[OH:1][CH2:2][CH2:3][CH:4]1[CH2:9][CH2:8][NH:7][CH2:6][CH2:5]1.[F:10][C:11]1[CH:18]=[CH:17][C:14]([CH:15]=O)=[CH:13][CH:12]=1.C1(C)C=CC(S(O)(=O)=O)=CC=1.O>C1C=CC=CC=1>[F:10][C:11]1[CH:18]=[CH:17][C:14]([CH2:15][N:7]2[CH2:8][CH2:9][CH:4]([CH2:3][CH2:2][OH:1])[CH2:5][CH2:6]2)=[CH:13][CH:12]=1A mixture of 4-(2-hydroxyethyl)piperidine (21.5 g), 4-fluorobenzaldehyde (17.5 ml) and p-toluene sulfonic acid (3 mg) in benzene (200 ml) was refluxed with separating water as the benzene azeotrope. After 2 hours, the mixture was evaporated in vacuo. The residue was dissolved in methanol (200 ml) and sodium borohydride (6.3 g) was added thereto at 5° C. After stirring at ambient temperature for 1 hour, the mixture was evaporated in vacuo. 4N Hydrochloric acid (200 ml) was added to the residue and washed with ethyl acetate. The aqueous layer was made basic to pH 10 with potassium carbonate and extracted with ethyl acetate. The extract was washed with water and brine, and dried over magnesium sulfate, and evaporated in vacuo to give 1-(4-fluorobenzyl)-4-(2-hydroxyethyl)piperidine (32.0 g) as an oil.
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