Highly selective and efficient olefin epoxidation with pure inorganic-ligand supported iron catalysts

Article abstract of DOI:10.1039/c9dt02997d

Over the past two decades, there have been major developments in the transition iron-catalyzed selective oxidation of alkenes to epoxides; a common structure found in drug, isolated natural products, and fine chemicals. Many of these approaches have enabled highly efficient and selective epoxidation of alkenes via the design of specialized ligands, which facilitates to control the activity and selectivity of the reactions catalyzed by iron atom. Herein, we report the development of the olefin epoxidation with inorganic-ligand supported iron-catalysts using 30% H₂O₂ as an oxidant, and the mechanism is similar to iron-porphyrin type. With the catalyst 1, (NH₄)₃[FeMo₆O₁₈(OH)₆], various aromatic and aliphatic alkenes were successfully transformed into the corresponding epoxides with excellent yields as well as chemo- and stereo-selectivity. This catalytic system possesses the advantages of being able to avoid the use of expensive, toxic, air/moisture sensitive and commercially unavailable organic ligands. The generality of this methodology is simple to operate and exhibits high catalytic activity as well as excellent stability, which gives it the potential to be used on an industrial scale, and maybe opens a way for the catalytic oxidation reaction via inorganic-ligand coordinated iron catalysis.

Full text of DOI:10.1039/c9dt02997d

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DOI: 10.1039/C9DT02997D
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ARTICLE
Highly Selective and Efficient Olefin Epoxidation with Pure
Inorganic-ligand Supported Iron Catalysts
Zhuohong Zhou, ‡a Guoyong Dai, ‡a,b Shi Ru, b Han Yu,a,b* Yongge Wei,b,c*
Received 00th January 20xx,
Accepted 00th January 20xx
Over the past two decades, there have been major developments in transition iron-catalyzed selective oxidation of alkenes
to epoxides, a common structure found in drug, natural products isolated, and fine chemicals. Many of these approaches
have enabled the highly efficient and selective epoxidation of alkenes through the design of specialized ligands, which
facilitates to control the activity and selectivity of reactions catalyzed by iron atom. Herein, we report the development of
an iron-porphyrin type of mechanistic resemble those of iron-porphyrin for the olefin epoxidation with inorganic-ligand
supported iron-catalysts using 30% H2O2 as an oxidant. With the catalyst 1, (NH4)3[FeMo6O18(OH)6], various aromatic and
aliphatic alkenes have been successfully transformed into the corre-sponding epoxides with excellent yields and chemo- and
stereo-selectivity. This catalytic system possesses the advantages of being able to avoid the use of expensive, toxic,
air/moisture sensitive and being commercially unavailable organic ligands. The generality of this methodology is simple to
operate and exhibits high catalytic activity as well as excellent stability, which gives it the potential to be used on an industrial
scale, and maybe opens a way for the catalytic oxidation reaction via inorganic-ligand coordinated iron catalysis.
DOI: 10.1039/x0xx00000x
www.rsc.org/
unavailable.5,6 Moreover, increasing the durability and
recyclability of organometallic iron-catalysts under mild
conditions remains a major challenge in industrial and synthetic
chemistry due to the susceptibility of the organic ligands to
undergo oxidative self-degradation. Therefore, the innovation
and improvement of catalytic epoxidation methods with other
ligand-supported iron catalysts, which provides an alternative
approach to the use of structurally complex ligand systems, is
highly desired.
Introduction
The selective oxidation of organic compounds remains
challenging and is an important transformation both
synthetically and in nature. Such reactions require inexpensive
and selective catalysts, high atom efficiency, and
environmentally benign oxidants. Among various oxidation
reactions, the catalytic olefin epoxidation using iron complexes
(e.g., iron-porphyrin or iron complexes bearing N-based ligands,
Fig. 1A) and environmentally benign oxidants (e.g., H2O2 or O2)
has attracted much attention. Epoxidation strategies that
achieve high selectivity under environmentally friendly
conditions are greatly desired because epoxides are highly
Catalyst
R3
R4
R2
O
R3
R1
R1, R2, R3, R4= H, alkyl or aryl
R4
R1
R2
O2 or H2O2
A Iron Complexes Catalysts
(e.g., iron-porphyrin or iron complexes bearing N-based ligands)
useful building blocks for
a number of subsequent
Ar
Ar
transformations in organic synthesis.1-4 In iron complexes
catalytic systems, ligands are essential for controlling the
reactivity and selectivity of olefin epoxidation reactions.
