Video Experimental Relacionado
Updated: Jul 15, 2025
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
10.4K
Variaciones en el tema de la ciclización de Bergman: electrociclizaciones de penta-, hepta- y octadiinas iónicas
Dominic A Sirianni1,2, Xinli Song2, Salmika Wairegi2
1Department of Natural Sciences, Daemen University, Amherst, New York 14226, United States.
Journal of the American Chemical Society
|September 25, 2023
Resumen
Se investigaron las extensiones iónicas de la ciclización de Bergman. El catión hepta-1,6-diino y el dicatión octa-1,7-diino muestran una ciclización de baja energía a través de una vía tripleta, formando diradicales aromáticos.
Área de la Ciencia:
- Química computacional
- Química orgánica
- Química teórica
Sus antecedentes:
- La ciclización de Bergman de hexa-3-eno-1,5-dieno a p-benceno es una reacción conocida.
- Esta reacción tiene aplicaciones potenciales como agente antitumoral debido a su baja barrera de ciclización y estabilidad diradical.
- Las extensiones iónicas de esta ciclización no se han investigado a fondo.
Objetivo del estudio:
- Para investigar teóricamente las extensiones iónicas de la ciclización de Bergman.
- Para explorar las electrociclizaciones del anión penta-1,4-diino, el catión hepta-1,6-diino y el dicatión octa-1,7-diino.
- Analizar las barreras de ciclización y la estabilidad del producto de estas especies iónicas.
Principales métodos:
- Empleó la formulación de giro y giro de la teoría de cúmulos acoplados a la ecuación de movimiento con sustituciones simples y dobles (EOM-SF-CCSD).
- Barreras de ciclización calculadas para los sistemas de diena aniónica, catiónica y catiónica.
- Se analizó la estructura electrónica y la aromaticidad de los productos diradicales resultantes.
Principales resultados:
- El anión penta-1,4-diino exhibe una alta barrera de ciclización (+66 kcal mol-1).
- El catión hepta-1,6-diino y el dicatión octa-1,7-diino muestran barreras de ciclización de baja energía a través de una vía tripleta no reportada anteriormente.
- Se observó una aromaticidad significativa en los productos diradicales triplet de las ciclizaciones catiónicas.
Conclusiones:
- Las extensiones iónicas de la ciclización de Bergman, particularmente las especies catiónicas, ofrecen vías de reacción energéticamente favorables.
- La vía de triplet para la ciclización de hepta-1,6-diino y octa-1,7-diino es un hallazgo clave.
- Los diradicales triplet aromáticos resultantes requieren una mayor investigación para posibles aplicaciones.
Videos de Conceptos Relacionados
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.4K
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.
2.4K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.0K
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.
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.
2.0K
01:17Pericyclic Reactions: Introduction
8.4K
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...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic...
8.4K
![[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
10.3K
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.
10.3K
01:18Aromatic Hydrocarbon Cations: Structural Overview
2.8K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
2.8K
01:16Cycloaddition Reactions: Overview
2.6K
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.
2.6K