[CH3:1][O:2][C:3]1[CH:8]=[CH:7][C:6]([CH:9]2[CH2:14][C:13](=[O:15])[CH2:12][C:11](=[O:16])[CH2:10]2)=[CH:5][CH:4]=1.[Br-].C[S+](C)[CH:20]=[C:21]=[CH2:22].[O-]CC.[Na+]>C(O)C>[CH3:1][O:2][C:3]1[CH:4]=[CH:5][C:6]([CH:9]2[CH2:10][C:11](=[O:16])[C:12]3[C:21]([CH3:22])=[CH:20][O:15][C:13]=3[CH2:14]2)=[CH:7][CH:8]=1A mixture of 5-(4-methoxyphenyl)cyclohexane-1,3-dione (0.95 g), dimethyl-1,2-propadien-1-yl sulfonium bromide (1.5 g), sodium ethoxide (0.31 g) and ethanol (10 ml) was refluxed for 5 hours. Under reduced pressure, the solvent was evaporated, and the residue was dissolved in ethyl acetate. The solution was washed with water and saturated brine, dried with magnesium sulfate and concentrated under reduced pressure. The residue was dissolved in toluene (20 ml), and to the solution was added p-toluenesulfonic acid(0.85 g). The mixture was stirred at room temperature for 1 hour. To the mixture was added ethyl acetate, and the mixture was washed with sodium hydrogen carbonate solution, water and saturated brine, dried with magnesium sulfate and concentrated under reduced pressure. The residue was purified with silica gel column chromatography (EtOAc/hexane) to give colorless crystals of 6-(4-methoxyphenyl)-3-methyl-4,5,6,7-tetrahydrobenzofuran-4-one (0.14 g).
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