Trifluoroacetic acid → Beta-Carboline

Participants

Reaction Conditions

Reaction Steps

Trifluoroacetic acid (0.62 mL, 8.11 mmol) was added to a mixture of Intermediate 13a (950 mg, 3.86 mmol) and piperonal (695 mg, 4.63 mmol) in CH2Cl2. (25 mL) at 0° C. under a nitrogen blanket, after which the mixture was warmed to room temperature stirred for 24 hours. The reaction mixture was diluted with CH2Cl2 (50 mL) and neutralized with saturated NaHCO3 solution (10 mL). The organic layer was washed with water (10 mL) and brine (15 mL), dried over Na2SO4, filtered, and the solvent was removed under reduced pressure. The residue was purified by flash column chromatography, eluting with CH2Cl2/EtOAc (10:1), to afford β-carboline Intermediate 18 as an inseparable mixture of cis and trans isomers, and was used for the next step without further purification (950 mg, 65%): TLC Rf (10:1 CH2Cl2/EtOAc)=0.40.

Provenance & Evidence