Heterogeneous permanganate oxidations. A novel method for the deamination using solid supported iron-permanganate

Article abstract of DOI:10.1081/SCC-120014768

The heterogeneous use of potassium permanganate supported on ferrous(II)sulphate heptahydrate, provides a simple, efficient and selective means for oxidising aromatic amines to azo and aliphatic amines to carbonyl compounds.

Full text of DOI:10.1081/SCC-120014768

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HETEROGENEOUS PERMANGANATE OXIDATIONS. A
NOVEL METHOD FOR THE DEAMINATION USING SOLID
SUPPORTED IRON-PERMANGANATE
Dhiren C. Barman a , Pramod Saikia a , Dipak Prajapati a & Jagir S. Sandhu b
a Division of Organic Chemistry, Regional Research Laboratory, Jorhat, 785 006, India
b Division of Organic Chemistry, Regional Research Laboratory, Jorhat, 785 006, India
Version of record first published: 22 May 2009.
To cite this article: Dhiren C. Barman , Pramod Saikia , Dipak Prajapati & Jagir S. Sandhu (2002): HETEROGENEOUS
PERMANGANATE OXIDATIONS. A NOVEL METHOD FOR THE DEAMINATION USING SOLID SUPPORTED IRON-PERMANGANATE,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:22,
3407-3412
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 22, pp. 3407–3412, 2002
HETEROGENEOUS PERMANGANATE
OXIDATIONS. A NOVEL METHOD FOR
THE DEAMINATION USING SOLID
SUPPORTED IRON-PERMANGANATE
Dhiren C. Barman, PramodSaikia, Dipak Prajapati,
*
andJagir S. Sandhu
Division of Organic Chemistry, Regional Research
Laboratory, Jorhat 785 006, India
ABSTRACT
The heterogeneous use of potassium permanganate supported
on ferrous(II)sulphate heptahydrate, provides a simple,
efficient andselective means for oxidising aromatic amines
to azo andaliphatic amines to carbonyl compounds.
The use of solidsupportedin synthetic organic chemistry has become
more important in recent years due to the altered reactivity and convenient
product isolation they provide.[1,2] Also it has been studied that permanga-
nate can be usedeffectively as a selective heterogeneous oxidant in organic
solvents, if it is adsorbed on to a hydrated metal cation.[3] Adsorptions onto
solidsupports, cause a change in the chemical properties of many reagents. [2]
One of the most striking examples of such a change in chemical reactivity
*Corresponding author.
3407
DOI: 10.1081/SCC-120014768
Copyright & 2002 by Marcel Dekker, Inc.
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3408
BARMAN ET AL.
[4]
that has been reportedto date is with the potassium permanganate.
The
heterogeneous reaction of sulfides, alkenes, unsaturated alcohols and
benzylic carbons with potassium permanganate supportedon copper sulfate
or alumina are different than heterogeneous aqueous reactions.[5] For
example, some supportedpermanganate reagents will not oxidise carbon–
carbon double bonds.[6] However, other supportedpermanganate oxidations
can be viewedas safer, less toxic andsimpler alternatives for oxidative
cleavage reactions.[7] Herein, in this communication we report, a new
methodfor the deamination of primary aminzes using solidsupported
iron-permanganate as the oxidising reagent.
In a typical procedure, to a paste of potassium permanganate adsorbed
on to hydrated ferrous sulphate, a solution of primary amine in dichloro-
methane was added and the resulting mixture was refluxed with constant
stirring. After completion of the reaction 5–6 h (monitoredby tlc), isolation
of products is achievedby filtration andchromatographic purifications. The
products obtained from this heterogeneous oxidation of primary aliphatic
andaromatic amines are similar to those that have been reportedfor
homogeneous permanganate oxidations. Rawalay and Shechter, for example
have reportedthat cyclohexylamine is convertedto cyclohexanone in 75%
yieldwhen treatedwith permanganate in aqueous solution of tert-butyl
alcohol.[8] Several examples illustrating this novel andrapidprocedure are
illustratedin the Table 1. It is interesting to note that arylamines with electron
withdrawing substituents such as NO2, Cl andBr etc. are efficiently oxidised
to the corresponding azo compounds, which are sometime troublesome to
obtain by the conventional methods. Furthermore, aniline reacts with
neat chromyl chloride explosively and the reaction mixture catches fire
instantaneously, giving out mixture of products.[9] In contrast, the present
study uses solid supports which provide the corresponding azo compounds in
excellent yields without the formation of any other side products. The alipha-
tic primary amines possessing a-hydrogens underwent oxidation selectively

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HETEROGENEOUS PERMANGANATE OXIDATIONS
3409

