A Metal-Free and Microwave-Assisted Efficient Synthesis of Diaryl Sulfones

Article abstract of DOI:10.1055/s-0032-1317803

An efficient and general protocol for the synthesis of diaryl sulfones via the metal-free coupling of readily available diaryliodonium salts and arenesulfinates in PEG-400 under microwave irradiation has been developed. Utilizing this metal-free and eco-friendly protocol, we have prepared various diaryl sulfones in high yields and shorter reaction times under mild conditions. Furthermore, the coupling of diaryliodonium with arenesulfinate salts with and without copper iodide provides a convenient access to various diaryl sulfones with high selectivity. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0032-1317803

LETTER
▌831
lAetteMr etal-Free and Microwave-Assisted Efficient Synthesis of Diaryl Sulfones
Synthesis of Diaryl Sulfones
Dalip Kumar,* V. Arun, Meenakshi Pilania, K. P. Chandra Shekar
Department of Chemistry, Birla Institute of Technology and Science, Pilani 333031, Rajasthan, India
Fax +44(113)343 6565; E-mail: dalipk@pilani.bits-pilani.ac.in
Received: 13.02.2013; Accepted after revision: 04.03.2013
Scheme 1) were prepared by the oxidative coupling of ar-
Abstract: An efficient and general protocol for the synthesis of di-
ylboronic acids and arylsulfonyl chlorides using palladi-
aryl sulfones via the metal-free coupling of readily available diaryl-
um and copper catalysts.7,8 The disadvantages found in
using metal catalysts are longer reaction time and the use
iodonium salts and arenesulfinates in PEG-400 under microwave
irradiation has been developed. Utilizing this metal-free and eco-
friendly protocol, we have prepared various diaryl sulfones in high of expensive and moisture-sensitive reactants.
yields and shorter reaction times under mild conditions. Further-
more, the coupling of diaryliodonium with arenesulfinate salts with
and without copper iodide provides a convenient access to various
previous work
metal
metal
ArB(OH)2
route b
ArSO2Cl
diaryl sulfones with high selectivity.
ArSO2 Na
ArSO2Ar
+
ArX
+
Key words: diaryl sulfones, diaryliodonium salts, arenesulfinate
route a
salts, microwave irradiation, polyethylene glycol (PEG-400)
metal-free
Y
ArSO2 Na
Ar–I–Ar
+
this work
Aryl sulfones are an important class of compounds which
are widely utilized in industry and many organic transfor-
mations.1 Especially, diaryl sulfones are employed in the
biological field as antifungal, antimicrobial, antitumor,
and antibacterial agents and selective inhibitors of COX-
2 and HIV-1 reverse transcriptase (1, Figure 1).2 More-
over, they are intermediates for the preparation of various
biologically active molecules. Recently, diaryl sulfone
scaffolds have been identified as potent sFRP-1 and 11β-
HSD1inhibitors (2, Figure 1).3 Owing to their emerging
biological properties and useful synthetic applications in
organic synthesis, the construction of diaryl sulfones has
attracted much attention and a number of strategies have
been explored.
