[82002-29-5] · CuMn2O8 · Copper(II) Permanganate · (MW 427.52)
(oxidant capable of converting saturated and a,b-unsaturated secondary alcohols into the corresponding ketones, primary alcohols and aldehydes into carboxylic acids, and sulfides into sulfones)
Physical Data: high-melting solid.
Solubility: sol water; insol methylene chloride.
Form Supplied in: red solid, commercially available.
Handling, Storage, and Precautions: oxidant, store in glass vessel at rt.
Hydrated copper permanganate is an excellent oxidant for alcohols and sulfides when used heterogeneously in methylene chloride.1,2 For secondary alcohols, the reaction is complete in a few minutes when alcohol (2.5 mmol in 2 mL of methylene chloride) is added to the oxidant (1.2 g, 2.7 mmol). For primary alcohols, aldehydes, and sulfides the reaction time is on the order of 24 h.2,3 In all cases the products are easily isolated in good yields by filtration followed by flash evaporation of the solvent. The anhydrous reagent is much less effective. Examples of typical reactions are given in eqs 1-7.
The presence of alkenes inhibits the oxidation of alcohols4 and sulfides,3 presumably by formation of p-complexes at the active site of the homogeneous reagent, thereby preventing direct contact between the alcohol and the oxidant. Interestingly, although alkenes inhibit the oxidation of other reductants, their presence does not result in reduction of the reagent to an observable extent. It has been suggested that the failure of the reagent to oxidize non-allylic unsaturated alcohols, such as cholesterol, may also be due to formation of a p-complex with the remote double bond.4
A reagent prepared from a finely ground mixture of KMnO4 and CuSO4.5H2O has properties similar to copper(II) permanganate heptahydrate; however, its reactions are in general less vigorous and require longer times to reach completion (see Potassium Permanganate-Copper(II) Sulfate).
Donald G. Lee
University of Regina, Saskatchewan, Canada