[CH3:1][CH:2]1[O:7][C:6]2[CH:8]=[C:9]([F:12])[CH:10]=[CH:11][C:5]=2[NH:4][CH2:3]1.[Br:13][CH2:14][CH2:15][CH2:16]Br.C(=O)([O-])[O-].[Na+].[Na+]>CN(C=O)C.C(OCC)(=O)C>[CH3:1][CH:2]1[O:7][C:6]2[CH:8]=[C:9]([F:12])[CH:10]=[CH:11][C:5]=2[N:4]([CH2:16][CH2:15][CH2:14][Br:13])[CH2:3]1A mixture of 2-methyl-7-fluoro-3,4-dihydro-2H-benzo[b][1,4]oxazine (4.3 g, 1 eq, 25.74 mmol) obtained in step (iii) above, 1,3-dibromo propane (26.1 ml, 10 eq, 257 mmol) and anhydrous sodium carbonate (8.2 g, 3 eq, 77.2 mmol) in dry DMF (260 ml) was heated at 70° C. for 16 h. The reaction mixture was diluted with ethyl acetate and washed with water and brine. The residue was chromatographed using ethyl acetate and hexane to afford the title compound (3.5 g, yield 48%) as viscous oil.
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