[C:1]([O:5][C:6]([NH:8][C:9]1[CH:13]=[CH:12][S:11][CH:10]=1)=[O:7])([CH3:4])([CH3:3])[CH3:2].CC([O-])=O.[Na+].[I:19]Cl>C(O)(=O)C>[I:19][C:10]1[S:11][CH:12]=[CH:13][C:9]=1[NH:8][C:6]([O:5][C:1]([CH3:4])([CH3:2])[CH3:3])=[O:7]A vial was charged with 199 mg (1.0 mmol) 3-(tert-butoxycarbonylamino)thiophene, 164 mg (2.0 mmol) NaOAc, 4.0 mL HOAc, and a stir bar. The mixture was stirred at room temperature, giving a homogeneous solution “A”. A second vial was charged with 162 mg (1.0 mmol) iodine monochloride and 2.0 mL glacial acetic acid. The second mixture was swirled at room temperature. This second homogeneous solution “B” was added to solution “A” dropwise over three minutes. A white solid began to precipitate immediately. After the addition, the mixture was allowed to stand overnight, at which time the white solid had separated from the brown supernatant. With stirring, 200 uL sat. Na2S2O3/H2O was added, decolorizing the mixture from brown to yellow. 10 mL water was added, and then the mixture was evaporated, affording a semi-solid light brown residue. The residue was partitioned between EtOAc and H2O, and the separated EtOAc phase was washed (sat. NaHCO3, then sat. NaCl). The EtOAc phase was filtered, and concentrated to give 262 mg (81%) of the title compound as light brown crystals. 1H NMR (CDCl3, 300 MHz) δ 7.49 (bs, 1H), 7.45 (d, J=5.4 Hz, 1H), 6.50 (bs, 1H), 1.54 (s, 9H). Method [5]: rt=1.40 min; m/z=269.9 (MH+ minus isobutylene).
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