934-07-6

1193-62-0

934-07-6

Synthesis of 5-bromo-1H-pyrrole-2-carboxylic acid methyl ester (53): 1H-pyrrole-2-carboxylic acid methyl ester (52; 10 g, 80 mmol) was dissolved in a solvent mixture of 800 mL tetrahydrofuran (THF) and 400 mL methanol (MeOH). The reaction mixture was cooled to 0 °C. N-bromosuccinimide (NBS; 15 g, 8.4 mmol) was added in 5 additions in batches over 1.5 hours. After addition, the reaction mixture was continued to be stirred at 0 °C for 2 hours. Upon completion of the reaction, the reaction mixture was concentrated and purified by silica gel column chromatography (eluent: 2% ethyl acetate/petroleum ether) to afford 4.3 g of 5-bromo-1H-pyrrole-2-carboxylic acid methyl ester 53 as a white solid in 26% yield.The LCMS analysis resulted in: m/z 206.0 [M + H] and a retention time t R = 1.50 min.