Hydrochloric Acid → 4-(3,4,5-Trifluorophenyl)cyclohexan-1-one

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Reaction Steps

To Grignard reagent prepared from 3,4,5-trifluorobromobenzene 100 g (474 mmol) and magnesium in 360 ml of dried tetrahydrofuran (abbreviated as THF, hereinafter) at room temperature, a THF (500 ml) solution of cyclohexanedione monoethyleneketal 74.0 g (474 mmol) was added dropwise at room temperature, and the mixture was stirred for 5 hours at room temperature. The reactant was added to one liter of 6N-hydrochloric acid, and the product was extracted with diethylether. The extract was washed with water, a saturated sodium bicarbonate aqueous solution, and then water, and dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. To the residue, para-toluene sulfonic acid (abbreviated as PTS, hereinafter) 5 g and toluene 600 ml were added. The mixture was refluxed with heating for 3 hours while removing water formed with Dien-Stark. The reactant was washed with water, a saturated sodium bicarbonate aqueous solution, and then water, and dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (eluent: heptane/ethyl acetate=4/1). Such obtained purified material was hydrogenated in the presence of 5% palladium carbon 5 g as a catalyst in ethanol 300 ml. The catalyst was filtered off, the solvent was distilled off, and the residue was purified by silica gel column chromatography (eluent: heptane/ethyl acetate=3/1) to obtain 4-(3,4,5trifluorophenyl)cyclohexanone 52 g (228 mmol). The yield was 48.1% from 3,4,5-trifluorobromobenzene.

Provenance & Evidence