Reactivity of the Diazine Ring

Quinoxaline is a by-product of cooking some food and can inhibit the growth of some ciliate protozoa and plan-pathogenic fungi. The metabolism of this ring system by Pseudomonas putida can provide the quinoxaline cis-5,6-dihydrodiol, 5-hydroxyquinoxaline, and 2(l//)-quinoxalinone. When quinoxaline is metabolized by Streptomyces badius, two different products were isolated. Both of these two products, 2(l//)-quinoxalinone and 3,4-dihydro-2(l/ )-quinoxalinone, were only isolated from the treatment of Streptomyces badius with quinoxaline. Six other Streptomyces species were tested and only produced 2(l//)-quinoxalinone. The mechanism for the formation of 3,4-dihydro-2(l//)- luinoxalinone was not determined. 

Protonation of the heteroaromatic ring considerably increases the reactivity towards nucleophilic radicals (3-6 orders of magnitude) compared to the unprotonated base. The introduction of the carbonyl decreases the basicity of the heterocyclic ring, reducing the reactivity of the molecule and preventing disubstitution. 

Due to the presence of two electronegative oxygen rings, the pyrazine and quinoxaline rings are poor substrates for electrophilic aromatic substrates. These nitrogen atoms do increase the heterocycles reactivity toward nucleophilic aromatic reaction. This reaction is usually done starting 

In efforts to develop selective inhibitors of the three members of the Pirn kinase family, a high through-put screen (HTS) of functionalized 

Selective fluorination of a range of heteroaromatic compounds to provide the 2-fluoro-derivatives has been achieved using an elemental fluorine-iodine mixture. This fluorination of heteroaromatic rings has become of vital interest in academia and industry due to the effects the 

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