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Hydrazones from hydroxy naphthaldehydes. Part 2. Condensations with aromatic N-aminoheterocycles and elucidation of tautomeric structures

Hydrazones from hydroxy naphthaldehydes. Part 2. Condensations with aromatic N-aminoheterocycles and elucidation of tautomeric structures
Hydrazones from hydroxy naphthaldehydes. Part 2. Condensations with aromatic N-aminoheterocycles and elucidation of tautomeric structures
This paper extends previous studies on hydrazones derived from hydroxyl naphthaldehydes to aromatic N-aminoheterocycles (exemplified herein by triazole derivatives), in an attempt to freeze enamine structures either by altering the electronic properties of the non-iminic nitrogen or through steric hindrance leading to coplanar dispositions between the lone pairs. By comparing experimentally obtained results (NMR in solution and crystal data) to computationally simulated ones (via DFT calculations in the gas phase and CHCl3), the structures of the preferential conformers and tautomers can be confidently assigned. All data are consistent with enhanced stability of imine forms with respect to their enamine counterparts. DFT calculations have the ability to identify the orbital interactions responsible for electron delocalization and the energy of intramolecular hydrogen bonding. In addition, all transition structures for conformational and tautomeric equilibria are located and characterized.
imine–enamine tautomerism, conformational analysis, hydrazones, DFT calculations
0040-4020
2319-2329
Martínez, R. Fernando
25456861-d6d7-4964-ac9c-54f5a1e5c2ba
Ávalos, Martín
2d0b39c7-15a3-4f90-bdfb-8e4b6e69c64a
Babiano, Reyes
b7ffd91c-bacd-4372-ab99-fc30ac2450ae
Cintas, Pedro
29979233-8382-47a8-bde7-1faf4869308c
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
Jiménez, José L.
074cc8fd-9ea1-41fc-b8b6-551d26e5fcd3
Palacios, Juan C.
2c06e379-89b3-46b1-95c8-7f5057732f9f
Martínez, R. Fernando
25456861-d6d7-4964-ac9c-54f5a1e5c2ba
Ávalos, Martín
2d0b39c7-15a3-4f90-bdfb-8e4b6e69c64a
Babiano, Reyes
b7ffd91c-bacd-4372-ab99-fc30ac2450ae
Cintas, Pedro
29979233-8382-47a8-bde7-1faf4869308c
Light, Mark E.
cf57314e-6856-491b-a8d2-2dffc452e161
Jiménez, José L.
074cc8fd-9ea1-41fc-b8b6-551d26e5fcd3
Palacios, Juan C.
2c06e379-89b3-46b1-95c8-7f5057732f9f

Martínez, R. Fernando, Ávalos, Martín, Babiano, Reyes, Cintas, Pedro, Light, Mark E., Jiménez, José L. and Palacios, Juan C. (2014) Hydrazones from hydroxy naphthaldehydes. Part 2. Condensations with aromatic N-aminoheterocycles and elucidation of tautomeric structures. Tetrahedron, 70 (14), 2319-2329. (doi:10.1016/j.tet.2014.02.049).

Record type: Article

Abstract

This paper extends previous studies on hydrazones derived from hydroxyl naphthaldehydes to aromatic N-aminoheterocycles (exemplified herein by triazole derivatives), in an attempt to freeze enamine structures either by altering the electronic properties of the non-iminic nitrogen or through steric hindrance leading to coplanar dispositions between the lone pairs. By comparing experimentally obtained results (NMR in solution and crystal data) to computationally simulated ones (via DFT calculations in the gas phase and CHCl3), the structures of the preferential conformers and tautomers can be confidently assigned. All data are consistent with enhanced stability of imine forms with respect to their enamine counterparts. DFT calculations have the ability to identify the orbital interactions responsible for electron delocalization and the energy of intramolecular hydrogen bonding. In addition, all transition structures for conformational and tautomeric equilibria are located and characterized.

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More information

Accepted/In Press date: 19 February 2014
e-pub ahead of print date: 26 February 2014
Published date: 8 April 2014
Keywords: imine–enamine tautomerism, conformational analysis, hydrazones, DFT calculations
Organisations: Chemistry

Identifiers

Local EPrints ID: 385727
URI: http://eprints.soton.ac.uk/id/eprint/385727
ISSN: 0040-4020
PURE UUID: 24eebbf1-59cf-43b5-bac7-ac6d6da37606
ORCID for Mark E. Light: ORCID iD orcid.org/0000-0002-0585-0843

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Date deposited: 21 Jan 2016 14:21
Last modified: 18 Feb 2021 16:52

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Contributors

Author: R. Fernando Martínez
Author: Martín Ávalos
Author: Reyes Babiano
Author: Pedro Cintas
Author: Mark E. Light ORCID iD
Author: José L. Jiménez
Author: Juan C. Palacios

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