在双重氧-科普/克莱森/乙烯反应中,高效地从宏环形状转移性
Effiette L O Sauer1, Louis Barriault
1Department of Chemistry, 10 Marie Curie, University of Ottawa, Ottawa, Canada K1N 6N5.
Journal of the American Chemical Society
|July 9, 2004
概括
这项研究详细介绍了三种立体选择性环周反应的级联,合成了具有两个相邻四分位中心的十骨. 这种高效的过程涉及氧-科普重组,克莱森重组,以及一个跨环状热反应.
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:
- 周环反应对于构建复杂的分子架构至关重要.
- 在有机化学中,用四元中心合成Decalin骨是一个重大挑战.
研究的目的:
- 开发一种用于合成Decalin骨的新型级联反应.
- 为了在两个连续的四元中心的形成中实现高立体选择性.
- 为了阐明双重氧-科普/克莱森/反应的机制.
主要方法:
- 采用了三步级联反应序列.
- 反应序列涉及一个氧-科普重组,一个克莱森[3,3]转移,和一个跨环状 ene 反应.
- 进行了机械分析,以了解立体选择性.
主要成果:
- 成功合成了具有两个连续四元中心的Decalin骨架.
- 在级联反应中实现了高立体选择性.
- 确定了关键的中间体:一个有10个成员的环乙醇宏循环和一个E-cyclodec-6-en-1-one.
结论:
- 开发的级联反应为复杂的Decalin结构提供了有效的途径.
- 高立体选择性归因于双重反应的特定机械路径.
- 这项工作为访问功能密集的Decalins提供了有价值的合成策略.
相关概念视频
Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
Pericyclic Reactions: Introduction
Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...
[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement
The Claisen rearrangement is a [3,3] sigmatropic rearrangement of allyl vinyl ethers to unsaturated carbonyl compounds. The rearrangement is a concerted pericyclic reaction proceeding via a chair-like transition state.


