[Br:1][C:2]1[CH:10]=[C:9]2[C:5]([CH:6]=[C:7]([CH2:11][OH:12])[NH:8]2)=[CH:4][CH:3]=1.[Si:13](Cl)([C:16]([CH3:19])([CH3:18])[CH3:17])([CH3:15])[CH3:14].N1C=CN=C1>CN(C=O)C>[Br:1][C:2]1[CH:10]=[C:9]2[C:5]([CH:6]=[C:7]([CH2:11][O:12][Si:13]([C:16]([CH3:19])([CH3:18])[CH3:17])([CH3:15])[CH3:14])[NH:8]2)=[CH:4][CH:3]=1The product from Step 1 (1.87 g, 8.3 mmol) was combined with t-butyldimethylsilyl chloride (1.38 g, 9.1 mmol) and imidazole (734 mg, 10.8 mmol) in DMF (15 mL). The mixture was stirred 2 h at room temperature. The solvents were removed by rotary evaporation under reduced pressure. The resulting residue was partitioned in EtOAc and saturated aqueous ammonium chloride. The organic layer was washed with brine, dried over Na2SO4, concentrated and chromatographed on silica gel (0-15% EtOAC in hexanes) to give the product (2.7 g, 96%). LC-MS 340.2, 342.2 [M+H]+, RT 1.62 min.
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