Quinoxaline Explained

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. 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.[1] Substituted derivatives arise when α-ketonic acids, α-chlorketones, α-aldehyde alcohols and α-ketone alcohols are used in place of diketones. Quinoxaline and its analogues may also be formed by reduction of amino acids substituted 1,5-difluoro-2,4-dinitrobenzene (DFDNB):[2]

One study[3] used 2-iodoxybenzoic acid (IBX) as a catalyst in the reaction of benzil with 1,2-diaminobenzene:

Uses

The antitumoral properties of quinoxaline compounds have been of interest.[4] Recently, quinoxaline and its analogs have been investigated as ligands.[5]

Notes and References

  1. 2,3-Pyrazinedicarboxylic Acid" Reuben G. Jones and Keith C. McLaughlin Org. Synth. 1950, 30, 86. . This paper describes the preparation of quinoxaline as an intermediate.
  2. Solution-phase reductive cyclization of 2-quinoxalinol analogs: Systematic study of parallel synthesis . Xiang-Hong Wu . Gang Liu . Mol. Divers. . 8 . 165–174. 2004 . 10.1023/B:MODI.0000025639.89179.60 . 2. 15209169 . 28252647 . etal.
  3. 10.3998/ark.5550190.0007.g02 . Facile synthesis of quinoxaline derivatives using o-iodoxybenzoic acid (IBX) at room temperature . 2006 . Heravi . Majid M. . Arkivoc . 2006 . 16. 16–22 . free . 2027/spo.5550190.0007.g02 . free .
  4. Heterocyclic quinones.2.Quinoxaline-5,6-(and 5-8)-diones-Potential antitumoral agents . Jean Renault . Michel Baron . Patrick Mailliet . Eur. J. Med. Chem. . 16 . 6 . 545–550 . 1981. etal.
  5. Regioselective Synthesis of Asymmetrically Substituted 2-Quinoxalinol Salen Ligands . Xianghong Wu . Anne E. V. Gorden . J. Org. Chem. . 72 . 8691–8699 . 2007 . 10.1021/jo701395w . 17939720 . 23.