Non-heme manganese complexes catalyzed asymmetric epoxidation of olefins by peracetic acid and hydrogen peroxide

Article abstract of DOI:10.1002/adsc.201100030

Chiral non-heme aminopyridine manganese complexes catalyze the enantioselective epoxidation of olefins with peracetic acid or hydrogen peroxide with moderate to high yields and ee valuess up to 89% (peracetic acid, AcOOH) and 84% (hydrogen peroxide, H₂O₂), performing as many as 1000 turnovers.

Full text of DOI:10.1002/adsc.201100030

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DOI: 10.1002/adsc.201100030
Non-Heme Manganese Complexes Catalyzed Asymmetric
Epoxidation of Olefins by Peracetic Acid and Hydrogen Peroxide
Roman V. Ottenbacher,a Konstantin P. Bryliakov,a,* and Evgenii P. Talsia
a
Boreskov Institute of Catalysis, Pr. Lavrentieva 5, Novosibirsk 630090, Russian Federation, and Novosibirsk State
University, Pirogova 2, Novosibirsk 630090, Russian Federation
Fax : (+7)-383-330-8056; phone: (+7)-383-330-6877; e-mail: bryliako@catalysis.ru
Received: January 13, 2011; Published online: April 14, 2011
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201100030.
Abstract: Chiral non-heme aminopyridine manga-
nese complexes catalyze the enantioselective epoxi-
dation of olefins with peracetic acid or hydrogen
peroxide with moderate to high yields and ee val-
uess up to 89% (peracetic acid, AcOOH) and 84%
(hydrogen peroxide, H2O2), performing as many as
1000 turnovers.
lyzed the epoxidation of various alkenes with perace-
tic acid in high yields (90–99%) and demonstrated an
efficiency (TON up to 1000) one order of magnitude
higher than that of the manganese-salen catalysts;
however, the enantioselectivity of the reaction was
not scrutinized.[3] Since then, various related manga-
nese complexes with N4 donor ligands have been pub-
lished.[4] Remarkably, Sun and co-workers reported
the highly enantioselective epoxidation of a,b-enones
(in 70–89% ee) using 1 mol% of manganese amino-
pyridine-type catalysts and 6 equiv. of H2O2,[4e] while
Costas and co-workers epoxidized (non-stereoselec-
tively) a number of alkenes with H2O2 in high yield
using 0.1 mol% of the catalyst in CH3CN/AcOH solu-
tion.[4d,f] Some other manganese-based catalyst sys-
Keywords: asymmetric oxidation; enzyme models;
homogeneous catalysis; hydrogen peroxide; manga-
nese
The discovery of efficient and atom-economic catalyst tems for non-enantioselective oxidations with H2O2
systems for asymmetric epoxidation is an important have been reported.[5]
objective of catalytic chemistry.[1] Since the break-
Recently, we have found that chiral manganese-
through of the groups of Jacobsen and of Katsuki aminopyridine catalysts can conduct the epoxidation
who pioneered the manganese-salen-catalyzed enan- of olefins with different terminal oxidants enantiose-
tioselective oxidations of unfunctionalized olefins,[2] lectively, and gained experimental evidence in favour
no manganese-based catalyst systems achieving com- of the “third oxidant” [LMn(IV)O(OX)]n+ responsi-
parable levels of efficiency and stereoselectivity at the ble for the asymmetric oxygen transfer.[4g] Now, we
same time has been reported. In 2003, Stack and co- report on the enantioselective epoxidations of various
workers published the aminopyridine [Mn(II)
bpmcn](CF3SO3)2] complex 1 (Scheme 1) which cata- oxide over the catalysts [Mn(II)
(CF3SO3)2] (1), [Mn(II)[(S,S)-bpmcn]
and [Mn(II)[(S,S)-pdp](CF3SO3)2] (3) (Scheme 1).
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Apart from the high efficiency (0.1 mol% catalyst
loading), these catalysts demonstrate remarkably high
enantioselection for both terminal oxidants used, as
well as high conversions and chemoselectivities, using
as high as 1.3 equivalents of the terminal oxidant.
Complex 1 was earlier reported and characterized
using X-ray crystallography by Stack and co-work-
AHCTUNGTRENNUNG
ers,[2a] 2 being its (S,S)-enantiomer.[4g] The tetraden-
tate ligand chosen for the preparation of 3 was first
used by White and Chen for the synthesis of a struc-
turally related iron catalyst;[6] 3 features the same cis-
Scheme 1. Complexes 1, 2 and 3.
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Roman V. Ottenbacher et al.
