Synthesis, characterization and catalytic activity of supported vanadium Schiff base complex as a magnetically recoverable nanocatalyst in epoxidation of alkenes and oxidation of sulfides

Article abstract of DOI:10.1016/j.jorganchem.2019.06.036

A new magnetically separable nanocatalyst was successfully synthesized by immobilizing of vanadyl acetylacetonate complex, [VO(acac)₂], onto silica coated magnetite nanoparticles previously functionalized with 3-aminopropyltriethoxysilane (3-APTES) and reacted by 5-bromosalicylaldehyde to form Schiff base moiety. The obtained nanocatalyst was characterized by elemental analysis (CHN), FT-IR spectroscopy, Powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), inductively coupled plasma optical emission spectrometry (ICP-OES) and thermogravimetric analysis (TGA). Eventually, the resulting nanoparticles were used as catalyst for epoxidation of alkenes and oxidation of sulfides using tert-butyl hydroperoxide (TBHP) as an oxidant.

Full text of DOI:10.1016/j.jorganchem.2019.06.036

Accepted Manuscript
Synthesis, characterization and catalytic activity of supported vanadium Schiff base
complex as a magnetically recoverable nanocatalyst in epoxidation of alkenes and
oxidation of sulfides
Mojtaba Bagherzadeh, Mohammad Bahjati, Anahita Mortazavi-Manesh
PII:
S0022-328X(19)30283-9
DOI:
https://doi.org/10.1016/j.jorganchem.2019.06.036
JOM 20848
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 9 April 2019
Revised Date: 16 June 2019
Accepted Date: 28 June 2019
Please cite this article as: M. Bagherzadeh, M. Bahjati, A. Mortazavi-Manesh, Synthesis,
characterization and catalytic activity of supported vanadium Schiff base complex as a magnetically
recoverable nanocatalyst in epoxidation of alkenes and oxidation of sulfides, Journal of Organometallic
Chemistry (2019), doi: https://doi.org/10.1016/j.jorganchem.2019.06.036.
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ACCEPTED MANUSCRIPT
Highlights
1. A new magnetically recoverable nanocatalyst has been prepared by
immobilization of VO(acac)2 onto surface of modified silica-coated magnetite
nanoparticles.
2. Modified magnetic nanoparticles were applied as efficient and reusable
nanocatalyst for the heterogeneous oxidation of alkenes and sulfides.
3. Easy work up, chemical stability and simple recyclability are the attractive
features of this catalytic system.

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Synthesis, characterization and catalytic activity of supported
vanadium Schiff base complex as a magnetically recoverable
nanocatalyst in epoxidation of alkenes and oxidation of sulfides
Mojtaba Bagherzadeh*, Mohammad Bahjati, Anahita Mortazavi-Manesh
Chemistry Department, Sharif University of Technology, Tehran, P.O. Box 11155-3615, Iran;
bagherzadeh@sharif.edu
Abstract: A new magnetically separable nanocatalyst was successfully synthesized by
immobilizing of vanadyl acetylacetonate complex, [VO(acac)2], onto silica coated
magnetite nanoparticles previously functionalized with 3-aminopropyltriethoxysilane (3-
APTES) and reacted by 5-bromosalicylaldehyde to form Schiff base moiety. The
obtained nanocatalyst was characterized by elemental analysis (CHN), FT-IR
spectroscopy, Powder X-ray diffraction (XRD), field emission scanning electron
microscopy (FE-SEM), inductively coupled plasma optical emission spectrometry (ICP-
OES) and thermogravimetric analysis (TGA). Eventually, the resulting nanoparticles
were used as catalyst for epoxidation of alkenes and oxidation of sulfides using tert-butyl
hydroperoxide (TBHP) as an oxidant.
Keywords: Vanadyl acetylacetonate, magnetic nanocatalyst, oxidation, alkenes, sulfides
1. INTRODUCTION
Nowadays, because of the importance of environmental and economic issues,
global scientific and industrial discoveries in the field of catalysts should use the
principles of “Green Chemistry” [1-5]. Recovery and reusability are the two
valuable keys after catalytic reactions for the definition of sustainability and will
show that a catalytic process follows the “Green Chemistry” principles [6,7]. But in

