In the presence of a catalytic amount of Ni(cod)(2) and IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), a cross-trimerization reaction of tetrafluoro-ethylene (TFE), ethylene, and aldehydes proceeded in a selective manner to afford a variety of 4,4,5,5-tetrafluoro-1-pentanone derivatives in good to excellent yields. The present system involves a five-membered nickelacycle key intermediate generated via the oxidative cyclization of TFE and ethylene.