16064-15-6

13794-72-4

16064-15-6

General procedure for the synthesis of 6,7-dihydroxyquinazolin-4(3H)-ones from 6,7-dimethoxyquinazolin-4-one: (i) In a 2.0 L four-necked round-bottomed flask equipped with a mechanical stirrer, reflux condenser and thermometer, 48% (w/w) hydrobromic acid (1000 g) and 6,7-dimethoxy-4(3H)-quinazolinone (100 g) were added. The reaction mixture was slowly heated to 110 °C and kept at this temperature for 1 hour. The temperature was then raised to reflux conditions and refluxed for 12 hours. The reaction progress was monitored by TLC. After completion of the reaction, the reaction mixture was cooled to 25-35 °C and filtered. The wet filter cake was transferred to another 2.0 L round bottom flask containing 1000 ml of deionized water, stirred for 10-15 min and the pH was adjusted to 7.0-7.5 by addition of ammonia aqueous solution. the resulting product was filtered, and the filter cake was washed with deionized water, and dried to give 85.2 g (98.62% theoretical yield) of 6,7-dihydroxy-4(3H)-quinazolinone as an off-white crystalline solid. Purity: 99.25% (HPLC); Melting point: >250°C. IR (KBr, cm-1): 3208.7, 1679.0, 1614.5, 1514.7, 1427.7, 1374.3, 1316.2, 1293.9, 1261.0, 1214.5, 1195.5, 866.0, 845.3, 780.7, 523.7, 523.3, 523.7, 6,7-dihydroxy-4(3H)-quinazolinone. 780.7, 523.8, 449.2.1H NMR (300 MHz, DMSO-d6): δ 6.93 (s, 1H), 7.35 (s, 1H), 7.84 (s, 1H), 9.75 (s, 1H), 10.13 (s, 1H), 11.2-12.4 (s, 1H).MS: 179 (M+1), 177 (M -1).