[Br:1][CH2:2][C:3]1[C:4]([C:20]2[CH:25]=[CH:24][C:23]([S:26](=[O:29])(=[O:28])[NH2:27])=[CH:22][CH:21]=2)=[C:5]([C:15]([O:17][CH2:18][CH3:19])=[O:16])[S:6][C:7]=1[C:8]1[CH:13]=[CH:12][C:11]([Cl:14])=[CH:10][CH:9]=1.[CH3:30][N:31]([CH:33]=O)[CH3:32].COC(OC)N(C)C>C(OCC)(=O)C>[Br:1][CH2:2][C:3]1[C:4]([C:20]2[CH:25]=[CH:24][C:23]([S:26](=[O:28])(=[O:29])[N:27]=[CH:30][N:31]([CH3:33])[CH3:32])=[CH:22][CH:21]=2)=[C:5]([C:15]([O:17][CH2:18][CH3:19])=[O:16])[S:6][C:7]=1[C:8]1[CH:9]=[CH:10][C:11]([Cl:14])=[CH:12][CH:13]=1To a stirred suspension of Ethyl 4-(bromomethyl)-5-(4-chlorophenyl)-3-(4-sulfamoylphenyl)thiophene-2-carboxylate (compound 35a, 2.7 g, 5.24 mmol) in ethyl acetate (30 ml) were added DMF (1.91 g, 2.01 ml, 26.2 mmol) and N,N-Dimethylformamide dimethyl acetal (DMF-acetal) (0.69 g, 0.76 ml, 5.76 mmol) under a nitrogen atmosphere at room temperature (about 25° C.). The reaction mixture was then stirred at room temperature (about 25° C.) for 4 hr. The progress of the reaction was monitored by TLC. The reaction mixture was concentrated under reduced pressure to obtain 2.9 g of crude product. The crude product so obtained was then purified by column chromatography over silica gel (100-200 mesh) using 1.5% methanol in DCM as an eluent to obtain the title compound (2.2 g, 73.82%).
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