Preparation and X-ray structures of 3-[bis(trifluoroacetoxy)iodo]benzoic acid and 3-[hydroxy(tosyloxy)iodo]benzoic acid: New recyclable hypervalent iodine reagents

Article abstract of DOI:10.1021/jo702112s

(Chemical Equation Presented) Preparation, structural characterization, and reactivity of 3-[bis(trifluoroacetoxy)iodo]benzoic acid and 3-[hydroxy-(tosyloxy)iodo]benzoic acid, new recyclable iodine(III) reagents derived from 3-iodosylbenzoic acid, are described. The reduced form of these reagents, 3-iodobenzoic acid, can be easily recovered from the reaction mixtures using ion-exchange resin or basic aqueous workup followed by acidification with HCl.

Full text of DOI:10.1021/jo702112s

(diacetoxy)iodobenzene, [bis(trifluoroacetoxy)iodo]benzene and
[hydroxy(tosyloxy)iodo]benzene are based on the oxidized forms
of iodobenzene. The reactions of these reagents with organic
substrates lead to iodobenzene as the byproduct, which is
difficult to recover and reuse because of the high volatility and
solubility in organic solvents. Several research groups have tried
to improve the iodobenzene-based hypervalent iodine reagents
by developing their polymer-supported analogues, such as, poly-
(diacetoxyiodo)styrene, poly[bis(trifluoroacetoxy)iodo]styrene,
poly[hydroxy(tosyloxy)iodo]styrene), etc.2 Despite the utility of
the polymer-supported reagents, they still have several draw-
backs. These reagents require a multistep preparation, they have
lower reactivity compared to that of the corresponding mono-
meric analogues, and moreover, the repeated use of these
polymers leads to significant degradation due to the benzylic
oxidation of the polystyrene chain. The other previously reported
approaches to recyclable hypervalent iodide reagents involve
non-polymeric molecular species,3 which require multistep
syntheses or employ fluorous alkyl iodides and fluorous solvents
for separation of products.4
Preparation and X-ray Structures of
3-[Bis(trifluoroacetoxy)iodo]benzoic Acid and
3-[Hydroxy(tosyloxy)iodo]benzoic Acid: New
Recyclable Hypervalent Iodine Reagents
Mekhman S. Yusubov,*,† Tatyana V. Funk,†
Ki-Whan Chi,*,‡ Eun-Hye Cha,‡ Ghyung Hwa Kim,#
Andreas Kirschning,*,§ and Viktor V. Zhdankin*,∧
The Siberian State Medical UniVersity and The Tomsk
Polytechnic UniVersity, 2 MoskoVsky trakt, 634050 Tomsk,
Russia, UniVersity of Ulsan, 680-749 Ulsan, Republic of Korea,
Pohang Accelerator Laboratory, 790-784 Pohang, Republic of
Korea, Institut fu¨r Organische Chemie, Leibniz UniVersita¨t
HannoVer, Schneiderberg 1b, 30167 HannoVer, Germany, and
Department of Chemistry and Biochemistry, UniVersity of
Minnesota Duluth, Duluth, Minnesota, 55812
Vzhdanki@d.umn.edu
ReceiVed September 27, 2007
Recently, tagging strategies for reagents and catalysts have
widely been investigated that allow easy purification by means
of specific phase separation or scavenging.5 We have found that
3-iodosylbenzoic acid (which has a polymeric structure 2,6 see
Scheme 1) is an excellent oxygenating reagent whose reduced
form, 3-iodobenzoic acid 1, can be removed at the end of the
reaction by treatment with anionic-exchange resin or by addition
of NaHCO3 and can be easily recycled.7 Likewise, 3-(dichlor-
oiodo)benzoic acid is an excellent chlorinating reagent that can
be similarly recycled via 3-iodobenzoic acid.8 In contrast to the
previously reported protocols,2-4 hypervalent iodine reagents
derived from 3-iodobenzoic acid are inexpensive and readily
available compounds that can be easily recovered from the
reaction mixture.
Preparation, structural characterization, and reactivity of
3-[bis(trifluoroacetoxy)iodo]benzoic acid and 3-[hydroxy-
(tosyloxy)iodo]benzoic acid, new recyclable iodine(III)
reagents derived from 3-iodosylbenzoic acid, are described.
