2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 3-ethyl-7-fluoroquinoxalin-2(1H)-one

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To a homogeneous solution of 3-ethyl-7-fluoro-3,4-dihydroquinoxalin-2(1H)-one (60.61 g, 312.1 mmol) and 1,4-dioxane (1350 ml) was added 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (75.91 g, 327.7 mmol) and the mixture was stirred using an overhead stirrer at rt for 2.5 h. At this time, the mixture was concentrated under reduced pressure to give a brown residue. The brown residue was suspended in saturated aqueous NaHCO3 (2 L), stirred for 30 min, filtered, washed with saturated aqueous NaHCO3 (1 L) to give a light green solid. The light green solid was re-suspended in saturated aqueous NaHCO3 (500 mL), well mixed, filtered, and washed with saturated aqueous NaHCO3 (500 mL) to give an off-white solid. The off-white solid was suspended in water (500 mL), well mixed, filtered, washed with water (1 L), air-dried overnight, and dried under high vacuum at 22° C. for 2 h to give 3-ethyl-7-fluoroquinoxalin-2(1H)-one (56.87 g, 94.8% yield) as an off-white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 12.36 (br. S, 1H.), 7.76 (dd, J=9.0, 5.9 Hz, 1H), 7.11 (td, J=8.8, 2.7 Hz, 1H), 7.00 (dd, J=9.6, 2.7 Hz, 1H), 2.78 (q, J=7.4 Hz, 2H), 1.20 (t, J=7.4 Hz, 3H) Mass Spectrum (ESI) m/e=193.0 (M+1).

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