N[C:2]1[CH:7]=[CH:6][C:5]([N:8]2[CH2:13][CH2:12][CH:11]([C:14]([O:16]CC)=[O:15])[CH2:10][CH2:9]2)=[CH:4][CH:3]=1.N([O-])=O.[Na+].[BrH:23]>O>[Br:23][C:2]1[CH:7]=[CH:6][C:5]([N:8]2[CH2:13][CH2:12][CH:11]([C:14]([OH:16])=[O:15])[CH2:10][CH2:9]2)=[CH:4][CH:3]=1To a solution of ethyl 1-(4-aminophenyl)piperidine-4-carboxylate (2.48 g, 10 mmol) in 40 mL of HBr 40%, a solution of NaNO2 (0.69 g, 10 mmol) in 7 mL of water was slowly added at 0° C. The mixture was stirred for 15 minutes and added to a solution of CuBr (0.79 g, 5.5 mmol) in 30 mL of HBr 40%. The resulting mixture was stirred and refluxed for 2 hours. The suspension thus obtained was partitioned between 2N NaOH and ethyl acetate. The organic layer was washed with aqueous NaCl, dried over Na2SO4 and concentrated to afford crude title compound 1.56 g. MS (m/z): 286 (M+2)+
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