RuCl3-catalyzed oxidation of iodoarenes with peracetic acid: New facile preparation of iodylarenes

Article abstract of DOI:10.1021/jo062073s

New facile methodology for the preparation of pentavalent iodine compounds using peracetic acid as an oxidant in the presence of catalytic amounts of ruthenium trichloride is described. The new procedure allows the preparation of several previously unknown iodylarenes bearing strongly electron-withdrawing CF₃ groups in the aromatic ring.

Full text of DOI:10.1021/jo062073s

SCHEME 1. RuCl3-Catalyzed Preparation of Iodylarenes
RuCl3-Catalyzed Oxidation of Iodoarenes with
Peracetic Acid: New Facile Preparation of
Iodylarenes
Alexey Y. Koposov,† Rashad R. Karimov,†
Andrey A. Pronin,† Tatyana Skrupskaya,†
Mekhman S. Yusubov,‡ and Viktor V. Zhdankin*,†
Department of Chemistry and Biochemistry, UniVersity of
Minnesota Duluth, Duluth, Minnesota, 55812, and The Siberian
State Medical UniVersity, Tomsk, Russia
a facile and convenient method for the preparation of iodylarenes
by ruthenium-catalyzed oxidation of aryl iodides under mild
conditions.
Vzhdanki@d.umn.edu
In the course of our recent studies on the RuCl3-catalyzed
oxidation of alcohols with (diacetoxyiodo)benzene, we have also
discovered that this reaction proceeds via an initial instantaneous
Ru-catalyzed disproportionation of PhI(OAc)2 to iodobenzene
and iodylbenzene with the latter acting as the actual stoichio-
metric oxidant toward alcohols.4 A similar example of the
ruthenium-catalyzed disproportionation of PhIO yielding PhIO2
and PhI was previously described in the literature.5 Based on
these observations, we have developed a RuCl3-catalyzed direct
one-pot conversion of ArI to ArIO2 using peracetic acid as a
stoichiometric oxidant (Scheme 1). This mild and convenient
procedure combines in one-pot the known peracetic oxidation
ReceiVed October 6, 2006
6
of ArI to ArI(OAc)2 and the immediate disproportionation of
the iodine(III) species in the presence of RuCl3 leading to ArIO2
as the final product.
New facile methodology for the preparation of pentavalent
iodine compounds using peracetic acid as an oxidant in the
presence of catalytic amounts of ruthenium trichloride is
described. The new procedure allows the preparation of
several previously unknown iodylarenes bearing strongly
electron-withdrawing CF3 groups in the aromatic ring.
This procedure (Scheme 1) requires much milder conditions
(gentle warming to 40 °C) compared to the known noncatalytic
oxidation of PhI to PhIO2 with peracetic acid at 100 °C.3e
Because of the milder conditions, the procedure is compatible
with the presence of the electron-donating alkyl and alkoxy
groups in the aromatic ring and can be applied for the
preparation of methyl-, isopropyl-, and methoxy-substituted
iodylarenes (Table 1, entries 2, 3, 5, 6). At the same time, this
method allows the preparation of iodylarenes from iodoarenes
bearing electron-withdrawing substituents, such as halogen
atoms and CF3 groups, in the aromatic ring (Table 1, entries
Iodylarenes, ArIO2, have attracted a significant current interest
as mild and highly selective reagents for the oxidation of
alcohols to carbonyl compounds as well as for a variety of other
synthetically useful oxidative transformations.1 The best known
representative of this class of compounds is 2-iodoxybenzoic
acid, IBX (which exists in the benziodoxole tautomeric form);
however, a variety of other iodylarenes, including the parent
iodylbenzene,2a have found some synthetic application. During
the last several years the preparation and synthetic utilization
of numerous new iodylarenes have been reported.2b-j A typical
procedure for the preparation of iodylarenes involves the
oxidation of an iodoarene with a strong oxidizing reagent.1a,f,g
Several experimental methods for the preparation of iodylben-
zene have been reported in the literature including the dispro-
portionation of iodosobenzene,3a or oxidations of iodobenzene
with potassium peroxysulfate in concentrated sulfuric acid,3b
sodium periodate,3c,d peracetic acid at 100 °C,3e and some other
powerful and generally unsafe oxidizing systems. We now report
(2) (a) Tohma, H.; Takizawa, S.; Watanabe, H.; Fukuoka, Y.; Maegawa,
T.; Kita, Y. J. Org. Chem. 1999, 64, 3519-3523. (b) Macikenas, D.;
Skrzypczak-Jankun, E.; Protasiewicz, J. D. Angew. Chem., Int. Ed. 2000,
39, 2007. (c) Meprathu, B. V.; Justik, M. W.; Protasiewicz, J. D.
Tetrahedron Lett. 2005, 46, 5187. (d) 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. (e) 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. (f) Zhdankin,
V. V.; Goncharenko, R. N.; Litvinov, D. N.; Koposov, A. Y. ARKIVOC
[Online] 2005, iV, 8-18. (g) Ladziata, U.; Koposov, A. Y.; Lo, K. Y.;
Willging, J.; Nemykin, V. N.; Zhdankin, V. V. Angew. Chem., Int. Ed.
2005, 44, 7127-7131. (h) Ladziata, U.; Willging, J.; Zhdankin, V. V. Org.
Lett. 2006, 8, 167-170. (i) Chung, W.-J.; Kim, D.-K.; Lee, Y.-S.
Tetrahedron Lett. 2003, 44, 9251-9254. (j) Kim, D.-K.; Chung, W.-J.; Lee,
Y.-S. Synlett 2005, 279-282.
(3) (a) Lucas, H. J.; Kennedy, E. R. Org. Synth. 1942, 22, 72-73. (b)
Kennedy, R. J.; Stock, A. M. J. Org. Chem. 1960, 25, 1901-1906. (c)
Kazmierczak, P.; Skulski, L.; Kraszkiewicz, L. Molecules 2001, 6, 881-
891. (d) Kraszkiewicz, L.; Skulski, L. ARKIVOC [Online] 2003, Vi, 120-
125. (e) Sharefkin, J. G.; Saltzman, H. Org. Synth. 1963, 43, 65-67.
(4) Yusubov, M. S.; Chi, K.-W.; Park, J. Y.; Karimov, R.; Zhdankin,
V. V. Tetrahedron Lett. 2006, 47, 6305-6308.
(5) Bressan, M.; Morvillo, A. Inorg. Chem. 1989, 28, 950.
(6) Sharefkin, J. G.; Saltzman, H. Org. Synth. 1973, CollectiVe Vol. V,
660-663.
† University of Minnesota Duluth.
‡ The Siberian State Medical University.
(1) (a) Varvoglis, A. HyperValent Iodine in Organic Synthesis; Academic
Press: London, 1997. (b) Koser, G. F. AdV. Heterocycl. Chem. 2004, 86,
225-292. (c) Moriarty, R. M. J. Org. Chem. 2005, 70, 2893-2903. (d)
Tohma, H.; Kita, Y. AdV. Synth. Catal. 2004, 346, 111-124. (e) Zhdankin,
V. V.; Stang, P. J. Chem. ReV. 2002, 102, 2523-2584. (f) Ladziata, U.;
Zhdankin, V. V. ARKIVOC [Online] 2006, ix, 26-58. (g) Zhdankin, V. V.
Curr. Org. Synth. 2005, 2, 121-145. (h) Wirth, T. Angew. Chem., Int. Ed.
2005, 44, 3656-3665. (i) Richardson, R. D.; Wirth, T. Angew. Chem., Int.
Ed. 2006, 45, 4402-4404.
10.1021/jo062073s CCC: $33.50 © 2006 American Chemical Society
Published on Web 11/29/2006
9912
J. Org. Chem. 2006, 71, 9912-9914

