Layered zinc and lanthanum hydroxide nitrates hosting chiral sulphonato-(salen)manganese(III) complex catalyzed asymmetric epoxidation reactions

Article abstract of DOI:10.1016/j.catcom.2013.07.028

Layered zinc and lanthanum hydroxide nitrates were first applied as two ion-exchangeable supports for immobilizing a chiral sulphonato-(salen) manganese(III) complex, and the resulted catalysts were characterized by FT-IR, elemental analysis, ICP-AES, TGA, conductivity, XRD, nitrogen physisorption, along with aqueous particle size and zeta potential. Heterogeneous catalysts showed moderate to good conversions and excellent enantioselectivities in epoxidation of styrene and α-methylstyrene when iodosylbenzene was employed as terminal oxidant. Furthermore, the superiority came from heterogeneity, and only filtration could lead to an effective separation of catalyst from product solution.

Full text of DOI:10.1016/j.catcom.2013.07.028

Layered zinc and lanthanum hydroxide nitrates hosting chiral sulphonato-
salen)manganese(III) complex catalyzed asymmetric epoxidation reactions
(
Xiaoyong Li, Qinchao Shen, Guangbin Zhang, Donghua Zhang, Aqun
Zheng, Fang Guan, Yang Sun
PII:
DOI:
Reference:
S1566-7367(13)00282-3
doi: 10.1016/j.catcom.2013.07.028
CATCOM 3588
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
13 June 2013
2 July 2013
13 July 2013
Please cite this article as: Xiaoyong Li, Qinchao Shen, Guangbin Zhang, Donghua Zhang,
Aqun Zheng, Fang Guan, Yang Sun, Layered zinc and lanthanum hydroxide nitrates host-
ing chiral sulphonato-(salen)manganese(III) complex catalyzed asymmetric epoxidation
reactions, Catalysis Communications (2013), doi: 10.1016/j.catcom.2013.07.028
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ACCEPTED MANUSCRIPT
Layered zinc and lanthanum hydroxide nitrates hosting chiral
sulphonato-(salen)manganese(III) complex catalyzed asymmetric
epoxidation reactions
a
b
c
b
a
a
Xiaoyong Li , Qinchao Shen , Guangbin Zhang , Donghua Zhang , Aqun Zheng , Fang Guan ,
a,*
Yang Sun
a
Department of Applied Chemistry, School of Science, Xi’an Jiaotong University, Xi’an, No. 28,
Xianning West Road 710049, PR China
b
School of Materials & Chemical Engineering, Xi’an Technological University, Xi’an, No. 2,
Xuefu Road 710021, PR China
c
Department of Pharmacy, College of Medicine, Xi’an Jiaotong University, Xi’an, No. 76, Yanta
West Road 710061, PR China

Abstract
Layered zinc and lanthanum hydroxide nitrates were first applied as two ion-exchangeable
supports for immobilizing a chiral sulphonato-(salen)manganese(III) complex, and the resulted
catalysts were characterized by FT-IR, elemental analysis, ICP-AES, TGA, conductivity, XRD,
nitrogen physisorption, along with aqueous particle size and zeta potential. Heterogeneous
catalysts showed moderate to good conversions and excellent enantioselectivities in epoxidation
of styrene and α-methylstyrene when iodosylbenzene was employed as terminal oxidant.
Furthermore, the superiority came from heterogeneity, and only filtration could lead to an effective
separation of catalyst from product solution.

*Corresponding author. Tel.: +86 29 82663914; fax: +86 29 82668559.
E-mail address: sunyang79@mail.xjtu.edu.cn (Y. Sun).
1

