Unexpected telomerization of hexafluoropropene with dissymetrical halogenated telechelic telogens

The synthesis of new fluorinated alpha,omega-diiodo telomers I[(TFE)(x)(VDF)(y)(HFP)(z)]I (A) where TFE, VDF and HFP represent tetrafluoroethylene, vinylidene fluoride and hexafluoropropene, respectively, was carried out by thermal telomerization of HFP with VDF oligomers, I(TFE)(x)(VDF)(y)I, as transfer agents. Compound A was obtained in 55% yield when x=y=1, whereas almost no reaction occurred when x=1 and y=2. Interestingly, HFP reacted with IC2F4CH2CF2 . selectively and not with ICF2CH2CF2CF2 . whereas, from IC4F8CH2CF2I, HFP could be introduced on both end-groups but produced a higher amount of I(TEE)(2)(VDF)(HFP)I. The reactivity of HFP is compared with that of VDF in reactions with fluorinated alpha,omega-diiodinated telogens and it is shown that the environment of the terminal C-I bond in the telogen influences the orientation of the reaction.