To a solution of m-aminobenzonitrile (1.0 g, 8.5 mmol) and formaldehyde (2.1 g, 69.0 mmol) in acetonitrile (20 mL) was added sodium cyanoborohydride (2.7 g, 42.5 mmol). The reaction mixture was stirred at room temperature for 2 hours. Acetic acid (100 mL) was added to adjust the pH to 7 and stirring was continued for 2 hours. Potassium hydroxide solution (1N, 100 mL) was then added and the mixture was extracted with ethyl acetate (100 mL x 2). The organic layers were combined, washed with saturated saline (80 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography with petroleum ether/ethyl acetate (10:1) as eluent to give 3-(dimethylamino)benzonitrile (1.3 g, 100%) as a colorless oil. Mass spectrum (MS): m/z 147.3 ([M+H]+).
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