Preparation and reductive decomposition of 2-iodoxybenzenesulfonic acid. X-ray crystal structure of 1-hydroxy-1H-1,2,3-benziodoxathiole 3,3-dioxide

Article abstract of DOI:10.1002/ejoc.200600683

2-Iodoxybenzenesulfonic acid (in a cyclic tautomeric form of 1-hydroxy-1H-1,2,3-benziodoxathiole 1,3,3-trioxide), a thiaanalog of 2-iodoxybenzoic acid (IBX) and a potentially important oxidizing reagent, was prepared by two different pathways: direct oxid

Full text of DOI:10.1002/ejoc.200600683

SHORT COMMUNICATION
DOI: 10.1002/ejoc.200600683
Preparation and Reductive Decomposition of 2-Iodoxybenzenesulfonic Acid.
X-ray Crystal Structure of 1-Hydroxy-1H-1,2,3-benziodoxathiole 3,3-Dioxide
Alexey Y. Koposov,[a] Dmitry N. Litvinov,[a] Viktor V. Zhdankin,*[a] Michael J. Ferguson,[b]
Robert McDonald,[b] and Rik R. Tykwinski[b]
Keywords: Iodine / Hypervalent compounds / Oxidation / X-ray diffraction
2-Iodoxybenzenesulfonic acid (in a cyclic tautomeric form of
1-hydroxy-1H-1,2,3-benziodoxathiole 1,3,3-trioxide), a thia-
analog of 2-iodoxybenzoic acid (IBX) and a potentially im-
portant oxidizing reagent, was prepared by two different
pathways: direct oxidation of 2-iodobenzenesulfonic acid
and hydrolysis of the methyl ester of 2-iodylbenzenesulfonic
acid. The resulting l-hydroxy-1H-1,2,3-benziodoxathiole
1,3,3-trioxide was found to be thermally unstable and highly
reactive towards organic solvents. The structure of its re-
ductive decomposition product, l-hydroxy-1H-1,2,3-benzi-
odoxathiole 3,3-dioxide (the cyclic tautomeric form of 2-iodo-
sylbenzenesulfonic acid), was established by single-crystal
X-ray diffraction.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
lar, investigations from our group have resulted in a series
of stable and soluble IBX derivatives: IBX-amides 2,[5a]
IBX-esters 3,[5b] as well as their sulfur-containing analogs
2-iodylsulfonamides 4,[5c] and 2-iodylsulfonate esters 5 (Fig-
ure 1).[5d] The synthesis of polymer-supported IBX deriva-
tives has been reported as well.[6,7] All of these reagents have
demonstrated promising oxidizing abilities toward alcohols
and sulfides. It should also be noted that the oxidizing
properties of the sulfur-containing analogs of IBX-esters
and amides (structures 4 and 5) were noticeably stronger in
Introduction
During the past decade, the chemistry of pentavalent iod-
ine oxidizing reagents has attracted significant research
interest.[1] Various types of hypervalent iodine(V) com-
pounds (λ5-iodanes) have been reported and some of them
have emerged as reagents of choice for synthetically useful
oxidative transformations because of their high chemoselec-
tivity, mild reaction conditions, and environmentally benign
nature. Cyclic and pseudocyclic hypervalent iodine reagents
that are designed on the basis of the benziodoxole system
represent an especially important class of iodanes with rich
and synthetically useful chemistry.[1–3] In particular, hetero-
cyclic λ5-iodane 1-hydroxy-1H-1λ5-benzo[d][1,2]iodoxol-
1,3-dione (1a), known under the name of its tautomeric
form of 2-iodoxybenzoic acid (IBX) (1b), has received wide-
spread application in organic synthesis as a highly efficient
and mild oxidant that can be used for the selective oxi-
dation of primary and secondary alcohols and for a variety
of other important oxidations.[2,3] However, the explosive
character and low solubility of IBX in common organic sol-
vents except DMSO restrict practical application of this
reagent.
