在生物和合成过程中的更高阶电循环
Abel de Cózar1,2, Ana Arrieta1, Iosune Arrastia1
1Departamento de Química Orgánica I, Facultad de Química, Universidad del País Vasco and Donostia International Physics Center (DIPC), P. K. 1072, 20018, San Sebastián-Donostia, Spain.
ChemPlusChem
|September 27, 2023
概括
较高阶的电循环 (1018 π电子) 可以偏离伍德沃德-霍夫曼规则. 本综述考察了这些反应,包括DFT计算,揭示了对周环拓和实验选择性的洞察.
科学领域:
- 有机化学 有机化学
- 物理化学 物理化学
- 计算化学计算化学
背景情况:
- 电循环化通常会遵守最多八个π电子的伍德沃德-霍夫曼规则.
- 从这些规则的偏差观察到更高阶的电循环反应与增加的π电子系统.
研究的目的:
- 审查涉及10,12,14,16和18π电子的更高阶电循环.
- 为了突出这些反应对生物活性化合物的合成实用性.
- 通过计算研究阐明反应机制.
主要方法:
- 关于报告的更高阶电循环的文献综述.
- 包含密度函数理论 (DFT) 计算,用于缺乏先前计算分析的系统.
- 围绕周期的拓的分析.
主要成果:
- 详细研究了涉及10至18π电子的电循环.
- 确定特定的例子,作为合成生物活性分子的中间体.
- 证明DFT在解释观察到的实验选择性的作用.
结论:
- 高阶电循环呈现出超出已建立的伍德沃德-霍夫曼规则的独特反应模式.
- 计算化学,特别是DFT,对于理解这些反应的机制细节和选择性至关重要.
- 这些反应为构建复杂的有机分子提供了有价值的途径.
相关概念视频
Thermal and Photochemical Electrocyclic Reactions: Overview
2.4K
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.
2.4K
Thermal Electrocyclic Reactions: Stereochemistry
2.0K
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.
2.0K
Photochemical 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
Cycloaddition Reactions: Overview
2.6K
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.
2.6K
Pericyclic Reactions: Introduction
8.4K
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...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic...
8.4K
Cycloaddition Reactions: MO Requirements for Photochemical Activation
2.1K
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.
2.1K


