Methyl-3-phenyl-2-quinoxalinecarboxylate

Benzenediamine (199) and C-(2-chloro-2-phenylacetyl)formamide (200) gave 3-phenyl-3,4-dihydro-2-quinoxalinecarboxamide (201), formulated as its 1,4-dihydro tautomer (EtOH, reflux, 6 h 56%) in contrast, the same substrate (199) with methyl C-(2-chloro-2-phenylacetyl)formate cyanohydrin (202) gave methyl 3-phenyl-2-quinoxalinecarboxylate (203), presumably by aerial oxidation of a dihydro precursor (MeCN, reflux, 12 h 7%). ... 

Methyl 3-phenyl-2-quinoxalinecarboxylate Methyl 3-phenyl-2-quinoxalinecarboxylate... 

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%). ... 

This category is represented in the facile reaction of o-phenylenediamine (408) with 4-benzoyl-5-phenyl-2,3-dihydro-2,3-thiophenedione (409) (in toluene at 20°C for 30 min) to afford 3-(a-benzoyl-p-mercaptostyryl)-2(l//)-qumoxalinone (410) in 98% yield " also in the complicated reaction of 3-methyl-2,2,4-trinitro-2,5-dihydrothiophene 1,1-dioxide (411) with 2 equiv of ethyl 4-aminobenzoate (412) (in acetonitrile but no further details) to give ethyl 2-(p-ethoxycarbonylphenyl)-3-(l-methyl-2-nitrovinyl)-6-quinoxalinecarboxylate (413) in 51% yield.Several... 

One interesting example of this type of synthesis has been reported. 6-Phenyl-5//-5,7(6F/)-pyrrolo[3,4-/>]pyrazine (515) underwent electrolytic reduction in the presence of chlorotrimethylsilane to give the (unisolated ) substrate (516) that reacted with methyl acrylate (minimal detail) to afford a mixture of methyl 8-anilino-5-oxo-l,5-dihydro-6-quinoxalinecarboxylate (517) and methyl 5-ani-lino-8-oxo-4,8-dihydro-6-quinoxalinecarboxylate (517a) (17% and 21%, respectively, after separation). 

Ethyl 3-isopropyl-2-quinoxalinecarboxylate Ethyl 3-methyl-2-methylene-1 -phenyl-1,2-dihydro-6-quinoxalinecarboxylate... 

Ethyl 3-oxo-4-phenyl-3,4-dihydro-2-quinoxalinecarboxylate (73, R = OEt) gave (V-methyl-3-oxo-4-phenyl-3,4-dihydro-2-quinoxalinecarboxamide (73, R = NHMe) (MeNH2, EtOH, H20, 20°C, A, 5 min 91%).535... 

Methyl 6-methyl-2,3-dioxo-1,2,3,4-tetrahydro-5-quinoxalinecarboxylate 2-Methyl-3-methylene-7-methylsulfonyl-4-phenyl-3,4-dihydroquinoxaline 2-Methyl-3-methylene-7-nitro-4-phenyl-3,4-dihydroquinoxaline... 

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