective合成中,很少报告.
- 了解支持表面对绑定催化剂的影响至关重要.
研究的目的:
- 介绍一种具有状壁的新型定期订购的中孔性有机 (PMO) 材料.
- 研究固定式易斯酸中心 (Al(III)) 的催化活性和性能.
- 研究奇拉表面和邻近群体对催化性质的影响.
主要方法:
- 合成PMO材料与性构建块的合成.
- 作为易斯酸中心的Al (III) 的固定.
- 不对称的碳烯反应以评估催化性能和酶选择性 (ee值).
主要成果:
- 与表面结合的Al(III) 合的PMO材料在不对称的碳烯反应中表现出催化活性.
- 与分子参考催化剂相比,与表面结合的Al(III) 催化剂表现出明显更高的反选择性 (ee值).
- 随着在毛孔壁上添加较大的二次群体,观察到ee值的增加.
结论:
- 在定制的半孔有机材料中固定催化剂可能是有益的.
- 催化中心和邻近的表面群体之间的合作效应提高了性能,特别是当硬质因素至关重要时.
- 这些性PMO材料作为研究表面结合催化和性环境影响的宝贵模型.
更多相关视频
相关概念视频
Prochirality
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
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...
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
Heterogeneous Catalysis
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...
Chirality at Nitrogen, Phosphorus, and Sulfur
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.


