Synthesis of ionic-liquid-supported diaryliodonium salts

Article abstract of DOI:10.1002/ejoc.201301920

The synthesis of ionic-liquid-supported diaryliodonium salts is described. The synthesis is simple and practical, and the ionic liquid products require no chromatographic purification. The ionic-liquid-supported diaryliodonium salts are quite stable, and they did not show any sign of decomposition or loss of reactivity, even after being stored for one month at 5 °C. The reactivity of these salts was explored in the phenylation of substituted phenols and carboxylic acids, and the corresponding diaryl ethers and aryl esters, respectively, were synthesized in good to excellent yields and with high purities.

Full text of DOI:10.1002/ejoc.201301920

FULL PAPER
DOI: 10.1002/ejoc.201301920
Synthesis of Ionic-Liquid-Supported Diaryliodonium Salts
Manoj Kumar Muthyala,[a][‡] Sunita Choudhary,[a][‡] Khima Pandey,[a] Ganesh M. Shelke,[a,b]
Mukund Jha,[b] and Anil Kumar*[a]
Keywords: Ionic liquids / Hypervalent compounds / Iodine / Supported reagents / Arylation
The synthesis of ionic-liquid-supported diaryliodonium salts
is described. The synthesis is simple and practical, and the
ionic liquid products require no chromatographic purifica-
tion. The ionic-liquid-supported diaryliodonium salts are
quite stable, and they did not show any sign of decomposi-
tion or loss of reactivity, even after being stored for one
month at 5 °C. The reactivity of these salts was explored in
the phenylation of substituted phenols and carboxylic acids,
and the corresponding diaryl ethers and aryl esters, respec-
tively, were synthesized in good to excellent yields and with
high purities.
reagents[8] also suffers from low loading capacity, long reac-
tion times, multistep synthesis, the inability to monitor the
reaction by various analytical techniques, and a paucity of
literature reports.
Introduction
Diaryliodonium salts[1] serve as efficient and powerful
electrophilic arylating agents for carbon–carbon[2] and
carbon–heteroatom[3] bond-forming reactions under both
metal-free and metal-catalysed conditions, due to their high
electron-deficiency and their ability to act as hyper leaving
groups. Recently, diaryliodonium salts have been used in
multicomponent cascade annulations[4] for the synthesis of
diverse heterocyclic compounds. These salts have also been
used as aryl sources in the enantioselective generation of
“α-carbonyl benzylic sterocentres” in the presence of chiral
catalysts.[5] Symmetrical diaryliodonium salts are generally
preferred over unsymmetrical salts to avoid chemoselectiv-
ity problems, but electron-rich and electron-poor symmetri-
cal diaryliodonium salts are not straightforward to synthe-
size. In addition, following this strategy, an expensive aryl
iodide moiety is generated as waste, which renders this ap-
proach less attractive. In contrast, it is easier to synthesize
unsymmetrical salts[1d,6] than the corresponding symmetri-
cal salts, but controlling the chemoselectivity of the reac-
tions of these unsymmetrical salts, and purification of the
reaction products, are major concerns. Moreover, every now
and then the possibility arises that the aryl iodide by-prod-
uct interferes with the desired reaction products, which
causes severe purification problems.[7] Furthermore, some
aryl iodides are very hard to recover and reuse. An alterna-
tive approach using polymer-supported diaryliodonium
Ionic-liquid-supported reagents are a unique class of
supported reagents with distinctive chemical and physical
properties. They offer several advantages for organic syn-
thesis: they offer the same superior product isolation and
purification as is seen with solid-phase chemistry, along
with the benefits of traditional solution-phase synthesis.[9]
Several ionic-liquid-supported reagents, including hyperva-
lent iodine reagents,[10] have been synthesized and used for
different organic transformations. These reagents showed
comparable reactivity to the corresponding unsupported
reagents, and also, the biphasic system offered the advan-
tage of simple product isolation with high purity. To date,
no report on ionic-liquid-supported diaryliodonium salts is
available in the literature. Consequently, there is a need to
develop ionic-liquid-supported diaryliodonium salts to deal
with the purification, isolation, and loading problems asso-
ciated with diaryliodonium salts. Our interest in ionic-li-
quid-supported reagents,[11] along with the synthetic utility
of diaryliodonium salts, prompted us to pursue a project
devoted to the synthesis of ionic-liquid-supported diaryl-
iodonium salts. In this paper, we wish to report the synthe-
sis of ionic-liquid-supported diaryliodonium salts. To the
best of our knowledge, this is first attempt at the synthesis
of ion-tagged diaryliodonium salts.
[a] Department of Chemistry, Birla Institute of Technology and
Science, Pilani
Results and Discussion
Pilani 333031, India
E-mail: anilkumar@pilani.bits-pilani.ac.in
http://www.bits-pilani.ac.in/pilani/anilkumar/profile
[b] Department of Biology and Chemistry, Nipissing University,
North Bay, ON, P1B 8L7, Canada
We envisioned that tagging electron-rich aryl groups to
an ionic liquid would facilitate the synthesis of ionic-liquid-
supported diaryliodonium salts. Thus, two electron-rich
aryl-functionalized ionic liquids 4 and 5 were synthesized
as shown in Scheme 1. Alkoxy tosylates 2 and 3 were pre-
[‡] Both authors contributed equally.
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201301920.
Eur. J. Org. Chem. 2014, 2365–2370
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. Kumar et al.
