[O:1]1[CH:5]=[CH:4][N:3]=[C:2]1[C:6]1[CH:11]=[CH:10][C:9]([OH:12])=[CH:8][CH:7]=1.C([O-])([O-])=O.[K+].[K+].F[C:20]1[CH:27]=[CH:26][C:23]([CH:24]=[O:25])=[CH:22][CH:21]=1.C([O-])(O)=O.[Na+]>CN(C=O)C>[O:1]1[CH:5]=[CH:4][N:3]=[C:2]1[C:6]1[CH:11]=[CH:10][C:9]([O:12][C:20]2[CH:27]=[CH:26][C:23]([CH:24]=[O:25])=[CH:22][CH:21]=2)=[CH:8][CH:7]=1
To a solution of 4-(2-oxazolyl)phenol (4.1 g, 25.44 mmol) in DMF (98 ml), K2CO3 (3.52 g, 25.44 mmol, 1 equiv.) was added. The reaction was stirred at ambient temperature for 30 min. Then, 4-fluorobenzaldehyde (2.73 mL, 25.44 mmol, 1 equiv., Aldrich # 12,837-6) was added and stirring was continued at 150° C. for 4 hours. After cooling, saturated NaHCO3 was added to the reaction mixture. The reaction mixture was extracted with ethyl acetate. The organic layer was washed with brine, dried over Na2SO4, and concentrated under reduced pressure. Flashmaster chromatography on 50 g of silica gel using a gradient of 100% hexane→50% hexane+50% ethyl acetate gave 6.4 g of 4-[4-(2-oxazolyl)phenoxy]benzaldehyde still containing 20 mol % DMF. Further drying led to the pure product (6.05 g; 90% th.; 148% pract.); 1H NMR (CDCl3) δ 9.95 (s, 1H), 8.09 (d, 2H), 7.89 (d, 2H), 7.72 (d, 1H), 7.24 (d, 1H), 7.16 (d, 2H), 7.13 (d, 2H) ppm.
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