Video Experimental Relacionado
Updated: Apr 21, 2026
07:06
A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
Published on: February 16, 2020
8.7K
Las bases fuertes. bases fuertes. Ortho-meta'- y meta-meta'-dimetalaciones dirigidas: un enfoque basado en la
Antonio J Martínez-Martínez1, Alan R Kennedy1, Robert E Mulvey2
1WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, UK.
Science (New York, N.Y.)
|November 15, 2014
Resumen
Los investigadores desarrollaron un nuevo protocolo para la desprotonación de areno utilizando un agente metalizante único. Este método logra regioselectividad en sitios distantes, desafiando la regla tradicional de la orto-metalización.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Química organometálica Química orgánica de los metales.
Sus antecedentes:
- La desprotonación de sustratos de areno ocurre típicamente en la posición orto con respecto a un grupo de dirección.
- La regioselectividad suele estar dictada por las propiedades electrónicas y coordinativas del grupo directivo.
Objetivo del estudio:
- Introducir un nuevo protocolo para la desprotonación regioselectiva del areno.
- Para extender la regioselectividad más allá de la posición ortopédica típica utilizando un agente metalizante a medida.
Principales métodos:
- Utilizó una alquil-amida de monomagnesio disódico como agente metalizante.
- Investigó la formación de un efecto de plantilla por el agente metalizante.
- Intermedios organometálicos caracterizados y productos de enfriamiento electrófilo.
Principales resultados:
- Se logró la regioselectividad en sitios arenes más distantes.
- Se observó orto-meta' y meta-meta' dimetalación dependiendo del grupo directivo.
- Se demostró meta-meta' dimetalación, rompiendo el dogma de la orto-metalación.
Conclusiones:
- El protocolo desarrollado permite una regioselectividad sin precedentes en la areneometalización.
- Los hallazgos amplían el alcance de las reacciones de metalización dirigidas.
- Este trabajo ofrece nuevas estrategias sintéticas para compuestos aromáticos complejos.
Videos de Conceptos Relacionados
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
8.0K
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...
8.0K
01:24ortho–para-Directing Deactivators: Halogens
7.2K
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...
7.2K
01:13meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
7.2K
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...
7.2K
01:14Directing Effect of Substituents: ortho–para-Directing Groups
10.0K
Ortho–para directors are substituent groups attached to the benzene ring and direct the addition of an electrophile to the positions ortho or para to the substituent. All electron-donating groups are considered ortho–para directors. They donate electrons to the ring and make the ring more electron-rich. The ring is therefore susceptible to the addition of electrophiles. Substituents such as amino, hydroxy, or alkoxy, containing lone pairs on the atom adjacent to the ring, donate...
10.0K
01:09Directing Effect of Substituents: meta-Directing Groups
6.6K
Substituents on the benzene ring that direct an incoming electrophile to undergo substitution at the meta position are called meta directors. All meta directors either have a positive charge on the atom directly bonded to the ring or a partial positive charge. These groups function by withdrawing electrons from the ring through inductive and resonance effects. Consider the carbocation intermediates formed upon the addition of an electrophile on nitrobenzene at the...
6.6K
01:15Enolate Mechanism Conventions
3.2K
When a carbonyl compound is treated with a strong base, the α position gets deprotonated to give a resonance-stabilized intermediate called an enolate. Enolates are ambident nucleophiles because they possess two nucleophilic sites that can attack an electrophile owing to the delocalization of the negative charge between the α carbon and oxygen atoms. When the oxygen atom attacks an electrophile, it is called O-attack, whereas electrophilic attack via the α carbon is known as...
3.2K