Video Experimental Relacionado
Updated: Oct 11, 2025
06:34
Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides CHIPS
Published on: June 20, 2014
14.0K
Un ligando tautomérico permite la hidroxilación dirigida C−H con oxígeno molecular
Zhen Li1, Zhen Wang1, Nikita Chekshin1
1The Scripps Research Institute, La Jolla, CA 92037, USA.
Science (New York, N.Y.)
|November 29, 2021
Resumen
Este estudio introduce un nuevo catalizador de paladio para la hidroxilación eficiente de arilo C-H utilizando oxígeno. El catalizador permite la modificación selectiva de moléculas complejas en posiciones difíciles, avanzando la química sintética.
Área de la Ciencia:
- Química orgánica
- Catálisis
- Metodología sintética
Sus antecedentes:
- La hidroxilación de enlaces arilo carbono-hidrógeno (C-H) utilizando oxígeno como oxidante es sintéticamente valiosa pero desafiante.
- El desarrollo de catalizadores eficientes y selectivos para la funcionalización directa de C-H sigue siendo un objetivo clave en la síntesis orgánica.
Objetivo del estudio:
- Desarrollar un nuevo catalizador de paladio para la hidroxilación aeróbica eficiente de enlaces arilo C-H.
- Investigar el mecanismo de la hidroxilación catalítica, centrándose en el papel de la tautomerización del ligando.
Principales métodos:
- Síntesis de un complejo de paladio con un ligando de piridina/piridona bidentado.
- Prueba catalítica del complejo de paladio para la hidroxilación aeróbica de C-H.
- Utilizando espectroscopia infrarroja (IR), cristalografía de rayos X y análisis computacional para dilucidar el mecanismo de reacción.
Principales resultados:
- El complejo de paladio cataliza eficientemente la hidroxilación de enlaces arilo C-H adyacentes a los ácidos carboxílicos.
- La evidencia sugiere que la tautomerización del ligando (de monoaniónico a neutro) juega un papel en el ciclo catalítico.
- El catalizador anula la selectividad de sitio convencional, permitiendo la funcionalización en posiciones previamente inaccesibles.
Conclusiones:
- Un nuevo catalizador de paladio facilita la hidroxilación aeróbica de C-H con una selectividad de sitio única.
- Se propone la tautomerización de ligandos como una característica mecanicista clave.
- Esta metodología permite la modificación en etapa tardía de moléculas complejas, incluidas las de interés farmacéutico.
Más Videos Relacionados
Videos de Conceptos Relacionados
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
11.1K
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
11.1K
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
03:08Hydroboration-Oxidation of Alkenes
9.3K
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
9.3K
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
6.3K
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
6.3K
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
3.5K
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
3.5K
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
4.1K
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
4.1K