Organic Letters
Letter
a
Scheme 4. Stereodivergent Synthesis of Polysubstituted Enynes
a
Isolated yields are given in parentheses.
illustrate this point, internal alkyne 6 was used to propose a
stereodivergent synthesis of trisubstituted enynes (Scheme 4).
(Z)-7 was obtained by the method of Trost and Ball,14 with an
α/β selectivity of 80:20. The isomers could not be separated,
and the mixture was coupled with (bromoethynyl)benzene
under our optimal conditions. Trisubstituted enyne (Z)-8 was
obtained with the same ratio of isomers in excellent yield.
Vinylsiloxane (E)-7 was synthesized using an N-heterocyclic
platinum(0) carbene catalyst13 with an α/β selectivity of 80:20.
The isomers could be separated, and pure (E)-7 was coupled
under the same conditions as before. (E)-8 was obtained almost
quantitatively with full retention of stereochemistry. Although
being known to be quite sensitive toward organocopper species,
no addition onto the electron-deficient double bond was ever
observed.
In conclusion, a mild and efficient copper-catalyzed cross-
coupling of vinylsiloxanes with bromoalkynes was presented.
Various cis, trans, and 1,1′-disubstituted vinylsiloxanes were
transformed into enynes with full retention of stereochemistry.
The presence of sensitive groups such as bromides, ketones,
and aldehydes were fully tolerated, emphasizing the very soft
nature of the reaction. Finally, a stereodivergent synthesis of
trisubstituted enynes was proposed, using different hydro-
silylation metal catalysts. Further studies concerning copper-
catalyzed transformations of vinylsilanes are underway and will
be reported in due time.
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ASSOCIATED CONTENT
* Supporting Information
Experimental procedures and characterization data. This
material is available free of charge via the Internet at http://
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AUTHOR INFORMATION
Corresponding Author
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(12) Cornelissen, L.; Vercruysse, S.; Sanhadji, A.; Riant, O. Eur. J.
Org. Chem. 2014, 35−38.
(13) Synthesis of β-(E)-vinylsiloxanes: (a) Berthon-Gelloz, G.;
Notes
Schumers, J.-M.; De Bo, G.; Marko,
4190−4197. (b) De Bo, G.; Berthon- Gelloz, G.; Tinant, B.; Marko,
E. Organometallics 2006, 25, 1881−1890. (c) Dierick, S.; Marko, I. E.
Personal communications with their permission.
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I. E. J. Org. Chem. 2008, 73,
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I.
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
Financial support from the Fonds de la Recherche Scientifique
(FRS-FNRS), the Fonds pour la formation a
l’Industrie et dans l’Agriculture (FRIA), and the Universite
Catholique de Louvain is gratefully acknowledged. We wish to
warmly thank Dr. Christophe Meyer (ESPCI Paris) and Pr.
Fabrice Chemla (UPMC Paris) for useful advices and
encouragements throughout this work.
(14) Synthesis of α-vinylsiloxanes: Trost, B. M.; Ball, Z. T. J. Am.
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(15) Synthesis of β-(Z)-vinylsiloxanes: Faller, J. W.; D’Alliessi, D. G.
Organometallics 2002, 21, 1743−1746.
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