Preparation and structure of phenolic aryliodonium salts

Article abstract of DOI:10.1039/C8CC06211K

Phenol based aryliodonium salts were prepared by the reaction of [hydroxy(tosyloxy)iodo]arenes with aryl silyl ethers in the presence of trifluoromethanesulfonic acid. Structures of several aryliodonium salts with the hydroxy group in the para-position of the phenyl ring were established by single crystal X-ray crystallography. Under basic conditions, 4-hydroxyphenyl(phenyl)iodonium salts form a dimeric hypervalent iodine(iii) complex, oxyphenyl(phenyl)iodonium ylidic salt, the solid structure of which was confirmed by X-ray crystallography. Phenolic iodonium salts are potentially useful phenol transfer reagents in reactions with various anionic nucleophiles.

Full text of DOI:10.1039/C8CC06211K

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: A. Yoshimura, M.
T. Shea, O. Guselnikova, P. S. Postnikov, G. T. Rohde, A. Saito, M. S. Yusubov, V. Nemykin and V. V.
Zhdankin, Chem. Commun., 2018, DOI: 10.1039/C8CC06211K.
This is an Accepted Manuscript, which has been through the
Volume 52 Number
1 4 January 2016 Pages 1–216
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Accepted Manuscripts are published online shortly after
Chemical Communications
www.rsc.org/chemcomm
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
=
3
rsc.li/chemcomm

Please do not adjust margins
ChemComm
Page 1 of 5
View Article Online
DOI: 10.1039/C8CC06211K
Journal Name
COMMUNICATION
Preparation and Structure of Phenolic Aryliodonium Salts
Akira Yoshimura,*a,b Michael T. Shea,b Olga Guselnikova,a Pavel S. Postnikov,a Gregory T. Rohde,c
Akio Saito,d Mekhman S. Yusubov,a Victor N. Nemykin,e and Viktor V. Zhdankin*b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
Phenol based aryliodonium salts were prepared by the reaction of substrates under strongly basic conditions produce the
[hydroxy(tosyloxy)iodo]arenes with arylsilyl ethers in the corresponding benzyne adducts.12-14 Recently, diaryliodonium
presence of trifluoromethanesulfonic acid. Structures of several compounds with silyl or boron-containing substituents have
aryliodonium salts with the hydroxy group in para-position of been developed and used as efficient precursors to reactive
phenyl ring were established by single crystal X-ray species.15-17 For example, Kitamura and co-workers reported
crystallography.
Under
basic
condition,
4- the preparation and reactivity of [2,5-bis(trimethylsilyl)-4-
hydroxyphenyl(phenyl)iodonium salts form a dimeric hypervalent (triflyloxy)phenyl](phenyl)iodonium triflate, which could be
iodine(III) complex, oxyphenyl(phenyl)iodonium ylidic salt, the used as the 1,4-benzdiyne equivalent in the presence of
solid structure of which was confirmed by X-ray crystallography. fluoride source.15 Legault group has reported zwitterionic
Phenolic iodonium salts are potentially useful phenol transfer iodonium trifluoroborates which react with phenols under
reagents in reactions with various anionic nucleophiles.
basic condition forming the corresponding arylation products
containing trifluoroborate group in the aryl group.16 Our group
has reported the preparation and structural investigation of
novel benzyne precursors, pseudocyclic arylbenziodoxaborole
triflates, which could react with various substrates in the
presence of water to give the respective benzyne adducts in
moderate to good yields.17 Despite a significant current
interest in functionalized diaryliodonium compounds, only few
examples of phenol-derived aryliodonum salts have been
reported.18-22 Moreover, most of these examples deal with the
ortho-hydroxy substituted diaryliodonium salts, which are
important precursors to phenolic iodonium ylides. To the best
of our knowledge, only single example of the para-hydroxy
substituted diaryliodonium salt was reported in the
literature,18 and general synthetic procedures for the
preparation of phenolic iodonum salts have been not
established.
In recent years, organohypervalent iodine compounds have
found a broad range of applications in organic chemistry
because of their environmentally benign nature, oxidative
ability similar to heavy metal oxidants, and the reactivity
pattern similar to transition metals.1-5 Diaryliodonium salts
belong to a particularly important class of organohypervalent
iodine(III) compounds, which have numerous synthetic
applications under metal or metal-free conditions.6-8
Symmetrical or unsymmetrical diaryliodonium salts are
effective electrophilic arylating reagents whose reactions with
various organic nucleophilic substrates involve oxidative
transfer of aryl groups resulting in the formation of new aryl-
carbon atom bonds, aryl-heteroatom bonds, and aryl-
radioactive isotope bonds. Diaryliodonium salts can also serve
as efficient benzyne precursors under appropriate conditions.9-
11
In particular, reactions of diaryliodonium salts with various
Herein, we report a straightforward one-pot synthesis and
structural investigation of para-hydroxy substituted
diaryliodonium salts, which can be prepared starting from the
corresponding hypervalent iodine(III) reagents
and
of
triisopropylsiloxybenzene
trifluoromethanesulfonic
in
the
presence
obtained
acid.
