有效的可见光光催化剂的 [2+2] 子循环添加物
Michael A Ischay1, Mary E Anzovino, Juana Du
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Journal of the American Chemical Society
|September 5, 2008
概括
三二化物 (Ru(bipy) 3Cl2) 作为可见光光催化剂,用于高效的 [2+2] 阴离子循环添加. 这种方法利用太阳光,形成具有优异的二聚体选择性,高产量的循环butan.
科学领域:
- 有机化学 有机化学
- 摄影化学的使用.
- 催化剂是一种催化剂.
背景情况:
- 可见光光催化是合成化学中快速发展的一个领域.
- 循环添加反应是有机合成中构建循环分子的基础.
- 子循环添加对于形成循环butan环很重要,但通常需要恶劣的条件.
研究的目的:
- 开发一种新的可见光光催化系统,用于 [2+2] enone 循环添加.
- 探索使用三二化物 (Ru(bipy) 3Cl2) 作为光催化剂.
- 为了在循环butan产品形成中实现高效率和多重选择性.
主要方法:
- 使用Ru(bipy) 3Cl2作为可见光照射下的光催化剂.
- 采用多种类型的烯作为基质.
- 研究涉及光生成的Ru(bipy) 3+复合体和基离子中间体的反应机制.
主要成果:
- 通过使用Ru(bipy) 3Cl2和可见光,成功地实现了 [2+2] 烯的循环添加.
- 在形成循环butan产品时观察到出色的二选择性.
- 反应以高效率和产量进行,利用太阳光作为唯一的能量来源.
结论:
- Ru(bipy) 3Cl2是一种有效的可见光光催化剂,用于 [2+2] 子循环添加.
- 拟议的机制涉及通过激发的光催化剂减少单电子的子.
- 这种方法提供了一种可持续和高效的途径,以合成有价值的循环butanes.
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.
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
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.
Thermal 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.
Thermal 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.
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