FULL PAPER
Scheme 1. Synthesis of various ionic-liquid-supported aryls.
pared from phenol and thiophene-2-carbaldehyde (see Sup- Table 1. Preparation of ionic-liquid-supported diaryliodonium salts
from 4 and 5.
porting Information). Reaction of 2 and 3 with 1,2-dimeth-
ylimidazole (1) at 80 °C gave the corresponding imid-
azolium-supported aryls (i.e., 4 and 5) in excellent yields
(95–96%). Simply washing the ionic-liquid layer with an
ethyl acetate/hexane mixture (1:1 v/v) followed by drying
under vacuum gave the pure products. The NMR spectro-
scopic data and MS data of the synthesized ionic liquids
were consistent with the structures of 4 and 5.
Entry Ar
ArЈ
Product
Yield [%]
Based on Pike’s[6a] and Kita’s[6b] work on the synthesis
of unsymmetrical iodonium salts, we anticipated that the
reaction of imidazolium-supported aryls with [hydroxy(tos-
yloxy)iodo]arenes (HTIA) or (diacetoxyiodo)arenes would
lead to the corresponding ionic-liquid-supported diaryl-
iodonium salts. Initial attempts to synthesize ionic-liquid-
supported diaryliodonium salts were made by the reaction
of 4 with HTIB (6a) in CHCl3 at room temperature, but
this did not result in the formation of the expected product
(i.e., 8a). However, when the same reaction mixture was
heated to reflux temperature, the desired product (i.e., 8a)
was formed in good yield. Decanting the solvent CHCl3,
followed by washing with tetrahydrofuran gave the product
in a quite pure form, without the need for any chromato-
graphic purification. For unsupported diaryliodonium salts,
in most cases, column chromatography is obligatory for pu-
rification.[12]
1
2
3
4
5
6
7
8
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
C6H5
2,4,6-(CH3)3C6H2
4-BrC6H4
4-(OCOPh)C6H4
4-(CO2CH3)C6H4
4-NO2C6H4
4-CH3C6H4
2-CH3C6H4
4-OCH3C6H4
C6H5
8a
8b
8c
8d
8e
8f
8g
8h
8i
9a
9c
9d
9e
9f
80[a]
72[a]
80[a]
85[a]
76[a]
72[a]
87[b]
86[b]
75[b]
72[a]
70[a]
76[a]
70[a]
68[a]
80[b]
77[b]
70[b]
67[b]
9
C6H5
10
11
12
13
14
15
16
17
18
2-C4H3S
2-C4H3S
2-C4H3S
2-C4H3S
2-C4H3S
2-C4H3S
2-C4H3S
2-C4H3S
2-C4H3S
4-BrC6H4
4-(OCOPh)C6H4
4-(CO2CH3)C6H4
4-NO2C6H4
4-CH3C6H4
2-CH3C6H4
4-OCH3C6H4
2-OCH3C6H4
9g
9h
9i
9j
[a] Reagents and reaction conditions; Method A: 4 or 5 (1.0 mmol),
ArI(OH)(OTs) (1.0 mmol), CHCl3 (10 mL), 62 °C, 10 h.
[b] Method B: 4 or 5 (1.0 mmol), ArI(OAc)2 (1.0 mmol), pTSA
(1.0 mmol), CH3CN/CHCl3 (1:2, 10 mL), 70 °C, 12 h.
1
The structure of 8a was confirmed by H and 13C NMR
spectroscopy. The 1H NMR spectrum of 8a showed a char-
acteristic multiplet at δ = 8.15 ppm due to the ortho-protons
adjacent to the iodonium ion, and a singlet peak at δ =
3.71 ppm due to the N-methyl group, along with other pro-
Ionic-liquid-supported diaryliodonium salts 8 and 9
tons. In the 13C NMR spectrum, a peak at δ = 106 ppm could also be synthesized by the reaction of 4 and 5 with
due to the C–I carbon provides clear evidence for the struc- (diacetoxyiodo)arenes 7g–7j and p-toluenesulfonic acid
ture of iodonium salt 8a.
(pTSA) by generation of the corresponding HTIAs in situ.
Having established the reaction conditions for the syn- Generally, this approach is more useful for electron-rich
thesis of such ionic-liquid-supported iodonium salts, we iodoaryls, for which the synthesis of the corresponding
went on to examine the possibility of accessing unsymmet- HTIAs is difficult due to their instability. Thus, (diacetoxy-
rical ionic-liquid-supported iodonium salts by the reaction iodo)arenes 7g–7j were treated with 4 and 5 to give the cor-
of 4 and 5 with various functionalized HTIAs 6a–6f responding products 8g–8i and 9g–9j in good to excellent
(Table 1). Gratifyingly, both electron-releasing (6b) and yields (Table 1, entries 7–9, 15–18).
electron-withdrawing (6c–6f) groups were tolerated quite
well on the HTIAs to give the desired products (i.e., 8a–8f iodonium salts bearing functional groups such as bromo,
and 9a–9f) in good to excellent yields (Table 1). acetoxy, nitro, methyl, and methoxy were synthesized in
Different unsymmetrical ionic-liquid-supported diaryl-
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Eur. J. Org. Chem. 2014, 2365–2370

Synthesis of Ionic-Liquid-Supported Diaryliodonium Salts
Scheme 2. Phenylation of substituted phenols and carboxylic acids using ionic-liquid-supported diaryl iodonium salts 8a and 9a. Reagents
and reaction conditions: (a) 10aЈ–10cЈ (1 mmol), Cs2CO3 (1.5 mmol), THF (5 mL), 8a (1.1 mmol), 0–30 °C, 4 h; (b) 13dЈ–13fЈ (1 mmol),
tBuOK (1.5 mmol), 8a (1.1 mmol), dry toluene (5 mL), 110 °C, 3 h. (c) Yields of 12aЈ–12cЈ when 9a was used as arylating agent.
