azides and alkynylboronates. Trimethylsilyl-substituted
alkynes undergo highly regioselective cycloaddition and the
corresponding products can be manipulated via functionalisa-
tion of the boronate and the TMS-groups. The chemistry
can be extended to include other alkynylboronates although
regioselectivities appear to be significantly lower. Mechanistic
studies on this reaction and the application of this chemistry
for the synthesis of heterocycle arrays is underway and will be
reported in due course.
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We are grateful to the EPSRC (EP/E016898/1) and
GlaxoSmithKline for financial support.
Notes and references
1 W.-Q. Fan and A. R. Katritzky, in Comprehensive Heterocyclic
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2 R. Huisgen, Angew. Chem., Int. Ed. Engl., 1963, 2, 565;
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3 H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew. Chem., Int.
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9 Alkynylboronate synthesis was carried out in accordance with
Brown’s procedure: H. C. Brown, N. G. Bhat and M. Srebnik,
Tetrahedron Lett., 1988, 29, 2631.
10 The product regiochemistry of compounds 2 and 6 was determined
by HMBC experiment and that of 5 was determined by NOE
NMR spectroscopy of the corresponding protodeboronated pro-
duct. The remaining triazoles are proposed to be formed with
analogous regiochemistry. Details are provided in the ESIw.
11 M. R. Netherton and G. C. Fu, Org. Lett., 2001, 3, 4295.
12 The cycloaddition of alkynylbromides and azides can provide a
direct route to these compounds: B. H. M. Kuijpers, G. C. T.
Dijkmans, S. Groothuys, P. J. L. M. Quaedflieg, R. H. Blaauw,
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4 A. Dondoni, Chem.–Asian J., 2007, 2, 700.
5 Boronic Acids, ed. D. G. Hall, Wiley-VCH, Weinheim, Germany, 2005.
6 J. E. Moore, M. W. Davies, K. M. Goodenough, R. A. J. Wybrow,
M. York, C. N. Johnson and J. P. A. Harrity, Tetrahedron, 2005, 61,
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13 The product regiochemistry of compounds 22a and 22b was
determined by HMBC experiment. The regiochemistry of the
inseparable isomers of compounds 23 and 24 was not determined.
7 For recent metal mediated or catalysed processes see:
M. W. Davies, C. N. Johnson and J. P. A. Harrity, J. Org. Chem.,
2001, 66, 3525; V. Gandon, D. Leca, T. Aechtner, K. P.
ꢀc
This journal is The Royal Society of Chemistry 2009
438 | Chem. Commun., 2009, 436–438