Quinoxalinones

When activating substituents are present in the benzenoid ring, substitution usually becomes more facile and occurs in accordance with predictions based on simple valence bond theory. When activating substituents are present in the heterocyclic ring the situation varies depending upon reaction conditions thus, nitration of 2(177)-quinoxalinone in acetic acid yields 7-nitro-2(177)-quinoxalinone (21) whereas nitration with mixed acid yields the 6-nitro derivative (22). The difference in products probably reflects a difference in the species being nitrated neutral 2(177)-quinoxalinone in acetic acid and the diprotonated species (23) in mixed acids. [Pg.163]

Alkylation of pyrazinones and quinoxalinones may be carried out under a variety of conditions and it is usually observed that while O-alkylation may occur under conditions of kinetic control, to yield the corresponding alkoxypyrazines or alkoxyquinoxalines, under thermodynamic control the A-alkylated products are formed. Alkylation using trialkyl-oxonium fluoroborate results in exclusive O-alkylation, and silylation under a variety of conditions (75MI21400) yields specifically the O-silylated products. Alkylation with methyl iodide or dimethyl sulfate invariably leads to A-methylation. [Pg.173]

Pyrazinones and quinoxalinones both play important roles in the chemistry of pyrazines and quinoxalines respectively, in that they are usually available by direct synthesis and serve as important starting points for halo derivatives, which in turn lead to a range of substitution products (e.g. see Section 2.14.3.3). [Pg.173]

Other synthetic routes to pyrazinones and quinoxalinones are from the halo compounds, by dealkylation of ethers (8lJCS(Pl)3111> or by diazotization of the corresponding amines, but since the halo derivatives are normally derived from the hydroxy compounds, and the amines from the halo derivatives, direct synthesis seems to represent the most practical approach. [Pg.173]

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). [Pg.177]

Chloro-l-methyl-2-quinoxalinone (215), which cannot anionize, reacts readUy with iV -methylaniline. 6-Bromo-as-triazine-3,5-dione (216) is largely anionized by dimethylamine but not by thiourea... [Pg.248]

In contrast, the reaction of dimethyl acetylenedicarboxylate with the benzodiazepinone 4-oxide 21 gives the quinoxalinone 24 by way of the isolable intermediates 22 and 23.249... [Pg.416]

Bromo-A -ferf-butyl-6-(2-chloroacetamido)aniline (25) gave 5-bromo-4-tert-butyl-3,4-dihydro-2(l//)-quinoxalinone (26) (EtPrjN, Nal, MeCN, reflux, 22 h 79%). ... [Pg.5]

A,A-Dibenzyl-2-(ethoxycarbonylmethyl)amino-4-(trifluoromethyl)aniline (27) underwent reductive debenzylation and spontaneous cyclization to 6-trifluoro-methyl-3,4-dihydro-2(17/)-quinoxalinone (28) [Pd(OH)2/C, EtOH, H2 (3 atm), 3 days 97%]. " °... [Pg.5]

Ethoxycarbonylacrylamido)nitrobenzene (55) gave 3-ethoxycarbonylmethyl-3,4-dihydro-2(177)-quinoxalinone (56) [Raney Ni, H2 (3 atm), MeOH, 20°C,... [Pg.10]

Chloro-3- [(1 -ethoxycarbonyl-1 -methylethyl)amino] -4-nitrobenzene (61) gave 6-cbloro-3,3-dimetbyl-3,4-dibydro-2(lF/)-quinoxalinone (62) (TiCl3, AcONa,... [Pg.11]

Acetamido-5-methoxy-1,2-benzenediamine (prepared in situ by reduction of 1 -acetamido-2-methoxy-4,5-dinotrobenzene) gave 6-acetamido-7-methoxy-quinoxaline (104) (OHCCHO-2NaHS03 H20, 70°C, 2 h 96%). 4-Acetamido-2,3-diaminophenol (105) (prepared in situ by reduction of the 2,3-dinitro analog) gave 8-acetamido-5(l//)-quinoxalinone (106) (OHCCHO-2NaHS03-H20, reflux, Nji, 2 h 79%). °... [Pg.17]

