The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Synthesis and study of N-oxides of heterocyclic compounds. I. N-Oxides of derivatives of morphine, tetra-hydroisoquinoline, and quinoline》. Authors are Khaletskii, A. M.; Pesin, V. G.; Tsin, Chshou.The article about the compound:8-Hydroxyquinoline 1-oxidecas:1127-45-3,SMILESS:OC1=CC=CC2=CC=C[N+]([O-])=C12).Product Details of 1127-45-3. Through the article, more information about this compound (cas:1127-45-3) is conveyed.
cf. Ochiai, C.A. 48, 3359i. Heating 8.4 g. codeine with 45 ml. 3% H2O2 at 50-60° gave after evaporation 8 g. codeine N-oxide, m. 206-8° (H2O); HCl salt, m. 214-17° (EtOH). To 5 g. dihydrohydroxycodeinone-HCl was added 10 ml. 10% NaOH yielding 93% dihydrohydroxycodeinone, m. 213-16°, which with 3% H2O2 as above gave 46.2% dihydrohydroxycodeinone N-oxide, decompose 152-3°, which gives a red color with Ac2O; picrate, m. 190-2°; HCl salt, m. 167-8°. The oxide treated with SO2 in warm EtOH gave 62.5% C18H23O8NS, decompose 169-70°, which was evidently an isomer of dihydrohydroxycodeinone sulfate; with BaCl2 solution it readily gave BaSO4; hydrolysis with 10% NaOH gave the original dihydrohydroxycodeinone, m. 207-9° (sulfate, m. 138-9°). Salsolidine (3 g.) in 20 ml. Me2CO and 30 ml. H2O treated with 2.5 ml. 30% H2O2 after several days at room temperature gave 15.48% N-hydroxysalsolidine, m. 100-1° (aqueous EtOH), which reduced Fehling and Tollens reagents. Similarly, N-methylsalsolidine gave N-methylsalsolidine N-oxide picrate, m. 133-4° (aqueous EtOH); HCl salt analog, decompose 162-3°. Oxidation of salsoline with 3% H2O2 in AcOH or with BzO2H in CHCl3 either gave no reaction or failed to yield any definite products. N-Methylsalsoline with aqueous H2O2 at room temperature in 3 days gave N-methylsalsoline N-oxide, m. 183° (EtOH); HCl salt, m. 186°. Oxidation of 8-hydroxyquinoline in CHCl3 with BzO2H with cooling gave yellow 8-hydroxyquinoline N-oxide, m. 137-8° (H2O); the same formed on oxidation with 30% H2O2 in AcOH-Ac2O at 40-5° in 3 hrs., but with 30% H2O2-AcOH in 2 hrs. only the starting material was recovered. 8-Hydroxyquinoline N-oxide treated with alc. KOH and Etl at reflux gave 8-ethoxyquinoline N-oxide, isolated as picrate, m. 135-8°; the same formed on treatment of 8-ethoxyquinoline with AcOH-Ac2O-30% H2O2 at 45-50°; HCl salt, m. 158°; free oxide, m. 61-2°. Similarly 2-phenylquinoline-4-carboxylic acid and AcOH-H2O2 gave 76% N-oxide, m. 244°, and 15% benzoylanthranilic acid, m. 170-2°. Oxidation of 2-phenylquinoline-4-carboxylic acid with BzO2H in CHCl3 in 2 days gave no evident reaction, the same being true of oxidation with 25% H2O2 in EtOH-Me2CO at 50°. Reduction of 2-phenylquinoline-4-carboxylic acid N-oxide with Na hydrosulfite in aqueous EtOH gave the original 2-phenylquinoline-4-carboxylic acid, m. 205-7°.
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Reference:
Quinoxaline – Wikipedia,
Quinoxaline | C8H6N2 | ChemSpider