Methane → 5-Chloro-7-fluoro-1,4-dihydro-2,3-quinoxalinedione

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Reaction Steps

5-Chloro-7-fluoro-1,4-dihydro-2,3-quinoxalinedione was prepared using an adaptation of the method of Cheeseman. (Cheeseman, G. W. H. J. Chem. Soc. 1171 (1962)). A mixture of diethyl oxalate (2.64 g, 18.1 mmol) and 1,2-diamino-3-chloro-5-fluorobenzene (290 mg, 1.81 mmol) was heated to reflux under N2 for 10 h. The reaction was allowed to cool to room temperature and the shiny yellow-brown crystals collected by vacuum filtration and rinsed with EtOH (10 mL) and air dried to give 164.1 mg (42%). A portion of this solid was taken and dissolved in 10 mL 1N NaOH. The solution was treated with activated charcoal and filtered through a pad of Celite. The resulting solution was carefully acidified with 1N HCl (pH=6). Pale yellow needles slowly formed in the solution and were collected by vacuum filtration, rinsed with 20 mL of H2O and further dried under vacuum (0.1 torr, 78° C.) to yield 67.8 of powdery pale yellow crystals. mp 306°-308° C. (dec), 1H NMR (d6 -DMSO) δ7.28 (s, 1H, ArH), 7.56 (s, 1H, ArH), 11.7 (br s, 2H, NH), EIMS m/z 216 (M+2,34, 214 (M+, bp), 188 (21), 186 (68), 123 (61), 131 (62). EIHRMS calc. for C8H4ClFN2O2 213.9945, found 213.9961.

Provenance & Evidence