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practical applications, using homogeneous catalysts in a real catalytic system has
the basic problems: high cost, time-consuming and boring procedure for the
catalyst separation and recovery [2,8,9]. One way to solve these problems is
heterogenization of homogeneous catalysts on solid supports like polymers,
zeolites and metal oxides [6,10-12]. Among various solid supports, magnetic
nanoparticles (MNPs) have revolutionized in the field of catalysts due to their
unique properties especially simple separation from the reaction mixture.
Supported catalysts on magnetic nanoparticles can be quickly separated from the
reaction mixture by inducing a magnetic field and can be reused for the next time
[13-17].
According to attractive properties of magnetic nanoparticles, they have found
application in various fields, from medical and biology to material science and
catalyst. When the magnetic particles become smaller and smaller, increasing the
surface area and surface-to-volume ratio of these particles causes lots of the
catalytically active structures can be loaded onto the surface and this high loading
increases the activity of catalytic transformations. On the other hand, when the
particles become small, they are easily dispersible in solvents, as a result, access to
the catalytically active sites is more comfortable [6,18]. However, uncoated
magnetic nanoparticles have the tendency to agglomeration. To overcome this
drawback, magnetic nanoparticles coated by protective agents like silica, alumina,
ceria, titania, polymers and other capping agents. Also, this strategy provides
convenient and practical way to immobilize metal complexes on the surface of
magnetite nanoparticles [15,19,20,21].
In this paper, we report the multistep preparation of a new magnetically separable
nanocatalyst as the recyclable catalyst for epoxidation of alkenes and oxidation of
sulfides by immobilizing of [VO(acac)2] onto the surface of the modified

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magnetite nanoparticles. The prepared nanocatalyst can be easily separated from
the reaction mixture with an external magnet and storage for the next reaction.
2. EXPERIMENTAL
2.1. Materials and Methods
All chemical materials and solvents were purchased from chemical companies,
Fluka, Merck and Sigma-Aldrich.
Elemental analysis (CHN) was obtained from a Thermo Finnigan Model FlashEA
1112 series analyzer. Fourier transform infrared (FT-IR) spectra were recorded on
a ABB Bomem MB-100 spectrometer using a KBr pellet for sample preparation.
Powder X-ray diffraction (PXRD) peaks were collected with a Bruker
diffractometer (D4 ENDEAVOR) with Cu Kα as a radiation source (λ= 0.15406
nm, 40 kV, 40 mA). Field emission scanning electron micrograph (FE-SEM)
performed on a TESCAN MIRA ΙΙ for determining the morphology of the obtained
nanoparticles. Metal content of the prepared nanocatalyst was determined by
inductively coupled plasma optical emission spectrometery (ICP-OES) performed
on a Varian 730-ES spectrometer. Gas chromatographic (GC) analyses were
carried out on an Agilent Technologies 6890N, including a 19091J-236 HP-5,5%
phenyl methyl siloxane, capillary column (60.0 m × 250 µm × 1.00 µm).
Thermogravimetric analysis (TGA) were accomplished by METTLER TOLEDO
TGA/DSC.
2.2. Synthesis of Fe3O4 nanoparticles (MNPs)
The Fe3O4 nanoparticles were prepared by co-precipitation method [22]. The
amount of 5.2 g (19.3 mmol) of FeCl3.6H2O and 2 g (10.0 mmol) of FeCl2.4H2O
were dissolved in 100 mL distilled water under Argon atmosphere. Then, 20 mL of

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the 25%.NH3 solution was added dropwise into the precursor solution and the
reaction mixture was vigorously stirred for 30 min at room temperature. The
formed black magnetite precipitates were separated with a magnet and rinsed
several times with distilled water and dried in oven at 80 °C for 24 h.
2.3. Synthesis of silica-coated magnetite nanoparticles (SMNPs)
Silica coating of the prepared Fe3O4 nanoparticles was the next step. The amount of
one gram of the prepared Fe3O4 nanoparticles was added into 40 mL of ethanol and
10 mL of distilled water and dispersed by ultrasonic. After dispersion, 2 mL of
tetraethylorthosilicate (TEOS) was added into the suspension and it was allowed to
stir for 30 min at 40 °C. Eventually, the pH of the reaction mixture was increased
with ammonia to pH=10 and the mixture was stirred at 40 °C for 24 h. The dark
brown silica coated magnetite nanoparticles (SMNPs) were separated with a
magnet and rinsed with distilled water and ethanol and dried in oven at 70 °C for
24 h.
2.4. Synthesis of amino-functionalized silica-coated magnetite nanoparticles
(ASMNPs)
For attaining the amino-functionalized silica-coated magnetite nanoparticle
(ASMNPs), 2.5 mL of 3-aminopropyltriethoxysilane (3-APTES) dissolved in 50
mL of ethanol and was added dropwise to the suspension of 0.5 g of the SMNPs in
50 ml of distilled water. Then, with using KOH, the pH value of the reaction
mixture was increased to pH=11 and the reaction mixture was stirred at 70 °C for 5
h. Eventually, the dark brown ASMNPs were collected using a magnet and
obtained precipitates were rinsed several times with distilled water and dried in
oven at 70 °C for 24 h.