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Scheme 2. Olefins used in this study.
a topology as 1 (see Supporting Information and [7]). from atom economy and environmental points of
Some epoxidation results for alkenes 4–9 (Scheme 2) view. For non-heme iron complexes, H2O2 has been
are given in Table 1.
used previously as the oxidant, in combination with
As reported previously,[4g] the enantioselectivity of acetic acid, for epoxidation, cis-dihydroxylation,[9] and
the epoxidation increased at low temperatures (cf. ex- C H oxidation reactions. Recently, Sun[4e] and Cos-
[6]
À
periments at 08C and at À308C). The presence of tas[4f] have applied H2O2/AcOH combinations in man-
oxygen unaffected the epoxidation.[4g] At 1.0 mol% ganese-based epoxidations. However, the synthetic
catalyst loadings, 1, 2 and 3 gave similar epoxide protocol of Sun exploits 1 mol% loading of the cata-
yields and enantioselectivities, while catalyst 3 per- lyst and requires the use of as high as 6 equivalents of
formed better than 1 at 0.1 mol% loadings (cf. en- H2O2 which is undesirable for preparative synthe-
tries 5 and 6, 10 and 11, 16 and 17).[8]
ses.[10] Given the high stereoselectivities demonstrated
In spite of the remarkable efficiency as well as by the catalyst systems 1–3/AcOOH at 0.1 mol% cata-
chemo- and stereoselectivities of the above catalyst lyst loadings, we have chosen the synthetic protocol[11]
systems, peracids are not optimal terminal oxidants
Table 1. Enantioselective epoxidation of olefins by AcOOH.[a]
No.
Substrate
Catalyst[b]
T [8C]
Conversion/yield[a]
ee (configuration)
1
2
3
4
5
6
7
8
4
4
4
4
4
4
5
5
5
5
5
6
6
6
6
6
6
1 (1.0)
3 (1.0)
1 (1.0)
3 (1.0)
1 (0.1)
3 (0.1)
1 (1.0)
2 (1.0)
3 (1.0)
1 (0.1)
3 (0.1)
1 (1.0)
3 (1.0)
1 (1.0)
3 (1.0)
1 (0.1)
3 (0.1)
0
0
71.0/51.8
48.5/32.8
11.0/8.1
9.0/6.0
53[c]
58[c]
À30
À30
À30
À30
À30
À30
À30
À30
À30
0
67[c]
65[c]
0
–
8.6/5.5
64[c]
97.2/90.3
98.3/94.3
100/93.5
0
100/90.4
100/100
100/100
100/100
100/100
60.6/60.6
100/100
78 (3S,4S)
79 (3R,4R)
82 (3R,4R)
–
78 (3R,4R)
82 (2S,3R)
79 (2R,3S)
89 (2S,3R)
86 (2R,3S)
88 (2S,3R)
88 (2R,3S)
9
10
11
12
13
14
15
16
17
0
À30
À30
À30
À30
[a]
Epoxide yield and enantioselectivity were analyzed as described in the Experimental Section.
Catalyst loading (mol%) in parentheses.
Optical configuration not assigned.
[b]
[c]
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Non-Heme Manganese Complexes-Catalyzed Asymmetric Epoxidation of Olefins
Table 2. Enantioselective epoxidation of olefins by H2O2.[a]
No.
Substrate
Catalyst[b]
T [8C]
Additive
Conversion/yield
ee (configuration)
1
2
3
4
5
6
7
8
4
4
5
5
5
5
6
6
6
6
6
6
6
6
7
8
9
9
1 (0.1)
3 (0.1)
1 (0.1)
3 (0.1)
3 (0.1)
3 (0.1)
1 (0.1)
1 (0.1)
1 (0.1)
3 (0.1)
3 (0.1)
3 (0.1)
1 (0.1)[d]
1 (0.1)[d]
3 (0.1)[e]
3 (0.1)
1 (0.1)[f]
3 (0.1)
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
À30
AA
AA
AA
AA
FA
IBA
AA
FA
IBA
AA
FA
IBA
AA
IBA
AA
AA
AA
AA
94.8/91.3
95.4/92.6
37.0/37.0
73.6/73.6
0
50.7/50.7
94.3/94.3
32.9/32.9
95.4/95.4
97.9/97.9
4.3/4.3
100/100
97.0/97.0
92.5/92.5
57.5/57.5
42.5/42.5
15.6/15.6
60.6/60.6
43[c]
54[c]
68 (3S,4S)
76 (3R,4R)
–
84 (3R,4R)
78 (2S,3R)
71 (2S,3R)
80 (2S,3R)
78 (2R,3S)
–
82 (2R,3S)
78 (2S,3R)
80 (2S,3R)
83 (2R,3S)
77 (2R,3S)
72 (2S,3R)
73 (2R,3S)
9
10
11
12
13
14
15
16
17
17
[a]
Reactions were performed in CH3CN/acid (0.40 mL/0.08 mL); products were analyzed as described in the Experimental
Section; abbreviations: AA=acetic acid, FA=formic acid, IBA=isobutyric acid.
Catalyst loading (mol%) in parentheses.
Absolute configuration not assigned.
95% H2O2 was used.
[b]
[c]
[d]
[e]
[f]
0.80 mL/0.08 mL of CH3CN/AcOH was used.
