Oligomeric iodosylbenzene sulfate: A convenient hypervalent iodine reagent for oxidation of organic sulfides and alkenes

Article abstract of DOI:10.1055/s-0029-1216870

Oligomeric iodosylbenzene sulfate, (PhIO)₃·SO ₃, which can be formally considered as a partially depolymerized activated iodosylbenzene, is a readily available, stable, and water-soluble hypervalent iodine reagent that is useful for the oxidation of sulfides or alkenes. Furthermore, this reagent can be conveniently generated in situ from (diacetoxyiodo)benzene and sodium bisulfate and used without isolation in oxidations in aqueous solution or under solvent-free conditions. The reaction of iodosylbenzene sulfate in situ with organic sulfides at room temperature affords sulfoxides in high yields without over-oxidation to sulfones, and this reaction is compatible with the presence in the substrate molecule of hydroxy groups, double bonds, benzylic carbon atoms, carboxylate groups, and various substituted phenyl rings. The reaction of an alkene with iodosylbenzene sulfate generated in situ results in oxidative rearrangement to form a ketone or aldehyde. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0029-1216870

PAPER
2505
Oligomeric Iodosylbenzene Sulfate: A Convenient Hypervalent Iodine
Reagent for Oxidation of Organic Sulfides and Alkenes
O
ligomeric Iodosylben
e
zene Sulfa
t
h
e
man S. Yusubov,*a Rosa Y. Yusubova,a Tatyana V. Funk,a Ki-Whan Chi,b Viktor V. Zhdankin*c
a
b
c
The Siberian State Medical University and Tomsk Polytechnic University, 2 Moskovsky trakt, 634050 Tomsk, Russian Federation
Department of Chemistry, University of Ulsan, 680-749 Ulsan, Korea
Department of Chemistry, University of Minnesota Duluth, Duluth, MN 55812, USA
Fax +218(726)7394.; E-mail: vzhdanki@d.umn.edu
Received 6 March 2009; revised 14 April 2009
iodosylbenzene monomer with 18-crown-6 (18C6), for
example, complex 1.6 The depolymerized protonated io-
dosylbenzene complex 1 is an efficient oxidizing agent
that has moderate solubility and excellent stability in wa-
Abstract: Oligomeric iodosylbenzene sulfate, (PhIO)3·SO3, which
can be formally considered as a partially depolymerized activated
iodosylbenzene, is a readily available, stable, and water-soluble hy-
pervalent iodine reagent that is useful for the oxidation of sulfides
or alkenes. Furthermore, this reagent can be conveniently generated ter.6a
in situ from (diacetoxyiodo)benzene and sodium bisulfate and used
[Hydroxy(tosyloxy)iodo]benzene (HTIB, 2) and similar
without isolation in oxidations in aqueous solution or under solvent-
free conditions. The reaction of iodosylbenzene sulfate in situ with
organic sulfides at room temperature affords sulfoxides in high
yields without over-oxidation to sulfones, and this reaction is com-
patible with the presence in the substrate molecule of hydroxy
groups, double bonds, benzylic carbon atoms, carboxylate groups,
and various substituted phenyl rings. The reaction of an alkene with
iodosylbenzene sulfate generated in situ results in oxidative rear-
rangement to form a ketone or aldehyde.