Several IBX derivatives and analogs have been reported
in the literature by different research groups.[4–6] In particu-
[a] Department of Chemistry and Biochemistry, University of Min-
nesota Duluth,
Duluth, Minnesota 55812, USA
E-mail: vzhdanki@d.umn.edu
[b] Department of Chemistry, University of Alberta,
Edmonton, Alberta, T6G 2G2 Canada
E-mail: rik.tykwinski@ualberta.ca
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Figure 1. 2-Iodoxybenzoic acid (IBX) and its derivatives and ana-
logs.
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V. V. Zhdankin et al.
SHORT COMMUNICATION
comparison with those of the original IBX-esters and point the signal of C–I(III) in reductive decomposition
amides, which is probably due to the greater electron-with- product 9[9,10] emerges at about 140 ppm. The contact of
drawing nature of the sulfonyl group.[5c,5d]
compound 8 with methanol or DMSO leads to almost in-
With the importance of the pentavalent iodine reagents stantaneous reduction to benziodoxathiole 9 as indicated
taken into consideration, and IBX especially, we have at- by 13C NMR spectroscopy. Because of the low stability of
tempted to prepare the analog of IBX bearing the sulfonyl compound 8, we were not able to investigate its oxidative
group in the five-membered ring with a goal to further in- reactivity towards organic substrates; however, its high reac-
vestigate the influence of the ortho-substituent on the sta- tivity toward methanol and DMSO is indicative of the
bility and the reactivity of cyclic iodine reagents. Herein, we stronger oxidizing properties compared with those of IBX.
report the preparation of 2-iodoxybenzenesulfonic acid (8)
Several attempts were performed to grow single-crystals
as well as the structure of the product of its reductive de- of compound 8 suitable for X-ray analysis with the use of
composition, l-hydroxy-1H-1,2,3-benziodoxathiole 3,3-di- methanol, methanol/acetonitrile, or acetonitrile as solvents.
oxide (9).
In each case, however, only benziodoxathiole 9, which re-
sults from the reductive decomposition of compound 8, was
identified by X-ray analysis as the final crystalline material.
Depending on the solvent used for crystallization, three dif-
ferent crystal structures of product 9 were determined: (1)
Results and Discussion
We have developed two different synthetic approaches to
compound 8 (Scheme 1). The first approach (method A)
involves the hydrolysis of known ester 6;[5c] the second pro-
cedure (method B) involves the direct oxidation of 2-iodo-
benzenesulfonic acid (7) by a procedure similar to that used
for the preparation of IBX.[8] The first approach affords
analytically pure product 8 whereas the direct oxidation of
iodobenzenesulfonic acid (7) by oxone gives the final prod-
uct that is, according to elemental analysis, contaminated
with approximately 10% of inorganic impurities. Because
of the very high solubility of product 8 in water, it is almost
impossible to separate all inorganic impurities left from the
oxidation when method B is used, and therefore, method A
provides a better synthetic approach to 2-iodylbenzenesul-
fonic acid. Product 8 is an unstable compound that decom-
poses to form iodine(III) heterocycle 9[9] after several days
of storage or upon contact with organic solvents, such as
acetonitrile, DMSO, and methanol. It is insoluble in chloro-
form, dichloromethane, and other nonpolar solvents.
¯
space group P1, for crystals of a hydrate obtained from
methanol (structure 9a), (2) space group P21/n for crystals
obtained from methanol/acetonitrile (structure 9b), and (3)
space group P212121 for crystals obtained from acetonitrile
(structure 9c). Molecular structure of benziodoxathiole 9
crystallized in the P212121 space group (crystal structure 9c)
is shown in Figure 2. Selected bond lengths for structure 9c
in comparison to the similar known structure of 1-hydroxy-
5-methyl-1H-1,2,3-benziodoxathiole 3,3-dioxide (10)[10] are
listed in the Table 1.
