2- Amino-3,4-dihydroquinoxaline

It is stated [45] that 2-amino-3,4-dihydroquinoxaline is quite easily dehydrogenated to 2-aminoquinoxaline with the help of H202 in the presence of trace amounts of iron ions ... 

Dehydrogenation of 2-amino-3,4-dihydroquinoxaline to 2-aminoquinoxaline is effected smoothly by reaction with hydrogen peroxide in combination with a trace amount of ferrous chloride, ferric sulfate, or lead dioxide as carrier. Details are... 

An unexpected property of 2-amino-3,4-dihydroquinoxaline is its ability to form a molecular complex with 2-aminoquinoxaline. Reaction of... 

Recent examples of this synthesis are of two types. The first involves condensation of the activated phenol, 2-amino-4,6-dinitrophenol (346a) with 2-dimethyl-amino-3,3-dimethyl-3//-azirine (346b) (in MeCN, 0°C- 20°C, A, 24 h) to afford a separable mixture of four products, one of which was 2-dimethylamino-3,3-dimethyl-5,7-dinitro-3,4-dihydroquinoxaline (346c) ( 20% yield) and another its hydrolysis product, 3,3-dimethyl-5,7-dinitro-3,4-dihydro-2(l//)-quinoxalinone (346d) ( 8%) the mechanism of such condensations has been discussed. ... 

The product of reaction between 2,3-diphenylquinoxaline and potassium amide has now been assigned as 2-phenylbenzimidazole,133 rather than 2,2-diphenyl-3-amino-l,2-dihydroquinoxaline, as suggested earlier. 

Reaction of 1,2,4-triazol-4-ylamidines (473) with diethyl carbonate in the presence of sodium ethoxyethoxide led (70JPR669) to intermediate 474 which, upon cyclization, gave the l,2,4-triazolo[3,4-/]l,2,4-triazino-8-ones (475). Kurasawa and his group (85JHC1715) reported that the reaction of 3-(a-hydroxyimino-4-amino-5-methyl-4//-l,2,4-triazol-3-ylmethyl)2-oxo-l,2-dihydroquinoxaline (476) with orthoesters and iron powder in acetic acid gave l,2,4-triazolo[3,4-/]l,2,4-triazines 480 and its 7,8-dihydro isomers 479. 

N-(Phenyl-l-amino-4-arsinic acid)-glycine-amide, (HO)20As. C8Hj(NHg).NH.CH2.CO.NH2, is obtained when 3 4-diaminophenyl-arsinie acid in alkaline solution is treated with chloracetamide. It begins to darken at 215° C. and melts with decomposition at 234° to 241° C. If about 25 per cent, more alkali is used in the preparation, 3-amino-6-arsino-l 2-dihydroquinoxaline results ... 

This melts at 226° C., forms an ammonium salt, decomposing at 200° C., and a benzoyl derivative, M.pt. 284° C. In the preparation of the glycine-amide, longer heating, or recrystallisation from an excess of alkali, causes it to change to the quinoxaline. If the latter in sodium hydroxide solution is allowed to stand for several days at 30° C. with an excess of ethylene oxide, the mixture being occasionally shaken, S-hydroiryethyl-amino-6-arsino-l i-dihydroquinoxaline is fomred. 

Irradiation of the diazepine N-oxide 8 gives a mixture of the 1,2-dihydroquinoxaline (10) and the oxadiazocine 11 through an intermediate oxaziridine (9). The dihydroquinoxaline undergoes acid hydrolysis to the quinoxalinone 12. It was subsequently shown that quinoxalinones of type 12 undergo ready reaction with ammonia or primary or secondary amines, in the presence of titanium tetrachloride, to give 3-amino- or... 

H. Mofakham, Z. Hezarkhani, A. Shaabani, J. Mol. Cat. 2012, 360, 26-34. CeUulose-SOjH as a biodegradable solid acid catalyzed one-pot three-component Ugi reaction synthesis of a-amino amide, 3,4-dihydroquinoxalin-2-amine, 4H-benzo [f>][l,4]thiazin-2-amine and l,6-dihydropyrazine-2,3-dicarbo-nitrile derivatives. 

In the case of 3-chloro-3-phenylpyruvamides 227, reaction with 1,2-DAB 155a involves the a-chloro ketone fragment, giving rise to 1,4-dihydroquinoxalines 228. These are due to the relatively easy alkylation of the amino group, unlike the transamidation of the amide group (Scheme 2.23) (Mamedov et al. 1989). 

---