overall good to excellent yields (67–87%). In all cases, the be extracted with a hexane/ethyl acetate mixture. This leaves
products were purified by simply washing with THF (no behind the by-product supported on the ionic liquid. O-
chromatographic purification was required). The synthe- Arylation of phenols using 9a gave the desired products
sized ionic-liquid-supported diaryliodonium salts were (i.e., 12aЈ–12cЈ) in yields slightly lower than those obtained
characterized by NMR spectroscopy and mass spectrome- with 8a. The recovered ionic-liquid-supported iodophenyl
try (see Supporting Information). The yields of the diaryl- (i.e., 11; Scheme 2) can potentially be reused as a supported
iodonium salts were better starting from 4 than from 5, the reagent in many other organic transformations,[13] and can
latter of which uses thiophene as the aryl source. The sta- also serve as a starting material to synthesize ionic-liquid-
bility of these salts is particularly noteworthy. The synthe- supported hypervalent iodine reagents.[10]
sized ionic-liquid-supported diaryliodonium salts (i.e., 8
and 9) did not show any sign of decomposition or loss of
reactivity, even after storage for one month at 5 °C.
Conclusions
The direct electrophilic arylation of various nucleophiles
is a synthetically useful reaction of diaryliodonium salts. To
demonstrate the utility of the ionic-liquid-supported diaryl-
iodonium salts, we examined the O-arylation of substituted
phenols and acids under metal-free conditions (Scheme 2).
Initial attempts to optimize the reaction conditions for the
O-arylation of phenols using 8a were made using 4-
bromophenol (10aЈ) as a model substrate. When 10aЈ was
treated with potassium tert-butoxide at 0 °C, followed by
the addition of 8a at room temperature, 1-bromo-4-phen-
oxybenzene (12aЈ) was formed in 70% yield. After further
optimization of the reaction conditions for this transforma-
tion by varying solvents and bases, we found that the best
yields for this and other phenol starting materials were ob-
tained by using THF as solvent and Cs2CO3 as base. For
the similar arylation of carboxylic acid starting materials,
the best yields were obtained by using toluene as solvent
and tBuOK as base.
Having established standard reaction conditions, we set
out to survey a range of phenols 10aЈ–10cЈ and carboxylic
acids 13dЈ–13fЈ towards O-arylation (Scheme 2). Interest-
ingly, both phenols and carboxylic acids reacted smoothly
with 8a to give the corresponding diaryl ethers (i.e., 12) and
aryl esters (i.e., 14), respectively, in good to excellent yields
(70–85%). A significant advantage of this protocol is that
the products are obtained in excellent purity without the
need for chromatographic purification. After completion of
In summary, we have designed and synthesized ionic-li-
quid-supported diaryliodonium salts. The ionic-liquid-sup-
ported diaryliodonium salts were prepared by two ap-
proaches: i) using HTIAs; and ii) using (diacetoxyiodo)-
arenes and p-toluenesulfonic acid, where the HTIAs were
generated in situ. One of the salient features of this protocol
is that chromatographic purification is avoided. The electro-
philic phenylation of phenols and carboxylic acids by ionic-
liquid-supported diaryliodonium salt 8a was demonstrated,
and the products were purified by simple extraction with a
hexane/ethyl acetate mixture. The by-product of the reac-
tion, ionic-liquid-supported iodophenyl 11, was easily iso-
lated, and can be further reused as a reagent in different
organic transformations.[13]
Experimental Section
General Remarks: NMR spectra were recorded with 300 and
400 MHz spectrometers using CDCl3 and [D6]DMSO as solvents.
Chemical shifts are expressed in ppm. The purity of the products
was determined by TLC, carried out on silica-coated aluminum
plates. Melting points were determined using open capillary tubes
and an automated melting-point apparatus. 1,2-Dimethylimidazole,
aryl iodides, and other reagents and solvents were purchased from
commercial suppliers, and were used without further purification
unless otherwise specified.
General Procedure for the Synthesis of Ionic-Liquid-Supported Di-
the reaction, the solvent is evaporated, and the product can aryliodonium Salts 8a–8f and 9a–9f from Various HTIA (Method
Eur. J. Org. Chem. 2014, 2365–2370
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A. Kumar et al.
FULL PAPER
A): HTIA (1.0 mmol) was added to the ionic-liquid-supported ar-
ene 4 or 5 (1.0 mmol) in CHCl3 (10 mL), and the resulting reaction
mixture was heated at reflux for 10 h. The progress of the reaction
was monitored by TLC. After the reaction was complete, the
CHCl3 was decanted, and the crude product was washed with THF
(3ϫ 5 mL) to remove unreacted starting materials. The resulting
compound was dried under reduced pressure to give the desired
product. The purity of the compounds was adequate, and further
purification by column chromatography was not required.
2.53 (s, 3 H), 2.28 (s, 6 H), 2.22–2.25 (m, 2 H) ppm. 13C NMR
(75 MHz, [D6]DMSO): δ = 161.5, 149.7, 146.1, 144.9, 138.1, 138.1,
136.6, 128.5, 126.5, 125.9, 123.7, 122.8, 121.4, 118.4, 106.5, 65.3,
45.1, 35.1, 28.9, 21.2, 9.6 ppm.