Scheme 1 Comparison of previous work and this work
Moreover, the synthesis of diaryl sulfones from diaryli-
odonium salts and arenesulfinate salts was briefly report-
ed utilizing an expensive palladium catalyst.9 To address
these drawbacks and to study the chemistry of diverse di-
aryliodonium salts, we envisaged a new greener synthetic
protocol by using cheaper and easily available starting
materials and an eco-friendly solvent, that is, polyethyl-
ene glycol (PEG-400) under microwave irradiation. Mi-
crowave irradiation has been widely used in organic
synthesis for the formation of a variety of carbon–carbon
and carbon–heteroatom bonds.10
Diaryliodonium salts have proved to be versatile electro-
philes in organic synthesis, they are stable and easy to
handle.11 In recent years, diaryliodonium salts have been
used extensively in the arylation of various nucleophiles
involving oxygen,12 sulfur,13 nitrogen,14 fluorine,15
arenes,16 and other heterocycles.17 Very recently, Yu and
co-workers reported the metal-free arylation of various ni-
trogen heterocycles using diaryliodonium salts.18 Gaunt et
al. reported the copper-catalyzed alkene arylation using
diaryliodonium salts,19 whereas Rodriguez and co-work-
ers reported the metal-free C–H direct arylation of unbi-
ased arenes.20 Varma and co-workers achieved the Heck-
type arylation of alkenes using diaryliodonium salts.21
O
O
S
R1
NC
S
F
R2
O
O
diaryl sulfones
11β HSD1 inhibitor
1
2
Figure 1 Biologically important diaryl sulfones
Sulfones were traditionally prepared by the oxidation of
sulfides and sulfoxides or electrophilic aromatic substitu-
tion of arenes with either arenesulfonic acids or corre-
sponding halides in the presence of strong acids.4 Later,
the reaction between organomagnesium halides and or-
ganolithium compounds with sulfonate esters have also
been well studied in their synthesis.5 Alternatively, the
above procedures are improved by copper-catalyzed reac-
tion of arenesulfinate salt (route a, Scheme 1) and aryl ha-
lides or triflates.6 Recently, diaryl sulfones (route b,
We developed a facile one-pot synthesis of 1,2,3-triazoles
utilizing diaryliodonium salts, sodium azide, and terminal
acetylenes.22 In recent years, there has been surge of inter-
est in the chemistry of diaryliodonium salts and metal-free
arylation reactions. In continuation of our ongoing re-
search efforts directed towards the synthetic utilities of or-
ganoiodane reagents, we herein report an efficient, rapid,
high-yielding, and metal-free protocol for the preparation
of various diaryl sulfones (Scheme 2).
SYNLETT 2013, 24, 0831–0836
Advanced online publication: 19.03.2013
DOI: 10.1055/s-0032-1317803; Art ID: ST-2013-D0144-L
© Georg Thieme Verlag Stuttgart · New York
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9
3
6
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2
1
4
1
4
3
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-
2
0
9
6

832
D. Kumar et al.
LETTER
To begin our investigation, we carried out the model reac-
tion between diphenyliodonium triflate 3a and sodium p-
toluenesulfinate salt (4a) under various conditions. The
reaction of diphenyliodonium triflate 3a with sodium p-
toluenesulfinate (4a) at room temperature in PEG-400 did
not proceed even after stirring for 24 hours. Next, we in-
vestigated this coupling reaction under microwave irradi-
ation and found that the formation of diaryl sulfone 5a
was excellent in PEG-400 (Table 1, entry 4).23 Reaction
solvents such as ethanol, dimethylformamide, and aceto-
nitrile afforded the desired product in poor yields (20–
37%).
Table 1 Arylation of Sodium p-Toluenesulfinate (4a)
O
S
Me
SO2Na
OTf
I
O
MW 50 °C, 10 min
Me
3a
5a
Entry
Solvent
Time (min) Yield (%)
1
2
3
4
5
6
7
MeCN
DMF
30
30
30
10
30
30
30
20
10
EtOH
37
Attempts to conduct the coupling reaction in water and
tetrahydrofuran failed to afford any product probably due
to the poor solubility of the reactants. Among the diaryl-
iodonium salts having different counteranions (OTf, OTs,
and Br) we found that diaryliodonium triflate is the best to
obtain diaryl sulfones in excellent yields. The optimized
conditions were applied to other symmetrical and unsym-
metrical diaryliodonium salts and sodium arenesulfinates,
and the results are summarized in Table 2. The optimized
reaction conditions were well tolerated by various diaryl-
iodonium salts having electron-withdrawing (bromo,
chloro, fluoro, and carboxyl), electron-donating (methyl
and methoxy), heterocyclyl (thienyl), and bulkier (mesi-
tyl) moieties.
PEG-400
THF
97
n.r.a
n.r.a
n.r.a
H2O
solvent-free
a n.r. = no reaction.
