2,2-Dimethyl-4-oxo-tetrahydro-thiopyran-3-carboxylic acid methyl ester → 2,2-Dimethyltetrahydro-4h-thiopyran-4-one

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Reaction Steps

The mixture of 6,6-Dimethyl-4-oxo-tetrahydro-thiopyran-3-carboxylic acid methyl ester and 2,2-Dimethyl-4-oxo-tetrahydro-thiopyran-3-carboxylic acid methyl ester (42 g) in 10% aq. H2SO4 solution (1000 mL) was heated at reflux for 70 h. Then the mixture was extracted with Et2O (3×300 mL), the combined organic layer was washed with sat. NaHCO3 (120 mL) and brine (120 mL), dried over Na2SO4 and evaporated under vacuum to give the title compound as a white solid (5.3 g, 17.7%, two steps).

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