N1C=CC=CC=1.[OH:7][CH2:8][CH2:9][NH:10][C:11](=[O:24])[O:12][CH2:13][C:14]1[CH:19]=[CH:18][C:17]([O:20][C:21](=[O:23])[CH3:22])=[CH:16][CH:15]=1>C(Cl)Cl.[O-2].[O-2].[O-2].[Cr+6]>[CH:8]([CH2:9][NH:10][C:11](=[O:24])[O:12][CH2:13][C:14]1[CH:19]=[CH:18][C:17]([O:20][C:21](=[O:23])[CH3:22])=[CH:16][CH:15]=1)=[O:7]A solution of pyridine (1.15 mL) in 20 mL of CH2Cl2 was cooled in an ice bath and chromium trioxide (711 mg) was added in one portion. The mixture was stirred at the same temperature for 5 min and at room temperature for 1 h. A solution of 62 (300 mg, 1.18 mmol) in 10 mL of CH2Cl2 was added in one portion and the mixture was stirred for 45 min at room temperature. The solution was decanted, diluted with 100 mL of CH2Cl2 and washed with aqueous NaHCO3 (2×75 mL), saturated NaCl (1×75 mL), dried over Na2SO4, filtered and concentrated in vacuo to give the crude aldehyde which was used without further purification. 1H NMR (400 MHz, CDCl3) δ 2.20 (s, 3H), 4.03 (s, 2H), 5.0 (s, 2H), 5.42 (broad s, 1H), 6.97 (d, J=8.5 Hz, 2H), 7.27 (d, J=8.4 Hz, 2H), 9.56 (s, 1H).
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