RSO2Na (4)
X
Ar
I
RSO2Ar
Ar
MW, 50 °C, 10 min
PEG-400
3
5
Scheme 2 Synthesis of diaryl sulfone 5 from diaryliodonium salt 3
Table 2 Metal-Free Synthesis of Diaryl Sulfones 5a–ma
Entry
Diaryliodonium salts 3
Sulfinate salts 4
Diaryl sulfones 5b
Yield (%)c Mp (°C)
O
S
OTf
I
Me
SO2Na
119–121
O
1
96
(119–122)7
Me
4a
3a
5a
O
S
OTf
I
O
157–159
2
3
4
5
4a
4a
4a
4a
92
(158–159)6b
Me
Me
Me
Me
5b
3b
O
S
Br
I
131–133
O
82
(132–134)6b
Me
Br
Br
Br
5c
3c
O
S
Br
I
116–118
O
83
(119–120)6b
Me
Cl
Cl
Cl
5d
3d
Me
Me
O
S
OTf
I
116–117
O
89
(115–117)25
Me
Me
Me
Me
Me
5e
3e
Synlett 2013, 24, 831–836
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Diaryl Sulfones
833
Table 2 Metal-Free Synthesis of Diaryl Sulfones 5a–ma (continued)
Entry
6
Diaryliodonium salts 3
Sulfinate salts 4
Diaryl sulfones 5b
Yield (%)c Mp (°C)
O
S
OTf
I
O
4a
91
120–121
Me
COOH
COOH
5f
3f
O
S
OTf
I
S
119–121
O
7
8
4a
4a
86
88
94
86
(119–122)7
Me
3g
5a
O
OTf
S
I
85–87
O
(85–86)6b
Me
F
F
F
5g
3h
O
S
OTf
I
SO2Na
128–130
O
9
(127–129)7
4b
5h
3a
O
S
Br
I
91–92
O
10
4b
4b
(92–94)30
Br
Br
Br
5i
3c
O
S
Br
I
O
77–79
11
82
(77–78)30
Cl
Cl
Cl
5j
3d
Me
Me
O
S
OTf
I
78–80
O
12
13
14
15
4b
4a
91
82
83
83
(79–81)30
Me
Me
Me
Me
3e
3i
5k
O
OTs
OTf
S
S
S
I
I
S
116–118
O
(118–120)7
Me
5l
O
S
Me
MeSO2Na
145–146
O
(144–145)8
4c
5m
3a
O
S
OTf
I
Me
84–86
O
4c
(85–87)6a
Me
Me
Me
5n
3b
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 831–836

834
D. Kumar et al.
LETTER
Table 2 Metal-Free Synthesis of Diaryl Sulfones 5a–ma (continued)
Entry
16
Diaryliodonium salts 3
Sulfinate salts 4
Diaryl sulfones 5b
Yield (%)c Mp (°C)
O
OTs
S
I
S
S
S
47–48
Me
4c
73
84
(45–47)6a
O
3i
5o
O
S
OTs
I
Me
119–120
O
17
4c
(118–120)6a
OMe
MeO
OMe
5p
3j
a Reaction conditions: 50 °C, MW, (5a–l: 10 min; 5m–p: 30 min).
b The yields refer to pure isolated products.
Diaryliodonium salts 3 afforded the desired diaryl sul- A plausible mechanistic pathway for the coupling of dia-
fones 5a–p in excellent yields (82–96%, Table 2). Arene- ryliodonium salts 3a and arenesulfinates 4 is outlined in
sulfinate salts 4a,b were found to be relatively more Scheme 4. The initial approach of the arenesulfinate anion
reactive (10 min, Table 2, entries 1–13) than the corre- to the electron-deficient iodine center forms a tricoordi-
sponding sodium methanesulfinate 4c (30 min, Table 2, nated intermediate A which probably undergoes reductive
entries 14–17). After preparing various diaryl sulfones in elimination by the loss of iodobenzene to generate diaryl
excellent yields, we explored the coupling reaction of di- sulfones 5.26
aryliodonium salts 3e–g and sodium p-toluenesulfinate
The difference in reactivity in the presence of copper
could be rationalized via the initial oxidative insertion of
copper(I) to the diaryliodonium salt 3 to form an organo
Cu(III)–aryl species I (stabilized by electron-rich aryl
(4a) in the presence of a catalytic amount of CuI (Scheme
3).24 Interestingly, we observed that the CuI-catalyzed
coupling reaction led to diaryl sulfone 5a in 71% yield as
a major product along with a small amount of diaryl sul-
moiety) by the loss of an aryl iodide with a relatively elec-
fone 5e (18% yield); in contrast, 5a was the exclusive
tron-deficient aryl ring. The highly electrophilic species I
product of the coupling reaction in the absence of CuI.
