Preparation, X-ray structure, and oxidative reactivity of N-(2-iodylphenyl)tosylamides and 2-iodylphenyl tosylate: Iodylarenes stabilized by ortho-substitution with a sulfonyl group

Article abstract of DOI:10.1021/jo901638f

(Chemical Equation Presented) New tosyl derivatives of 2-iodylaniline and 2-iodylphenol were prepared by the dimethyldioxirane oxidation of the corresponding 2-iodophenyltosylamides or 2-iodophenyl tosylate and isolated as stable, microcrystalline products. Single-crystal X-ray diffraction analysis of N-(2-iodylphenyl)-N,4-dimethylbenzenesulfonamide revealed pseudocyclic structure formed by intramolecular I...O interactions between the hypervalent iodine center and the sulfonyl oxygens in the tosyl group. This tosylamide has an excellent solubility in organic solvents and is a potentially useful hypervalent iodine oxidant.

Full text of DOI:10.1021/jo901638f

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transformations due to their high chemoselectivity, mild reac-
Preparation, X-ray Structure, and Oxidative
Reactivity of N-(2-Iodylphenyl)tosylamides and
2-Iodylphenyl Tosylate: Iodylarenes Stabilized by
Ortho-Substitution with a Sulfonyl Group
tion conditions, and environmentally benign nature. Cyclic
and pseudocyclic hypervalent iodine reagents based on the
benziodoxole system represent an especially important class of
iodanes with rich and synthetically useful chemistry. In parti-
cular, the heterocyclic λ5-iodane, 1-hydroxy-1-oxo-1H-1λ5-
benzo[d][1,2]iodoxol-3-one (1), known under the name of its
tautomeric form of 2-iodoxybenzoic acid (IBX), has received
widespread application in organic synthesis as a highly efficient
and mild oxidant that can be used for selective oxidation of
primary and secondary alcohols and for a variety of other
important oxidations.1,2 However, the explosive character and
low solubility of IBX in common organic solvents except
DMSO restrict practical application of this reagent.
Artur K. Mailyan, Ivan M. Geraskin, Victor N. Nemykin,*
and Viktor V. Zhdankin*
Department of Chemistry and Biochemistry, University of
Minnesota-Duluth, Duluth, Minnesota 55812
vzhdanki@d.umn.edu
Received July 28, 2009
New tosyl derivatives of 2-iodylaniline and 2-iodylphenol
were prepared by the dimethyldioxirane oxidation of the
corresponding 2-iodophenyltosylamides or 2-iodophenyl
tosylate and isolated as stable, microcrystalline products.
Single-crystal X-ray diffraction analysis of N-(2-iodyl-
phenyl)-N,4-dimethylbenzenesulfonamide revealed pseu-
The low solubility of IBX 1arises from strong intermolecular
secondary I O contacts, hydrogen bonding, and π-stacking
3 3 3
observed for IBX in the solid state.3 Several research groups
have tried to overcome this preparative limitation by perform-
ing oxidation at elevated temperatures,4a using an ionic liquid
and water as a reaction medium,4b or functionalizing IBX
aromatic core.4c,d Also, several solid-supported reagents in
which IBX scaffold is linked to a polymer have been repor-
ted.5 Another fruitful approach initially proposed by Protasie-
wicz6 consists of incorporation of an ortho-substituent into
docyclic structure formed by intramolecular I O inter-
3 3 3
actions between the hypervalent iodine center and the
sulfonyl oxygens in the tosyl group. This tosylamide has
an excellent solubility in organic solvents and is a poten-
tially useful hypervalent iodine oxidant.
(2) (a) Nicolaou, K. C.; Mathison, C. J. N.; Montagnon, T. J. Am. Chem.
Soc. 2004, 126, 5192–5201. (b) Nicolaou, K. C.; Baran, P. S.; Zhong, Y. L.;
Sugita, K. J. Am. Chem. Soc. 2002, 124, 2212-2220 and references cited
therein. (c) Zhdankin, V. V. Curr. Org. Synth. 2005, 2, 121–145. (d) Moorthy, J.
