1 - benzyl - 4 -- 2 - yl ] methylpiperidine or hydrochloride thereof , which is useful as a drug , can be produced in high purity by safer and easier operations suitable for industrial production by subjecting 1 - benzyl - 4 -- 2 - ylidene ] methyl - piperidine or a solvate thereof to catalytic hydrogenation in the presence of a palladium - alumina catalyst and if necessary , converting the thus obtained compound to its hydrochloride .