Hydrochloric Acid → 3-(4-Bromophenyl)piperidine

To an ice-cooled solution of 3-(4-bromo-phenyl)-piperidin-2-one (37.97 g, 149 mmol) in tetrahydrofuran (250 ml) was added borane-tetrahydrofuran complex (335 ml, 1.0 M solution in THF, 335 mmol). The solution was stirred overnight at room temperature, and then refluxed 1.5 hr after addition of 10% aqueous hydrochloric acid. Solvents was removed in vacuo, and the residue was partitioned between dichloromethane and 1N sodium hydroxide. The aqueous layer was extracted with dichlorometane. The combined organic layer was washed with water and brine, dried over sodium sulfate, and concentrated in vacuo. The residue was dissolved in water (100 mL) and concentrated hydrochloric acid (100 mL) and refluxed for 3 hr. Sodium hydroxide was added to the solution and the resulting solution was extracted with dichlorometane. The organic layer was washed with water and brine, dried over sodium sulfate Concentration in vacuo afforded 3-(4-bromo-phenyl)-piperidine (32 18 g, 90%).