Using a Dialdehyde Glyoxal or Related Synthon

Commercial 40% aqueous glyoxal or the glyoxal-sodium bisulhte adduct may be used satisfactorily with o-phenylenediamines to afford 2,3-unsubstituted quinoxalines the use of an irregular synthon or substrate is also illustrated in the following examples. 

6-Dibromo-l,2-benzenediamine (95) and glyoxal (96) gave 5,8-dibromoqui-noxaline (97) (H20-Et0H, reflux, 3 h 71%) ° appropriate substrates also gave 5-chloro-6-nitro- (98) (likewise, 1 h 96%), 6-fluro-7-nitro- (99) (likewise, 1 h 81%), and 6-nitroquinoxaline (100) (MeCN-H20, 50°C, 12 h 62%). °  

With Glyoxal-Sodium Bisulfite Adduct as Synthon 

4-Methyl-5-nitro-1,2-benzenediamine gave 6-methyl-7-nitroquinoxalme (103) 

4-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%). ° 

4-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-2NaHS03H20, 70°C, 2 h 96%).282 

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, N2, 2 h 79%).620 

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