Video Experimental Relacionado
Updated: May 10, 2026
04:38
Preparation of Contiguous Bisaziridines for Regioselective Ring-Opening Reactions
Published on: July 28, 2022
Abrimiento de anillo / metástasis cruzada altamente Z-selectiva y enantioselectiva catalizada por un complejo
John Hartung1, Robert H Grubbs
1Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
Journal of the American Chemical Society
|July 5, 2013
Resumen
Los investigadores desarrollaron un nuevo catalizador de rutenio para las reacciones Z-selectivas asimétricas de apertura de anillo / metástasis cruzada. Este catalizador logra una alta selectividad Z (hasta el 98%) y enantioselectividad (hasta el 95%).
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Catalización asimétrica por catálisis asimétrica.
- Síntesis orgánica La síntesis orgánica.
Sus antecedentes:
- La apertura asimétrica del anillo/metátesis cruzada es una transformación crucial en la síntesis orgánica.
- El desarrollo de catalizadores altamente selectivos y enantioselectivos sigue siendo un desafío importante.
- Los catalizadores basados en rutenio son ampliamente explorados para las reacciones de metástasis de olefinas.
Objetivo del estudio:
- Para sintetizar un nuevo complejo de rutenio para la apertura asimétrica de anillos/metátesis cruzada.
- Para lograr una alta Z-selectividad y enantioselectividad en el proceso catalítico.
- Para demostrar un nuevo método para la preparación de catalizadores a través de la resolución quiral.
Principales métodos:
- Síntesis de un complejo de rutenio con un ligando de carbenos N-heterocíclicos quelantes.
- Resolución del complejo de carbenos N-heterocíclicos utilizando un carboxilato quiral.
- Aplicación del complejo de rutenio sintetizado en reacciones asimétricas de apertura de anillo / metástasis cruzada.
Principales resultados:
- El complejo de rutenio sintetizado cataliza efectivamente la apertura de anillos asimétricos Z-selectivos / metástasis cruzada.
- Se logró hasta un 98% de selectividad Z en las reacciones.
- Se ha demostrado una alta enantioselectividad, alcanzando hasta un 95% de exceso enantiomérico (ee).
Conclusiones:
- Se ha sintetizado con éxito un nuevo catalizador de rutenio que permite la apertura de anillos asimétricos / metástasis cruzada altamente selectiva por Z y enantioselectiva.
- La sustitución de ligandos por un carboxilato quiral es una estrategia eficaz para resolver los complejos de carbenos N-heterocíclicos quelatantes.
- Este catalizador representa un avance significativo en la metátesis asimétrica de las olefinas.
![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)
Videos de Conceptos Relacionados
02:26Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
02:24Acid-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...
02:23SN2 Reaction: Stereochemistry
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
02:43E1 Reaction: Stereochemistry and Regiochemistry
One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.
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.