2- Methylquinoxalines acids

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). 

The structure of this compound is confirmed by the preparation of the 1-acetyl derivative, acid degradation to 4-methylquinoxalin-3-one-2-carboxylic acid (12), and alternative synthesis from the acid chloride of (12) and AW -dimethyluread A most unusual cyclization occurs when AW-dimethyl-o-phenylenediamine (15) is treated with alloxan in ethanolic solution this apparently involves an A-methyl group and leads to the formation of the spirobarbituric acid (16). The struc-... 

The bromination of 5,8-dimethoxyquinoxaline in methanol gives a mixture of 6-bromo and 6,7-dibromo compounds/ Treatment of 2-methylquinoxaline with bromine in acetic acid yields a mixture of 27% of 2 bromomethyl- and 37% of 2-dibromomethyl-quinoxaline." Thus in the absence of powerfully activating groups, side-chain rather than nuclear substitution takes place. 

Peracetic acid oxidation of l-methylquinoxalin-2-one (42) at 55°C gives l-methylquinoxaline-2,3-dione (43) in moderate yield, and similar treatment of l,3-dimethylquinoxalin-2-one (44) yields a small quantity of the 4-oxide, An improved yield of (43) is obtained by... 

Oxidation of 4-methylquinoxalin-3-one 2-carboxy-fV -methylamlide (45) with hydrogen peroxide and acetic acid furnishes the 1-oxide but, on removal of either or both of the fV-raethyl groups (giving 46, 47, or 48), oxidation with hydrogen peroxide or with peracetic or perbenzoic acid results in the removal of the carboxyamide groups and the formation of a quinoxaline-2,3-dione. ... 

Chromic acid oxidation of hydroxyiminomalon-bis-AT -methylanilide (93) gives 4-methylquinoxalin-3-one-2-carboxy-A -methylanilide 1-oxide (94) by a process involving AT -oxidation and dehydrative ring closure. ... 

The structure of the latter compound has been confirmed by alternative synthesis from 4-methylquinoxalin-3-one-2-carboxylic acid, which... 

Reaction of nitromalon-bis-A -methylanilide (105) with sulfuric acid gives A -methylisatin- -oxime (107) and not 4-methylquinoxalin-3-one 1-oxide (108) as originally suggested. This transformation may involve a Beckmann-type rearrangement of the protonated aci-nitro compound (106) prior to dehydrative ring closure. ... 

Bromomethyl-3-methylquinoxaline (273) and m-hydroxybenzoic acid (274) gave either 2-(m-hydroxybenzoyloxymethyl)-3-methylquinoxaline (275) [KOH (1 mol), EtOH, reflux, 2h 69%] or 2-(m-carboxyphenoxymethyl)-3-methylquinoxaline (276) [KOH (2 mol), EtOH, 50°C—>reflux, 1 h 44%] p-hydroxybenzoic acid reacted similarly but o-hydroxybenzoic acid (salicylic acid) gave only the isomer of product (275) even in the presence of KOH (2 mol). It would seem that the substrate (275) preferred to react at the phenolic anion rather than at the carboxylate anion when both were present... 

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-... 

Anilino-2-quinoxalinecarboxamide 3-AniIino-2-quinoxalinecarboxylic acid 3-Azido-7-benzoyl-2(l//)-quinoxalinone 2-Azido-6-bromo-3-methylquinoxaline... 

Oxidation, by nitric acid, 48 of aldehyde to carboxyl group, 49 of hydroxyl to carboxyl group, 49 of 2-methylquinoxaline to 2-methyl-pyrazine-5,6-dicarboxylic acid, 89 of quinoxaline to 2,3-pyrazinedicar-boxylic acid, 87... 

Methyl-5,6-pyrazinedicarboxylic acid may be prepared in 70-75% yields from 2-methylquinoxaline by this same procedure. The crude acid (m.p. 155-160°, dec.) is somewhat unstable at elevated temperatures. It should not be heated above 100° for long periods of time. In order to obtain pure 2-methyl-5,6-pyrazinedicarboxylic acid (m.p. 175°, dec.) the crude product is best recrystaUized from acetone. 

Quinoxaline has been prepared by the reaction of glyoxal with o-phenylenediamine, and 2-methylquinoxaline by the reaction of pyruvic aldehyde or isonitrosoacetone with < -phenylenedi-amine. 2,3-Pyrazinedicarboxylic acid has been prepared only by the permanganate oxidation of quinoxaline. 2-Methyl-5,6-pyrazinedicarboxylic acid has been prepared from 2-methyl-quinoxaline in the same way. - ... 

Hydroxyquinoxaline (98) is converted into the 1,4-dioxide (99), and 5-acetamido-7-methylquinoxaline similarly forms the 1,4-dioxide with m-chloroperbenzoic acid in benzene.195a,b 2-Aminoquinoxaline is best oxidized with permaleic acid in ethanol in the presence of sodium bicarbonate. Exclusive 1-oxidation occurs, and the product is conveniently isolated as the carbamic acid ester (100) (85%).115... 

Aminoquinoxaline-3-thione (166) reacts with cr-chloroesters under alkaline conditions, and (2-aminoquinoxaline)thioglycollic acids (167) are obtained. With et-haloketones in the presence of alkali, ring closure takes place and quinoxalino]2,3-6] [ l,4]thiazines, such as 168 are isolated.174 Photolysis of 3-methylquinoxaline-2-thione in ethanol or chloroform yields 3-methyl-2-quinoxalyl disulfide.175... 

Methylquinoxaline-2,3-dione (173) is oxidized with Co(OAc)2 Mn(OAc)2 in HBr/H20 to the 6-carboxylic acid (174),183 which on treatment with thionyl chloride is converted into 2,3-dichloro-quinoxaline-6-carbonyl chloride (175).184 The 6-sulfonyl chloride is obtained from quinoxaline-2,3-dione and chlorosulfonic acid and treatment of the resulting 6-chlorosulfonyl derivative with phosphoryl chloride and pyridine.185 Such derivatives are useful synthetic dye intermediates. 

Methylquinoxaline, 30, 88, 89 fi aws-Methylstyrylcarbinol, 30, 77 Methyl 0-thiodipropionate, 30, 65 Michael condensation between 2-nitro-propane and methyl acrylate, 32, 86 Monochlorourea, 30, 24, 25, 26 Monoethanolamine, 32, 19 Mucobromic acid, 32, 95... 

When 2,4-dimethylbenzodiazepine was treated with sodium nitrite in acetic acid, the major products were 2-methylbenzimidazole and 2-acetyl-3-methylquinoxaline the latter product could arise by initial nitrosation at C-3 to form a 3-hydroxyimino derivative that underwent rearrangement and hydrolysis (59JCS1132). Also isolated in low yield was a compound that, on spectroscopic evidence, was assigned the structure l-nitroso-2,4-dimethyl-1 //-benzodiazepine. 

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