NaTure CHemisTrY
Articles
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fuorination and aryl halide exchange mediated by a Cui/Cuiii catalytic cycle.
J. Am. Chem. Soc. 133, 19386–19392 (2011).
aryl leaving groups to address the challenge of copper(iii)-mediated
photoredox catalysis as a promising reactivity manifold. In contrast
to mononuclear leaving groups, such as bromide, complex leav-
ing groups can bear a positive charge that can lower the reduction
potential while they maintain the ability to engage in productive
redox catalysis if they display appropriate stereoelectronic proper-
ties. Therefore, the conceptual value of our contribution is also to
provide a suitable hypothesis for the design of new leaving groups
that do not undergo deleterious side reactions and so can also
engage in metallophotoredox catalysis with copper or other metals.
14. Le, C., Chen, T. Q., Liang, T., Zhang, P. & MacMillan, D. W. C. A radical
approach to the copper oxidative addition problem: trifuoromethylation of
bromoarenes. Science 360, 1010–1014 (2018).
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consecutive visible light-induced electron transfer processes. Science 346,
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activation through light-color regulation of redox potentials. Angew. Chem.
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Methods
17. Nguyen, J. D., D'Amato, E. M., Narayanam, J. M. R. & Stephenson, C. R. J.
Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated
free radical reactions. Nat. Chem. 4, 854–859 (2012).
General procedure for fuorination. To a 4ml borosilicate vial, equipped with
a stir bar, was added Ir[dF(CF3)ppy]2(dtbpy)PF6 (2.4mg, 2.1μmol, 1.0mol%)
(dF(CF3)ppy, 2-(2,4-difuorophenyl)-5-(trifuoromethyl)pyridine; dtbbpy, 4,4′
-di-tert-butyl-2,2′-bipyridine)) and an aryl (tetrafuoro)thianthrenium salt
(0.200mmol, 1.00equiv.). Under N2 atmosphere, Cu(MeCN)4BF4 (94.4mg,
0.300mmol, 1.50equiv.), anhydrous CsF (36.4mg, 0.240mmol, 1.20equiv.) and
anhydrous acetone (2.0ml, 0.10M) were added into the reaction vial. Subsequently,
the vial was capped and placed 5cm away from two 34W blue light-emitting diode
(LEDs). Te temperature was kept at approximately 30°C through cooling with
a fan. Afer being stirred for 20h, the reaction mixture was diluted with CH2Cl2
(2ml) and the resulting mixture was fltered through a short pad of Celite using
CH2Cl2 (5ml) as eluent. Te fltrate was collected and concentrated by rotary
evaporation. Te residue was purifed by chromatography on silica gel to aford
the fuorinated product.
18. Costentin, C., Robert, M. & Savéant, J. M. Fragmentation of aryl halide π
anion radicals. Bending of the cleaving bond and activation vs driving force
relationships. J. Am. Chem. Soc 126, 16051–16057 (2004).
19. Yang, S., Chen, M. & Tang, P. Visible‐light photoredox‐catalyzed and
copper‐promoted trifuoromethoxylation of arenediazonium
tetrafuoroborates. Angew. Chem. Int. Ed. 58, 7840–7844 (2019).
20. Ichiishi, N., Canty, A. J., Yates, B. F. & Sanford, M. S. Cu-catalyzed
fuorination of diaryliodonium salts with KF. Org. Lett. 15,
5134–5137 (2013).
21. Berger, F. et al. Site-selective and versatile aromatic C−H functionalization
by thianthrenation. Nature 567, 223–228 (2019).
22. Ye, F. et al. Aryl sulfonium salts for site-selective late-stage
trifuoromethylation. Angew. Chem. Int. Ed. 58, 14615–14619 (2019).
23. Engl, P. S. et al. C–N cross-couplings for site-selective late-stage
diversifcation via aryl sulfonium salts. J. Am. Chem. Soc. 141,
13346–13351 (2019).
Note that for the optimal results, the use of anhydrous CsF is important for
the reaction. When CsF was weighed under ambient atmosphere, the yield of the
fluorinated product was lower and the yield of the hydrodefunctionalized product
was higher. Schlenk techniques can be used to avoid moisture. For convenience,
we stored and weighed the CsF in a N2-filled glove box; the reactions can be
performed outside a glove box.
24. Lowry, M. S. et al. Single-layer electroluminescent devices and photoinduced
hydrogen production from an ionic iridium(iii) complex. Chem. Mater. 17,
5712–5719 (2005).
Data availability
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radicals to dications. Solvents of low nucleophilicity. Electrochim. Acta 18,
537–541 (1973).
Crystallographic data for the structures reported in this article have been deposited
at the Cambridge Crystallographic Data Centre (CCDC) under deposition
numbers CCDC 1900278 (4), 1900279 (25-TT), 1900280 (40-TT), 1900276
and its Supplementary Information, or from the corresponding author upon
reasonable request.
26. Rupp, H., Verplaetse, J. & Lontie, R. Binuclear copper electron paramagnetic
resonance signals of α-methemocyanin of helix pomatia. Z. Naturforsch. 35 c,
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27. Andrieux, C. P., Savéant, J.-M., Tallec, A., Tardivel, R. & Tardy, C. Concerted
and stepwise dissociative electron transfers. Oxidability of the leaving group
and strength of the breaking bond as mechanism and reactivity governing
factors illustrated by the electrochemical reduction of α-substituted
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28. Kampmeier, J. A. et al. Regioselectivity in the reductive bond cleavage
of diarylalkylsulfonium salts: variation with driving force and
structure of sulfuranyl radical intermediates. J. Am. Chem. Soc. 131,
10015–10022 (2009).
Received: 24 April 2019; Accepted: 17 September 2019;
Published: xx xx xxxx
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Acknowledgements
10. Welin, E. R., Le, C., Arias-Rotondo, D. M., McCusker, J. K. & MacMillan, D.
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We thank C. Costentin (Université Paris VII) for helpful discussions on the
electrochemical analysis. We thank O. Rüdiger (MPI CEC) for providing the
electrochemical set-up and for helpful discussions, S. Marcus and D. Kampen (MPI
KOFO) for mass spectrometry analysis and A. Dreier and J. Rust (MPI KOFO) for the
crystal structure analysis.