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相关概念视频

Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

2.5K
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.
2.5K
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

2.7K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
2.7K
Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

2.2K
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.
2.2K
Photochemical Electrocyclic Reactions: Stereochemistry01:26

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
1.9K
Cycloaddition Reactions: Overview01:16

Cycloaddition Reactions: Overview

2.9K
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.
2.9K
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

2.4K
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
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Updated: Sep 28, 2025

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

Published on: December 16, 2022

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由染色体干扰启动的编程聚烯循环

Megan M Solans1, Vitalii S Basistyi1, James A Law1

  • 1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.

Journal of the American Chemical Society
|April 4, 2022
PubMed
概括
此摘要是机器生成的。

研究人员使用β-烯衍生物开发了一种新的聚烯循环化策略. 这种方法有效合成复杂的[4.4.1]-propellanes,改善区域选择性,并为天然产品提供新的合成途径.

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[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst
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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions

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[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst
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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
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科学领域:

  • 有机化学
  • 合成化学
  • 自然产品合成

背景情况:

  • 聚烯循环化是天然产品合成的一个关键策略.
  • 现有的仿生策略往往受到有限的区域选择性影响.
  • 进入复杂的多环基支架,如4.4.1-propellanes仍然是一个挑战.

研究的目的:

  • 开发一个新的区域选择性聚循环化策略.
  • 合成具有提高效率和基板范围的[4.4.1]-propellanes.
  • 证明新策略在天然产品合成中的实用性.

主要方法:

  • 开发一种利用β-烯衍生物的新型聚烯循环化策略.
  • 使用光诱导解来产生反热力学聚.
  • 采用赫克的循环处理来形成[4.4.1]-.

主要成果:

  • 与现有方法相比,新级联策略实现了更好的区域选择性.
  • 这种方法可以容纳广泛的富电子和缺电子 (异质) 基.
  • 证明成功地转移了纳税和萨尔维亚斯帕拉诺的总合成.

结论:

  • 开发的战略为[4.4.1]推进器提供了一个强大的新途径.
  • 这种方法克服了先前策略的区域选择性和基质范围的局限性.
  • 这种方法可以获得以前无法获得的异构阿比二烯.