Yield:952740-00-0 88%

Reaction Conditions:

with pyridine;dmap in dichloromethane at 20; for 4.16 h;

Steps:

Preparation of enol acetate (R = methyl); To a suspension of oxcarbazepine (69.3 g, 0.275 mol), DMAP (1.025 g) and acetic anhydride (38.07 g) in dichloromethane (700 mL) was added drop wise a solution of 30.1 g pyridine in 50 mL dichloromethane at room temperature. The addition completed in 10 min. After stirring at room temperature for 75 min, the system became clear. Three hours after the addition, the system became cloudy again. The suspension was then stirred at room temperature for one more hour and washed with 2 x 400 mL of 1 N HCl, 2 x 400 mL of 10% NaHCO₃ and 2 x 400 mL of H₂O. Concentration under reduced pressure afforded a light yellow solid. Isopropyl alcohol (700 mL) was added and the mixture was refluxed for 3 min. When it cooled down, the solid was filtered off and washed with 2 x 100 mL isopropyl alcohol. Isopropyl alcohol (500 mL) was added and the mixture was refluxed for 2 min. When it cooled down, the solid was filtered off and washed with 3 x 100 mL isopropyl alcohol (This second wash may not be necessary). The final product was dried under vacuum and obtained as a white solid (71.5 g) in 88% yield. IH NMR (DMSO-d6, 360 MHz): δ = 7.53-7.30 (m, 8H), 6.92 (s, IH), 5.66 (b, 2H), 2.32 (s, 3H) ppm. 13C NMR (DMSO-d6, 90 MHz): δ = 169.5, 156.2, 146.8, 140.7, 140.4, 132.8, 132.1, 131.1, 129.8, 129.7, 129.4, 127.9, 127.6, 125.9, 120.8, 21.1 ppm.

References:

WO2007/117166,2007,A1 Location in patent:Page/Page column 12-13