The
para-
hydroxyphenyl(phenyl)iodonium
bromide under basic
conditions can be converted to a novel dimeric hypervalent
iodine(III) complex, oxyphenyl(phenyl)iodonium ylidic salt,
solid structure of which was confirmed by X-ray
crystallography.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 5
View Article Online
DOI: 10.1039/C8CC06211K
COMMUNICATION
Journal Name
d
Our approach to the one-pot synthesis of
hydroxyphenyl(aryl)iodonium salts is based on the reaction of
various hypervalent iodine(III) reagents with phenyl silyl ethers
involving the initial formation of silyloxyphenyl(aryl)iodonium
salts followed by desilylation of intermediate product in the
presence of trifluoromethanesulfonic acid (TfOH) to produce
the desired hydroxyphenyl(aryl)iodonium salts. In our initial
experiment, the reaction of Koser's reagent 2a and
triisopropylsiloxybenzene 1a in 2,2,2-trifluoroethanol (TFE)
gave the 4-triisopropylsiloxyphenyl(phenyl)iodonium tosylate
3a (R = TIPS; L = OTs) in 87% yield (Table 1, entry 1). Without
6
1e/H
1a
2a
–
7
2b/PhI(OAc)2,
4a 22%
4a 96%
4a 32%
4a 35%
4b 86%
4c 83%
8
1a
2c/PhI(OCOCF3)2
9
1a
2d/PhIO
2a
10e
11f
12g
1a
1a
2a
1a
2a
a All reactions were performed using substrate 1 (1.2 equiv.) and hypervalent iodine
reagent 2 (1 equiv.) in 2,2,2-trifluoroethanol at room temperature for 24 hours. The
purification, the initial compound
3 was transformed to the
desired 4-hydroxyphenyl(phenyl)iodonium triflate 4a in 97% reaction mixture was evaporated and then TfOH (1.5 equiv.) was added to the reaction
mixture in acetonitrile solution and stirred at 0 °C for 2 hours. b Yields of isolated
yield by treatment with TfOH in acetonitrile at 0 °C (entry 2).
products. c No TfOH added in the reaction mixture and isolated as 3a (R = TIPS; L = OTs).
d Complex mixture. e TfOH (1.5 equiv.) was added from the beginning. f p-TsOH·H2O (3.0
equiv.) was used instead of TfOH and stirred for 24 hours. g KBr (10.0 equiv.) was added
to the reaction mixture and stirred for 2 hours.
The structure of 4a was confirmed by NMR, elemental analysis,
and high-resolution ESI mass spectrometry. Reactions of other
phenyl silyl ethers protected with tert-butyldimethylsilyl group
(TBDMS) 1b or tert-butyldiphenylsilyl group (TBDPS) 1c under
similar conditions gave the corresponding phenolic iodonium
triflate 4a in 65-83% yields (entries 3 and 4). However, the
reaction of trimethylsiloxybenzene 1d or phenol 1e instead of
1a using Koser's reagent 2a did not afford the desired product
(entries 5 and 6). Screening of other hypervalent iodine(III)
reagents 2b-d has indicated that the Koser's reagent 2a and
[bis(trifluoroacetoxy)iodo]benzene 2c are the most effective
reagents in this reaction (entries 2, 7-9). Since
[hydroxy(tosyloxy)iodo]arenes are readily available and stable
compounds, we decided to use these reagents in our following
studies. The reaction in the presence of TfOH added from the
beginning gave product 4a in only 35% yield (entry 10). The
tosylate product 4b was obtained in 86% yield when p-
toluenesulfonic acid was used instead of TfOH (entry 11). The
triflate product 4a could be further converted into the 4-
hydroxyphenyl(phenyl)iodonium bromide 4c by treatment
with the aqueous potassium bromide solution at room
temperature (entry 12). The bromide 4c was recrystallized
from methanol, and characterized by X-ray crystallography
(Figure 1).
