The dinuclear manganese complex Mn2O(OAc)2(TPTN) as a catalyst for epoxidations with hydrogen peroxide

Article abstract of DOI:10.1039/a910232i

In acetone and at ambient temperature, the dinuclear manganese complex of TPTN is able to catalyse the oxidation of several alkenes to the corresponding epoxides with high turnovers numbers (up to 900) using H₂O₂ as oxidant.

Full text of DOI:10.1039/a910232i

The dinuclear manganese complex Mn O(OAc) (TPTN) as a catalyst for
2
2
epoxidations with hydrogen peroxide†
a
b
c
a
Jelle Brinksma, Ronald Hage, Judith Kerschner and Ben L. Feringa*
a
Laboratory of Organic Chemistry, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen,
The Netherlands. E-mail: B.L.Feringa@chem.rug.nl
Unilever Research Laboratory Vlaardingen, PO Box 114, 3130 AC Vlaardingen, The Netherlands
Unilever Research US, 45 River Road, Edgewater, New Jersey 07020, USA
b
c
Received (in Cambridge, UK) 17th December 1999, Accepted 24th February 2000
Published on the Web 15th March 2000
In acetone and at ambient temperature, the dinuclear
manganese complex of TPTN is able to catalyse the
oxidation of several alkenes to the corresponding epoxides
with high turnovers numbers (up to 900) using H
oxidant.
2 2
O as
Selective oxidation of alcohols to aldehydes and the formation
of epoxides from olefins are among the key reactions in organic
chemistry. In the ongoing pursuit to develop environmentally
benign synthetic methodology there is currently great interest in
new and more efficient catalytic versions of these oxidations.
Compared to catalytic methods that require oxidants like NaOCl
2 2
and ammonium periodates the use of H O offers the advantage
that it is a cheap, environmentally friendly and a readily
available reagent. Since water is the only expected byproduct,
synthetic applications of this reagent are undoubtedly appealing
provided efficient catalysis is accomplished.
Recently a number of metal complexes have been found to be
2 2
suitable catalysts for selective epoxidation reactions with H O
as oxidant.1 Noyori and coworkers reported a catalytic system
based on Na WO dihydrate for the epoxidation of terminal
olefins and turnovers numbers (TON) were found in the range
50–200 per W atom by using 150 mol% H and 0.2–2 mol%
–4
2
4
1
2 2
O
1
of the catalyst. Methyltrioxorhenium (MTO) is also emerging
as a highly suitable epoxidation catalyst.2 A remarkable
acceleration effect on the epoxidation rate was found by
Sharpless and coworkers by using pyridine and pyridine
derivatives for the MTO catalysed epoxidation of terminal and
3
5
internal olefins. The Jacobsen catalyst and the related Katsuki
Advantages of this type of ligands are the accessibility and the
possibility for ligand modification. The ligands and manganese
complexes examined here were synthesised following literature
6
catalyst are commonly applied for asymmetric epoxidation
reactions of cis-olefins. However, with a few exceptions7
NaOCl is used as oxidant for which TON values in the range of
procedures and complexes 2 (and 3) have been reported as
35–40 were found. Recently it was found that a manganese(iv)
mimics for the photosystem II (PS II).12–15 Preliminary
complex based on the N,NA,NB-1,4,7-trimethyl-1,4,7-triazacy-
clononane (MeTACN) ligand is a highly active oxidation
catalyst.4
screening in a number of different catalytic epoxidations
showed that complex 3 based on TPEN,† featuring a two-
carbon spacer between the three N-donor sets in the ligand, was
unreactive in epoxidation reactions.§ In sharp contrast, complex
2, based on TPTN with a three-carbon spacer, is able to catalyse
the oxidation of various alkenes to the corresponding epoxides,
with H O as oxidant in acetone and at ambient temperature
This dinuclear manganese complex 1 is capable of the
epoxidation of alkenes with TON usually below 1008 but in
,9
2 2
some cases up to 1000 have been reported using H O as
10
oxidant. ‡ This complex was also shown by us to be a highly
active and selective catalyst for the oxidation of benzyl alcohols
to benzaldehydes (TON up to 1000).11 Synthesis and modifica-
tions of the MeTACN ligand are, however, not easily accom-
plished due to lengthy and tedious preparation whereas the
sensitivity of the corresponding metal complexes to changes in
the MeTACN structure often leads to completely inactive Mn-
complexes. Therefore a challenge is the design of novel
dinucleating ligands featuring the three N-donor set for each
Mn-site and retaining the high oxidation activity. We present
here, high catalytic epoxidation activity for the manganese
2
2
(Scheme 1).
Catalytic reactions were performed under a nitrogen atmos-
phere using 1 equiv. of complex 2, 1000 equiv. substrate and
H O was used as oxidant (1 ml of 30% aqueous H O , 9.8 mM,
2
2
2 2
8 equiv. with respect to substrate).¶ During the oxidation
reaction in acetone at room temperature gas bubbles developed
rapidly when the excess of oxidant was added. As for the
reactions using 14,11 part of the H O disproportionates to O .
2
2
2
An increase of the catalyst TON was obtained by performing the
2 2
complex 2 based on the ligand TPTN† using H O as oxidant.
†
1
Abbreviations TPTN = N,N,NA,NA-tetrakis(2-pyridylmethyl)propane-
,3-diamine, TPEN = N,N,NA,NA-tetrakis(2-pyridylmethyl)ethane-1,2-di-
amine.
DOI: 10.1039/a910232i
Chem. Commun., 2000, 537–538
This journal is © The Royal Society of Chemistry 2000
537

