LETTER
m-Iodosylbenzoic Acid as a Convenient Recyclable Reagent
565
(3) Adam, W.; Gelalcha, F. G.; Saha-Moeller, C. R.; Stegmann,
V. R. J. Org. Chem. 2000, 65, 1915.
Method B is particularly useful for the oxidation of acid-
sensitive substrates. Product yields and reaction times for
the oxidation of a series of primary alcohols are shown in
Figure 1.
(4) Mueller, P.; Godoy, J. Tetrahedron Lett. 1981, 22, 2361.
(5) Yusubov, M. S.; Chi, K.-W.; Park, J. Y.; Karimov, R.;
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D.; Kitamura, T. Synthesis 2006, 1253. (f) Mülbaier, M.;
Giannis, A. Angew. Chem. Int. Ed. 2001, 40, 4393; Angew.
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Chem. 2001, 113, 4532. (h) Lei, Z.; Denecker, C.;
In method A, the reaction is terminated by addition of IRA
900 (hydroxide form) which traps the reduction product
m-iodobenzoic acid (1) by ion exchange (as polymer 3).
Also any remaining oxidant 2 is removed in this way. m-
Iodobenzoic acid (1) can be easily regenerated (> 95%)
from polymer 3 in pure form by treatment with aqueous
HCl. When the oxidation is performed in the presence of
NaHCO3 (method B), the carbonyl compound is conve-
niently extracted from the reaction mixture with diethyl
ether, while the sodium salt of m-iodobenzoic acid re-
mains in the aqueous solution and can be easily recycled
and reused.
Jegasothy, S.; Sherrington, D. C.; Slater, N. K. H.;
Also secondary alcohols can be oxidized furnishing the
corresponding ketones (Figure 2). Method B gave better
results in the oxidation of the acid-sensitive protected
sugar derivative (product 4r),14 while in the oxidation of
borneol, method A afforded a much higher yield of the re-
spective product 4p.
Sutherland, A. J. Tetrahedron Lett. 2003, 44, 1635.
(i) Chung, W.-J.; Kim, D.-K.; Lee, Y.-S. Tetrahedron Lett.
2003, 44, 9251. (j) Ladziata, U.; Willging, J.; Zhdankin, V.
V. Org. Lett. 2006, 7, 167. (k) Tohma, H.; Maruyama, A.;
Maeda, A.; Maegawa, T.; Dohi, T.; Shiro, M.; Morita, T.;
Kita, Y. Angew. Chem. Int. Ed. 2004, 43, 3595; Angew.
Chem. 2004, 116, 3679. (l) Dohi, T.; Maruyama, A.;
Yoshimura, M.; Morimoto, K.; Tohma, H.; Shiro, M.; Kita,
Y. Chem. Commun. 2005, 2205.
It can be assumed that m-HO2CPhIO2 and aryl iodide 1 are
initially formed as a result of the Ru-catalyzed dispropor-
tionation of reagent 2, and m-iodylbenzoic acid serves as
the actual oxidizer in the oxidation of alcohols.5 In practi-
cal use, however, the readily available and stable iodosyl
compound 2 is a more convenient oxidizer compared to
the explosive iodylarene.
(8) Tesevic, V.; Gladysz, J. A. J. Org. Chem. 2006, 71, 7433.
(9) Kirschning, A.; Wittenberg, R.; Monenschein, H. Angew.
Chem. Int. Ed. 2001, 40, 650; Angew. Chem. 2001, 113, 670.
(10) (a) Wilgerodt, C. Chem. Ber. 1894, 27, 2326. (b) Katritzky,
A. R.; Savage, G. P.; Gallos, J. K.; Durst, H. D. J. Chem.
Soc., Perkin Trans. 2 1990, 1515. (c) Caraway, W. T.;
Hellerman, L. J. Am. Chem. Soc. 1953, 75, 5334.
