[Cl:1][C:2]1[C:3]([CH3:17])=[C:4]2[C:9](=[CH:10][C:11]=1[Cl:12])[N:8]=[C:7]([O:13][CH3:14])[C:6]([O:15][CH3:16])=[N:5]2.[Br:18]N1C(=O)CCC1=O.CC(N=NC(C#N)(C)C)(C#N)C>ClC(Cl)(Cl)C>[Br:18][CH2:17][C:3]1[C:2]([Cl:1])=[C:11]([Cl:12])[CH:10]=[C:9]2[C:4]=1[N:5]=[C:6]([O:15][CH3:16])[C:7]([O:13][CH3:14])=[N:8]2A mixture of 6,7-dichloro-2,3-dimethoxy-5-methylquinoxaline (from step (f), 22.0 g, 80.5 mmol), N-bromosuccinimide (17.2 g, 96.6 mmol) and α,α-azoisobutyronitrile (1.3 g, 8.0 mmol) was heated at reflux in 1,1,1-trichloroethane (400 ml) for 4 h under irradiation from a 500 W sunlamp. The mixture was cooled, silica gel (50 g, 60-230 m) was added, and the solvent was removed under reduced pressure. The residue was applied to the top of a silica gel chromatography column, and the product was eluted using a hexane/ethyl acetate gradient. The product was triturated with hexane to give 5-bromomethyl-6,7-dichloro-2,3-dimethoxyquinoxaline (25.3 g, 87%) as a fluffy white solid. Found: C, 37.72; H, 2.40; N, 7.40; C11H9 BrCl2N2O2 requires C,37.53; H, 2.58; N, 7.96%.
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