Chemical Science
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ARTICLE
Journal Name
"chain" structures as Frohn,25 Seppelt,26 and we have observed
(see SI).
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4
R. Gilmour, J. Org. Chem., 2017, 82, 11792.
DOI: 10.1039/C9SC02162K
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Conclusions
5
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Remarkably, this TCICA/KF approach to oxidative
fluorination of iodoarenes can be employed to synthesize both
aryl-IF2 and aryl-IF4 compounds. Under our reaction conditions,
access to either the I(III)- or I(V)-derivatives is controlled
primarily by the substitution pattern on the iodoarene
substrate, i.e. an ortho-substituent inhibits further conversion
of aryl-IF2 to the corresponding aryl-IF4 compound. An
exception to this trend was also presented in the form of
compound 37, whereby the ortho-substituent participates in a
three-centered bonding interaction with the iodine atom, thus
making the I(V)-derivative accessible. Moreover, this method
arguably presents the mildest synthesis of aryl-IF4 compounds
reported to date, as well as the mildest approach to electron-
deficient aryl-IF2 compounds, as a complement to the methods
of Shreeve and Gilmour that can be used to access more
electron-rich aryl-IF2 compounds using Selectfluor.
Beyond the development of the TCICA/KF approach as an
oxidative fluorination method, this study also raised several
questions about the relationship between the IF2 group and
ortho-substituents on an arene. This resulted in a series of
controlled hydrolysis experiments, computational studies, X-ray
crystallographic analyses, and the synthesis of a probe molecule
that allotted the first detailed dynamic NMR study on rotation
about the C-I bond on substituted aryl-IF2 compounds, from
which, rotational barriers and thermodynamic parameters were
reported herein.
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16 The synthesis of one of the tetralone intermediates required
to make 21 is loosely based on a synthesis reported by
Kutateladze and co-workers: W. C. Cronk, O. A. Mukhina, and
A. G. Kutateladze, J. Org. Chem., 2014, 79, 1235. Additional
modifications were adapted from procedures in ref. 14, as
well as: P. Nguyen, E. Corpuz, T. M. Heidelbaugh, K. Chow, and
M. E. Garst, J. Org. Chem. 2003, 68, 10195.
In all, we hope that our easy access to and increased
structural understanding of aryl-IF2 and aryl-IF4 compounds in
both solution and the solid state will stimulate more research in
this area. Future studies will be focused on studying the
oxidative fluorination mechanism, as well as exploring
applications of aryl-IF2 and aryl-IF4 compounds as possible
reagents.
Conflicts of interest
There are no conflicts to declare.
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Acknowledgements
We thank the ETH transfer office for support in filing a patent
application on this work, in which C.R.P., N.S., and A.T. are listed
as inventors. MoBiAS (ETH) is acknowledged for assistance with
HRMS analyses. Financial support was provided by ETH Zürich
and the ETH Postdoctoral Fellowship Program (C.R.P.).
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Notes and references
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23 C. R. Groom, I. J. Bruno, M. P. Lightfoot, and S. C. Ward, Acta
Cryst., 2016, B72, 171. The CCDC search was conducted on
1
V. V. Zhdankin, Hypervalent Iodine Chemistry: Preparation,
Structure and Synthetic Applications of Polyvalent Iodine
Compounds, John Wiley & Sons, West Sussex, UK, 2014.
2
C. Ye, B. Twamley, and J. M. Shreeve, Org. Lett., 2005, 7, 3961.
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