A new and general one-pot transformation of aromatic aldehydes to fluorinated olefins containing -CH=C(Cl)CF3 or -CH=C(F)CClF2 moieties is described. Freons CCl3CF3 and CCl2FCCIF2 were used as trifluoromethyl and difluoromethyl C-2-building blocks respectively. A proposed mechanism for the reaction is discussed. (C) 2001 Elsevier Science Ltd. Ali rights reserved.