正式的 [2 + 2 + 2] 循环添加策略是基于分子内基酶反应/Diels-Alder循环添加级联
Julia M Robinson1, Takeo Sakai, Katsuhiko Okano
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Journal of the American Chemical Society
|August 12, 2010
概括
本研究介绍了一种新的,无金属的 [2 + 2 + 2] 循环添加策略. 它利用一连串的循环反应,包括一个propargylic ene反应和一个Diels-Alder反应,以形成复杂的循环结构.
科学领域:
- 有机化学 有机化学
- 合成化学 合成化学
- 反应机制 反应机制
背景情况:
- 循环添加反应是有机合成的基础.
- 无金属的催化方法对于可持续化学是非常可取的.
- 了解反应机制对于开发新的合成策略至关重要.
研究的目的:
- 开发一种新的,没有金属的 [2 + 2 + 2] 循环添加策略.
- 研究涉及1,6-diynes的级联环周反应的机制.
- 探索循环加法过程的区域选择性和异地选择性.
主要方法:
- 在1,6-diynes.的分子内基反应中.
- 与基或基基二烯醇的分子间或分子内迪尔斯-阿尔德反应.
- 对区域选择性和异地选择性反应产物的分析.
主要成果:
- 一连串的两个循环过程被成功地用于 [2 + 2 + 2] 循环加法.
- 与非对称的二烯基分子的反应显示出良好的优秀的区域选择性.
- 观察到高立体选择性,仅产生内循环载荷管道.
- 针对基尼尔二烯的,提出了一种涉及异二烯类型中间体的新型机制.
结论:
- 开发的战略为复杂的循环化合物提供了一种多功能和高效的无金属途径.
- 这些发现为级联环周反应提供了新的机理洞察力.
- 这项工作有助于在有机化学中推进可持续的合成方法.
相关概念视频
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.


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