N.; Senapati, K.; Kumar, S. J. Org. Chem. 2009, 74, 6287–6290. (e) Drouet, F.;
Fontaine, P.; Masson, G.; Zhu, J. Synthesis 2009, 1370–1374. (f) Kuhakarn, C.;
Panchan, W.; Chiampanichayakul, S.; Samakkanad, N.; Pohmakotr, M.; Reutra-
kul, V.; Jaipetch, T. Synthesis 2009, 929–934. (g) Ojha, L. R.; Kudugunti, S.;
Maddukuri, P. P.; Kommareddy, A.; Gunna, M. R.; Dokuparthi, P.; Gottam, H. B.;
Botha, K. K.; Parapati, D. R.; Vinod, T. K. Synlett 2009, 117–121.
During the past decade the chemistry of pentavalent iodine
oxidizing reagents has attracted a significant research in-
terest.1 Various types of hypervalent iodine(V) compounds
(λ5-iodanes) have been reported and some of them have
emerged as reagents of choice for synthetically useful oxidative
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Perkin Trans. 2 1997, 589–591.
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C.; Zheng, Q.-G. Org. Lett. 2003, 5, 3321–3323. (c) Thottumkara, A. P.; Vinod, T.
K. Tetrahedron Lett. 2002, 43, 569–572. (d) Richardson, R. D.; Zayed, J. M.;
Altermann, S.; Smith, D.; Wirth, T. Angew. Chem., Int. Ed. 2007, 46, 6529–6532.
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4394. (b) Sorg, G.; Mengei, A.; Jung, G.; Rademann, J. Angew. Chem., Int.
Ed. 2001, 40, 4395–4397. (c) Reed, N. N.; Delgado, M.; Hereford, K.;
Clapham, B.; Janda, K. D. Bioorg. Med. Chem. Lett. 2002, 12, 2047–2049.
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Zhang, H.; Hatton, T. A. Chem. Mater. 2008, 20, 2001–2008.
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Springer-Verlag: Berlin, Germany, 2003. (c) Koser, G. F. Adv. Heterocycl. Chem.
2004, 86, 225–292. (d) Ladziata, U.; Zhdankin, V. V. Synlett 2007, 527–537. (e)
Wirth, T. Angew. Chem., Int. Ed. 2005, 44, 3656–3665. (f) Ladziata, U.;
Zhdankin, V. V. ARKIVOC 2006, 9, 26–58. (g) Zhdankin, V. V.; Stang, P. J.
Chem. Rev. 2008, 108, 5299–5358. (h) Zhdankin, V. V. ARKIVOC 2009, 1, 1–
62. (i) Richardson, R. D.; Wirth, T. Angew. Chem., Int. Ed. 2006, 45, 4402–4404.
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Published on Web 10/01/2009
DOI: 10.1021/jo901638f
r
2009 American Chemical Society

Mailyan et al.
JOCNote
iodylarene (e.g., phosphine oxide 56b or sulfone 66a) thus
resulting in intramolecular secondary bonding. This ortho-
stabilization leads to a partial disruption of the polymeric
network, and consequently enhances solubility. More recently,
investigations from our group have resulted in a series of stable
and soluble IBX analogues: IBX-amides 2,7a IBX-esters 3,7b as
well as 2-iodylbenzenesulfonamides 77c,d and 2-iodylbenzene-
sulfonate esters 8.7e According to X-ray data, a planar pseudo-
benziodoxole moiety due to the intramolecular nonbonding
iodine-oxygen interaction is a key structural feature present in
this series of compounds.6,7 Readily available hypervalent
iodine reagents 2 and 3 possess reactivity similar to that of
IBX and Dess-Martin periodinane, and proved to be useful
oxidizing reagents toward alcohols7 and sulfides.8 The synth-
esis of polymer-supported IBX esters and amides has been
reported as well.9 Recently, we have described the preparation
and oxidative reactivity of N-(2-iodylphenyl)acylamides
(NIPA, 4), which are soluble and stable IBX analogues having
pseudo-benziodoxazine structure.10
SCHEME 1. Preparation of 2-Iodophenyltosylamides 13 and 14
To further explore the effects of ortho-substituents in the
analogous to N-(2-iodylphenyl)acylamides 4 pseudo-six-
membered heterocycles, we considered the preparation of
iodylarenes derived from the readily available tosyl deriva-
tives of 2-iodoaniline and 2-iodophenol. Herein we report
the preparation and study of two new N-(2-iodylphenyl)to-
sylamides and the 2-iodylphenyl tosylate.
