Synthesis of 6-methylquinazoline-2,4-dione: 2-amino-5-methylbenzoic acid (0.758 g, 5 mmol) and potassium cyanate (0.673 g, 8.3 mmol) were suspended in water (20 mL) followed by addition of acetic acid (0.5 mL). The reaction mixture was stirred at room temperature for 24 hours. Upon completion of the reaction, the resulting white solid product was collected by vacuum filtration, washed with water and dried under vacuum to afford 6-methylquinazoline-2,4-dione (0.736 g, 84% yield). The structure of the product was confirmed by 1H NMR (DMSO-d6): δ 9.90 (br s, 1H), 8.27 (d, J = 8.4 Hz, 1H), 7.70 (d, J = 1.8 Hz, 1H), 7.29 (dd, J = 2.4, 8.7 Hz, 1H), 6.50 (br s, 1H), 2.25 (s, 3H).