Figure 2. Perspective view of the molecular structure of benziodox-
Scheme 1.
athiole
9 crystallized in the P212121 space group (crystal
structure 9c). Non-hydrogen atoms are represented by Gaussian
Despite the low stability and high reactivity of 8 towards
ellipsoids at the 20% probability level.
organic solvents, we were able to obtain reliable identifica-
1
tion data including H- and 13C NMR, IR, HRMS, and
For structures 9a–c, the intramolecular bond lengths are
elemental analysis. In particular, the high resolution ES approximately the same; however, the secondary bonding
mass spectrum of compound 8 displays the appropriate mo- motifs are different (Figure 3). In all three structures the
lecular ion, and the elemental analysis is in agreement with hypervalent iodine center has square-planar geometry,
the monohydrate formula 8·H2O. The 13C NMR spectrum which is typical for iodine(III) compounds. In the case of
¯
of a freshly prepared sample of compound 8 in D2O shows the P1 space group (structure 9a), two molecules related by
the signal of the ipso-carbon, C–I(V), at about 143 ppm, an inversion center are found in the unit cell. These two
which is characteristic of iodylarenes;[5] this signal disap- molecules are strongly connected by hydrogen bonds
pears when the sample is stored for several days at which [1.904(6)–1.938(7) Å] that are formed by the hydrogen
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Preparation and Decomposition of 2-Iodoxybenzenesulfonic Acid
SHORT COMMUNICATION
Table 1. Selected bond lengths for structure 9 in comparison to the atoms of the cocrystallized water and the oxygen atoms of
known structure of 1-hydroxy-5-methyl-1H-1,2,3-benziodoxathiole
the sulfonyl groups, as shown in Figure 3a. Another short
contact that is found in this structure is the secondary
3,3-dioxide (10).[10]
bonding between the oxygen atom of the water molecule
and the hypervalent iodine from the neighboring unit cell
[3.005(2) Å]. This additional interaction provides the con-
nection between the two dimers and builds a three-dimen-
sional polymeric network. In the second space group, P21/
n (structure 9b), two crystallographically independent mole-
cules are found in the unit cell. Weak secondary bonding
Bond[a]
Structure 9c
Benziodoxathiole 10
[3.004(3) Å] interactions between an iodine atom from one
of the molecules and a sulfonyl oxygen from the cycle of a
neighboring molecule link the two molecules. The second
type of secondary bonding in this structure is due to the
intermolecular interaction between the hypervalent iodine
and a sulfonyl oxygen from a second molecule [2.807(3) Å].
In the last space group, P212121 (structure 9c), one molecule
is found in the asymmetric unit. In this case, secondary
bonding also plays a significant role in the arrangement of
I–O1
I–O2
I–C1
S–O2
S–O3
S–O4
S–C2
1.9334(18)
2.3809(19)
2.116(3)
1.473(2)
1.438(2)
1.438(2)
1.775(3)
1.933(5)
2.372(5)
2.125(6)
1.440(5)
1.406(6)
1.415(9)
1.759(6)
[a] The numbering scheme refers to the thermal ellipsoid projection
shown in Figure 2.
¯
Figure 3. a) Perspective view of the crystal packing of benziodoxathiole 9a in space group P1. Selected distances [Å]: O3"···H1SB* 1.94;
O4···H1SB* 1.90; O1S···I 3.005(2); H1O···O1S 1.86. b) Perspective view of the crystal packing of benziodoxathiole 9b in space group
P21/n. Selected distances [Å]: O12···I2 3.004(3); O13"···I1 2.807(3); H11O···O23Ј 1.87; H21O···O11Ј 1.93. c) Perspective view of the crystal
packing of benziodoxathiole 9c in space group P212121. Selected distances [Å]: I···O3Ј 2.847(2); H1O"···O4 1.90. In all cases, hydrogen
atoms are omitted for clarity, and non-hydrogen atoms are represented by Gaussian ellipsoids at the 20% probability level.
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V. V. Zhdankin et al.
SHORT COMMUNICATION
hydroxy-1H-1,2,3-benziodoxathiole 3,3-dioxide in crystal form 9a.
