[Cl:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[CH:8]([O:13][C:14]1[CH:19]=[CH:18][C:17]([CH3:20])=[CH:16][CH:15]=1)[C:9]([O:11][CH3:12])=[O:10].[Br:21]N1C(=O)CCC1=O.CC(N=NC(C#N)(C)C)(C#N)C>C(Cl)(Cl)(Cl)Cl>[Br:21][CH2:20][C:17]1[CH:18]=[CH:19][C:14]([O:13][CH:8]([C:3]2[CH:4]=[CH:5][CH:6]=[CH:7][C:2]=2[Cl:1])[C:9]([O:11][CH3:12])=[O:10])=[CH:15][CH:16]=1To a solution of 0.200 g (0.69 mmol) of the product of Step C dissolved in 2 mL of carbon tetrachloride was added 0.117 g (0.95 eq) of N-bromosuccinimide and ca. 10 mg (catalytic amount) of AIBN. The reaction mixture was stirred and refluxed under a nitrogen atmosphere for 30 minutes, then cooled and concentrated in vacuo. The residual oil was purified on a silica gel flash chromatography column eluted with 5% ethyl acetate/hexane to afford 0.186 g (73%) of the title compound.
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