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4.4 g (0.0157 mol) of N-[2-(3,4-dimethoxy-phenyl)-ethyl]-3(hydroxymethyl)-piperidine are dissolved in 70 ml of carbon tetrachloride and cooled to 0° C. Then 1.63 ml (0.0173 mol) of phosphorus tribromide is added, whereupon a bulky precipitate is immediately formed. The mixture is stirred for 15 hours at ambient temperature, water is added and the mixture is neutralized with 2 molar sodium hydroxide solution. The organic phase is separated off, washed with water, dried over magnesium sulphate, concentrated by evaporation in vacuo and purified over 310 g of aluminium oxide (neutral, activity II-III) with methylene chloride and then with increasing amounts of ethanol (up to 5%). Yield: 2.0 g (37.2% of theory), Rf value: 0.5 (aluminium oxide neutral, eluant: 2% ethanol in methylene chloride).

1. customis immediately formed
2. customThe organic phase is separated off
3. washwashed with water
4. dry with materialdried over magnesium sulphate
5. concentrationconcentrated by evaporation in vacuo
6. custompurified over 310 g of aluminium oxide (neutral, activity II-III) with methylene chloride