In conclusion, we have disclosed that the rarely employed
m-iodosylbenzoic acid is an ideally tagged iodine(III)
reagent which in our view allows the easiest purification
protocol for aryliodine reagents known so far. This tag-
ging concept was utilized in the RuCl3-catalyzed oxida-
tion of alcohols but should also be applicable for most
iodine(III)-mediated reactions.
(11) Improved Procedure for the Preparation of m-Iodosyl-
benzoic Acid (2): m-Iodobenzoic acid (1; 2.48 g, 10 mmol)
was added at 40 °C to a freshly prepared solution of peracetic
acid in AcOH [prepared by stirring a mixture of Ac2O (60
mL) and 35% H2O2 (14 mL) at 40 °C for 4 h in dark] and the
resulting mixture was stirred for 12 h at ambient temperature
in dark. A spontaneous heating of the reaction mixture up to
45 °C and complete dissolution of m-iodobenzoic acid was
observed during the first two hours of stirring. The reaction
mixture was poured onto ice-water (150 mL), and allowed to
crystallize. The precipitate was filtered on a Büchner funnel
and washed with ice-water (200 mL). The solid was then
dried, first by maintaining suction and then in vacuum, to
afford product 2 as a light yellow powder. Yield: 1.90–
2.11 g (72–80% yield); mp 168–169 °C. 1H NMR (200 MHz,
CD3COOD): d = 7.71 (t, 1 H), 8.35 (d, 1 H), 8.48 (d, 1 H),
8.89 (s, 1 H). Anal. Calcd for C7H5IO3 (263.93): C, 31.84;
H, 1.91. Found: C, 31.77; H, 1.84.
Acknowledgment
M.S.Y. thanks the Minister of Education of Russia and Deutsche
Akademische Austauschdienst (DAAD) for a scholarship and
RFBR (Grant 07-03-00239a). Additionally, the work was funded by
the Fonds der Chemischen Industrie. V.V.Z. thanks National
Science Foundation (USA) for support.
References and Notes
(12) RuCl3-Catalyzed Oxidation of Alcohols to Carbonyl
Compounds:
(1) (a) Hypervalent Iodine Chemistry; Wirth, T., Ed.; Springer:
Berlin, 2003. (b) Varvoglis, A. Hypervalent Iodine in
Organic Synthesis; Academic Press: London, 1997.
(c) Tohma, H.; Kita, Y. Adv. Synth. Catal. 2004, 346, 111.
(d) Wirth, T. Angew. Chem. Int. Ed. 2005, 44, 3656.
(e) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2002, 102,
2523. (f) Zhdankin, V. V. Curr. Org. Synth. 2005, 2, 121.
(2) (a) Kalberer, E. W.; Whitfield, S. R.; Sanford, M. S. J. Mol.
Catal. A: Chem. 2006, 251, 108. (b) Dick, A. R.; Hull, K.
L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300.
(c) Desai, L. V.; Hull, K. L.; Sanford, M. S. J. Am. Chem.
Soc. 2004, 126, 9542. (d) Kalyani, D.; Sanford, M. S. Org.
Lett. 2005, 7, 4149.
Method A: To a mixture of alcohol (0.05–0.20 mmol) and
m-iodosylbenzoic acid (2; 0.075–0.300 mmol, 1.5 equiv) in
aq MeCN (MeCN–H2O, 5:1; 0.5–2 mL) an aqueous solution
of RuCl3 (1.0–4.0 mL of 0.25 M solution; 0.25–1.0 mmol)
was added under stirring at r.t. An instantaneous formation
of a cotton-like, off-white precipitate was observed. The
reaction mixture was stirred for a period of time indicated in
Figures 1 and 2 (the reactions were monitored by TLC).
Then, CH2Cl2 (1.5 mL) and IRA 900 (hydroxide form; 160–
620 mg) were added and the mixture was stirred for 5 min.
The polymer was removed by filtration and the solution was
Synlett 2007, No. 4, 563–566 © Thieme Stuttgart · New York