APPLICATION OF FLUOROCARBETHOXY-SUBSTITUTED PHOSPHONATE: A FACILE ENTRY TO SUBSTITUTED 2-FLUORO-3-OXOESTERS

Diethyl(fluorocarbethoxymethyl)phosphonate 1a or diisopropyl(fluorocarbethoxymethyl)phosphonate 1b, prepared from triethyl phosphite or triisopropyl phosphite with ethyl bromofluoroacetate, react with n-butyllithium in THF to give the corresponding phosphonate carbanions [(RO)2P(O)CFCO2Et]−Li+ 2a (R=Et) and 2b (R=i-Pr). Addition of trimethylsilyltrifluoroacetate CF3C(O)OSiMe3 to a THF solution of phosphonate carbanions formed the enolate of ethyl trifluoroacetylfluoroacetate [CF3C(O)CFCO2Et]−Li+ 3. Subsequent protonation, alkylation or allylation of the enolate afforded substituted 2,4,4,4-tetrafluoro-3-oxoesters CF3C(O)CFR1CO2Et 10