SCHEME 2. Preparation of 2-Iodophenyl Tosylate 17
Synthesis of N-(2-iodylphenyl)tosylamides 13 and 14 was
performed by the tosylation of commercially available
2-iodoaniline 9 with tosyl chloride in pyridine, followed by the
alkylation of tosylamide 10 with iodomethane or additional
tosylation with TsCl. Oxidation of the iodides 11 and 12 with
3,3-dimethyldioxirane according to the previously reported
procedure7e afforded N-(2-iodylphenyl)tosylamides 13 and
14 in good yields (Scheme 1). Products 13 and 14 were
isolated as white microcrystalline compounds and were
analyzed by NMR spectroscopy. In particular, 13C NMR
spectra of both products 13 and 14 showed characteristic
signals of the ipso-carbon, C-IO2, at about 151 ppm, which is
typical of iodylarenes.7 Both iodylarene derivatives are
stable at room temperature and do not possess any explosive
properties upon heating or impact. A slow decomposition
is observed during heating of compound 13 or 14 in a
capillary tube above the melting point. Compound 13 has
excellent solubility in chloroform and acetonitrile, while the
bis-tosylate 14 has a relatively low solubility in organic
solvents.
2-iodophenol 15, using 4-toluenesulfonyl chloride in DMF,
followed by the oxidation of the tosylate 16 with
3,3-dimethyldioxirane (Scheme 2). Product 17 was isolated
as a white, stable microcrystalline compound in excellent
yield and was identified by NMR spectroscopy and elemental
analysis. Specifically, the NMR spectra of this product
showed the appropriate pattern of protons and carbons
and a signal of the ipso-carbon, C-IO2, at about 147 ppm,
which is comparable with the tosylamides 13 and 14. The
same as the tosylamides, the tosylate 17 is indefinitely stable
at room temperature and does not have any explosive
properties. It has a low solubility in nonpolar solvents, but
is soluble in DMSO.
The structure of 2-iodophenyl tosylamide 13 was con-
firmed by single-crystal X-ray crystallography. The CA-
MERON diagrams of 13 are presented in Figures 1 and 2.
The X-ray data reveal eight molecules of 13 located in the
unit cell. The iodine atom forms two short I-O double bonds
with O(1) and O(2) atoms and a single bond with C(1). In
addition to these three covalent bonds, the molecular struc-
ture of 13 exhibits three short contacts between iodine center
and oxygen atoms forming overall pseudo-octahedral con-
figuration around iodine (Figure 2). These short contacts
Synthesis of the o-tosyloxy-substituted iodylarene 17
was performed by tosylation of commercially available
(7) (a) Zhdankin, V. V.; Koposov, A. Y.; Netzel, B. C.; Yashin, N. V.;
Rempel, B. P.; Ferguson, M. J.; Tykwinski, R. R. Angew. Chem., Int. Ed.
2003, 42, 2194–2196. (b) Zhdankin, V. V.; Koposov, A. Y.; Litvinov, D. N.;
Ferguson, M. J.; McDonald, R.; Luu, T.; Tykwinski, R. R. J. Org. Chem.
2005, 70, 6484–6491. (c) Koposov, A. Y.; Litvinov, D. N.; Zhdankin, V. V.
Tetrahedron Lett. 2004, 45, 2719–2721. (d) Koposov, A. Y.; Nemykin, V. N.;
Zhdankin, V. V. New J. Chem. 2005, 29, 998–1000. (e) Zhdankin, V. V.;
Goncharenko, R. N.; Litvinov, D. N.; Koposov, A. Y. ARKIVOC 2005, 4, 8–
18.
consist of one relatively weak intramolecular I O interac-
3 3 3
˚
tion (I(1)-O(3), 3.035(3) A) and two intermolecular inter-
actions between I(1) and O(1A) as well as I(1) and O(4B) with
˚
the former being short (2.727(3) A) and the later being
˚
relatively long (3.167(2) A).