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Keywords: Layered single-metal hydroxide salt; Sulphonato-(salen)Mn(III); Asymmetric
epoxidation; Conversion; Enantioselectivity; Heterogeneity.
1. Introduction
Synthesis and application of enantiomerically pure epoxides are of continuous significance in
both synthetic chemistry and pharmaceutical industry [1]. In order for synthetic feasibility,
enantiomeric purity, and atom economy as well, the design of effective catalysts for asymmetric
epoxidation of alkenes had constituted an important strategy for large-scale production of fine
chemicals.
Chiral
(salen)manganese(III)
complexes
(salen,
N,N’-bis(salicylidene)ethylenediaminato), initially developed by Jacobsen [2] and Katsuki [3],
were synthetically accessible, inexpensive and nontoxic, and could afford high enantiomeric
excess (e.e.) values as well as conversions in homogeneous catalysis, but exhibited poor catalyst
recovery and recycling. Therefore, studies on immobilization had been carried out for purpose of
heterogeneous catalysis, such as grafting onto polymers [4], inorganic porous materials [5], and
ionic liquids [6]. However, heterogeneous approaches toward ultimate goal were not completely
successful up to date. Limited accessibility of substrate to metal centers restricted conversion and
enantioselectivity, and catalyst leaching would degrade reactivity and contaminate product [7].
Therefore, exploring porous and stable supporting materials had constituted a real challenge in the
future.
Layered double hydroxide (LDH) had attracted attentions due to their potential applications in
industry [8]. The layers in LDH were held together through electrostatic or van der Waals forces,
and interlayer spaces could be utilized by exfoliation or intercalation. LDH, having a generic
2+
3+
n-
formula [M 1-xM (OH) ][A ] zH O with stable porous structure, had been employed as
x
2
x/n
2
2

ACCEPTED MANUSCRIPT
catalyst or supporting material into various catalytic reactions [8]. In particular, Anderson [9] and
Choudary [10] intercalated a sulphonato-Mn(salen) complex into Zn(II) or Mg(II) / Al(III) LDH to
produce active epoxidation catalysts, revealing synergetic effects of salen complex with local
environments.
In addition to LDH, another interesting layered material denoted as layered single-metal
hydroxide salt (abbreviated as LHS) came into sight, and current studies mainly focused on their
synthesis and characterization [11]. When selecting carriers for immobilization of (salen)Mn(III),
LHS showed several advantages over LDH. First, synthesis of LHS was easier, and sometimes
caused a more regular inner structure than LDH [11]. Next, trivalent cations were scarce in LHS,
so interlayer forces were weaker and intercalation of bulkier anions became convenient [11]. At
last, LHS offered an opportunity to study novel lanthanide hydroxide layers that might bear some
other specific physicochemical properties [12].
In this study, layered zinc and lanthanum hydroxide nitrates were prepared for immobilizing a
sulphonato-(salen)Mn(III), and physicochemical characterizations might give structural
information. Terminal oxidants including sodium hypochloride (NaClO) and iodosylbenzene
(PhIO) were loaded into epoxidations of terminal, trans- and cyclic unfunctionalized alkenes, to
comprehensively evaluate heterogeneous catalysts.
2. Experimental
2.1. Starting Materials and Syntheses
Zn(NO ) 6H O, La(OH) 6H O, styrene, α-methylstyrene, trans-stilbene, indene, and
3
2
2
3
2
HPLC-grade solvents were purchased from Sigma-Aldrich without purification.
3

