直接可见光激发不对称的分子间 [2+2] 光环添加物的易斯酸催化
Xiaoqiang Huang1, Taylor R Quinn2, Klaus Harms1
1Fachbereich Chemie, Philipps-Universität Marburg , Hans-Meerwein-Strasse 4, 35043 Marburg, Germany.
Journal of the American Chemical Society
|June 24, 2017
概括
这项研究引入了一种新型的可见光激活反应,用于立体控制的 [2+2] 循环添加. 这种方法有效地产生循环,包括复杂的四级立体中心.
科学领域:
- 有机化学
- 光催化
- 不对称的合成
背景情况:
- 化酸催化对于立体选择性合成至关重要.
- 可见光光催化提供了可持续和温和的反应条件.
- 开发构建四元立体中心的方法仍然是一个重大挑战.
研究的目的:
- 报告一种使用可见光和易斯酸的新反应设计.
- 为了实现高度立体控制的分子间 [2+2] 循环加法.
- 用邻近的全碳四元立体中心合成循环.
主要方法:
- 采用基质结合的复合物作为易斯酸催化剂.
- 使用可见光产生催化剂的激发状态.
- 与各种辅助基质进行分子间 [2+2] 循环添加.
主要成果:
- 反应以高度立体控制的方式进行,产生循环.
- 达到优异的反选择性 (高达99% ee) 和异选择性 (高达20:1 d.r.) ) 的情况.
- 证明能够在分子间形成邻近的全碳四分体立体中心,包括螺旋环结构.
结论:
- 开发的方法为复杂的循环butan衍生物提供了有效的途径.
- 可见光激活易斯酸可以实现新的不对称转换.
- 这种方法扩大了构建具有挑战性的立体中心的工具包.
相关概念视频
Cycloaddition Reactions: MO Requirements for Photochemical Activation
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Cycloaddition Reactions: MO Requirements for Thermal Activation
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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.
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Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
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[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
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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.
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Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
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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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