The reduced form of these reagents, 3-iodobenzoic acid, can
be easily recovered from the reaction mixtures using ion-
exchange resin or basic aqueous workup followed by
acidification with HCl.
(2) (a) Togo, H.; Sakuratani, K. Synlett 2002, 1966-1975. (b) Yamamoto,
Y.; Kawano, Y.; Toy, P. H.; Togo, H. Tetrahedron 2007, 63, 4680-4687.
(c) Tohma, H.; Takizawa, S.; Maegawa, T.; Kita, Y. Angew. Chem., Int.
Ed. 2000, 39, 1306-1308. (d) Tohma, H.; Morioka, H.; Takizawa, S.;
Arisawa, M.; Kita, Y. Tetrahedron 2001, 57, 345-352. (e) Tohma, H.;
Maegawa, T.; Kita, Y. Synlett 2003, 723-725. (f) Abe, S.; Sakuratani, K.;
Togo, H. J. Org. Chem. 2001, 66, 6174-6177. (g) Abe, S.; Sakuratani, K.;
Togo, H. Synlett 2001, 22-24. (h) Sakuratani, K.; Togo, H. ARKIVOC 2003,
Vi, 11-20. (i) Sakuratani, K.; Togo, H. Synthesis 2003, 21-23. (j) Ueno,
M.; Togo, H. Synthesis 2004, 2673-2677. (k) Tashino, Y.; Togo, H. Synlett
2004, 2010-2012. (l) Shang, Y.; But, T. Y. S.; Togo, H.; Toy, P. H. Synlett
2007, 67-70. (m) Jang, H.-S.; Chung, W.-J.; Lee, Y.-S. Tetrahedron Lett.
2007, 48, 3731-3734. (n) Ladziata, U.; Willging, J.; Zhdankin, V. V. Org.
Lett. 2006, 8, 167-170. (o) Ladziata, U.; Zhdankin, V. V. Synlett 2007,
527-537.
(3) (a) Tohma, H.; Maruyama, A.; Maeda, A.; Maegawa, T.; Dohi, T.;
Shiro, M.; Morita, T.; Kita, Y. Angew. Chem., Int. Ed. 2004, 43, 3595-
3598. (b) Moroda, A.; Togo, H. Tetrahedron 2006, 62, 12408-12414.
(4) Tesevic, V.; Gladysz, J. A. J. Org. Chem. 2006, 71, 7433-7440.
(5) For reviews on tagged reagents, see: (a) Barrett, A. G. M.; Hopkins,
B. T.; Ko¨bberling, J. Chem. ReV. 2002, 102, 3301. (b) Yoshida, J.-I.; Itami,
K. Chem. ReV. 2002, 102, 3693. (c) Bhattacharyya, S. Curr. Opin. Drug
DiscoVery DeV. 2004, 7, 752.
Hypervalent iodine reagents have emerged as reagents of
choice for various synthetically useful oxidative transforma-
tions.1 The most widely used reagents, such as, iodosylbenzene,
† The Siberian State Medical University.
‡ University of Ulsan.
# Pohang Accelerator Laboratory.
§ Leibniz Universita¨t Hannover.
∧ University of Minnesota Duluth.
(1) (a) Varvoglis, A. HyperValent Iodine in Organic Synthesis; Academic
Press: London, 1997. (b) Wirth, T., Ed. HyperValent Iodine Chemistry;
Springer-Verlag: Berlin, 2003. (c) Koser, G. F. Aldrichimica Acta 2001,
34, 89-102. (d) Koser, G. F. AdV. Heterocycl. Chem. 2004, 86, 225-292.
(e) Moriarty, R. M. J. Org. Chem. 2005, 70, 2893-2903. (f) Wirth, T.
Angew. Chem., Int. Ed. 2005, 44, 3656-3665. (g) Ladziata, U.; Zhdankin,
V. V. ARKIVOC 2006, ix, 26-58. (h) Zhdankin, V. V.; Stang, P. J. Chem.
ReV. 2002, 102, 2523-2584. (i) Richardson, R. D.; Wirth, T. Angew. Chem.,
Int. Ed. 2006, 45, 4402-4404. (j) Zhdankin, V. V. Science of Synthesis:
Houben-Weyl Methods of Molecular Transformations, Georg Thieme
Verlag: Stuttgart, Germany, 2007; Vol. 31a, Chapter 31.4.1, pp 161-234.
