[CH2:1]([S:3]([C:6]1[CH:11]=[CH:10][C:9]([OH:12])=[C:8]([NH2:13])[CH:7]=1)(=[O:5])=[O:4])[CH3:2].C(=O)([O-])[O-].[Cs+].[Cs+].Br[CH2:21][C:22](Br)=[O:23]>CN(C=O)C>[CH2:1]([S:3]([C:6]1[CH:11]=[CH:10][C:9]2[O:12][CH2:21][C:22](=[O:23])[NH:13][C:8]=2[CH:7]=1)(=[O:5])=[O:4])[CH3:2]Commercially available 4-ethylsulfonyl-2-aminophenol (4.02 g, 20 mmol) was dissolved in DMF (30 mL) and mixed with cesium carbonate (6.5 g, 20 mmol). The reaction mixture was cooled to 0° C. and bromoacetyl bromide (4.0 g, 20 mmol) in DMF (5 mL) was added dropwise. The reaction was stirred overnight at room temperature. After aqueous work up, the product was purified by silica gel chromatography with methanol/dichloromethane to give the product as an orange solid, 1.7 g (35%).
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