[NH:1]1[CH2:11][CH2:10][CH2:9][C@@H:3]([C:4]([O:6][CH2:7][CH3:8])=[O:5])[CH2:2]1.[CH:12](O)=O.C(=O)([O-])O.[Na+].[OH-].[Na+]>C=O>[CH3:12][N:1]1[CH2:11][CH2:10][CH2:9][C@@H:3]([C:4]([O:6][CH2:7][CH3:8])=[O:5])[CH2:2]1
(R)-Ethyl nipecotate (5.7 g 365 mmol), (prepared by resolution of ethyl nipecotate by treatment with L(+)-tartaric acid as described in J. Org. Chem. 1991, (56), 1168), was dissolved in 38.5% aqueous formaldehyde solution (45 ml) and formic acid (90 ml) and the mixture heated at reflux for 18 hours. The mixture was allowed to cool and added dropwise to cooled saturated aqueous sodium hydrogen carbonate solution. The mixture was adjusted to pH12 by addition of sodium hydroxide and the mixture was extracted with methylene chloride. The organic extract was washed with brine, dried (MgSO4) and the solvent removed by evaporation to give (R)-ethyl 1-methylpiperidine-3-carboxylate (4.51 g, 73%) as a colourless oil.
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