1-Acetylnaphthalene (8 g, 0.047 mol), paraformaldehyde (2 g, 0.065 mol) and dimethylamine hydrochloride (5.3 g, 0.065 mol) were dissolved in ethanol (15 mL), followed by the addition of 0.6 mL of concentrated hydrochloric acid. The reaction mixture was heated to reflux for 12 hours, after which it was cooled to room temperature and refrigerated at -20 °C overnight. A white solid precipitated from the reaction mixture, which was separated by filtration and washed with ethanol. The resulting white solid was dissolved in water and 50% aqueous sodium carbonate solution (5.8 g, 0.54 mol) was slowly added. After stirring for 10-15 min, the aqueous phase was extracted with ethyl acetate (20 mL x 3), the organic layers were combined, washed sequentially with water (15 mL x 2) and saturated saline (15 mL x 2), and dried over anhydrous sodium sulfate. After filtration, the solvent was evaporated under reduced pressure to obtain the target compound 3-dimethylamino-1-(naphthalen-5-yl)acetone as a colorless oil (8 g, 70% yield).
