Hydrogen Peroxide-Tungstic Acid


[7722-84-1]  · H2O2  · Hydrogen Peroxide-Tungstic Acid  · (MW 34.02) (H2WO4)

[7783-03-1]  · H2O4W  · Hydrogen Peroxide-Tungstic Acid  · (MW 249.87)

(oxidation of alkenes,1 alkynes,15 and other organic substrates18 -22)

Physical Data: H2WO4: d 5.500 g cm-3.

Solubility: H2WO4: insol cold H2O; slightly sol hot H2O.

Form Supplied in: H2WO4: yellow powder; widely available.

Handling, Storage, and Precautions: see Hydrogen Peroxide. All operations involving peroxides should be conducted behind a safety shield in a fume cupboard. It is also advisable, prior to work-up, to analyze the reaction mixture for peroxy compounds. These should be destroyed or removed before evaporation of the solvent.

Epoxidation of Alkenes.

Tungstic acid catalyzes the oxidation by hydrogen peroxide of alkenes to the corresponding epoxides.1 As tungstic acid is a fairly strong acid, the reaction mixture requires buffering to prevent subsequent diol formation. Typical conditions are: tungstic acid 1 mol %, sodium acetate 2-3 mol % (pH 4.5), 35% hydrogen peroxide 1.5 mol % at rt.2 Under these conditions the epoxidation occurs with complete retention of configuration for both cis- and trans-alkenes (eq 1). Reactivity increases with nucleophilicity of the double bond. Coordination to the catalyst by hydroxy groups in the substrate also enhances the rate of epoxidation, with allylic alcohols reacting faster than homoallylic alcohols,3 and isolated alkenes being least reactive (eq 2). Dienols can be selectively epoxidized at the allylic position (eq 3).4 Conjugated unsaturated acids and even diacids are epoxidized using sodium tungstate and hydrogen peroxide in water at 60-65 °C, with the pH controlled to within 5.8-6.8.5 The use of pertungstate, W2O112-, generated from tungstic acid and benzyltriphenylphosphonium chloride, Ph3PCH2Ph+ Cl-, allows unbuffered conditions to be employed (eq 4).6 The catalyst can be prepared in situ or preformed and stored for a long time. Other epoxidation methods include: sodium tungstate in a two-phase system of phosphate buffer/dichloromethane,7 and a complex of tungstic acid and tributyltin chloride supported on charcoal.8 See also m-Chloroperbenzoic Acid and Vanadyl Bis(acetylacetonate).

Diol Formation.

The oxidation of cyclooctadiene to the trans-diol has been effected using 30% hydrogen peroxide and a catalytic quantity of tungstic acid in t-butanol at 31 °C (eq 5);9 however, similar conditions have also been used for the cleavage of cyclopentene to glutaraldehyde (eq 6).10 More concentrated solutions of hydrogen peroxide have also been employed.11 The use of 90% hydrogen peroxide in 2-propanol has been reported to yield cyclohexane-1,2-diol from cyclohexene. When methanol or ethanol are used as solvents the corresponding glycol monoethers are formed.12 See also: Potassium Permanganate and Osmium Tetroxide.

Carboxylic Acids.

Under the more forcing conditions of refluxing t-butanol, epoxidation followed by diol formation and oxidative alkene cleavage occurs. Using these conditions, cyclopentene gives glutaric acid (eq 7)13 and 1-methyl-1-cyclohexene gives 2-oxoheptanoic acid (eq 8). Cyclohexanone has been oxidized to adipic acid in low yield.14 See also: Sodium Periodate.

a-Hydroxy Ketones.

Treatment of 12-tungstophospholic acid with hydrogen peroxide and cetylpyridinium chloride in water gives peroxotungstophosphate, an efficient catalyst for the oxidation of internal alkynes to the corresponding a,b-epoxy ketone (eq 9).15 The same catalyst will also oxidize vic-diols into a-hydroxy ketones (eq 10).16 See also: Iodosylbenzene.