ES-MS: m/z (%) = 300.901 (100) [M + H]+.
the molecules in the solid state; the strong interaction be-
tween a sulfonyl oxygen and the iodine center [2.847(2) Å]
is the main motif in this crystal structure. It is worth noting
Crystal Data for 9a·H2O: X-ray intensity data were collected at–
that in all three cases (9a–c), hydrogen bonding between the 80 °C with
a Bruker PLATFORM/SMART 1000 CCD dif-
fractometer with Mo-Kα radiation (λ = 0.71073 Å) with the use of
hydroxylic hydrogens and the oxygen atoms of different
types are present, which makes the three-dimensional poly-
meric network even stronger.
a crystal with dimensions of 0.60×0.12×0.10 mm. C6H7IO5S, FW
= 318.08 g/mol , triclinic space group = P1 (No. 2), unit cell dimen-
3
¯
sions: a = 7.8244(6) Å, b = 7.9472(6) Å, c = 8.0000(7) Å, α =
68.0284(11)°, β = 86.6496(11)°, γ = 80.1374(10)°, V = 454.50(6) Å3,
Z = 2, ρcalcd. = 2.324 g/cm3, µ = 3.739 mm–1, 2θmax = 52.74°, R1(F)
= 0.0189 for 1771 reflections with Fo2 Ն 2σ(Fo2), wR2(F2) = 0.0481
Conclusions
for 1829 independent reflections [Fo Ն –3σ(Fo2)] and 126 param-
2
In conclusion, we have reported the preparation and
spectroscopic characterization of 2-iodoxybenzenesulfonic
acid [in a cyclic tautomeric form of l-hydroxy-1H-1,2,3-
benziodoxathiole 1,3,3-trioxide (8)], which is a thia-analog
of 2-iodoxybenzoic acid (IBX) and a potentially important
oxidizing reagent. This compound was prepared by two dif-
ferent pathways: direct oxidation of 2-iodobenzenesulfonic
acid or hydrolysis of the methyl ester of 2-iodylbenzenesul-
fonic acid. The resulting l-hydroxy-1H-1,2,3-benziodoxathi-
ole 1,3,3-trioxide was found to be unstable and highly reac-
tive towards organic solvents. The structure of its reductive
decomposition product, l-hydroxy-1H-1,2,3-benziodoxathi-
ole 3,3-dioxide (9) (the cyclic tautomeric form of 2-iodoso-
benzenesulfonic acid), was established by single-crystal X-
ray diffraction analysis.
eters, GOF(F2) = 1.058 [Fo Ն –3σ(Fo2)].
2
Slow evaporation of a methanol/acetonitrile (1:1) solution of com-
pound 8 over a 3–5 d period at room temperature afforded colorless
crystals of l-hydroxy-1H-1,2,3-benziodoxathiole 3,3-dioxide in
crystal form 9b.
Crystal Data for 9b: X-ray intensity data were collected at –80 °C
with a Bruker PLATFORM/SMART 1000 CCD diffractometer
with Mo-Kα radiation (λ = 0.71073 Å) with the use of a crystal
with dimensions of 0.42×0.33×0.05 mm. C6H5IO4S, FW
=
300.06 g/mol3, monoclinic space group = P21/n (No. 14), unit cell
dimensions a = 12.7784(13) Å, b = 9.2753(9) Å, c = 14.7718(15) Å,
β = 109.456(2)°, V = 1650.8(3) Å3, Z = 8, ρcalcd. = 2.415 g/cm3, µ
= 4.102 mm–1, 2θmax = 52.70°, R1(F) = 0.0302 for 2996 reflections
with Fo Ն 2σ(Fo2), wR2(F2) = 0.0810 for 3356 independent reflec-
2
tions [Fo Ն –3σ(Fo2)] and 219 parameters, GOF(F2) = 1.074
2
2
[Fo Ն –3σ(Fo2)].
Slow evaporation of an acetonitrile solution of compound 8 over
a 3–5 d period at room temperature afforded colorless crystals of
l-hydroxy-1H-1,2,3-benziodoxathiole 3,3-dioxide in crystal form 9c.
