Journal of the American Chemical Society
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M.; Plattner, D. L.; Staples, R. J.; Maligres, P. E.; Krska, S. W.; Malec-
We have developed a readily accessed, anionic ligand that
engages in a substrate-catalyst ion-pairing interaction to
enable meta-selective borylation of two distinct classes of
aromatic quaternary ammonium salts. The use of non-
covalent interactions to control regioselectivity in transition
metal catalysis is an area of great potential. This study
demonstrates the viability of ion-pairing as a powerful tool
for the development of new regioselective transformations.
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Rodríguez, R.; Estepa, B.; Álvarez, E.; Fernández, R.; Lassaletta, J. M.
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5193.
ASSOCIATED CONTENT
Supporting Information
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Experimental procedures and spectral data is available free of
AUTHOR INFORMATION
Corresponding Author
*rjp71@cam.ac.uk
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENTS
We are grateful to the EPSRC and Pfizer for a CASE student-
ship (H.J.D.), AstraZeneca for
a studentship (M.T.M.)
through the AZ-Cambridge PhD Program, the Royal Society
for a University Research Fellowship (R.J.P.), the EPSRC and
EPSRC UK National Mass Spectrometry Facility at Swansea
University and Dr Andrew Bond for X-ray crystallography.
We thank Professors Steven V. Ley and Matthew J. Gaunt for
support and useful discussions, and Dr David Blakemore
(Pfizer) and Dr Alan D. Brown for useful discussion.
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H. D.; Larionov, O. V. J. Am. Chem. Soc. 2016, 138, 2985.
(16) Zhu, F.; Tao, J.-L.; Wang, Z.-X. Org. Lett. 2015, 17, 4926.
(17) Furuya, T.; Klein, J. E. M. N.; Ritter, T. Synthesis 2010, 1804.
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Soc. 2014, 136, 4575.
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(22) See Supporting Information for full details.
(23) Due to requirements of synthetic accessibility, some sub-
strates were used as their triflate salts.
(24) (a) Takagi, J.; Sato, K.; Hartwig, J. F.; Ishiyama, T.; Miyaura,
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(26) Interestingly, several of these substrates gave higher than ex-
pected meta selectivity with dtbpy in THF (2o, 2p and 4l). Switching
to cyclohexane with dtbpy as ligand gave unexpectedly high meta
selectivity for these compounds, albeit in generally low conversion to
mixtures of mono and diborylated compounds. The substrates in
Schemes 1-3 were found to give poor selectivity using
dtbpy/cyclohexane, demonstrating that this unusual effect was not
general and restricted to substrates with no arene substituents. For
further details and screening of 1a and 1m against a range of bipyri-
dine ligands in cyclohexane to probe this, see supporting infor-
mation.
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