不对称的克莱森重新排列,由催化不对称的Di (((Allyl) 乙烯合成实现
1Department of Chemistry, University of Pittsburgh, Pennsylvania 15260, USA. sgnelson@pitt.edu
Journal of the American Chemical Society
|March 30, 2006
概括
本研究介绍了一种两步方法,结合了催化不对称合成和烯酸异构化-克莱森重组,以实现高效的非对称的形克莱森重组. 这种方法产生了高度立体控制的2,3-不替代的4 - 五元制衍生物,展示了它的合成效用.
科学领域:
- 有机化学 有机化学
- 不对称的合成方法
背景情况:
- 亚利法克莱森重组对于合成复杂分子至关重要.
- 开发用于不对称的阿里法特克莱森重排的高效方法仍然是一个挑战.
研究的目的:
- 建立一个方便的两步路径,以实现非对称的阿里法特克莱森重排.
- 在合成2,3-非替代的4 - pentenal衍生物中实现出色的相对和绝对立体控制.
主要方法:
- 催化不对称合成二 () 乙烯.
- 随后的素异构-克莱森重组 (ICR) 反应.
主要成果:
- 成功结合了二 () 乙烯合成和ICR反应.
- 高产量和优秀的立体控制 (相对和绝对) 的目标乙醇衍生物.
- 在 (+) - 卡洛二甲基乙醇的催化酶选择性合成中证明有用性.
结论:
- 开发的两步协议为非对称的阿里法特克莱森重排提供了一个实用和高效的途径.
- 这种方法对复杂分子合成和不对称合成企业有价值.
相关概念视频
Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic β-ketoester as the final product. Commonly, 1, 6 and 1, 7-diesters are preferred substrates for the reaction since the generated five, and six-membered cyclic β-keto esters are particularly more stable.
β-Dicarbonyl Compounds via Crossed Claisen Condensations
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction involving esters, with both containing α hydrogen, results in a mixture of four different products that are difficult to isolate. This reduces the synthetic utility of the reaction.
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.
[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.
Esters to β-Ketoesters: Claisen Condensation Mechanism
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...
[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.


