The general procedure for the synthesis of 4,6-dichloropyrimidine-5-acetaldehyde from 5-allyl-4,6-dichloropyrimidine was as follows: in a 50 mL three-necked flask equipped with a magnetic stirrer, 20 mL of dichloromethane and 4,6-dichloro-5-allylpyrimidine (5.0 g, 0.026 mol) were added sequentially, followed by dimethyl sulfoxide (8 g, 0.104 mol) and triethylamine. After cooling the reaction mixture to -40°C, ozone (O3) was passed through until the reaction solution took on a blue color, at which point the ozone passage was stopped and switched to nitrogen (N2) protection for 30 minutes to completely remove ozone from the system. Next, thiourea (2.0 g, 0.026 mol) was added to the reaction system and the reaction mixture was allowed to warm up to room temperature naturally. The reaction system was tested using starch potassium iodide test paper to confirm that no peroxide was present (the paper did not turn blue). Finally, 60 mL of water was added to the reaction mixture and extracted twice with dichloromethane. The yield of this step was 88%.
