Ammonium Chloride → 8-(3,5-Difluorophenyl)-1,4-dioxaspiro[4.5]decane

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Reaction Steps

A Grignard reagent prepared from dried magnesium and 50 g (0.26 mol) of 1-bromo-3,5-diflorobenzene in THF was added dropwide at room temperature to a solution of 34 g (0.22 mol) of cyclohexanedion monoethylene ketal in 500 ml of THF and the mixture was stirred for 5 hours. The reaction solution was added to 500 ml of a saturated ammonium chloride and the mixture was stirred. The reaction product was extracted with ether. The extract was dried over magnesium sulfate and the solvent was distilled off. The residue and 2 g of p-toluenesulfonic acid were added to 300 ml of toluene, and the mixture was refluxed for 3 hours, while removing the produced water using Dean-Stark. The reaction solution was washed successively with water, a saturated aqueous sodium carbonate and water, dried over magnesium sulfate, and then the solvent was distilled off. The residue was purified by column chromatography on silica gel (eluting solvent: heptane/ethyl acetate=3/1), and the solvent was distilled off under reduced pressure. The residue thus obtained was hydrogenated in ethanol in the presence of 2 g of 5% palladium/carbon. The catalyst was filtered off and then the solvent was distilled off to afford 31 g (0.12 mol) of 4-(3,5-difluorophenyl)-cyclohexanone mono-ethylene ketal.

Provenance & Evidence