Reaction of acetals with hydrogen peroxide and tungstic acid in acetonitrile at low temperature gives the corresponding gem-dihydroperoxides (eq 11).17

Other Oxidations.

Tungstic acid has been used to catalyze the oxidation by hydrogen peroxide of sulfides to the corresponding sulfones.18 Various amines have also been oxidized to the corresponding oximes,19 nitrones,20 hydroxamic acids,21 and nitroso compounds.22

1. (a) Kanerva, L. T.; Vanttinen E. TA 1993, 4, 85. (b) Itakura, J.; Tanaka, H.; Ito, H. BCJ 1969, 42, 1604.
2. Prat, D.; Lett, R. TL 1986, 27, 707.
3. Prat, D.; Delpech, B.; Lett, R. TL 1986, 27, 711.
4. Wershofen, S.; Scharf, H.-D. S 1988, 854.
5. (a) Kirshenbaum, K. S.; Sharpless, K. B. JOC 1985, 50, 1979. (b) Payne, G. B.; Williams, P. H. JOC 1959, 24, 54.
6. Prandi, J.; Kagan, H. B.; Mimoun, H. TL 1986, 27, 2617.
7. Venturello, C.; Alneri, E.; Ricci, M. JOC 1983, 48, 3831.
8. Itoi, Y.; Inoue, M.; Enomoto, S. BCJ 1985, 58, 3193.
9. Singh, V.; Deota, P. T. SC 1988, 18, 617.
10. Jingfa, D.; Xinhua, X.; Haiying, C.; Anren, J. T 1992, 48, 3503.
11. An, Z.-W.; D'Aloisio, R.; Venturello, C. S 1992, 273.
12. Payne, G. B.; Smith, C. W. JOC 1957, 22, 1682.
13. Oguchi, T.; Ura, T.; Ishii, Y.; Ogawa, M. CL 1989, 857.
14. Ishii, Y.; Adachi, A.; Imai, R.; Ogawa, M. CL 1978, 611.
15. Ishii, Y.; Sakata, Y. JOC 1990, 55, 5545.
16. Sakata, Y.; Ishii, Y. JOC 1991, 56, 6233.
17. Jefford, C. W.; Li, Y.; Jaber, A.; Boukouvalas, J. SC 1990, 20, 2589.
18. (a) Schultz, H. S.; Freyermuth, H. B.; Buc, S. R. JOC 1963, 28, 1140. (b) Ichikawa Y. TL 1988, 29, 4957. (c) Blacklock, T. J.; Butcher, J. W.; Sohar, P.; Lamanec, T. R.; Grabowski, E. J. J. JOC 1989, 54, 3907. (d) Giam, C. S.; Kikukawa, K.; Trujillo, D. A. OPP 1981, 13, 137.
19. (a) Salituro, G. M.; Townsend, C. A. JACS 1990, 112, 760. (b) Dagonneau, M.; Kagan, E. S.; Mikhailov, V. I.; Rozantsev, E. G.; Sholle, V. D. S 1984, 895. (c) Noyori, R.; Suzuki, M. AG(E) 1984, 23, 847.
20. (a) Murahashi, S.-I.; Shiota, T.; Imada, Y. OS 1991, 70, 265. (b) Murahashi, S.-I.; Mitsui, H.; Shiota, T.; Tsuda, T.; Watanabe, S. JOC 1990, 55, 1736. (c) Dehnel, A.; Griller, D.; Kanabus-Kaminska, J. M. JOC 1988, 53, 1566.
21. Murahashi, S-I.; Oda, T.; Sugahara, T.; Masui, Y. CC 1987, 1471.
22. (a) Bunce, N. J.; Stephenson, K. L. CJC 1989, 220. (b) Cory, E. J.; Gross, A. W. OS 1987, 65, 166.

Malcolm Chandler

Glaxo Research & Development, Stevenage, UK

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