[S:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[C:6]([O:8][CH3:9])=[O:7].II.FC(F)(F)C(O[I:17](C1C=CC=CC=1)OC(=O)C(F)(F)F)=O.C(=O)(O)[O-].[Na+].S([O-])([O-])(=O)=S.[Na+].[Na+]>C(Cl)Cl.C(OCC)(=O)C>[I:17][C:5]1[S:1][C:2]([C:6]([O:8][CH3:9])=[O:7])=[CH:3][CH:4]=1
To a stirred solution of methyl thiophene-2-carboxylate (0.46 mL, 4 mmol) in anhydrous methylene chloride (5 mL) was added iodine (510 mg, 2 mmol) followed by [bis(trifluoroacetoxy)iodo]benzene (900 mg, 2.1 mmol). The reaction mixture was stirred at RT for 1.5 hr before saturated aqueous sodium bicarbonate solution (10 mL) and saturated aqueous sodium thiosulfate solution (2 mL) were added. The mixture was then stirred at RT for 20 min. The aqueous layer was separated and extracted with methylene chloride (2×1 mL). The combined organic solutions were dried (Na2SO4). Silica gel flash chromatography (0-100% ethyl acetate in hexanes) gave methyl 5-iodothiophene-2-carboxylate (500 mg, 1.9 mmol, 47% yield) as a solid.
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