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Topic: Potassium permanganate and active Manganese dioxide as oxidants  (Read 4119 times)

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Offline Zainb

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Potassium permanganate and active Manganese dioxide as oxidants
« on: January 31, 2012, 12:55:10 PM »
The combination of potassium permanganate and active manganese dioxide (KMnO4/MnO2) produces a reagent that can be used effectively for the oxidation of alcohols to carbonyl compounds as shown below.





Any idea about the resulting reagent from this combination?

Usually KMnO4 is used to oxidize alkenes.

Thanks for any help..

Offline discodermolide

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Re: Potassium permanganate and active Manganese dioxide as oxidants
« Reply #1 on: January 31, 2012, 03:07:02 PM »
The combination of potassium permanganate and active manganese dioxide (KMnO4/MnO2) produces a reagent that can be used effectively for the oxidation of alcohols to carbonyl compounds as shown below.





Any idea about the resulting reagent from this combination?

Usually KMnO4 is used to oxidize alkenes.

Thanks for any help..


I see you obtained this from the following paper. The title says it all!
I guess it is not a reagent but a supporting medium, similar to Pd/C.
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Offline Zainb

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Re: Potassium permanganate and active Manganese dioxide as oxidants
« Reply #2 on: February 02, 2012, 04:31:03 AM »
I have seen the complete paper,,, but they did not explain the mechanism...

They used 17.3 equivalents from MnO2 and just 32 equivalents from KMnO4,,, Then the permanganate just a catalyst,,, I try to use this regent on alkenyl compound but the reaction mechanism still unclear.

Offline orgopete

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Re: Potassium permanganate and active Manganese dioxide as oxidants
« Reply #3 on: February 02, 2012, 08:34:28 AM »
I have not seen the paper. I don't know that the mechanism for KMnO4 oxidations of benzylic CH's has been proven, but it is generally believed to involve a radical reaction. From there, oxidation reactions generally involve
       H-C-O-X  :rarrow: H+ + C=O + X-

where X is any group able to accept electrons, MnOn, CrOn, Br, Cl, Ag, etc.

Although the first step is usually carried out a elevated temperatures (to improve radical formation?), the reference reaction was carried out under mild conditions. If your substrate fails to react, I should presume the radical allylic oxidation step has a higher activation energy than is being supplied in this reaction. (If you have an alkene, I am surprised the hydroxylation reaction (similar to OsO4 oxidation) is not occurring directly.)
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Offline Zainb

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Re: Potassium permanganate and active Manganese dioxide as oxidants
« Reply #4 on: February 15, 2012, 03:15:16 AM »
the hydroxy group is a good nucleophile, which will attack the metal atom centr in the MnO2 (SN2) and  then one of oxynium atom of the intermediate, R2-CH-O-MnO2H, will depronate the proton in the cyclic transition state leading to the carbony compound 

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