Br[C:2]1[C:3](=O)[C:4](Br)=[CH:5][C:6]([Br:9])(Br)[CH:7]=1.[O:12]1C2C=CC=CC=2[N:14]=[C:13]1[N:21]1[CH2:26][CH2:25][CH2:24][CH2:23][C@H:22]1[C:27]([O:29][CH3:30])=[O:28]>ClCCl>[Br:9][C:6]1[CH:7]=[CH:2][C:3]2[N:14]=[C:13]([N:21]3[CH2:26][CH2:25][CH2:24][CH2:23][C@H:22]3[C:27]([O:29][CH3:30])=[O:28])[O:12][C:4]=2[CH:5]=12,4,4,6-Tetrabromo-2,5-cyclohexadien-1-one (4.7 g) was added to a solution of methyl (2S)-1-(1,3-benzoxazol-2-yl)-2-piperidinecarboxylate (3.0 g) [see Preparation 2] in dichloromethane (60 ml) at −10° C. over a period of 10 minutes. The reaction mixture was then warmed to room temperature and diluted with dichloromethane. The organic layer was washed with saturated sodium hydrogen carbonate, then with 1N sodium hydroxide solution, dried over sodium sulphate and the solvent removed under reduced pressure to afford methyl (2S)-1-(6-bromo-1,3-benzoxazol-2-yl)-2-piperidinecarboxylate (3.7 g) as a purple coloured oil.
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