9a: Yellow viscous liquid (562 mg, 72%). 1H NMR (300 MHz, [D6]-
DMSO): δ = 8.24 (d, J = 7.7 Hz, 2 H), 7.94 (d, J = 3.7 Hz, 1 H),
7.70–7.51 (m, 5 H), 7.48 (d, J = 8.0 Hz, 4 H), 7.11 (d, J = 7.8 Hz,
4 H), 7.04 (d, J = 3.6 Hz, 1 H), 4.74 (s, 2 H), 4.33 (t, J = 4.6 Hz,
2 H), 3.79–3.65 (m, 5 H), 2.53 (s, 3 H), 2.28 (s, 6 H) ppm. 13C
NMR (75 MHz, [D6]DMSO): δ = 152.2, 146.0, 145.2, 140.5, 138.2,
135.1, 132.5, 132.1, 128.6, 128.4, 125.9, 122.7, 121.7, 119.9, 100.7,
8a: White solid (648 mg, 80%), m.p. 149–157 °C. 1H NMR
(300 MHz, [D6]DMSO): δ = 8.28–8.09 (m, 4 H), 7.65 (d, J =
2.1 Hz, 1 H), 7.63 (d, J = 7.4 Hz, 1 H), 7.60 (d, J = 2.0 Hz, 1 H), 68.5, 66.8, 47.8, 35.2, 21.2, 9.8 ppm.
7.51 (d, J = 8.0 Hz, 2 H), 7.48 (d, J = 8.1 Hz, 4 H), 7.10 (d, J =
9c: Brown viscous liquid (602 mg, 70%). 1H NMR (300 MHz, [D6]-
7.9 Hz, 4 H), 7.03 (d, J = 9.1 Hz, 2 H), 4.25 (t, J = 6.9 Hz, 2 H),
4.03 (t, J = 5.9 Hz, 2 H), 3.71 (s, 3 H), 2.52 (s, 3 H), 2.28 (s, 6 H),
2.23–2.11 (m, 2 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ =
161.3, 146.1, 144.9, 138.1, 137.7, 135.3, 132.3, 132.1, 128.5, 125.9,
122.8, 121.4, 118.3, 117.5, 106.2, 65.3, 45.1, 35.1, 28.9, 21.2,
9.6 ppm.
DMSO): δ = 8.18 (d, J = 8.6 Hz, 2 H), 7.95 (d, J = 3.8 Hz, 1 H),
7.74 (d, J = 8.6 Hz, 2 H), 7.60 (d, J = 1.9 Hz, 1 H), 7.57 (d, J =
2.1 Hz, 1 H), 7.48 (d, J = 8.0 Hz, 4 H), 7.11 (d, J = 7.9 Hz, 4 H),
7.06 (d, J = 3.8 Hz, 1 H), 4.75 (s, 2 H), 4.34 (t, J = 4.8 Hz, 2 H),
3.79–3.70 (m, 5 H), 2.53 (s, 3 H), 2.28 (s, 6 H) ppm. 13C NMR
(75 MHz, [D6]DMSO): δ = 152.4, 146.0, 145.2, 140.7, 138.2, 137.1,
1
8b: Off-white viscous liquid (588 mg, 72%). H NMR (300 MHz, 135.0, 128.5, 128.4, 126.6, 125.9, 122.7, 121.7, 118.5, 101.0, 68.5,
[D6]DMSO): δ = 7.90 (d, J = 8.9 Hz, 2 H), 7.65 (d, J = 1.8 Hz, 1
H), 7.60 (d, J = 1.7 Hz, 1 H), 7.46 (d, J = 7.9 Hz, 4 H), 7.18 (s, 2
H), 7.10 (d, J = 7.8 Hz, 4 H), 7.00 (d, J = 8.9 Hz, 2 H), 4.25 (t, J
= 6.8 Hz, 2 H), 4.02 (t, J = 5.8 Hz, 2 H), 3.71 (s, 3 H), 2.59 (s, 6
H), 2.53 (s, 3 H), 2.28 (s, 9 H), 2.22–2.09 (m, 2 H) ppm. 13C NMR
(75 MHz, [D6]DMSO): δ = 161.0, 146.1, 144.9, 143.3, 141.8, 138.1,
137.0, 130.1, 128.5, 125.9, 123.6, 122.8, 121.4, 118.3, 104.1, 65.3,
55.4, 45.1, 35.1, 28.9, 26.7, 21.2, 20.9, 9.6 ppm.
66.8, 47.8, 35.2, 21.2, 9.8 ppm.
9d: Brown viscous liquid (685 mg, 76% yield). 1H NMR (300 MHz,
[D6]DMSO): δ = 8.36 (d, J = 7.9 Hz, 2 H), 8.11 (d, J = 7.4 Hz, 2
H), 7.98 (s, 1 H), 7.77 (t, J = 6.9 Hz, 1 H), 7.60 (dd, J = 15.5,
6.4 Hz, 4 H), 7.48 (d, J = 6.1 Hz, 6 H), 7.11 (d, J = 7.4 Hz, 4 H),
7.06 (d, J = 3.7 Hz, 1 H), 4.76 (s, 2 H), 4.31–4.37 (m, 2 H), 3.69–
3.79 (m, 5 H), 2.53 (s, 3 H), 2.27 (s, 6 H) ppm. 13C NMR (75 MHz,
[D6]DMSO): δ = 164.7, 153.7, 152.4, 145.9, 145.2, 140.7, 138.3,
136.9, 134.9, 130.4, 129.5, 128.8, 128.6, 128.4, 126.0, 125.9, 122.7,
121.7, 116.1, 101.0, 68.5, 66.9, 47.8, 35.2, 21.2, 9.8 ppm.
