C[O:2][C:3]1[C:12]([O:13]C)=[CH:11][C:10]2[C:5](=[N:6][C:7](=[O:16])[C:8](=[O:15])[N:9]=2)[CH:4]=1.B(Br)(Br)Br.[OH-].[Na+].Cl>C(Cl)Cl>[OH:2][C:3]1[C:12]([OH:13])=[CH:11][C:10]2[C:5](=[N:6][C:7](=[O:16])[C:8](=[O:15])[N:9]=2)[CH:4]=1To a suspension of 6,7-dimethoxy-2,3-quinoxalinedione (45) (222 mg, 1.0 mmol) in 2 mL of methylene dichloride was added 5 mL of a solution of boron tribromide in methylene dichloride (1 M, Aldrich). The resulting mixture was stirred at room temperature for 24 hr. The mixture was then poured into ice-water (10 g) to form a suspension. Aquous sodium hydroxide (20%, 10 mL) was added to the suspension to form a red solution. The solution was acidified with 6 N HCl (10 mL) to pH=1. The suspension was centrifuged, washed with methanol, and dried in vacuo, giving 170 mg (88%) of the product as a brown solid; mp>350° C.; 1H NMR (DMSO-d6, 300 MHz) δ 6.541 (s, 2 H), 8.989 (s, 2 H), 11.543 (s, 2 H). EIMS m/e 194 (100, M+). (HPLC>99%).
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