Quinoxaline
Skeletal formula of quinoxaline
Quinoxaline molecule
C=black, H=white, N=blue
Quinoxaline molecule
C=black, H=white, N=blue
Names
Preferred IUPAC name
Quinoxaline[1]
Other names
Benzo[b]pyrazine, Benzopyrazine, Benzoparadiazine, 1,4-Benzodiazine, Phenopiazine, Phenpiazine, Quinazine, Chinoxalin
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.001.862
EC Number
  • 202-047-4
KEGG
UNII
  • InChI=1S/C8H6N2/c1-2-4-8-7(3-1)9-5-6-10-8/h1-6H checkY
    Key: XSCHRSMBECNVNS-UHFFFAOYSA-N checkY
  • InChI=1/C8H6N2/c1-2-4-8-7(3-1)9-5-6-10-8/h1-6H
    Key: XSCHRSMBECNVNS-UHFFFAOYAS
  • c1cccc2nccnc12
Properties
C8H6N2
Molar mass 130.150 g·mol−1
Melting point 29-32 °C
Boiling point 220 to 223 °C (428 to 433 °F; 493 to 496 K)
Acidity (pKa) 0.60[2]
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

A quinoxaline, also called a benzopyrazine, in organic chemistry, is a heterocyclic compound containing a ring complex made up of a benzene ring and a pyrazine ring. It is isomeric with other naphthyridines including quinazoline, phthalazine and cinnoline.[3] It is a colorless oil that melts just above room temperature. Although quinoxaline itself is mainly of academic interest, quinoxaline derivatives are used as dyes, pharmaceuticals (such as varenicline), and antibiotics such as olaquindox, carbadox, echinomycin, levomycin and actinoleutin.

Synthesis

They can be formed by condensing ortho-diamines with 1,2-diketones. The parent substance of the group, quinoxaline, results when glyoxal is condensed with 1,2-diaminobenzene.[4] Substituted derivatives arise when α-ketonic acids, α-chlorketones, α-aldehyde alcohols and α-ketone alcohols are used in place of diketones.[3] Quinoxaline and its analogues may also be formed by reduction of amino acids substituted 1,5-difluoro-2,4-dinitrobenzene (DFDNB):[5]

One study[6] used 2-iodoxybenzoic acid (IBX) as a catalyst in the reaction of benzil with 1,2-diaminobenzene:

Quinoxaline Synthesis
Quinoxaline Synthesis

Uses

The antitumoral properties of quinoxaline compounds have been of interest.[7] Recently, quinoxaline and its analogs have been investigated as the catalyst's ligands.[8]

References

  1. ↑ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 212. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. ↑ Brown, H.C.; et al. (1955). Baude, E.A.; Nachod, F.C. (eds.). Determination of Organic Structures by Physical Methods. New York: Academic Press.
  3. 1 2 One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Quinoxalines". Encyclopædia Britannica. Vol. 22 (11th ed.). Cambridge University Press. p. 760.
  4. ↑ 2,3-Pyrazinedicarboxylic Acid" Reuben G. Jones and Keith C. McLaughlin Org. Synth. 1950, 30, 86. doi:10.15227/orgsyn.030.0086. This paper describes the preparation of quinoxaline as an intermediate.
  5. ↑ Xiang-Hong Wu; Gang Liu; et al. (2004). "Solution-phase reductive cyclization of 2-quinoxalinol analogs: Systematic study of parallel synthesis". Mol. Divers. 8 (2): 165–174. doi:10.1023/B:MODI.0000025639.89179.60. PMID 15209169. S2CID 28252647.
  6. ↑ Heravi, Majid M. (2006). "Facile synthesis of quinoxaline derivatives using o-iodoxybenzoic acid (IBX) at room temperature". Arkivoc. 2006 (16): 16–22. doi:10.3998/ark.5550190.0007.g02. hdl:2027/spo.5550190.0007.g02.
  7. ↑ Jean Renault; Michel Baron; Patrick Mailliet; et al. (1981). "Heterocyclic quinones.2.Quinoxaline-5,6-(and 5-8)-diones-Potential antitumoral agents". Eur. J. Med. Chem. 16 (6): 545–550.
  8. ↑ Xianghong Wu; Anne E. V. Gorden (2007). "Regioselective Synthesis of Asymmetrically Substituted 2-Quinoxalinol Salen Ligands". J. Org. Chem. 72 (23): 8691–8699. doi:10.1021/jo701395w. PMID 17939720.
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