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Zn (OH) (NO ) 2H O (Zn-LHS) [13], La(OH) (NO )H O (La-LHS) [13], synthetic
5
8
3 2
2
2
3
2
intermediates and sulphonato-(salen)Mn(III) (catalyst 1) [14], PhIO [15] were prepared according
to literatures. Catalyst 1 (2 mmol) was water-soluble, its ion-exchanging reactions with Zn-LHS
(2 mmol) or La-LHS (4 mmol) were carried out in distilled water (20 mL) with stirring at room
temperature, supposing complete ion-exchanging of nitrates with catalyst anions (Fig. 1).
Precipitates (both catalysts 2 and 3) were collected by filtration and washed by distilled water (3 ×
30 mL), ethanol (3 × 30 mL), and dichloromethane (3 × 30 mL), to remove possibly physisorbed
catalyst 1, NaNO or organic impurities.
3
2.2. Instrumental Conditions
1
H NMR spectra were acquired on Bruker ADVANCE III (400MHz): CDCl (TMS) for
3
conversions, sample/(CDCl and TMS) 10% (v/v), CDCl /TMS 25/1 (v/v), 295.5 K, on integration
3
3
of methyl hydrogen for α-methylstyrene, and of C=C hydrogen for other olefins, ± 5% relative
error of stated values. FT-IR were collected in KBr pellets on Bruker Tensor 27. The C, H, N
elemental analyses were carried out on Elementar VarioEL III. Metal contents were obtained
through inductive coupled high frequency plasma atomic emission spectrometry (ICP-AES),
ICPE-9000. Conductivities were measured on DDS-11A digital conductivity meter in DMSO at
2
4
98 K. Thermogravimetric analysis (TGA) was performed on NETZSCH TG 209C with TASC
14/4 controller: 10 K/min, 296 K to 893 K. The BET surface area, pore volume, pore radius, and
pore size distribution were recorded on Micromeritics ASAP 2020 at 77.35 K, each sample was
o
degassed in vacuum at 150 C. Bulk density was recorded on SOTAX TD2 density detector,
CAMAG. Aqueous particle size and zeta potential were measured at 298 K on Zetasizer Nano
ZS90 spectrometer, Malvern. X-ray diffraction (XRD) were recorded on Shimadzu XRD-6000
4

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o
o
o
X-ray diffractometer (Cu-Ka , λ 1.54059 Å), 2θ angles of 4 -40 at 0.02 intervals. Thin layer
1
chromatography (TLC) was conducted on GF254 silica gel, coloration by phosphomolybdic acid
(PMA) / ethanol (5% mass percent). HPLC analysis was performed on Waters instrument (system
controller: Waters 1525, binary hplc pump; UV-vis detector: Waters 2998, photodiode array
detector; UV detection: 242 nm), equipped with a CHIRALCEL OD-H column (150 mm × 4.6
-1
mm; 5 μm particle; mobile phase: n-hexane/2-propanol, 93/7, v/v; flow rate: 1.0 mL min ; column
-1
temperature: 300 K; pressure: 4 MPa; sample concentration: 1.0 mg mL in n-hexane; injection:
10 μL).
2.3. Catalysis
For NaClO facilitated reactions: Na HPO (0.05 mol/L, 4 mL) was added to a commercial
2
4
o
NaClO solution (0.58 mol/L, 10 mL) under stirring, buffered pH was 13.1, then pre-cooled at 0 C.
Alkene (2 mmol), catalyst (0.12 mmol Mn, 6 mol% on alkene), and NH OAc (co-catalyst, 0.24
4
mmol) were combined with CH Cl (5 mL) into a round-bottomed flask (250 mL) with addition
2
2
o
funnel at ice-water bath (0 C). Under vigorous stirring, the pre-cooled NaClO solution was
introduced dropwise, and reaction progress was monitored by TLC together with PMA coloration
(
petroleum ether/CH Cl , 2/1, v/v; R of styrene, α-methylstyrene, trans-stilbene, and indene: 0.89,
2 2 f
0
.86, 0.72, 0.75; R of epoxides for above alkenes: 0.26, 0.23, 0.36, and 0.32 correspondingly).
f
After 6 h, the mixture was diluted with CH Cl (30 mL), organic layer was isolated, and
2
2
heterogeneous catalyst was recovered by filtration under reduced pressure from aqueous
suspension. CH Cl layer was washed with water (50 mL), brine (50 mL), dried over anhydrous
2
2
1
Na SO . After evaporation, the residue was suitable for H NMR and HPLC. As a reference, the
2
4
mixture was filtrated after reaction of 6h, and filtrate was monitored by TLC for another 6 h. No
5

