Video Experimental Relacionado

Updated: Jul 6, 2026

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes

Published on: August 5, 2016

Alquilaciones alilicas asimétricas cinéticas dinámicas de todos los alenos

Barry M Trost¹, Daniel R Fandrick, Diana C Dinh

¹Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA. bmtrost@stanford.edu

Journal of the American Chemical Society

|October 13, 2005

Resumen

Este estudio presenta un nuevo método para crear alenos quirales utilizando alquilaciones alílicas asimétricas dinámicas cinéticas. La reacción muestra una dependencia básica única, lo que permite el acceso a valiosos bloques de construcción quirales.

Área de la Ciencia:

Química orgánica es la química orgánica.
Catalización asimétrica por catálisis asimétrica.

Sus antecedentes:

El acceso a los alenos enantioméricamente puros es crucial para sintetizar moléculas complejas.
Los métodos anteriores para la alquilación alilica asimétrica de los alenos tienen limitaciones.

Objetivo del estudio:

Desarrollar una nueva alquilación dinámica cinética asimétrica de acetatos de aleno racémicos.
Para investigar la influencia de diferentes bases en la enantioselectividad.

Principales métodos:

Utilizó el ligando DACH-fenil Trost para la catálisis asimétrica.
Empleó nucleófilos de malonato y amina en las reacciones de alquilación.
Se realizó una cicloadición intramolecular [4 + 2] catalizada por Rh (I) de los productos.

Principales resultados:

Se logró un alto exceso enantiomérico (84-95%) para varios allenes quirales.
Descubrió una dependencia inusual de la enantioselectividad en la base para ambos tipos de nucleófilos.
Transfirió con éxito la quiralidad axial a múltiples estereocentros y controló la geometría de las olefinas.

Conclusiones:

El método desarrollado proporciona acceso general a los alenos altamente enriquecidos enantioméricamente.
La enantioselectividad dependiente de la base ofrece nuevos conocimientos sobre los mecanismos de inducción asimétrica.
La subsiguiente cicloadición demuestra la utilidad de los alenos quirales en la síntesis de moléculas complejas.

Más Videos Relacionados

Sit-to-stand-and-walk from 120% Knee Height: A Novel Approach to Assess Dynamic Postural Control Independent of Lead-limb

Sit-to-stand-and-walk from 120% Knee Height: A Novel Approach to Assess Dynamic Postural Control Independent of Lead-limb

Published on: August 30, 2016

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

A Uniaxial Compression Experiment with CO₂-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

Published on: June 12, 2019

Videos de Conceptos Relacionados

Organic Compounds

Organic Compounds

All living things are formed mostly of carbon compounds called organic compounds. The category of organic compounds includes both natural and synthetic compounds that contain carbon. Although a single, precise definition has yet to be identified by the chemistry community, most agree that a defining trait of organic molecules is the presence of carbon as the principal element, bonded to hydrogen and other carbon atoms. However, some carbon-containing compounds such as carbonates, cyanides, and...

Conformations of Ethane and Propane

Conformations of Ethane and Propane

In an organic molecule, free rotation about the carbon-carbon single bond results in energetically different conformers of the molecule. Due to this rotation, called the internal rotation, ethane has two major conformations — staggered and eclipsed.
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered ethane, the...

Acidity of 1-Alkynes

Acidity of 1-Alkynes

The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.

Acidity and Basicity of Carboxylic Acid Derivatives

Acidity and Basicity of Carboxylic Acid Derivatives

Carboxylic acids are the strongest among organic acids, as they readily lose the hydroxyl proton to form a resonance-stabilized carboxylate ion. In comparison, the acid derivatives lack acidic hydrogens directly attached to a functional group. In these compounds, the acidic nature arises from their ability to lose α hydrogens, making them weakly acidic.
The relative acidic strength of the derivatives can be explained based on the extent of resonance stabilization of the conjugate base. The...

Basicity of Aliphatic Amines

Basicity of Aliphatic Amines

Amines can behave as Brønsted–Lowry bases by accepting a proton from the acid to form corresponding conjugate acids. Due to a lone pair of nonbonding electrons, aliphatic amines can also act as Lewis bases by forming a covalent bond with an electrophile.
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...

Basicity of Aromatic Amines

Basicity of Aromatic Amines

The basicity of aromatic amines is much weaker than that of aliphatic amines due to the involvement of the lone pair of electrons over the N atom in resonance with the aryl rings. Generally, the electron-donating ability of any substituents on the aryl ring of aromatic amines increases the basicity of the amine by increasing electron density, and hence the availability of lone pair on the nitrogen. On the other hand, electron-withdrawing functional groups on the aryl ring of amines decrease the...