Video Experimental Relacionado
Updated: Jul 24, 2026
09:45
Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
Catálisis asimétrica de la reacción de cicloadición [5 + 2] de los vinilciclopropanos y los sistemas pi
Paul A Wender1, Lars O Haustedt, Jaehong Lim
1Department of Chemistry, Stanford University, Stanford, California 94305, USA. wenderp@stanford.edu
Journal of the American Chemical Society
|May 11, 2006
Resumen
Los investigadores desarrollaron catalizadores de rodio altamente selectivos para las cicloadiciones catalizadas por metales [5 + 2]. Estos catalizadores convierten eficientemente los vinilciclopropanos (VCP) y los sistemas pi en moléculas complejas con un alto exceso enantiomérico.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis es la catálisis.
- Síntesis asimétrica de síntesis.
Sus antecedentes:
- Las cicloadiciones catalizadas por metales son cruciales para la síntesis orgánica.
- Los complejos de rodio (I) han demostrado ser prometedores en la catalización de [5 + 2] cicloadiciones de vinilciclopropanos (VCP) y sistemas pi.
- Trabajos anteriores demostraron que los catalizadores de Rh (I) funcionan bajo condiciones suaves.
Objetivo del estudio:
- Para evaluar comparativamente los catalizadores quirales para la cicloadición [5 + 2] catalizada por el rodio.
- Para evaluar el rendimiento de un catalizador preferido, [((R) -BINAP) Rh] + SbF6-, con varios sustratos.
- Desarrollar un modelo predictivo para la selectividad de reacción.
Principales métodos:
- Cribado de múltiples catalizadores quirales de rodio.
- Prueba del catalizador optimizado con diversos sustratos de vinilciclopropano y sistema pi.
- Análisis del exceso enantiomérico (ee) utilizando cromatografía quiral.
- Desarrollo de un modelo computacional para la predicción de selectividad.
Principales resultados:
- Se evaluaron varios catalizadores quirales para la [5 + 2] cicloadición.
- El catalizador preferido, [((R) -BINAP) Rh]+SbF6-, logró una alta enantioselectividad (>95% ee) para varias combinaciones de sustratos.
- La sustitución del sustrato y el tipo de sujeción influyeron significativamente en la selectividad.
- Se desarrolló con éxito un modelo predictivo para la selectividad.
Conclusiones:
- Los catalizadores quirales de rodio, en particular [((R) -BINAP) Rh] + SbF6-, permiten cicloadiciones altamente enantioselectivas [5 + 2].
- El modelo predictivo desarrollado ayuda a comprender y controlar los resultados de la reacción.
- Este trabajo avanza en el campo de las cicloadiciones asimétricas catalizadas por metales.
Más Videos Relacionados
Videos de Conceptos Relacionados
01:26Thermal 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.
01:26Photochemical 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
Selection Rules: Photochemical Activation
01:16Cycloaddition 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.
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
01:17Pericyclic 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...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
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.