[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[CH2:20][CH3:21]>CN(C)C=O>[CH2:20]([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]1)[CH3:21]To a stirred solution of 35 parts of ethyl 3-hydroxy-4,4-dimethoxy-1-piperidinecarboxylate in 144 parts of N,N-dimethylformamide were added portionwise 8.2 parts of a sodium hydride dispersion 50% at about 30° C. After stirring for 1.50 hours at about 30° C., the mixture was cooled to room temperature and 26.5 parts of iodoethane were added dropwise at a temperature below 30° C. Upon completion, stirring was continued for 18 hours 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 34.1 parts (87%) of ethyl 3-ethoxy-4,4-dimethoxy-1-piperidinecarboxylate as a residue (intermediate 67).
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