A mixture of 3-(2-chloroethyl)-2,4-(1H,3H)-quinazolinedione (1.57 kg), 1-(2-methoxyphenyl)piperazine (1.34 kg), sodium iodide (1.05 kg) and potassium carbonate (0.49 kg) was dissolved in dimethylformamide (7,000 ml) and the solution was heated at an internal temperature of 80°-85° C. for 7 hours. After completion of the reaction, the mixture was cooled by the addition of water (25 l) and ice (5 kg). The cooled mixture was left for 24 hours and the resulting crystal was collected, washed with water and dried with heat to give 3-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-2,4-(1H,3H)quinazolinedione (2.3 kg). Its physicochemical data was the same as that of the products obtained in Example 1.
