[I:1][C:2]1[C:10]2[O:9][C:8](=[O:11])[NH:7][C:6]=2[CH:5]=[C:4]([N+:12]([O-:14])=[O:13])[CH:3]=1.C(N(CC)C(C)C)(C)C.[CH3:24][Si:25]([CH3:32])([CH3:31])[CH2:26][CH2:27][O:28][CH2:29]Cl>CN(C)C=O.C(OCC)(=O)C>[I:1][C:2]1[C:10]2[O:9][C:8](=[O:11])[N:7]([CH2:29][O:28][CH2:27][CH2:26][Si:25]([CH3:32])([CH3:31])[CH3:24])[C:6]=2[CH:5]=[C:4]([N+:12]([O-:14])=[O:13])[CH:3]=1A solution of 7-iodo-5-nitro-1,3-benzoxazol-2(3H)-one (0.76 g, 2.5 mmol) in N,N-dimethylformamide (5 mL) at 0° C. was treated with N,N-diisopropylethylamine (0.65 mL, 3.7 mmol) followed by [β-(trimethylsilyl)ethoxy]methyl chloride (0.61 mL, 3.5 mmol) dropwise and stirred at 20° C. for 1 h. The reaction mixture was diluted with ethyl acetate (100 mL) and washed with 0.5 M HCl (50 mL), brine (25 mL), dried over anhydrous sodium sulfate, filtered, and concentrated to a crude oil. This material was purified by flash column chromatography to give the desired product (0.93 g, 86%) as a yellow oil.
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