Chiral salen Mn (III) immobilized on ZnPS-PVPA through alkoxyl-triazole for superior performance catalyst in asymmetric epoxidation of unfunctionalized olefins

Article abstract of DOI:10.1016/j.jorganchem.2019.02.008

Chiral salen Mn (III) catalysts anchored onto ZnPS-PVPA via click chemistry are prepared and applied in asymmetric epoxidations of unfunctionalized olefins. Superior catalytic performances (conv%, up to >99; ee%, up to >99) are achieved in the epoxidations of α-methylstyrene, styrene, indene and 1-octene. According to 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethylchromene, configuration of epoxides are reversed. And then the catalysts are selective in not only oxidative systems, but also substrates. Moreover, superior reusability (yield, 82%; ee, 86%) after recycling for nine times could also be obtained, which provide the potential application in industry.

Full text of DOI:10.1016/j.jorganchem.2019.02.008

Accepted Manuscript
Chiral salen Mn (III) immobilized on ZnPS-PVPA through alkoxyl-triazole for superior
performance catalyst in asymmetric epoxidation of unfunctionalized olefins
Jing Huang, Sirui Liu, Yan Ma, Jiali Cai
PII:
S0022-328X(19)30045-2
DOI:
https://doi.org/10.1016/j.jorganchem.2019.02.008
JOM 20710
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 2 December 2018
Revised Date: 28 January 2019
Accepted Date: 5 February 2019
Please cite this article as: J. Huang, S. Liu, Y. Ma, J. Cai, Chiral salen Mn (III) immobilized on
ZnPS-PVPA through alkoxyl-triazole for superior performance catalyst in asymmetric epoxidation of
unfunctionalized olefins, Journal of Organometallic Chemistry (2019), doi: https://doi.org/10.1016/
j.jorganchem.2019.02.008.
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ACCEPTED MANUSCRIPT
Chiral salen Mn (III) immobilized on ZnPS-PVPA through alkoxyl-triazole for superior
performance catalyst in asymmetric epoxidation of unfunctionalized olefins
Jing Huang a,b*, Sirui Liua, Yan Maa, Jiali Caic*
a
College of Biotechnology, Southwest University, Chongqing 400715, PR China. E-mail:
hj41012@163.com;
b Institute for Clean Energy & Advanced Materials, Southwest University, Chongqing 400715, PR
China.
c College of Rongchang, Southwest University, Chongqing 402460, PR China.
*Corresponding author: Dr. Jing Huang
E-mail: hj41012@163.com; Tel: +86 2368250191; fax: +86 2368251128
Abstract: Chiral salen Mn (III) catalysts anchored onto ZnPS-PVPA via click chemistry are
prepared and applied in asymmetric epoxidations of unfunctionalized olefins. Superior catalytic
performances (conv%, up to >99; ee%, up to >99) are achieved in the epoxidations of
α-methylstyrene, styrene, indene and 1-octene. According to 6-cyano-2,2-dimethylchromene and
6-nitro-2,2-dimethylchromene, configuration of epoxides are reversed. And then the catalysts are
selective in not only oxidative systems, but also substrates. Moreover, superior reusability (yield,
82%; ee, 86%) after recycling for nine times could also be obtained, which provide the potential
application in industry.
Keywords: Chiral Mn (III) salen; heterogeneous catalyst; asymmetric epoxidation; click
chemistry
1. Introduction
Epoxides are validated as being important synthons in the industrial application of several
commodity compounds, as well as in the preparation of many intermediates, fine chemicals, and
pharmaceuticals by virtue of their chemical versatility and reactivity [1-6]. Chiral salen Mn (III)

