[CH3:1][O:2][C:3](=[O:13])[C:4]1[CH:9]=[CH:8][C:7]([CH:10]=[O:11])=[CH:6][C:5]=1[Br:12].[CH2:14]([OH:17])[CH2:15]O.[C:18]1(C)C=CC(S(O)(=O)=O)=CC=1>C1COCC1>[CH3:1][O:2][C:3](=[O:13])[C:4]1[CH:9]=[CH:8][C:7]([CH:10]2[O:17][CH2:14][CH:15]=[CH:18][O:11]2)=[CH:6][C:5]=1[Br:12]The mixture of 2-bromo-4-formyl-benzoic acid methyl ester (440 mg, 1.8 mmol), ethylene glycol (1.1 g, 18 mmol) and p-toluene sulfonic acid (30 mg) in THF (10 mL) is stirred at room temperature overnight. The reaction mixture is partitioned between EtOAc (30 mL) and water (30 mL). The organic phase is washed with brine (30 mL), dried (Na2SO4), filtered, and concentrated under reduced pressure to a residue. The residue is purified by flash chromatography to afford the title compound as syrup (380 mg, 73%). LC-ES/MS m/e 287.0 (M+1).
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