F. Chanteau et al. / Tetrahedron Letters 43 (2002) 1677–1680
1679
Scheme 5.
1a, 1b and 1d, giving good isolated yields of the corre-
sponding cyclohexene derivatives 4a, 4b and 4d. On the
other hand, reaction of 1a and 1b with isoprene gave 5a
and 5b, respectively, as a mixture of regioisomers,
whose structures were attributed according to the
NMR spectra (Scheme 5).18 The major compound is the
one expected from a ‘normal’ enone, but the low
regioselectivity probably results from the counter effect
of the b-perfluoroalkyl substituent.
Organofluorine Compounds. Chemistry and Applications;
Springer: Berlin, 2000.
2. (a) Welch, J. T. Tetrahedron 1987, 43, 3123–3197; (b)
Welch, J. T.; Eswarakrishnan, S. Fluorine in Bioorganic
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The structure of the acyl moiety has no influence on the
dienophilic properties of these hemifluorinated enones,
neither from the kinetic nor from the stereoselectivity
point of view. Furthermore, we explored the reactivity
of hemifluorinated enones with furan, and attempted to
modify the regioselectivity of the cycloaddition with
isoprene, using Lewis acid (TiCl4 or BF3·Et2O) as acti-
vator. In each case, the experiments were unsuccessful:
no reaction occurred at low temperature whereas total
decomposition was observed at room temperature.
4. (a) Ernet, T.; Haufe, G. Tetrahedron Lett. 1996, 37,
7251–7252; (b) Ernet, T.; Maulitz, A. H.; Wu¨rthwein,
E.-U.; Haufe, G. J. Chem. Soc., Perkin Trans. 1 2001,
1929–1938.
In summary, the presented results disclose the unprece-
dented application of hemifluorinated enones in [4+2]
cycloadditions, giving new cyclic or bicyclic fluorinated
compounds of potential synthetic interest. Extension of
the scope of these reactions as well as synthetic applica-
tions will be reported in due course.
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Acknowledgements
We are grateful to the M.E.N.E.S.R. and the DFG for
PhD fellowships (F.C. and M.E.), to the Graduate
College ‘Highly Reactive Multiple Bond Systems’ for
financial support, and to the ATOFINA Company for
the generous gift of perfluoroalkyl iodides.
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