8c: White solid (683 mg, 80%), m.p. 152–159 °C. 1H NMR
(300 MHz, [D6]DMSO): δ = 8.18–8.15 (m, 4 H), 7.72 (d, J =
8.6 Hz, 2 H), 7.65 (d, J = 1.9 Hz, 1 H), 7.60 (d, J = 1.9 Hz, 1 H),
7.47 (d, J = 8.0 Hz, 4 H), 7.10 (d, J = 7.9 Hz, 4 H), 7.04 (d, J =
9.0 Hz, 2 H), 4.26 (t, J = 7.0 Hz, 2 H), 4.04 (t, J = 5.9 Hz, 2 H),
3.72 (s, 3 H), 2.53 (s, 3 H), 2.28 (s, 6 H), 2.12–2.10 (m, 2 H) ppm.
13C NMR (75 MHz, [D6]DMSO): δ = 161.3, 146.1, 144.9, 138.1,
137.7, 137.3, 134.9, 128.5, 126.41, 125.9, 122.8, 121.4, 118.3, 116.1,
106.5, 65.3, 45.1, 35.1, 28.9, 21.2, 9.6 ppm.
9e: White solid (587 mg, 70%), m.p. 170–173 °C. 1H NMR
(300 MHz, [D6]DMSO): δ = 8.36 (d, J = 8.4 Hz, 2 H), 8.03 (d, J
= 8.4 Hz, 2 H), 7.98 (d, J = 3.7 Hz, 1 H), 7.60 (d, J = 1.7 Hz, 1
H), 7.56 (d, J = 1.6 Hz, 1 H), 7.47 (d, J = 7.9 Hz, 4 H), 7.11 (d, J
= 7.8 Hz, 4 H), 7.07 (d, J = 4.0 Hz, 1 H), 4.76 (s, 2 H), 4.34 (t, J
= 4.6 Hz, 2 H), 3.87 (s, 3 H), 3.75–3.70 (m, 5 H), 2.54 (s, 3 H), 2.28
(s, 6 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 165.6, 160.0,
158.1, 152.6, 146.1, 145.2, 141.0, 138.1, 135.4, 133.0, 132.3, 128.5,
125.9, 124.5, 122.7, 121.7, 68.5, 66.9, 53.2, 47.8, 35.2, 21.2,
9.8 ppm.
8d: White solid (761 mg, 85%), m.p. 155–162 °C. 1H NMR
(300 MHz, [D6]DMSO): δ = 8.32 (d, J = 7.1 Hz, 2 H), 8.21 (d, J
= 6.9 Hz, 2 H), 8.11 (d, J = 5.5 Hz, 2 H), 7.82–7.72 (m, 1 H), 7.63
(d, J = 11.5 Hz, 4 H), 7.47 (d, J = 5.6 Hz, 6 H), 7.16–6.99 (m, 6
H), 4.33–4.19 (m, 2 H), 4.11–4.01 (m, 2 H), 3.71 (s, 3 H), 2.50 (s,
3 H), 2.27 (s, 6 H), 2.22–2.12 (m, 2 H) ppm. 13C NMR (75 MHz,
[D6]DMSO): δ = 164.7, 161.3, 153.6, 146.1, 144.9, 138.1, 137.7,
137.1, 134.9, 130.4, 129.5, 128.8, 128.5, 126.1, 125.9, 122.84, 121.4,
118.3, 113.8, 106.6, 65.3, 45.1, 35.1, 28.9, 21.2, 9.6 ppm.
9f: Pale brown viscous liquid (562 mg, 68% yield). 1H NMR
(300 MHz, [D6]DMSO): δ = 8.49 (d, J = 8.7 Hz, 2 H), 8.28 (d, J
= 8.7 Hz, 2 H), 8.02 (d, J = 3.6 Hz, 1 H), 7.63–7.60 (m, 1 H), 7.59–
7.55 (m, 1 H), 7.47 (d, J = 7.8 Hz, 4 H), 7.11 (d, J = 7.8 Hz, 4 H),
7.08–7.06 (m, 1 H), 4.76 (s, 2 H), 4.38–4.30 (m, 2 H), 3.75–3.70 (m,
5 H), 2.54 (s, 3 H), 2.28 (s, 6 H) ppm. 13C NMR (75 MHz, [D6]-
DMSO): δ = 152.9, 149.7, 146.0, 145.2, 141.3, 138.2, 136.4, 128.6,
8e: Brown viscous liquid (633 mg, 76%). 1H NMR (300 MHz, [D6]-
DMSO): δ = 8.32 (d, J = 7.8 Hz, 2 H), 8.20 (d, J = 8.0 Hz, 2 H), 128.5, 126.6, 125.9, 122.7, 121.7, 101.0, 68.6, 66.9, 47.8, 35.2, 21.2,
7.99 (d, J = 7.5 Hz, 2 H), 7.65 (d, J = 2.0 Hz, 1 H), 7.60 (d, J = 9.8 ppm.
