烯合双[12]烯,通过光或热进行跨环基循环添加
Aiko Fukazawa1, Hiroya Oshima, Yoshihito Shiota
1Department of Chemistry, Graduate School of Science, Nagoya University, Furo, Chikusa, Nagoya 464-8602, Japan. aiko@chem.nagoya-u.ac.jp
Journal of the American Chemical Society
|January 30, 2013
概括
一个新的硫融合宏循环通过光或热进行 [2+2] 基环添加. 这种反应对于创建新的π支架至关重要,避免了过渡金属,并为电子应用提供了潜力.
科学领域:
- 有机化学 有机化学
- 材料科学 材料科学 材料科学
- 超分子化学 超分子化学
背景情况:
- 具有结合系统的宏环化合物对于先进材料至关重要.
- 硫-化无烯具有独特的电子和结构性质.
- 在应力宏循环中控制循环加法反应是一个合成的挑战.
研究的目的:
- 合成一种新型的bisdehydro[12]annulene衍生物,其结构与 thiophene 融合.
- 在热和光化学条件下研究 [2+2] 基环载管的形成.
- 探索由此产生的循环载荷管道作为电子应用的π支架的潜力.
主要方法:
- 合成一种与烯融合的双[12]annulene.
- 宏观循环的光照射和热处理.
- 理论计算 (例如,密度函数理论) 来阐明反应机制.
主要成果:
- 成功合成了基基合 bisdehydro [12]annulene 的目标.
- 在光解和热条件下,在没有过渡金属的情况下,有效的 [2+2] 基环载管形成.
- 理论分析揭示了不同的机制:异步协调 [2+2]用于光化学和连续的电循环反应的热路.
- 鉴定出硫融合对于使循环添加成为可能至关重要.
结论:
- 一个新型的硫融合宏循环很容易经历无金属 [2+2] 基循环添加.
- 反应机制在光化学和热激活之间有所不同.
- 由此产生的硫融合双烯是电子材料的有前途的新型多环 π 架构.
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01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
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.
01:16Cycloaddition 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.
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.
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).