![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)
使用理论和光谱学调节光化驱动的循环添加
Jiao Yu J Wang1, Mitchell T Blyth1, Michael S Sherburn1
1Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
Journal of the American Chemical Society
|January 7, 2022
概括
本研究使用计算和实验方法探索光化/迪尔斯-阿尔德 (PEDA) 反应序列. PEDA序列与碳烯具有广泛的适用性,而硫烯和胺则具有独特的反应性挑战和机遇.
科学领域:
- 有机光化学
- 计算化学
- 反应机制研究
背景情况:
- 光化/迪尔斯-阿尔德反应是一种强大的合成工具.
- 了解PEDA序列的范围和局限性对于其应用至关重要.
- 之前的研究没有全面研究影响PEDA反应性的因素.
研究的目的:
- 进行PEDA序列的广泛调查.
- 检查各种替代剂和反应伙伴对PEDA反应的影响.
- 探索相应反应途径的潜力,如光化/单体添加 (PECA).
主要方法:
- 使用SMD溶解的M06-2X/6-31+G{d,p) 计算.
- 通过实验性紫外线光谱来支持计算结果.
- 研究了一组具有不同电子和结构性质的20个prodienes和20个dienophiles的测试组.
主要成果:
- PEDA序列对碳基prodienes中的大多数替代模式具有耐受性.
- 由于系统间的交叉和相互竞争的原子转移途径,硫衍生物的反应速度较慢.
- 在激发状态下,基胺表现出更高的障碍物,但如果克服,可以轻易地经历PEDA.
- 迪尔斯-阿尔德反应的范围比之前报告的更广泛,可能涉及乙烯和富电子的基.
- 预计一氧化碳 (CO) 将经历一个简单的 (4+1) 基质添加 (PECA),而不是一个 [4+2] 基质添加.
结论:
- PEDA序列是一种多功能反应,具有广泛的适用性,特别是对于碳烯.
- 硫和胺衍生物具有独特的反应性,可以在特定条件下加以利用.
- 新的光化/切莱特罗普添加 (PECA) 序列提供了一个无金属的路径,用于化环.
相关概念视频
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
2.2K
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.
2.2K
01:16Cycloaddition Reactions: Overview
2.9K
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.
2.9K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
1.9K
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
1.9K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.5K
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.
2.5K
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
3.8K
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.
3.8K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.1K
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.
2.1K