phenyliodine(III) organosulfonates, PhI(OH)OSO2R, rep-
resent an important class of hypervalent iodine reagents
that are commonly used as versatile mild oxidants and
electrophiles in organic synthesis.1,3,7 In contrast to phe-
nyliodine(III) organosulfonates, the corresponding deriv-
atives of sulfuric acid have not been extensively
investigated. The formation of a highly hygroscopic sul-
fate 4 in the reaction of (dichloroiodo)benzene and silver
sulfate was briefly described by Alcock and Waddington
in 1963,8 and the unstable and extremely hygroscopic sul-
fates 3 (PhIO·SO3) and 5 [(PhIO)2·SO3] are generated
from iodosylbenzene and sulfur trioxide or trimethylsilyl
chlorosulfonate under absolutely dry conditions.9
Key words: oxidations, iodine, sulfoxides, iodosylbenzene, (di-
acetoxyiodo)benzene, hypervalent iodine
Hypervalent iodine compounds are used extensively in or-
ganic synthesis as highly selective and environmentally
friendly oxidizing reagents.1 Among these reagents, iodo-
sylbenzene, (PhIO)n, is especially important as an oxy-
gen-transfer agent that has found widespread application
in various oxidation reactions.2,3 In particular, iodosylben-
zene is the most efficient source of oxygen atoms for oxi-
dations catalyzed by cytochrome P-450 or discrete
transition-metal complexes.2 Despite its usefulness as an
oxidant, practical applications of iodosylbenzene are
hampered by its low solubility in nonreactive media,3 its
low thermal stability, and its tendency to explode violent-
ly upon moderate heating.4 The low solubility of iodosyl-
benzene is explained by its existence as a zigzag,
polymeric, asymmetrically bridged structure in which
monomeric units of iodosylbenzene (PhIO) are linked by
intermolecular I···O secondary bonds.3 An explanation of
the oxo-bridged zigzag polymer structure of (PhIO)n on
the basis of the trans-effects of the ligands has recently
been provided.5
OH
OH
I
+
–
PhIOSO2O–
Ph I +
BF4
Ph
OTs
3
18C6
2 (HTIB)
1
Ph
O
Ph
I
I
Ph
Ph
O
O
O
I
I
S
O2
HO3SO
OSO3H
4
5
Figure 1 Known phenyliodine(III) organosulfonates and sulfates
We recently reported the preparation and X-ray structure
of a new, stable, and water-soluble oligomeric iodosyl-
benzene sulfate (PhIO)3·SO3 (6; Scheme 1), which can be
considered as a partially depolymerized and activated
form of iodosylbenzene.10 Compound 6 can be prepared
by treatment of (diacetoxyiodo)benzene with one equiva-
lent of sodium bisulfate, and isolated by crystallization
from water as a stable yellow crystalline product
(Scheme 1).
Iodosylbenzene can be depolymerized by protonation or
by treatment with a Lewis acid. Ochiai and co-workers
have reported the preparation, X-ray crystal structures,
and useful oxidizing reactions of activated complexes of
We have found that sulfate 6 is a highly reactive oxidant
towards organic sulfides and alkenes, with a reactivity
pattern that is similar to that of activated iodosylbenzene
complexes, such as complex 1. In particular, the oxidation
of the aryl alkyl sulfide 7 proceeds at room temperature
SYNTHESIS 2009, No. 15, pp 2505–2508
x
x.
x
x
.
2
0
0
9
Advanced online publication: 26.06.2009
DOI: 10.1055/s-0029-1216870; Art ID: M01009SS
© Georg Thieme Verlag Stuttgart · New York

2506
M. S. Yusubov et al.
PAPER
O
S
H2O
3 PhI(OAc)2 + 2 NaHSO4
(PhIO)3SO3
6, MeCN–H2O (5:1)
10 min, r.t.
S
– 6 AcOH
– Na2SO4
Me
6
Me
94%
NC
Scheme 1 Preparation of oligomeric iodosylbenzene sulfate (6)
NC
7
8
6, MeCN–H2O (5:1)
2 h, r.t.
within 10 minutes, thereby demonstrating the high oxidiz-
ing ability of reagent 6. This oxidation leads to the forma-
tion of the corresponding sulfoxide 8 in high yield without
over-oxidation to the sulfone (Scheme 2). A similar oxi-
dation with iodosylbenzene proceeds under the same con-
ditions (water, room temperature), but only in the
presence of a catalytic bromide anion, which is required
for the depolymerization of (PhIO)n.11 The oxidation of
cyclohexene with sulfate 6 results in ring contraction with
the formation of cyclopentanecarbaldehyde (9).12 Like-
wise, the oxidation of 1,1-diphenylethylene leads to oxi-
dative rearrangement with formation of ketone 10
(Scheme 2).13 This pattern of reactivity is similar to that of
iodosylbenzene activated by a Brønsted or Lewis acid. In
particular, the reaction of (PhIO)n with cyclohexene in
aqueous sulfuric acid affords ketone 9 in 44% yield.12a
The formation of the same product in low yield was also
reported for the reactions of cyclohexene with phenyl-
O
O
39%
9
6, MeCN–H2O (5:1)
30 min, r.t.