Figure 1. X-ray crystal structure of compound 4c. All non-oxygen hydrogen atoms
were removed for clarity. Ellipsoids drawn to the 50% probability level. Selected
bond lengths and angles: I(1)-C(1) 2.094(13); I(1)-C(7) 2.137(11); I(1)-Br(1)
3.277(2); O(1)-C(4) 1.379(15); I(1)-Br(1’) 3.280(1); C(1)-I(1)-C(7) 92.7(4); C(1)-I(1)-
Br(1) 86.8(3); Br(1)-I(1)-Br(1’) 89.9(1); Br(1’)-I(1)-C(7) 90.5(2). Br(1’) is located in
the neighboring asymmetric unit (Figure S1).
According to the X-ray crystallography data, compound 4c
has a pseudo-square-planar coordination formed by two
covalent iodine-carbon bonds and two close contact bromide
anions, with one of the bromide anions in the neighboring
asymmetric unit (Br1’). The I•••Br non-covalent
intermolecular interaction distances were 3.277(2) and
3.280(1) with angles nearly 90° between the iodine atom and
the four contacts (Figure S1). Additionally, a least-squares
plane fit through I1, C1, C7, Br1 and Br1’ resulted in a root-
mean square deviation of 0.029 Å. The bond angles and bond
distances of C–I–C are similar to the previously reported
structure of diaryliodonium salts.23 The bond distance between
oxygen and carbon atoms falls within the typical range for a
phenolic C–O bond length.
Table 1. Optimization of preparation of 4-hydroxyphenyl(phenyl)iodonium salts
4a
a
.
At the next step, we investigated the preparation of
various substituted 4-hydroxyphenyl(aryl)iodonium triflates
from the corresponding [hydroxy(tosyloxy)iodo]arenes under
optimized conditions. In general, the reaction of reagents
bearing electron-withdrawing or electron-donating
6
5
5
Entry
1/R
2/PhI(III)
4 (%)b
substituents in para-position with phenyl silyl ether 1a gave
the corresponding 4-hydroxyphenyl(aryl)iodonium triflates 6a-i
in moderate to good yields. In the reaction of sterically
hindered ortho-substituted [hydroxy(tosyloxy)iodo]arenes 5c,e
with 1a, the desired products 6c,e were also obtained in good
yields. However, the reaction of para-methoxy substituted
reagent 5g afforded product 6g only in 29% yield probably
1
2
3
4
5
1a/TIPS
1a
2a/PhI(OH)OTs
(3a 87%)c
4a 97%
4a 83%
4a 65%
2a
2a
2a
2a
1b/TBDMS
1c/TBDPS
1d/TMS
d
–
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 3 of 5
View Article Online
DOI: 10.1039/C8CC06211K
Journal Name
COMMUNICATION
because this reagent was a relatively unstable compound that reaction. Under same conditions, asymmetrical compound 8d
decomposed during the reaction.24 In the reaction of 2-thienyl was prepared in 68% from
(5j) or 3-thienyl (5k) Koser's type reagents with 1a, the
respective phenolic (thienyl)iodonium triflates 6j,k were
obtained in moderate yields. The bromide salt of 6k was also
prepared in 46% yield. The structures of phenolic
(thienyl)iodonium salts 6j-l were established by X-ray
crystallography (see supporting information). Molecular
arrangements in these structures are similar to the previously
7 with 1f.
Scheme 1. Preparation of 4,4'-di(hydroxyphenyl)iodonium salts 8a-d
.
reported aryl(thienyl)iodonium salts.25,26 The reaction of
pseudocyclic Koser's reagent, 2-
Phenolic (aryl)iodonium salts have the acidic hydroxyl
group on the aromatic ring. Previously, several research
groups reported that ortho-phenolic iodonium salts could be
converted to the corresponding aryliodonium ylides under
basic conditions.19,21 Thus, we investigated the preparation of
aryliodonim ylide from phenolic salt 4c under basic conditions.
The reaction of 4-hydroxyphenyl(phenyl)iodonium bromide 4c
with aqueous potassium carbonate at room temperature for 1
hour afforded the dimeric oxyphenyl(phenyl)iodonium ylide–
HBr complex 9a in 62% yield (Scheme 2). The reaction mixture
was stirred for 24 hours to give the respective potassium
bromide complex 9b in 86% yield. However, reaction of triflate
[hydroxy(tosyloxy)]iodobenzoic acid 5l, with 1a under the
same conditions gave the corresponding 1-(4-hydroxyphenyl)-
benziodoxole
6m in 74% yield. Compound 6m was
recrystallized from methanol and characterized by X-ray
crystallography (see supporting information). The reaction of
substituted aryl silyl ether 1f or 1g with 2a or 3e gave the
corresponding phenolic iodonium triflates 6n-p in good yields.
a,b
Table 2. Preparation of 4-hydroxyphenyl(aryl)iodonium salts 6a-o
.