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1
increased conversions were detected by H NMR.
For PhIO facilitated: alkene (2 mmol), catalyst (0.12 mmol Mn, 6 mol% on alkene),
iodosylbenzene (2.3 mmol) and NH OAc (co-catalyst, 0.24 mmol) were combined with CH Cl (5
4
2
2
o
mL) into a round-bottomed flask (250 mL) at 0 C. The suspension was stirred vigorously, and
monitored by identical TLC. After 6 h, the mixture was diluted with CH Cl (30 mL), and solid
2
2
catalysts were recovered by filtration. CH Cl layer was washed with water (50 mL), brine (50
2
2
1
mL), dried over Na SO . After evaporation, residue was suitable for H NMR and HPLC. Similar
2
4
reference experiments had proved no further reaction occur after catalyst separation.
3. Results and Discussion
3.1. Characterization of Catalysts
-
1
According to Fig. 2, the broad bands at 3500 to 3200 cm for all samples could be ascribed to
-1
stretching vibration of water hydroxyls. Remarkably, 3635 and 3574 cm for Zn-LHS (b), 3583
-1
and 3539 cm for La-LHS (d) illustrated ZnO-H and LaO-H vibrations [11,13]. Although ZnO-H
absorptions were overlapped with water hydroxyls on catalyst 2 (c), LaO-H vibrations were still
distinctive at the same positions (e). Spectra b, d, e showed sharp peaks at 1636, 1645, and 1645
-
1
-1
cm , which were H O bending vibration (arrow labeled) [13]. Absorption at 1608 cm for catalyst
2
1
was characteristic of C=N stretching that also retained in catalysts 2 and 3 (solid triangles in a, c,
e), indicating effective linkage of salen complex with LHSs. Moreover, IR bands at 1191 and 1066
-
1
-
3
cm stemmed from anti-symmetric and symmetric stretching of SO on catalyst 1 [16], and they
were still in catalyst 2 (hollow triangles in a and c), which further supported grafting. Bands like
-1
-1
1
384 cm for Zn-LHS and 1384, 1338, 1051 cm for La-LHS were all typical vibrations for
6

ACCEPTED MANUSCRIPT
nitrates (asterisks in b and d) [13], but they all shifted or declined after ion-exchanging (asterisks
in c and e), indicating partial replacement of nitrates by anions of catalyst 1.
C, H, N and metal contents (Table 1), as well as TGA (Fig. S1 in Supplementary data) put
forward ideal composition of synthetic products. Zn-LHS and La-LHS contained no carbon, so
formula weights of catalysts 2 and 3 could be determined according to carbon with one
(salen)Mn(III) as criteria. Referencing the reported thermal behaviors of sulphonato-(salen)Mn(III)
o
[
16], Zn-LHS [13], and La-LHS [13], all weight loss below 200 C could be assigned to water
release. Ideal chemical formulae were deduced: Zn (OH) (NO ) 2H O (Zn-LHS),
5
8
3 2
2
La(OH) (NO )H O
(La-LHS),
C H N O S Na MnClH O
(catalyst
1),
2
3
2
28 36
2
8
2
2
2
C H N O S MnCl[Zn (OH) ] (NO ) 56H O
(catalyst
2),
and
2
8
36
2
8
2
5
8 8
3 14
2
C H N O S MnCl[La(OH) ] (NO ) 16H O (catalyst 3). Featuring (salen)Mn(III) as criteria,
2
8
36
2
8
2
2 12.5
3 10.5
2
both catalysts 2 and 3 showed declined molar conductivities than catalyst 1, and with
2
+
+
[
Zn (OH) ] or [La(OH) ] as standard, catalysts 2 and 3 also exhibited lower conductivities than
5 8 2
Zn-LHS and La-LHS, which both proved immobilization of (salen)Mn(III) anions into LHSs
through ion-exchanging [17].
o
The observed interlayer spacing of 9.63 Å (2θ at 9.18 ) for Zn-LHS was amplified to 12.95 Å
o
(
2θ at 6.82 ) for catalyst 2 (Fig. 3), but calculated dimension of a solvated Jacobsen’s complex
was 2.05 nm × 1.61 nm [18], so Zn-LHS probably underwent exfoliation and restacking during
ion-exchanging [11], and planar catalyst 1 seemed to intercalate with Zn-LHS horizontally. Both
Zn-LHS and catalyst 2 showed approximate type III isotherms with H1 hysteresis loop at higher
relative pressure (Fig. 4), revealing a structure composed of uniform spheres in regular array and
narrow distributions of pore size [19]. Catalyst 2 showed improved surface area and pore volume
7

