[F:1]C1C=CC(CC2SC=CC=2)=CC=1.II.OS(O)(=O)=O.F[C:22]1[CH:34]=C[C:25]([CH2:26][C:27]2[S:31][C:30]([I:32])=[CH:29][CH:28]=2)=[CH:24][CH:23]=1>[Cl-].[Na+].O.C(O)(=O)C.C(OCC)(=O)C>[F:1][C:23]1[CH:22]=[CH:34][C:26]([C:27]2[S:31][C:30]([I:32])=[CH:29][CH:28]=2)=[CH:25][CH:24]=1A mixture of 2-(4-fluorobenzyl)thiophene (8.4 g, 43.7 mmol), HIO3 (1.86 g, 10.6 mmol), I2 (4.86 g, 19.2 mmol), ethyl acetate (66 ml), acetic acid (7.7 ml) and conc. H2SO4 (0.79 ml) was heated at 35° C. overnight (GC-MS showed that all the starting material is converted to 5-(4-fluorobenzyl)-2-iodothiophene). To the reaction mixture was added brine solution (33 ml), the organic layer was separated and washed with sodium hydroxide/sodium thiosulfate solution (33 ml) (prepared from 2.3 g of NaOH, 3.3 g of Na2S2O3 in 27 ml of H2O), followed by 10% of NaHCO3 solution (33 ml). The organic layer was concentrated to yield 13.9 g of 5-(4-fluorophenyl)-2-iodothiophene.
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