C(=O)([O-])[O-].[Cs+].[Cs+].[Br:7][C:8]1[CH:9]=[N:10][NH:11][CH:12]=1.CS(O[CH:18]1[CH2:23][CH2:22][CH:21]([C:24]([O:26][CH2:27][CH3:28])=[O:25])[CH2:20][CH2:19]1)(=O)=O>CN(C=O)C.O>[Br:7][C:8]1[CH:9]=[N:10][N:11]([CH:18]2[CH2:23][CH2:22][CH:21]([C:24]([O:26][CH2:27][CH3:28])=[O:25])[CH2:20][CH2:19]2)[CH:12]=1Cesium carbonate (1.96 g, 6 mmol) and 4-bromopyrazole (321 mg, 2.2 mmol) were added to a solution of ethyl 4-[(methylsulfonyl)oxy]cyclohexanecarboxylate (0.50 g, 2 mmol) in DMF (10 mL). The mixture was stirred at 80° C. for 16 hours. Upon cooling to room temperature, the mixture was diluted with water and extracted with ethyl acetate. The organic layer was dried over sodium sulfate, filtered, and concentrated under reduced pressure. The residue was purified by chromatography on silica gel (ethyl acetate/petroleum ether) to give ethyl 4-(4-bromo-1H-pyrazol-1-yl)cyclohexanecarboxylate. MS ESI calc'd. for C12H18BrN2O2 [M+H]+ 301 and 303. found 301 and 303. 1H NMR (400 MHz, CDCl3): δ 7.45 (s, 1H), 7.44 (s, 1H), 4.23 (q, J=7.2 Hz, 2H), 2.46-2.38 (m, 1H), 2.26-2.18 (m, 4H), 2.06-1.98 (m, 2H), 1.86-1.78 (m, 3H), 1.36 (t, J=7.2 Hz, 3H).
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