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than Zn-LHS (Table 2), mainly owing to intercalation. On the other hand, d-spacing of 9.64 Å (2θ
o
o
at 9.16 ) for La-LHS was slightly shifted to 9.66 Å (2θ at 9.14 ) for catalyst 3 (Fig. 3), La-LHS
and catalyst 3 showed type II isotherms demonstrating monolayer-multilayer adsorption [19],
together with an improved surface area of catalyst 3 more than La-LHS (Table 2), which all
suggested multilayer deposition of (salen)Mn(III) onto La-LHS surface instead of intercalation.
3.2. Catalytic Reactions
Blank experiments using Zn-LHS or La-LHS (6 mol% metal on alkene) as catalyst, loading
NaClO and PhIO as terminal oxidants for epoxidation of styrene, α-methylstyrene, trans-stilbene,
and indene had been tested before regular catalyses were summarized in Table 3. Under TLC
monitoring during 24 h, neither Zn-LHS nor La-LHS afforded epoxidation product for each
substrate. Catalyst 1 could not promote epoxidation reactions with NaClO. The solutions became
attenuated and no considerable epoxides were detected on HPLC after 24 h. Perhaps, catalyst 1
-
was immiscible with CH Cl and not in line with phase-transfer condition of ClO in Jacobsen
2
2
system [21]. LHS supported (salen)Mn(III) (catalysts 2 and 3), in combination with NaClO,
exhibited better conversions for styrene and α-methylstyrene (entries 2, 7, 9). Nevertheless,
NaClO was aqueous and water molecules were easily coordinated to Zn(II) and La(III) centers,
once channels were occupied by water, the entrance of bulkier olefins to (salen)Mn(III) was
mainly blocked that affected conversions (entries 12, 14, 17, 19). When PhIO loaded as oxidant,
catalysts 1 to 3 afforded pronounced conversions more than those performed under NaClO,
especially for trans-stilbene (entries 11, 13, 15). Furthermore, catalyst 2 consistently afforded
higher conversions for all substrates than catalyst 3 (entries 3 vs. 5, 8 vs. 10, 13 vs. 15, 18 vs. 20),
probably owing to sandwiched structure of catalyst 2 (Fig. 1 and Fig. 3).
8

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Under PhIO, catalyst 1 exhibited good to moderate enantioselectivity for styrene (entry 1),
indene (entry 16), and α-methylstyrene (entry 6), but catalysts 2 and 3 showed great e.e. values for
styrene (entries 3, 5) and α-methylstyrene (entries 8, 10). Catalyst 2 provided best recycling for
styrene and α-methylstyrene (entries 3, 8). Enantioselective epoxidation of styrene and
α-methylstyrene was difficult not only because these terminal alkenes may undergo addition by
(salen)Mn(III) with lower enantiofacial selectivity than cis-disubstituted and trisubstituted alkenes,
but for a nonstereospecific cyclization leading to enantioselectivity leakage [22]. However, this
dilemma could be ameliorated by immobilizing (salen)Mn(III) onto appropriate carriers whose
spatial effects might do work [23]. Catalyst 2 had an sandwich-type local structure featuring
interlayer spacing of 12.95 Å which was narrower than that found in LDH-supported
(salen)Mn(III) [9], probably constraining free rotation of styrene or α-methylstyrene in favor of
enantioselectivity. Acceptable e.e. values were observed for indene with catalysts 2 and 3, but they
were less significant due to low conversions (entries 18 and 20). Additionally, trans-stilbene was
not an appropriate substrate, only catalyst 2 afforded a 48 % e.e. together with 50 % conversion
(entry 13).
4. Conclusion
In summary, LHS-supported catalysts had specific local structures and exhibited moderate to
good conversions, excellent enantioselectivities, as well as satisfactory recycling in epoxidation of
styrene and α-methylstyrene under iodosylbenzene as terminal oxidant. Another superiority of this
system appeared to be heterogeneity. Herein, only filtration could lead to effective separation of
catalyst from product solution.
9

