Dimethylformamide dimethyl acetal → 3-(Dimethylamino-methyleneamino)-thiophene-2-carboxylic acid methyl ester

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A mixture of methyl 3-amino-2-thiophenecarboxylate (1.572 g, 10 mmol) in 5 ml of N,N-dimethylformamide dimethyl acetal (DMF-DMA) was heated at reflux for 2 h and then allowed to cool to room temperature. The resulting mixture was evaporated to give 2.019 g (95%) of orange residue. 1H NMR (400 MHz, DMSO-d6) δ 7.75 (s, 1H), 7.63 (d, J=5.6 Hz, 1H), 6.81 (d, J=5.2 Hz, 1H), 3.67 (m, 3H), 3.00 (s, 3H), 2.93 (s, 3H); LC-MS (ESI) m/z 213.1 (M+1).

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