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2.5. Synthesis of Schiff base functionalized silica-coated magnetite
nanoparticles (Sb@SMNPs)
The reaction between amino group of the ASMNPs and carbonyl group of the 5-
bromosalicylaldehyde was carried out via Schiff base condensation reaction. The
amount of 0.5 g of the prepared ASMNPs and 0.2 g (1.0 mmol) of 5-
bromosalicylaldehyde were added in to 50 mL of ethanol and the mixture was
refluxed with continuous stirring for 24 h. The obtained nanoparticles were
separated with a magnet, rinsed several times with ethanol and dried in oven at 70
°C for 24 h.
2.6. Immobilization of VO(acac)2 onto Sb@SMNPs
To immobilize the oxo-vanadium complex onto Sb@SMNPs, commercially
available VO(acac)2 was used as precursor. The amount of 0.2 g (0.75 mmol) of
VO(acac)2 and 0.1 g of the prepared Sb@SMNPs were added into 10 mL of
methanol and the mixture was vigorously stirred and refluxed for 24 h. The
obtained nanoparticles were separated with a magnet, rinsed several times with
methanol and dried in oven at 70 °C for 24 h. Formation of the obtained product
was corroborated by FT-IR.
2.7. General procedure for epoxidation of alkenes and oxidation of sulfides
In a typical run, nanocatalyst (1 mg, 0.51 × 10-3 mmol), substrate (0.2 mmol) and
tert-Butyl hydroperoxide (0.6 mmol) were added into 1 mL of 1,2-dichloroethane
(DCE) in a tube. Then, the mixture was stirred vigorously at 85 °C. At the end of
each reaction, the nanocatalysts were collected using a magnet, rinsed several
times with DCE, dried under in oven and reused. Formation of products and
consumption of substrates were monitored by gas chromatography (GC).

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2.8. Reusability of the nanocatalyst
For determining the reusability and sustainability of the prepared nanocatalyst, at
the end of each reaction, the nanocatalyst was separated from the reaction mixture
with a magnet, washed several times with DCE and dried in room temperature for
24 h.
3. RESULTS AND DISCUSSION
3.1. Characterization
3.1.1. FT-IR Spectroscopy
The preparation of product in each step was confirmed by FT-IR spectroscopy.
Fig. 1 shows the FT-IR spectra of MNPs, SMNPs, ASMNPs, Sb@SMNPs and
VO(acac)@Sb@SMNPs in the range of 400-4000 cm-1. Fig. 1a indicates a peak at
590 cm-1 due to the Fe-O stretching vibration and a broad peak at 3435 cm-1 is
associated to the stretching vibration of surface hydroxyl groups. In Fig. 1b, the
silica coating of the MNPs was corroborated by peaks at 806 cm-1 and 1103 cm-1
which attributed to the Si-O-Si symmetric and Si-O-Si asymmetric stretching
bands, respectively. The FT-IR spectra of Fe3O4@SiO2-NH2 depicts a doublet peak
at 2870 cm-1 and 2935 cm-1 corresponding to symmetric and asymmetric stretching
modes of -CH2 groups, respectively (Fig. 1c). In Fig. 1d, after the reaction between
ASMNPs and 5-bromosalicylaldehyde, the product shows a peak at 1643 cm-1
which assigned to imine group. In comparison with Sb@SMNPs (Fig. 1d), it is
observed that the peak at 1643 cm-1 shifted to 1630 cm-1 due to the covalent
binding of the Sb@SMNPs to the metal center and confirms that anchoring of
vanadium was successfully completed onto the surface of Sb@SMNPs (Fig. 1e).