is then attacked by sodium arenesulfinate 4 to generate the
When unsymmetrical diaryliodonium salt 3f was treated
aryl–Cu(III)–arenesulfinate species II, which upon reduc-
with sodium p-toluenesulfinate (4a) under the similar re-
tive elimination results in diaryl sulfone 5 (Scheme 5).27
action conditions, diaryl sulfone 5a was obtained as a ma-
Generally, the most electron-rich aryl moiety was trans-
ferred to arenesulfinates when unsymmetrical diaryliodo-
nium salts were employed. However, the exact
mechanism for the formation of diaryl sulfones remains
jor product (61% yield) along with a minor amount of 5f
(21%); whereas 5f was exclusively formed under copper-
free conditions. Further, coupling of heteroaryl iodonium
salt 3g in the presence of CuI gave exclusively thienyl tol-
yl sulfone 5l in 81% yield, whereas the corresponding
copper-free coupling reaction delivers diaryl sulfone 5a in
86% yield. This different selectivity of unsymmetrical di-
unclear at this stage.
During the submission of this work Manolikakes et al.
have also reported the synthesis of various diaryl sulfones
aryliodonium salt with and without CuI as a catalyst could
be utilized to prepare diversely substituted diaryl sulfones.
OTf
Me
I
TolSO2Na
+
5a (71%) 5e (18%)
In this metal-free protocol PEG-400 probably forms a
complex with the sodium cation, thereby weakening the
interaction between the sodium cation and the sulfinate
anion.25 As a result the free sulfinate anion acts as an ele-
vated active species to react relatively faster with im-
proved product yield. Also the solubility of some salts in
PEG-400 is reported to be comparable with dimethylsulf-
oxide. Furthermore, PEG-400 efficiently couples under
microwave irradiation and makes the reaction feasible in
a shorter time. No product was formed without PEG-400
under similar reaction conditions. However, exposing the
neat mixture of 3a and 4a to microwave irradiation at
150 °C for 15 minutes afforded the diaryl sulfone 5a in
90% yield.
(a)
CuI, PEG-400
MW, 15 min
Me
3e
Me
OTf
I
TolSO2Na
(b)
(c)
+
5a (61%) 5f (21%)
CuI, PEG-400
MW, 15 min
CO2H
3f
OTf
I
S
TolSO2Na
5l (87%)
3g
CuI, PEG-400
MW, 15 min
Scheme 3 Copper iodide catalyzed formation of diaryl sulfones 5
Synlett 2013, 24, 831–836
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Diaryl Sulfones
835
R
S
O
O
OTf
I
RSO2Na
– NaOTf
– PhI
SO2R
I
3a
5
A
Scheme 4 A plausible mechanism for the formation of diaryl sulfones
CuII
ArSO2Na
TfONa
OTf
Ar2
Ar1 CuIIIISO2Ar
I
Ar1 CuIIII OTf
Ar1 SO2Ar
Ar1
Ar2I
CuII
3
5
I
II
Scheme 5 Possible mechanism for the copper(I)-catalyzed formation of diaryl sulfones 5
(4) Graybill, B. M. J. Org. Chem. 1967, 32, 2931.
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in good yields from the reactions of diaryliodonium salts
3 and arenesulfinate salts 4 in DMF at 90 °C within 24
hours.28 However, these reaction conditions failed to pro-
duce alkyl sulfones 5m–p which were successfully pre-
pared in good yields under the present reaction conditions.
Further, our rapid protocol (10 min vs. 24 h) utilizes only
a small amount of biodegradable PEG-400 (100 μL) and
avoids the use of DMF. Therefore, this independently de-
veloped protocol is relatively advantageous to prepare
various diaryl sulfones in high yields.
In conclusion, we have developed a novel and metal-free
synthetic method to prepare various diaryl sulfones in
high yields from readily available diaryliodonium salts
and arenesulfinates using the green solvent PEG-400 in a
short reaction time. The copper iodide catalyzed coupling
of diaryliodonium salts and arenesulfinate salts resulted in
different selectivity to afford diverse diaryl sulfones.
