319442-18-7

319442-19-8

319442-18-7

Step B: Ethyl 4-oxo-3,4-dihydrothieno[3,2-d]pyrimidine-2-carboxylate (2.6 g, 11.6 mmol) was dissolved in phosphoryl chloride (20 mL) and the reaction was stirred at 105 °C overnight. Upon completion of the reaction, the mixture was concentrated under reduced pressure to remove the excess phosphoryl chloride. Subsequently, toluene was added and evaporated again under reduced pressure to completely remove the residual phosphoryl chloride. The crude product was dissolved in dichloromethane (DCM) and rapid filtration through a silica gel pad was performed to purify the product, resulting in ethyl 4-chlorothieno[3,2-d]pyrimidine-2-carboxylate (2.25 g, 80% yield). The structure of the product was confirmed by LC-MS (ESI), m/z 243 (M + H)+.