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3.1.2. X-ray Diffraction Studies (XRD)
To study the crystalline structure of the prepared nanocatalyst, XRD analysis was
carried out. In Fig. 2, the XRD pattern of the prepared nanocatalyst involves of six
characteristic peaks (2
θ = 30.26°, 35.62°, 43.3°, 53.6°, 57.25° and 62.9°)
corresponding to (220), (311), (400), (422), (511) and (440) brag reflection,
respectively. These diffraction peaks are consistent with the database in JCPDS file
(JCPDS no. 19-0629) assigned to the planes of inverse cubic spinel structured
Fe3O4 [23-25]. Also, Fig. 2b shows the XRD pattern of the nanocatalyst after 7th
catalytic reaction cycle. The same characteristic peaks can also be found in this
pattern suggesting that the crystalline structure of Fe3O4 nanoparticles does not
change after 7th reaction run.
3.1.3. FE-SEM and EDX Analysis
The morphological and structural properties of the nanoparticles were studied by
FE-SEM. Fig. 3 shows the FE-SEM image of the prepared nanoparticles. As
shown in the image, the nanoparticles have a spherical shape with particle diameter
between 30-50 nm. Also, EDX analysis (Fig. 4), corroborated the presence of
vanadium in the obtained nanoparticles. In addition, the vanadium content of the
nanoparticle was found to be 0.51 mmol.g-1 by using ICP-OES technique. Based
on the nitrogen content (0.8% N, 0.57 mmol.g-1) determined by elemental analysis
(CHN), the molar ratio of the Schiff base and vanadium in the synthesized
nanocatalyst is nearly 1:1 which agreement with structure it has been shown in
scheme.1.
3.1.4. Thermogravimetric Analysis (TGA)

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The thermal stability of the nanocatalyst was evaluated by TGA and resulting
thermogram depicted in Fig. 5. The TG curve of the VO(acac)@Sb@SMNPs
exhibited three mass losses in the range of 25-800 °C. The first weight loss (3.8 %)
between 25 and 205 °C arising from the fact that physically adsorbed water was
evaporated. The second and third weight loss (3.3 % and 2.06 %, respectively)
between 205 °C and 800 °C ascribe to the loss of organic groups.
3.2. Catalytic Studies
Vanadium compounds have attracted much attention because they have widely
been used for homogeneous, heterogeneous and industrial oxidation processes [26-
29]. In this way, catalytic performance of the prepared nanocatalyst was
investigated in the epoxidation of alkenes and oxidation of sulfides.
In order to find best reaction condition, we used cyclooctene as a model. To find
the best oxidant for this reaction, under same temperature and reaction time,
different oxidants such as TBHP, H2O2 and UHP (urea-hydrogen peroxide) were
examined and finally TBHP was found to be the best oxidant for the epoxidation of
cyclooctene (Table 1).
Different amounts of the nanocatalyst were used (Table 2, entries 1-5) and results
show that increasing the catalyst amount from 0.51×10-3 to 2.55×10-3 mmol did not
significantly affect the conversion. Among various quantity of the
substrate/oxidant ratio (entries 1, 6-8), the ratio 1:3 for substrate and oxidant was
concluded. Effect of solvent on the catalytic activity was studied by using some of
solvents (entries 1, 9-13). Due to the competition between solvents with TBHP for
coordination to the vanadium center, non-coordinating solvents such as 1,2-
dichloroethane, chloroform and n-hexane were exhibited high conversion than
coordinating solvents (ethanol, methanol and acetonitrile). After finding out the

