Organic Letters
Letter
purification step. When using various thiols with carbonate 2b,
low to moderate conversions (30−58%) were observed. NMR
analysis of the crude mixtures unfortunately revealed that the
major component was the isomerized products 8 along with
other unidentified fluorinated side products (7−15%). The
desired allylic thioethers 7 were only observed in low yield (2−
ASSOCIATED CONTENT
Supporting Information
■
*
S
Detailed experimental procedures and full spectroscopic data for
16
6
%) when R = Ph or Bn. Further NMR experiments confirmed
AUTHOR INFORMATION
the rapid isomerization of 7 to 8 under the reaction conditions.
We believe that, in this case, the isomerization process is
facilitated due to the increased acidity of the allylic proton located
α to the sulfur atom. This observation would also support a base-
■
Notes
1
2,17
mediated process for the isomerization.
The lower
The authors declare no competing financial interest.
conversions observed may result from poisoning of the palladium
catalyst.
Finally, we investigated the possibility to further functionalize
the product obtained using 3c as a model compound, and the
results are shown in Scheme 5. For instance, hydrogenation
ACKNOWLEDGMENTS
■
This work was supported by the Canada Research Chair
Program, the Natural Sciences and Engineering Research
Council of Canada, the Canada Foundation for Innovation,
FRQNT Centre in Green Chemistry and Catalysis (CGCC), and
Scheme 5. Further Functionalization of 3c
Universite
4,4-difluorocyclohexane)methylamine hydrochloride. We also
thank Pierre Audet (Universite Laval) for his assistance in the
́
Laval. We thank OmegaChem for a generous gift of
(
́
determination by NMR of the stereochemistry of 10.
REFERENCES
■
(
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18
in quantitative yield. Even though the number of known Diels−
19
Alder reactions of trifluoromethylalkenes is limited, a Diels−
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3
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20
substituted saturated cycles. Indeed, a combined isolated
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2
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N
N
2
1,22
and excellent enantioselectivity (>99% ee).
5
(
3
2
In conclusion, we have reported the use of a regioselective
Tsuji−Trost reaction catalyzed by palladium nanoparticles for
the introduction of the 4,4,4-trifluorobut-2-ene chain using
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(
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(
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3
1
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economical sources of palladium, PdCl . Furthermore, the
2
Ishihara, T.; Yamanaka, H. J. Org. Chem. 2002, 67, 1768−1775.
products are amenable to additional synthetic transformations.
Overall, this method provides a new and alternative approach to
useful fluorinated molecules.
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C
Org. Lett. XXXX, XXX, XXX−XXX