[C:1]([CH2:3][C:4]([O:6][CH3:7])=[O:5])#[N:2].[S:8]1CC(O)S[CH2:10][CH:9]1O.C(N(CC)CC)C>CCO>[NH2:2][C:1]1[S:8][CH:9]=[CH:10][C:3]=1[C:4]([O:6][CH3:7])=[O:5]A mixture of methyl cyanoacetate (3.25 g, 32.3 mmol), 1,4dithiane-2,5diol (5 g, 32.8 mmol), triethylamine (1 mL, 7.71 mmol) in EtOH (50 mL) is stirred at 40° C. for 1 h. The cooled solution is eluted through a silica plug with CH2Cl2 . The filtrate is stripped to dryness to give crude methyl 2-aminothiophene-3-carboxylate which is carried on to the next reaction. 1H NMR (DMSO) δ 7.26 (1H, s), 6.82 (1H, d, J=5.8 Hz), 6.28 (1H, d, J=5.8 Hz), 3.69 (3H, s)
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