(6) Katritzky, A. R.; Savage, G. P.; Gallos, J. K.; Durst, H. D. J. Chem.
Soc., Perkin Trans. 2 1990, 1515-1518.
(7) (a) Yusubov, M. S.; Gilmkhanova, M. P.; Zhdankin, V. V.;
Kirschning, A. Synlett 2007, 563-566. (b) Kirschning, A.; Yusubov, M.
S.; Yusubova, R. Y.; Chi, K.-W.; Park, J. Y. Beilstein J. Org. Chem. 2007,
3, 19.
(8) Yusubov, M. S.; Drygunova, L. A.; Zhdankin, V. V. Synthesis 2004,
2289-2292.
10.1021/jo702112s CCC: $40.75 © 2008 American Chemical Society
Published on Web 12/07/2007
J. Org. Chem. 2008, 73, 295-297
295

SCHEME 1. Preparation of 3-Iodosylbenzoic Acid 2 and Its
Derivatives 3 and 4
We report the preparation and X-ray crystal structure of two
new recyclable non-polymeric hypervalent iodine reagents
derived from 3-iodobenzoic acid, namely, 3-[bis(trifluoroac-
etoxy)iodo]benzoic acid, 3, and 3-[hydroxy(tosyloxy)iodo]-
benzoic acid, 4. Compounds 3 and 4 were conveniently prepared
in high yield by treatment of 3-iodosylbenzoic acid, 2,7 with
trifluoroacetic acid or p-toluenesulfonic acid, respectively
(Scheme 1).
FIGURE 1. Perspective view of one of five crystallographically
independent molecules 3-[bis(trifluoroacetoxy)iodo]benzoic acid, 3, with
50% ellipsoid. Selected distances [Å] and angles [deg]: I(1)-C(1)
2.083, I(1)-O(3) 2.149, I(1)-O(6) 2.186, I(1)‚‚‚O(5) 3.146, I(1)‚‚‚
O(4) 3.030; C(1)-I(1)-O(3) 83.26, O(3)-I(1)-O(6) 163.85.
Products 3 and 4 were isolated as white, stable, microcrys-
talline compounds and were analyzed by NMR spectroscopy,
elemental analysis, and X-ray crystallography. Molecular struc-
tures of 3 and 4 are presented in Figures 1 and 2.
It is interesting to note that the presence of a meta carboxylic
group does not have any noticeable effect on the molecular
geometries of products 3 and 4 which, in general, are similar
to the previously reported X-ray crystal structures of [bis-
(trifluoroacetoxy)iodo]benzene9 and [hydroxy(tosyloxy)iodo]-
benzene.10 Both structures 3 and 4 have a distorted T-shaped
geometry at the iodine(III) center. In the molecule of trifluo-
roacetate 3 intramolecular I‚‚‚O interactions with the carboxylate
oxygens O(4) and O(5) are observed with distances I(1)‚‚‚O(5)
3.146 Å and I(1)‚‚‚O(4) 3.030 Å. In addition to the five
intramolecular interactions, an intermolecular coordination of
an iodine atom to one of the carboxylic oxygens of the
neighboring molecule was also found with a distance of 3.023
Å. The overall geometry of the iodine coordination sphere in 3
could be represented as a distorted octahedron, similar to the
structure of [bis(trifluoroacetoxy)iodo]benzene.9
The I-OTs bond distance in tosylate 4, (2.437 Å), is
significantly longer than the I-OH bond distance of 1.954 Å,
which is indicative of some ionic character of this compound.
Bond distances and angles at the iodine(III) center in 4 are very
close to the respective structural parameters previously reported
for [hydroxy(tosyloxy)iodo]benzene.10 In addition to the three
intramolecular bonds, a weaker intermolecular coordination of
iodine atom to one of the sulfonyl oxygens of the neighboring
molecule is found with a distance of 2.931 Å. No intermolecular
interaction involving meta carboxylic group can be found in
both molecules 3 and 4, which is in sharp contrast with the
polymeric structure of 3-iodobenzoic acid 2.6 The monomeric
character of 3 and 4 leads to the improved solubility and higher
reactivity compared those of to 3-iodobenzoic acid 2.
