[OH:1][C:2]1[CH:11]=[C:10]([OH:12])[CH:9]=[C:8]2[C:3]=1[C:4](=[S:14])[CH:5]=[C:6]([CH3:13])[O:7]2.C(=O)([O-])[O-].[K+].[K+].[CH:21](I)([CH3:23])[CH3:22].[CH3:25]I>O.CC(C)=O>[CH:21]([O:12][C:10]1[CH:9]=[C:8]2[C:3]([C:4](=[S:14])[CH:5]=[C:6]([CH3:13])[O:7]2)=[C:2]([O:1][CH3:25])[CH:11]=1)([CH3:23])[CH3:22]
A mixture consisting of 354 mg (1.58 mmol) of 5,7-dihydroxy-2-methylthiochromone, 1.09 g (7.90 mmol) potassium carbonate, 0.79 ml (7.90 mmol) isopropyl iodide, and 20 ml acetone was refluxed overnight. Then, 2.95 ml (47.4 mmol) methyl iodide was added, and the mixture was further refluxed overnight. Water was added to the solution thus reacted. The product was extracted twice with ethyl acetate. The organic layer was washed with brine and dried over anhydrous sodium sulfate. The solvent was distilled out under reduced pressure. The resulting crude product was purified by flash column chromatography (hexane:ethyl acetate=1:3-1:6), whereby 228 mg of 7-isopropoxy-5-methoxy-2-methylthiochromone was obtained (yield: 52%).
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