Dimethylformamide → 1-[[(o-Tolylamino)carbonyl]amino]-1,4-dihydro-2,3-quinoxalinedione

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To a stirred solution of N-carboxymethyl-6,7-dibromo-1,4-dihydroquinoxaline-2,3-dione (100 mg, 0.260 mmol) and m-nitroaniline (40 mg, 0.29 mmol) in dry DMF (2 mL) under N2 at 28° C., DCC (60 mg, 0.29 mmol) was added in one portion. The solution was stirred for 4 h at 28° C. The insoluble solid was filtered and washed with DMF (1 mL). The clear filtrate was then poured into water (30 mL). The precipitated solid was filtered and dried under vacuum (water aspirator) to obtain 65 mg crude product as a yellow powder. The product was purified by Soxhlet extraction in boiling ethanol (20 mL), keeping the oil bath temperature at 120° C., for 4 h. The insoluble material (in the thimble) was dried under vacuum to obtain 30 mg pure (1H NMR) N-(N'-(m-nitrophenyl)carboxamidyl)-methyl-6,7-dibromo-1,4-dihydroquinox-aline-2,3-dione as a white solid (some of the product also ends up being extracted by hot ethanol which accounts for the low yield of pure product). M.p. >300° C. (decomposes). 1H NMR: δ 4.98 (s, 1H), 7.45 (s, 1H), 7.61 (d of d seen as at, J=8.1Hz) 7.79(s, 1H), 7.86 (d, 1H, J=9 Hz), 7.91 (d, 1H, J=8.4 Hz), 8.54 (s, 1H), 10.76 (s, 1H), 12.28 (s, 1H). IR (KBr, cm4): 3444, 3289, 1707, 1686, 1672, 1602. HRMS: Calculated for C16H10Br2N4O5, 495.9018; Observed, 495.9008.

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