通过代环融合策略扩展 [23]-烯具有特殊的手术性质
Gavin R Kiel1, Harrison M Bergman1, Adrian E Samkian1
1Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.
Journal of the American Chemical Society
|December 16, 2022
概括
研究人员合成了多达23个环的新型扩展基因,实现了高反化障碍. 这一突破使得能够分离出具有特殊光学特性的稳定,纯净的螺旋式纳米碳.
科学领域:
- 有机化学
- 纳米材料科学
- 整形眼镜光谱
背景情况:
- 扩展的螺旋体是具有独特结构和潜在的手术性质的螺旋式纳米碳体.
- 低反化障碍阻碍了对它们预测性能的实验研究.
研究的目的:
- 合成和描述具有增加环数的新型扩展基.
- 研究分子结构与化障碍之间的关系.
- 为了实现稳定的 enantiopure 扩展的 helicenes 用于手术应用.
主要方法:
- 通过代的Ir-催化 [2 + 2 + 2] 循环添加反应合成膨胀的基.
- 使用可变温度的NMR光谱测定化自由能障碍 (ΔG‡e).
- 测量循环二重体 (CD) 不对称因素.
主要成果:
- 成功合成了15个,19个和23个环的扩展.
- 证明了环数和 ΔG‡e 之间的线性相关性.
- 膨胀的 [23]-呈现出高的 ΔG‡e (29.2 ± 0.1 kcal/mol),在室温下停止了反分子化.
- 乙二烯显示显著增强的CD不对称系数 (±0.056在428nm).
结论:
- 这项研究提供了一个可行的合成途径,
- 增加的分子长度和直径有效地提高了化障碍,使稳定的分离成为可能.
- 这些发现为开发具有卓越光学性能的先进分子材料提供了设计原则.
相关概念视频
02:38Electrophilic Addition to Alkynes: Halogenation
8.5K
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
8.5K
01:18Aromatic Hydrocarbon Cations: Structural Overview
2.9K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
2.9K
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
02:33Stereoisomerism of Cyclic Compounds
9.1K
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
9.1K
02:05Prochirality
3.9K
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
3.9K
02:02Chair Conformation of Cyclohexane
14.9K
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this...
14.9K