(13) Vaddula, B. R.; Varma, R. S.; Leazer, J. Eur. J. Org. Chem.
2012, 6852.
(14) Guo, F.; Wang, L.; Wang, P.; Yu, J.; Han, J. Asian J. Org.
Chem. 2012, 1, 218.
Acknowledgment
(15) Wang, B.; Qin, L.; Neumann, K. D.; Uppaluri, S.; Cerny, R.
L.; DiMagno, S. G. Org. Lett. 2010, 12, 3352.
(16) Ciana, C.-L.; Phipps, R. J.; Brandt, J. R.; Meyer, F.-M.;
Gaunt, M. J. Angew. Chem. Int. Ed. 2011, 50, 458.
(17) Beletskaya, I. P.; Davydov, D. V.; Moreno-Mañas, M.
Tetrahedron Lett. 1998, 39, 5621.
We sincerely thank the CSIR, New Delhi for financial support and
SAIF, Punjab University, Chandigarh for analytical support.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.SnoIufproig
m
iotSrat
ungIifoop
r
t
(18) Wen, J.; Zhang, R.-Y.; Chen, S.-Y.; Zhang, J.; Yu, X.-Q. J.
Org. Chem. 2011, 77, 766.
References and Notes
(19) Phipps, R. J.; McMurray, L.; Ritter, S.; Duong, H. A.; Gaunt,
M. J. J. Am. Chem. Soc. 2012, 134, 10773.
(20) Castro, S.; Fernandez, J. J.; Vicente, R.; Fananas, F. J.;
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(21) Vaddula, B. R.; Saha, A.; Leazer, J.; Varma, R. S. Green.
Chem. 2012, 14, 2133.
(22) Vaddula, B. R.; Kumar, D. Synthesis 2010, 1687.
(23) General Procedure for the Synthesis of Diaryl Sulfones 5
The diaryliodonium salts were prepared according to the
reported methods.29 A mixture of diaryliodonium salt 3a–h
(0.2 mmol) and arenesulfinate salt 4a–c (0.2 mmol) in PEG-
400 (0.1 mL) was placed in a sealed microwave vial and
irradiated in MW (power 200 W) at 50 °C for 10 min. After
completion, H2O (1 mL) was added, and the reaction mixture
was extracted with EtOAc (3 × 5 mL). The combined
organic extract was washed with H2O (4 mL) and dried over
anhyd Na2SO4. The solvent was evaporated in vacuo, the
(1) The Chemistry of Sulfones and sulfoxides; Patai, S.;
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H.; Lévesque, J.-F.; Seto, C.; Silva, J. H.; Trimble, L. A.;
Carriere, M.-C.; Denis, D.; Greig, G.; Kargman, S.;
Lamontagne, S.; Mathieu, M.-C.; Sawyer, N.; Slipetz, D.;
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Nicoll-Griffith, D. A.; Wang, Z.; Zamboni, R.; Young, R.
N.; Metters, K. M. J. Med. Chem. 2007, 50, 794.
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Med. Chem. 2008, 51, 7670.
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 831–836

836
D. Kumar et al.
LETTER
solid thus obtained was washed with hexane and dried to
afford 8a–m in high yields.
(24) General Procedure for the Copper-Catalyzed
Preparation of Diaryl Sulfones 5
NMR (400 MHz, DMSO-d6): δ = 2.35 (s, 3 H), 7.47–7.42
(m, 4 H), 7.85 (d, 2 H, J = 6.6 Hz), 8.04 (dd, 2 H, J = 9.0, 5.1
Hz).
Diphenyl Sulfone (5h)
A mixture of diaryliodonium salts 3e–g (0.2 mmol) and
sodium p-toluenesulfinate 4a (0.2 mmol) in PEG-400 (0.1
mL). A catalytic amount of CuI (10 mol%) was added, and
the reaction mixture was placed in a sealed microwave vial
and irradiated in MW (power 200 W) at 50 °C for 15 min.
After completion of the reaction, 20% Na2CO3 solution (2
mL) was added. The aqueous layer was extracted with
EtOAc (3 × 5 mL), washed with H2O (7 mL), and dried over
anhyd. Na2SO4. The solvents were evaporated under reduced
pressure, and the residue so obtained was purified by column
chromatography on silica gel (100–120 mesh) eluting with
hexane–EtOAc (4:1) afforded the desired diaryl sulfones 5.
