A. Bis(trifluoroethyl) methylphosphonate 1. All glassware is oven-dried. A 1-L, four-necked, round-bottomed flask is fitted with an efficient mechanical stirrer, a thermometer, reflux condenser with a bubbler, and a 200-mL, pressure-equalizing dropping funnel with a nitrogen inlet. Under a gentle flow of nitrogen, the flask is charged with 300 mL of anhydrous tetrahydrofuran (THF) (Note 1), 42 g (0.42 mol) of trifluoroethanol (Note 2), and 42.4 g of triethylamine (Note 2). Stirring is started, and the flask is immersed in a cool (~ 10°C) water bath. The dropping funnel is charged with a solution of 26.6 g (0.2 mol) of methylphosphonic dichloride (Note 3) in 100 mL of THF, that is subsequently added at a constant rate over 30 min. The internal temperature rises to 20–30°C, and a white solid precipitates. After the addition is complete, the water bath is removed, and the resulting mixture is stirred at room temperature for 2 hr. The organic salts are removed by suction filtration through a glass funnel, and the filter cake is washed with three 50-mL portions of THF. The solvent is completely removed under reduced pressure on a rotary evaporator. The residue is dissolved in 100 mL of dry ether and filtered to remove insoluble triethylamine hydrochloride, using an additional 40 mL of ether to aid the filtration/transfer. Solvent is again completely evaporated under reduced pressure. Crude product 1, thus obtained, is transferred to a 100-mL pear-shaped flask, fitted with a short distillation column (Note 4), and distilled under reduced pressure to afford 45.3–48.0 g (89–93%) of pure bis(trifluoroethyl) methylphosphonate (1) as a colorless liquid, bp 88–91°C (14 mm), which affords white crystals on standing in the freezer (Note 5). When sufficiently pure, 1 will crystallize on standing at room temperature.

B. Bis(trifluoroethyl) (carboethoxymethyl)phosphonate (2). An oven-dried, 1-L, four-necked, round-bottomed flask is fitted as above (Part A), flushed with nitrogen, and charged with 131 mL (0.210 mol) of a solution of butyllithium (1.6 M in hexane) (Note 6). The solution is cooled with stirring to approximately −20°C in a dry ice-acetone bath, and the dropping funnel is charged with a solution of 34 g (0.212 mol) of hexamethyldisilazane (Note 7) in 110 mL of tetrahydrofuran (THF) (Note 1). The contents of the addition funnel are added dropwise over 15 min during which time the yellow color practically disappears. A fine white suspension forms when the resulting solution is cooled to −78°C. A solution of 26 g (0.1 mol) of 1 and 11.5 g (0.106 mol) of ethyl chloroformate (Note 7) in 60 mL of THF is then added dropwise over 15 min via the addition funnel. During the course of the addition, the temperature rises to between −75° and −65°C, and the solution becomes clear. The reaction mixture is stirred at −70°C for an additional 15 min; the flask containing the reaction mixture is securely stoppered and stored overnight at −20°C in a freezer (Note 8). The cold (−20°C) reaction mixture is poured into a stirred mixture of 170 mL of 2 M hydrochloric acid and an equal volume of crushed ice, and 150 mL of methylene chloride. The organic layer is separated, and the aqueous layer is extracted twice with 50 mL of methylene chloride (Note 9). The combined organic extracts are diluted with 200 mL of hexane to facilitate drying, and then dried for ~12 hr over anhydrous magnesium sulfate (Note 10). After removal of the magnesium sulfate by filtration, the solvents are evaporated under reduced pressure using a rotary evaporator to give crude 2 as a pale yellow liquid. Subsequent distillation of this crude material in a short path distillation apparatus (Note 11) under reduced pressure gives, after a small forerun (Note 12), 25.5–26.3 g (77–79%) of bis(trifluoroethyl) (carboethoxymethyl) phosphonate (2) as a colorless oil, bp 88–97°C (0.04 mm) (Note 13).