Synthesis
1. Preparation of 6-nitro-3H-quinazolin-4-one: 150 g of 2-amino-5-nitrobenzoic acid was added to 200 ml of formamide and stirred until completely dissolved. The reaction mixture was heated to 170°C and maintained at this temperature for 4 hours. After completion of the reaction, the mixture was cooled to 100°C. 500 ml of ice water was slowly added and stirring was continued for 1 hour. Subsequently, the mixture was filtered under reduced pressure and the solid product was collected. The solid was washed with plenty of water to remove residual reactants and by-products. Finally, the resulting solid was dried at 40 °C for 15 h to afford 4-hydroxy-6-nitroquinazoline (140 g, 90% yield). The structure of the product was confirmed by 1H-NMR (DMSO-d6, 300 MHz): δ8.77 (d, J = 2.7 Hz, 1H), 8.55 (dd, J = 6.9 Hz, 1H), 8.36 (s, 1H), 7.84 (d, J = 9 Hz, 1H).
References
[1] Patent: WO2006/71017, 2006, A1. Location in patent: Page/Page column 34
[2] Tetrahedron Letters, 2002, vol. 43, # 21, p. 3911 - 3913
[3] Tetrahedron Letters, 2003, vol. 44, # 24, p. 4455 - 4458
[4] Patent: US2005/187231, 2005, A1. Location in patent: Page/Page column 14
[5] Tetrahedron, 2013, vol. 69, # 15, p. 3182 - 3191
