[3+2]通过可见光光催化剂的循环添加阿里环基
Zhan Lu1, Meihua Shen, Tehshik P Yoon
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
Journal of the American Chemical Society
|January 11, 2011
概括
研究人员开发了一种新的光催化方法,用于合成替代环丹. 这种方法利用烯基环基和烯酸,通过一电子还原开始基基离子形成.
科学领域:
- 有机化学 有机化学
- 光催化作用的光催化
- 合成方法论 合成方法论
背景情况:
- 环丹环是天然产品和药品中普遍存在的结构图案.
- 在合成化学中,构建高置换性环丹的高效方法至关重要.
- 现有的合成路线可能缺乏多功能性或需要恶劣的条件.
研究的目的:
- 为了引入一个新的正式的 [3+2] 反应用于环丹合成.
- 开发一种光催化方法,使用易于获得的原始材料.
- 为了在产生的环丹环上实现高水平的替代.
主要方法:
- 采用一个光催化系统,涉及鲁 (Ruthenium) ((II) 三二) ([Ru(bpy) 3) ((2+)),兰三甲酸盐 (La(OTf) 3) 和四甲基乙二胺 (TMEDA).
- 使用阿里环基和奥莱芬作为关键反应伙伴.
- 通过将子减少为基离子的一电子来启动反应.
主要成果:
- 成功地生成了高度替代的环旋环系统.
- 一个新的正式 [3+2] 循环加法路径的演示.
- 光催化系统有效地促进了关键的激素离子中间体的形成.
结论:
- 报告的方法提供了一个高效和多功能途径,以替代环丹.
- 光催化为C-C键形成提供了一种温和而有效的策略.
- 这项工作扩大了构建复杂循环结构的工具包.
相关概念视频
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.
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.
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
[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.
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