Spectral Data for Selected Compounds
Yield 88%; white solid; mp 128–130 °C (lit.7 mp 127–129
°C). IR (KBr): 1303, 1149 cm–1. 1H NMR (400 MHz,
DMSO-d6): δ = 7.59–7.51 (m, 6 H), 7.89 (d, 4 H, J = 8.6 Hz).
p-Chlorophenyl Phenyl Sulfone (5j)
Yield 96%; white solid; mp 77–79 °C (lit.30 mp 77–78 °C).
1H NMR (400 MHz, DMSO-d6): δ = 7.64 (d, 2 H, J = 7.8
Hz), 7.71 (d, 3 H, J = 8.6 Hz), 7.98 (d, 4 H, J = 8.2 Hz). ESI-
MS: m/z calcd for C12H10ClO2S [M + H]+: 253.0; found:
253.1.
2,4,6-Trimethylphenyl Phenyl Sulfone (5k)
Yield 91%; white solid; mp 78–80 °C (lit.30 mp 79–81 °C).
1H NMR (400 MHz, DMSO-d6): δ = 2.30 (s, 3 H), 2.56 (s, 6
H), 7.11 (s, 2 H), 7.42 (t, 2 H, J = 7.8 Hz), 7.53 (t, 1 H, J =
7.4 Hz), 7.73 (d, 2 H, J = 7.7 Hz). 13C NMR (100 MHz,
DMSO-d6): δ = 143.33, 141.25, 133.16, 131.58, 131.30,
129.72, 121.68, 113.42, 26.45, 20.21. ESI-MS: m/z calcd for
C15H17O2S [M + H]+: 261.1; found: 261.1
Phenyl Tolyl Sulfone (5a)
Yield 96%; white solid; mp 119–121 °C (lit.7 mp 119–
122 °C). IR (KBr): 1303, 1149 cm–1. 1H NMR (400 MHz,
DMSO-d6): δ = 2.36 (s, 3 H), 7.34 (d, 2 H, J = 8.0 Hz), 7.58–
7.50 (m, 3 H), 7.76 (d, 2 H, J = 8.1 Hz), 7.87 (d, 2 H, J = 7.3
Hz). ESI-MS: m/z calcd for C13H13O2S [M + H]+: 233.1;
found: 233.1.
2-Thienyl Tolyl Sulfone (5l)
Yield 82%; white solid; mp 116–118 °C (lit.7 mp 118–120
°C). 1H NMR (400 MHz, DMSO-d6): δ = 2.34 (s, 3 H), 7.30
(d, 2 H, J = 8.0 Hz), 7.50–7.46 (m, 2 H, J = 7.4 Hz), 7.75 (d,
2 H, J = 8.0 Hz), 7.84 (d, 1 H, J = 7.5 Hz).
Bistolyl Sulfone (5b)
Yield 92%; white solid; mp 157–159 °C (lit.7 mp 158–
159 °C). IR (KBr): 1288, 1149 cm–1. 1H NMR (400 MHz,
DMSO-d6): δ = 2.35 (s, 6 H,), 7.29 (d, 4 H, J = 8.0 Hz), 7.72
(d, 4 H, J = 7.7 Hz), ESI-MS: m/z calcd for C14H15O2S [M +
H]+: 247.1; found: 247.2.
Methyl Phenyl Sulfone (5m)
Yield 83%; white solid; mp 145–146 °C (lit.8 mp 144–
145 °C). 1H NMR (400 MHz, DMSO-d6): δ = 3.12 (s, 3 H),
7.63 (t, 2 H, J = 8.17 Hz), 7.71 (t, 1 H, J = 5.4 Hz), 7.94 (d,
2 H, J = 7.2 Hz).
p-Bromophenyl Tolyl Sulfone (5c)
Yield 82%; white solid; mp 131–133 °C (lit.1 mp 132–
134 °C). IR (KBr): 1319, 1149 cm–1. 1H NMR (400 MHz,
DMSO-d6): δ = 2.36 (s, 3 H) 7.38 (d, 2 H, J = 8.1 Hz), 7.62
(d, 2 H, J = 8.6 Hz), 7.83–7.74 (4 H, m). ESI-MS: m/z calcd
for C13H12BrO2S [M + H]+: 313.0; found: 313.0.
