四胺环来自Mukaiyama-Michael级联反应的环
Megan L Bolla1, Brian Patterson, Scott D Rychnovsky
1Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, USA.
Journal of the American Chemical Society
|November 17, 2005
概括
一种新的无效反应从醇乙烯和不和子/ Ester 产生四基. 这一过程涉及Mukaiyama-Michael的添加,其次是2-oxonia-Cope的重新排列,产生有价值的循环化合物.
科学领域:
- 有机化学 有机化学
- 合成化学 合成化学
- 反应方法的反应方法.
背景情况:
- 四基是天然产品和药品中普遍存在的结构图案.
- 在有机合成中,高效和立体选择性的合成路径对四基类素非常受欢迎.
- 现有的方法通常需要多个步骤或缺乏广泛的基质范围.
研究的目的:
- 发现和描述一种用于合成四胺基的新无效反应.
- 调查反应机制,包括关键中间体和重组.
- 探索新开发的反应的范围和立体化学结果.
主要方法:
- 同性乙醇乙烯与各种α,β不和和的反应.
- 涉及拟议的Mukaiyama-Michael添加和2-oxonia-Cope重组的机制研究.
- 使用奇拉基质和不同不和伙伴的立体选择性分析.
主要成果:
- 一个新的无效反应有效地产生四基.
- 反应通过Mukaiyama-Michael加法进行,然后再进行2-oxonia-Cope重组.
- 观察到某些基质 (例如,3-布-2-one) 具有立体选择性,而其他基质则产生二聚体混合物 (例如,乙烯酸盐);用复杂的子获得化环产品,并且保持了光学活性.
结论:
- 已经建立了一个新的和高效的合成路径到四基.
- 反应机制涉及一连串明确的离子中间体.
- 该方法提供了一个有价值的工具,用于构建替代的四基,具有立体化学控制和复杂分子合成中的应用潜力.
相关概念视频
Conjugate Addition of Enolates: Michael Addition
The attack of a nucleophile at the β carbon of an α,β-unsaturated carbonyl compound is called conjugate addition. Conjugate addition reactions of active methylene compounds, such as β-diketones, β-keto esters, β-keto nitriles, and α-nitro ketones, are called Michael addition reactions.
[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.
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview
In the presence of an aqueous base and a halogen, primary amides can lose the carbonyl (as carbon dioxide) and undergo rearrangement to form primary amines. This reaction, called the Hofmann rearrangement, can produce primary amines (aryl and alkyl) in high yields without contamination by secondary and tertiary amines.
Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
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.
Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
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