二,二,六,六四甲基皮化物介导的环氧化物的α和β-化:依赖溶剂的机制
Sean H Wiedemann1, Antonio Ramírez, David B Collum
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Journal of the American Chemical Society
|December 18, 2003
概括
二,二,六,六四甲基化物 (LiTMP) 能够有效地对环氧化物进行α和β化. 溶剂选择对LiTMP聚合和反应机制产生重大影响,影响有机合成的结果.
科学领域:
- 有机化学 有机化学
- 有机金属化学 有机金属化学
- 反应机制 反应机制
背景情况:
- 胺是有机合成中的关键基.
- 二,二,六,六四甲基化物 (LiTMP) 是一种固态阻碍的胺基.
- 了解LiTMP的反应性和机制对于其有效应用至关重要.
研究的目的:
- 为了研究由LiTMP调解的环氧化物的α-和β-化.
- 为了比较LiTMP与二醇胺 (LDA) 的反应性.
- 阐明LiTMP介导反应的机械差异和溶剂效应.
主要方法:
- 在THF和Me2NEt中使用LiTMP的实验动力学研究.
- 化环氧化物中间体的合成和表征.
- 密度函数理论 (DFT) 计算用于检查过渡结构.
主要成果:
- 在环氧化物化中,LiTMP的反应性比LDA更高.
- 阿尔法化通过单溶解二次体进行,导致跨环状C-H插入.
- 贝塔化途径根据溶剂不同:THF中的单体,Me2NEt中的二元.
- LiTMP的依赖溶剂的聚合会影响反应速率和机制.
结论:
- LiTMP是用于选择性环氧化物功能化的强有力的试剂.
- 溶剂选择关键控制LiTMP聚合状态和反应途径.
- DFT计算为这些化反应的过渡状态提供了洞察力.
相关概念视频
Free-Radical Chain Reaction and Polymerization of Alkenes
The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
Oxidation of Alcohols
In this lesson, the oxidation of alcohols is discussed in depth. The various reagents used for oxidation of primary and secondary alcohols are detailed, and their mechanism of action is provided.
The process of oxidation in a chemical reaction is observed in any of the three forms:
The process of oxidation in a chemical reaction is observed in any of the three forms:
Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Radical Autoxidation
The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form hydroperoxide. Autoxidation involves initiation, propagation, and termination steps. Many organic compounds are susceptible to autoxidation—especially ethers in the presence of oxygen, which form hydroperoxides. Even though this reaction is slow, old ether bottles contain small amounts of peroxide, which leads to laboratory explosions during ether...
Radical Chain-Growth Polymerization: Mechanism
The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this species into the...