However, most organic ligands suffer from the problems of
being expensive, toxic, air/moisture sensitive and commercially
H3
C
CH3
N
N
N
N
N
N
N-
-N
N
N
N
N
Ar
Ar
Porphyrin
BPMEN
TPA
Representative Porphyrin,BPMEN and TPA ligands for the iron-catalyzed epoxidation of olefins
Inorganic-ligand Supported Iron-Catalysts
B
3-(NH4
)
3
O
O
Mo
O
a.
O
This work
O
School of Chemical and Environmental Engineering, Shanghai Institute of
O
O
Mo
Technology, Shanghai 201418, P.R. China. E-mail: scihanyu@163.com
b. Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of
Education, Department of Chemistry. Tsinghua University, Beijing 100084, P.R.
China. E-mail: hanyu0220@ tsinghua.edu.cn; yonggewei@ tsinghua.edu.cn
O
O
O
O
O
O
Fe
Mo
Mo
O
O
O
O
O
O
O
Mo
O
Mo
O
O
c.
O
State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing
100191, P.R. China. E-mail: ygwei@pku.edu.cn
FeMo (
6O18 OH)6]
(NH4
)
[
3
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
‡ These authors contributed equally to this work.
Fig. 1. Alkene epoxidation catalyzed by iron catalysts.
Catalytically active, stable complexes involving low-valence
metals ions supported/coordinated by metal oxides are
commonplace. Many of these inorganic-ligand coordinated
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complexes contain dispersed metal ions with a variable number oxidant. This catalyst exhibits high catalytic activity and
View Article Online
DOI: 10.1039/C9DT02997D
of metal-oxygen bonds between the scaffold and the metal selectivity, and possess excellent stability during catalytic cycles
sites, providing complexes that are more stable than (Fig S8 and S9). One of the main advantages of this catalytic
organometallic
catalysts.
Inspired
by
this
idea, system is that it can avoid the use of complicated/sensitive
polyoxometalates (POMs) are considered to be an inorganic organic ligands and expensive tungsten-based POMs.
alternative to classical transition-metal complexes. The catalytic
function of POMs has attracted much attention because their
ability to design catalytically active sites allows for ‘fine-tuning’
Results and discussion
of their redox and acidic properties at the atomic or molecular
levels. number of tungsten-based POMs have been
Our initial studies were begun with the oxidation of cyclohexene
as a model substrate using the inorganic-ligand supported iron
catalyst 1 and 30% H2O2 as the sole oxidant at 50 °C (Table 1).
Subsequently, the influence of solvents and additives on the product
yield and selectivity was investigated. Gratifyingly, with regards to
other solvents, acetonitrile was found to be a suitable solvent for the
epoxidation of cyclohexene, with the epoxidized product being
obtained in 99% yields and with 99% selectivity (Table 1, entry 3-7).
We found that the efficiency of the transformation was strongly
affected by the additives. When the reaction was carried out in the
absence of an additive, the yield and selectivity of the epoxidation
products were significantly reduced. The influence of different
additives (Na2CO3, K2CO3, NaAc and NaCl) on product yields obtained
from olefin epoxidation was investigated (Table 2, entries 12-16).
A
successfully employed as H2O2 or O2-based epoxidation
catalysts under homogeneous and heterogeneous conditions.
