[CH3:1][O:2][C:3]([C:5]1([C:8]2[CH:13]=[CH:12][C:11]([O:14]C)=[C:10]([N+:16]([O-:18])=[O:17])[CH:9]=2)[CH2:7][CH2:6]1)=[O:4].B(Br)(Br)Br.O>C(Cl)Cl>[CH3:1][O:2][C:3]([C:5]1([C:8]2[CH:13]=[CH:12][C:11]([OH:14])=[C:10]([N+:16]([O-:18])=[O:17])[CH:9]=2)[CH2:6][CH2:7]1)=[O:4]To a solution of 1-(4-methoxy-3-nitro-phenyl)-cyclopropane-carboxylic acid methyl ester (10.0 g, 39.8 mmol) in CH2Cl2 (100 mL) was added BBr3 (12.0 g, 47.8 mmol) at −70° C. The mixture was stirred at −70° C. for 1 hour, then allowed to warm to −0.30° C. and stirred at this temperature for 3 hours. Water (50 mL) was added dropwise at −20° C., and the resulting mixture was allowed to warm room temperature before it was extracted with EtOAc (200 mL×3). The combined organic layers were dried over anhydrous Na2SO4 and evaporated under vacuum to give the crude product, which was purified by column chromatography on silica gel (petroleum ether/ethyl acetate 15:1) to afford 1-(4-hydroxy-3-nitro-phenyl)-cyclopropanecarboxylic acid methyl ester (8.3 g, 78%). 1H NMR (CDCl3, 400 MHz) δ 10.5 (s, 1H), 8.05 (d, J=2.4 Hz, 1H), 7.59 (dd, J 2.0, 8.8 Hz, 1H), 7.11 (d, J=8.4 Hz, 1H), 3.64 (s, 3H), 1.68-1.64 (m, 2H), 1.20-1.15 (m, 2H).
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