[H-].[Na+].[OH:3][C:4]1([CH3:17])[CH2:9][CH2:8][N:7]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:6][CH2:5]1.[CH3:18]I>CN(C)C=O.O.[Cl-].[Na+].O>[CH3:18][O:3][C:4]1([CH3:17])[CH2:5][CH2:6][N:7]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:8][CH2:9]1Sodium hydride (60% dispersion on mineral oil) (198 mg, 4.95 mmol) was added portionwise to tert-butyl 4-hydroxy-4-methylpiperidine-1-carboxylate (21) (710 mg, 3.30 mmol) in N,N-dimethylformamide (12 mL) at ambient temperature over a period of 30 seconds under an air atmosphere. The resulting suspension was stirred at 25° C. for 20 minutes. Methyl iodide (0.411 mL, 6.60 mmol) was then and the resulting suspension was stirred at 25° C. for 18 hours. The reaction mixture was diluted with water (150 mL) and saturated brine (25 mL), then washed sequentially with dichloromethane (3×100 mL). The organic layer was dried over MgSO4, filtered and evaporated to afford crude product, which was used directly in the next stage.
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