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best solvent (DCE), different temperatures were tested (entries 1, 14-16) and 85 °C
was found to be the best reaction temperature.
Under optimized reaction conditions, epoxidation of some alkene was evaluated
(Table 3). Cyclooctene as an example for cyclic alkene showed notable conversion
and selectivity (entry 1). For styrene and its derivatives (entries 2-5),
α-
methylstyrene showed significant selectivity. Cis stilbene and trans stilbene
showed conversion and selectivity close to each other (entries 6-7). In linear
substrates such as 1-octene and trans-2-octene (entries 8-9), trans-2-octene showed
high conversion and selectivity than 1-octene which indicates that internal carbon
double bond more active than terminal carbon double bond.
Also, under optimization condition that found for epoxidation of alkenes, oxidation
of some sulfide to corresponding sulfoxide was studied (Table 4). The results show
that oxidation of sulfides to corresponding sulfoxides exhibited excellent
selectivity and conversion after 1 h.
3.2.1. Reusability
Catalyst stability and reusability are two great importance parameters for
identifying heterogeneous catalytic systems. To examine the stability and
reusability of the nanocatalyst, at the end of each reaction, catalyst was collected
with a magnet, rinsed several times with DCE and dried for 24 h. Epoxidation of
cyclooctene was chosen as a model substrate to study the reusability of the
synthesized nanocatalyst. Results were shown in Fig. 6. For determining catalyst
leaching, after seven run, vanadium content was analyzed by ICP-OES that shows
some vanadium moieties were separated from the surface of Sb@SMNPs. The
catalyst was consecutively reused about six times without significant loss of
activity. It should be mentioned that the decrease of catalytic efficiency after

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reusing for six runs may be due to release of surface-adsorbed or loosely
coordinated VO(acac)2 complex.
3.2.2. Proposed Mechanism
According to the previous studies which were investigated by Conte et al., the
accepted mechanism for epoxidation of alkenes by oxovanadium catalysts in the
presence of TBHP was illustrated in Fig. 7 [30]. At first, intermediate I
(oxovanadium (V)) formed by oxidation of oxovanadium (IV) with TBHP.
Afterward, by simultaneously proton transfer from TBHP to V=O group, TBHP is
coordinated to the metal center which acts as a Lewis acid to form the intermediate
II. Eventually, interaction between the intermediate II and the alkene, causes
formation of the final products, epoxy compound and t-BuOH. Also, to confirm the
proposed mechanism, the epoxidation reaction of cyclooctene was controlled in the
presence of hydroquinone as the radical trap and results showed that there was no
change in the activity of the nanocatalyst for this reaction.
Finally, we compared the performance of VO(acac)Sb@SMNPs in the epoxidation
of alkenes with other published works (Table 5). Based on these results, catalytic
epoxidation of alkenes and oxidation of sulfides in the presence of
VO(acac)Sb@SMNPs were preferable from the point of view of time, solvent,
oxidant and amount of catalyst.
4. CONCLUSIONS
In brief, we have synthesized a new magnetically recoverable nanocatalyst by
immobilization of VO(acac)2 onto surface of modified silica-coated magnetite
nanoparticles. The prepared nanocatalyst has been characterized by several

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techniques such as FT-IR, elemental analysis (CHN), XRD, ICP-OES, FE-SEM
and TGA. The synthesized nanoparticles used as the catalyst for epoxidation of
alkenes and oxidation of sulfides using TBHP as the oxidant and 1,2-
dichloroethane as the solvent. Results showed that catalytic epoxidation of alkenes
to corresponding epoxides in the presence of VO(acac)Sb@SMNPs is notable.
Also, oxidation of sulfides in the optimum condition that found for epoxidation of
alkenes showed excellent conversion and selectivity. Easy separation and recovery
from the reaction mixture only with a magnet are other plus points of using this
nanocatalyst in the consecutive runs that have a significant role in the field of
catalysis.
Acknowledgments
Financial assistance from Sharif University of Technology is acknowledged.
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SCHEME CAPTIONS:
SCHEME 1 Step-by-step synthesis of the VO(acac)@Sb@SMNPs nanocatalyst
FIGURE CAPTIONS:
FIGURE 1 FT-IR Spectra of a) MNPs; b) SMNPs; c) ASMNPs; d) Sb@SMNPs and e)
VO(acac)@Sb@SMNPs
FIGURE 2 XRD pattern of fresh (a) and used (b) nanocatalyst after 7th reaction cycle
FIGURE 3 FE-SEM image of VO(acac)@Sb@SMNPs
FIGURE 4 EDX analysis of VO(acac)@Sb@SMNPs
FIGURE 5 TGA curve of VO(acac)@Sb@SMNPs
FIGURE 6. Reusability of the nanocatalyst in the epoxidation of cyclooctene. Reaction
conditions: cyclooctene (0.2 mmol), TBHP in water (0.6 mmol), catalyst (1.0 mg), C2H4Cl2 (1
mL), 85 °C and 7 h reaction.
FIGURE 7 The proposed mechanism for epoxidation of alkenes with VO(acac)@Sb@SMNPs
TABLE CAPTIONS:
. Epoxidation of cyclooctene with different oxidants in presence of VO(acac)Sb@SMNPs
. Effect of the catalyst amount, TBHP amount, various solvents and temperature on the
epoxidation of cyclooctene with

