POTASSIUM PERMANGANATE–COPPER(II) SULFATE
1
Potassium Permanganate–Copper(II)
Sulfate
KMnO
4
CuSO
4
·
5H
2
O
(KMnO
4
)
[7722-64-7]
KMnO
4
(MW 158.04)
InChI = 1/K.Mn.4O/q+1;;;;;-1/rK.MnO4/c;2-1(3,4)5/q+1;-1
InChIKey = VZJVWSHVAAUDKD-QPPHZJHPAS
(CuSO
4
·5H
2
O)
[7758-99-8]
CuO
4
S
(MW 249.72)
InChI = 1/Cu.H2O4S.5H2O/c;1-5(2,3)4;;;;;/h;(H2,1,2,3,4);5*
1H2/q+2;;;;;;/p-2/fCu.O4S.5H2O/qm;-2;;;;;
InChIKey = JZCCFEFSEZPSOG-QLBZKNHHCL
(oxidant; capable of converting saturated primary alcohols into
carboxylic acids,
1
saturated secondary alcohols into ketones,
2
α
,β-unsaturated alcohols into α,β-unsaturated ketones,
3
dialkyl
and diaryl sulfides into sulfones,
4
diphenyl selenide into diphenyl
selenone,
4
α
,ω-diols into lactones,
1
alkenes into diketones
and α-hydroxy ketones,
5
ω
-hydroxy alkenes into ω-lactones,
6
1,5-dienes into 5-substituted butanolides,
7
and
5
-unsaturated
steroids into the corresponding 5β,6β-epoxy steroids)
Physical Data:
mixture of high melting solids; see entries for
Potassium Permanganate and Copper(II) Sulfate.
Solubility:
sol cold H
2
O; insol CH
2
Cl
2
.
Form Supplied in:
KMnO
4
: purple solid. CuSO
4
·5H
2
O: blue
solid.
Handling, Storage, and Precautions:
oxidant; store in glass con-
tainers at rt.
Introduction. The use of KMnO
4
adsorbed on a solid sup-
port as a heterogeneous oxidant in nonaqueous solvents such as
CH
2
Cl
2
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 evapora-
tion 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 silica
10
–
13
) with Copper(II) Sulfate being the most conve-
nient 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 theo-
retical understanding of its function has been the subject of only
preliminary discussions.
11,14
Oxidation of Secondary Alcohols to Ketones. When potas-
sium permanganate (3 g) and copper(II) sulfate pentahydrate (2 g)
are ground together, a reagent capable of oxidizing both saturated
and α,β-unsaturated secondary alcohols into the corresponding
ketones is produced. When the alcohols (3 mmol) dissolved in
20 mL of CH
2
Cl
2
are added and the heterogeneous mixture re-
fluxed 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 condi-
tions, sulfides and selenides are converted to sulfones and sele-
nones.
4
Oxidation of Primary Alcohols and α,ω-Diols.
If a base
(Cu(OH)
2
·CuCO
3
or KOH) is added, primary alcohols are oxi-
dized to the corresponding carboxylic acids in yields of 80–96%
and in a competition experiment it was found that primary al-
cohols are oxidized in preference to secondary alcohols.
1
Under
similar conditions, α,ω-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’ phase
15
surrounding the solid support. Under such
conditions alkenes are oxidized to α-diketones and/or α-hydroxy
ketones. For example, when 200
L 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 CH
2
Cl
2
(15 mL) and t-butyl alcohol (1.0 mL), α-
hydroxycyclooctanone was obtained in 50% yield after refluxing
for 30 min. Under similar conditions, but with the addition of
Cu(OAc)
2
·H
2
O (1.0 g), 1,2-cyclooctadione was obtained in 48%
yield (eq 2).
HO
HO
O
O
(1)
83%
O
O
O
OH
(2)
50%
48%
With some alkenes, epoxides are obtained instead of ketones.
For example,
5
-unsaturated steroids are readily converted into
the corresponding 5β,6β-epoxides in 90–95% yield (eq 3).
5,8
O
AcO
H
H
H
O
AcO
H
H
H
(3)
O
90%
Oxidation of ω-Hydroxy Alkenes and 1,5-Dienes. When the
omega phase is produced by adding 400
L of water to powdered
KMnO
4
(8 g) and CuSO
4
·5H
2
O (4 g), ω-hydroxy alkenes are
oxidized with the loss of one or more carbons (eq 4).
6
OH
R
2
R
1
O
R
2
R
1
O
52–84%
(4)
Under similar conditions, 1,5-dienes are converted to 5-sub-
stituted butanolides,
7
as opposed to 2,5-bis(hydroxymethyl)tetra-
Avoid Skin Contact with All Reagents