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complexes are more suitable for the epoxidation of olefins since they are attractive redox active
systems and demonstrate a high catalytic activity and selectivity [7-11]. Although homogenous
catalysts show high activity in the epoxidation of olefins, they often suffer from difficulty in
recovery and reusability. To overcome these problems, considerable efforts have been devoted to
immobilize these complexes on various supports such as zeolites, silica, organic polymers, clays,
magnetic nanoparticles, ion-exchange resins and carbon nanotubes. Some chiral salen based Mn
(III) complex heterogenized on silica matrix exhibit a relatively high enantioselectivity for
epoxidation reaction and asymmetric borohydride reduction of ketones [12-20].
In recent decades, the development of sustainable oxidative procedures on the basis of solid
catalysts is aiming at reducing the environmental impact of the epoxidation reaction. Extensive
studies have revealed the high catalytic activity of various supported catalysts in a number of
oxidation reactions. Resins, organic gels, and fibres are the polymeric organic materials which act
as the conventional support for the immobilization of enzymes. But they create problem in
disposal and show low reusability. On the other hand, inorganic supports such as porous silica gels
are environmentally more acceptable, structurally more stable, and also chemically more resistant
to organic solvents and microbial attacks over the organic supports. By the incorporation of
organic ligand in the pores of the silica wall an organic-inorganic hybrid is formed which make the
materials hydrothermally stable and hydrophobic and higher catalytic efficient during applications
for organic process. These kinds of applications of these materials in reaction condition provides a
synergistic means of an efficient approach of the reactants to metal sites, and suitable
mesochannels to drive out the products for next recycles [21-25]. However, the catalytic activity
of some of these heterogeneous catalysts decreases upon immobilization due to the reduction in

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accessibility of active sites [26-28]. Our group has also reported a series of superior Jacobsen’s
catalysts with hybrid materials as the supports in asymmetric epoxidation of unfunctionalized
olefins, such as zirconium oligo-styrenylphosphonate-phosphate (ZSPP) and zirconium poly
(styrene-phenylvinylphosphonate)-phosphate (ZPS-PVPA) and zinc poly (styrene-phenylvinyl-
phosphonate)-phosphate (ZnPS-PVPA) as well as calcium poly (styrene-phenylvinylphos-
phonate)-phosphate (CaPS- PVPA) [29-32].
In this study, we have been initiated to design chiral Jacobsen’s catalysts immobilized on
ZnPS-PVPA through alkoxyl-triazole (Scheme 1-2) for asymmetric epoxidation of
unfunctionalized olefins. In addition, we also attempt to appraise the catalytic properties and to
investigate the mechanisms as well as to explore the reusability.
Scheme 1. Synthetic route of the heterogeneous catalysts

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Br
RH2, THF
Na
N3
Br
Br
NaN3
N
N
N
CuSO4, VcNa
7
8
N
N
Mn
R
salen Mn(III)Cl
THF, Na
RH
N
t-Bu
O
O
t-Bu
N
N
t-Bu
t-Bu
N
N
N
R = -O(CH2)6O-
10
9
Scheme 2. The synthesis of homogeneous catalysts 10
As described in Fig. S1, both the catalysts 6a-d and Jacobsen’s catalyst have
displayed the same bands at 1620 cm−1 by virtue of the azomethene (C=N) stretching band.
The bands at 523 cm−1 are due to the stretching vibration of Mn-O. The bands in the scope
of 1345-1460 cm−1 for the catalysts are ascribed to the stretching vibration of C-H groups.
2-
The common prominent bands at 1145, 1089, and 986 cm-1 are attributed to R-PO3
phosphonate stretching vibrations. The phosphonate and phosphate stretching vibrations
are conductive to the adsorptions at 1200, 1145, and 1080 cm-1. Apart from this, the bands
at the hand of 1279 cm-1 refer to the vibration of triazole ring in the catalysts 6a
-d. On
account of this, the immobilization of Jacobsen’s catalyst onto alkoxyl-modified
ZnPS-PVPA has been confirmed successfully.
Based on the TG curves (Fig. S2), the initial weight loss is 2.5% below 200 ℃, by virtue of
surface-bound or intercalated water in this stage. And further decomposition of organic moieties
contribute to 62.9% weight loss in the range of 200-550 ℃. Finally, the small weight losses

