Video Experimental Relacionado
Updated: May 4, 2026
07:08
The Lambda Select cII Mutation Detection System
Published on: April 26, 2018
7.5K
Fosfinación asimétrica catalizada por el paladio. Alcance, mecanismo y origen de la enantioselectividad
Natalia F Blank1, Jillian R Moncarz, Tim J Brunker
1Contribution from the 6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA.
Journal of the American Chemical Society
|May 4, 2007
Resumen
Este estudio desarrolló un método de acoplamiento cruzado asimétrico para crear fosfinas terciarias enriquecidas con enantio utilizando catalizadores quirales de paladio. Los sustratos de fosfina estéricamente inhibidos y los yoduros de arilo ricos en electrones produjeron el mayor exceso enantiomérico, hasta el 88%.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Catalización asimétrica por catálisis asimétrica.
- Química del fósforo Química del fósforo
Sus antecedentes:
- Las fosfinas terciarias son ligandos cruciales en la catálisis.
- El desarrollo de métodos sintéticos enantioselectivos para las fosfinas es altamente deseable.
Objetivo del estudio:
- Para establecer una reacción asimétrica de acoplamiento cruzado para sintetizar fosfinas terciarias enantioenriquecidas.
- Aclarar el mecanismo catalítico y los factores que influyen en la enantioselectividad.
Principales métodos:
- Acoplamiento cruzado asimétrico de yoduros de arilo con arilfosfinas secundarias utilizando catalizadores quirales de paladio.
- Aislamiento y caracterización de intermedios catalíticos, incluido un complejo fosfido estudiado cristalográficamente.
- Espectroscopia de RMN a baja temperatura para estudiar los equilibrios diastereoméricos y la cinética de reacción.
Principales resultados:
- Se obtienen fosfinas terciarias enantioenriquecidas (hasta un 88% ee) a través del acoplamiento cruzado catalizado con paladio.
- Identificó la masa estérica de los sustituyentes de la fosfina y las propiedades electrónicas de los yoduros de arilo como factores clave para una alta enantioselectividad.
- Propuso un mecanismo catalítico que involucra la adición oxidativa, la coordinación de la fosfina, la desprotonación a un complejo fosfido y la eliminación reductora.
- Se demostró que la inversión piramidal del ligando fosfido es más rápida que la formación de enlaces P-C, consistente con un modelo cinético Curtin-Hammett-Winstein-Holness (CHWH).
Conclusiones:
- El método desarrollado proporciona un acceso eficiente a las fosfinas terciarias enriquecidas con enantio.
- El estudio proporciona conocimientos mecanicistas sobre el acoplamiento cruzado asimétrico, destacando el papel de la dinámica del ligando fosfido.
- Los hallazgos ofrecen una base para el diseño de ligandos quirales de fosfina y sistemas catalíticos mejorados.
Más Videos Relacionados
08:25Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks MOFs
Published on: January 17, 2020
6.6K
10:17Creating Highly Specific Chemically Induced Protein Dimerization Systems by Stepwise Phage Selection of a Combinatorial Single-Domain Antibody Library
Published on: January 15, 2020
7.3K
Videos de Conceptos Relacionados
01:13Induced-fit Model
77.0K
Most chemical reactions in cells require enzymes—biological catalysts that speed up the reaction without being consumed or permanently changed. They reduce the activation energy needed to convert the reactants into products. Enzymes are proteins, that usually work by binding to a substrate—a reactant molecule that they act upon.
Enzymes exhibit substrate specificity, meaning that they can only bind to certain substrates. This is mainly determined by the shape and chemical...
Enzymes exhibit substrate specificity, meaning that they can only bind to certain substrates. This is mainly determined by the shape and chemical...
77.0K
02:50Catalysis
22.9K
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
22.9K
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
14.2K
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...
14.2K
02:36Regioselectivity and Stereochemistry of Hydroboration
7.8K
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...
7.8K
01:17Pericyclic Reactions: Introduction
9.2K
Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic...
9.2K
01:22Heterogeneous Catalysis
141
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
141