3-Methyl-2 -quinoxalinone 4-oxide

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... 

Fluoro-2(17/)-quinoxalinone 4-oxide (273) gave 6-fluoro-3-methyl-2(l//)-quinoxalinone (275), probably by degradation of the adduct (274) (ACCH2-COjEt, PhH, H2O, NaOH, 65°C, 1 h % several analogs likewise). ... 

Benzenesulfonyl-l-ethoxycarbonylmethyl-3,4-dihydro-2(l//)-quinoxalinone (8) gave either l-carboxymethyl-2(l//)-quinoxalinone (9) (1.25M NaOH, reflux, 6 h 92% note additional nuclear oxidation by loss of PhS02H) or 4-benzenesulfonyl-1 -carboxymethyl-3,4-dihydro-2(lfl)-quinoxalinone (10) (H2 SO4, AcOH, H2O, 80°C, 15 min then 60°C, 5 h then 20°C, 16 h 27%). Methyl 3-methyl-2-quinoxalinecarboxylate 1,4-dioxide (11, R = Me) gave 3-methyl-2-quinoxalinecarboxyhc acid 1,4-dioxide (11, R = H) (Et3N, CaCl2,... 

Ethyl-l-methyl-2(17T)-quinoxalinone 4-oxide Ethyl 3-morpholino-2-quinoxalinecarboxylate Ethyl 6-nitro-2-quinoxalinecarboxylate... 

Methyl-3-oxo-3,4-dihydro-2-quinoxalinecarbonitrile 1-oxide (149) gave 6-methyl-2(lfl)-quinoxalinone (150) (Na2S204, H20, EtOH, °C, h %).98... 

Acetoxymethylquinazoline 1,4-dioxide 2-Acetoxymethylquinazoline 4-oxide 1 -Acetoxy-6-methyl-2( l//)-quinoxalinone 3 - Acetoxy methyl-2( 1H)-quinoxalinone 1 -Acetoxy-3-methyl-2( l//)-quinoxalinone... 

Amino-3-methyl-2(l//)-quinoxalinone 3-Amino-l-methyl-2(l//)-quinoxalinone 4-oxide 3-Amino-7-nitro-2-quinoxalinecarbonitrile... 

Ethoxy carbonylmethyl-l-methyl-2(lff)-quinoxalinone 4-oxide 3-Ethoxy carbonylmethyl-6/7-nitro-2(lff)-quinoxalinone... 

Methyl-3-propyl-2( 17/)-quinoxalinone 4-oxide 2-Methyl-3-propylthioquinoxaline 2-Methyl-3-(prop-2-ynyl)quinoxaline 2-Methyl-5-quinoxalinamine... 

Quinoxaline 1-oxide (209) reacts with phenyl isocyanate to give 2-anilinoquinoxaline (210) together with 1,3-diphenyl-l-(2-quinoxalinyl)-urea (211) and cyclized oxidation product of the urea 212.215 2-Quinoxalinone 4-oxide (205) and its 1-methyl derivative undergo addition reactions, e.g., with phenyl isocyanate and benzyne to give compounds 214 and 216, respectively.216 These reactions are formulated as proceeding via the intermediate cycloadducts 213 and 215. Compound 216 has also been obtained by photolysis of 3-(o-hydroxy-phenyl)quinoxaline 1-oxide.51 1,3-Dipolar cycloaddition of quinoxaline... 

The infrared spectra of quinoxaline mono- and di-./V-oxides 3-quin-oxalinone 1-oxides, and 1-hydroxyquinoxaline 2,3-diones have been reported, and the ring stretching vibrations and C=0 and N—O stretching frequencies were assigned.267 2-Methyl-6-amino- and 2-methyl-6-nitro-l,2,3,4-tetrahydro-3-quinoxalinones have been examined... 

N-oxides of this type are accessible from o-nitroaniline-based syntheses (see earlier section). l,2-Dihydro-2-oxoquinoxaline 4-oxide (64) and its N-methyl derivative (65) condense with compoimds containing an active methylene group in the presence of piperidine, yielding 3-alkylated quinoxalinones (66). The oxide 64, when warmed with aqueous potassium cyanide, affords 3-cyano-l,2-dihydro-2-oxoquinoxaline, whereas oxide 65 gives l,2-dihydro-3-hydroxy-2-oxo-l-methylquinoxaline. ... 

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