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General procedure for the synthesis of 5-aminothiophene-2-carbonitrile from 5-nitrothiophene-2-carbonitrile: 5-nitrothiophene-2-carbonitrile (1 g, 6.5 mmol) was suspended in methanol (30 mL), aqueous NH4Cl (30 mL containing 4.5 g, 65 mmol) was added, followed by activated zinc (4.2 g, 65 mmol). The reaction mixture was stirred for 0.5 h at room temperature. After completion of the reaction, the mixture was filtered through a short diatomaceous earth pad and the filtrate was concentrated. The concentrated residue was partitioned between ethyl acetate and water. The organic layer was separated and the aqueous layer was further extracted with ethyl acetate. All organic extracts were combined, washed sequentially with water and brine, dried over MgSO4 and concentrated to give 5-aminothiophene-2-carbonitrile as a yellow solid (0.7 g, 87% yield).

[1] Patent: US2011/130398, 2011, A1. Location in patent: Page/Page column 79; 80
[2] Patent: US6353006, 2002, B1. Location in patent: Page column 146