(8) Koposov, A. Y.; Zhdankin, V. V. Synthesis 2005, 22–24.
(9) (a) Chung, W.-J.; Kim, D.-K.; Lee, Y.-S. Tetrahedron Lett. 2003, 44,
9251. (b) Kim, D.-K.; Chung, W.-J.; Lee, Y.-S. Synlett 2005, 279. (c)
Lecarpentier, P.; Crosignani, S.; Linclau, B. Molecular Diversity 2005, 9,
341–351.
(10) (a) Ladziata, U.; Koposov, A. Y.; Lo, K. Y.; Willging, J.; Nemykin,
V. N.; Zhdankin, V. V. Angew. Chem., Int. Ed. 2005, 44, 7127–7131. (b)
Ladziata, U.; Willging, J.; Zhdankin, V. V. Org. Lett. 2006, 8, 167–170.
The intramolecular secondary bonding between the hy-
pervalent iodine center and the oxygen atom in the ortho-
˚
substituent [I(1) O(3) 3.035(3) A] in 13 is noticeably
3 3 3
weaker compared to the I O secondary bonding of 2.647
3 3 3
˚
A previously reported for the pseudo-benziodoxazine struc-
ture 4 and close to the sum of van der Waals radii of iodine
J. Org. Chem. Vol. 74, No. 21, 2009 8445

Mailyan et al.
JOCNote
FIGURE 1. Perspective view of N-(2-iodylphenyl)tosylamide 13
˚
with 50% ellipsoid probability. Selected distances [A] and angles
[deg]: I(1)-C(1) 2.104(3), I(1)-O(1) 1.807(2), I(1)-O(2) 1.786(3),
C(1)-I(1)-O(1) 97.89(11), C(1)-I(1)-O(2) 99.39(13), O(1)-I(1)-
O(2) 100.13(11).
and oxygen (3.55 A).7d,10a,11 This difference can be explained
˚
by the longer N-S bond distance in 13 as compared to the
N-C bond distance in 4. Nevertheless, this additional inter-
action in the molecule of 13 partially replaces intermolecular
secondary bonding between the iodine atom I(1) and the
oxygen atom (O1A) of the iodyl group in the neighboring
molecule (Figure 2) and thus weakens the polymeric network
typical of iodylarenes in the solid state. It is particularly
important that this structural feature leads to the excellent
solubility of compound 13 in nonpolar solvents such as
chloroform.
We were not able to grow single crystals of ditosylamide 14
and tosylate 17 because of the low solubility of these com-
pounds. It can be hypothesized that the polymeric character of
these compounds is explained by a significant intermolecular
secondary interaction between the hypervalent iodine center
and the sulfonyl oxygens in tosyl groups of neighboring mole-
FIGURE 2. Intra- and intermolecular secondary bonding in 13.
˚
Selected distances [A]: I(1) O(1A) 2.727(3), I(1) O(4B)
3 3 3
3 3 3
3.167(2), I(1)-O(3) 3.035(3). Tolyl groups of molecules A (located
at 3/2 - x, 1/2 - y, 1 - z position) and B (located at 3/2 - x, 1/2 þ y,
3/2 - z position) are omitted for clarity.
after 6 h under reflux conditions in acetonitrile. The details of
these oxidations are provided in the Supporting Informa-
tion. In comparison with tosylamide 13, the previously
reported IBX esters 3 showed even lower reactivity toward
alcohols (the oxidation with 3 required acid catalysis),7b
while IBX amides 27a demonstrated higher reactivity and
were capable of oxidizing aliphatic alcohols.
