[NH2:1][C:2]1[S:3][CH:4]=[CH:5][C:6]=1[C:7]([O:9]C)=O.[CH:11]([NH2:13])=O>O>[N:1]1[C:2]2[S:3][CH:4]=[CH:5][C:6]=2[C:7](=[O:9])[NH:13][CH:11]=1Methyl 2-aminothiophene-3-carboxylate (10 g, 64 mmol) was charged with formamide (50 mL). The reaction was heated at 190° C. under nitrogen for 3 hours. The solution was cooled to room temperature. The slurry was poured into 125 mL of water and extracted with chloroform:isopropyl alcohol mixture (2 times). The solution was concentrated and triturated to afford the title compound (2.25 g, 23%).
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