[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].CN(C=O)C>O>[OH:1][C:2]1[CH:11]=[C:10]([O:12][CH:21]([CH3:23])[CH3:22])[CH:9]=[C:8]2[C:3]=1[C:4](=[S:14])[CH:5]=[C:6]([CH3:13])[O:7]2
A mixture consisting of 6.88 g (30.35 mmol) 5,7-dihydroxy-2-methylthiochromone, 12.56 g (91.05 mmol) potassium carbonate, 6.07 ml (60.70 mmol) isopropyl iodide, and 150 ml DMF was stirred at 60° C. for 30 min. Subsequently, water was added to the solution. 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=4:1), whereby 6.71 g of 5-hydroxy-7-isopropoxy-2-methylthiochromone was obtained (yield: 83%).
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