Sodium Thiosulfate → HCID 86697949, Verbindung

2.3 g of 3-chloroperoxybenzoic acid (75%) are added slowly, in fractions, to a solution of 1.6 g of methyl 2-(methylsulfanyl)-7-phenylthieno[3,2-d]pyrimidine-6-carboxylate (example 4) in 25 ml of dichloromethane, cooled in an ice bath. The mixture is stirred for 2.5 h while cold, and then left at ambient temperature overnight. The mixture is then diluted with 80 ml of dichloromethane and treated with 60 ml of saturated sodium thiosulfate solution. After stirring and settling out, the aqueous phase is extracted with 60 ml of dichloromethane. The organic phases are washed with 60 ml of a saturated sodium bicarbonate solution, and then with 60 ml of a saturated sodium chloride solution. The organic phases are dried over magnesium sulfate, filtered, and then concentrated under vacuum so as to obtain the crude product, which is purified on 200 g of silica, elution being carried out with dichloromethane, so as to obtain 1.4 g of methyl 2-(methylsulfonyl)-7-phenylthieno[3,2-d]pyrimidine-6-carboxylate in the form of a white solid.