Experimental Section
Preparation of l-Hydroxy-1H-1,2,3-benziodoxathiole 1,3,3-trioxide
(8)
Crystal Data for 9c: X-ray intensity data were collected at –80 °C
with a Bruker PLATFORM/SMART 1000 CCD diffractometer
with Mo-Kα radiation (λ = 0.71073 Å) with the use of a crystal
Method A (by hydrolysis of methyl sulfonate 6): 1-Iodyl-2-(meth-
oxysulfonyl)benzene 6 (0.103 g, 0.31 mmol) was placed in a round-
bottomed flask and distilled water (5 mL) was added. The mixture
was heated at 60 °C, stirred for 3 min, and the reaction mixture
was then cooled to room temperature and attached to a vacuum
system. After complete removal of the water, pure monohydrate 8
was obtained as pale-yellow glass. Yield 0.104 g, 100%. M.p. 97–
99 °C (dec). IR (NaCl): 3442, 3070, 1628, 1449, 1425, 1183, 1142,
1104, 1040, 762, 737, 647, 614, 557 cm–1. 1H NMR (300 MHz,
D2O, CDCl3 external standard): δ = 8.28 (dd, J = 8.3 and 0.9 Hz,
1 H), 8.03 (m, 2 H), 7.91 (td, J = 7.9 and 0.7 Hz, 1 H) ppm. 13C
NMR (75.5 MHz, D2O, CDCl3 external standard): δ = 143.0,
139.6, 134.3, 133.6, 128.4, 122.5 ppm. C6H5IO5S·H2O (334.09):
calcd. C 21.57, H 2.11, I 37.99, S 9.60; found C 21.75, H 2.03, I
37.27, S 9.66. ES-MS: m/z (%) = 338.879 (50) [M + Na]+.
with dimensions of 0.50×0.12×0.04 mm. C6H5IO4S, FW
=
300.06 g/mol3, orthorhombic space group = P212121 (No. 19), unit
cell dimensions
a = 5.1895(3) Å, b = 11.7496(6) Å, c =
13.7880(7) Å, V = 840.72(8) Å3, Z = 4, ρcalcd. = 2.371 g/cm3, µ =
4.027 mm–1, 2θmax = 52.74°, R1(F) = 0.0142 for 1701 reflections
2
with Fo Ն 2σ(Fo2), wR2(F2) = 0.0360 for 1725 independent reflec-
2
2
tions [Fo Ն –3σ(Fo2)] and 110 parameters, GOF(F2) = 1.039 [Fo
Ն –3σ(Fo2)].
CCDC-616821 to -616823 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of the arti-
cle): Experimental procedures, spectroscopic and other data for the
new compounds.
Method B (by direct oxidation of 2-iodobenzenesulfonic acid): To a
stirred mixture of 2-iodobenzenesulfonic acid (0.5 g, 1.7 mmol) in
distilled water (4.25 mL) heated at 70 °C was added oxone (3.25 g)
in small portions over a 15 min period. After the addition was com-
plete, the reaction mixture was stirred for an additional 1 h and
cooled to room temperature. Acetonitrile (9 mL) was added to the
reaction mixture, and the resulting inorganic precipitate was re-
moved by filtration and extracted with acetonitrile/water (2:1;
3×2 mL). The extracts were combined and concentrated in vacuo
to afford product 8.
Acknowledgments
This work was supported by a research grant from the National
Science Foundation (CHE-0353541), NSF-MRI award CHE-
0416157, the Natural Sciences and Engineering Research Council
of Canada, and the University of Alberta.
1-Hydroxy-1H-1,2,3-benziodoxathiole 3,3-Dioxide 9 by Reductive
Decomposition of 8
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Preparation and Decomposition of 2-Iodoxybenzenesulfonic Acid
SHORT COMMUNICATION
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Received: August 5, 2006
Published Online: September 11, 2006
Eur. J. Org. Chem. 2006, 4791–4795
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