N-bromobutanimide → 8-bromo-10a-(4-chlorophenyl)-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrrolo[1,2-d]pyrazin-5-one

Participants

Reaction Steps

To a solution of 10a-(4-chlorophenyl)-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrrolo[1,2-d]pyrazin-5-one (100 mg, 0.35 mmol) dissolved in THF (20 mL) was added N-bromosuccinimide (62 mg, 0.35 mmol) and the reaction mixture was stirred at room temperature for 1 h. LCMS analysis showed a mixture of mono brominated product (366/368 m/z), a small amount of dibrominated pyrrole (446 m/z) and debrominated starting material (288 m/z). The reaction mixture was partitioned with water (25 ml) and CH2CL2 (25 mL) and the organic layer was separated and concentrated in vacuo to give crude product (light yellow oil). The crude mixture was then purified using flash chromatography (Biotage SP4, 12 g cartridge, 0-10% MeOH gradient in CH2Cl2) to give 7-bromo-10a-(4-chlorophenyl)-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrrolo[1,2-d]pyrazin-5-one (A) and 8-bromo-10a-(4-chlorophenyl)-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrrolo[1,2-d]pyrazin-5-one (B) in a 0.6:1 ratio (98.4 mg, yield 77%). The mixture was used without further purification in the next step.

Provenance & Evidence