In conclusion, we have reported the preparation of new
tosyl derivatives of 2-iodylaniline and 2-iodylphenol. Single-
crystal X-ray diffraction analysis of N-(2-iodylphenyl)-N,4-
dimethylbenzenesulfonamide, 13, revealed the presence of
intramolecular secondary bonding between the hypervalent
iodine center and the oxygen atom in the ortho-substituent.
This additional interaction in the molecule of 13 partially
replaces intermolecular secondary bonding between the
iodine atom and the oxygen atom of the iodyl group of the
neighboring molecule and thus weakens the polymeric net-
work typical of iodylarenes in the solid state. Due to this
structural feature compound 13 has excellent solubility in
nonpolar solvents such as chloroform. Compound 13 is an
efficient oxidant toward organic substrates and can oxidize
benzylic alcohols to the respective aldehydes or ketones.
cules, similar to the I(1) O(4B) secondary bonding in struc-
3 3 3
ture 13 (Figure 2). Indeed, the previously reported 2-iodyl-
phenol ethers, in which the Ts moiety of structure 17 is replaced
with an alkyl group, have excellent solubility in organic sol-
vents.12 Such a striking difference in the solubility of structurally
similar 2-iodylphenol alkyl ethers and the 2-iodylphenol tosy-
late 17 is indicative of the importance of intermolecular second-
ary interactions involving the tosyl group.
Due to its excellent solubility in organic solvents, N-(2-
iodylphenyl)tosylamide 13 is a potentially useful hypervalent
iodine oxidant. We have found that the oxidizing reactivity
of compound 13 is generally similar to the previously re-
ported N-(2-iodylphenyl)acylamides (NIPA, 4). In particu-
lar, the tosylamide 13 reacts with various benzylic alcohols
(e.g., benzyl alcohol, 4-nitro- and 4-methoxy-substituted
benzyl alcohols, pyridin-3-ylmethanol, thiophen-2-ylmetha-
nol, and 1-phenylethanol) in acetonitrile under mild condi-
tions to afford the respective aldehydes or ketones in
quantitative yield in 4-6 h. The oxidation of aliphatic and
allylic alcohols proceeds much slower, even at elevated
temperatures. For example, geraniol is oxidized by com-
pound 13 to the respective aldehyde with only 4% conversion
Experimental Section
Additional experimental details can be found in the Support-
ing Information.
N-(2-Iodylphenyl)-N,4-dimethylbenzenesulfonamide (13). A
freshly prepared 0.1 M solution of dimethyldioxirane in dichlor-
omethane13 (120 mL, approximately 12 mmol) was added to a
(11) For a detailed discussion on secondary bonding in hypervalent
iodine compounds, see: Nemykin, V. N.; Koposov, A. Y.; Netzel, B. C.;
Yusubov, M. S.; Zhdankin, V. V. Inorg. Chem. 2009, 48, 4908–4917.
(12) Koposov, A. Y.; Karimov, R. R.; Geraskin, I. M.; Nemykin, V. N.;
Zhdankin, V. V. J. Org. Chem. 2006, 71, 8452–8458.
(13) Gibert, M.; Ferrer, M.; Sanchez-Baeza, F.; Messeguer, A. Tetrahe-
dron 1997, 53, 8643–8650.
8446 J. Org. Chem. Vol. 74, No. 21, 2009

Mailyan et al.
JOCNote
stirred mixture of N-(2-iodophenyl)-N,4-dimethylbenzenesulfo-
namide (11) (0.19 g, 0.50 mmol) in 5 mL of dry CH2Cl2 at 0 °C.
The reaction mixture was stirred at room temperature over-
night, then the solvent was removed under vacuum. Crude
product was recrystallized from the mixture of ethyl ether/
dichloromethane (1:1). The resulting precipitate was filtered
and dried to afford 0.17 g (81%) of product 13 in the form of
dimethyldioxirane in dichloromethane (120 mL, approximately
12 mmol), using the same procedure as for compound 13,
afforded 0.38 g (89%) of product 14 in the form of a white
powder, mp 191-192 °C dec. 1H NMR (500 MHz, DMSO-d6) δ
8.11 (d, 1H), 7.81 (t, 1H), 7.79 (d, 4H), 7.51 (t, 1H), 7.45 (d, 4H),
6.73 (d, 1H), 2.45 (s, 6H); 13C NMR (500 MHz, DMSO-d6) δ
151.1, 147.0, 134.2, 133.6, 132.5, 132.3, 132.1, 130.4, 129.8,
128.4, 21.5. Anal. Calcd for C20H18INO6S2: C, 42.94; H, 3.24;
N, 2.50; S, 11.46; I, 22.69. Found: C, 42.74; H, 3.20; N, 2.39; S,
11.48; I, 22.54.
