Thieno[2,3-d]pyrimidin-4(3H)-one was synthesized from methyl 2-aminothiophene-3-carboxylate (3.0 g, 19.1 mmol) and formamide (95 ml) by heating and reacting at 190 °C for 4 hours. After completion of the reaction, the mixture was cooled to room temperature and poured into water. The precipitate was collected by filtration, washed with water and dried. The crude product was purified by silica gel column chromatography (eluent: CH2Cl2/MeOH = 50:1) to afford the target compound thieno[2,3-d]pyrimidin-4(3H)-one as a white solid (1.93 g, 66% yield). The structure of the product was confirmed by 1H NMR (300 MHz, DMSO, 25 °C) and HRMS: 1H NMR δ= 12.49 (s, 1H, NH), 8.13 (s, 1H, CH), 7.58 (d, J = 5.8 Hz, 1H, CH), 7.39 (d, J = 5.8 Hz, 1H, CH) ppm; HRMS (calculated) C6H5N2OS: 153.01226, measured value: 153.01155).
![Thieno[2,3-d]pyrimidin-4(3H)one](/CAS/GIF/14080-50-3.gif)