[Br:1][C:2]1[C:9]([F:10])=[CH:8][C:5]([CH:6]=O)=[C:4]([F:11])[CH:3]=1.[CH3:12][C:13]1(C)[O:18]C(=O)CC(=O)[O:14]1.Cl>C(N(CC)CC)C>[Br:1][C:2]1[C:9]([F:10])=[CH:8][C:5]([CH:6]=[CH:12][C:13]([OH:18])=[O:14])=[C:4]([F:11])[CH:3]=1To a solution of 4-bromo-2,5-difluorobenzaldehyde (15.0 g) in triethylamine formiate (80 mL) at room temperature was added 2,2-dimethyl-1,3-dioxane-4,6-dione (9.77 g). After being stirred for 1 h, the mixture was heated at 95° C. with stirring for 15 hours. After cooling down, ice water was added. The mixture was adjusted to pH ˜1 with HCl (6 M) and then extracted with ethyl acetate (200 mL×3). The organic phase was washed with brine (50 mL) and dried over Na2SO4. The solvent was removed under reduced pressure and the residue was purified by silica gel column chromatography eluting with DCM/petroleum ether (7:1) to give the subtitle compound as a white solid. MS ESI+: m/z=263 [M+H]+.
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