Step B: Synthesis of 4-chloro-6-iodoquinazoline. Anhydrous dimethylformamide (DMF, 3.20 ml) was added to a stirred solution of 1,2-dichloroethane (DCE, 10 ml) under nitrogen protection and subsequently cooled in an ice water bath. A solution of oxalyl chloride (5.2 ml, 60 mmol) in DCE (25 ml) was slowly added dropwise. Formation of white precipitate was observed during dropwise addition. After completion of dropwise addition, the ice water bath was removed and the reaction mixture was continued to be stirred at room temperature for 5 minutes. Under nitrogen atmosphere, 6-iodo-4(H)-quinazolinone (5.0 g, 18 mmol) was added in batches, followed immediately by heating the mixture to reflux. After maintaining the reflux reaction for 4.5 h, it was cooled to room temperature. The reaction mixture was poured into an excess of ice-water mixture (about 300 ml) and extracted with dichloromethane (DCM, about 500 ml). The aqueous layer was further extracted with DCM (2 x 50 ml). All organic extracts were combined, dried with anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure to give 5.2 g (99% yield) of 4-chloro-6-iodoquinazoline as a brown solid.
