O[CH2:2][C:3]1[CH:4]=[C:5]([C:13]([O:15][CH3:16])=[O:14])[CH:6]=[C:7]([CH:12]=1)[C:8]([O:10][CH3:11])=[O:9].C(N(S(F)(F)[F:23])CC)C>C(Cl)Cl>[F:23][CH2:2][C:3]1[CH:4]=[C:5]([C:13]([O:15][CH3:16])=[O:14])[CH:6]=[C:7]([CH:12]=1)[C:8]([O:10][CH3:11])=[O:9]Under Ar atmosphere, with ice-cooled, to a solution of dimethyl 5-hydroxymethylisophthalate (32) (3.36 g, 15.0 mmol) in CH2Cl2 (150 mL, 0.1 M solution) was slowly added dropwise (diethylamino)sulfur trifluoride (4.00 mL, 30.5 mmol), and stirred for 2 hours at a room temperature. TLC was used to confirm the progress of the reaction. Then, the reaction was quenched with MeOH (150 mL). The solvent was removed under reduced pressure. The residue was subjected to extraction with EtOAc and a saturated sodium hydrogen carbonate aqueous solution (three times). The organic layer was washed with a saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, and evaporated under reduced pressure to remove the solvent. The residue was purified by neutral silica gel column chromatography (hexane:EtOAc=10:1) to isolate dimethyl 5-fluoromethylisophthalate (33) (2.57 g, 78%) as white crystals.
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