2.0 Hz, 1 H), 7.48 (d, J = 7.1 Hz, 4 H), 7.10 (d, J = 7.2 Hz, 4 H),
General Procedure for the Synthesis of Ionic-Liquid-Supported Di-
7.05 (d, J = 8.3 Hz, 2 H), 4.26 (t, J = 7.0 Hz, 2 H), 4.04 (t, J =
aryliodonium Salts (8g–8i and 9g–9j) from Various (Diacetoxyiodo)-
5.9 Hz, 2 H), 3.86 (s, 3 H), 3.71 (s, 3 H), 2.53 (s, 3 H), 2.28 (s, 6
arenes (Method B): para-Toluenesulfonic acid (1.0 mmol) was
H), 2.23–2.11 (m,
2
H) ppm. 13C NMR (75 MHz, [D6]-
added to a suspension of (diacetoxyiodo)arene (1.0 mmol) in
MeCN (4.0 mL) to give an intensely yellow solution, which was
further diluted with CHCl3. Ionic-liquid-supported arene 4 or 5
(1.0 mmol) was added to the reaction mixture, and the resulting
pale yellow solution was heated at reflux for 12 h. After TLC indi-
cated that the reaction was complete, the solvent was evaporated.
DMSO): δ = 165.6, 161.4, 146.1, 144.9, 138.1, 137.9, 135.7, 132.8,
132.2, 128.5, 125.9, 122.8, 122.3, 121.4, 118.4, 106.2, 65.3, 53.2,
45.0, 35.1, 28.9, 21.2, 9.6 ppm.
8f: Pale brown viscous liquid (590 mg, 72%). 1H NMR (300 MHz,
[D6]DMSO): δ = 8.44 (d, J = 9.0 Hz, 2 H), 8.29–8.20 (m, 4 H),
7.65 (d, J = 2.0 Hz, 1 H), 7.60 (d, J = 2.0 Hz, 1 H), 7.47 (d, J = The residue was washed with diethyl ether (2ϫ 5 mL) and THF
8.0 Hz, 4 H), 7.10 (d, J = 7.9 Hz, 4 H), 7.06 (d, J = 9.1 Hz, 2 H), (3ϫ 5 mL), and then dried under reduced pressure to give the pure
4.26 (t, J = 7.0 Hz, 2 H), 4.05 (t, J = 5.9 Hz, 2 H), 3.72 (s, 3 H),
ionic-liquid-supported diaryliodonium salt.
2368
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 2365–2370

Synthesis of Ionic-Liquid-Supported Diaryliodonium Salts
8g: White solid (687 mg, 87%), m.p. 160–166 °C. 1H NMR
(300 MHz, [D6]DMSO): δ = 8.14–8.06 (m, 4 H), 7.65 (d, J =
General Procedure for O-Phenylation of Substituted Phenols: Substi-
tuted phenol 10 (1.0 mmol) was dissolved in THF (5.0 mL), and
2.2 Hz, 1 H), 7.60 (d, J = 2.1 Hz, 1 H), 7.48 (d, J = 8.1 Hz, 4 H), Cs2CO3 (1.5 mmol) was added slowly at 0 °C. The mixture was
7.31 (d, J = 8.2 Hz, 2 H), 7.10 (d, J = 7.8 Hz, 4 H), 7.02 (d, J = stirred for 20 min, then it was treated with ionic-liquid-supported
9.1 Hz, 2 H), 4.25 (t, J = 6.9 Hz, 2 H), 4.03 (t, J = 6.0 Hz, 2 H),
3.71 (s, 3 H), 2.52 (s, 3 H), 2.33 (s, 3 H), 2.28 (s, 6 H), 2.24–2.11
(m, 2 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 161.2, 146.2,
144.9, 142.7, 138.1, 137.6, 135.3, 132.7, 128.5, 125.9, 122.8, 121.4,
118.21, 113.9, 106.4, 65.3, 45.1, 35.1, 28.9, 21.3, 21.2, 9.6 ppm.
iodonium salt 8a or 9a (1.1 mmol). The resulting solution was
stirred at room temperature for 4 h. After the reaction was com-
plete, the THF was evaporated, and the product was extracted with
hexane/ethyl acetate (1:1 v/v). The organic phase was washed with
water, dried with anhydrous sodium sulfate, and concentrated to
give the desired product.
1
8h: Colourless viscous liquid (679 mg, 86%). H NMR (300 MHz,
12aЈ: Colourless liquid (211 mg, 85%). 1H NMR (300 MHz,
CDCl3): δ = 7.43 (d, J = 2.2 Hz, 1 H), 7.40 (d, J = 2.2 Hz, 1 H),
7.37–7.30 (m, 2 H), 7.12 (dt, J = 7.0, 1.08 Hz, 1 H), 7.01 (q, J =
1.8 Hz, 1 H), 6.99–6.97 (m, 1 H), 6.89 (d, J = 2.2 Hz, 1 H), 6.86
(d, J = 2.2 Hz, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 156.7,
156.6, 132.7, 129.9, 123.7, 120.4, 119.0, 115.6 ppm.
