Polystyrene-bound Manganese(III) Porphyrin as a Heterogeneous Catalyst for Alkene Epoxidation

Article abstract of DOI:10.1039/a805250f

The manganese(III) complex of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin covalently bound to crosslinked chloromethylated polystyrene can act as an efficient heterogeneous catalyst for alkene epoxidation by sodium periodate.

Full text of DOI:10.1039/a805250f

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788 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 788±789$
Polystyrene-bound Manganese(III) Porphyrin as a
Heterogeneous Catalyst for Alkene Epoxidation$
Shahram Tangestaninejad* and Valiollah Mirkhani
Department of Chemistry, Esfahan University, Esfahan 81744, Iran
The manganese(III) complex of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin covalently bound to crosslinked
chloromethylated polystyrene can act as an efficient heterogeneous catalyst for alkene epoxidation by sodium periodate.
Table 1 Effect of various axial ligands on epoxidation of
cyclooctene with sodium periodate in the presence of
polystyrene-bound manganese porphyrina
Metalloporphyrins have been found to be ecient bio-
mimetic catalysts for alkene epoxidation using various
oxygen atom donors.1±5 However, diculty of recovery and
instability are two of the major drawbacks of these expen-
sive catalysts. The attachment of metalloporphyrin catalysts
to insoluble polymeric supports should prevent inter-
molecular self-oxidation, and simpli®es catalyst recovery
by ®ltration. Furthermore, the support also in¯uences the
selectivity of oxidation.6±10
This report describes a new polymer-bound manganese
porphyrin catalyst which is very easy to prepare and can
be used without degradation in the presence of sodium
periodate for alkene epoxidation.
Epoxide yieldb (%)
Axial ligand
After 1 h
After 2 h
After 3 h
Imidazole
46
45
24
7
80
80
29
10
6
95
95
35
11
7
1-Methylimidazole
tert-Butylpyridine
Pyridine
Without axial base
3
aReaction conditions: cyclooctene (1 mmol), NaIO4 (2 mmol),
axial base (0.2 mmol), catalyst (mass equiv. to 0.04 mmol Mn),
CH3CN±H2O (10 ml±5 ml). bGLC yield based on starting
cyclooctene.
(w/w) of covalently bound manganese porphyrin. The
covalent bonding of the polymer and metalloporphyrin is
so strong that the manganese porphyrin is not eluted
from polymer by water and common organic solvents. The
potential of this supported manganese(III) porphyrin as
catalyst for epoxidation was initially investigated with
cyclooctene in the presence of sodium periodate at
room temperature. The reaction was carried out in a 2:1
CH3CN±H2O mixture in which higher epoxidation yield
was observed.
The e€ect of di€erent axial ligands upon the rate of
epoxidation of cyclooctene was also investigated (Table 1).
The epoxidation rates decrease in the order: imidazole3
1-methylimidazole>tert-butylpyridine>pyridine.
This heterogeneous catalytic system is very ecient for
epoxidation of various alkenes (Table 2). Epoxidation of
trans-stilbene proceeds with complete stereospeci®city and
results in trans-stilbene oxide, whereas epoxidation of cis-
stillbene leads to 90% cis- and 10% trans-stilbene oxide.
Epoxidation of (R)-(‡)-limonene gives a mixture of 1,2- and
8,9-epoxides. The ratio of 1,2- to 8,9-epoxides was found
to be 1:1.
Polymer-bound manganese porphyrin 1 was prepared from
cross-linked chloromethylated polystyrene and 5,10,15,20-
tetrakis(4-aminophenyl)porphyrin by a slight modi®cation
of the previously reported method for non-crosslinked
chloromethylated polystyrene.11 Elemental analysis (Mn)
showed that the supported catalysts contained about 15.4%
Table 2 Epoxidation of alkene with NaIO4 catalyzed by polystyrene-bound manganese porphyrina
Alkene Reaction time/h
Conversion (%)b Epoxide yield (%)b
Cyclooctene
Cyclohexene
Styrene
a-Methylstyrene
p-Methoxystyrene
(‡)-Camphene
(R)-(‡)-Limonene
100
95
75
93
75
70
84
3
1.25
2
2
1.25
3
100
100
100
100
84
70
35 (8,9-Epoxide)
35 (1,2 Epoxide)
71 (trans)
90 (cis)
3
trans-Stilbene
cis-Stilbene
71
100
3
3
10 (trans)
aReaction conditions: alkene (1 mmol), NaIO4 (2 mmol), imidazole (0.2 mmol), catalyst (mass equiv.
to 0.04 mmol Mn), CH3CN±H2O (10 ml±5 ml). bGLC yield based on starting alkene.
*To receive any correspondence.
The activity of this polymer-bound catalyst was compared
to that of the unsupported catalyst in the epoxidation
of styrene and cyclohexene. The results showed that the
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).

