Synthesis
To stirred solution of dried 18-crown-6 (4.50 g, 17.02 mmol), THF (20 mL), and
phosphite 1 (0.55 mL, 3.75 mmol) was added KHMDS (8.5 mL, 4.25 mmol, 0.5 M in toluene) in a dropwise manner by syringe at -78 ℃. After 15 min, ethyl 2-bromobutyrate
(0.50 mL, 3.38 mmol) was added to the flask and after continuous stirring for 4 hr at
room temperature the typical workup protocol was followed. The crude product was then
purified by flash column chromatography (7:1-4:1 hexanes:EtOAc, Rf = 0.14 in 2:1
hexanes:EtOAc) yielding Butanoic acid, 2-[bis(2,2,2-trifluoroethoxy)phosphinyl]-, ethyl ester (168 mg, 0.47 mmol, 13.8%) as a yellow
syrup.
