N-bromobutanimide → 1-tert-butyl 2-methyl 3-bromo-1H-pyrrole-1,2-dicarboxylate

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Synthesis was carried out according to the procedure reported: Hasse et al., Aust. J. Chem., 62(7):683-691 (2009). Crystallized (from water) N-bromo succinimide (100 g, 564 mmol) was added to a solution of 1-tert-butyl 2-methyl pyrrolidine-1,2-dicarboxylate (34.0 g, 148 mmol) in carbon tetrachloride (17 L). The resulting suspension was heated at 85° C. for 2 h. The reaction mixture was cooled to 0° C. and the precipitated succinimide removed by filtration. The filtrate was concentrated under reduced pressure. The dark orange oil obtained was subjected to column chromatography (REDISEP®, silica gel, 120 g, 10% EtOAc/hexanes), gave 1-tert-butyl 2-methyl 3-bromo-1H-pyrrole-1,2-dicarboxylate (18.0 g, 39.1%) as an orange color liquid. 1H NMR (400 MHz, CD3OD) 6 ppm: 1.53 (s, 9H), 3.32 (s, 3H), 6.46 (d, J=3.6 Hz, 1H), 7.44 (d, J=3.6 Hz, 1H).

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