6.7- Dimethyl-3-phenyl-2 -quinoxalinone

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

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%). ... 

Only one procedure has been reported recently within this category. Thus 7-chloro-l-methyl-5-phenyl-2,3-dihydro-lH-benzodiazepin-2-one 4-oxide (437) with dimethyl acetylenedicarboxylate in methylene chloride at 20° C for 3 days gave a separable mixmre of the primary tricyclic adduct, dimethyl lO-chloro-6-oxo-llb-phenyl-5,6,7, 1 lb-tetrahydroisoxazolo[2,3-t/] [ l,4]benzodiazepine-1,2-dicarboxylate (438), and its rearrangement product, 6-chloro-4-(2-methoxalyl-2-methoxycarbonyl-l-phenylvinyl)-l-methyl-3,4-dihydro-2(lT0-quinoxalinone (439) each product afforded 6-chloro-l-methyl-2(l//)-quinoxalinone (440) on refluxing in ethanol (see also Section 1.7.13). However, the final quinoxaline (440) was best obtained in 75% yield) by simply heating the initial substrate (437) and dimethyl... 

An analogous substrate, dimethyl 10-chloro-7-methyl-6-oxo-l lb-phenyl-5,6,7,1 lb-tetrahydroisoxazolo[2,3-d][l,4]benzodiazepine-l,2-dicarboxylate (566), gave not 567 but 6-chloro-l-methyl-2(l/7)-quinoxalinone (EtOH, reflux, 30 h -40%). ... 

As in the preceding subsection, l,2-bis(benzenesulfonylimino)-4,5-dimethyl-benzene (598) and 2-phenylthiazolo[3,2-fl]quinolinium-l-olate (599) in dichloromethane at 20°C during 15 min afforded l,4-bis(benzenesulfonyl)-6,7-dimethyl-3-phenyl-3-(quinolin-2-ylthio)-3,4-dihydro-2(l//)-quinoxalinone (600) in almost quantitative yield. " ... 

Methyl-l-phenyl-2(17/)-quinoxalinone (226) and methyl methacrylate (227) gave the photoadduct, methyl l,2a-dimethyl-3-oxo-4-phenyl-2,2a,3,4-tetra-hydro-l//-azeto[l,2-fl]quinoxaline-l-carboxylate (228) as a separable mixture of two stereoisomers (CH2CI2, MeOH, hv, N2, <15 h 40% each) analogs likewise. " ... 

Methoxy-5-nitro-3-phenylquinoxaline gave only 6-methoxy-5-nitro-3-phenyl-quinoxaline 1-oxide (232) (AcOH, 30% H2O2, 80°C, 3 h 81%) 1,3-dimethyl-2(17/)-quinoxalinone 4-oxide (233) was made similarly but in only... 

Benzenesulfonyl-6,7-dimethyl-3-phenyl-2(l //)-quinoxalinone (73) rearranged into 2-benzenesulfonyloxy-6,7-dimethyl-3-phenylquinoxaline (74) (xylene, 140°C, 2 h 75%).964... 

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