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Journal of the American Chemical Society
Higashino, T.; Hayashi, T. J. Am. Chem. Soc. 2010, 132,
supports the idea that KOtBu can undergo electron transfer to an
15537−15539. Note: this paper also demonstrated effective reacꢀ
tions with NaOtBu. (d) Liu, W.; Cao, H.; Zhang, H.; Zhang, H.;
Chung, K. H.; He, C.; Wang, H.; Kwong, F. Y.; Lei, A. J. Am.
Chem. Soc. 2010, 132, 16737−16740.
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electrophile with a suitable reduction potential, such as CBr4.
In summary, reports on the unique capacity of KOtBu to cause
unusual reactions have appeared regularly in the recent literature:
(i) In the cases of transition metalꢀfree coupling reactions, where
the reactions are conducted in an arene solvent, to date there is no
evidence to support KOtBu acting directly as an electron donor to
an aryl halide. This finding accords both with electrochemical
information on the oxidation potential of KOtBu and with compuꢀ
tational evidence, as well as with our published lack of reaction
between KOtBu and 2ꢀiodoꢀmꢀxylene, 35.5b,5f (ii) Reaction of
KOtBu with DMSO leads to the dimsyl anion, which acts as an
electron donor to appropriate substrates.40 (iii) Reaction of KOtBu
with DMF affords electron transfer activity also, but here, our
experiments indicate a role for a dimerization of formamides to
afford novel and strong organic electron donors.25 Thus in all
these cases, it is the behaviour of KOtBu as a base that gives acꢀ
cess to these electron transfer reactions. The greater basicity of the
KOtBu over its sodium and lithium counterparts likely results
from the difference in the metalꢀoxygen bonding in these salts.14
(2) (a) Sun, C. L.; Gu, Y.ꢀF.; Wang, B.; Shi, Z.ꢀJ. Chem.−Eur. J.
2011, 17, 10844−10847. (b) Sun, C. L.; Gu, Y.ꢀF.; Huang, W.ꢀP.;
Shi, Z.ꢀJ. Chem. Commun. 2011, 47, 9813−9815. (c) Shirakawa,
E.; Zhang, X.; Hayashi, T. Angew. Chem., Int. Ed. 2011, 50,
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Finally, in pursuit of likely examples of direct electron transfer
from KOtBu, we mirrored earlier experiments of Schreiner, who
had used KOH with CBr4. The substrate CBr4 has a reduction
potential near to the oxidation potential of KOtBu and, in the
presence of adamantane as a reporter molecule, leads to 1ꢀ
bromoadamantane via the generation of tribromomethyl radicals.
Computational studies show that in this case, electron transfer
from KOtBu is the likely source of these radicals. This study does
address a number of cases where KOtBu has been associated with
electron transfer, but we are now investigating yet further cases,41
and will report on those in due course.
ASSOCIATED CONTENT
Supporting Information
Experimental procedures including the synthesis of substrates,
important NMR spectra, cyclic voltammetry and EPR studies and
computational coordinates are provided. This material is available
AUTHOR INFORMATION
Corresponding Author
John.Murphy@strath.ac.uk; tell.tuttle@strath.ac.uk
Author Contributions
‡These authors contributed equally.
(6) (a) Liu, W; Xu, L. G. Tetrahedron 2015, 71, 4974−4981. (b) Liu,
W.; Liu, R.; Bi, Y. Tetrahedron 2015, 71, 2622−2628. (c) Doni,
E.; Zhou, S.; Murphy, J. A. Molecules, 2015, 20, 1755−1774. (d)
Masters, K.ꢀS. RSC Advances 2015, 5, 29975−29986. (e) Yi, H.;
Jutand, A.; Lei, A. Chem Commun. 2015, 51, 545−548.
Notes
The authors declare no competing financial interests.
(7) Patil, M. J. Org. Chem, 2016, 81, 632−639.
ACKNOWLEDGMENT
(8) Barham, J. P.; Coulthard, G.; Kane, R. G.; Delgado, N.; John, M.
P.; Murphy, J. A. Angew. Chem. Int. Ed., 2016, 55, 4492ꢀ4496. .
(9) Sun, C. L.; Gu, Y.ꢀF.; Wang, B.; Shi, Z.ꢀJ. Chem.−Eur. J. 2011,
17, 10844−10847..
We thank Prof. John C. Walton for assistance and advice on EPR.
We thank EPSRC (current grant number EP/K033077/1) and GSK,
AstraZeneca and the University of Strathclyde for funding. High
resolution mass spectra were obtained at the EPSRC National
Mass Spectrometry Centre, Swansea.
(10) Studer, A.; Curran, D. P. Angew. Chem. Int. Ed. 2011, 50,
5018−5022.
(11) OksdathꢀMansilla, G.; Argüello J. E.; Peñéñory, A. B.
Tetrahedron Lett. 2013, 54, 1515−1518.
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