Although significant progress has been made in these tungsten-
based POMs, the challenge including costs still exists. The
activity and selectivity of epoxides are difficult to be controlled
using a single category catalyst, the substrate scope still keeps
limited, and high reaction temperatures are required which
sometimes reduce the selectivity and efficiency. Inspired by the
milestone work of Neumann, Mizuno and Hill in POMs
catalysis7,8,11 and according to previous studies concerning the
chemistry of POMs12-15, we have envisioned that the B-type
Anderson-structured POMs could be employed in epoxidation
reactions16-22. These structures are unique since they are made
up of a single metal atom coordinated by a polyoxomolybdate
or polyoxotungstate which consists of six edge-sharing MO6 (M
= W or Mo) octahedra surrounding a central, edge-sharing
metal heteroatom octahedron (XO6) with six protons attached
on to the apical oxygen atoms. The MoVI centers, positioned
around the central heterometal, not only greatly enhance the
Lewis acidity of the catalytically active sites but also enable the
edge-sharing MO6 unit to act as ligands analogous to those used
in traditional organometallic complexes. This, together with
their inherent resistance towards oxidation and high stability in
solution, makes Anderson POMs ideal candidates for solving
those problems associated with the instability and activity of
complex catalysts commonly encounter in organometallic
catalysis, and thus provides a potential alternative for aerobic
oxidation. Furthermore, the Anderson POMs, which bear an
easily accessible central metal heteroatom, a small molecular
structure and well-defined active sites, allow for a more rational
development of the catalyst based on structure-activity
relationship. Indeed, very recently, our group23 has confirmed
that Anderson POMs can be exploited as inorganic ligand-
coordinated metal catalysts for the highly efficient aerobic
oxidation of aldehydes to carboxylic acids in water under mild
conditions. However, to the best of our knowledge, the use of
Anderson POMs as catalysts for the epoxidation of olefins has,
until now, not been developed. Herein, we report that an
Table 1. Influence of additives and solvents a
1a
Cat. (0.1 mol %)
additive (0.1 equiv.)
solvent, 50 oC, 8 h
H2O2
O
+
Cat.
(mol%)
-
Additive
Sel.
(%)b
-
Yield
(%)c
Entry
Solvent
(0.1 eq.)
NaHCO3
-
1
2
CH3CN
CH3CN
CH3CN
CH2Cl2
DMF
-
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.05
0.2
0.5
0.1
0.1
76
99
95
91
89
93
93
97
92
90
96
99
99
95
99
52
99
93
82
75
72
62
77
83
59
87
99
99
83
95
3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
Na2CO3
K2CO3
4
5
6
DMSO
H2O
7
8
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
9
10
11
12
13
14
15d
16e
NaCl
NaAc
NaHCO3
NaHCO3
NaHCO3
NaHCO3
NaHCO3
aReaction conditions: Cat.1(0.1 mol%), cyclohexene (1 mmol),
H2O2 (1.5 equiv.), additive (0.1 equiv.), solvent (2 mL).b,c
Selectivity and yield were determined by GC-MS analysis of the
crude reaction mixture. d Reaction carried out at 25 °C. e Reaction
carried out at 60 °C.
inorganic-ligand
supported
iron
catalyst
1,
(NH4)3[FeMo6O18(OH)6] (Fig. 1B), which possess an iron(III) ion
core and can be readily synthesized in one simple step in
aqueous solution at 100°C (see supporting information, Fig. S1
to S4), can efficiently catalyze the epoxidation of various
aromatic and aliphatic alkenes using 30% H2O2 as the sole
These results show that the additive clearly influences the
activity of the catalyst 1, and the NaHCO3 additive plays an important
2 | J. Name., 2012, 00, 1-3
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role in generating an efficient epoxidation species for the reaction of
Based on these experimental results and previous studies
View Article Online
26-28
cyclohexene with H2O2 catalyzed by 124,25. The influence of the related to biomimetic enzymes catalyst studies
, a tentative
DOI: 10.1039/C9DT02997D
catalyst loading and temperature on the product yield was also mechanism for the epoxidation reaction has been proposed (Fig. 2A).
investigated (entries 3-12). Increasing the amount of catalyst loading For the inorganic-ligand supported iron catalysts, the two oxidizing
had little effect on the product yield (entries 3, 13 and 14), thus equivalents required for oxidation are not stored only at the metal
demonstrating that altering the catalyst loading has little influence center but are delocalized on the six edge-sharing MO6 units instead.
on the conversion. Increasing or decreasing the temperature leads to Thus, the Fe-POM catalyst 1 first activates H2O2 to generate an active
a slight decrease in both the yield and selectivity of the product Fe(III)-OOH species A, which undergoes O-O bond heterolysis to give
(entries 15 and 16). It should be noted that in our control experiment, the highly reactive high-valence metal-oxo Fe(V)=O species B as the
when Fe2(SO4)3, Fe(NO3)3 or Na2MoO4 were used as a catalyst alone, active oxidant29.This may occur via an intramolecular Fe-O-Mo
respectively, no oxidation product was observed even in a prolonged charge transfer of the POM cluster. Such delocalization generates a
reaction
time
of
up
to
24h.
