Synthesis and polymerisation of fluorinated monomers bearing a reactive lateral group. Part 5 - Radical addition of iodine monobromide to chlorotrifluoroethylene to form a useful intermediate in the synthesis of 4,5,5-trifluoro-4-ene-pentanol
B. Ameduri et al., Synthesis and polymerisation of fluorinated monomers bearing a reactive lateral group. Part 5 - Radical addition of iodine monobromide to chlorotrifluoroethylene to form a useful intermediate in the synthesis of 4,5,5-trifluoro-4-ene-pentanol, J FLUORINE, 93(2), 1999, pp. 117-127
The synthesis of the new halogenated alcohol BrCF2CFClCH2CHICH2OH as a prec
ursor of 4,5,5 trifluoro-4-ene pentanol F2C=CFC3H6OH is based on a two-step
process. First, the radical addition of iodine monobromide to chlorotriflu
oroethylene (CTFE) led to the expected BrCF2CFClI (I) and ICF2CFClBr (II),
but also to BrCF2CFClBr (III) and ICF2CFClI (IV), the amount of which deter
mined by F-19 NMR depended on the reaction conditions: by feeding CTFB into
IBr continuously or in batches; photochemical or thermal initiations, and
with various initial [IBr](0)/[CTFE](0) molar ratios. In most cases, isomer
(I) was mainly produced. The second step concerned the addition of such a
mixture to allyl alcohol yielding the polyhalogenoalcohol with a quantitati
ve conversion of (I). The reactivity of different halogeno end-groups of th
ese isomers toward the allyl alcohol was discussed. Reduction of the iodine
atom into hydrogen and the halogenated alcohol was accompanied by that of
the bromine atom leading to BrCF2CFClC3H6OH and HCF2CFClC3H6OH (V). Dehalog
enation of the former alcohol in the presence of zinc led to F2C=CFC3H6OH w
hile dehydrochlorination of (V) into trifluorovinyl hydroxy monomers was ac
hieved in the presence of potassium hydroxide but in poor yields. Strategie
s starting from the radical additions of iodine monochloride and of iodine
monobromide were compared showing that the former led to better overall yie
lds of trifluorovinyl alcohol than the latter. (C) 1999 Elsevier Science S.
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