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相关概念视频

Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal 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.
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

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.
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

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
Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

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

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...
Pericyclic Reactions: Introduction01:17

Pericyclic Reactions: Introduction

Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...

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相关实验视频

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Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of &#945;-Imino &#947;-Lactones and Alkylidene Pyrazolones
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Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Published on: February 7, 2019

通过循环烯的重建性碳化,通过涉及C[键]C键裂变的循环烯的快速催化合成pyranopyrandiones.

Teruyuki Kondo1, Yushi Kaneko, Yoshinori Taguchi

  • 1Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.

Journal of the American Chemical Society
|June 13, 2002
PubMed
概括

一种新的催化反应使得从环烯中合成pyranopyrandiones. 这种方法为功能单体和非对称的pyranopyrandiones提供了一条新的途径.

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Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
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Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Published on: June 10, 2021

科学领域:

  • 有机化学 有机化学
  • 催化剂是一种催化剂.
  • 聚合物科学 聚合物科学

背景情况:

  • 环二烯是具有独特反应性的紧张循环分子.
  • 催化剂在有机合成中广泛用于各种转换.

研究的目的:

  • 开发一种新的合成路径,使pyranopyrandiones.
  • 探索催化反应对于C-C键裂解和碳化反应的实用性.

主要方法:

  • 催化碳酸盐二聚化循环烯.
  • 在一氧化碳下,二烯基cyclopropenone与Ru3 ((CO) 12和NET3的反应.
  • 催化碳酸性合环烯和基的结合.

主要成果:

  • 在81%的产量中成功合成了3,4,7,8-tetrapropylpyrano[6,5-e]pyran-2,6-dione.
  • 制备新型功能单体和非对称替代的pyranopyrandiones.
  • 在循环烯中证明了C-C键裂变.

结论:

  • 催化提供了一种有效的方法来合成pyranopyrandione.
  • 开发的方法为功能单体和复杂的pyranopyrandione结构提供了一种多功能方法.