Chloro-l,2-benzenediamine (137) and glyoxylic acid gave a mixture of 6-chloro- (138) and 7-chloro-2(l//)-quinoxalinone (139) from which only 6-isomer could be isolated in a pure state (OHCCO2H, H20-Me0H, 20°C, 24h 37%). ... [Pg.22]

Benzenediamine (148) and frani-l-chloro-l,2-bis(hydroxyimino)ethane (149) gave 2(177)-quinoxalinone oxime (150), perhaps better formulated as 2-hydroxyaminoquinoxaline (151) (EtOH, 20°C, 3 h 71%) 6,7-dibromo-l,2-benzenediamine likewise gave 6,7-dibromo-2-hydroxyamino-quinoxaline. ... [Pg.24]

Dimethyl-1,2-benzenediamine with phenylglyoxylic acid (PhCOC02H) gave 6,7-dimethyl-3-phenyl-2(17/)-quinoxalinone (212, R = Ph) (EtOH, reflux. [Pg.30]

Methyl-1,2-benzenediamine (215, R = Me) with the hydrate of 3,3,3-trifluoro-pyruvic acid gave a mixture of isomers (216, R = Me) and (217, R = Me) (dioxane, reflux, 30 min 98%) from which neither appears to have been isolated in a pure state in contrast, 4-nitro-1,2-benzenediamine (215, R = NO2) and the same synthon gave a mixture of 6-nitro- (216, R = NO2) and 7-nitro-3-trifluoromethyl-2(l//)-quinoxalinone (217, R = NO2) (dioxane, reflux, 4 h 95%), from which both isomers were isolable, albeit with... [Pg.31]

The same substrate (218) and ethyl ethoxalylacetate (Et02CC0CH2C02Et) gave 3-ethoxycarbonylmethyl-2(l//)-quinoxalinone (221, R = H) (EtOH, reflux, 3 h 80% ° likewise but 15 min 64%) the homologous substrate, 3,6-dimetyl-l,2-benzenediamine, and the same synthon gave 3-ethoxycarbonyl-methyl-5,8-dimethyl-2(l//)-quinoxalinone (221, R = Me) (AcOH, reflux, briefly 61%). ... [Pg.32]

Benzenediamine (228) and diethyl dibromomalonate (229) gave ethyl 3-oxo-3,4-dihydro-2-quinoxalinecarboxylate (230) (MeOH, 20°C, 24 h 40%)." The same substrate (228) with ethyl a-bromoisobutyrate gave 3,3-dimethyl-3,4-dihydro-2(17i)-qumoxalinone (231) (Me2NCHO, NEtPr j, 110°C, 7 h 76%) or with methyl 2-bromo-2-phenylacetate gave 3-phenyl-3,4-dihydro-2(l//)-quinoxalinone (232) (KI, K2CO2, AcMe, reflux, 12 h then oily product, MeONa, PhH, reflux, 7 h 89%). ... [Pg.33]

The corresponding half-imidic esters have also been used to afford 3-amino-2(17/)-quinoxalinones. The following examples illustrate typical conditions and yields. [Pg.36]

In contrast, 4-methyl-1,2-benzenediamine (263) and the same synthon (261) gave an inseparable 70 30 mixture of 3-amino-7-methyl- (264) and 3-amino-6-methyl-2(177)-quinoxalinone (265) [EtOH, 25°C, >8 h 77% (mixture)] likewise analogous mixtures. [Pg.38]

Benzenediamine (270) and the nitrone, ethyl 2-amino-2-(oxidophenylimino) acetate (271) (the equivalent of ethyl carbamoylformate) gave 3-amino-2(177)-quinoxalinone (272) with loss of EtOH and A -phenylhydroxylamine (EtOH, trace AcOH, 20°C, h 45%). " ... [Pg.38]

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