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within the limits of 550-1000 ℃ are ascribed to exothermal transition. Therefore, the catalyst 6d
still remains superior thermal stability near 180 ℃.
In Fig. S3, the XRD patterns of ZnPS-PVPA indicate that a broad 001 peak (the lowest-angle
diffraction peak in the pattern) at the vicinity of 24.8º is attributed to the parts of inorganic
phosphate (ZnNaPO4) in ZnPS-PVPA, and that other peaks at higher-order 00n peaks such as at
38.04º is ascribed to organic compositions in the catalysts. Although the intensities of all peaks for
the catalyst 6d have weakened by virtue of the immobilization of Jacobsen’s catalyst, the
reflections also reveal that the mesoporous structure of ZnPS-PVPA still has been preserved.
Simultaneously, the interlayer distance which could be calculated (via the Bragg equation, nλ = 2d
sinθ) of the catalyst 6d (43.7 ± 0.1 Å) is nearly twice as much as that of ZnPS-PVPA (21± 1.3 Å).
On account of this, it could be deduced that the augment of interlayer for the zinc layer is
attributed to the introduction of chiral salen Mn (III) in ZnPS-PVPA, which is in contrast to the
most of the results reported [29-30].
Fig. 1 The nitrogen adsorption-desorption isotherm and pore distribution of the catalyst 6d
On account of the desorption isotherms (Fig. 1), the nitrogen adsorption-desorption
isotherms belong to characteristic type V along with a sharp increase in N2 adsorption at higher

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P/P0 values (~0.9) and a distinct hysteresis loop (type H3). Desorption isotherm is below
adsorption isotherm, accompanying with an almost parallel adsorption and desorption. The pore
diameters of the particles mainly vary from 2 nm to 12 nm, which is within the scope of
mesoporous. And few particles are over 12 nm and less than 2 nm in diameter.
The corresponding textural parameters calculated by N2 adsorption-desorption isotherms are
presented in Table 1.
Table 1 Physiochemical characterization data of 1-6
Surface
area (m2/g)
4.9
Pore volum
(×10-2 cm3/g)
1.3
Average pore Mn content
Sample
diameter (nm)
3.5
(mmol/g)
1
2
-
-
36.9
18.82
10.21
12.78
14.63
1.85
4
38.7
20.15
-
5
42.6
23.57
-
6a
6b
6c
6d
6a
10.26
5.72
5.86
5.91
0.76
6b
11.57
1.92
6c
12.31
2.03
14.18
2.16
6.09
ZnPS-PVPA could offer sufficient space to contain the solvated chiral Mn (III) salen
complex on account of the textural parameters in Table 1 (1 vs Jacobsen’s: 3.5 vs 2.05-1.06 nm).
Meanwhile, the physiochemical characterization data will be pulled out in two stages from ZnPS-
PVPA to the catalyst: the first stage means that the textural parameters are on the increase through
the chloromethylation and click chemistry as well as the alkoxylation, such as in BET surface area
(1 vs 2 vs 4 vs 5, 4.9 vs 36.9 vs 38.7 vs 42.6 m2/g), and in the pore volume (1 vs 2 vs 4 vs 5, 1.3 vs
18.82 vs 20.15 vs 23.57 ×10-2 cm3/g) as well as in average pore diameter (1 vs 2 vs 4 vs 5, 3.5 vs
10.21 vs 12.78 vs 14.63 nm). This fact demonstrates that the effect on the textural parameters from
the augment of the interlayer distance is stronger than the introduction of chloromethyl and