The
(NH4)6Mo7O24 potent oxidant that is suitable for attacking a variety of substrates, a
=(NH4)6[MoMo6O18(O)6] (also can be considered to be an isomerized common strategy in biocatalysis. The high-valence Fe-oxo species
Anderson-structured POM with an Mo core instead of Fe as the then reacts with cyclohexene to give the intermediate C with the
central atom), also cannot give the as-admired oxidation product. Fe(V)=O ferryl group attacking the C=C double of cyclohexene.
When the Fe core center of (NH4)3[FeMo6O18(OH)6] was replaced Finally, the intermediate C releases the product via an intramolecular
with other metals such as Co, Ni and Cu, the selectivity and yield oxygen-to-metal charge transfer from the POM to the Fe atom. An
would be dramatically deceased. These results strongly suggest that electron transferred from the inorganic ligand MoO6 unit to the
the central Fe core and inorganic ligand MoO6 units work in a central Fe atom through an intramolecular Fe-O-Mo bond.
synergic manner to boost the production in the present epoxidation
In support of the above mechanism for epoxidation with the Fe-
reaction.
POM catalyst 1, we carried out some control experiments using
Proposed mechanism
A
cyclohexene as a model substrate (Fig. 2B). When Fe-POM catalyst 1
was used stoichiometrically under inert atmosphere, trace of the
product was obtained, indicating that Fe-POM catalyst 1 was not as
the active species (Fig. 2B(a)). When 1.0 mmol Fe-POM catalyst
1reactedwith H2O2 in CH3CN at 50 oC for 8 hours, the B species
formed and the ESI-MS analysis showed m/z 1099.38 peaks
attributed to B, which may be POM-Fe=O (Fig. 2B(b) and Fig. S10-13).
Next, the combination of metal-oxo species B and a stoichiometric
cyclohexene under inert atmosphere was also tested, 98% yield of
cyclohexene oxide was obtained, thus confirming that metal-oxo
species B is the active catalyst. Moreover, a significant amount of
18O-incorporation from H218O2 into the cyclohexene oxide was
observed for the epoxidation of cyclohexene (∼30% based on 95%
18O-enriched H218O2). 1,2-Epoxycyclohexane was obtained in 92%
yield and with excellent selectivity (99) with a reaction time of 24h,
and with an 18O content of 95±1%. The 18O content in the product did
not change during the reaction, which shows that all the 18O atoms
incorporated into the alcohol originate from H2 18O2. (Fig. 2C)
POM-Fe3+
OH
Heterolysis
O
H2O2
H2O
A
O
POM-Fe3+
B
POM-Fe5+
O
Fe5+
O
POM
C
B
Control experiments
POM-Fe
Ar (1 atm)
NaHCO3 (0.1 eq.)
(a)
O
CH3CN (2 ml)
50 oC, 8 h
1.
(1.0 mmol)
yield: <5% (GC-Ms)
(
1.0 mmol)
NaHCO3 (0.1 eq.)
(b)
POM-Fe
H2O2
B
CH3CN (2 ml)
50 oC, 8 h
m/z=1099.38 (ESI-Ms,Figure S10-S13)
1.
(1.5 mmol)
(
1.0 mmol)
Inspired by this emergence of high-valence iron chemistry,
we sought to unveil similar inorganic-ligand supported iron
chemistry of FeV (Fig. S5). We initially hypothesized that a FeV
complex could be accessed via the 2e oxidation of the FeIII
starting material (NH4)3[FeMo6O18(OH)6]. This hypothesis was
based on literature investigations of the reactivity of FeIII and n
cyclic voltammogram studies carried out in our lab. As shown in
Fig.. S5a, the cyclic voltammogram of 1 in CH3CN shows two
oxidative waves at -0.23 V and +0.21 V versus Fc/Fc+ (Fc,
ferrocene). We assign these features to the FeIII/FeIV and the
FeIV/FeV couples, respectively. These waves are both
quasireversible and at relatively low potentials, suggesting that
NaHCO3 (0.1 eq.)
(c)
O
B
CH3CN (2 ml)
50 oC, 8 h
(1.0 mmol)
yield: 98% (GC-Ms)
C
18O labeling experiments
FeMo
(NH4)3[
6O18(OH)6](0.1mol %)
H
18O
2 (7.5 mmol 18O content: 95%)
30%
2
O18
NaHCO3 (0.1 eq.)
