Methyl iodide → ethyl 5-bromo-1,4-dimethyl-1H-pyrrole-3-carboxylate

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Reaction Steps

To a solution of ethyl 4-methyl-3-pyrrolecarboxylate (1.57 g, 10 mmol) in anhyd THF (30 mL) cooled to −78° C. was added NBS (1.9 g, 10 mmol). After stirring 1 h at −30° C., the reaction mixture was concentrated under reduced pressure. The residue was purified by column chromatography, eluting with EtOAc-Hex (0:100 to 30:70), to yield ethyl 5-bromo-4-methyl-1H-pyrrole-3-carboxylate (2.0, 86%) as a white solid. 1H-NMR (CDCl3): δ 8.54 (1H, brs), 7.38 (1H, d), 4.27 (2H, q), 2.24 (3H, s), 1.33 (3H, t). To a solution of ethyl 5-bromo-4-methyl-1H-pyrrole-3-carboxylate (2.0 g, 8.6 mmol) in anhyd DMF (30 mL) at 0° C. was added portionwise NaH (60% in mineral oil, 705 mg, 17.6 mmol) under nitrogen. After 1 h at ambient temperature, the reaction mixture was charged with iodomethane (1.5 mL, 24 mmol) and then stirred at ambient temperature overnight. The reaction mixture was quenched by cautious addition of water and then extracted with DCM. The combined extracts were washed with water, dried over Na2SO4, concentrated under reduced pressure, and purified by column chromatography, eluting with EtOAc-Hex (0:100 to 20:80), to provide the title compound (1.64 g, 78%) as a white solid. 1H-NMR (CDCl3): δ 7.33 (1H, s), 4.25 (2H, q), 3.58 (3H, s), 2.24 (3H, s), 1.33 (3H, t).

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