(R)-Omeprazole

73590-85-9

119141-89-8

GENERAL STEPS: Sulfide (5-methoxy-2-[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]thio]benzimidazole, 100 mmol) and titanium-tannic acid catalyst (1.1 mmol) were dissolved in ethyl acetate (EtOAc, 6.0 mL). The reaction mixture was kept at a constant temperature to the indicated temperature (usually 0°C, or in the range of -20 to +20°C for variable temperature experiments). Subsequently, a 30% aqueous hydrogen peroxide solution (0.105 mmol H2O2) was added all at once. The reaction mixture was continuously stirred at 500 rpm at a constant temperature (usually 24 h). For low-temperature experiments, the reaction time was about 30 h at -10 °C, which could be extended to 10 days at -20 °C. To analyze the progress of the reaction, 20 μL of the reaction mixture was taken into a vial and immediately evaporated carefully to dryness (~15-20 s) with a stream of compressed air. The residual solid was dissolved in isopropanol solution (0.20 mL) containing 1% triethylamine (Et3N), and the residual sulfide, (R)- and (S)-sulfoxide, and sulfone contents were analyzed by chiral HPLC.