[CH3:1][C:2]1[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][C:5]=2[O:4][C:3]=1[C:11](OCC)=[O:12].C1(C)C=CC=CC=1.[H-].C([Al+]CC(C)C)C(C)C.Cl.CC(OI1(OC(C)=O)(OC(C)=O)OC(=O)C2C=CC=CC1=2)=O.S([O-])([O-])=O.[Na+].[Na+]>O1CCCC1.ClCCl>[CH3:1][C:2]1[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][C:5]=2[O:4][C:3]=1[CH:11]=[O:12]To a solution (40 mL) of ethyl 3-methyl-1-benzofuran-2-carboxylate (2.00 g) in tetrahydrofuran was added dropwise 1.5M diisobutylaluminum hydride toluene solution (19.6 mL) at 0° C., and the mixture was stirred for 2 hr. 1N Hydrochloric acid was added to quench the reaction, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure to give a white solid. To a solution (40 mL) of the obtained solid in dichloromethane was added Dess-Martin periodinane (4.96 g) at 0° C., and the mixture was stirred at room temperature overnight. Saturated sodium sulfite aqueous solution was added to quench the reaction, and the mixture was extracted with ethyl acetate. The extract was washed with saturated aqueous sodium hydrogen carbonate solution and saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate:hexane=1:9, volume ratio) to give the title object compound (753 mg, 48%) as a white solid.
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