对于 [2 + 2] 循环添加反应,从光化学迁移到电化学
Issa Yavari1, Sina Shaabanzadeh1
1Department of Chemistry, Tarbiat Modares University, P.O. Box, 14115-175, Tehran 1411713116, Iran.
The Journal of organic chemistry
|June 8, 2023
概括
一种新的电化学方法可以通过 [2 + 2] 循环添加缺电子烯来简单合成循环氨酸. 这种无催化剂的方法提供了一条实用的途径,可以使用可访问的材料来实现功能化四位置换的循环.
科学领域:
- 有机化学 有机化学
- 合成化学 合成化学
- 电化学 电化学 电化学
背景情况:
- 循环butan结构在许多天然产品和生物活性化合物中普遍存在.
- 循环butanes的高效和非光化学合成途径仍未得到充分探索.
- 现有的方法往往需要复杂的程序或专门的设备.
研究的目的:
- 开发一种新的,实用的,无催化剂的电化学方法,用于循环butan合成.
- 通过电合成,探索缺电子烯的 [2 + 2] 循环添加过程.
- 建立一种易于使用的方法来制备功能化四替代循环butanes.
主要方法:
- 电化学 [2 + 2] 循环添加缺乏电子的烯酸.
- 使用易于获得和廉价的电极材料.
- 循环电压测量 (CV) 用于机械研究.
- 格拉姆尺度合成验证.
- 用于产品结构确定的X射线晶体学.
主要成果:
- 成功合成了具有多种功能组的四位置换循环butanes.
- 实现了良好的反应效率.
- 已证明与格拉姆级合成的兼容性.
- 证实了电化学方法的无催化剂性质.
- 通过CV分析获得了机械洞察力.
结论:
- 开发的电化学策略提供了一条方便而高效的途径,以获得有价值的循环butan支架.
- 这种方法绕过了光催化剂或金属催化剂的需要,简化了合成过程.
- 试剂和设备的可访问性使这种方法非常实用,用于有机合成中的更广泛应用.
相关概念视频
Cycloaddition Reactions: MO Requirements for Photochemical Activation
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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.
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Cycloaddition Reactions: Overview
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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.
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Photochemical Electrocyclic Reactions: Stereochemistry
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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
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Cycloaddition Reactions: MO Requirements for Thermal Activation
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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.
3.6K
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
2.1K
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
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