2(1H)-Quinoxalinone → 7-bromo-1H-quinoxalin-2-one

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Reaction Steps

Heat benzene-1,2-diamine (7.5 g, 69 mmol) and oxo-acetic acid ethyl ester (20 mL) in ethanol (100 mL) at 120° C. for 18 h. Cool, filter the resulting precipitate, and wash with dry ether to give 1H-quinoxalin-2-one (6.7 g). Dissolve 1H-quinoxalin-2-one in acetic acid (300 mL), add bromine (5 mL), and stir the reaction mixture for 1 h. Filter the resulting crystals and wash with ether to afford 7-bromo-1H-quinoxalin-2-one (7.2 g). Reflux 7-bromo-1H-quinoxalin-2-one in POCl3 (30 mL) for 18 h. Remove POCl3 in vacuo, dissolve the product in 3:1 chloroform/isopropyl alcohol, and wash the organic phase with saturated sodium bicarbonate. Dry over sodium sulfate and purify by silica gel flash chromatography eluting with dichloromethane to 10% methanol/90% dichloromethane to afford the title compound as a yellow solid (4.5 g, 58%). MS (electrospray, m/z) 243.0 and 245.0 (M+1).

Provenance & Evidence