The general procedure for the synthesis of methyl 1-amino-1H-pyrrole-2-carboxylate from methyl 2-pyrrolecarboxylate is as follows:
Step 1: Methyl 2-pyrrolecarboxylate (8.0 g, 63.9 mmol) was slowly added to a suspension of NaH (60%, 4.1 g, 102.2 mmol) in dimethylformamide (120 mL) at 0 °C and under nitrogen protection. After stirring for 1 h, a solution of dimethylformamide (30 mL) of 2,4-dinitroaniline (19.1 g, 95.9 mmol) was added dropwise for a controlled time of 30 min. The reaction mixture was continued to be stirred at 0 °C for 2.5 hours. Upon completion of the reaction, the reaction was quenched by slow addition of saturated aqueous sodium thiosulfate solution. The reaction mixture was extracted with ethyl acetate and the organic layer was washed with 10% aqueous lithium chloride solution, dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated and the resulting brown residue was purified by silica gel column chromatography (eluent: 10% hexane solution of ethyl acetate) to afford methyl 1-amino-1H-pyrrole-2-carboxylate as an oil (7.5 g, 53.5 mmol, 84% yield).
1H NMR (400 MHz, CDCl3): δ 6.96 (t, J = 2.4 Hz, 1H), 6.83 (dd, J = 4.4 Hz, 2.0 Hz, 1H), 6.02 (dd, J = 4.4 Hz, 2.8 Hz, 1H), 5.54 (br s, 2H), 3.83 (s, 3H).
