2- Amino-3-methylquinoxaline

Aminopyrazines and 2-aminoquinoxalines, like their pyridine analogs, react with nitrous acid under aqueous conditions to give the 2(l//)-pyrazinones and 2(l//)-quinoxalinones. 2-Aminoquinoxalines are more readily hydrolyzed than typical heterocyclic amines and 2-amino-3-methylquinoxaline, for example, undergoes hydrolysis on heating at 100 °C with dilute sodium hydroxide (59JCS1132). 

Aminoquinoxaline exists predominantly as such rather than in the tautomeric imino form. This is indicated by a comparison of the basic strength of the 2-amino compound (pKo 3.90) and those of its fixed methylated tautomers, 2-dimethylaminoquinoxaline pKa 3.72) and l-methylquinoxalin-2-oneimine (pfCn 8.70). The ultraviolet spectrum of the neutral molecule of 2-dimethylaminoquinoxaline shows the expected bathochromic shifts compared to that of 2-aminoquinoxaline these spectra differ from the ultraviolet spectrum of the neutral molecule of l-methylquinoxalin-2-oneimine (Fig. 1). The mono-cations (68) and (69) derived from 2-aminoquinoxaline and l-methylquinoxalin-2-oneimine have a similar chromophoric system and show almost identical ultraviolet absorption (Fig. 2). 

Treatment of an alkaline solution of quinoxalin-2-one or quinoxa-line-2,3-dione with an alkyl iodide or sulfate results in A-methylation. Thus methylation of 3-aminoquinoxalin-2-one (74) with methyl sulfate and alkali gives 3-amino-l-methylquinoxalin-2-one (75) and not as previously reported the isomeric 0-methyl derivative. ... 

Chloro-3-methylquinoxaline 4-oxide gave 3-chloro-2-quinoxalinecarbalde-hyde 1-oxide (172) (SeOi, PhH, reflux, h 72%) dioxane may be used as solvent for such oxidations yielding, for example, 3-amino-2-quinoxaline-carbaldehyde ethyl acetate may also be so used. 

Methylquinoxaline 4-oxide (264) selectively from 2-methylquinoxaline 1,4-dioxide (265) (ascorbic acid, H2O, 90°C, 5 h 58% homologs likewise) the natural amino acids in foods can also reduce such quinoxaline N-... 

Hydrazino-3-methylquinoxaline (247) and phenacyl cyanide gave 2-(3-amino-5-phenylpyrazol-l-yl)-3-methylquinoxaline (248) (EtOH, reflux, 4 h 60% or neat reactants, fused, 5 min >50%) analogs likewise. " ... 

Chloro-5,8-dimethoxy-3-methylquinoxaline (86) gave 2-[(4-diethylamino-l-methylbutyl)amino]-5,8-dimethoxy-3-methylquinoxaline (87) (H2NCHMeCH2 CH2CH2NEt2, K2C03, 98°C, 8 h 10%)690... 

Alkyl and arylmagnesium halides react with 2-methylquinoxaline by addition of one mole of reactant to the 3,4-bond. After hydrolysis the 2-alkyl- or 2-aryl-l,2-dihydro-3-methylquinoxalines (52) are obtained. When ethylmagnesium bromide is used a dimeric by-product (53) is also isolatedReaction of 2,3-dimethylquinoxaline with benzonitrile and lithium amide gives l-amino-l-phenyl-2-(3-methyl-2-quinoxalinyl)-ethylene (54). The mono- and dilithium salts of 2,3-dimethylquinoxaline have been generated from the quinoxaline by reaction with one or two equivalents of lithium diisopropylamide (LiNPr, respectively. These salts have been reacted with a variety of electrophilic reagents such as alkyl halides, aryl ketones, esters, and nitriles. " ... 

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