Ph
Ph
Ph
93%
Ph
10
Scheme 2 Oxidations by using oligomeric iodosylbenzene sulfate 6
iodosyl sulfate and iodosylbenzene–trifluoroborane com-
plex.12b
A further study of these reactions (Scheme 2) showed that
reagent 6 can be conveniently generated in situ from (di-
acetoxyiodo)benzene and sodium bisulfate, and used
without isolation for subsequent oxidations in aqueous so-
lution or under solvent-free conditions.14 In particular, the
reaction of sulfide 7 with (diacetoxyiodo)benzene and so-
Table 1 Oxidations of Sulfides with Reagent 6 Generated In Situ from (Diacetoxyiodo)benzene and Sodium Bisulfate
Sulfide
Producta
MeCN–H2O (5:1)
H2O
Solid state
Time (min) Yield (%)b
Time (h) Yield (%)b
Time (min) Yield (%)
PhSMe
PhSOMe
10
86
98
67
45
1.25
1.0
88
96
88
1.0
1.0
1.0
2.0
1.0
93
99
89
4-BrC6H4SMe
4-MeOC6H4SMe
PhSCH2CN
CH2=CHCH2SPh
(t-Bu)2S
4-BrC6H4SOMe
4-MeOC6H4SOMe
PhSOCH2CN
CH2=CHCH2SOPh
(t-Bu)2SO
15
5.0
2.0
2.0
0.5
2.0
1.75c
2.0
d
d
–
–
e
–
3.0
66
68
f
f
f
f
47
–
–
–
–
e
MeS(CH2)2OH
(CH2)5S
MeSO(CH2)2OH
(CH2)5SO
–
1.25
1.30
5.0
47
46
80
19
1.0
82
f
f
f
f
–
–
–
–
PhSBn
PhSOBn
5.0
95
1.0
90
d
d
d
d
4-ClC6H4SCH2CO2H 4-ClC6H4SOCH2CO2H
–
–
3.0g
–
–
h
h
4-O2NC6H4SMe
4-NCC6H4SMe
3-O2NC6H4SMe
[Me(CH2)7]2S
4-O2NC6H4SOMe
4-NCC6H4SOMe
3-O2NC6H4SOMe
[Me(CH2)7]2SO
360
10
84
92
–
–
5.0
3.0
5.0
2.0
90
94
47
95
h
h
–
–
i
i
10
–
10
–
h
h
20
97
–
–
a All products were identified by comparison of their physical and spectral (IR, NMR, and MS) properites with those reported in the literature.15
b Isolated yield (column chromatography).
c The reaction was started out at 0 °C and then gradually warmed to r.t.
d The reaction was too slow at r.t., and significant decomposition was observed upon heating.
e Nonselective reaction with the formation of a complex mixture was observed under these conditions
f The reaction was not performed in a mortar because of the extremely strong smell of the substrate.
g The reaction was carried out at 90 °C.
h The reaction was not performed because the substrate was insoluble in H2O.
i A black tar was formed under these reaction conditions.
Synthesis 2009, No. 15, 2505–2508 © Thieme Stuttgart · New York

PAPER
Oligomeric Iodosylbenzene Sulfate
2507
ing a gas chromatograph equipped with a quadrupole mass
spectrometer (Hewlett Packard 5890/II) as the detector (EI, 70 eV).
Microanalyses were carried out by using a 1106 Carlo Erba CHNS-
O analyzer. Flash column chromatography was performed on silica
gel (L40/100 mm; Chemapol). TLC was performed on silica gel
plates (Sorbfil, Russia). All commercial reagents were of ACS re-
agent grade and used without further purification. Oligomeric iodo-
sylbenzene sulfate (6) was prepared according to the previously
reported procedure.10
dium bisulfate in aqueous acetonitrile proceeds at room
temperature within 10 minutes and affords the corre-
sponding sulfoxide 8 in 92% isolated yield, which is al-
most identical to that obtained with purified reagent 6
(Scheme 2). The results of oxidations of various sulfides
with reagent 6 generated in situ from (diacetoxyiodo)ben-
zene and sodium bisulfate in aqueous acetonitrile, water,
or under solvent-free conditions are summarized in
Table 1. The final products were isolated and their identi-
ty was confirmed by GC-MS and NMR spectroscopy
through comparison with known sulfoxides.15 In general,
the best yields of sulfoxides were achieved and the reac-
tion was fastest under solvent-free conditions. No over-
Oxidation of 4-(Methylthio)benzonitrile (7) with Oligomeric
Iodosylbenzene Sulfate (6)
Solid reagent 6 (130 mg, 0.175 mmol) was added to a stirred soln of
sulfide 7 (82.5 mg, 0.5 mmol) in 5:1 MeCN–H2O (1 mL), and the
soln was stirred at r.t. for 10 min. The solvent was evaporated and
oxidation to sulfones was observed, and the reaction is the residue was separated by column chromatography [hexanes–
EtOAc (2:1)]; yield: 76 mg (92%). The purity and identity of prod-
uct 8 were confirmed by GC-MS and by comparison of its NMR
compatible with the presence of a hydroxy group, a dou-
ble bond, a benzylic carbon, a carboxylic function, or var-
ious substituted phenyl rings in the molecule of the
substrate (Table 1).
