[CH3:1][O:2][C:3](=[O:15])[C:4](=[N+]=[N-])[C:5]1[CH:10]=[CH:9][C:8]([Cl:11])=[C:7]([Cl:12])[CH:6]=1.ClCCl.[CH:19]1([OH:24])[CH2:23][CH2:22][CH2:21][CH2:20]1>CC(O)=O.CC(O)=O.CC(O)=O.CC(O)=O.[Rh].[Rh].O>[CH3:1][O:2][C:3](=[O:15])[CH:4]([O:24][CH:19]1[CH2:23][CH2:22][CH2:21][CH2:20]1)[C:5]1[CH:10]=[CH:9][C:8]([Cl:11])=[C:7]([Cl:12])[CH:6]=1In a dry flask under argon was placed diazo-(3,4-dichloro-phenyl)-acetic acid methyl ester (350 mg 1.4 mmol) to which was added dichloromethane (10 mL) and cyclopentanol (0.25 mL, 2.8 mmol). The solution was stirred at 25° C. and as rhodium (II) acetate dimer (13 mg, 0.028 mmol) was added, the immediate evolution of gas was noted and the color changed from bright yellow to an aquagreen color. After the solution was stirred at 25° C. for 1 h, it was then poured into water and the layers were separated. The aqueous layer was washed with dichloromethane (3×15 mL) and the organic layers were then combined, dried over sodium sulfate and concentrated in vacuo. The residual material was purified by flash chromatography (Merck Silica gel 60, 230-400 mesh, 95/5 hexanes/ethyl acetate) to give rac-cyclopentyloxy-(3,4-dichloro-phenyl)-acetic acid methyl ester (273 mg, 64% yield) as a clear colorless oil: EI-HRMS m/e calcd for C14H16Cl2O3 (M+) 302.0477, found 302.0484.
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