CS(O[CH:6]1[CH2:11][CH2:10][N:9]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:8][CH2:7]1)(=O)=O.[Br:19][C:20]1[CH:24]=[CH:23][NH:22][N:21]=1.C(=O)([O-])[O-].[Cs+].[Cs+].C(OCC)(=O)C>CN(C=O)C>[Br:19][C:20]1[CH:24]=[CH:23][N:22]([CH:6]2[CH2:11][CH2:10][N:9]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:8][CH2:7]2)[N:21]=1A mixture of tert-butyl 4-(methylsulfonyloxy)piperidine-1-carboxylate (0.837 g, 3.00 mmol), 3-bromo-1H-pyrazole (0.441 g, 3.02 mmol), and cesium carbonate (2.94 g, 9.02 mmol) in DMF (10 mL) stirred for 5 h at 100° C. The reaction mixture was cooled to room temperature and poured ethyl acetate (50 mL). The mixture was washed with water (3×10 mL), dried over anhydrous sodium sulfate, filtered, and concentrated under vacuum. The residue purified via column chromatography on silica gel (eluting with 10% dichloromethane/methanol to afford tert-butyl 4-(3-bromo-1H-pyrazol-1-yl)piperidine-1-carboxylate (0.25 g, 25%) as a white solid. MS (ESI, pos. ion) m/z 330, 332 [M+H]+.
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