The general procedure for the synthesis of 7-bromothieno[3,2-d]pyrimidin-4(1H)-one from thieno[3,2-d]pyrimidin-4(3H)-one (38.0 g, 0.25 mol) was as follows: a dilution of bromine (40.4 mL, 0.78 mol) in acetic acid (122 mL, 2.1 mol) was slowly added to a thieno[3,2-d]pyrimidin -4(3H)-one solution in acetic acid (143 mL, 2.5 mol). The reactor was sealed and the reaction mixture was stirred at 120°C for 18 hours. Upon completion of the reaction, the mixture was cooled to room temperature and the acetic acid was subsequently removed by distillation under reduced pressure. The concentrate was poured into ice water and precipitate was precipitated, which was filtered and dried to afford the target compound 7-bromothieno[3,2-d]pyrimidin-4(1H)-one (37.5 g, 65% yield) without further purification. The product was characterized by 1H-NMR (300 MHz, DMSO-d6): δ 12.75 (brs, 1H), 8.36 (s, 1H), 8.24 (s, 1H).
![THIENO[3,2-D]PYRIMIDIN-4(3H)-ONE](/CAS/GIF/16234-10-9.gif)
![7-BROMOTHIENO[3,2-D]PYRIMIDIN-4(1H)-ONE](/CAS/GIF/31169-25-2.gif)