Thionyl chloride (2.0 molar equivalents) was slowly added dropwise to a stirred solution of anhydrous ethanol (10.0 molar equivalents) pre-cooled to 0 °C under argon protection. The reaction temperature was maintained at 0 °C with continuous stirring for 1 hour and then gradually warmed up to room temperature. Subsequently, 2-aminoisobutyric acid (1.0 molar equivalent) was added and the reaction mixture was heated to reflux overnight. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure and finally the residual trace solvent was removed by azeotropic distillation. The crude product was ground with ether to give purified ethyl 2-aminoisobutyrate hydrochloride. In Example 14, ethyl 2-aminoisobutyrate hydrochloride (Product 14n) was prepared according to the method of Example 1 (A) as a white solid (9.12 g, 776.0 mmol) from 2-aminoisobutyric acid (8.0 g, 77.6 mmol), thionyl chloride (11.3 mL, 155.2 mmol) and anhydrous ethanol (45.5 mL, 776.0 mmol). (70% yield). Its 1H-NMR (CDCl3; 300 MHz) and 13C-NMR (CDCl3; 75 MHz) data were consistent with the expected structure.