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triazolyl as well as alkoxy. On the contrary, the second stage refers to that the textural parameters
begins to decrease by chance as a result of the immobilization of chiral salen Mn (III) on
ZnPS-PVPA, for instance in BET surface area (5 vs 6d, 42.6 vs 14.18 m2/g), and in the pore
volume (5 vs 6d, 23.57 vs 2.16 ×10-2 cm3/g) as well as in average pore diameter (5 vs 6d, 14.63 vs
6.09 nm), which is inconsistent with the results reported [29-30]. The introduction of sterically
bulky salen Mn(III) in ZnPS-PVPA may aid in the occupation of some caves and holes as well as
channels, which bring about the decrease of structure parameters.
The heterogeneous catalyst 6d reveals a Mn 2p3/2 core level peak at 642.6 eV (Fig. S4),
which consists with the earlier literature data [33]. In comparison with the binding energy of 642.1
eV for neat chiral salen Mn(III) complex, the increase of 0.5 eV in chemical shift for the catalyst
6d is attributed to the diverse coordination microenvironment of Mn inside the configuration of
the catalyst 6d.
Fig. 2 SEM images of (a) ZnPS-PVPA and (b) the catalyst 6d
SEM images indicate that the surface morphology transform from a smooth anomalous
structure (ZnPS-PVPA, Fig. 2a) to a loose amorphous configuration (the catalyst 6d, Fig. 2b) by
virtue of the immobilization of Jacobsen’s catalyst. In view of the configuration of the catalyst 6d,
there are many small caves and irregular channels, which would lead to the increase in surface

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area of the catalyst (6d vs ZnPS-PVPA, 28.02 vs 4.9 m2/g) and further help the substrates to easily
get closer with the catalytic sites.
Fig. 3 TEM images of (a) ZnPS-PVPA and (b) the catalyst 6d
TEM images of ZnPS-PVPA (Fig. 3a) reveals the spheroid structure with the sizes of the
particle within the limits of 70-80 nm. On account of the catalyst 6d (Fig. 3b), the configuration is
loose, and the channels, holes, cavums also exist. Based on this, the substrates are provided with
more chance to approach the internal catalytic active sites and further symmetric epoxidation of
unfunctionalized olefins could be carried out in sufficient space.
Table 2 Asymmetric epoxidation of alkenes catalyzed by 6a-d and 10
Oxidant
system
Time Conv. eee
(h) (%) (%)
TOFf
×10-4(s-1)
54.42
43.87
44.98
51.64
55.53
28.35
54.99
54.99
19.80
53.34
Entry Substratea Catalyst
1
2
A
A
A
A
A
A
A
A
A
A
Jacobsen’s
m-CPBA/NMOb
1
1
1
1
1
1
1
1
1
1
98 54
79 82
81 86
93 95
6a
6b
6c
6d
6d
1
m-CPBA
3
m-CPBA
4
m-CPBA
5
m-CPBA
>99
8
>99
51
6
m-CPBA/NMO
m-CPBA
7
>99
0
8
5d
10
10
m-CPBA
>99 26
36 72
97 91
9
m-CPBA/NMO
m-CPBA
10
11
B
Jacobsen’s NaClO/PPNOc
24 >99 65
2.31

