1,2-Dibromoethane → methyl 4-bromo-1-(2-bromoethyl)-1H-pyrrole-2-carboxylate

To a solution of methyl 4-bromo-1H-pyrrole-2-carboxylate (Combi-Blocks, San Diego, Calif.; 5.15 g, 25.2 mmol) in DMF (25 mL) at 0° C. was added NaH (60% wt. in mineral oil, 1.81 g, 45.4 mmol) and the resulting mixture was stirred at 0° C. for 15 min. 1,2dibromoethane (4.79 ml, 55.5 mmol) was added and the reaction was stirred at RT for 10 min, then heated in an oil bath at 70° C. for 2 h. After cooling to RT, it was treated with ice cold NH4Cl solution (10 mL), extracted with 2×75 mL of EtOAc. The combined organic layers were washed with brine, dried over Na2SO4 and concentrated. Purification on a silica gel column (15-35% EtOAc in hexanes) furnished methyl 4-bromo-1-(2-bromoethyl)-1H-pyrrole-2-carboxylate (3.60 g, 11.58 mmol, 46% yield) as an off-white amorphous solid. 1H NMR (400 MHz, DMSO-d6) δ ppm 7.41 (1H, d, J=2.0 Hz), 6.92 (1H, d, J=1.8 Hz), 4.65 (2H, t, J=6.5 Hz), 3.75 (5H, m). m/z (ESI, +ve) 311.9 (M+H)+.