Video Experimental Relacionado
Updated: Oct 4, 2025
07:06
A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
Published on: February 16, 2020
8.3K
Control estérico remoto para la activación C-H meta selectiva no dirigida de las arenas
Boobalan Ramadoss1, Yushu Jin1, Sobi Asako1
1RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Science (New York, N.Y.)
|February 10, 2022
Resumen
Los investigadores desarrollaron una nueva estrategia de control estérico remoto para la funcionalización regional selectiva. Este método permite la activación selectiva de meta enlaces carbono-hidrógeno, expandiendo las capacidades de funcionalización C-H.
Área de la Ciencia:
- Síntesis orgánica
- Catálisis
- Química medicinal
Sus antecedentes:
- La funcionalidad regioselectiva de las arenas es crucial pero desafiante.
- Los métodos de control estérico existentes bloquean principalmente los sitios ortopédicos, no diferenciando las posiciones remotas.
- La activación selectiva de enlaces específicos carbono-hidrógeno (C-H) en arenas es un objetivo sintético clave.
Objetivo del estudio:
- Introducir una nueva estrategia para el control estérico remoto en la funcionalización de arenas.
- Para lograr la activación selectiva de enlaces meta-C-H en arenas monosubstituidas.
- Demostrar la utilidad de este enfoque en las reacciones de borilación catalizadas por iridio.
Principales métodos:
- Desarrollo de un ligando tipo techo para el blindaje estérico.
- Aplicación de la catálisis del iridio para la activación del enlace C-H.
- Borilación de varios arenos monosubstituidos, incluidas las moléculas complejas.
Principales resultados:
- El ligando en forma de techo protegió eficazmente los sitios para y orto.
- Se logró la activación selectiva de los enlaces meta-C-H en ausencia de sustitución orto o para.
- Se demostró el éxito de la borilación meta-selectiva de diversos sustratos de areno.
Conclusiones:
- La estrategia reportada permite una funcionalización meta-selectiva de C-H sin precedentes.
- El control estérico remoto ofrece una nueva y poderosa herramienta para los químicos sintéticos.
- Este enfoque amplía el alcance de la funcionalización de enlaces C-H, particularmente para moléculas complejas.
![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
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
14.8K
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
14.8K
01:13meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
6.0K
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for...
6.0K
02:36Regioselectivity and Stereochemistry of Hydroboration
8.5K
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...
8.5K
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
6.5K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
6.5K
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
9.0K
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
9.0K
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
3.6K
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
3.6K