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12
13
14
15
16
17
18
B
B
B
B
B
B
B
6a
6b
6c
6d
6d
10
10
NaClO/PPNO
NaClO/PPNO
NaClO/PPNO
NaClO/PPNO
NaClO
24
24
24
84 73
86 85
95 89
1.94
1.99
2.19
2.31
1.46
2.03
1.82
24 >99 >99
24
24
24
63 75
88 93
79 68
NaClO/PPNO
NaClO
19
20
21
22
23
24
25
26
B
B
B
B
B
B
B
B
Jacobsen’s NaIO4/imidazoled
5
5
5
5
5
5
5
5
>99 69
>99 >99
>99 >99
>99 >99
>99 >99
>99 >99
88 84
11.11
11.11
11.11
11.11
11.11
11.11
9.78
6a
6b
6c
6d
6d
10
10
NaIO4/imidazole
NaIO4/imidazole
NaIO4/imidazole
NaIO4/imidazole
NaIO4
NaIO4/imidazole
NaIO4
82 80
9.11
27
28
29
30
31
32
B
B
B
B
B
B
Jacobsen’s m-CPBA/NMO
1
1
1
1
1
1
>99 54
84 72
88 81
93 86
>99 >99
62 20
54.99
46.19
48.39
51.14
54.99
34.09
6a
6b
6c
6d
6d
m-CPBA
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
33
34
35
36
37
38
C
C
C
C
C
C
Jacobsen’s m-CPBA/NMO
1
1
1
1
1
1
98 47
81 52
86 58
93 67
>99 74
54.44
44.54
47.29
51.14
54.99
54.99
6a
6b
6c
6d
6d
m-CPBA
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
>99
6
39
40
41
42
43
44
D
D
D
D
D
D
Jacobsen’s m-CPBA/NMO
1
1
1
1
1
1
90 40
82 61
85 69
92 73
>99 83
50.00
45.09
46.74
50.59
54.99
54.99
6a
6b
6c
6d
6d
m-CPBA
m-CPBA
m-CPBA
m-CPBA
m-CPBA/NMO
>99
8
a A = indene, B = α-methylstyrene, C = styrene, D = 1-octene.
b Reactions were carried out in CH2Cl2 (4 mL) with alkene (1 mmol), n-nonane (internal standard, 1 mmol), NMO
(5 mmol), homogeneous (5% mmol) or heterogeneous salen Mn (III) catalysts (5% mmol) and m-CPBA (2
mmol) at 0℃ for 1 h. The conversions and the ee values were determined by GC with chiral capillary columns
HP19091G-B 213, 30 m×0.32 mm×0.25 µm.
c Reactions were carried out in CH2Cl2 (2 mL) with alkene (0.5 mmol), n-nonane (internal standard, 89.3 µL, 0.5
mmol), PPNO (0.25 mmol) and NaClO (pH 11.3, 0.55 M, 1,25 mL) at 25℃ for 24 h.

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d
Reactions conditions: alkene (1 mmol), n-nonane (internal standard, 1 mmol), NaIO4 (2 mmol), catalyst
(0.03mmol), CH3CN/H2O (10 mL/5 mL) at 25℃ for 5 h.
e (S)-form.
f Turnover frequency (TOF) is calculated by the expression of [product]/[catalyst] × time (s−1).
As for
m-CPBA/NMO, ZnPS-PVPA and the alkoxyl-modified ZnPS-PVPA 5d are
employed to catalyze asymmetric epoxidation of indene by way of investigating the chiral
induction of the support and the linker (Table 2). Low olefin enantio excesses are achieved
(ee%: ZnPS-PVPA vs 5d, 0 vs 26; entry 7 vs 8), which reveals that both ZnPS-PVPA and
the alkoxyl-modified ZnPS-PVPA 5d are stereochemically inactive for the epoxidation of
olefins. On account of the results reported, it could be deduced that the lower activity is
ascribed to the absence of active catalysts on the exterior surface and a lack of any active
solution species [10]. Simultaneously, ee values vary from 54% to 91% (Jacobsen’s vs 10
,
entry 1 vs 10) owing to the alkoxylation and the introduction of 1,2,3-triazole, and further
reach >99% (6d vs 10, entry 10 vs 5) by virtue of anchoring onto ZnPS-PVPA. Based on
this, the synergistic effect originating from ZnPS-PVPA and the linkage alkoxyl-triazole as
well as chiral salen Mn center contributes to the chirality of products.
According to NaClO/PPNO, the catalytic properties of the supported catalysts 6a-d
are superior to Jacobsen’s catalyst (conv%, 84 - >99 vs >99; ee%, 73 - >99 vs 65; entry
12-15 vs entry 11). Moreover, the catalytic performance of homogeneous catalyst 10 have
climbed to (conv%, 88; ee%, 93; entry 19) according to Jacobsen’s catalyst (conv%, >99;
ee%, 65; entry 11) due to the import of alkoxy and 1,2,3-triazole, and ultimately runs up to
(conv%, >99; ee%, >99; entry 15) owing to the immobilization. This means that the
coordination of ZnPS-PVPA, the linker including alkoxy and 1,2,3-triazole, and the chiral