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3410
BARMAN ET AL.
to produce the corresponding carbonyl compounds without undergoing any
kindof prototropic rearrangement. [10] But the reaction is not effective when
anhydrous ferrous sulphate was used instead of hydrated ferrous sulphate in
the above reaction i.e., hydration of the inert solid provides better efficiency of
the reaction. We have also notedthat nickel sulphate hexahydrate, manga-
nese sulphate monohydrate and magnesium sulphate heptahydrate can also
[11]
be successfully usedas solidsupport.
Moreover, when the oxidation was
carried out with primary amines dissolved in dichloromethane by potassium
permanganate without the aidof solidsupports, we observedthe formation
of corresponding oxidised products in 40–50% yields only. Although the
mechanism of the reaction remain obscure at this stage, this investigation
reports a experimental procedure that is superior to others reported in the
literature.[12]
In conclusion, the use of potassium permanganate supportedon
ferrous(II)sulfate provides a selective and convenient method for the oxida-
tion of primary amines to azo and carbonyl compounds. The procedure
utilises inexpensive reagents, the work-up is simple, side products are
minimal, mild reaction conditions and excellent yields. Also the method
avoids the use of chromic acid, which should allow its wider application in
organic synthesis.
EXPERIMENTAL
Mps/bps were determined using a Buchi melting point apparatus and
are uncorrected. IR spectra were recorded for KBr discs on a Perkin-Elmer
240C analyser. The 1H NMR spectra were recorded on Bruker AC-80 spec-
trometers as CDCl3 solutions andchemical shift values are in ꢀ units (ppm)
relative to Me4Si as internal standard. The amines obtained from the Aldrich
Chemical Co., was purifiedby distillation, flash chromatography or recrys-
tallization prior to use. Purity of the amines was confirmedby melting points
and NMR analysis. The oxidant was prepared by grinding equal amount by
weight of KMnO4, andFeSO 4, 7H2O in a mortar until homogeneous.
Oxidation of Aromatic and Aliphatic Primary Amines with
SupportedKMnO
4
A homogeneous mixture of the oxidant was prepared by grinding
gently the equal amount of KMnO4 (1 g) andFeSO 4-7H2O (1 g) in a
morter. The amine, 4-bromoaniline (0.35 g, 2 mmol) in dichloromethane
(20 mL) was taken in a 50 mL roundbottomedflask. The oxidant (2.0 g)

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HETEROGENEOUS PERMANGANATE OXIDATIONS
3411
was added and the heterogeneous mixture stirred under reflux for 5 h. The
progress of the reaction was monitoredby tlc until no starting material
could be detected. After cooling to room temperature the product was
then filtered through celite and the residue washed thoroughly with dichloro-
methane (3 ꢁ 15 mL) andiedthylether (3
ꢁ 15 mL) andrdiedover
anhydrous sodium sulphate. Removal of the solvent and purification of
the residue by column chromatography on silica gel gave the corresponding
1,2-bis(4-bromophenyl)diazene m.p. 200–210ꢀC (lit.[13] m.p. 203–205ꢀC) in
96% yield. The corresponding control reaction in the solid state i.e., without
dichloromethane at room temperature produced only 60% yield of
1,2-bis(4-bromophenyl)diazene. There was no evidence for the formation
of any other products. Treatment of other aromatic amines in CH2Cl2
gave the corresponding azo compounds, in 80–95% yields, as summarised
in the Table 1. When cyclohexylamine was usedin the above reaction
in place of 4-bromoaniline andstirredunder reflux for 6 h, after usual
workup, cyclohexanone was obtainedin 90% yieldwithout the formation
of any azo compounds. Similarly other aliphatic amines were reacted
andcharacteristics of the proudcts are recoreddin the Table 1. All
isolated aldehydes and azo compounds (known in the literature) were
fully characterisedby 1H NMR, IR andMass spectral data andcomparison
with authentic samples.
REFERENCES
1. Fatiadi, A.J.; Synthesis 1987, 85; Menger, F.M.; Lee, C. J. Org. Chem.
1979, 44, 3445.
2. Smith, K., Ed. Solid Supports and Catalysis in Organic Synthesis, Ellis
HorwoodandPTR Prentice Hall: New York, 1992; Laszlo, P.
In Comprehensive Organic Synthesis; Trost, B.M., Ed.; Pergamon:
New York, 1991, Vol. 7, p. 839.
3. Menger, F.M.; Lee, C. Tetrahedron Lett. 1981, 22, 165; Wolfe, S.;
Ingold, C.F. J. Am. Chem. Soc. 1983, 105, 7755.
4. Lee, D.G. In Encyclopedia of Reagents for Organic Synthesis; Paquette,
I.A., Ed.; Wiley: New York, 1995; pp. 4274–4281.
5. Fatiadi, A.J. Synthesis 1987, 85.
6. Smith, K., Ed. Solid Supports and Catalysis in Organic Synthesis;
Prentice Hall: New York, 1992; Menger, F.M.; Lee, C.J. J. Org.
Chem. 1979, 3446.
7. Hayes, R.B. In Biological and Environmental Aspects of Chromium;
Langard, S., Ed. Elsevier Biochemical: New York, 1982; Ch. 10; Van
Rheenen, V. J. Chem. Soc., Chem. Commun. 1969, 314.

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3412
BARMAN ET AL.
8. Rawalay, S.S.; Sheeter, H. J. Org. Chem. 1963, 32, 3129.
9. Nallaiah, C.; Strickson, J.A. Tetrahedron 1986, 42, 4089; Strickson,
J.A.; Leigh, M.J. Tetrahedron 1968, 24, 5145.
10. Jayachandran, B.; Sasidharan, M.; Sudalai, A.; Ravindranathan, T.
J. Chem. Soc., Chem. Commun. 1995, 1523.
11. Barman, D.C.; Saikia, P.; Prajapati, D.; Sandhu, J.S. Unpublished
results.
12. Using mercuric acetate see: Leonard, N.J.; Morrow, D.F. J. Am.
Chem. Soc. 1958, 80, 371; Using chlorine dioxide see: Hult, I.A.;
Davis, G.T.; Rosenblatt, D.H.; Williams, H.K.R.; Weglein, R.C.
J. Am. Chem. Soc. 1967, 89, 1163; Using bezoyl peroxide see:
Buckley, D.; Dunstan, S.; Henbest, H.B. J. Chem. Soc. 1957, 4901;
Using alkyl hydroperoxides see: De La Mare, H.E. J. Org. Chem.
1960, 25, 2114; Using nitrous acidsee: Smith, P.A.S.; Leoppky, R.N.
J. Am. Chem. Soc. 1967, 89, 1147.
13. Observedmps/bps are same as reportedin the literature see: Dictionary
of Organic Compounds, 4th Ed.; E. & F. N.: Spain, London, 1965.
Receivedin the Netherlands November 11, 2001