Methoxymethyl-triphenylphosphonium chloride → 1-(2,3-Difluorophenyl)-4-methoxymethylene cyclohexane

First, 27.4 g of (methoxymethyl)triphenylphosphonium chloride, 9 g of potassium t-butoxide, and 225 ml of dry ether were placed in a 500 ml flask whose content was replaced with argon. The mixture was stirred for 30 minutes under ice water cooling. Then, 50 ml of an ether solution containing 16.8 g of 4-(2,3-difluorophenyl)cyclohexanone was added dropwise to the reaction mixture. The reaction mixture was stirred under ice water cooling for 30 minutes and at room temperature for 8 hours. Thereafter, a precipitate was filtered out. A filtrate was washed with water and dried over anhydrous sodium sulfate. The solvent was distilled away. Thereafter, the residue was purified by silica gel column chromatography (eluent: toluene/hexane=1/4) to obtain 17.1 g of 1-(2,3-difluorophenyl)-4-methoxymethylene cyclohexane (Y: 89.7%). The compound thus obtained had a purity of 99.2% by GC.