Synthesis
(5)-Mandelic acid (40.2 g, 264.5 mmol) was added to a solution of 3:2 isopropyl alcohol (/PrOH) and ethanol (EtOH) (500 mL) at room temperature, and the suspension was heated at 60 °C until a clear solution formed. Racemic 2,4-dichloro-a-methyl benzylamine (50 g, 264.5 mmol) was added to the hot solution, which was then cooled to 30 °C over 2 h and stirred at this temperature for 24 h. The colorless crystals were collected by filtration and washed with acetone (70 mL). The resulting salt was suspended in 3:2 /PrOH/EtOH (400 mL) at room temperature and the mixture was heated at 60 °C to give a clear solution. The solution was then cooled to room temperature and stirred for 24 hours. The colorless crystals were filtered off, and washed with acetone (40 mL) to give the desired salt. A portion of the salt (12.0 g) in dichloromethane (CH2C12) (100 mL) was added to aqueous 4 N sodium hydroxide solution (30 mL). The reaction mixture was stirred for 1 h at room temperature, and extracted with dichloromethane (2 χ 100 mL), dried with anhydrous sodium sulfate (Na2S04), filtered, and concentrated in vacuo to afford (R)-1-(2,4-Dichlorophenyl)ethanamine as a colorless liquid (7.5 g, 39.5 mmol, 40%).
