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COMMUNICATION
Journal Name
Akhmedov, J. L. Petersen and X. Shi, AngDewOI.:C1h0.e1m03.V9Ii/neCwt6.AECrtdCic.0l,e52O30n61l0in4Be,
53, 5418-5422.
carboboration product 29 (see SI, Scheme 2) with no evidence
of hydroborated products. This infers that under catalysis
conditions, hydroboration of the respective alkyne with pinacol
borane is more rapid than 1,1-carboboration.
Interestingly, the present mechanism is distinct from that
proposed by Hoshi and coworkers8 for hydroboration catalysis
by HBCy2. In this case, both Markovnikov and anti-Markovnikov
addition products are seen but only the former reacts with
HBpin to transfer the alkenyl-fragment liberating HBCy2.
4. K. Wen, J. Chen, F. Gao, P. S. Bhadury, E. Fan and Z. Sun, Org.
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Sci., 2016, 7, 3384-3389.
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Science, 2013, 341, 1374-1377; (b) M. Pérez, L. J. Hounjet, C. B.
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Conclusions
Herein E-alkenyl pinacol boronic esters are readily prepared in
efficient catalytic and atom economic hydroborations with
pinacol borane. While such reactions were shown to proceed
with a variety of Lewis acid catalysts, HB(C6F5)2 is shown to act
as a pre-catalyst generating a mixed 1,1-diborylated alkane
species which functions as the catalytically active species.
Further reactivity studies of such diborylated species are
currently under investigation in our laboratories. The results of
these studies will be reported in due course.
D.W.S. is grateful for the financial support of the NSERC of
Canada and the award of a Canada Research Chair. M.F. and
J.M. acknowledge the financial support of the DFG for a
postdoctoral fellowship. T.v.S. thanks the A.von Humboldt
Foundation for a Feodor-Lynen Research Fellowship.
13. J. Möbus, T. vom Stein and D. W. Stephan, Chem. Commun.,
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Notes and references
Department of Chemistry, University of Toronto, 80 St. George St.,
Toronto,
Ontario
M5S
3H6,
Canada,
Email:
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†Electronic Supplementary Information (ESI) available: Spectroscopy
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Crystallographic details have been deposited in CCDC #1484364.
ŦThese authors have contributed equally.
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