FIGURE 2. X-ray crystal structure of 3-[hydroxy(tosyloxy)iodo]-
benzoic acid, 4, with 50% ellipsoid. Selected distances [Å] and angles
[deg]: I(1)-C(7) 2.105, I(1)-O(3) 1.954, I(1)-O(5) 2.437; O(3)-
I(1)-C(7) 92.21, O(3)-I(1)-O(5) 172.02.
benzene and [hydroxy(tosyloxy)iodo]benzene, both of which
belong to the most important and widely used representatives
of hypervalent iodine reagents.1 The oxidative properties of
reagents 3 and 4 were evaluated in the most typical reactions
previously reported for PhI(OCOCF3)2 and PhI(OH)OTs, such
as oxidation of sulfides,3a,11 oxidative iodination of arenes,12
R-tosyloxylation of ketones,2g,3a,13 and Hofmann-type rearrange-
ment3a,14 (Scheme 2). The products of these reactions (Scheme
2) were conveniently separated from the byproduct, 3-iodoben-
zoic acid 1, by simple treatment with ion-exchange resin IRA-
900. 3-Iodobenzoic acid 1 can easily be regenerated from IRA
As expected from the structural similarity, the reactivity
pattern of 3 and 4 is similar to [bis(trifluoroacetoxy)iodo]-
(11) Barbas, D.; Spyroudis, S.; Varvoglis, A. J. Chem. Res. (S) 1985,
186-187.
(12) Muraki, T.; Togo, H.; Yokoyama, M. J. Org. Chem. 1999, 64,
2883-2889.
(9) Alcock, N. W.; Harrison, W. D.; Howes, C. J. Chem. Soc., Dalton
Trans. 1984, 1709-1716.
(10) Koser, G. F.; Wettach, R. H.; Troup, J. M.; Frenz, B. A. J. Org.
Chem. 1976, 41, 3609-3611.
(13) Koser, G. F.; Relenyi, A. G.; Kalos, A. N.; Rebrovic, L.; Wettach,
R. H. J. Org. Chem. 1982, 47, 2487-2489.
(14) Lazbin, I. M.; Koser, G. F. J. Org. Chem. 1986, 51, 2669-2671.
296 J. Org. Chem., Vol. 73, No. 1, 2008

SCHEME 2. Representative Reactions of Reagents 3 and 4
3-[Hydroxy(tosyloxy)iodo]benzoic Acid (4). A mixture of
3-iodosylbenzoic acid 1 (0.264 g, 1 mmol) and p-TsOH‚H2O
(0.38 g, 2 mmol) in acetonitrile (2 mL) was stirred at room
temperature for 1 h. The resulting precipitate was filtered,
washed with cold dichloromethane (2 mL), and dried to afford
0.362 g (83%) of product 4 in the form of white crystals, mp
132-134 °C (with decomposition). IR (KBr): 3240, 1687, 1235,
1
1100 cm-1. H NMR (DMSO-d6): δ 8.69 (s), 8.42 (d, J ) 8
Hz, 1H), 8.19 (d, J ) 8 Hz, 1H), 7.45 (t, J ) 8 Hz, 1H), 7.46
(d, J ) 8 Hz, 2H), 7.11 (d, J ) 8 Hz, 2H), 2.28 (s, 3H). 13C
NMR (DMSO-d6): δ 165.7, 145.6, 138.1, 137.7, 134.6, 133.2,
132.7, 131.4, 128.1, 122.5, 123.3, 20.8. Anal. Calcd for C14H13-
IO6S: C, 38.55; H, 3.00. Found: C, 38.92; H, 2.87.
