A 500-mL 3-neck RBF immersed in an ice bath is equipped with a large stir bar and a condenser that is attached to a 50-mL receiving flask cooled to -78 °C with an acetone-dry ice bath. The RBF is then filled with a slurry of 26 g of sodium bicarbonate in 26 mL of water and 48 g of Oxone® is added with vigorous stirring. An addition funnel filled with 24 mL of trifluoroacetone is pre-cooled to -20 °C which is connected to the RBF, an addition is conducted within circa 10 s. The product under TFA starts to distill and condense into the receiving flask. After 20 minutes, the receiving flask is tightly closed with a plastic stopper, wrapped with aluminum foil and stored at –80 °C.
Addition of the NaHCO3
Addition of trifluoroacetone
The distilled product of 0.4 M to 0.6 M concentration