Publicación: Synthesis, structure and NMR study of fluorinated isoxazoles derived from hemi-curcuminoids
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Fecha
2019-03
Autores
Cornago, María del Pilar
Cabildo, María del Pilar
Claramunt Vallespí, Rosa María
Elguero, José
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Derechos de acceso
info:eu-repo/semantics/openAccess
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Elsevier
Resumen
The purpose of this work is to prepare a series of isoxazoles bearing phenyl and 4'-hydroxy-styryl substituents at position 3 and 5; besides the phenyl group of the styryl residue bears one or two fluorine substituents. They were prepared to study their structure in the solid state and in solution by X-ray crystallography and solid-state NMR (SSNMR) for the solid state and NMR for the solution. The reaction of hydroxylamine with hemi-curcuminoid β-diketones affords two isomeric isoxazoles we have named series a (3-phenyl) and b (5-phenyl) that have been identified and characterized. Four pairs have been prepared that in three cases bear one or two fluorine atoms. Three X-ray structures have been determined 3a, 3b and 5b; 3a crystallizes without solvent, 3b crystallizes with a water molecule hydrogen-bonded to a phenolic OH, finally 5b crystallizes as a solvate with a methanol molecule hydrogen-bonded to the isoxazole N atom. This hydrogen bond results in larger differences between 15N chemical shifts in DMSO-d6 solution and in the solid state. The splitting of some signals observed in Cross-Polarization Magic Angle Spinning (CPMAS) 13C NMR was assigned to 1JCF dipolar couplings. The combined use of crystallography and SSNMR affords a complete characterization of isomeric isoxazoles, in particular the assignment of an isoxazole to a or to b series is not a trivial matter. In this work, we describe methods for the synthesis of isoxazoles bearing fluorine substituents that are promising structures for drug discovery.
Descripción
This is an Accepted Manuscript of an article published in “Journal of Fluorine Chemistry, 219, 39-49", is available online at the publisher's website: Elsevier, https://doi.org/10.1016/j.jfluchem.2018.12.012
Este es el manuscrito aceptado del artículo publicado en “Journal of Fluorine Chemistry, 219, 39-49", disponible en línea en el sitio web del editor: Elsevier, https://doi.org/10.1016/j.jfluchem.2018.12.012
Este es el manuscrito aceptado del artículo publicado en “Journal of Fluorine Chemistry, 219, 39-49", disponible en línea en el sitio web del editor: Elsevier, https://doi.org/10.1016/j.jfluchem.2018.12.012
Categorías UNESCO
Palabras clave
Isoxazole, Hemi-curcuminoids, Fluorinated isoxazoles, Solid-state NMR, X-ray crystallography
Citación
Nieto, C. I., Cornago, M. P., Cabildo, M. P., Sanz, D., Claramunt, R. M., Torralba, M. C., & Elguero, J. (2019). Synthesis, structure and NMR study of fluorinated isoxazoles derived from hemi-curcuminoids. Journal of Fluorine Chemistry, 219, 39-49. https://doi.org/10.1016/J.JFLUCHEM.2018.12.012
Centro
Facultades y escuelas::Facultad de Ciencias
Departamento
Química Orgánica y Bio-Orgánica