[I:1][C:2]1[C:11]2[O:10][CH2:9][C:8](=[O:12])[NH:7][C:6]=2[CH:5]=[C:4]([C:13]([O:15][CH3:16])=[O:14])[CH:3]=1.C(=O)([O-])[O-].[K+].[K+].Br[CH2:24][CH2:25][CH2:26][CH3:27]>CS(C)=O.O>[CH2:24]([N:7]1[C:6]2[CH:5]=[C:4]([C:13]([O:15][CH3:16])=[O:14])[CH:3]=[C:2]([I:1])[C:11]=2[O:10][CH2:9][C:8]1=[O:12])[CH2:25][CH2:26][CH3:27]To a solution of Methyl 8-iodo-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-6-carboxylate (2.64 g) and potassium carbonate (5 g) in DMSO (20 mL) was added bromobutane (5 g), and the reaction mixture was stirred for 1 h at 80° C. The mixture was cooled to room temperature, diluted with 1:1 ethyl acetate/hexanes (100 mL) and water (160 mL), and separated. The organic layer was washed with water, and brine, dried (magnesium sulfate), filtered, and concentrated under reduced pressure. Purification by flash column chromatography (silica, 1:10 ethyl acetate/hexanes) afforded 2.24 g of the title compound: 1H NMR (300 MHz, CDCl3) δ 8.13, 7.63, 4.74, 3.96, 3.92, 1.64, 1.42, 0.97.
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