[CH3:1][O:2][C:3]1[CH:8]=[CH:7][C:6]([NH:9][S:10]([CH2:13][C:14]#[N:15])(=[O:12])=[O:11])=[CH:5][CH:4]=1.C(=O)([O-])[O-].[K+].[K+].Br[CH2:23][CH2:24]Br.Cl>CN(C)C=O.O>[CH3:1][O:2][C:3]1[CH:8]=[CH:7][C:6]([N:9]2[CH2:24][CH2:23][CH:13]([C:14]#[N:15])[S:10]2(=[O:12])=[O:11])=[CH:5][CH:4]=1
To a solution of the compound obtained in Step A (0.59 g) in dimethylformamide (40 ml) was added potassium carbonate (1.1 g). Then, a solution of 1,2-dibromoethane (0.59 g) in dimethylformamide (25 ml) was added dropwise at 55° C. The reaction mixture was then stirred at 55° C. for 2 hours, cooled to room temperature, poured into 15 ml water, and aqueous 2N hydrochloric acid was added to acidic pH. The aqueous layer was then extracted with dichloromethane, the combined organic layers washed two times with 2% aqueous hydrochloric acid, dried over sodium sulfate and concentrated in vacuo. Column chromatography (ethyl acetate/cyclohexane 7:3) afforded the title product as a beige solid (310 mg). 1HNMR (CDCl3, 400 MHz): 7.30 (d, 2H), 6.90 (d, 2H), 4.25 (m, 1H), (m, 1H), 3.70-3.90 (m, 5H), 2.95 (m, 1H), 2.80 (m, 1H).
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