[OH:1][C:2]1[C:3]2[C:8]([CH:9]=[C:10]([O:14]C)[C:11]=1[O:12]C)=[N:7][C:6](=[O:16])[C:5](=[O:17])[N:4]=2.[B].[OH-].[Na+].Cl>C(Cl)Cl>[OH:1][C:2]1[C:3]2[C:8]([CH:9]=[C:10]([OH:14])[C:11]=1[OH:12])=[N:7][C:6](=[O:16])[C:5](=[O:17])[N:4]=2To a suspension of 5-hydroxy-6,7-dimethoxy-2,3-quinoxalinedione (48) (50 mg, 0.22 mmol) in 2 mL of methylene dichloride was added 2 mL of a solution of boron tribomide in methylene dichloride (1 M, Aldrich). The resulting mixture was stirred at room temperature for 12 hr. The mixture was poured into ice-water (5 g) to form a suspension. Aqueous sodium hydroxide (20%, 2 mL) was added to the suspension to form a red solution. Then the solution was acidified with 6 N HCl (5 mL) to pH=1. The suspension was centrifuged, washed with methanol, and dried in vacuo giving 37 mg (80%) of the product as a brown solid; mp >350° C.; 1H NMR (DMSO-d6,300 MHz) δ 6.149 (s, 1H), 9.113 (s, 1H), 9.190 (s, 2H), 10.713 (s, 1H), 11.501 (s, 1H) (HPLC >98%).
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