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After 4-(2-bromo-5-methoxybenzyl)piperidine hydrochloride (16.00 g, 50.22 mmol) was suspended in a 1N aqueous sodium hydroxide solution (100 ml), the organic substance liberated was extracted with diethyl ether, and the organic layer was dried over anhydrous potassium carbonate and distilled under reduced pressure to remove the solvent. While cooling a solution of the thus obtained free amine in dichloromethane (100 ml) at 0° C., a 1.0M solution (100 ml) of boron tribromide in dichloromethane was added dropwise thereto over a period of 5 hours and the resulting mixture was stirred at room temperature for 3.5 hours. The reaction was terminated by adding methanol (500 ml), and the reaction mixture was stirred for 10 minutes and then distilled under reduced pressure to remove the solvent. The residue was dissolved in a 4N aqueous sodium hydroxide solution (200 ml) and washed with diethyl ether, and then acetic acid was added dropwise thereto until the aqueous layer became neutral. The gummous substance produced was extracted with ethyl acetate and the organic layer was dried over anhydrous sodium sulfate and distilled under reduced pressure to remove the solvent, whereby 4-(2-bromo-5-hydroxybenzyl)piperidine (9.93 g, 37.03 mmol) was obtained in a yield of 74%.

1. extractionthe organic substance liberated was extracted with diethyl ether
2. dry with materialthe organic layer was dried over anhydrous potassium carbonate
3. distillationdistilled under reduced pressure
4. customto remove the solvent
5. additiona 1.0M solution (100 ml) of boron tribromide in dichloromethane was added dropwise
6. customThe reaction was terminated
7. additionby adding methanol (500 ml)
8. stirringthe reaction mixture was stirred for 10 minutes
9. distillationdistilled under reduced pressure
10. customto remove the solvent
11. dissolutionThe residue was dissolved in a 4N aqueous sodium hydroxide solution (200 ml)
12. washwashed with diethyl ether
13. additionacetic acid was added dropwise
14. customThe gummous substance produced
15. extractionwas extracted with ethyl acetate
16. dry with materialthe organic layer was dried over anhydrous sodium sulfate
17. distillationdistilled under reduced pressure
18. customto remove the solvent