43088-67-1

43088-64-8

43088-67-1

Step 2. Preparation of 4-chloro-5-methylthieno[2,3-d]pyrimidine: 5-methylthieno[2,3-d]pyrimidin-4(3H)-one (1.4 g, 8.42 mmol) prepared in Step 1 was dissolved in phosphorochloridic acid (5 mL). Subsequently, the reaction mixture was stirred at 110°C for 1 hour. Upon completion of the reaction, the reaction mixture was slowly poured into a mixture of ice water and chloroform and washed sequentially with water and saturated aqueous sodium bicarbonate. The organic layers were combined and concentrated under reduced pressure. The residue was purified by recrystallization (hexane/ethyl acetate mixed solvent) to give 590 mg (yield: 39%) of the target product 4-chloro-5-methylthieno[2,3-d]pyrimidine as a yellow solid.1H NMR (400 MHz, CDCl3): δ 8.81 (s, 1H), 7.24 (s, 1H), 2.70 (s, 3H).