Abstract A reduction-olefination sequence has been used to convert ethyl pentafluoropropanoate 6 to 1-fluoro-1-phenyl-2-pentafluoroethyl ethene 7 and ethyl 2, 4, 4, 5, 5, 5-hexafluoro-2− pentenoate 8. Addition of lithium diethyl α-fluorobenzylphosphonate [(EtO) 2P (O) CFPh]− Li+ 4 or lithium fluorocarboethoxymethylene dialkylphosphonate [(RO) 2P (O) CFCO2Et]− Li+ 5 (R= Et, i-Pr) to a THF solution of fluorinated aldehydes prepared ...