Potassium Permanganate-Copper(II) Sulfate

KMnO4-CuSO4.5H2O
(KMnO4)

[7722-64-7]  · KMnO4  · Potassium Permanganate-Copper(II) Sulfate  · (MW 158.04) (CuSO4.5H2O)

[7758-99-8]  · CuO4S  · Potassium Permanganate-Copper(II) Sulfate  · (MW 249.72)

(oxidant; capable of converting saturated primary alcohols into carboxylic acids,1 saturated secondary alcohols into ketones,2 a,b-unsaturated alcohols into a,b-unsaturated ketones,3 dialkyl and diaryl sulfides into sulfones,4 diphenyl selenide into diphenyl selenone,4 a,o-diols into lactones,1 alkenes into diketones and a-hydroxy ketones,5 o-hydroxy alkenes into o-lactones,6 1,5-dienes into 5-substituted butanolides,7 and D5-unsaturated steroids into the corresponding 5b,6b-epoxy steroids)

Physical Data: mixture of high melting solids; see entries for Potassium Permanganate and Copper(II) Sulfate.

Solubility: sol cold H2O; insol CH2Cl2.

Form Supplied in: KMnO4: purple solid. CuSO4.5H2O: blue solid.

Handling, Storage, and Precautions: oxidant; store in glass containers at rt.

Introduction.

The use of KMnO4 adsorbed on a solid support as a heterogeneous oxidant in nonaqueous solvents such as CH2Cl2 has two very practical advantages. First, in common with most heterogeneous reactions, the product can be isolated simply by filtering to remove the spent oxidant, followed by flash evaporation of the solvent. Second, adsorption of potassium permanganate onto a solid support remarkably improves its selectivity. Various supports have been used (e.g. molecular sieves,9 Alumina,10,11 and silica10,12,13) with Copper(II) Sulfate being the most convenient and versatile.

The water of hydration is important; without it very little or no product is obtained.2 While the role of water in controlling the nature of the products is empirically well documented, a theoretical understanding of its function has been the subject of only preliminary discussions.11,14

Oxidation of Secondary Alcohols to Ketones.

When potassium permanganate (3 g) and copper(II) sulfate pentahydrate (2 g) are ground together, a reagent capable of oxidizing both saturated and a,b-unsaturated secondary alcohols into the corresponding ketones is produced. When the alcohols (3 mmol) dissolved in 20 mL of CH2Cl2 are added and the heterogeneous mixture refluxed for several hours, ketones are formed in excellent yields;3 however, primary alcohols, alkenes, and alcohols unsaturated at a more remote position are not oxidized unless water or a base are added.

Oxidation of Sulfides and Selenides.

Under similar conditions, sulfides and selenides are converted to sulfones and selenones.4

Oxidation of Primary Alcohols and a,o-Diols.

If a base (Cu(OH)2.CuCO3 or KOH) is added, primary alcohols are oxidized to the corresponding carboxylic acids in yields of 80-96% and in a competition experiment it was found that primary alcohols are oxidized in preference to secondary alcohols.1 Under similar conditions, a,o-diols are converted to lactones in good yields (eq 1).

Oxidation of Alkenes.

The presence of a small additional amount of moisture along with some t-butyl alcohol introduces a modification to the reactivity of the reagent by formation of an omega phase15 surrounding the solid support. Under such conditions alkenes are oxidized to a-diketones and/or a-hydroxy ketones. For example, when 200 mL of water was added to a finely ground mixture of potassium permanganate (4.0 g) and copper(II) sulfate pentahydrate (2.0 g) followed by cyclooctene (4 mmol) in CH2Cl2 (15 mL) and t-butyl alcohol (1.0 mL), a-hydroxycyclooctanone was obtained in 50% yield after refluxing for 30 min. Under similar conditions, but with the addition of Cu(OAc)2.H2O (1.0 g), 1,2-cyclooctadione was obtained in 48% yield (eq 2).

With some alkenes, epoxides are obtained instead of ketones. For example, D5-unsaturated steroids are readily converted into the corresponding 5b,6b-epoxides in 90-95% yield (eq 3).5,8

Oxidation of o-Hydroxy Alkenes and 1,5-Dienes.

When the omega phase is produced by adding 400 mL of water to powdered KMnO4 (8 g) and CuSO4.5H2O (4 g), o-hydroxy alkenes are oxidized with the loss of one or more carbons (eq 4).6

Under similar conditions, 1,5-dienes are converted to 5-substituted butanolides,7 as opposed to 2,5-bis(hydroxymethyl)tetrahydrofurans which are formed in the corresponding aqueous reactions (eq 5).16


1. Jefford, C. W.; Wang, Y. CC 1988, 634.
2. Menger, F. M.; Lee, C. JOC 1979, 44, 3446.
3. Noureldin, N. A.; Lee, D. G. TL 1981, 22, 4889.
4. Noureldin, N. A.; McConnell, W. B.; Lee, D. G. CJC 1984, 62, 2113.
5. Baskaran, S.; Das, J.; Chandrasekaran, S. JOC 1989, 54, 5182.
6. Baskaran, S.; Islam, I.; Vankar, P. S.; Chandrasekaran, S. CC 1990, 1670.
7. Baskaran, S.; Islam, I.; Vankar, P. S.; Chandrasekaran, S. CC 1992, 626.
8. Syamala, M. S.; Das, J.; Baskaran, S.; Chandrasekaren, S. JOC 1992, 57, 1928.
9. Regen, S. L.; Koteel, C. JACS 1977, 99, 3837.
10. Quici, S.; Regen, S. L. JOC 1979, 44, 3436.
11. Lee, D. G.; Chen, T.; Wang, Z. JOC 1993, 58, 2918.
12. Ferreira, J. T. B.; Cruz, W. O.; Vieira, P. C.; Yonashiro, M. JOC 1987, 52, 3698.
13. Clark, J. H.; Cork, D. G. CC 1982, 635.
14. Lee, D. G.; Noureldin, N. A. JACS 1983, 105, 3188.
15. Liotta, C. L.; Burgess, E. M.; Ray, C. C.; Black, E. D.; Fiar, B. E. In Phase-Transfer Catalysis; New Chemistry, Catalysts, and Applications; Starks, C. M., Ed.; American Chemical Society: Washington, 1987; p 15.
16. Walba, D. M.; Przybyla, C. A.; Walker, C. B. JACS 1990, 112, 5624 and references therein.

Donald G. Lee

The University of Regina, Saskatchewan, Canada



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