CH3CN(5 ml), 50 oC, 24 h
(5 mmol)
92% yield
99%selectivity
18O content: 95 1%
±
Fig. 2. A: Proposed mechanism for epoxidation of olefins
catalyzed by Fe-catalyst 1; B: Control experiments; C: 18O FeV could be accessible with this ligand system. Furthermore, as
labeling experiments.
shown in Fig. S5b, the different cyclic voltammograms of 1
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demonstrate that this FeV complex has excellent stability in the reaction of α-methyl styrene showed high yields and excellent
View Article Online
DOI: 10.1039/C9DT02997D
oxidation reaction.
chemo-selectivity (compounds 11), demonstrating the influence of
the steric hindrance around the active site of the catalyst. To our
delight, the epoxidation of a variety of substituted stilbene
derivatives, such as cis- and trans-stilbene, 1-phenylpropenes, and 1-
phenyl-2-methylpropenes, also proceeded in excellent yields to their
corresponding oxiranes (compounds 12-16). For the epoxidation of
cis- and trans-1,2-diphenylethene, the configurations around the
C=C bond were retained in the corresponding epoxides, thus
suggesting that free-radical intermediates are not involved in this
reaction. The epoxide products are commonly used as intermediates
for the synthesis of various biologically active natural products and
drug molecules, for example, the corresponding amino alcohols.
Table 2．Investigation of substrate scopes a.
1
R3
Cat. (0.1 % mol)
R4
O
R4
R2
R3
R1
NaHCO3 (0.1 eq.)
CH3CN, 50 o
H2O2
+
R1
R2
C
aryl alkenes
O
O
O
O
O
F
Cl
Cl
Cl
99%(92), 6h
(2)b
(4)
(5)
(6)
98%(85), 8h
(3)
99%(90), 5h
97%(88), 6h
99%(86), 5h
O
O
O
O
O
O
Br
(10)
91%(83), 8h
(7)
99%(90), 5h
(11)
92%(82), 9h
(8)
(9)
96%(81), 8h
95%(80), 8h
The high reactivity of the stilbene derivatives prompted us to
check our optimized method for the selective epoxidation of more
challenging linear and cyclic aliphatic alkenes. The selective
epoxidation of non-activated aliphatic alkenes proceeded smoothly
giving the corresponding products also in excellent yields
(compounds 17-21). A series of propylene derivatives bearing
acetate, hydroxyl, carbonyl, chloro, carboxyl, and ester groups at the
allylic positions, can be epoxidized chemo-selectively to afford the
corresponding 1,2-epoxides, a class of very important industrial
chemicals that are valuable for the preparation of cosmetics,
pharmaceuticals and polymer materials (compounds 22-28)30.
Furthermore, the more accessible, but less nucleophilic double
bonds in non-conjugated dienes, such as trans-1,4-hexadiene and 7-
methylocta-1,6-diene, were also epoxidized in high yields and in a
highly region-selective manner (compounds 29 and 30).
O
O
O
O
O
(14)
(15)
(16)
83%(75), 20h
95%(89), 12h
87%(77), 18h
(12)
98%(93), 9h
(13)
97%(82), 7h
alkyl alkenes
O
O
O
O
O
O
HO
AcO
OH
(21)
95%, 10h
(19)
(20)
(17)
(18)
90%, 12h
99%, 13h
97%, 14h
97%, 15h
O
O
O
O
O
Cl
(24)
94%, 12h
(22)
(23)
88%, 16h
(25)
96%, 15h
99%, 12h
(26)
95%,12h
OH
O
O
O
O
O
O
(27)
(29)
92%, 15h
98%, 12h
(28)
(30)
82%, 9h
93%, 12h
(31)
69%, 9h
Cyclic alkenes could also be efficiently and selectively
transformed into the corresponding epoxides in high yields
(compounds 31-43). Norbornene was exclusively oxidized with
excellent stereo-selectivity (compound 36). Epoxidation of
dicyclopentadiene gave the corresponding diepoxide in 94% yield
(compound 37). Epoxidation of (R)-1-methyl-4-(prop-1-en-2-yl)
cyclohex-1-ene proceeded region-selectively to give the 8,9-epoxide
in 90% yield without formation of the 1,2-epoxide (compound 41).
