2-(1,3-Dioxan-2-yl)ethyltriphenylphosphonium bromide → 2-(2-(4-(2,3-Difluoro-4-ethoxyphenyl)cyclohexylidene)-ethyl)-1,3-dioxane

Participants

Reaction Conditions

Reaction Steps

A mixture of 2-(1,3-dioxane-2-yl)-ethyltriphenyl phosphonium bromide (60.4 mmol) and 30 ml of THF was cooled down 20 to −30° C. by use of a refrigerant under a nitrogen flow. To this mixture, t-BuOK (60.4 mmol) was added, and the mixture was stirred for one hour. A solution of the crude 4-(2,3-difluoro-4-ethoxyphenyl)-cyclohexanone (50.3 mmol) dissolved in 100 ml of THF was added dropwise to this mixture while temperature was maintained at −30° C. or below. After completion of the addition, the reaction temperature was gradually elevated to room temperature, and the mixture was stirred for 2 hours. The reaction mixture was filtered with celite, the solvent was distilled off under reduced pressure, the residue was subjected to silica gel column chromatography (eluent: a mixed solvent of ethyl acetate/toluene=3/7), the solvent was distilled off under reduced pressure, and the product was re-crystallized from heptane to form 2-(2-(4-(2,3-difluoro-4-ethoxyphenyl)cyclohexylidene)-ethyl)-1,3-dioxane (36.9 mmol).

Provenance & Evidence