C[CH:2]1[CH2:5][CH2:4][C:3]1([C:9]1[CH:14]=[CH:13][C:12]([Cl:15])=[CH:11][CH:10]=1)[C:6]([OH:8])=[O:7].S(=O)(=O)(O)O.[C:21](=O)([O-])[O-].[Na+].[Na+]>CO>[Cl:15][C:12]1[CH:13]=[CH:14][C:9]([C:3]2([C:6]([O:8][CH3:21])=[O:7])[CH2:4][CH2:5][CH2:2]2)=[CH:10][CH:11]=1To a solution of methyl 1-(4-chlorophenyl)cyclobutanecarboxylic acid (5.0 g, 23.73 mmol) in anhydrous methanol was added 1 mL of the concentration of sulfuric acid. The mixture was refluxed for overnight. The mixture was neutralized to pH 4-5 with sodium carbonate. The solvent was evaporated. The residue was dissolved in ethyl acetate (50 mL), washed with brine (3×10 mL), dried over MgSO4. The crude product was used for the next reaction without further purification.
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