Video Experimental Relacionado

Updated: May 19, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Published on: June 10, 2021

Aplicaciones sintéticas y dinámicas de inversión de las 2-litio-2-arilpirrolidinas y -piperidinas de configuración

Timothy K Beng¹, Jin Sun Woo, Robert E Gawley

¹Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, USA.

Journal of the American Chemical Society

|August 14, 2012

Resumen

Los carbaniones bencílicos terciarios de los heterociclos quirales son configuralmente estables a bajas temperaturas. Estos intermediarios se someten a alquilación y acilación con alta enantiopuridad, lo que permite nuevas rutas sintéticas.

Área de la Ciencia:

Química orgánica es la química orgánica.
La estereoquímica es la estereoquímica.
Metodología sintética de la metodología sintética.

Sus antecedentes:

Los carbaniones bencílicos terciarios quirales son valiosos intermedios sintéticos.
Comprender su estabilidad de configuración es crucial para la síntesis asimétrica.
Estudios anteriores han explorado sistemas relacionados con éxito variable.

Objetivo del estudio:

Para investigar la estabilidad de configuración de las N-Boc-2-litio-2-arilpiperidinas y las N-Boc-2-litio-2-arilpirrolidinas.
Para explorar el alcance de las reacciones de alquilación y acilación utilizando estos carbaniones quirales.
Para estudiar la dinámica de la enantiomerización bajo diferentes condiciones.

Principales métodos:

Generación de N-Boc-2-litio-2-arilpiperidinas y N-Boc-2-litio-2-arilpirolidinas en éter dietílico.
Estudios de estabilidad a bajas temperaturas a -80 °C y -60 °C.
Reacciones de alquilación y acilación con varios electrófilos.
Análisis de enantiopuridad utilizando cromatografía quiral.
Estudios de RMN a temperatura variable para sondear la dinámica de la enantiomerización.

Principales resultados:

Las N-Boc-2-litio-2-arilpiperidinas tienen una configuración estable a -80 °C.
Las N-Boc-2-litio-2-arilpirrolidinas son estables en su configuración a -60 °C.
Alquilación y acilación exitosas de estos carbaniones con una pérdida mínima de enantiopuridad.
La exploración del alcance de la reacción demostró una amplia aplicabilidad.
Se estudió la dinámica de la enantiomerización en varios disolventes y con ligandos achirales.

Conclusiones:

Las N-Boc-2-litio-2-arilpiperidinas y pirrolidinas quirales son intermedios estables a bajas temperaturas.
Estos intermediarios pueden ser efectivamente funcionalizados con una alta enantioselectividad.
Los hallazgos proporcionan un método robusto para sintetizar heterociclos enantiopuros 2-sustituidos.

Más Videos Relacionados

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Published on: February 7, 2019

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Published on: January 3, 2018

Videos de Conceptos Relacionados

Thermal Electrocyclic Reactions: Stereochemistry

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

Thermal and Photochemical Electrocyclic Reactions: Overview

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.

Cycloaddition Reactions: Overview

Cycloaddition Reactions: Overview

Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

Woodward–Hoffmann Selection Rules and Microscopic Reversibility

Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...

Cycloaddition Reactions: MO Requirements for Thermal Activation

Cycloaddition Reactions: MO Requirements for Thermal Activation

Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.

Stability of Substituted Cyclohexanes

Stability of Substituted Cyclohexanes

This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...