N-bromobutanimide → Tert-butyl 6-bromo-2-methyl-spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4'-piperidine]-1'-carboxylate

Participants

Reaction Conditions

Reaction Steps

To tert-butyl 2-methylspiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (10 g, 32.74 mmol) in methylene chloride (73.5 mL) at 0° C. was added N-bromosuccinimide (5.53 g, 31.10 mmol) portionwise. The reaction was stirred at 0° C. After 30 minutes, additional N-bromosuccinimide (291.4 mg, 1.64 mmol) was added and the reaction was stirred for 1 hour. The reaction was diluted with 0.5 M Na2S2O3 (135 mL) and the aqueous phase was removed. The organic layer was washed with brine (135 mL). The organic layer was dried over sodium sulfate, filtered and the solvent was evaporated under reduced pressure to yield tert-butyl 6-bromo-2-methyl-spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate as a red viscous liquid that was used in the next step without further purification. 1H NMR (400 MHz, DMSO) δ 6.09 (d, J=3.7 Hz, 1H), 5.99 (d, J=3.7 Hz, 1H), 3.78-3.65 (m, 4H), 3.27 (t, J=6.0 Hz, 2H), 3.17-2.92 (m, 2H), 2.21 (s, 3H), 2.03-1.93 (m, 2H), 1.65-1.53 (m, 2H), 1.40 (s, 9H). ESI-MS m/z calc. 383.1, found 386.0 (M+1)+; Retention time: 1.13 minutes (3 minute run).

Provenance & Evidence