[N:1]1([C:12]([O:14][CH2:15][C:16]2[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=2)=[O:13])[CH2:6][CH2:5][CH2:4][CH:3]([C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH2:2]1.[CH3:22][Si]([N-][Si](C)(C)C)(C)C.[Li+].CI.[Cl-].[NH4+]>C1COCC1>[CH3:22][C:3]1([C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH2:4][CH2:5][CH2:6][N:1]([C:12]([O:14][CH2:15][C:16]2[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=2)=[O:13])[CH2:2]1To 1-benzyl 3-ethyl piperidine-1,3-dicarboxylate (3.0 g, 10.3 mmol) in THF (20 mL) was added lithium bis(trimethylsilyl)amide (12.9 mL, 12.9 mmol) in THF at −78° C., and the reaction was stirred at this temperature for 20 minutes. MeI (0.867 mL, 13.9 mmol) was added, and the reaction was warmed to room temperature. After 2 hours at room temperature, the mixture was poured onto saturated ammonium chloride (20 mL) and extracted with ether, washed with brine and dried over sodium sulfate. After removal of the solvent, the residue was purified by chromatography on silica gel (hexane:ethyl acetate 5:1) to give 1-benzyl 3-ethyl 3-methylpiperidine-1,3-dicarboxylate (3.1 g, 98% yield) as an oil.
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