[OH:1][CH:2]1[C:7]([O:10][CH3:11])([O:8][CH3:9])[CH2:6][CH2:5][N:4]([C:12]([O:14][CH2:15][CH3:16])=[O:13])[CH2:3]1.[H-].[Na+].I[CH3:20]>CN(C)C=O>[CH3:20][O:1][CH:2]1[C:7]([O:8][CH3:9])([O:10][CH3:11])[CH2:6][CH2:5][N:4]([C:12]([O:14][CH2:15][CH3:16])=[O:13])[CH2:3]1To a stirred mixture of 35 parts of ethyl 3-hydroxy-4,4-dimethoxy-1-piperidinecarboxylate and 144 parts of N,N-dimethylformamide were added portionwise 8.2 parts of sodium hydride dispersion 50%: exothermic reaction (temp. roses to 30° C.; cooling in a water-bath was necessary to keep the temperature below 30° C.). The whole was stirred for 1.50 hours at about 30° C. and then it is cooled to room temperature. 24.1 Parts of iodomethane were added dropwise (strong exothermic reaction) while the temperature was kept below 30° C. Upon completion, stirring was continued over week-end at room temperature. The reaction mixture was poured onto water and the product was extracted with 4-methyl-2-pentanone. The extract was washed with water, dried, filtered and evaporated, yielding 35.9 parts (95.7%) of ethyl 3,4,4-trimethoxy-1-piperidinecarboxylate as an oily residue (intermediate 64).
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