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由金属复合驱动的功能化跨环的光化学合成
Maksim Royzen1, Glenn P A Yap, Joseph M Fox
1Brown Laboratories, Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
Journal of the American Chemical Society
|March 7, 2008
概括
这项研究提出了一种可扩展的方法,用于使用银酸盐染色学和光化学合成跨环烯衍生物. 连续流系统有效地将cis-异构体转化为有价值的跨环氧 octene 产品.
科学领域:
- 有机化学 有机化学
- 摄影化学的使用.
- 合成方法论 合成方法论
背景情况:
- 转环烯衍生物是有价值的合成中间体.
- 这些化合物的高效合成,特别是在温和的条件下,仍然是一个挑战.
研究的目的:
- 开发一种可扩展和高效的光化学过程,用于合成跨环烯衍生物.
- 通过金属复合和染色学,让人们可以接触到功能化的跨环烯化合物.
主要方法:
- 一种使用酸银浸的化色谱的连续流系统.
- 在循环反应循环中,cis-cyclooctene衍生物的光化学异构.
- 金属复合用于选择性保留跨环氧烯产品.
主要成果:
- 这种方法成功地合成了各种功能化的跨环氧乙烯衍生物.
- 一种5-aza-trans-cyclooctene衍生品经过了高保真度的跨环循环转化到一个六 Pyrrolizine 框架.
- 在循环化过程中观察到高立体化学转移.
结论:
- 这种可扩展的光化学合成提供了一条可靠的途径,以获得跨环烯衍生物.
- 开发的方法可以更轻松地访问复杂的异环结构与保存的烯立体化学.
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.
01:26Photochemical 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.
01:12Cycloaddition 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.
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.
01:16Cycloaddition 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.