[S:1]1[CH2:6][CH2:5][C:4](=[O:7])[CH2:3][CH2:2]1.[C:8]1(C)C=CC(S(O)(=O)=O)=C[CH:9]=1>C1(C)C=CC=CC=1>[CH:6]12[S:1][CH:2]([CH2:8][CH2:9]1)[CH2:3][C:4](=[O:7])[CH2:5]2Tetrahydrothiopyran-4-one (19.1 g, 150 mmol), ethylene-1,2-diol (11.2 g. 180 mmol), toluene-p-sulfonic acid (0.5 g), and toluene (500 mL) was heated under reflux in a Dean-Stark apparatus for 1.5 h. The toluene was then removed by rotary evaporation, and the residue dissolved in ether and washed, first with 10% aqueous sodium hydroxide and then with water. The organic layer was dried (Na2SO4) and evaporated, and allowed to crystallize by standing in Et2O overnight, giving 24.4 g (93%) of the title compound.
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