TABLE 1. Oxidation of Aryl Iodides with Peracetic Acid in the Presence of Ruthenium Trichloride
a Isolated yields of analytically pure products. b All previously reported ArIO2 were identified by comparison of their IR and NMR spectra with literature
data (refs 3c,d); for analytical and spectroscopic characterization of new products (entries 6, 12, 13) see the Supporting Information. c Decomposition with
formation of black tar was observed. d Significant decomposition occurred; yield determined by NMR. e Unreacted starting material (about 50%) was present
in the reaction mixture. f 2-Iodosylbenzoic acid (1-hydroxy-(1H)-benzo-1,2-iodoxol-3-one) was isolated.
7-13). The most impressive result was the facile preparation
of the previously unknown 1-iodyl-4-trifluoromethylbenzene
(entry 12) and 1-iodyl-3,5-bis(trifluoromethyl)benzene (entry 13)
in excellent yields.
(IBX) from 2-iodobenzoic acid (entry 15) and its ester (entry16)
resulted in the formation of 2-iodosylbenzoic acid (IBA), which
indicates that only noncyclic iodine(III) intermediates can
disproportionate in the presence of RuCl3.
The procedure in general is limited to the nonsterically
hindered substrates. The attempted preparation of the unknown
1-iodyl-2,4,6-trimethylbenzene by the oxidation of 1-iodo-2,4,6-
trimethylbenzene (entry 4, Table 1) resulted in complete
decomposition with the formation of a black tar, probably, due
to the low stability of the target iodylarene. At the same time,
the preparation of the sterically hindered, previously unknown
1-iodyl-2-isopropylbenzene was successful (entry 6). It should
be noted, however, that the oxidation of 1-iodo-2-isopropyl-
benzene was slow and a substantial amount of unreacted iodide
was present in the reaction mixture even after 16 h.
The oxidation of 2-iodobenzoic acid (entry 15), and its
derivatives (entries 14 and 16) has also failed to afford the
desired iodine(V) derivatives. In the case of the 2-iodobenzamide
derivative, a complete decomposition was observed, most likely
because of the instability of the amido group under reaction
conditions. The attempted preparation of 2-iodoxybenzoic acid
The mechanism of the Ru-catalyzed disproportionation of
iodine(III) compounds has been previously discussed in the
literature. It is assumed, in particular, that the intermediate oxo
ruthenium complexes are responsible for the oxygen transfer
steps in the mechanism of disproportionation of iodine(III)
species.4,5 It is unlikely that RuCl3 has any catalytic effect on
the initial oxidation of ArI to ArI(OAc)2. The uncatalyzed
oxidation of iodoarenes with peracetic acid occurs at 30-40
°C in about 1 h, which is comparable with the conditions of
the catalytic reaction (Scheme 1).
In conclusion, we reported the new facile methodology for
the preparation of iodylarenes using peracetic acid as an oxidant
in the presence of catalytic amounts of ruthenium trichloride.
This new procedure allows the preparation of several previously
unknown iodylarenes bearing strongly electron-withdrawing CF3
groups in the aromatic ring, as well as the preparation of the
sterically hindered 1-iodyl-2-isopropylbenzene.
J. Org. Chem, Vol. 71, No. 26, 2006 9913

