Organic Letters
Letter
of D2O (Scheme 3F). Therefore, the formation of an active
alkenyl-copper(I) species via a cis-addition process of Cu−H to
the alkynyl bond was further confirmed.
To provide some insights into the reaction process, density
functional theory (DFT) calculations were performed on the
hydrosilylation of 6a with PhSiH3 using Xantphos ligand
(Scheme 4).35 The computational results indicate that the
diminishing the product yield or regioselectivity demonstrates
that the current hydrosilylation reaction is a highly useful and
practical methodology. Mechanistic studies and computational
rationalization show that this reaction involves a Cu−H
addition step to the alkynyl bond and a sequential σ-bond
metathesis process with hydrosilane.
ASSOCIATED CONTENT
* Supporting Information
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sı
Scheme 4. Computational Investigation of Copper-
Catalyzed Regioselective Hydrosilylation of Terminal
The Supporting Information is available free of charge at
a
Alkynes
Experimental details, characterization data, and copies of
1H NMR and 13C NMR spectra (PDF)
Accession Codes
crystallographic data for this paper. These data can be obtained
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
■
Yun-He Xu − Department of Chemistry and Hefei National
Laboratory for Physical Sciences at Microscale, University of
Science and Technology of China, Hefei 230026, China; State
Key Laboratory and Institute of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, China; orcid.org/
Authors
Zi-Lu Wang − Department of Chemistry and Hefei National
Laboratory for Physical Sciences at Microscale, University of
Science and Technology of China, Hefei 230026, China
Feng-Lian Zhang − Department of Chemistry and Hefei
National Laboratory for Physical Sciences at Microscale,
University of Science and Technology of China, Hefei 230026,
China
Jian-Lin Xu − Department of Chemistry and Hefei National
Laboratory for Physical Sciences at Microscale, University of
Science and Technology of China, Hefei 230026, China
Cui-Cui Shan − Department of Chemistry and Hefei National
Laboratory for Physical Sciences at Microscale, University of
Science and Technology of China, Hefei 230026, China
Meng Zhao − Department of Chemistry and Hefei National
Laboratory for Physical Sciences at Microscale, University of
Science and Technology of China, Hefei 230026, China
a
(a) Gibbs energy profiles for the Cu-catalyzed hydrosilylation of 6a
with Xantphos ligand. Free energies in solution (in kcal/mol) at the
M06/6-311+G(d,p)-SDD/SMD(THF)//B3LYP-D3(BJ)/6-31G
(d,p)-SDD/SMD(THF) level are displayed. (b) ADCH charges on
the Cu, H, and two alkynyl C atoms of Int-II-A and Int−II-B. 3D
structures were generated by CYLview.34 All of the hydrogens atom of
C−H bond are omitted for clarity.
stereoselectivity is determined by the irreversible hydro-
cupration step, which occurs more selectively via TS−II-III-
A than via TS-II-III-B (20.7 kcal/mol versus 23.1 kcal/mol),
affording vinylcopper(I) species Int-III-A with an obvious
energy decrease of 17.8 kcal/mol. The lower energy of TS-II-
III-A than TS-II-III-B can be addressed by the different
electronegativity of the alkynyl carbon atoms on Int-II-A and
Int-II-B (Scheme 4b).34 The partially positive charged Cu
atom is prone to migrate to the more electronegative terminal
alkynyl carbon atom with the hydride attached to Cu migrating
to the internal alkynyl carbon atom simultaneously. Subse-
quent σ-bond metathesis of Int-III-A via TS-III-7a produces
the 7a−Cu-H complex, which dissociates to give the linear
product 7a and regenerate Cu-H.
In summary, an unprecedented copper-catalyzed regio- and
stereoselective hydrosilylation of alkynes was reported, which
could highly recognize the terminal alkynyl group from
different functionalities. The reaction can be performed
under mild reaction conditions, and a broad range of aliphatic
and aromatic alkynes underwent this reaction in high
efficiency. A gram-scale synthesis of vinylsilane 3e without
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Author Contributions
§Z.-L.W. and F.-L.Z. contributed equally.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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We gratefully acknowledge the funding support of the National
Natural Science Foundation of China (21871240, 21672198)
and the Fundamental Research Funds for the Central
Universities (WK2060190082). The numerical calculations in
D
Org. Lett. XXXX, XXX, XXX−XXX