Sulfuric Acid → 5-(2-(4-fluorophenyl)allyl)-2,3,4,5-tetrahydro-2,8-dimethyl-1H-pyrido[4,3-b]indole

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Reaction Conditions

Reaction Steps

2-(4-Fluorophenyl)-1-(1,2,3,4-tetrahydro-2,8-dimethylpyrido[4,3-b]indol-5-yl)propan-2-ol (4.6 g, 13.05 mmol, 1 equiv.) was heated to reflux with 14 mL of 25% aq. sulfuric acid for 2 h. The reaction mixture was cooled to 0-5° C. and made alkaline with 15% aq. KOH solution and extracted with THF:EtOAc (1:1 mixture, 2×30 mL). The combined organic layer was washed with water (15 mL) and then brine, dried over sodium sulfate and evaporated under vacuum. 4.1 g of crude product was obtained which contained 5-((Z)-2-(4-fluorophenyl)prop-1-enyl)-2,3,4,5-tetrahydro-2,8-dimethyl-1H-pyrido[4,3-b]indole as the minor isomer. This isomer was isolated by repeated flash chromatography using 230-400 mesh silica gel using EtOAc as eluent. Yield: 500 mg of 5-((E)-2-(4-fluorophenyl)prop-1-enyl)-2,3,4,5-tetrahydro-2,8-dimethyl-1H-pyrido[4,3-b]indole and 1 g of 5-(2-(4-fluorophenyl)allyl)-2,3,4,5-tetrahydro-2,8-dimethyl-1H-pyrido[4,3-b]indole were isolated as pure products.

Provenance & Evidence