Br[C:2]1[C:6]([Br:7])=[CH:5][S:4][C:3]=1[N+:8]([O-:10])=[O:9].[NH:11]1[CH:15]=[CH:14][N:13]=[N:12]1.C(=O)(O)[O-].[K+]>CN(C=O)C>[Br:7][C:6]1[C:2]([N:12]2[N:13]=[CH:14][CH:15]=[N:11]2)=[C:3]([N+:8]([O-:10])=[O:9])[S:4][CH:5]=1A mixture of 3,4-dibromo-2-nitrothiophene (1.5 g, 5.23 mmol), 1H-1,2,3-triazole (0.30 mL, 5.18 mmol) and potassium bicarbonate (0.54 g, 5.36 mmol) in DMF (13 mL) were stirred in an oil bath set at 110° C. under condenser with N2 (g) inlet for 1 h. The reaction mixture was quenched with H2O and extracted with ethyl acetate. The organic phase was collected, dried (sodium sulfate), filtered and concentrated under reduced pressure. Purification by flash chromatography (silica, 30:70 ethyl acetate/hexane) gave the regio-isomer nitro intermediate of interest (0.518 g, 36%). Retention time (min)=1.950, method [4], MS(ESI) 276.9 (M+H).
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