Video Experimental Relacionado
Updated: Jan 9, 2026
07:50
Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides
Published on: May 26, 2019
9.7K
Síntesis directa de haluros de Z-alquenilo mediante metástasis cruzada catalítica
Ming Joo Koh1, Thach T Nguyen1, Hanmo Zhang1
1Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Nature
|March 25, 2016
Resumen
Los investigadores desarrollaron un nuevo catalizador basado en molibdeno para la metátesis de olefinas, produciendo eficientemente haluros de Z-alquenilo. Este avance ofrece un método versátil para sintetizar moléculas orgánicas complejas y permitir la fluoración selectiva.
Área de la Ciencia:
- Química orgánica
- Catálisis
- Química organometálica
Sus antecedentes:
- La metátesis de olefinas es una herramienta sintética poderosa, pero la generación de haluros de alquenilo acíclicos sigue siendo un desafío.
- Los catalizadores existentes basados en rutenio para esta transformación a menudo sufren de inestabilidad, baja actividad y mala estereoselectividad.
Objetivo del estudio:
- Desarrollar métodos eficientes y selectivos para la síntesis de haluros acíclicos de Z-alquenilo.
- Explorar la reactividad de las nuevas especies de alquileno de molibdeno sustituido por halo en la metátesis de olefinas.
Principales métodos:
- Generación in situ de un nuevo catalizador de alquileno de molibdeno sustituido por halo.
- Reacción con reactivos de 1,2-dihaloeteno disponibles en el mercado en condiciones suaves (temperatura ambiente, 4 horas).
- Utilizando reactivos líquidos no purificados para la simplicidad y facilidad de manejo.
Principales resultados:
- Se ha demostrado una reactividad excepcionalmente alta del catalizador de molibdeno.
- Se obtienen altos rendimientos (hasta el 91%) y una completa selectividad Z para haluros de alquenilo 1,2-disubstituidos acíclicos (cloruros, bromuros y fluoruros).
- Síntesis exitosa de compuestos biológicamente activos y fluoración selectiva del sitio de moléculas complejas.
Conclusiones:
- Las especies de alquileno de molibdeno sustituido por halo representan una clase de catalizadores altamente eficaces para la metátesis de olefinas.
- Este método proporciona una ruta robusta, eficiente y estereoselectiva para los valiosos bloques de construcción de haluro de alquenilo.
- La metodología desarrollada tiene implicaciones significativas para la síntesis de moléculas orgánicas complejas y compuestos fluorados avanzados.
Más Videos Relacionados
Videos de Conceptos Relacionados
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
8.9K
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
8.9K
02:35Electrophilic Addition to Alkynes: Hydrohalogenation
11.3K
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
11.3K
02:34Preparation of Alkynes: Dehydrohalogenation
17.9K
Introduction
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
17.9K
02:27Preparation of Alkynes: Alkylation Reaction
11.9K
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
11.9K
02:46Halogenation of Alkenes
18.3K
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
18.3K
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
4.7K
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...
4.7K