Journal of the American Chemical Society
Communication
cleavage using magnesium monoperoxyphthalate (MMPP),20
respectively (Scheme 6).
Goldfarb, Y. L.; Abronin, I. A.; Zhidomirov, G. M. Tetrahedron Lett.
1973, 14, 1761.
(3) Wessels, M.; Mahajan, V.; Bosshammer, S.; Raabe, G.; Gais, H.-J.
Eur. J. Org. Chem. 2011, 2431.
Scheme 6. Representative Hydrazone Transformations
(4) For seminal work, see: (a) Cho, J. Y.; Iverson, C. N.; Smith, M.
R. III J. Am. Chem. Soc. 2000, 122, 12868. (b) Cho, J. Y.; Tse, M. K.;
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40, 1992. (b) Hurst, T. E.; Macklin, T. K.; Becker, M.; Hartmann, E.;
Kugel, W.; Parisienne-La Salle, J.-C.; Batsanov, A. S.; Marder, T. B.;
̈
Snieckus, V. Chem.Eur. J. 2010, 16, 8155.
(6) Boebel, T. A.; Hartwig, J. F. J. Am. Chem. Soc. 2008, 130, 7534.
(7) (a) Kawamorita, S.; Ohmiya, H.; Hara, K.; Fukuoka, A.;
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K.; Kawamorita, S.; Ohmiya, H.; Sawamura, M. Org. Lett. 2010, 12,
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(e) Ishiyama, T.; Isou, H.; Kikuchi, T.; Miyaura, N. Chem. Commun.
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(8) Ros, A.; Estepa, B.; Lop
R.; Lassaletta, J. M. Angew. Chem., Int. Ed. 2011, 50, 11724.
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(10) Minor amounts of o,o′-diborylated products have been detected
in directed borylation of benzoate derivatives7a,f and some nitro-
genated derivatives.9 To the best of our knowledge, there are no other
precedents of directed o,o′-diborylations. For a sterically controlled
diborylation of para-substituted benzonitriles, see: Chotana, G. A.;
Rak, M. A.; Smith, M. R. III J. Am. Chem. Soc. 2005, 127, 10539.
(11) Zhu, L.; Shabbir, S. H.; Gray, M.; Lynch, V. M.; Sorey, S.;
Anslyn, E. V. J. Am. Chem. Soc. 2006, 128, 1222 and references cited
therein.
In summary, the combination of pyridine−hydrazones as
hemilabile N,N-ligands and hydrazones as privileged directing
groups enables a very efficient and regioselective Ir-catalyzed
o,o′-diborylation of benzaldehyde derivatives. The dissymmetric
interaction of the hydrazone with the boryl groups enables the
high-yielding, sequential functionalization of these intermedi-
ates for the straightforward synthesis of densely functionalized
arenes.
́
́ ́
ez-Rodríguez, R.; Alvarez, E.; Fernandez,
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures, characterization data, NMR spectra
for new compounds, and CIF data for 4b and 5a. This material
AUTHOR INFORMATION
Corresponding Author
(12) For a study of related formyl CH···O−B interactions, see:
Corey, E. J.; Lee, T. W. Chem. Commun. 2001, 1321.
■
(13) For previous reports on the use of hydrazones as directing
groups in catalytic C−H functionalization, see: (a) Kakiuchi, F.;
Tsuchiya, K.; Matsumoto, M.; Mizushima, E.; Chatani, N. J. Am. Chem.
Soc. 2004, 126, 12792. (b) Benesch, L.; Bury, P.; Guillaneux, D.;
Houldsworth, S.; Wang, X.; Snieckus, V. Tetrahedron Lett. 1998, 39,
961.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank the Spanish Ministerio de Ciencia e Innovacion
(Grants CTQ2010-15297 and CTQ2010-14974 and a fellow-
ship to B.E.), European FEDER Funds, and Junta de Andalucia
■
(14) 1H NMR analysis of the crude reaction mixtures showed
products in near-quantitative yields. Though chromatography on silica
gel led to extensive decomposition, purification on neutral alumina or
treatment with n-hexane allowed the catalyst and remaining HBpin to
be removed with a moderate loss of product. See Supporting
Information for details.
́
́
(Grants 2008/FQM-3833 and 2009/FQM-4537) for financial
support. A.R. thanks the European Union for a Marie Curie
Reintegration Grant (FP7-PEOPLE-2009-RG-256461), and
R.L.-R. thanks the CSIC for a JAE Predoctoral Fellowship.
(15) The virtual angle reaches a value of 180° for a planar atom and
120° for a tetrahedral atom. See: Rankin, K. N.; Boyd, R. J. J. Phys.
Chem. A 2002, 106, 11168.
(16) Pauling, L. The Nature of the Chemical Bond, 2nd ed.; Cornell
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(17) For reasons that are not clear at this point, the reaction of the
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