4a, tosylate 4b, or symmetrical diphenolic iodonium salts
under similar conditions did not produce the respective
product. The composition of compounds was confirmed by
7
9
elemental analysis. The solid structure of 9a was established
by X-ray crystallography (Figure 2).
Scheme 2. Preparation of dimeric oxyphenyl(phenyl)iodonium ylides 9a,b
.
Figure 2. X-ray crystal structure of compound 9a. Non-oxygen hydrogen atoms
were removed for clarity. Ellipsoids drawn to the 50% probability level. Selected
bond lengths and angles: I(1)-C(1) 2.108(2); I(1)-C(7) 2.106(2); I(1)-Br(1)
3.3076(3); O(1’)-I(1) 2.760(2); C(1)-I(1)-C(7) 93.33(8); C(1)-I(1)-O(1’) 85.93(6);
C(7)-I(1)-Br(1) 81.84(6); O(1’)-I(1)-Br(1) 98.71(3). O(1’) is located in the
neighboring asymmetric unit (Figure S6).
a All reactions were performed using substrate 1 (1.2 equiv.) and hypervalent iodine
reagent 3 (1 equiv.) in 2,2,2-trifluoroethanol at room temperature for 24 hours. The
reaction mixture was evaporated and then TfOH (1.5 equiv.) was added to the reaction
mixture in acetonitrile solution and stirred at 0 °C for 2 hours. b Yields of isolated
products. c KBr (10.0 equiv.) was added to the reaction mixture and stirred for 2 hours.
According to the X-ray crystallography data, compound 9a
has a pseudo-square-planar coordination formed by two
covalent I–C bonds and two non-covalent intermolecular
interactions: an I•••Br interation at 3.3076(3) Å atom and an
I•••O interaction from a neighboring asymmetric unit at
2.760(2) Å (Figure S6). The C–I–C bond angle is close to the
expected T-sharped geometry of diaryliodonium salts or
iodonium zwitterion compounds.
Furthermore, we investigated the preparation of
symmetrical
diphenolic
iodonium
salts,
from
4-
acetoxy[hydroxy(tosyloxy)iodo]benzene
7
with
triisopropylsiloxybenzene 1a (Scheme 1). The reaction of
reagent with 1a under similar conditions afforded 4,4'-
di(hydroxyphenyl)iodonium triflate 8a in 94% yield. Other
diphenolic iodonium derivatives, tosylate 8b or bromide 8c
7
,
could be produced in moderate yields via ligand exchange
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 5
View Article Online
DOI: 10.1039/C8CC06211K
COMMUNICATION
Journal Name
Finally, we investigated the reactivity of
a
phenolic
5. A. Yoshimura and V. V. Zhdankin, Chem. Rev., 2016,
116, 3328-3435.
iodonium salt as
a phenol transfer reagent. Previously,
Olofsson and co-workers reported that the reaction of sodium
nitrite with diaryliodonium salts under weakly basic conditions
afforded the respective nitroarenes in good yields.27 Thus, we
tested the reactivity of the phenolic (aryl)iodonium salt as a
phenol transfer reagent (Scheme 3). The reaction of sodium
nitrite with 8a in the presence of NaOTf gave para-nitrophenol
10 in 46% yield. Reactions of other anionic nucleophiles with
8a under similar conditions gave respective compounds 11-14
in low to good yield. The obtained azide 11 is potentially useful
as a click chemistry synthone.28,29
6. V. W. Pike, J. Labelled Compd. Radiopharm., 2018, 61
196-227.
,
7. M. Fananas-Mastral, Synthesis, 2017, 49, 1905-1930.
8. E. A. Merritt and B. Olofsson, Angew. Chem., Int. Ed.,
2009, 48, 9052-9070.
9. A. Yoshimura, A. Saito and V. Zhdankin, Chem. - Eur. J.,
2018, in press. DOI: 10.1002/chem.201802111
10. D. R. Stuart, Synlett, 2017, 28, 275-279.
11. T. Kitamura, Aust. J. Chem., 2010, 63, 987-1001.
12. S. K. Sundalam, A. Nilova, T. L. Seidl and D. R. Stuart,
Angew. Chem., Int. Ed., 2016, 55, 8431-8434.
13. M. Wang and Z. Huang, Org. Biomol. Chem., 2016, 14
10185-10188.
,
14. H. Chen, J. Han, L. Wang and J. Han, Beilstein J. Org.
Chem., 2018, 14, 354-363.