The epoxidation of 1,2- or 4-substituted cyclohexenes, such as 3-
aReaction conditions: Cat. 1 (0.1 mol %), olefins (1.0 mmol), H2O2
(1.5 equiv.), NaHCO3 (0.1 equiv.), CH3CN (2 mL). Unless otherwise
noted, yields were determined by GC-Ms analysis of the crude
b
reaction mixture, values in parentheses are the isolated yields.
cYields of isolated products.
The effect of the amount of H2O2 used on the conversion and
product selectivity was studied at various H2O2/substrate molar
ratios in the presence of 0.1 mol% catalyst 1 (Fig. S6). The selectivity
and yield changed with varying amounts of H2O2. The best yield and
selectivity was obtained using 1.5 equiv. H2O2; further increasing this
ratio significantly reduced the conversion and/or selectivity of the
reaction products.
methylcyclohex-1-ene,
1-methylcyclohex-1-ene,
1,4,4-
trimethylcyclohex-1-ene, cyclohex-2-en-1-ol and cyclohex-2-en-1-
one, showed unusual diastereo selectivity - the corresponding
epoxides are formed highly diastereo selectively with the oxirane
ring trans to the substituents (compound 38-40, 42 and 43). We also
studied the epoxidation of various olefins for the preparation of
natural products and drugs with biological activity, including
dihydropyrimidinones, inexpensive terpenes, and vitamin
derivatives, all proceeded to give the corresponding epoxides in good
yields of 86-96%. The corresponding epoxides were obtained without
affecting the parent structures (compounds 44-47). It is worth
mentioning that the substrates with double bonds give the
corresponding epoxides 46 and 47, demonstrating the method
possesses novelty regarding region-selectivity. Finally, in order to
confirm the further efficiency of the present system, a 20 mmol scale
epoxidation of cyclooctene was carried out. The epoxidation
Because the structure of the POMs is pH dependent, the
oxidation of cyclohexene was also run at different pH values. The
good yield and selectivity were obtained when the pH of the reaction
medium was above 5 and less than 9; further increasing or reducing
the pH out of this region significantly reduced both the conversion
and selectivity (Fig. S7) due to the increasing instability of the catalyst
1 both in strong acidic or basic solution.
With the optimal reaction conditions in hand, a structurally
diverse array of substituted aromatic olefins were subjected to
epoxidation. The corresponding products were obtained all in
excellent yields regardless of the electronic nature or the position of
substituents on the aromatic rings (compounds 2-10). Notably, the
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13. H. Yu, Y. Zhai, G. Dai, S. Ru, S. Han, Y. Wei, Chem. Eur. J. 2017,
proceeded efficiently with the corresponding epoxide being isolated
in 92% yield and with 99% selectivity (Scheme S1).
View Article Online
23, 13883-13887.
DOI: 10.1039/C9DT02997D
14. H. Yu, S. Ru, Y. Zhai, G. Dai, S. Han, Y. Wei, ChemCatChem.
2018, 10, 1253-1257.
15. J. Zhang, Y. Huang, J Hao, Y. Wei, Inorg. Chem. Front. 2017,
4, 1215-1218.
16. J. S. Anderson, Nature. 1937, 140, 850.
17. Jr. H. T. Evans, J. Am. Chem. Soc. 1948, 70, 1291-1292.
18. B. Hasenknopf, R. Delmont, P. Herson, P. Gouzerh, Eur. J.
Inorg. Chem. 2002, 5, 1081-1087.
19. P. Wu, P. Yin, J. Zhang, J. Hao, Z. Xiao, Y. Wei, Chem. Eur. J.
2011, 17, 12002-12005.
20. H. Ai, Y. Wang, B. Li, L. Wu, Eur. J. Inorg. Chem. 2014, 17,
2766-2772.
21. C. Lin, W. Chen, D. Long, L. Cronin, Y. Song, Dalton Trans.
2014, 43, 8587-8590.
22. A. Blazevic, A. Rompel, Coord. Chem. Rev. 2016, 307, 42-64.
23. H. Yu, S. Ru, G. Dai, Y. Zhai, H. Lin, S. Han, Y. Wei, Angew.
Chem. Int. Ed. 2017, 56, 3867-3871.
24. B. Lane, K. Burgess, J. Am. Chem. Soc. 2001, 123, 2933-2934.
25. B. Lane, M. Vogt, V. DeRose, K. Burgess, J. Am. Chem. Soc.
2002, 124, 11946-11954.
