10.1002/anie.201806296
Angewandte Chemie International Edition
COMMUNICATION
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homolysis of their neutral benzimidazole reagent.[18] When we
conducted a similar UV-homolysis experiment (DGN–O = 53.2 kcal
·mol-1) with much higher energy radiation, we observed an inferior
yield of 30%. However, even with an N–O bifurcation barrier
computed to be D(DG) = 3.1 kcal·mol-1, we expected that the
efficiency of our reaction could be diminished by competing
background reaction of aryl pyridination under standard
photoredox conditions (Scheme 3). Thus, even, under our
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further quenched by a number of species including various
oxidation states of ground state or excited [Ru] or sacrificial
oxidation of the cyclohexadienyl radical (see SI).[31]
To support the radical nature of the reaction, we carried out a
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highly reactive oxygen radical, we have preliminary evidence for
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MeCN matrix, ostensibly through an intermolecular charge-
transfer photoexcitation (see Scheme 3).
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In summary, we have designed highly electrophilic N–O
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to late-stage diversification, this class of pyridinium reagents has
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oxidants for directed, transition-metal mediated routes to solve
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Acknowledgements
This research was gratefully supported by ETH Zürich, by
NSERC for a postdoctoral fellowship (BJ), and by kind gifts from
Syngenta Crop Protection AG (Stein, Switzerland). IF thanks the
Collaborative Research and Training Experience program for a
postdoctoral fellowship. The authors thank Dr. A. Poblador-
Bahamonde and Carmine Chiancone (both U. de Genève) for
access to their computational facilities.
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Keywords: trifluoromethoxylation • photoredox • late-stage
[18] Albeit a distinctly different mechanism and reagent, a new N–OCF3
reagent was reported during the final stages of this work, see: W. Zheng,
C. Rivera, J. Lee, P. Liu, M. Ngai, Angew. Chem. Int. Ed. 2018, DOI:
10.1002/anie.201800598.
functionalization• organofluorine • radical mechanisms
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