15. T. Kitamura, K. Gondo and J. Oyamada, J. Am. Chem.
Soc., 2017, 139, 8416-8419.
Scheme 3. Phenolation reactions of various nucleophiles using 8a
.
16. R. Robidas, V. Guerin, L. Provencal, M. Echeverria and
C. Y. Legault, Org. Lett., 2017, 19, 6420-6423.
17. A. Yoshimura, J. M. Fuchs, K. R. Middleton, A. V.
Maskaev, G. T. Rohde, A. Saito, P. S. Postnikov, M. S.
Yusubov, V. N. Nemykin and V. V. Zhdankin, Chem. -
Eur. J., 2017, 23, 16738-16742.
In summary, we have reported
synthetic procedure for the preparation of 4-
hydroxyphenyl(aryl)iodonium salts from
a practical one-pot
triisopropylsiloxybenzene using hydroxy(tosyloxy)iodoarenes
in the presence of TfOH. Several solid-state structures of these
products were established by X-ray crystallography. These
phenolic diaryliodonium salts are potentially important
precursors of novel hypervalent iodine(III) ylidic compounds. In
particular, treatment of 4-hydroxyphenyl(phenyl)iodonium
salts under basic conditions converts them to dimeric
oxyphenyl(phenyl)iodonium ylidic salts. We have also
demonstrated that the symmetrical bis(phenolic)iodonium salt
is a potentially useful electrophilic phenol transfer reagent.
This work was supported by the grant of the Russian
Science Foundation (RSF-16-13-10081), the grant of the Tomsk
Polytechnic University Competitiveness Enhancement Program
(VIU-195/2018), the National Science Foundation (CHE-
1759798) and the JSPS Fund for the Promotion of Joint
International Research (Grant No 16KK0199).
18. F. M. Beringer and I. Lillien, J. Am. Chem. Soc., 1960, 82
725-731.
,
19. S. W. Page, E. P. Mazzola, A. D. Mighell, V. L. Himes and
C. R. Hubbard, J. Am. Chem. Soc., 1979, 101, 5858-
5860.
20. P. B. Kokil and P. M. Nair, Tetrahedron Lett., 1977,
4113-4116.
21. O. Prakash, M. Kumar and R. Kumar, Tetrahedron,
2010, 66, 5827-5832.
22. E. Malamidou-Xenikaki and S. Spyroudis, Synlett, 2008,
2725-2740.
23. M. S. Yusubov, D. Y. Svitich, A. Yoshimura, B. J. Kastern,
V. N. Nemykin and V. V. Zhdankin, Eur. J. Org. Chem.,
2015, 4831-4834.
24. I. Papoutsis, S. Spyroudis, A. Varvoglis and C. P.
Raptopoulou, Tetrahedron, 1997, 53, 6097-6112.
25. D. Bykowski, R. McDonald, R. J. Hinkle and R. R.
Tykwinski, J. Org. Chem., 2002, 67, 2798-2804.
26. R. R. Tykwinski, K. Kamada, D. Bykowski, K. Ohta and R.
McDonald, Adv. Mater., 2000, 12, 133-137.
27. G. L. Tolnai, U. J. Nilsson and B. Olofsson, Angew.
Chem., Int. Ed., 2016, 55, 11226-11230.
Conflicts of interest
There are no conflicts to declare.
Notes and references
28. A. Baschieri, S. Muzzioli, V. Fiorini, E. Matteucci, M.
Massi, L. Sambri and S. Stagni, Organometallics, 2014,
1. T. Wirth, Ed., Top. Curr. Chem., 2016, 373, 1-310.
2. V. V. Zhdankin, Hypervalent Iodine Chemistry:
Preparation, Structure and Synthetic Application of
Polyvalent Iodine Compounds, John Wiley & Sons Ltd,
2014.
33, 6154-6164.
29. V. E. Romanov and E. E. Shul'ts, Chem. Nat. Compd.,
2015, 51, 1142-1146.
3. T. Kaiho, Ed., Iodine Chemistry and Applications, John
Wiley & Sons, Inc., 2015.
4. T. Dohi and Y. Kita, Curr. Org. Chem., 2016, 20, 580-
615.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 5
ChemComm
View Article Online
DOI: 10.1039/C8CC06211K
OH
OTips
R
Nucleophile
NaOTf
1) ArI(OH)OTs
2) TfOH
then ligand source
Nu
_
L
–
–
+
+
+
I
I
O
O
I
R
Ar
Ph
+
M
aq K2CO3
Ph
–
OH
23 examples
29-97%
Br
para-hydroxy- and oxy-phenyl(aryl)iodonium salts were prepared and structurally characterized by X-ray crystallography.