spectra with literature data.15b
Oxidation of Sulfides to Sulfoxides with Oligomeric Iodosylben-
zene Sulfate (6) Generated In Situ: General Procedures
Oxidation in Aqueous Acetonitrile: Solid PhI(OAc)2 (169 mg, 0.525
Reactions of alkenes 11 and 14 with (diacetoxyiodo)ben-
zene and sodium bisulfate under solvent-free conditions
mmol) and NaHSO4·H2O (73 mg, 0.525 mmol) were added to a
afforded the corresponding products of oxidative rear-
stirred soln of the organic sulfide (0.5 mmol) in 5:1 MeCN–H2O (1
rangements 9, 10, 12, 13, and 15 (Scheme 3). The yields
of these products were almost identical to those obtained
mL), and the mixture was magnetically stirred until the reagent was
consumed (TLC; see Table 1). The mixture was then concentrated
with the pure reagent 6 (Scheme 2). The formation of the
rearranged aldehyde 12 in the reaction of styrene with ac- mL) and separated by column chromatography [EtOAc–hexanes
in vacuo, and the organic products were extracted with CH2Cl2 (2
(1:2) followed by EtOAc] to give the analytically pure sulfoxide.
tivated iodosylbenzene monomer complex 1 has been pre-
viously reported.6a
Oxidation in Water: Solid PhI(OAc)2 (169 mg, 0.525 mmol) and
NaHSO4·H2O (73 mg, 0.525 mmol) were added to a stirred soln of
the organic sulfide (0.5 mmol) in H2O (1 mL), and the mixture was
magnetically stirred until the reagent was consumed (TLC; see
Table 1). The mixture was then extracted with CH2Cl2 (2 mL), and
the organic products were separated by column chromatography
[EtOAc–hexanes (1:2) followed by EtOAc] to give the analytically
pure sulfoxide.
PhI(OAc)2, NaHSO4•H2O
grinding, 0.5-1 min, r.t.
O
Ph
R
Ph
R
83–97%
10 (R = Ph)
12 (R = H)
13 (R = Me)
11
Solvent-Free Oxidation: Solid PhI(OAc)2 (169 mg, 0.525 mmol),
NaHSO4·H2O (73 mg, 0.525 mmol), and an organic sulfide (0.5
mmol) were mixed in a mortar, and the mixture was intensively
ground for 1–5 min (see Table 1). The mixture was then extracted
with CH2Cl2 (2 mL), and the organic products were separated by
column chromatography [EtOAc–hexanes (1:2) followed by
EtOAc] to give the analytically pure sulfoxide.
R
PhI(OAc)2, NaHSO4•H2O
grinding, 0.5–1 min, r.t.