spatula, or heating, and therefore should be handled with ap-
propriate precautions.
Experimental Section
General Procedure for Preparation of Iodylarenes. Iodoarene
(5 mmol) was added at 40 °C to a freshly prepared solution of
peracetic acid in acetic acid (prepared by stirring a mixture of acetic
anhydride (16 mL) and 35% H2O2 (4 mL) at 40 °C for 4 h), and
the resulting mixture was stirred at 40 °C for 1 h. Then the solution
of RuCl3 in water (10 µL, 0.04 mmol/mL) was added, and the
reaction was stirred at the same temperature for 16 h. Diethyl ether
(80 mL) was added to the mixture after cooling to room temper-
ature; the resulting white, microcrystalline precipitate of ArIO2 was
collected by filtration, washed with Et2O, and dried in vacuum.
Additional purification can be performed by crystallization from
boiling water. Caution: Dry iodylarenes are potentially hazardous
compounds, which may explode upon impact, scratching with a
Acknowledgment. This work was supported by a Research
Grant from the National Science Foundation.
Supporting Information Available: The general procedure of
the oxidation of iodoarenes, full characterization data for new
iodylarenes (1-iodyl-2-isopropylbenzene, 1-iodyl-4-trifluorometh-
ylbenzene, and 1-iodyl-3,5-bis(trifluoromethyl)benzene), NMR
spectra of all products. This material is available free of charge
via the Internet at http://pubs.acs.org.
JO062073S
9914 J. Org. Chem., Vol. 71, No. 26, 2006