Tetrahydro-2H-thiopyran-3-one

63449-37-6

19090-03-0

GENERAL STEPS: Concentrated sulfuric acid (2 mL, 36.00 mmol) was added to a solution in water (50 mL) containing equimolar ratios of ethyl 3-oxotetrahydro-2H-thiopyran-2-carboxylate and ethyl 3-oxotetrahydro-2H-thiopyran-4-carboxylate (total 8.92 g, 23.69 mmol). The reaction mixture was stirred at room temperature followed by continuous stirring under reflux conditions for 18 hours. Upon completion of the reaction, the reaction mixture was diluted with ether (125 mL) and two-phase separation was carried out. The organic layer was dried with anhydrous magnesium sulfate, filtered and the solvent was evaporated to give the crude product. The crude product was purified by reduced pressure distillation (1 Torr) and the fractions distilled at 45 °C were collected to give the final dihydro-2H-thiopyran-3(4H)-one (1.693 g, 61.5% yield) as a colorless liquid.