[S:1]1[CH:5]=[CH:4][C:3]2[C:6](=[O:9])[CH2:7][CH2:8][C:2]1=2.[H-].[Na+].C([O:14][C:15]([C:17]1[CH:21]=[CH:20][O:19][CH:18]=1)=O)C.Cl>C1COCC1.C(OCC)(=O)C.O>[O:19]1[CH:20]=[CH:21][C:17]([C:15]([CH:7]2[CH2:8][C:2]3[S:1][CH:5]=[CH:4][C:3]=3[C:6]2=[O:9])=[O:14])=[CH:18]15,6-Dihydro-cyclopenta[b]thiophen-4-one in 40 mL of THF was treated with NaH (60 percent, 0.8 g, 36.25 mmol). After the addition of Furan-3-carboxylic acid ethyl ester, the reaction mixture was heated at 100° C. for 8 hr. The solution was cooled to room temperature and poured into water. The resulting mixture was acidified with concentrated HCl and was added with ethyl acetate (70 mL). The organic layer was collected, brined, dried over MgSO4(s), and concentrated under reduced pressure. The resultant precipitate was collected and recrystallized from ethanol to provide the corresponding 5-(Furan-3-carbonyl)-5,6-dihydro-cyclopenta[b]thiophen-4-one (0.9 g, 38 mmol) as brown solid in 27% yield.
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