a) Synthesis of methyl 3-bromo-1H-pyrrole-2-carboxylate: methyl 3-bromo-1-(phenylsulfonyl)-1H-pyrrole-2-carboxylate (6.59 g, 19.2 mmol) was dissolved in 132 mL of methanol. Sodium methanolate (1.55 g, 28.7 mmol) was added and the reaction mixture was stirred for 4 hours at room temperature. After completion of the reaction, the solvent was removed by evaporation and the residue was extracted by partitioning with saturated aqueous ammonium chloride solution and ethyl acetate. The organic layer was washed sequentially with water and brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. Purification by fast column chromatography (eluent: 0% to 30% hexane/ethyl acetate gradient) afforded 3.32 g (85% yield) of the target product methyl 3-bromopyrrole-2-carboxylate. Low resolution mass spectrometry (LRMS) showed m/z: 203,205 ([M+1]+).
