Trifluoroacetic acid → 9-Bromo-1,2,3,4,10,10a-hexahydro-pyrazino[1,2-a]indole

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Reaction Steps

9-Bromo-1,2,3,4-tetrahydro-pyrazino[1,2-a]indole (3.5 g, 13.9 mmol) was dissolved in THF (15 mL) and trifluoroacetic acid (30 mL) and cooled to 0° C. Sodium borohydride (1 g, 27.9 mmol) was added in portions, the mixture was stirred for 90 min at room temperature and added to an ice/water mixture (150 mL). After addition of sodium hydroxide solution (28%, 35 mL) to render the mixture basic it was extracted with dichloromethane. Organic phases were pooled, washed with brine, dried with MgSO4 and the solvent was evaporated. Chromatography on silica gel (dichloromethane/methanol/ammonia 180:10:1) yielded 9-bromo-1,2,3,4,10,10a-hexahydro-pyrazino[1,2-a]indole (2.4 g, 68%) as a yellowish solid, MS: m/e=252.0 (M+).

Provenance & Evidence