3-(tert-Butyl)-6-(ethylthio)-1,3,5-triazine-2,4(1H,3H)-dione is used as Ensitrelvir intermediates.
T-Butyl isocyanate (1.2 mL, 10.5 mmol) and DBU (1.9 mL, 12.8 mmol) were added to mixture of S-ethylthiourea hydrobromate (1.85 g, 10 mmol) and DMF (9.3 mL) under ice-cooling, and the resulting mixture was stirred for 6 hours. 1,1′-Carbonyldiimidazole (1.95 g, 12 mmol) and DBU (1.9 mL, 12.8 mmol) were added to the reaction mixture under ice-cooling, and the mixture was stirred for 2 hours. 2 mol/L Hydrochloric acid (80 mL) was added to the reaction mixture under ice-cooling over 50 minutes, and the generated powder was collected by filtration. The powder was dissolved in ethyl acetate, dried over anhydrous magnesium sulfate, and concentrated in vacuo to give 3-(tert-Butyl)-6-(ethylthio)-1,3,5-triazine-2,4(1H,3H)-dione (1.15 g, yield: 50%) as pale brown powder.
