Communication
ties. N-Protected olefins 1e and 1 f reacted smoothly under
our conditions furnishing N-phthalimide 3e and bis-N-Boc-pro-
tected fluorocyclopropanes 3 f, respectively, in decent yields
and excellent enantioselectivities for both diastereoisomers.
Fluoroallylsilane 1g was reacted under our standard condi-
tions and the resulting fluorocyclopropane 3g was obtained in
80% isolated yield with a reverse diastereoselectivity and ex-
cellent enantiomeric excesses. Finally, fluorostyrene derivative
1h was tested, yielding fluorocyclopropanes 3h in good yield
with 70:30 diastereoisomeric ratio and an excellent enantio-
meric excess for each diastereoisomer. Encouraged by these
promising results using fluorinated olefins, we turned our at-
tention to the chlorinated substrates. Similarly, the asymmetric
cyclopropanation reaction proceeded well along with a good
functional group tolerance. Indeed, chlorinated olefins bearing
halogen, O-protected alcohol, sulfone, silyl group, N-protected
amine, or phenyl substituents reacted smoothly. The corre-
sponding highly functionalized chlorocyclopropanes 3i–n were
obtained in moderate to good yields and good to excellent
diastereoselectivities. Note that diastereoselectivities are gener-
ally higher with chlorinated olefins than their fluorinated ana-
logues. In all cases, the enantiocontrol of the reaction was ex-
cellent for the major diastereoisomer (up to 96% ee). Regard-
ing olefins, 1m and 1n, a significant drop of the enantiomeric
ratio was measured on the minor diastereoisomer since the
latter was obtained with less than 15% ee. Subsequently, we
studied the bromo-substituted olefins 1o–s to extend the ver-
satility of our methodology. To our delight, our reaction condi-
tions were compatible with various functional groups, such as
halogen, benzyl ether, sulfone, phthalimides, and aryl substitu-
ent. Good levels of diastereocontrol were observed and excel-
lent enantioselectivities were measured for the major diaste-
reoisomers. Finally, in order to compare the effect of the halo-
gen atom on the stereochemical outcome of the reaction, a-
iodo styrene 1t was tested. The corresponding iodocyclopro-
pane 3t was isolated in 94% yield as a 90:10 diastereoisomeric
ratio and 74% ee of the major isomer. Interestingly, the enan-
tioselectivity of the reaction decreased in the order: F>Cl>
Br>I. Indeed, the enantiomeric excess of the major isomer
slightly decreased, whereas the minor isomer was almost ob-
tained as a racemic mixture with a-chloro (3n), -bromo (3s)
and -iodo styrenes (3t). In contrast the diastereoselectivity of
the reaction is higher with chlorinated, brominated, and iodi-
nated olefins compared to the fluorinated ones.
Scheme 2. Synthetic utility of the products.
a catalyst. The corresponding cyclopropanes were obtained in
good yields and moderate to good diastereoselectivities. Both
diastereoisomers were generally obtained with excellent enan-
tiomeric excess. The scope of the reaction was successfully ex-
tended to a broad range of functionalized olefins, highlighting
the high functional group tolerance of the method, giving
access to highly decorated halocyclopropanes. Finally, the ver-
satility of these halocyclopropanes was demonstrated in the
course of functional group manipulations.
Acknowledgements
This work was partially supported by INSA Rouen, Rouen Uni-
versity, CNRS, EFRD, Labex SynOrg (ANR-11-LABX-0029), and
RØgion Haute-Normandie (CrunchNetwork). A.P. thanks the
Labex SynOrg for a doctoral fellowship. P.I. thanks the IS:CE-
Chem project and Interreg IV: A France-(Channel)-England Pro-
gram for a doctoral fellowship. A.B.C. thanks the Labex SynOrg
(ANR-11-LABX-0029) for a chair of excellence.
Keywords: asymmetric catalysis · chiral rhodium catalyst ·
cyclopropane · diazo derivatives · fluorine
8627; c) A. de Meijere, Top. Curr. Chem. 2000, 207, 1–227; d) D. Y. K.
[3] For a review, see: E. David, G. Milanole, P. Ivashkin, S. Couve-Bonnaire, P.
[4] For selected examples of fluorocyclopropanes, see: a) O. Tamura, M. Ha-
clopropanes, see: f) L.-P. B. Beaulieu, L. E. Zimmer, A. Gagnon, A. B. Char-
mocyclopropanes, see: g) H. Y. Kim, L. Salvi, P. J. Carroll, P. J. Walsh, J.
The versatility of the resulting halocyclopropanes can be il-
lustrated by their further functionalization (Scheme 2). We first
demonstrated that the p-methoxybenzyl (PMB) protecting
group can be readily removed from compound 3d, giving 4 in
94% isolated yield.[11] In addition, silylated cyclopropane 3g
can be converted into 4 through a Tamao–Fleming oxidation
without loss of the enantiomeric excess. Then, the Yb-cata-
lyzed selective removal of one Boc protecting group was per-
formed giving 5 in 84% isolated yield.
In summary, we reported in this communication the first
general method to access highly functionalized halocyclopro-
panes starting from readily available haloalkenes and function-
alized diazo derivatives in the presence of [Rh2{(S)-IBAZ}4] as
Chem. Eur. J. 2016, 22, 6239 – 6242
6241
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