General procedure for the synthesis of 2,4-dichloro-5,6,7,8-tetrahydroquinazoline from 5,6,7,8-tetrahydroquinazoline-2,4(1H,3H)-dione: 5,6,7,8-tetrahydroquinazoline-2,4(1H,3H)-dione (8.0 g) was mixed with phosphorochloridic acid chloride (40 mL) and reacted at 120 °C for 1 hour. After completion of the reaction, the mixture was cooled to room temperature and the excess phosphoryl chloride was removed by distillation under reduced pressure. The residue was dissolved in ethyl acetate (400 mL) and water (200 mL) for partitioning. The organic phase was washed sequentially with saturated NaHCO3 solution (200 mL) and brine (200 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography to afford 2,4-dichloro-5,6,7,8-tetrahydroquinazoline (4.0 g, 57% yield) as a yellow solid.1H NMR (400 MHz, CDCl3) δ 1.8 (br s, 4H), 2.73 (br s, 2H), 2.88 (br s, 2H).MS m/z (M+H): 203.1.