[D6]DMSO): δ = 8.36 (d, J = 7.9 Hz, 1 H), 8.12 (d, J = 8.9 Hz, 2
H), 7.65 (d, J = 2.0 Hz, 1 H), 7.60 (d, J = 2.0 Hz, 1 H), 7.54 (d, J
= 6.5 Hz, 2 H), 7.48 (d, J = 8.0 Hz, 4 H), 7.32–7.23 (m, 1 H), 7.10
(d, J = 7.9 Hz, 4 H), 7.00 (d, J = 9.0 Hz, 2 H), 4.25 (t, J = 6.8 Hz,
2 H), 4.02 (t, J = 5.9 Hz, 2 H), 3.70 (s, 3 H), 2.60 (s, 3 H), 2.51 (s,
3 H), 2.27 (s, 6 H), 2.22–2.09 (m, 2 H) ppm. 13C NMR (75 MHz,
[D6]DMSO): δ = 161.2, 146.0, 144.9, 140.8, 138.2, 137.57, 137.4,
133.1, 131.7, 129.6, 128. 6, 125.9, 122.8, 122.5, 121.4, 118.3, 105.6,
65.3, 45.0, 35.1, 28.9, 25.4, 21.2, 9.5 ppm.
12bЈ: Colourless liquid (121 mg, 75%). 1H NMR (300 MHz,
CDCl3): δ = 7.33 (t, J = 2.2 Hz, 1 H), 7.32–7.29 (m, 2 H), 7.29–
7.26 (m, 1 H), 7.10–7.04 (m, 2 H), 7.01 (t, J = 1.6 Hz, 2 H), 6.99–
6.97 (m, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 157.3, 129.8,
123.3, 119.0 ppm.
1
8i: Pale yellow viscous liquid (604 mg, 75%). H NMR (300 MHz,
[D6]DMSO): δ = 8.12 (d, J = 8.7 Hz, 4 H), 7.64 (s, 1 H), 7.59 (s, 1
H), 7.47 (d, J = 7.2 Hz, 4 H), 7.10 (d, J = 7.4 Hz, 4 H), 7.03 (t, J
= 7.9 Hz, 4 H), 4.25 (t, J = 6.5 Hz, 2 H), 4.09–3.94 (m, 2 H), 3.78
(s, 3 H), 3.71 (s, 3 H), 2.52 (s, 3 H), 2.27 (s, 6 H), 2.22–2.11 (m, 2
H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 162.3, 161.1, 146.1,
144.9, 138.1, 137.4, 137.4, 128.5, 125.9, 122.8, 121.4, 118.2, 117.8,
106.8, 106.5, 65.2, 56.2, 45.1, 35.1, 25.59, 21.2, 9.6 ppm.
9g: Pale brown viscous liquid (636 mg, 80%). 1H NMR (300 MHz,
[D6]DMSO): δ = 8.11 (d, J = 7.2 Hz, 2 H), 7.90 (s, 1 H), 7.57 (d,
J = 9.3 Hz, 2 H), 7.48 (d, J = 7.2 Hz, 4 H), 7.32 (d, J = 7.6 Hz, 2
H), 7.11 (d, J = 7.3 Hz, 4 H), 7.03 (s, 1 H), 4.73 (s, 2 H), 4.27–4.38
(m, 2 H), 3.81–3.67 (m, 5 H), 2.52 (s, 3 H), 2.33 (s, 3 H), 2.28 (s, 6
H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 152.0, 145.9, 145.2,
143.0, 140.3, 138.2, 135.1, 132.7, 128.6, 128.4, 125.9, 122.7, 121.7,
116.3, 100.9, 68.5, 66.8, 47.8, 35.2, 21.32, 21.2, 9.8 ppm.
9h: Pale brown viscous liquid (612 mg, 77% yield). 1H NMR
(300 MHz, [D6]DMSO): δ = 8.41 (d, J = 7.9 Hz, 1 H), 7.91 (d, J
= 3.8 Hz, 1 H), 7.60 (t, J = 2.5 Hz, 2 H), 7.57 (t, J = 2.5 Hz, 2 H),
7.47 (d, J = 8.0 Hz, 4 H), 7.35–7.28 (m, 1 H), 7.11 (d, J = 7.9 Hz,
4 H), 7.03 (d, J = 3.8 Hz, 1 H), 4.73 (s, 2 H), 4.33 (t, J = 4.9 Hz,
2 H), 3.75–3.72 (m, 5 H), 2.63 (s, 3 H), 2.53 (s, 3 H), 2.28 (s, 6 H)
ppm. 13C NMR (75 MHz, [D6]DMSO): δ = 151.9, 146.1, 145.2,
140.4, 140.2, 138.1, 137.2, 133.4, 131.9, 129.8, 128.5, 128.4, 125.9,
124.9, 122.7, 121.7, 100.1, 68.5, 66.8, 47.8, 35.2, 25.4, 21.2,
9.8 ppm.
12cЈ: White solid (149 mg, 70%), m.p. 70–72 °C. 1H NMR
(300 MHz, CDCl3): δ = 7.30–7.22 (m, 2 H), 7.04–6.96 (m, 1 H),
6.93 (t, J = 1.6 Hz, 1 H), 6.90 (dd, J = 3.1, 2.1 Hz, 1 H), 6.86 (s, 1
H), 6.81 (d, J = 1.6 Hz, 1 H), 6.72 (dd, J = 8.0, 1.2 Hz, 1 H), 3.79
(s, 3 H), 2.35 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 158.4,
151.3, 142.4, 134.9, 129.4, 122.1, 121.5, 121.3, 116.7, 113.8, 55.9,
21.3 ppm.