X-ray Crystal Structure Determination of 3 and 4. The
diffraction data were collected with synchrotron radiation (λ )
0.80000 Å) at the Wiggler Beamline 4A, Pohang Accelerator
Laboratory. Data reduction and adsorption correction were
performed with HKL2000 package. The structures were solved
by direct methods and refined by full-matrix least-squares
method with SHELXTL package. All the non-hydrogen atoms
were refined anisotropically, and hydrogen atoms were added
to their geometrically ideal positions. Crystal data for 3:
C11H4O6F6I, M ) 473.04, triclinic, space group P1h (No. 2), a
) 14.302(3) Å, b ) 15.142(3) Å, c ) 17.101(3) Å, R ) 97.53-
(3)°, â ) 101.25(3)°, γ ) 90.66(3)°, V ) 3598.3(12) Å3, Z )
10, T ) 90 K, µ(λ ) 0.80000 Å) ) 3.154 mm-1, dcalc ) 2.183
g/cm3, 10346 reflections measured, 10346 unique, R1 ) 0.0755,
wR2 ) 0.2513 (I > 2σ(I)), R1 ) 0.1099, wR2 ) 0.2837 (all
data), GOF ) 0.753. Crystal data for 4: C14H13O6SI, M )
436.20, monoclinic, space group P21/c (No. 14), a ) 17.534-
(3) Å, b ) 12.134(2) Å, c ) 7.166(1) Å, â ) 99.15(3)°, V )
1505.2(5) Å3, Z ) 4, T ) 90 K, µ(λ ) 0.80000 Å) ) 3.114
mm-1, dcalc ) 1.925 g/cm3 5316 reflections measured, 3089
unique (Rint ) 0.0698), R1 ) 0.0476, wR2 ) 0.1327 (I > 2σ(I)),
R1 ) 0.0479, wR2 ) 0.1332 (all data), GOF ) 1.015. For
further details on crystal structures see the Crystallographic
Information File (deposited as Supporting Information).
900 resin by treatment with aqueous HCl and can be reoxidized
to reagent 2 without additional purification.7 An alternative
procedure for product separation involves basic aqueous workup
followed by acidification with HCl.8
In conclusion, we have reported the preparation, X-ray
structural characterization, and useful reactivity of 3-[bis-
(trifluoroacetoxy)iodo]benzoic acid, 3, and 3-[hydroxy(tosy-
loxy)iodo]benzoic acid, 4, new recyclable iodine(III) reagents
derived from 3-iodosylbenzoic acid.
Experimental Section
Additional experimental details can be found in the Support-
ing Information.
3-[Bis(trifluoroacetoxy)iodo]benzoic Acid (3). A mixture
of 3-iodosylbenzoic acid 1 (0.264 g, 1 mmol) and trifluoroacetic
acid (2 mL) was refluxed for 1 h. After cooling to room
temperature, the resulting solution was concentrated in vacuum
to the volume of about 1 mL, and then dichloromethane (2 mL)
was added to this solution. The resulting mixture was heated to
boiling point and then cooled to 0 °C; the precipitate was
filtered, washed with cold dichloromethane, and dried to afford
0.436 g (92%) of product 3 in the form of white crystals, mp
Acknowledgment. M.S.Y. and A.K. thank Fonds der
Chemischen Industrie for support of this work. 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 Brain Korea 21 program in Korea. We thank Pohang
Accelerator Laboratory and Mr. Hyunuk Kim in POSTECH for
their help in the X-ray analysis.
1
125-127 °C (with decomposition). H NMR (CDCl3-CF3-
CO2H, 2:3): δ 9.05 (s), 8.57 (d, J ) 8 Hz, 1H), 8.54 (d, J )
8 Hz, 1H), 7.84 (t, J ) 8 Hz, 1H). 13C NMR (CDCl3-CF3-
CO2H, 2:3): δ 170.6, 163.0 (q, overlapping with signal from
CF3CO2H), 141.1, 137.7, 136.1, 133.0, 132.9, 122.8, 115.0 (q,
overlapping with signal from CF3CO2H). Anal. Calcd for
C11H5F6IO6: C, 27.87; H, 1.06. Found: C, 27.95; H, 0.97.
Supporting Information Available: Details of the experimental
procedures, spectroscopic data of the reaction products, and X-ray
data for the compounds 3 and 4 (CIF). This material is available
free of charge via the Internet at http://pubs.acs.org.
JO702112S
J. Org. Chem, Vol. 73, No. 1, 2008 297