在水性有机双相系统中,催化 [2 + 2 + 2] 循环化
Hidenori Kinoshita1, Hiroshi Shinokubo, Koichiro Oshima
1Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan.
Journal of the American Chemical Society
|June 26, 2003
概括
使用triynes的催化宏循环在双相系统中实现. 这种方法控制了基质度,并使得疏水性和疏水性基因的选择性交叉取消成为可能.
科学领域:
- 有机化学 有机化学
- 催化剂是一种催化剂.
- 绿色化学 绿色化学
背景情况:
- 宏循环对于合成复杂的有机分子至关重要.
- 传统方法通常需要稀释条件或缓慢添加,使程序复杂化.
- 催化 [2+2+2] 无效提供了一个对宏观循环的强大途径.
研究的目的:
- 开发一种高效和选择性的宏循环化方法,使用催化分子内 [2+2+2] 取消.
- 探索使用水性有机双相系统来控制反应条件和基质度.
- 为了实现疏水性和疏水性基因之间的选择性交叉取消.
主要方法:
- 采用催化剂进行分子内 [2+2+2] 取消三.
- 使用水性有机双相系统来管理基质的溶解度和度.
- 研究不同疏水性的二烯和烯之间的选择性交叉取消反应.
主要成果:
- 在双相系统中成功实现了triynes的宏循环化.
- 双相系统有效地控制了水相中的基质度,模仿稀释条件而不加缓慢添加.
- 证明了疏水性二氨酸和疏水性氨酸之间的选择性交叉取消.
结论:
- 水性有机双相系统为催化宏循环提供了一个实用和高效的平台.
- 这种方法提供了对反应条件和选择性的增强控制,特别是对于具有不同溶解度的基质.
- 该方法为合成复杂的宏循环结构提供了一个更绿色的替代方案.
相关概念视频
01:26Thermal 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.
01:17Thermal 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.
01:26Photochemical 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
01:16Cycloaddition 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.
01:17Pericyclic 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...
01:12Cycloaddition 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.