2818-07-7

39687-95-1

922-67-8

2818-07-7

Step A: To a solution of dioxane (200 mL) containing cuprous oxide (832 mg, 5.9 mmol) and 1,10-phenanthroline (2.14 g, 11.89 mmol) was added sequentially methyl propargylate (10 g, 118.9 mmol) and methyl isocyanoacetate (8.95 g, 98.6 mmol) under nitrogen protection. The reaction mixture was heated with stirring at 100 °C for 2 hours. Upon completion of the reaction, the mixture was cooled to room temperature and filtered through a diatomaceous earth pad to remove the solid catalyst. The filtrate was concentrated under reduced pressure to remove the solvent and the resulting crude product was purified by silica gel column chromatography using a solvent mixture of ethyl acetate-hexane as eluent. The target fraction was collected and concentrated to give dimethyl 1H-pyrrole-2,4-dicarboxylate (8.6 g, 48% yield) as a white solid. The product was confirmed by nuclear magnetic resonance hydrogen spectroscopy (1H NMR, 300 MHz, DMSO-d6): δ 12.55 (s, 1H), 7.60 (s, 1H), 7.10 (s, 1H), 3.92 (s, 3H), 3.90 (s, 3H); liquid chromatography-mass spectrometry (LC-MS, ESI) showed the molecular ion peak m/z 184 ([M+H] +).