1
a white microcrystalline solid, mp 159-160 °C dec. H NMR
(500 MHz, CDCl3) δ 8.21 (d, 1H), 7.66 (t, 1H), 7.43 (t, 1H), 7.42
(d, 2H), 7.3 (d, 2H), 6.59 (d, 1H), 3.27 (s, 3H), 2.46 (s, 3H); 13
C
NMR (500 MHz, CDCl3) δ 151.2, 145.5, 140.3, 133.6, 131.5,
130.7, 130.0, 128.8, 126.9, 126.3, 39.4, 21.9.
2-Iodylphenyl 4-Methylbenzenesulfonate (17). The oxidation
of 2-iodophenyl 4-methylbenzenesulfonate (16) (0.35 g, 0.94
mmol) with a 0.1 M solution of dimethyldioxirane in dichlor-
omethane (100 mL, approximately 10 mmol), using the same
procedure as for compound 13, afforded 0.37 g (97%) of
product 17 as a white powder, mp 194-195 °C. 1H NMR (500
MHz, DMSO-d6) δ 7.91 (two overlapping d, 3H), 7.60 (t, 1H),
7.58 (t, 1H), 7.50 (d, 2H), 7.21 (d, 1H), 2.42 (s, 6H); 13C NMR
(500 MHz, DMSO-d6) δ 147.4, 147.3, 142.4, 134.3, 131.4, 131.1,
129.2, 128.6, 127.4, 122.1, 21.9. Anal. Calcd for C13H11IO5S: C,
38.44; H, 2.73; S, 7.89; I, 31.24. Found: C, 38.37; H, 2.68; S, 7.79;
I, 31.17.
Single crystals of product 13 suitable for X-ray crystallographic
analysiswere obtained by slow crystallizationfrom the ethyl ether/
dichloromethane solution. X-ray diffraction data were collected
on a Bruker APEX CCD diffractometer, using graphite-mono-
˚
chromated Mo KR radiation (λ=0.71073 A) at -100 °C. Absorp-
tion corrections were applied to the data by using the DIFABS
method. The structure was solved by the Patterson method
and refined by full-matrix least-squares refinement on F2,
using the Crystals for Windows program. Crystal data for 13:
C14H14INO4S, M = 419.24, monoclinic, space group C2/c,
˚
˚
˚
a = 25.253(3) A, b = 8.3071(11) A, c = 16.289(2) A, β =
3
˚
˚
117.351(2)°, V = 3035.1(7) A , Z = 8, μ(λ = 0.80000 A) =
3.154 mm-1, dcalc = 2.183 g/cm3, 10346 reflections measured,
10346 unique, R1 = 0.0205, wR2 = 0.0376 (I > 3σ(I)), R1 =
0.0433, wR2 = 0.0492 (alldata), GOF= 0.898. For further details
on crystal structures see the Crystallographic Information File
(deposited as Supporting Information).
Acknowledgment. This work was supported by a research
grant from the National Science Foundation (grant CHE-
0702734).
Supporting Information Available: Details of the experi-
mental procedures, spectroscopic data of the reaction products,
and X-ray data for compound 13 (CIF). This material is
available free of charge via the Internet at http://pubs.acs.org.
N-(2-Iodylphenyl)-4-methyl-N-tosylbenzenesulfonamide (14).
The oxidation of N-(2-iodophenyl)-4-methyl-N-tosylbenzene-
sulfonamide (12) (0.40 g, 0.76 mmol) with 0.1 M solution of
J. Org. Chem. Vol. 74, No. 21, 2009 8447