O
R
39–45%
14
9
(R = H)
15 (R = Me)
Scheme 3 Oxidations of alkenes with reagent 6 generated in situ
from (diacetoxyiodo)benzene and sodium bisulfate
Oxidation of Alkenes with Oligomeric Iodosylbenzene Sulfate
(6) Generated In Situ: General Procedure
Solid PhI(OAc)2 (161 mg, 0.5 mmol), NaHSO4·H2O (69 mg, 0.5
mmol), the alkene (0.5 mmol), and two drops of H2O (about 34 mg)
were mixed in a mortar, and the mixture was intensively ground for
0.5–1 min. The mixture was then extracted with Et2O, and the or-
ganic products were separated by column chromatography [hexanes
then EtOAc–hexanes (1:5)]. Products 9, 12, 13, and 15 were isolat-
In conclusion, our study showed that oligomeric iodosyl-
benzene sulfate 6 is a readily available, stable, and versa-
tile water-soluble reagent for the oxidation of sulfides and
alkenes. The reactivity pattern of this reagent is similar to
that of relatively unstable activated monomeric iodosyl-
benzene complexes, such as 1. Furthermore, reagent 6 can ed as their 2,4-dinitrophenylhydrazones by adding 4–5 mL of a
standard soln of 2,4-dinitrophenylhydrazine [prepared from 2,4-
be conveniently generated in situ from (diacetoxy-
dinitrophenylhydrazine (3 g), concd H2SO4 (15 mL), EtOH (70
iodo)benzene and sodium bisulfate, and used without iso-
mL), and H2O (20 mL)]. The crystals that formed were filtered off,
lation for subsequent oxidations in aqueous solution or
washed with EtOH, dried, and recrystallized (EtOH).
under solvent-free conditions.
Phenylacetaldehyde (12)
Yield: 86% [isolated as 2,4-dinitrophenylhydrazone; mp 120–
121 °C (Lit.16 121 °C)].
All melting points were determined by using a Boetius melting
point apparatus and are uncorrected. 1H and 13C NMR spectra were
recorded on a Bruker AM-200 NMR spectrometer (200 and 50
1-Phenylacetone (13)
Yield: 83% [isolated as 2,4-dinitrophenylhydrazone, mp 157–
158 °C (Lit.16 156 °C)].
MHz) with TMS as the internal standard; chemical shifts are report-
ed in parts per million (ppm). GC-MS spectra were obtained by us-
Synthesis 2009, No. 15, 2505–2508 © Thieme Stuttgart · New York

2508
M. S. Yusubov et al.
PAPER
L. A., Ed.; Wiley: Chichester, 2004, DOI: 10.1002/
047084289X.ri039.pub3. (b) Stang, P. J.; Zhdankin, V. V.
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ARKIVOC 2009, (i), 1.
1,2-Diphenylethanone (10)
Yield: 97%; mp 59–60 °C (Lit.16 60 °C).
1H NMR (200 MHz, CDCl3): d = 4.24 (s, 2 H, CH2), 7.27 (m, 5 H),
7.43 (m, 3 H), 8.00 (dd, J = 1.6, 7.0 Hz, 2 H, Harom).
13C NMR (50 MHz, CDCl3): d = 45.26 (CH2), 126.63, 128.34,
128.44, 129.04, 129.22, 132.66, 134.43, 126.60 (C arom.), 196.32
(CO).
(4) A violent explosion of iodosylbenzene upon drying at a high
temperature under vacuum has been reported: McQuaid, K.
M.; Pettus, T. R. R. Synlett 2004, 2403.
Cyclopentanecarbaldehyde (9)
Yield: 39% [isolated as 2,4-dinitrophenylhydrazone, mp 154–
156 °C (Lit.17 156–157 °C)].
(5) Ochiai, M.; Sueda, T.; Miyamoto, K.; Kiprof, P.; Zhdankin,
V. V. Angew. Chem. Int. Ed. 2006, 45, 8203.
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(b) Ochiai, M.; Miyamoto, K.; Yokota, Y.; Suefuji, T.;
Shiro, M. Angew. Chem. Int. Ed. 2005, 44, 75.
1-Cyclopentylethanone (15)
Yield: 45% [isolated as 2,4-dinitrophenylhydrazone, mp 115–
116 °C (EtOH)].
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(8) Alcock, N. W.; Waddington, T. C. J. Chem. Soc. 1963, 4103.
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(b) Kasumov, T. M.; Brel, V. K.; Koz’min, A. S.; Zefirov, N.
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Anal. Calcd. for C13H16N4O4: C, 53.42; H, 5.52; N, 19.17. Found:
C, 53.15; H, 5.76; N, 20.01.
Acknowledgment
V.V.Z. thanks the National Science Foundation (research grant
CHE-0702734) for support. K.W.C. and M.S.Y. are grateful for the
support of the Brain Korea 21 program of the Republic of Korea.
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Synthesis 2009, No. 15, 2505–2508 © Thieme Stuttgart · New York