Table 1 Oxidation of selected olefins with Mn
2
2
O(OAc)
2
(TPTN) complex
Main advantages of the new catalytic system are the facile
synthesis and possibility for ligand modification. In acetone and
at ambient temperature the manganese complex of TPTN is able
to catalyse the selective oxidation of various alkenes to the
corresponding epoxides, with H O as oxidant. Further studies
2 2
towards the elucidation of the mechanism and introduction of
chirality in the ligand are in progress.
a
TON
h, 4 h, 2 h, 4 h,
2
Productb
c
d
c
d
Entry Substrate
298 K 298 K 273 K 273 K
1
Styrene
Styrene oxide
Benzaldehyde
Cyclohexene
oxide
Cyclooctene
oxide
157
5
208
75
176
2
271
14
Cyclohexene
Cyclooctene
Notes and references
2
3
4
247
563
328
868
‡ Very recently a co-ligand effect was reported by the groups of De Vos and
Berkessel, see: D. E. De Vos, B. F. Sels, M. Reynaers, S. Rao and P. A.
Jacobs, Tetrahedron Lett., 1998, 39, 3221; A. Berkessel and C. A. Sklorz,
Tetrahedron Lett., 1999, 40, 7965
193
49
636
93
262
61
219
575
48
321
cis-Diol
Cinnamyl alcohol Cinnamyl oxide 208 219
Cinnamyl
§ L. Fraisse, J. J. Girerd, F. Perie, A. Rabion, D. Tetard, J. B. Verlhac and
A. Nivorozhkin, PCT WO 97/18035 Elf-Aquitaine. Oxidation catalysis
with various Mn and Fe complexes based on amine-heteroaromatic ligands
has been claimed recently (e.g. cyclohexane oxidation, polyaromatic
oxidation). No epoxidation activity was given however.
¶ Catalytic reactions were started by mixing 1.0 ml of a 1.2 mM stock
solution of the manganese complex in acetone and 1.0 ml of a 1.2 mM stock
solution of substrate at 25 °C under a nitrogen atmosphere. As an internal
standard, bromobenzene or 1,2- dichlorobenzene (in the case of cyclooc-
tene) were used. After stirring for 2 min, an excess of hydrogen peroxide
aldehyde
Benzaldehyde
trans-Oct-2-ene
oxide
trans-oct-2-ene
oxide
1-Decene oxide 28
trans-oxide
cis-oxide
69
22
85
47
70
21
86
46
trans-2-Octene
trans-4-Octene
5
118
97
188
178
248
6
7
8
148
34
84
153
80
23
210
97
115
147
1-Decene
cis-b-Methyl-
styrene
19
43
104
44
a
Experimental conditions, see text. b All products were identical to
2 2
(1.0 ml of 30% aqueous H O , 9.8 mM, 8 eq. with respect to substrate) was
added. The progress of the reaction was monitored by GC, by removing
small samples of the reaction mixture and filtering over a short column of
silica. To establish the identity of the epoxides and other products
unequivocally, the retention times and spectral data were compared to those
of commercially available and independently synthesised compounds.
independent samples and identified by GC (HP 6890, column HP1 15 3 0.3
1
c
mm 3 2.65 mm, polydimethylsiloxane) and H NMR. Turnover number =
with respect to substrate. d 16
mol product per mol catalyst, 8 equiv. H
equiv. H with respect to substrate.
2 2
O
2 2
O
1
K. Sato, M. Aoki, M. Ogawa, T. Hashimoto and R. Noyori, J. Org.
Chem., 1996, 61, 8310.
catalytic reactions in acetone at 0 °C suppressing H
decomposition. For the selected olefins generally up to 300
