To a solution of n-butanol (316 ml), water (24 ml) and N-(2-
tetrahydrofuroyl)piperazine (20 g) were added, while stirring, 4-amino-2-
chloro-6,7-dimethoxyquinazoline (22.2 g). The reaction mixture was heated to
reflux and the reflux was maintained for about 9 h. Then the reaction mixture
was cooled to room temperature and stirred at this temperature for about 10-
12 h. The crystals were collected by filtration, washed with n-BuOH and dried
in vacuo at 40-50°C to yield 40.1 g (94%) of the 1-(4-amino-6,7-dimethoxy-
2-quinazolinyl)-4-(tetrahydrofuroyl)piperazine hydrochloride dihydrate
