1-Benzyl-4-piperidone → 1-benzyl-N-methylpiperidin-4-amine

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Reaction Steps

A mixture of 1-benzyl-4-piperidone (XXV, Chart G, 24.5 mL, 0.1295 mol), N-methylamine hydrochloride (44.75 g, 0.6628 mol) and methanol (50 ml) is stirred for 35 minutes at 20°-25°, at which time additional methanol (10 ml) is added. The mixture is then cooled in an ice bath and a solution of sodium cyanoborohydride (9.1749 g, 0.1460 mol) in methanol (68 ml) is added to the mixture. The mixture is stirred for 5 min and then is allowed to warm to 20°-25°. After 1.25 hr the mixture is concentrated under reduced pressure and saturated aqueous sodium bicarbonate is added. After stirring for 1 hr, the mixture is extracted with dichloromethane and the organic phases are combined, backwashed with saline, dried with magnesium sulfate and concentrated under reduced pressure to give (XXVII). The material is upgraded by forming the dihydrochloride salt and collecting the resulting solids. The dihydrochloride salt is further upgraded by trituration with dichloromethane. The free base (XXVII) is recovered by slurrying the dihydrochloride salt (7.5204 g, 0.02713 mol) in dichloromethane and adding enough saturated sodium bicarbonate to dissolve all the solids and then extracting the aqueous layer exhaustively with dichloromethane to obtain N-(1-benzylpiperidin-4-yl)-N-methylamine (XXVII), MS (m/z) 204; IR (neat) 2942, 2796, 2775, 743 and 2749 cm-1.

Provenance & Evidence