TONs were found. Addition of a further 1 ml of H (30%
2 2
O
2 W. A. Herrmann, R. W. Fischer and D. W. Marz, Angew. Chem., Int. Ed.
Engl., 1991, 30, 1638.
3
2 2
O
J. Rudolph, K. L. Reddy, J. P. Chiang and K. B. Sharpless, J. Am. Chem.
Soc., 1997, 119, 6189.
R. Hage, J. E. Iburg, J. Kerschner, J. H. Koek, E. L. M. Lempers, R. J.
Martens, U. S. Racherla, S. W. Russell, T. Swarthoff, M. R. P. van Vliet,
J. B. Warnaar, L. van der Wolf and B. Krijnen, Nature, 1994, 369,
aqueous solution in water, 9.8 mmol, 8 equiv. with respect to
substrate) resulted in an considerable increase in epoxide yield
after 4 h (total TON up to 900, for cyclohexene). These results
indicate that the catalyst is very robust under the conditions
used. High selectivity is observed and it should be emphasized
that in the epoxidation reaction of cyclic alkenes (especially for
cyclohexene), besides the epoxides, no allylic oxidation
products were found. In control experiments replacing
4
6
37.
5
J. F. Larrow, E. N. Jacobsen, Y. Gao, Y. Hong, X. Nie and C. M. Zepp,
J. Org. Chem., 1994, 59, 1939.
6 N. Hosoya, A. Hatayama, K. Yanai, H. Fujii, R. Irie and T. Katsuki,
Mn
2
O(OAc)
2
(TPTN) 2 with Mn(OAc)
3
·3H
2
O, strong peroxide
Synlett, 1993, 641.
P. Pietikäinen, Tetrahedron, 1998, 54, 4319.
D. E. De Vos and T. Bein, J Organomet. Chem., 1996, 520, 195.
P. P. Knops-Gerrits, D. E. De Vos and P. A. Jacobs, J. Mol. Catal. A.,
7
8
9
decomposition and no epoxide formation was found. Data for
the conversion of various alkenes to the corresponding epoxides
are compiled in Table 1. Styrene epoxidation is accompanied by
the formation of a small amount of benzaldehyde; a feature
commonly observed with epoxidation of this substrate. Cinna-
myl alcohol also showed some cleavage and alcohol oxidation
leading to benzaldehyde and cinnamyl aldehyde, respectively.
A substantial amount of trans-epoxide is obtained in the
1
997, 117, 57.
1
1
0 D. E. De Vos and T. Bein, Chem. Commun., 1996, 917.
1 C. Zondervan, R. Hage and B. L. Feringa, Chem. Commun., 1997,
4
19.
12 H. Toftlund and S. Yde-Andersen, Acta Chem. Scand. Ser. A, 1981, 35,
575.
13 H. Toftlund, A. Markiewicz and K. S Murray, Acta Chem. Scand., 1990,
4, 443.
4 J .B. Mandel, C. Maricondi and B. E. Douglas, Inorg. Chem., 1988, 27,
990.
5 S. Pal, J. W. Gohdes, W. Christian, A. Wilisch and W. H. Armstrong,
Inorg. Chem., 1992, 31, 713.
reaction of cis-b-methylstyrene with H
2
O
2
in the presence of
4
catalyst 2 which is usually attributed to the formation of a
radical intermediate with a lifetime sufficient for internal
rotation before ring closure.16 Excellent results were also found
for internal alkenes e.g. entries 5 and 6 whereas slightly lower
yields were found for terminal linear alkenes.
1
1
1
2
6 W. Zhang, N. H. Lee and E. N. Jacobsen, J. Am. Chem. Soc., 1994, 116,
In conclusion, we have demonstrated that the manganese
complex 2 based on TPTN is a promising catalyst in catalytic
4
25.
epoxidation procedures using H
2
O
2
as the terminal oxidant.
Communication a910232i
538
Chem. Commun., 2000, 537–538