0.80 mL/0.16 mL of CH3CN/AcOH was used.
of Costas (previously used for non-stereoselective ep- [where the crucial role of the active oxoiron(V) inter-
oxidations[4f]). mediate is established[9c,14]], the existence of an active
Some results are presented in Table 2. One can see oxomanganese(V) intermediate seems unlikely based
that for the oxidation with H2O2, the stereoselectivi- on 18O-labelling data.[15] Additional evidence against
ties were generally somewhat lower than with the Mn(V)=O active intermediate was obtained in
AcOOH[12] (yet still around 80% ee for the epoxida- catalytic experiments with formic and isobutyric acids
tion of chalcone 6 and its heterocyclic counterparts 7– used instead of acetic acid. Indeed, both complexes 1
9), the epoxide yields being moderate to quite high and 3 displayed differing performance and enantiose-
(up to 100%) and the absolute configurations remain- lectivity depending on the acid additive (isobutyric
ing the same as with AcOOH. Noteworthy, no or very acid being the best and formic acid the worst additive,
small side product formation was documented for the Table 2, entries 4–6, 7–9, 10–12), indicating that the
H2O2 oxidations. The use of concentrated hydrogen acid molecule could be incorporated into the active
peroxide did not significantly affect the epoxide yield species. These data argue both against the simple
and ee (cf. entries 7, 9 and 13, 14). We note that this is Lewis acid H2O2 activation pathway and carboxylic
À
the first example of enantioselective aminopyridine acid-assisted heterolysis of the O O bond to generate
manganese-catalyzed epoxidation with a nearly stoi- a high-valence active manganese oxo species.[4f] Fur-
chiometric amount of H2O2.
ther mechanistic studies are needed to establish the
Of particular importance is the nature of the active, valence state of manganese and reliably discriminate
oxygen transferring sites. While the situation with between manganese oxo, peroxo, acylperoxo or other
AcOOH is more or less clear now,[13] the true epoxid- active species.
izing agent in aminopyridine manganese/H2O2 sys-
Overall, the high chemo- and enantioselectivities of
catalysts 1, 2 and 3 are close to those demonstrated
tems is little studied so far.[4d,f]
Oxomanganese(IV) species can be ruled out since by the Katsuki–Jacobsen salen manganese catalysts,[2]
they appeared fairly inactive in olefin epoxidations.[4g] the aminopyridine manganese complexes showing a
Unlike the aminopyridine iron/H2O2 catalyst systems much higher efficiency and capability of using H2O2, a
Adv. Synth. Catal. 2011, 353, 885 – 889
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Roman V. Ottenbacher et al.
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t
(3S,4S) =19.0 min; 6 epoxide: Chiralcel OD-H column, i-
green and atom-economic terminal oxidant. Catalysts
1, 2 and, particularly, 3 are also more efficient and se-
lective than related aminopyridine iron catalysts,[6,8]
which makes chiral aminopyridine manganese com-
plexes challenging protagonists of bio-inspired stereo-
selective oxidation catalysts of near future. Mechanis-
tic studies aimed at the understanding of the stereose-
lective oxygen transfer mechanism will be the subject
of our further investigations.
PrOH:n-hexane=2:98, 1.0 mLminÀ1, 254 nm, t(2S,3R)
=
17.0 min, t(2R,3S) =18.2 min; 7 epoxide: Chiralpak AD-H
column, i-PrOH:n-hexane=20:80, 1.0 mLminÀ1, 220 nm,
t
(2R,3S) =11.0 min, t(2S,3R) =12.7 min; 8 epoxide: Chiralpak
AD-H column, i-PrOH:n-hexane=30:70, 0.8 mLminÀ1,
220 nm, t(2R,3S) =11.4 min, t(2S,3R) =18.4 min; 9 epoxide: Chir-
alpak
AD-H
column,
i-PrOH:n-hexane=20:80,
0.8 mLminÀ1, 220 nm, t(2S,3R) =9.2 min, t(2R,3S) =10.1 min).
Experimental Section
Acknowledgements
1
The authors thank Mr. Bernhard Weibert for the X-ray meas-
urements and Dr. Oleg Lyakin for the synthesis of the ligand
for complex 3. Financial support from the Russian Founda-
tion for Basic Research (grant 09-03-00087) is gratefully ac-
knowledged.
Materials and H NMR Spectra
All solvents were of analytical grade and used without pu-
rification. 30% aqueous H2O2 was either was used as re-
ceived or concentrated under reduced pressure to obtain a
95% solution. All other chemicals [olefins, (R,R)- and (S,S)-
1,2-cyclohexanediamine, (S,S)-2,2’-bispyrrolidine tartrate, 2-
picolyl chloride] were commercial reagents. MnACTHNUTRGNE(UNG SO3CF3)2,
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1
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Adv. Synth. Catal. 2011, 353, 885 – 889
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