In a 2000 mL three-necked flask, 1000 g of tetrahydrofuran (THF), 424 g of o-xylene, and 60 g of p-toluenesulfonic acid (p-TsOH) were added, and the reaction temperature was controlled to be below 40°C. The reaction was carried out by a slow pass of 400 g of hexafluoroacetone gas. 400 g of hexafluoroacetone gas was slowly passed. After heating and refluxing the reaction for 12 hours, it was cooled to room temperature. The reaction mixture was washed with saturated sodium bicarbonate (NaHCO3) aqueous solution to pH 7-8. 500 g of toluene was added, partitioned and the organic phase was washed with deionized water. The washed organic phase was concentrated to give a solid crude product. The crude product was recrystallized by dissolving in 1200 g of ethanol. The wet product was dried under vacuum at 40 ℃ for 12 hours to obtain 670 g of white crystal product with 93.1% yield. The product was analyzed by gas chromatography (GC), and the purity was 99.6%, the content of single impurity was less than 0.1%, and the content of all metal ions was less than 1 ppm.