26. W. Nam, Y. Lee, S. Fukuzumi, Acc. Chem. Res. 2014, 47, 1146-
1154.
Conclusions
In summary, we have disclosed a catalytic aerobic
epoxidation of olefins with an inorganic-ligand supported non-
precious metal catalyst using 30% H2O2 as the oxidant.31 No
extra reducing agents or radical initiators are required in this
protocol. The catalyst (NH4)3[FeMo6O18(OH)6] can be readily
prepared in high yield using a one step process in water at 100°C
and can catalyze the epoxidation of various aromatic and
aliphatic alkenes into the corresponding epoxides with excellent
yields and chemo- and stereo-selectivity. This iron catalyst
exhibits high catalytic activity as well as excellent stability.
Moreover, this reaction is simple to be operated, and avoids the
use of expensive and toxic precious metals, and does not
require the use of air/moisture sensitive and commercially
unavailable organic ligands or tungsten-based POMs. Extension
of this methodology to other catalytic reactions is currently
ongoing in our laboratory. The generality of this methodology
gives it a potential to be used on an industrial scale in the future.
27. Z. Chen, G. Yin, Chem. Soc. Rev. 2015, 44, 1083-1100.
28. H. Neu, R. Baglia, D. Goldberg, Acc. Chem. Res. 2015, 48,
2754-2764.
29. V. Srivastava, A. Negi, J. Kumar, M. Gupta, P. Khanuja, Bioorg.
Med. Chem. 2005, 13, 5892-5908.
30. S. Oyama, X. Zhang, J. Lu, Y. Gu, T. Fujitani, J. Catal. 2008, 257,
1-4.
31. D. Dutta, A. D. Jana, M. Debnath, A. Bhaumik, J. Marek, M.
Ali, Dalton Trans. 2010, 39, 11551-11559.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Nos. 21471087, 21631007, 91022010,
21225103 and 21221062), Doctoral Fund of Ministry of
Education of China and Tsinghua University Initiative
Foundation Research Program No. 20131089204, and the State
Key Laboratory of Natural and Biomimetic Drugs K20160202.
Notes and references
1. Jr. L. Que, W. B. Tolman, Nature 2008, 455, 333-340.
2. G. Olivo, O. Cussó, M. Borrell, M. Costas, J. Biol. Inorg. Chem.
2017, 22, 425-452.
3. I. Bauer, H. J. Knölker, Chem. Rev. 2015, 115, 3170-3387.
4. S. Enthaler, K. Junge, M. Beller, Angew. Chem. Int. Ed. 2008,
47, 3317-3321.
5. W. Oloo, Jr. L. Que, Acc. Chem. Res. 2015, 48, 2612-2621.
6. M. T. Pope, A. Müller, Angew. Chem. Int. Ed. 1991, 30, 34-48.
7. J. Rhule, C. Hill, D. Judd, Chem. Rev. 1998, 98, 327-358.
8. N. Mizuno, K. Kamata, Coord. Chem. Rev. 2011, 255, 2358-
2370.
9. K. Kamata, K. Yonehara, Y. Sumida, K. Yamaguchi, S. Hikichi,
N. Mizuno, Science. 2003, 300, 964-966.
10. Z. Xi, N. Zhou, Y. Sun, K. Li, Science. 2001, 292, 1139-1141.
11. R. Neumann, M. Dahan, Nature. 1997, 388, 353-355.
12. Q. Li, Y. Wei, J. Hao, Y. Zhu, L. Wang, J. Am. Chem. Soc. 2007,
129, 5810-5811.
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DOI: 10.1039/C9DT02997D
3-(NH4)3
O
O
O
O
O
Mo
Mo
O
O
O
O
O
O
O
O
Fe
Mo
Mo
O
O
O
O
O
O
O
Mo
O
Mo
O
O
O
(
6O18 OH)6]
1:
FeMo
(NH4)3[
1
Cat. (0.1 % mol)
NaHCO3 (0.1 eq.)
H2O2 (1.5 eq.)
R3
R1
R4
R2
O
R3
R1
R4
R2
31 examples
up to 99% yield
up to 99% selectivity
CH3CN, 50 o
C
R1, R2, R3, R1= H, alkyl or aryl
An inorganic ligand supported iron catalyst which can effectively catalyze olefin epoxidation
with excellent yields.