The synthesis of some polycyclic N-H acids with quinoxaline and[1,2,4]triazines

Abstract

3-(4-Aminophenyl)-1,2-dihydro-quinoxaline-2-one (2b), 3-(2-aminophenyl)-6, 7-dimethyl-1,2-dihydro-quinoxaline-2-one (1b), its 3-(4-aminophenyl)-isomer (3b), 3-(2-aminobenzyl)-1,2-dihydro-quinoxaline-2-one (4b), its 3-(4-aminobenzyl)-isomer (6b), 3-(2-aminobenzyl)-6,7-dimethyl-1,2-dihydro- quinoxaline-2-one (5b) and its 3-(4-aminobenzyl)-isomer (7b) were diazotised and the resulting diazonium salts were coupled with ethyl cyanoacetylcarbamate, 3-methyl-1,2-dihydro-quinoxaline-2-one, 3,6,7-trimethyl-1,2-dihydro-quinoxaline- 2-one and 3-methyl-6,7-dichloro-1,2-dihydro-quinoxaline-2-one. In this manner the corresponding hydrazones with one 1,2-dihydro-quinoxaline-2-one ring (1d, 3d, 5d, 7d) and hydrazones with two 1,2-dihydro-quinoxaline-2-one rings (3e-3g, 4e-4g, 5e-5g, 6e-6g, 7e-7g) were obtained. Cyclization of hydrazones (1d, 3d, 5d, 7d) afforded compounds (1h, 3h, 5h, 7h) containing 6-azauracil and also 1,2-dihydroquinoxaline-2-one rings. The starting amino derivative (1b) was prepared by the reaction of N-acetylisatine with 4,5-dimethyl-o-phenylenediamine followed by hydrolysis of the N-acetyl derivative. The amino derivative (5b) was prepared by the condensation of 2-nitrophenylpyruvic acid with 4,5-dimethyl-o-phenylenediamine and by reduction of the formed nitro derivative (5a). The amino derivative (3b) was prepared by the condensation of 4-acetylaminophenylglyoxylic acid with 4,5-dimethyl-o-phenylenediamine and hydrolysis of the N-acetyl derivative. The amino derivative (7b) resulted from the condensation of 4,5-dimethyl-o-phenylenediamine with 4-aminophenylpyruvic acid.