C(=O)([O-])[O-].[K+].[K+].[CH2:7]([O:9][C:10](=[O:25])[CH:11]=[C:12]1[CH2:17][CH2:16][N:15]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:14][CH2:13]1)[CH3:8].[CH3:26][N+:27]([O-:29])=[O:28].Cl>O.CS(C)=O>[CH2:7]([O:9][C:10](=[O:25])[CH2:11][C:12]1([CH2:26][N+:27]([O-:29])=[O:28])[CH2:17][CH2:16][N:15]([C:18]([O:20][C:21]([CH3:24])([CH3:23])[CH3:22])=[O:19])[CH2:14][CH2:13]1)[CH3:8]Into a 3000-mL 4-necked round-bottom flask was placed potassium carbonate (93.2 g, 662 mmol, 0.50 equiv) and DMSO (2000 mL). The resulting solution was heated to 80° C. This was followed by the addition of tert-butyl 4-(2-ethoxy-2-oxoethylidene)piperidine-1-carboxylate (368 g, 1.30 mol, 1.00 equiv, 95%) and CH3NO2 (417 g, 6.70 mol, 5.00 equiv, 98%) slowly. The resulting solution was stirred for 120 min at 90° C. After being cooled to room temperature, the reaction mixture was adjusted to ph 5 with HCl (0.5 mol/L) and diluted with 2000 mL of water. The resulting solution was extracted with 3×1500 mL of ether. The organic layers were combined, washed with 1×2000 mL of water and 1×2000 mL of saturated brine, dried and concentrated under vacuum. The residue was applied onto a silica gel column and eluted with ethyl acetate/petroleum ether (1:20˜1:15˜1:10) to afford the title compound.
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