Potassium;tri(butan-2-yl)boranuide → cis-3-Hydroxy-4-(3,4-dimethylphenoxy)-1-carbobenzyloxy-piperidine

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Reaction Steps

10.0 g (0.028 mol) of the 4-(3,4-dimethylphenoxy)-1-carbobenzyloxy-3-piperidone described in Example 44 are dissolved in 60 ml of dry tetrahydrofurane and the solution is treated dropwise, at room temperature in a nitrogen atmosphere, with 112 ml of a 0.5 M solution of potassium tri-sec.-butylborohydride (K selectride) (0.056 l mol) in tetrahydrofurane. After the addition has ended, the reaction mixture is stirred for a further 3 hours at room temperature and then concentrated to about 1/3 of the original volume under a water pump vacuum. The solution is cooled to 0° in an ice-water bath, treated dropwise with 130 ml of water and extracted by shaking with twice 150 ml of methylene chloride. The combined organic phases are washed with 0.1 N hydrochloric acid, then with 0.1 N sodium hydroxide solution and finally with water, dried over sodium sulphate and evaporated to dryness under a water pump vacuum. The oily crude product is dissolved in toluene and the solution is filtered through a layer of silica gel. cis-3-hydroxy-4-(3,4-dimethylphenoxy)-1-carbobenzyloxy-piperidine is obtained in the form of a pale yellow oil by elution with a toluene/ethyl acetate mixture (5:1).

Provenance & Evidence