相关实验视频

Updated: Jul 28, 2025

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

Published on: March 20, 2017

电友环烯的反应性电友环烯的反应性

Andreas Eitzinger¹, Armin R Ofial¹

¹Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 München, Germany.

Pure and applied chemistry. Chimie pure et appliquee

|May 30, 2023

概括

接受电子的环烯酸在环开放反应中充当电友. 在C2位置上的基替代剂增强了反应性,为有机合成的构建块提供了洞察力.

科学领域:

有机化学有机化学
反应机制反应机制

背景情况:

功能化环烯是有机合成中的多功能构建块.
带有电子接受群的极化环烯具有对核友的增强反应性.

研究的目的:

为了研究爱核环开放反应的动力学和机制的爱电环环旋.
为了比较环胺的反应性与相关的迈克尔添加剂.
探索C2替代剂对环烯反应性的影响.

主要方法:

在DMSO中使用thiophenolates和azide离子进行非催化环开放反应的动力学研究.
确定二次速率常数 (k2).
使用哈梅特关系对替代效应的分析.

主要成果:

电友性环烯经历S_N2型环开反应.
与C2处的基替代剂的环烯与非替代类型相比,表现出较高的反应速度.
观察到抛物线式哈梅特关系与基电子性质的变化.

结论:

这项研究阐明了电友环烯的固有S_N2反应性.
C2 基替代剂显著影响了环烯环开放的速率和机制.
这些发现为功能化环烯的合成应用提供了宝贵的见解.

关键词:

在ICPOC-25中,运动学的动力学.线性自由能量关系是线性的.核爱的人是核爱的人.环开放反应的反应.结构-反应性结构-反应性

更多相关视频

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

Published on: February 6, 2019

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Published on: May 21, 2019

相关概念视频

Thermal and Photochemical Electrocyclic Reactions: Overview

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.

Pericyclic Reactions: Introduction

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...

Cycloaddition Reactions: Overview

Cycloaddition 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.

Radical Reactivity: Electrophilic Radicals

Radical Reactivity: Electrophilic Radicals

Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a...

Photochemical Electrocyclic Reactions: Stereochemistry

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

Acid-Catalyzed Ring-Opening of Epoxides

Acid-Catalyzed Ring-Opening of Epoxides

Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...