RESEARCH
| REPORTS
Thanks to recent experimental developments
(including SEVI and, crucially for the present
study, the use of a cryogenically cooled ion trap
to produce large amounts of p-FH2− and n-FD2−),
high-resolution anion photodetachment spec-
troscopy does indeed provide an effective way
to observe the elusive resonances in F + H2
reactive scattering, as was predicted by Russell
and Manolopoulos almost 20 years ago (17).
BORON CATALYSIS
Metal-free catalytic C-H bond
activation and borylation
of heteroarenes
REFERENCES AND NOTES
1. J. C. Polanyi, A. H. Zewail, Acc. Chem. Res. 28, 119–132 (1995).
2. D. E. Manolopoulos, J. Chem. Soc. Faraday Trans. 93, 673–683
(1997).
Marc-André Légaré, Marc-André Courtemanche,
Étienne Rochette, Frédéric-Georges Fontaine*
3. G. C. Schatz, Science 288, 1599–1600 (2000).
4. F. Fernández-Alonso, R. N. Zare, Annu. Rev. Phys. Chem. 53,
67–99 (2002).
5. X. Yang, D. H. Zhang, Acc. Chem. Res. 41, 981–989 (2008).
6. R. T. Skodje, in Advances in Quantum Chemistry,
C. A. Nicolaides, E. J. Brändas, R. S. John, Eds. (Academic
Press, New York, 2012), vol. 63, pp. 119–163.
7. K. Liu, in Advances in Chemical Physics, S. A. Rice, A. R. Dinner,
Eds. (Wiley, Hoboken, NJ, 2012), vol. 149, pp. 1–46.
8. D. M. Neumark, A. M. Wodtke, G. N. Robinson, C. C. Hayden,
Y. T. Lee, J. Chem. Phys. 82, 3045 (1985).
9. R. T. Skodje et al., J. Chem. Phys. 112, 4536 (2000).
10. R. T. Skodje et al., Phys. Rev. Lett. 85, 1206–1209 (2000).
11. W. Dong et al., Science 327, 1501–1502 (2010).
12. T. Wang et al., J. Phys. Chem. Lett. 5, 3049–3055 (2014).
13. M. Qiu et al., Science 311, 1440–1443 (2006).
14. D. M. Neumark, Phys. Chem. Chem. Phys. 7, 433–442 (2005).
15. I. M. Waller, T. N. Kitsopoulos, D. M. Neumark, J. Phys. Chem.
94, 2240–2242 (1990).
16. D. E. Manolopoulos et al., Science 262, 1852–1855 (1993).
17. C. L. Russell, D. E. Manolopoulos, Chem. Phys. Lett. 256,
465–473 (1996).
18. C. Hock, J. B. Kim, M. L. Weichman, T. I. Yacovitch,
D. M. Neumark, J. Chem. Phys. 137, 244201 (2012).
19. T. I. Yacovitch et al., Faraday Discuss. 157, 399–414, (2012).
20. A. Osterwalder, M. J. Nee, J. Zhou, D. M. Neumark,
J. Chem. Phys. 121, 6317–6322 (2004).
21. Methods are detailed in the supplementary materials at
Science Online.
22. A. T. J. B. Eppink, D. H. Parker, Rev. Sci. Instrum. 68, 3477 (1997).
23. J. Z. H. Zhang, W. H. Miller, J. Chem. Phys. 92, 1811 (1990).
24. F. Lique, G. Li, H.-J. Werner, M. H. Alexander, J. Chem. Phys.
134, 231101 (2011).