General Procedure for O-Phenylation of Substituted Benzoic Acids:
A mixture of substituted benzoic acid 13 (1 mmol), tBuOK
(1.5 mmol), and ionic-liquid-supported diphenyliodonium salt 8a
(1.1 mmol) in dry toluene (5 mL) was heated at reflux under a ni-
trogen atmosphere. The progress of the reaction was monitored by
TLC. After the reaction was complete, the toluene was evaporated,
and the product was extracted using a hexane/ethyl acetate mixture
(1:1 v/v). The combined organic layers were washed with saturated
sodium hydrogen carbonate solution, dried with anhydrous sodium
sulfate, and evaporated under reduced pressure to give the pure O-
phenylated product.
1
14dЈ: Pale brown solid; m.p. 119–124 °C (233 mg, 72%). H NMR
(300 MHz, CDCl3): δ = 7.89 (s, 4 H), 7.42 (d, J = 6.7 Hz, 2 H),
7.35–7.14 (m, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 164.7,
150.8, 138.0, 131.5, 129.5, 129.1, 126.1, 121.6, 101.6 ppm.
14eЈ: White solid, m.p. 58–60 °C; (142 mg, 72%). 1H NMR
(400 MHz, CDCl3): δ = 8.22 (d, J = 7.5 Hz, 2 H), 7.64 (t, J =
7.4 Hz, 1 H), 7.51 (t, J = 7.7 Hz, 2 H), 7.44 (t, J = 7.8 Hz, 2 H),
7.27 (dd, J = 12.7, 5.1 Hz, 1 H), 7.22 (d, J = 8.0 Hz, 2 H) ppm.
13C NMR (101 MHz, CDCl3): δ = 165.3, 151.1, 133.7, 130.3, 129.7,
129.6, 128.7, 126.0, 121.8 ppm.
1
9i: Pale brown viscous liquid (568 mg, 70%). H NMR (300 MHz,
[D6]DMSO): δ = 8.17 (d, J = 9.1 Hz, 2 H), 7.89 (d, J = 3.8 Hz, 1
H), 7.60 (d, J = 2.2 Hz, 1 H), 7.56 (d, J = 2.1 Hz, 1 H), 7.47 (d, J
= 8.1 Hz, 4 H), 7.14–7.06 (m, 5 H), 7.07–7.01 (m, 2 H), 4.74 (s, 2
H), 4.34 (t, J = 4.9 Hz, 2 H), 3.80 (s, 3 H), 3.77–3.72 (m, 5 H), 2.54
(s, 3 H), 2.28 (s, 6 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ =
162.4, 151.8, 146.2, 145.2, 140.0, 138.1, 137.3, 128.5, 128.3, 126.0,
122.7, 121.7, 117.8, 108.9, 101.4, 68.5, 66.8, 56.2, 47.8, 35.2, 21.2,
9.8 ppm.
9j: Brown viscous liquid (543 mg, 67%). 1H NMR (300 MHz, [D6]-
DMSO): δ = 8.11 (d, J = 7.2 Hz, 2 H), 7.90 (s, 1 H), 7.57 (d, J =
9.3 Hz, 2 H), 7.48 (d, J = 7.2 Hz, 4 H), 7.32 (d, J = 7.6 Hz, 2 H),
7.11 (d, J = 7.3 Hz, 4 H), 7.03 (s, 1 H), 4.73 (s, 2 H), 4.33 (s, 2 H),
3.97 (s, 3 H), 3.75–3.74 (m, 5 H), 2.52 (s, 3 H), 2.28 (s, 6 H) ppm.
13C NMR (75 MHz, DMSO): δ = 156.3, 151.6, 145.9, 145.2, 140.2,
138.3, 137.3, 135.5, 128.6, 128.2, 125.9, 123.9, 122.7, 121.7, 113.4,
109.9, 100.0, 68.5, 66.8, 57.5, 47.8, 35.2, 21.2, 9.8 ppm.
1
14fЈ: Colourless solid; m.p. 129–132 °C; (198 mg, 72%). H NMR
(300 MHz, CDCl3): δ = 7.87 (dd, J = 8.4, 2.0 Hz, 1 H), 7.68 (d, J
= 1.9 Hz, 1 H), 7.43 (t, J = 7.8 Hz, 2 H), 7.30–7.17 (m, 3 H), 6.95
(d, J = 8.5 Hz, 1 H), 3.97 (s, 3 H), 3.96 (s, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 165.0, 153.6, 151.1, 148.8, 129.5, 125.8,
124.4, 122.0, 121.8, 112.4, 110.4, 56.1, 56.1 ppm.
11: Off-white solid; m.p. 71–75 °C (369 mg, 70%). 1H NMR
(300 MHz, CDCl3): δ = 7.63 (d, J = 8.1 Hz, 2 H), 7.44 (d, J =
8.9 Hz, 2 H), 7.35 (s, 2 H), 7.06 (d, J = 8.0 Hz, 2 H), 6.54 (d, J =
8.9 Hz, 2 H), 4.20 (t, J = 6.9 Hz, 2 H), 3.78 (t, J = 5.6 Hz, 2 H),
3.69 (s, 3 H), 2.47 (s, 3 H), 2.27 (s, 3 H), 2.18–2.05 (m, 2 H) ppm.
Eur. J. Org. Chem. 2014, 2365–2370
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2369

A. Kumar et al.
FULL PAPER
13C NMR (75 MHz, CDCl3): δ = 158.1, 144.0, 143.6, 139.4, 138.3,
128.7, 125.8, 122.9, 121.2, 116.9, 83.1, 64.1, 45.3, 35.3, 28.9, 21.3,
9.6 ppm.
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Published Online: February 13, 2014
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 2365–2370