[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([Cl:8])=[CH:4][C:3]=1[CH2:9][CH2:10][CH2:11][CH2:12][C:13]([O:15]C)=[O:14].[Li+].[OH-]>O1CCCC1.CO>[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([Cl:8])=[CH:4][C:3]=1[CH2:9][CH2:10][CH2:11][CH2:12][C:13]([OH:15])=[O:14]Methyl 5-(2,5-dichlorophenyl)pentanoate (1.10 g, 4.2 mmol) was dissolved in 20 ml tetrahydrofuran and 7 ml methanol. 1N LiOH (12 ml) was added dropwise and the reaction was stirred at room temperature for 2 days. The reaction was worked-up by acidification with 2N HCl and removal of most of the tetrahydrofuran and methanol on a rotary evaporator followed by extraction of the aqueous residue with ethyl acetate. The organic phase was washed with water and saturated brine, dried over anhydrous sodium sulfate and concentrated to a residue. Flash chromatography (silica gel; hexane/toluene (19/1) with 1% acetic acid) of the residue gave 725 mg (70%) of a white solid. 1H NMR (200 MHz, CD3OD) delta=7.30-7.26 (m, H3, H6), 7.14 (dd, J=2.6, 8.4 Hz, H4), 2.70 (t, J=7.2 Hz, Ar-CH2 --), 2.30 (t, J=7.0 Hz, --CH2 --COOH), 1.67-1.57 (m, --CH2 --CH2 --CH2 --CH2 --); MS (EI, m/z (relative intensity)) 248 (29), 246 (M+·, 45), 167 (31), 165 (97), 161 (66), 159 (100); exact mass calculated for C11H12Cl2 O2, [M]+· 246.0213, found 246.0210.
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