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ligand acts on superior performance, which reveals that the appropriate conformation
makes for the enantioselective oxygen transferring towards some substrates[33-35].
In view of NaIO4/imidazole, no matter conversions or enantioselectivities according
to the catalysts 6a-d all exceed 99%. Notably, ee values run up to 84% (the catalyst 10
,
entry 25) in contrast to 69% (Jacobsen’s catalyst, entry 19) via alkoxy and 1,2,3-triazole,
and at length attain >99% (6d, entry 23) as a result of anchoring onto ZnPS-PVPA. On
account of this, it could be deduced that the catalytic properties are similarly ascribed to
congenerous effect originating from ZnPS-PVPA and the linker as well as the chiral
ligand.
Without the addition of NMO, ee value varies from 8% to >99%, conversion from 51%
to >99% in the epoxidation of indene (entry 6 vs entry 5); ee from 20% to >99%,
conversion from 62% to >99% in the epoxidation of α-methylstyrene (entry 32 vs 31); ee
from 6% to 74% in the epoxidation of styrene (entry 38 vs 37); ee from 8% to 83% in the
epoxidation of 1-octene (entry 44 vs 43). The similar appearance also happens to
homogeneous catalyst 10 (conv%, 36 vs 97; ee%, 72 vs 91; entry 9 vs 10) according to the
epoxidation of indene. Namely, the addition of NMO to the reaction does not improve the
chiral induction, but results in the decrease of the catalytic activity, which is adverse to the
articles reported [29-30]. The framework of NMO is six-membered nitrogen and oxygen
heterocycle with lone-pair electron, which is similar to that of 1,2,3-triazole involving
five-membered nitrogen heterocycle with lone pair electrons. Evidently, NMO displays
identical steric effect and electronic structure to 1,2,3-triazole. In the presence of NMO, the
steric hindrance from 1,2,3-triazole impels the optimal geometric configuration of the

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reactive intermediates salen Mn(V)=O or their transition states altered, followed by the
lower ee values.
No matter imidazole is added or not, ee values and conversions still reach >99% in the
epoxidation of α-methylstyrene (entry 23 vs 24). As for the homogeneous catalyst, the
performance increases a little in the presence of imidazole such as catalyst 10 (conv%, 88
vs 82; ee%, 84 vs 80; entry 25 vs 26). Imidazole is five membered nitrogen heterocycle
with lone-pair electron, which is similar to the configuration of 1,2,3-triazole group.
Distinctly, imidazole indicates slightly weak electronic effect and similar steric effect to
1,2,3-triazole group. Accordingly, the role of imidazole as the additive to oxidation system
NaIO4/imidazole may be substituted by 1,2,3-triazole group in the heterogeneous catalyst
and further superior performance could still be indicated with the addition of imidazole or
not.
The addition of PPNO could still be conductive to the reinforcement of the catalytic
properties (conv%, >99 vs 63; ee%, >99 vs 75, entry 15 vs 16), which agree with the
articles reported [29-30, 36]. The similar phenomenon has occurred to the homogeneous
catalyst 10 (conv%, 88 vs 79; ee%, 93 vs 68; entry 17 vs 18). In this context, PPNO not
only could heighten the stability of the catalyst through coordinating with salen Mn (
Ⅲ),
but also could accelerate the speed of epoxidation in the way of transferring active
ingredient HClO from aqueous phase to organic phase[37]. Apart from this, PPNO consists
of benzene ring connected to pyridine ring, which owns nitrogen and oxygen atoms with
lone-pair electron. On account of the whole effect from spatial orientation and the electron,
PPNO is evidently stronger than 1,2,3-triazole group and further the role of PPNO could

