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相关概念视频

SN2 Reaction: Stereochemistry02:23

SN2 Reaction: Stereochemistry

In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
Prochirality02:05

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...
Anionic Chain-Growth Polymerization: Overview01:20

Anionic Chain-Growth Polymerization: Overview

The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
α-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview01:19

α-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview

The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester molecules in the presence of sodium metal in an aprotic solvent yields an α-hydroxy ketone product. The α-hydroxy ketone is also called acyloin, so the reaction is referred to as ‘acyloin condensation.’
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)00:53

Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)

Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule02:17

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

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...

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相关实验视频

Updated: May 15, 2026

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
06:46

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Published on: June 21, 2017

对于立体选择性烯酸插入的概念

Boris Neuwald1, Lucia Caporaso, Luigi Cavallo

  • 1Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, 78464 Konstanz, Germany.

Journal of the American Chemical Society
|December 22, 2012
PubMed
概括
此摘要是机器生成的。

这项研究合成了复合物与硫酸连接体,揭示了连接体灵活性和硬质散体影响在甲基烯酸插入中的立体控制. 不对称的配体增强了最初的立体选择性,但连续插入显示由于竞争的立体控制因素而减少了控制.

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Stereolithographic 3D Printing with Renewable Acrylates
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Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators
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Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

Published on: November 27, 2015

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Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

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Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators
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Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

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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.
  • 连接体设计 连接体设计

背景情况:

  • 帕拉复合物与硫酸联体被探索用于催化应用.
  • 了解连接体动力学和固态效应对于控制催化结果至关重要.
  • 插入反应中的立体控制仍然是催化剂的重大挑战.

研究的目的:

  • 合成和表征新型硫酸连接物及其复合物.
  • 研究连接体结构,特别是固态体积和对称性对分子运动和动力学的影响.
  • 阐明甲基烯酸盐插入到甲基键中的立体选择性,并了解控制这一过程的因素.

主要方法:

  • 合成各种对称和不对称的硫酸连接体和复合体.
  • 可变温度的NMR研究和线形状分析,以探测分子运动和确定能量障碍.
  • 使用现场NMR和密度功能理论 (DFT) 计算对甲基烯酸插入立体选择性的研究.

主要成果:

  • 成功合成了带有硫酸连接体的合物复合物.
  • 在配体和复合体中的阿里尔旋转表现出高能障碍 (44-64 kJ/mol),而固态散体增加了这些障碍.
  • 配体替代模式显著影响了第一个甲基烯酸插入,与不对称的配体实现了高达6:1的立体选择性,而连续的插入显示了立体选择性的减少.

结论:

  • 连接体灵活性和固体体积是影响催化性能的关键因素,体积增加阻碍了插入率和区域选择性.
  • 非对称的硫酸联体可以在第一个插入步骤中提供高的立体选择性.
  • 连续插入的立体选择性降低归因于竞争的enantiomorphic和链末立体控制机制,需要进一步的概念开发以改善控制.