Regiospecific Oxidative Nitration of 3,4-Dihydro-6,7-disubstituted Quinoxalin-2(1H)-ones Gives 1,4-Dihydro-5-nitro-6,7-disubstituted Quinoxaline-2,3-diones, Potent Antagonists at the NMDA/Glycine Site

Article abstract of DOI:10.1021/jo00123a020

The regiospecific oxidative nitration of 3,4-dihydro-6,7-disubstituted quinoxalin-2(1H)-ones (15a-h, 20) utilizing fuming nitric acid in TFA gave 1,4-dihydro-5-nitro-6,7-disubstituted quinoxaline-2,3-diones (6a-i), respectively, in good yields.Compounds 15a-h were prepared from commercially available 1-halo-3,4-disubstituted benzenes 12a-h in three steps.These were nitration, nucleophilic substitution of the halogen ortho to the nitro group with sodium glycinate, and finally, reduction of the nitro group and concomitant cyclization.Compound 20 was prepared from 16 by a different route involving alkylation of substituted o-nitroaniline 18.The final oxidative nitration yields a single, predictable nitro isomer and is a significant improvement over the direct nitration of 6,7-disubstituted quinoxaline-2,3-diones.