Conformational preferences of furan- and thiophene-based arylamides: a combined computational and experimental study

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Conformational preferences of furan- and thiophene-based arylamides: a combined computational and experimental study

Tema

ESPECTROSCOPIA
RESONANCIA MAGNETICA NUCLEAR
FURANOS
BIBLIOGRAFIA NACIONAL QUIMICA
2013

Abstract

We examine the conformational preferences of the furan- and thiophene-based arylamides, N-methylfuran-2-carboxamide (3) and N-methylthiophene-2-carboxamide (4), using a combination of computational methods and NMR experiments. The compound choice stems from their use as foldamer building blocks. We quantify the differences in the conformational rigidity of the two compounds, which governs corresponding foldamer conformations. Specifically, we demonstrate the effects of intramolecular hydrogen bonding (H-bonding), geometrical patterns and solvent polarity on arylamide conformations by comparing 3, 4 and previously studied ortho-methoxy N-methylbenzamide (1) and ortho-methylthio N-methylbenzamide (2). The study reveals that compound 3, despite its non-optimal S(5)-type H-bond geometry, retains a large portion of the H-bonded (eclipsed) conformation even in polar protic solvents. This behaviour is consistent with the quantum mechanical (QM) torsional energy profile. The percentages of H-bonded conformers that 3 retains are just slightly smaller than those of 1, which has a stronger S(6)-type H-bond. As for 2 and 4, the replacement of the O atom in 1 by an S atom in 2 results in a 70–90% loss of the H-bonded conformer in solution. However, the equivalent O to S replacement in 3 (leading to 4) causes only 15–30% loss of the eclipsed conformers in 4. Therefore, conformational preferences of 4 are very different from 2, in contrast to the similarity between 3 and 1. This study shows how the interplay of several forces modulates the conformational flexibility of arylamides. It also attests the strategy we are developing, which leads to accurate prediction of foldamer structure. The vital component of this strategy is the re-parameterization of critical force field parameters based on QM potential energy profiles, as well as validation of these parameters using experimental data in solution.

Autor

Galan, J. F.
Tang, C. N.
Chakrabarty, S.
Liu, Z.
Pophristic, V.

Fuente

Physical Chemistry Chemical Physics v. 15, no. 28, 2013. -- p. 11883-11892

Editor

Royal Society of Chemistry

Fecha

2012

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PDF

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Inglés

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Artículo

Identificador

DOI: 10.1039/C3CP50353D

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PDF
Fecha de agregación
October 23, 2017
Colección
Bibliografía Nacional Química
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Document
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Citación
Galan, J. F., “Conformational preferences of furan- and thiophene-based arylamides: a combined computational and experimental study,” RIQUIM - Repositorio Institucional de la Facultad de Química - UdelaR, accessed January 22, 2020, http://riquim.fq.edu.uy/items/show/4697.
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