General procedure for the synthesis of 6-chloropyrimidine-2,4(1H,3H)-dione from 2,4,6-trichloropyrimidine: 2,4,6-trichloropyrimidine (10.21 g, 0.56 mol) was dissolved in an aqueous solution (100 mL) containing NaOH (8.9 g, 0.22 mol), which was stirred under refluxing conditions for 1 hour. Upon completion of the reaction, the pH of the reaction mixture was adjusted to 2-3 with concentrated hydrochloric acid. the mixture was placed in a refrigerator overnight to promote crystallization. Subsequently, the precipitate was collected by filtration, washed with cold water and dried under vacuum in the presence of phosphorus pentoxide. 6.43 g (0.54 mol, 97% yield) of 6-chlorouracil was finally obtained as a white crystalline solid. The spectral data of the product were in agreement with those reported in the literature [28] and [40]. Melting point > 280°C. 1H NMR (300 MHz, DMSO-d6) δ (ppm): 12.00 (broad peak, 1H, NH), 11.09 (broad peak, 1H, NH), 5.66 (single peak, 1H, CH). IR (KBr, ν cm-1): 3095 (N-H stretching vibration), 1729,1709,1652 (C=O stretching vibration), 1616 (C=C stretching vibration), 1380 (C-N stretching vibration), 841 (N-H out-of-plane bending vibration), 790 (C-Cl stretching vibration).
