10.00 kg (33.66 mol) of 3-methyl-7-(2-butin-1-yl)-8-bromoxanthine, 7.13 kg (37.02 mol) of 2-chloromethyl-4-methylquinazoline, 3.92 kg (37.02 mol) of anhydrous sodium carbonate and 30 liters of N-methyl-2-pyrrolidone are initially charged in the reactor. The reactor contents are heated to 140° C. and stirred at 140° C. for 2 hours. After the reaction has ended, the reaction mixture is cooled to 80° C. and diluted with 60 liters of 96% ethanol and subsequently at 70° C. with 55 liters of water. At 60° C., 4.04 kg (67.32 mol) of acetic acid are metered in and flushed in with 5 liters of water. The resulting suspension is stirred at 60° C. for 30 minutes, then cooled to 23° C. and stirred for a further 30 minutes. Subsequently, the product is centrifuged off and washed first with a mixture of 20 liters of 96% ethanol and 20 liters of water, then with 40 liters of 96% ethanol and 40 liters of water. Drying is effected at 45° C. in a drying cabinet under inertization.