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not be replaced by 1,2,3-triazole in reaction. In a word, superior performance could be
obtained only when PPNO is added to the reaction system.
As for m-CPBA/NMO, ee values increase from 82% to 98%, conversions from 79% to >99%
(entry 2-5) with the increase of chain length in asymmetric epoxidation of indene, which agree
with the results reported by C. Li [36] and our group [30]. According to NaClO/PPNO, the
catalytic performance also increase with the length of the linker in the epoxidation of
α-methylstyrene (conv%, from 84 to >99; ee%, from 73 to >99; entry 12-15). This phenomenon
could be interpreted that the heterogeneous salen Mn (III) catalysts may approach the active
intermediates of salen Mn (V) or their transition states more easily owing to the elongation of
chain length. While for NaIO4/imidazole, the impacts originating from the chain length do not
emerge. Both the conversions and enantioselectivities (entry 20-23) do not change with the
increase of chain length and go beyond >99%, which demonstrates that superior oxidability of
NaIO4 hush up the effect of the chain length.
Table 3 Asymmetric epoxidation of 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethylchromenea catalyzed
by 6a-d
TOFd× 10-4(S-1)
Entry
Catalyst
Substrateb
Time (h)
Conv(%)
ee (%)c
1
2
3
4
5
Jacobsen’s
D
D
D
D
D
6
60
68
76
85
98
91(3R, 4R)
63(3S, 4S)
72(3S, 4S)
78(3S, 4S)
87(3S, 4S)
5.56
1.55
1.75
1.96
2.26
6a
6b
6c
6d
24
24
24
24
6
7
Jacobsen’s
E
E
E
E
E
6
68
71
78
89
97
90(3R, 4R)
69(3S, 4S)
72(3S, 4S)
79(3S, 4S)
85(3S, 4S)
6.30
1.64
1.80
2.06
2.24
6a
6b
6c
6d
24
24
24
24
8
9
10
a
Reactions were carried out in CH2Cl2 (1 mL) with alkene (0.25 mmol), n-nonane (internal standard, 1 mmol),
PPNO (0.05 mmol), homogeneous 5% mmol) or heterogeneous salen Mn(III) catalysts (5% mmol) and NaOCl

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(0.5 mmol).
b D = 6-cyano-2,2-dimethylchromene, E = 6-nitro-2,2-dimethylchromene
c Chiral HPLC OD column.
d Same as in Table 2.
In Table 3, the catalyst 6a-d indicate higher catalytic performance than Jacobsen’s catalyst in
the epoxidation of 6-cyano-2,2-dimethylchromene (conv%, 68-98 vs 60; ee%, 63-87 vs 91; entry
2-5 vs 1) and 6-nitro-2,2-dimethyl-chromene (conv%, 71-97 vs 68; ee%, 69-85 vs 90; entry 7-10
vs 6). Moreover, the catalytic properties have also been boosted with the increase of chain length.
For example, conversions increase from 68% to 98%, ee values from 63% to 87% in the
epoxidation of 6-cyano-2,2-dimethylchromene (entry 2-5); conversions from 71% to 97%, ee
values from 69% to 85% in the epoxidation of 6-nitro-2,2-dimethyl-chromene (entry 7-10).
On the other hand, the steric configuration of the epoxides (3S, 4S) catalyzed by 6a-d is
obviously reversed in comparison with Jacobsen’s catalyst (3R, 4R), which has been reported
before [38]. As a matter of fact, the result is not only attributed to the linker, the support and the
chiral ligand, but also related to the confinement effect deriving from the nanopores of the
catalysts and the corresponding microenvironment. In this context, the interaction between the
reactants and the products could hold back the reactants approaching the active site and further
confine the rotation of the intermediates salen Mn(V)=O or transition states of the epoxidation
[32,36], which finally affect the steric structure of the epoxides. Apart from this, the results in
Table 2 reveal the same architecture of epoxides, which demonstrates that similar reaction
mechanism process is carried out in asymmetric epoxidations of α-methylstyrene, indene, styrene
and 1-octene. While for the epoxidation of 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-
dimethylchromene, the spatial framework of epoxides (3S, 4S) are turned according to Jacobsen’s

