N-bromobutanimide → 7-(tert-Butyl) 1-methyl 3-bromo-5,6-dihydroimidazo[1,5-a]pyrazine-1,7(8H)-dicarboxylate

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Reaction Steps

To a stirred solution of Intermediate 1G (2 g, 7.11 mmol) in anhydrous acetonitrile (30 mL) at room temperature, NBS (1.30 g, 7.11 mmol) was added in one portion. The resulting mixture was stirred at room temperature in the dark for 24 hours. The solvent was removed under reduced pressure and the residue was diluted with ethyl acetate. A saturated aqueous solution of sodium sulfite was added and the biphasic mixture was stirred vigorously at room temperature for 30 minutes. The aqueous phase was separated and the organic layer was washed twice with brine, dried over anhydrous MgSO4, filtered and evaporated under reduced pressure to give the crude product which was purified by column chromatography (silica), eluting with ethyl acetate/hexane mixtures to give Intermediate 1H as a white solid at 60% yield. 1H-NMR (400 MHz, CDCl3) δ: 1.52 (s, 9H), 3.85 (m, 2H), 3.89 (s, 3H), 3.93 (m, 2H), 4.89 (s, 2H). LCMS (+ESI) m/z 362.16 [M+H]+, 360.16 [M+H]+.

Provenance & Evidence