p-Chlorophenyl Tolyl Sulfone (5d)
Methyl p-Tolyl Sulfone (5n)
Yield 83%; white solid: mp 87 °C (lit.6a mp 144–145 °C). 1H
NMR (400 MHz, DMSO-d6): δ = 2.44 (s, 3 H), 3.12 (s, 3 H),
7.43 (d, 2 H, J = 8.0 Hz), 7.80 (d, 2 H J = 8.1 Hz).
Methyl p-Methoxyphenyl Sulfone (5p)
Yield 84%; white solid: mp 119 °C (lit.6a mp 118–120 °C).
1H NMR (400 MHz, DMSO-d6): δ = 3.10 (s, 3 H), 3.87 (s, 3
H), 7.12 (d, 2 H, J = 8.8 Hz), 7.85 (d, 2 H, J = 8.8 Hz).
(25) Chen, J.; Spears, S. K.; Huddleston, G. J.; Rogers, R. D.
Green Chem. 2005, 7, 64.
Yield 83%; white solid; mp 116–118 °C (lit.1 mp 119–
120 °C). IR (KBr): 1319, 1149 cm–1. ESI-MS: m/z calcd for
C13H12ClO2S [M + H]+: 267.0; found: 267.1.
2,4,6-Trimethylphenyl Tolyl Sulfone (5e)
Yield 89%; white solid; mp 116–117 °C (lit.30 mp 115–117
°C). 13C NMR (100 MHz, DMSO-d6): δ = 143.18, 142.89,
139.90, 139.07, 133.60, 131.84, 129.25, 125.67, 22.18,
21.03, 20.42. ESI-MS: m/z calcd for C16H19O2S [M + H]+:
275.1; found: 275.2.
(26) Ochiai, M. Topics in Current Chemistry; Vol. 224; Chap. 3;
Springer: Berlin/Heidelberg, 2002.
(27) (a) Phipps, R. J.; Grimster, N. P.; Gaunt, M. J. J. Am. Chem.
Soc. 2008, 130, 8172. (b) Phipps, R. J.; Gaunt, M. J. Science
2009, 323, 1593. (c) Bigot, A.; Williamison, A. E.; Gaunt,
M. J. J. Am. Chem. Soc. 2011, 133, 13778. (d) Harvey, J. S.;
Simonovich, S. P.; Jamison, C. R.; MacMillan, D. W. C. J.
Am. Chem. Soc. 2011, 133, 13782. (e) Chen, B.; Hou, X.-L.;
Li, Y.-X.; Wu, Y.-D. J. Am. Chem. Soc. 2011, 133, 7668.
(28) Umierski, N.; Manolikakes, G. Org. Lett. 2013, 15, 188.
(29) (a) Bielawski, M.; Zhu, M.; Olofsson, B. Adv. Synth. Catal.
2007, 349, 2610. (b) Kraszkiewicz, L.; Skulski, L. Synthesis
2008, 2373.
p-Tolylsulfonylbenzoic Acid (5f)
Yield 91%; white solid; mp 120–121 °C. IR (KBr): 3055-
2553, 1689, 288, 1157 cm–1. 1H NMR (400 MHz, DMSO-
d6): δ = 2.33 (3 H, s,), 7.31 (2 H, d, J = 7.5 Hz), 7.76 (2 H, d,
J = 7.5 Hz), 7.93 (2 H, d, J = 7.9 Hz), 8.07 (2 H, d, J = 7.7
Hz). 13C NMR (100 MHz, DMSO-d6): δ = 165.94, 144.85,
144.37, 137.27, 134.90, 130.13, 129.85, 127.35, 127.01,
20.67.
p-Fluorophenyl Tolyl Sulfone (5g)
(30) Singh, R. P.; Kamble, R. M.; Chandra, K. L.; Saravanan, P.;
Singh, V. K. Tetrahedron 2001, 57, 241.
Yield 88%; white solid; mp 85–87 °C (lit.1 mp 85–86 °C). 1H
Synlett 2013, 24, 831–836
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