Transition metal complexes are efficient catalysts for the C-H bond functionalization of
heteroarenes to generate useful products for the pharmaceutical and agricultural
industries. However, the costly need to remove potentially toxic trace metals from the
end products has prompted great interest in developing metal-free catalysts that
can mimic metallic systems. We demonstrated that the borane (1-TMP-2-BH2-C6H4)2
(TMP, 2,2,6,6-tetramethylpiperidine) can activate the C-H bonds of heteroarenes and
catalyze the borylation of furans, pyrroles, and electron-rich thiophenes. The selectivities
complement those observed with most transition metal catalysts reported for this
transformation.
ransition metal–catalyzed reactions are ubiq-
uitous tools in the pharmaceutical and
agrochemical industries, despite the costs
associated with removing residual catalysts;
trace metals in products for human con-
In the borylation reaction using iridium catalysts,
this transformation is usually assisted by the boryl
substituents present on the metal center, which
T
sumption are heavily regulated by international
bodies (1). Similar concerns exist in the modern
electronics industry, where metals need to be re-
moved from organic electronic devices to avoid
loss of efficiency (2). Nevertheless, the importance
of selectively forming bonds between carbon and
other atoms using transition metals has been
acknowledged by three Nobel Prizes in Chemistry
in the past 15 years. More recently, the catalytic
functionalization of C-H bonds using transition
metals has emerged as an atom-economical way
to generate new bonds without the need for ac-
tivated precursors (3, 4). Through such an acti-
vation process, the catalytic Csp2-H borylation of
aromatic molecules generates organoboronates
(5–7), which are important species for the phar-
maceutical industry and in the field of modern
organic materials, notably as building blocks for
the creation of new bonds using the Suzuki-
Miyaura cross-coupling reaction (8, 9). Although
some base metal complexes have been used as
catalysts for the borylation of arenes (10–12),
the most efficient systems to date rely on noble
metals, most notably iridium (6, 7). Alternative-
ly, borenium or boronium species generated by
highly reactive precursors can promote the elec-
trophilic borylation of arenes, but stoichiomet-
ric quantities of amine derivatives are generally
needed to generate the active boron reagents
(13–15).
25. C. Blondel, C. Delsart, F. Goldfarb, J. Phys. At. Mol. Opt. Phys.
34, 2757 (2001).
26. S. E. Bradforth, D. W. Arnold, D. M. Neumark,
D. E. Manolopoulos, J. Chem. Phys. 99, 6345 (1993).
27. S. L. Holmgren, M. Waldman, W. Klemperer, J. Chem. Phys. 67,
4414 (1977).
28. M. H. Alexander, S. Gregurick, P. J. Dagdigian, J. Chem. Phys.
101, 2887 (1994).
29. J. F. Castillo, D. E. Manolopoulos, K. Stark, H.-J. Werner,
J. Chem. Phys. 104, 6531 (1996).
30. D. E. Manolopoulos, Nature 419, 266–267 (2002).
31. B. Fu, X. Xu, D. H. Zhang, J. Chem. Phys. 129, 011103 (2008).
ACKNOWLEDGMENTS
The experimental part of this work was funded by the Air Force Office of
Scientific Research (AFOSR) under grant no. FA9550-12-1-0160 and
the Defense University Research Instrumentation Program (DURIP)
under grant no. FA9550-11-1-0330. M.L.W. thanks the National Science
Foundation for a graduate research fellowship. The experimental data
are available upon request from dneumark@berkeley.edu. M.H.A. is
grateful for partial support by the U.S. National Science Foundation
under grant CHE-1213332. D.E.M. is funded by the Wolfson Foundation
and the Royal Society.
SUPPLEMENTARY MATERIALS
Noble metals are well suited to cleave aromatic
C-H bonds in catalytic processes because they
can easily mediate two-electron transfer processes.
Fig. 1. Representative transition states for the
C-H activation of arenes. (A) Activation of C-H
bonds in borylation transformations using Ir cata-
lysts. (B) Carboxylate-assisted metalation depro-
tonation at palladium. (C) Metal-free C-H activation
of heteroarenes using FLP catalysts. The dashed
lines represent bonds formed and cleaved during
the electron transfer.
Materials and Methods
Supplementary Text
Figs. S1 to S7
Tables S1 and S2
Département de Chimie, Centre de Catalyse et Chimie Verte
(C3V), Université Laval, 1045 Avenue de la Médecine,
Québec, QC G1V 0A6, Canada.
References (32–59)
4 June 2015; accepted 9 July 2015
10.1126/science.aac6939
*Corresponding author. E-mail: frederic.fontaine@chm.ulaval.ca
SCIENCE sciencemag.org
31 JULY 2015 • VOL 349 ISSUE 6247 513