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Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations

Abstract

The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF{sub 3}COOH/CH{sub 2}Cl{sub 2} yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH{sub 3} groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity, in the latter. (author)
Authors:
Gomez, Javier A.G.; Lage, Mateus R.; Carneiro, Jose Walkimar de M.; Resende, Jackson A.L.C.; Vargas, Maria D., E-mail: mdvargas@vm.uff.br, E-mail: walk@vm.uff.br [1] 
  1. Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Quimica
Publication Date:
Feb 15, 2013
Product Type:
Journal Article
Resource Relation:
Journal Name: Journal of the Brazilian Chemical Society; Journal Volume: 24; Journal Issue: 2
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BENZENE; CARBON 13; CHEMICAL SHIFT; CRYSTALLOGRAPHY; ENOLS; ETHANOL; HEXANE; HYDROGEN 1; HYDROGENATION; HYDROLYSIS; INFRARED SPECTRA; ISOMERIZATION; LIQUID COLUMN CHROMATOGRAPHY; NAPHTHALENE; NMR SPECTRA; PHENAZINE; QUINONES; X-RAY DIFFRACTION
OSTI ID:
22139044
Country of Origin:
Brazil
Language:
English
Other Identifying Numbers:
Journal ID: ISSN 0103-5053; CODEN: JOCSET; TRN: BR13V0215093154
Availability:
Available from http://www.scielo.br/pdf/jbchs/v24n2/v24n2a07.pdf
Submitting Site:
BRN
Size:
page(s) 219-229
Announcement Date:
Oct 17, 2013

Citation Formats

Gomez, Javier A.G., Lage, Mateus R., Carneiro, Jose Walkimar de M., Resende, Jackson A.L.C., and Vargas, Maria D., E-mail: mdvargas@vm.uff.br, E-mail: walk@vm.uff.br. Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations. Brazil: N. p., 2013. Web. doi:10.1590/S0103-50532013000200007.
Gomez, Javier A.G., Lage, Mateus R., Carneiro, Jose Walkimar de M., Resende, Jackson A.L.C., & Vargas, Maria D., E-mail: mdvargas@vm.uff.br, E-mail: walk@vm.uff.br. Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations. Brazil. doi:10.1590/S0103-50532013000200007.
Gomez, Javier A.G., Lage, Mateus R., Carneiro, Jose Walkimar de M., Resende, Jackson A.L.C., and Vargas, Maria D., E-mail: mdvargas@vm.uff.br, E-mail: walk@vm.uff.br. 2013. "Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations." Brazil. doi:10.1590/S0103-50532013000200007. https://www.osti.gov/servlets/purl/10.1590/S0103-50532013000200007.
@misc{etde_22139044,
title = {Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations}
author = {Gomez, Javier A.G., Lage, Mateus R., Carneiro, Jose Walkimar de M., Resende, Jackson A.L.C., and Vargas, Maria D., E-mail: mdvargas@vm.uff.br, E-mail: walk@vm.uff.br}
abstractNote = {The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF{sub 3}COOH/CH{sub 2}Cl{sub 2} yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH{sub 3} groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity, in the latter. (author)}
doi = {10.1590/S0103-50532013000200007}
journal = {Journal of the Brazilian Chemical Society}
issue = {2}
volume = {24}
journal type = {AC}
place = {Brazil}
year = {2013}
month = {Feb}
}