Trifluoroacetic acid → 5-Chloro-2-(1-methyl-1,2,3,6-tetrahydropyridin-4-yl)benzo-thiophene

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Reaction Steps

To 0.30 gm (1.06 mMol) 5-chloro-2-(1-methyl-4-hydroxy-1,2,3,6-tetrahydropyridin-4-yl)benzothiophene were added 4.0 mL trifluoroacetic acid. The reaction mixture was stirred for two hours at room temperature. The volatiles were removed under reduced pressure and the residue partitioned between aqueous sodium bicarbonate and dichloromethane. The phases were separated and the organic phase dried over sodium sulfate and then concentrated under reduced pressure. The residue was subjected to flash chromatography, eluting with chloroform containing 5% methanol. Fractions shown to contain product were combined and concentrated under reduced pressure to give 0.336 gm of 5-chloro-2-(1-methyl-1,2,3,6-tetrahydropyridin-4-yl)benzo-thiophene as an orange powder. A portion of this material was dissolved in ethyl acetate and treated with 1.0 equivalents of oxalic acid. The solution was concentrated under reduced pressure to give the title compound as a rust solid.

Provenance & Evidence