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catalyst (3R, 4R), which confirms that the reagents assault or the groups leave in antipodal
direction and then the reversal epoxides are formed. In brief, the survey also illustrates that the
catalyst is selective about the substrates in asymmetric epoxidation of unfunctionalized olefins.
Fig. 4 The recycles of catalyst 6d in the epoxidation of α-methylstyrene
After nine consecutive times (Fig. 4), the catalytic performance reveals only a slightly
decrease (conv%: from >99 to 82; ee%: from excess >99 to 86), which is still comparable to
Jacobsen’s catalyst (ee%, 54). The effective separation the chiral Mn (III) salen complexes by
ZnPS-PVPA is conductive to the superior stability of the catalyst in case that they would dimerize
to inactive µ-oxo-Mn (IV) species. Simultaneously, the decrease of properties could be mainly
attributed to several factors, such as the decomposition of the catalysts under epoxidation
conditions [32]; the desquamation of salen Mn (III) from ZnPS-PVPA as a result of stirring; the
blockage of some pores and channels from byproduct in reaction. Apart from this, the Mn content
of the catalyst 6d (0.45 mmol/g) slightly decreases after recycling for nine times, compared with
the fresh catalyst (around 0.76 mmol/g).
In summary, we have explored a series of Jacobsen’s catalyst anchored onto ZnPS-PVPA

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through alkoxy and 1,2,3-triazole. The superior catalytic performance in asymmetric epoxidation
of unfunctionalized olefins (conv%, up to 99; ee%, up to 99) is due to the synergistic effect
originating from ZnPS-PVPA and the linkage as well as chiral salen Mn (III) ligand. Moreover,
the heterogeneous catalysts could still maintain comparable properties after recycling for nine
times, which paves the way for the potential application in industry.
Acknowledgement
We gratefully acknowledge to the financial support from Faculty of Materials and Energy and
Institute for Clean Energy & Advanced Materials, Southwest University and Chongqing Key
Laboratory for Advanced Materials and Technologies of Clean Electrical Power Sources and the
Fundamental Research Funds for the Central Universities (XDJK2013C120) and the Ministry of
Education Chunhui Project (Z2016161) and the Recruitment Program of Southwest University
(SWU117023).
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Figures captions:
Scheme 1 Synthetic route of the heterogeneous catalysts
Scheme 2 The synthesis of homogeneous catalysts 10
Fig 1 The nitrogen adsorption-desorption isotherm and pore distribution of the catalyst 6d
Fig 2 SEM images of (a) ZnPS-PVPA and (b) the catalyst 6d
Fig 3 TEM images of (a) ZnPS-PVPA and (b) the catalyst 6d
Fig 4 The recycles of catalyst 6d in the epoxidation of α-methylstyrene
Tables captions:
Table 1 Physiochemical characterization data of 1, 2 and 6d
Table 2 Asymmetric epoxidation of alkenes catalyzed by 6a-d and 10
Table 3 Asymmetric epoxidation of 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethyl-
chromenea catalyzed by 6a-d

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Highlights
Chiral salen Mn (III) immobilized on ZnPS-PVPA through
alkoxyl-triazole for superior performance catalyst in asymmetric
epoxidation of unfunctionalized olefins
Jing Huang*, Sirui Liu, Yan Ma, Jiali Cai*
‹
‹
The chiral salen Mn(III) have been immobilized on alkoxyl-modified ZnPS-PVPA.
The supported catalysts indicate the selectivity of oxidants and the substrates.
‹
‹
The catalysts could recycle for nine times without significant loss of activity.
The catalysts could be used in large-scale reactions with superior performance.