1.3- Dimethyl-2 -quinoxalinone 4-oxide

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... 

Dimethyl-1,4-benzoquinone (328) and ethylenediamine (329) gave 7,8-dimethyl-6(4//)-quinoxalinone (330) (EtOH-CH2Cl2, 20°C, light exclusion 35% the required oxidation was probably provided by an excess of the quinone). ... 

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... 

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... 

Methoxy-2,3-dimethylquinoxaline 1,4-dioxide 5-Methoxy-2,3-dimethylquinoxaline 1 -oxide 3-Methoxy-6,7-dimethyl-2(177)-quinoxalinone... 

Direct amination of quinoxalinones with hydroxylamine-O-sulfonic acid produces the 1-amino derivatives (135) in 70-80% yield, and subsequent oxidation with lead tetraacetate gives the 1,2,4-benzotriazines (138). Benzotriazine formation probably involves the formation of an intermediate nitrene (136), ring expansion to a benzo-triazepinone (137) and subsequent loss of carbon monoxide. The nitrene (136 R = Ph) was trapped as the sulfoximide 139 when the oxidation was carried out in the presence of dimethyl sulfoxide.147... 

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