To a stirred mixture of 2-amino-5-nitrobenzoic acid (5.0 g, 28 mmol) and imidazole (2.2 g, 33 mmol) in acetonitrile (50 mL), was added acetyl chloride (2.3 mL, 33 mmol) at room temperature. The mixture was stirred at room temperature overnight. To the mixture, was added 3-amino-piperidine-2,6-dione hydrogen chloride (4.5 g, 28 mmol), imidazole (4.1 g, 60 mmol) and triphenyl phosphite (8.7 mL, 33 mmol) and heated to reflux for 22 hours. To the mixture, was added water (60 mL). The suspension was filtered and washed with water (2×50 mL), ethyl acetate (2×50 mL), and water (50 mL) to give 3-(2-methyl-6-nitro-4-oxo-4H-quinazolin-3-yl)-piperidine-2,6-dione as an off-white solid (5.3 g, 61% yield): 1H NMR (DMSO-d6) δ 2.19-2.26 (m, 1H, CHH), 2.60-2.69 (m, 2H, 2CHH), 2.72 (s, 3H, CH3), 2.79-2.87 (m, 1H, CHH), 5.37 (dd, J=5, 11 Hz, 1H, NCH), 7.83 (d, J=9 Hz, 1H, Ar), 8.56 (dd, J=3, 9 Hz, 1H, Ar), 8.74 (dt, J=3 Hz 1H, Ar), 11.12 (s, 1H, NH); 13C NMR (DMSO-d6) δ 20.69, 23.82, 30.57, 56.98, 119.46, 120.20, 122.21, 128.45, 128.74, 144.90, 150.85, 159.13, 159.78, 169.12, 172.53.
