[CH3:1][C:2]1([CH3:16])[C:7](=[O:8])[NH:6][C:5]2[CH:9]=[C:10]([N+:13]([O-:15])=[O:14])[CH:11]=[CH:12][C:4]=2[O:3]1.Br[CH2:18][C:19]([O:21][CH2:22][CH3:23])=[O:20].C(=O)([O-])[O-].[K+].[K+].C(#N)C>CN(C)C=O>[CH3:1][C:2]1([CH3:16])[C:7](=[O:8])[N:6]([CH2:18][C:19]([O:21][CH2:22][CH3:23])=[O:20])[C:5]2[CH:9]=[C:10]([N+:13]([O-:15])=[O:14])[CH:11]=[CH:12][C:4]=2[O:3]1A mixture of 6.66 g of 3,4-dihydro-2,2-dimethyl-6-nitro-3-oxo-2H-1,4-benzoxazine, 5.51 g of ethyl bromoacetate, 4.5.6 g of potassium carbonate and 20 ml of acetonitrile was refluxed under heating for 2.5 hours. Then, 10 ml of N,N-dimethylformamide was added and the mixture was stirred at 80° C. for 2 hours. To this mixture was added 2-80 g of ethyl bromoacetate. After an hour of stirring at 80° C., 2.28 g of potassium carbonate was added and the mixture was further stirred at 80° C. for 1 hour. The reaction mixture was then concentrated under reduced pressure and the residue was chromatographed on a silica gel column, elution being carried out with hexane-ethyl acetate (10:.1). The crystals from the eluate were recrystallized from ethyl acetate-hexane to give 7.4 g of ethyl (3,4-dihydro-2,2-dimethyl-6-nitro-3-oxo-2H1,4 -benzoxazin-4-yl)acetate. This compound has the following physicochemical properties.
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