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Acknowledgements
This study was supported by Fundamental Research Funds for the Central University of China.
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Figure Captions
o
Fig. 1. Synthesis of catalysts. Conditions: i) K CO , ethanol/water, 70 C, 2 h; ii) Mn(OAc) ·4H O,
2
3
2
2
o
ethanol/water, N protection, 75 C, 2 h; NaCl, open system, 1 h; iii) Zn (OH) (NO ) 2H O
2
5
8
3 2
2
(
Zn-LHS)/Cat. 1, 1/1 (molar ratio); distilled water, 72 h; iv) La(OH) (NO )H O (La-LHS)/Cat.
2
3
2
1, 2/1 (molar ratio); distilled water, 72 h.
Fig. 2. FT-IR spectra of catalyst 1 (a), Zn-LHS (b), catalyst 2 (c), La-LHS (d), catalyst 3 (e).
Fig. 3. Powdered XRD patterns of Zn-LHS, catalyst 2, La-LHS and catalyst 3.
Fig. 4. N adsorption-desorption isotherms and pore size distributions of Zn-LHS, La-LHS,
2
catalysts 2 and 3.
1
2

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O
H
H
NaO S
ONa
t-Bu
3
+
-
NH3+
OH
N
N
H N
3
HO
Aldehyde
NaO S
ONa NaO
t-Bu t-Bu
SO Na
3
3
ii)
O C
2
CO -
i)
2
Diamine
Na4L
Cat. 1
Na [Mn(L)(Cl)]
2
La-LHS
Zn-LHS
iii)
iv)
H
H
N
N
Mn
O S
3
O
O
SO3
1
2.95 Å
Cl
t-Bu
t-Bu
H
H
N
N
Mn
Cl
O S
3
O
O
SO3
t-Bu
t-Bu
9
.66 Å
Cat. 2
Cat. 3
o
Fig. 1. Synthesis of catalysts. Conditions: i) K CO , ethanol/water, 70 C, 2 h; ii) Mn(OAc) ·4H O,
2
3
2
2
o
ethanol/water, N protection, 75 C, 2 h; NaCl, open system, 1 h; iii) Zn (OH) (NO ) 2H O
2
5
8
3 2
2
(
Zn-LHS)/Cat. 1, 1/1 (molar ratio); distilled water, 72 h; iv) La(OH) (NO )H O (La-LHS)/Cat.
2
3
2
1, 2/1 (molar ratio); distilled water, 72 h.
1
3

ACCEPTED MANUSCRIPT
Fig. 2. FT-IR spectra of catalyst 1 (a), Zn-LHS (b), catalyst 2 (c), La-LHS (d), catalyst 3 (e).
1
4

ACCEPTED MANUSCRIPT
Fig. 3. Powdered XRD patterns of Zn-LHS, catalyst 2, La-LHS and catalyst 3.
1
5

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Fig. 4. N adsorption-desorption isotherms and pore size distributions of Zn-LHS, La-LHS,
2
catalysts 2 and 3.
1
6

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Table 1
a
Chemical composition of supporting materials and catalysts .
b
c
c
c
d
e
Sample
Elemental analysis
Mn
Zn
La
C/Mn
Λ
C
H
N
Zn-LHS
La-LHS
Cat. 1
Cat. 2
Cat. 3
a
-
1.9 (1.9)
1.6 (1.5)
5.9 (5.1)
3.0 (3.4)
2.7 (2.4)
4.4 (4.5)
5.3 (5.5)
4.4 (3.8)
3.2 (3.6)
4.0 (4.6)
-
-
8.10 (8.05)
-
-
190
35
-
-
3.99 (3.95)
-
45.9 (45.0)
5.4 (5.4)
8.9 (8.9)
1.39 (1.34)
0.16 (0.16)
0.27 (0.26)
-
-
27.0
28.1
27.4
187
19
6.39 (6.40)
-
-
3.37 (3.30)
20
Data in parentheses were calculated values based on ideal formulae.
Weight percentage (wt%).
b
c
d
e
-1
Determined by ICP (mmol g ).
Molar ratio of Carbon to Mn.
-1
-1
3+
-3
-1
2+
-3
Conductivity (ohm cm ) detected in DMSO: [Mn ] 1.0×10 mol L for catalysts 1 to 3, [Zn (OH) ] 8.0×10
5
8
-
1
+
-3
-1
mol L for Zn-LHS and catalyst 2, [La(OH) ] 12.5×10 mol L for La-LHS and catalyst 3.
2
1
7

