1) A mixture of 7-chloro-6-nitro-3H-quinazolin-4-one (approx. 3:1 ratio, 52.0 g; for preparation, see Leonard et al. J. Org. Chem. 1975, 40, 356-363) was added to thionyl chloride (200 mL) along with DMF (0.7 mL) and heated to reflux for 4 hr. Upon completion of the reaction, the mixture was concentrated to dryness, added toluene (150 mL) and concentrated again. This concentration step was repeated twice, after which dichloromethane (280 mL) was added to the residue with stirring at room temperature.
2) Isopropanol solution (760 mL) of 3-chloro-4-fluoroaniline (36.9 g, 253.6 mmol) was added slowly and dropwise to the above suspension, followed by the addition of methylene chloride (300 mL), and stirred at 20°C for 20 minutes.
3) Under cooling in an ice bath, hexane (600 mL) was added to the mixture and stirring was continued at 20°C. The precipitate was collected by filtration, washed with hexane (200 mL x 2) and dried under reduced pressure.
4) The resulting solid was suspended in a solvent mixture of methanol (1 L) and water (120 mL), and triethylamine (30 mL) was added slowly under cooling in an ice bath. After stirring for 1 hour at room temperature, the precipitate was collected by filtration and washed with water (700mL×2).
(5) The crude product (65 g) was washed with acetonitrile (1.2 L) suspended under heating conditions and filtered to obtain the target compound 7-chloro-N-(3-chloro-4-fluorophenyl)-6-nitro-4-aminoquinazoline (54.6 g, 67% yield).
