Acetic Acid → Pyrazino[2,3-alpha]phenazine-11-carboxylic acid

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Reaction Steps

A solution of 3-nitro-(quinoxalinylamino)benzoic acid (0.8 g, 2.58 mmol) in 5M NaOH (40 mL) was treated with NaBH4 (0.9 g, 12.9 mmol), and the mixture was heated under reflux for 2 h. The cooled mixture was diluted with water (40 mL), then neutralized with glacial AcOH to give pyrazino[2,3-α]phenazine-11-carboxylic acid (0.52 g, 73%): mp (MeOH/Et3N/AcOH)>350° C. 1H NMR [CF3CO2D] δ 8.62 (dd, J=8.8, 7.3 Hz, 1 H, H-9), 8.91 (d, J=9.8 Hz, 1 H, H-5 or H-6), 8.97 (d, J=9.8 Hz, H-5 or H-6), 9.18 (dd, J=8.8, 1.0 Hz, 1 H, H-8), 9.47 (dd, J=7.3, 1.0 Hz, 1 H, H-10), 9.57 (d, J=2.2 Hz, 1 H, H-2 or H-3), 9.65 (d, J=2.2 Hz, 1 H, H-2 or H-3),

Provenance & Evidence