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相关概念视频

Stereoisomerism of Cyclic Compounds02:33

Stereoisomerism of Cyclic Compounds

11.4K
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,...
11.4K
Cycloaddition Reactions: MO Requirements for Thermal Activation01:16

Cycloaddition Reactions: MO Requirements for Thermal Activation

4.9K
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.
4.9K
Prochirality02:05

Prochirality

5.1K
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...
5.1K
Woodward–Hoffmann Selection Rules and Microscopic Reversibility01:34

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

4.1K
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
4.1K
Stability of Substituted Cyclohexanes02:30

Stability of Substituted Cyclohexanes

16.4K
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
16.4K
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.6K
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.
2.6K

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相关实验视频

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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
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在共价2+2宏循环化中,分子间堆叠指导的基拉尔偏好.

Zhen-Sheng Huang1, Wen-Rong Wang1, Fang-Hong Yang1

  • 1Department of Chemistry, College of Chemistry and Chemical Engineering and the MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, Xiamen University, Xiamen 361005, China.

JACS Au
|February 27, 2026
PubMed
概括

这项研究揭示了宏循环化反应中意想不到的性偏好. 通过使用特定的氨基酸基反应剂,研究人员实现了异体性宏循环的高产量,由分子间堆叠而不是分子内结合驱动.

关键词:
阳离子受体是一种阳离子受体.合体自我分类.宏观周期堆叠是指一个宏观周期堆叠.型多米米特的宏观循环.立体选择性宏观循环化

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科学领域:

  • 超分子化学 超分子化学
  • 有机合成 有机合成
  • 立体化学是一种立体化学.

背景情况:

  • 宏循环反应对于合成复杂分子至关重要.
  • 在宏循环化中,基拉的偏好通常依赖于分子内相互作用和驱动的过程.
  • 在宏观循环形成中控制立体化学是合成化学的一个重大挑战.

研究的目的:

  • 为了研究2 + 2宏循环化反应中的性偏好.
  • 探索分子间相互作用在立体选择性宏循环形成中的作用.
  • 建立一个新的策略,用于无催化剂,立体选择性宏循环.

主要方法:

  • 与阿奇拉尔1,4-二二二酸化物反应的种族或二二二二二化物.
  • 使用氨酸 (A) 基和氨酸 (F) 基二化物.
  • 使用分析技术 (隐含) 分析产品产量和立体化学结果.

主要成果:

  • 在高产量 (大约) 中,只形成异体的宏循环 (例如,L,L,D,D-AAAA). 80%) 来自赛血基的原材料.
  • 已证明对氨酸和混合氨基酸基二化物有异体性偏好.
  • 观察到偏好L,D,D,L-AAAA而不是L,D,L,D-AAAA来自中位二化物.
  • 鉴定了增强的跨宏循环堆叠作为激素偏好的驱动力.
  • 受青的宏循环在堆叠时表现出更对称的形状,从而增加了热稳定性 (30-40°C更高的分解温度).

结论:

  • 建立了一种新的,无催化剂的方法,用于通过分子间堆叠驱动的立体选择性宏循环.
  • 证明了可以利用分子间相互作用来控制宏循环立体化学,与传统驱动的同偏好正交.
  • 这项工作为设计宏环化合物的立体选择性合成策略提供了一个新的范式.