ACCEPTED MANUSCRIPT
Table 2
Physicochemical properties of supporting materials and catalysts.
a
b
c
d
e
f
g
Sample
Zn-LHS 3.78
Cat. 2
21.79
La-LHS 0.63
SBET
PV
PR
ρ
dS
dW
ζ
-
-
-
-
2
2
3
2
3
3
3.07 × 10
9.38 × 10
1.90 × 10
7.31 × 10
134.92
73.77
52.72
30.25
1.56
1.07
2.91
1.70
1.01 × 10
257
483.5
500.2
536.9
596.3
-29.0
-28.0
-30.4
-29.1
3.27 × 10
56.79
Cat. 3
62.14
a
2
-1
Surface area determined by BET method based on nitrogen adsorption (m g ).
b
c
d
e
f
3
-1
Pore volume, BJH method on adsorption (cm g ).
Pore radius, BJH method on adsorption (nm).
-3
Bulk density (g cm ).
Crystallite size based on BET surface area: d = 6/(SBET·ρ), ρ bulk density, nm as unit.
S
Diameter of aqueous particle (nm).
g
Zeta potential of aqueous particle (mV).
1
8

ACCEPTED MANUSCRIPT
Table 3
Enantioselective epoxidation of unfunctionalized alkenes catalyzed by catalysts 1, 2, and 3.
a
d
e
-1
Entry Alkene
Catalyst
Oxidant
Conversion (%)
E.e. (%)
TOF (h )
1
2
3
4
5
6
7
8
9
1
2
2
3
3
1
2
2
3
3
1
2
2
3
3
1
2
2
3
3
PhIO
55
60
82
1.5
1.7
1.1
0.7
1.0
0.8
1.4
2.2
1.4
1.3
1.3
-
NaClO
PhIO
23
b
39 (40, 40, 36)
99 (99, 99, 94)
NaClO
PhIO
25
78
37 (35, 30, 27)
99 (99, 85, 80)
PhIO
29
55
NaClO
PhIO
52
68
79 (77, 77, 70)
99 (99, 97, 97)
NaClO
PhIO
49
72
1
0
47 (45, 40, 29)
46
99 (90, 86, 81)
11
H
Ph
H
PhIO
17
-
c
1
1
1
1
1
1
1
1
2
3
4
5
6
7
8
9
0
Ph
NaClO
PhIO
NF
50
NF
19
33
9
48
-
1.4
-
NaClO
PhIO
20
65
23
56
6
0.5
0.9
0.3
0.1
0.1
0.1
PhIO
NaClO
PhIO
5
NaClO
PhIO
4
2
4
89
a
1
Determined by H NMR.
b
c
d
Values in parentheses were consecutively recycled results.
NF: no epoxides were found on HPLC.
Determined by chiral HPLC. Major epoxide enantiomers: (R)-styrene oxide [20], (R)-α-methylstyrene oxide [20],
1R,2R)-trans-stilbene oxide [20], (1R,2S)-indene oxide [21], after comparison with literatures.
(
e
-1
-1
Turnover frequency of fresh catalysis, molproduct molMn (6 h) .
1
9

ACCEPTED MANUSCRIPT
Graphical abstract
2
0

ACCEPTED MANUSCRIPT
Highlights
1
2
3
4
. Chiral (salen)Mn(III) was immobilized into layered hydroxide salts.
. Heterogeneous catalysts showed excellent e.e. values for terminal alkenes.
. Recycling experiment of heterogeneous catalysts was satisfactory.
. Superiority of this system appeared to be heterogeneity.
2
1