To a solution of diisopropylamine (1.028 mL, 7.21 mmol, 1.8 eq.) dissolved in 10 mL of THF at 0 °C was slowly added n-butyllithium (3.76 mL, 6.01 mmol, 1.5 eq.). After 1 hr of reaction, the resulting LDA solution was transferred to a 35 mL THF solution containing 6-bromo-4-chlorothieno[2,3-d]pyrimidine (1.0 g, 4.01 mmol, 1.0 eq.) at -78 °C and under nitrogen protection. Stirring was continued at -78 °C for 1 h. A mixture consisting of 1.25 mL of water and 5 mL of THF was then slowly added. The reaction mixture was gradually warmed to 0 °C, poured into 60 mL of water and extracted with dichloromethane. The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give a yellow solid. The crude product was purified by silica gel column chromatography using a 20% ethyl acetate/hexane gradient elution to give 5-bromo-4-chlorothieno[2,3-d]pyrimidine (tan solid, 671 mg, 67.1% yield). NMR hydrogen spectrum (400 MHz, chloroform-d) δ 8.85 (s, 1H), 7.64 (s, 1H).
![6-BROMO-4-CHLOROTHIENO[2,3-D]PYRIMIDINE](/CAS/GIF/56844-12-3.gif)
![5-bromo-4-chlorothieno[2,3-d]pyrimidine](/CAS/GIF/814918-95-1.gif)