[F:1][C:2]1[CH:7]=[C:6]([F:8])[CH:5]=[CH:4][C:3]=1[NH:9][S:10]([CH2:13][CH2:14][CH3:15])(=[O:12])=[O:11].C([N-]C(C)C)(C)C.[Li+].C([Li])CCC.C(NC(C)C)(C)C.CN(C)[CH:38]=[O:39]>O1CCCC1.O>[F:1][C:2]1[C:7]([CH:38]=[O:39])=[C:6]([F:8])[CH:5]=[CH:4][C:3]=1[NH:9][S:10]([CH2:13][CH2:14][CH3:15])(=[O:12])=[O:11]To propane-1-sulfonic acid (2,4-difluoro-phenyl)-amide (57, 1.5 g, 6.38 mmol) in tetrahydrofuran (10 mL) under an atmosphere of nitrogen, cooled in a −78° C. acetone/dry ice bath was added lithium diisopropylamide (0.80 M in tetrahydrofuran, 24 mL, freshly prepared from n-butyllithium and diisopropylamine). After 30 minutes, N,N-dimethyl-formamide (542 μL, 7.018 mmol) was added dropwise to the reaction. The reaction was stirred for 30 minutes at −78° C. and then allowed to warm to room temperature for 40 minutes. The reaction was poured into water and extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated and purified by silica gel column chromatography eluting with 5% ethyl acetate in hexane to give a light yellow solid (58, 300 mg, 18%). MS (ESI) [M−H+]−=262.3.
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