Video Experimental Relacionado
Updated: Jul 2, 2026
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
07:12
Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Fotocatálisis eficiente con luz visible de las adiciones de ciclo [2+2] de enonas
Michael A Ischay1, Mary E Anzovino, Juana Du
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Journal of the American Chemical Society
|September 5, 2008
Resumen
El dicloruro de rutenio tris ((bipiridina) (Ru ((bipy) 3Cl2) actúa como un fotocatalizador de luz visible para las cicloadiciones de enones [2+2] eficientes. Este método utiliza la luz solar para la formación de ciclobutano de alto rendimiento con excelente diastereoselectividad.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La fotoquímica es la fotoquímica.
- La catálisis de la catálisis.
Sus antecedentes:
- La fotocatálisis de luz visible es un campo de rápido crecimiento en la química sintética.
- Las reacciones de cicloadición son fundamentales en la síntesis orgánica para la construcción de moléculas cíclicas.
- Las cicloadiciones de enonas son importantes para la formación de anillos de ciclobutanos, pero a menudo requieren condiciones duras.
Objetivo del estudio:
- Desarrollar un nuevo sistema fotocatalítico de luz visible para [2+2] enonas cicloadiciones.
- Para explorar el uso del dicloruro de rutenio tris (bipiridina) (Ru (bipy) 3Cl2) como un fotocatalizador.
- Para lograr una alta eficiencia y diastereoselectividad en la formación de productos de ciclobutano.
Principales métodos:
- Utilizando Ru(bipy) 3Cl2 como fotocatalizador bajo irradiación de luz visible.
- Empleando una variedad de enonas de arilo como sustratos.
- Investigando el mecanismo de reacción que involucra a un fotogenerado Ru(bipy) 3+ complejo e intermediarios de aniones radicales.
Principales resultados:
- Se logró una exitosa [2+2] cicloadición de enonas de arilo utilizando Ru(bipy) 3Cl2 y luz visible.
- Se observó una excelente diastereoselectividad en la formación de productos de ciclobutano.
- La reacción procedió con alta eficiencia y rendimiento, utilizando la luz solar como la única fuente de energía.
Conclusiones:
- Ru(bipy) 3Cl2 es un fotocatalizador de luz visible eficaz para las [2+2] adiciones ciclónicas de enones.
- El mecanismo propuesto implica la reducción de un solo electrón de las enonas por el fotocatalizador excitado.
- Esta metodología ofrece una ruta sostenible y eficiente a los ciclobutanos sintéticamente valiosos.
Videos de Conceptos Relacionados
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
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.
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.
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: 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.
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.
01:17Thermal 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.
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.