Step A: Synthesis of chloromethyl isobutyrate
To a solution of isobutyric acid (0.600 mL, 6.47 mmol) in dichloromethane (DCM, 6 mL) was added sodium bicarbonate (2092 mg, 24.91 mmol), tetrabutylammonium hydrogensulfate (220 mg, 0.65 mmol), and water (6 mL) in that order. Chloromethyl chloroformate (0.767 mL, 7.44 mmol) was added slowly at room temperature with rapid stirring. After addition, the reaction mixture was continued to stir at room temperature overnight. Upon completion of the reaction, the reaction mixture was diluted with dichloromethane (10 mL) and subsequently washed with water (2 x 10 mL). The organic phase was dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated to afford the crude chloromethyl isobutyrate (746 mg, 84% yield). The product was used directly in the next step of the reaction without further purification.
1H NMR (500 MHz, CDCl3) δ ppm: 1.17 (m, 6H), 2.62 (m, 1H), 5.72 (s, 2H).