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J. CHEM. RESEARCH (S), 1998 789
Progress of the reaction was monitored by GLC. After the reaction
was completed, the polymer beads were ®ltered o€ and the ®ltrate
was extracted with CH2Cl2 and puri®ed by silica gel plate or silica
gel column chromatography. The identities of products were
con®rmed by IR and 1H NMR spectral data.
homogeneous oxidations are faster but less selective.
Commonly observed side reactions such as double bond
cleavage and allylic oxidation are minimized with the
hetereogeneous catalyst.
The solutions remained colourless during the course of
epoxidations and there was no evidence for leaching of
the catalyst from the polymeric support into solution. The
attachment of metalloporphyrin to the polymer made it
possible to remove the stable catalyst by simple ®ltration at
the end of reaction. The stability of the polystyrene-bound
manganese porphyrin catalyst was studied in repeated epoxi-
dation reactions of cyclooctene (eight times) by NaIO4. The
catalyst was reused after each reaction by simple ®ltration
and washing with acetonitrile. The reused catalyst displayed
consistent reactivity and selectivity.
Partial support of this work by Esfahan University
Research Council is gratefully acknowledged.
Received, 7th July 1998; Accepted, 12th August 1998
Paper E/8/05250F
References
1 B. Meunier, Chem. Rev., 1992, 92, 1411.
2 M. Sono, M. P. Roach, E. D. Coulter and J. H. Dawson, Chem.
Rev., 1996, 96, 2841.
Experimental
The porphyrin ligand, 5,10,15,20-tetrakis(4-aminophenyl)porphyrin,
was prepared and metalated according to the literature pro-
cedures.12,13 Alkenes were obtained from Merck or Fluka and were
passed through a column containing active alumina to remove
peroxidic impurities.
Preparation of Polystyrene-bound Manganese(III) 5,10,15,20-Tetra-
kis(4-aminophenyl) Porphyrin.ÐChloromethylated polystyrene cross-
linked with 2% divinylbenzene (2.0 g) (Merck) was suspended
in 100 ml of dimethylformamide (DMF) and 1.67 g (2.48 mmol)
of manganese(III) 5,10,15,20-tetrakis(4-aminophenyl)porphyrin and
5 ml of triethylamine were added. The mixture was re¯uxed for
72 h in the dark under N2 atmosphere while stirring magnetically
and then cooled to room temperature. The dark green resin was
suction ®ltered, washed thoroughly with DMF, methanol and
acetone, respectively, and dried under vacuum at room temperature
for 24 h.
3 T. G. Traylor, C. Kim, J. L. Richards, F. Xu and C. L. Perrin,
J. Am. Chem. Soc., 1995, 117, 3468.
4 A. J. Appleton, S. Evans and J. R. Lindsay Smith, J. Chem.
Soc., Perkin Trans. 2, 1996, 281.
5 A. Maldotti, C. Bartocci, G. Varani, A. Malinari, P. Battioni
and D. Mansuy, Inorg. Chem., 1996, 35, 1126.
6 D. R. Leonard and J. R. Lindsay Smith, J. Chem. Soc., Perkin
Trans. 2, 1991, 25.
7 S. Campestrini and B. Meunier, Inorg. Chem., 1992, 31, 1999.
8 H. S. Hilal, C. Kim and A. F. Schreiner, J. Mol. Catal., 1993,
81, 157.
9 S. Tangestaninejad and M. Moghadam, Synth. Commun., 1998,
28, 427.
10 S. Tangestaninejad and M. Moghadam, J. Chem. Res. (S), 1998,
242.
11 J. Gitzel, H. Ohno, E. Tsuchida and D. Woehrle, Polymer, 1986,
27, 1781.
12 A. S. Semeikin, O. I. Koifman and B. D. Berezin, Khim.
Geterotsikl. Soed., 1982, 10, 1354.
General Procedure for Epoxidation Reactions.ÐA 25 ml ¯ask was
charged with alkene (1 mmol), polystyrene-bound manganese
porphyrin (200 mg), imidazole (0.2 mmol) and CH3CN (10 ml).
After addition of sodium periodate solution (2 mmol in 5 ml of
H2O), the mixture was stirred magnetically at room temperature.
13 A. D. Adler, F. R. Longo, F. Kampas and J. Kim, J. Inorg.
Nucl. Chem., 1970, 32, 2443.