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. Epoxidation of cyclooctene with different oxidants in presence of
a
Entry Catalyst Oxidant Conversion (%)b Selectivity (%)c TONd
(mmol)
1
0.51×10-3
H2O2
---------------
(10)e
------------
(100)e
100
--
(39)e
4
2
3
0.51×10-3
0.51×10-3 TBHP
UHP
Trace
55
100
216
a Reaction conditions: cyclooctene (0.2 mmol), oxidant (0.2 mmol), catalyst (1 mg, 0.51 × 10-3 mmol),
C2H4Cl2 (1 mL), reaction time: 7 h and 85 °C.
b GC conversion based on starting alkene.
c Selectivity to epoxide = ((epoxide)/(epoxide + other products)) × 100.
d TON = (mmol of product)/(mmol of catalyst).
e Values in parentheses were obtained in the presence of acetonitrile as solvent.

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. Effect of the catalyst amount, TBHP amount, various solvents and
temperature on the epoxidation of cyclooctene with
1 mg catalyst
O
TBHP as oxidant
Entry
Catalyst
(mmol)
Oxidant
(mmol)
0.6
Solvent
Temperature
°C)
Conversion
Selectivity
(%)c
100
TONd
(
(%)b
88
90
91
91
92
55
84
86
29
40
19
82
53
44
30
24
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
0.51×10-3
1.02×10-3
1.53×10-3
2.04×10-3
2.55×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
0.51×10-3
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
85
85
85
85
85
85
85
85
85
85
85
85
85
70
60
r.t.
345
176
119
89
0.6
0.6
0.6
0.6
0.2
0.4
0.8
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
72
216
329
337
114
159
75
322
208
173
118
94
Ethanol
Methanol
Acetonitrile
Chloroform
n-Hexane
DCE
DCE
DCE
a Reaction conditions: cis-cyclooctene (0.2 mmol), C2H4Cl2 (1 ml), reaction time: 7 h. GC conversions
based on starting alkenes. c Selectivity to epoxide= ((epoxide)/(epoxide + other products)) × 100. d TON =
(mmol of product) / (mmol of catalyst).
b

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Entry
Substrate
Time (h)
Conversion (%)b
Selectivity (%)c
TONd
1
2
3
4
Cyclooctene
Styrene
7
7
7
9
88
94
95
76
>99
55
345
369
373
298
4-methyl styrene
4-methoxy styrene
48
76
5
6
α-methyl styrene
9
7
91
56
95
47
357
220
Cis stilbene
7
8
Trans stilbene
1-octene
7
9
61
40
50
42
239
157
9
Trans 2-octene
9
67
54
263
a Reaction conditions: substrate (0.2 mmol), TBHP (0.6 mmol), catalyst (0.51 × 10-3 mmol), C2H4Cl2 (1
ml) and 85 °C. b GC conversions based on starting alkenes. c Selectivity to epoxide= ((epoxide) / (epoxide
+ other products)) × 100. d TON = (mmol of product) / (mmol of catalyst).

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Entry Substrate
Time Conversion (%) b Selectivity (%) c TON d
(h)
1
Methyl phenyl
1
100
100
392
sulfide
2
3
4
5
Diallyl sulfide
Diphenyl sulfide
Dibuthyl sulfide
Benzyl phenyl
sulfide
1
1
1
1
88
71
100
64
100
100
100
100
345
278
392
251
a Reaction conditions: substrate (0.2 mmol), TBHP (0.6 mmol), catalyst (0.51 × 10-3 mmol), C2H4Cl2 (1
b
c
ml) and 85 °C. GC conversions based on starting sulfides. Selectivity to sulfoxide= ((sulfoxide) /
(sulfoxide + sulfone)) × 100. d TON = (mmol of product) / (mmol of catalyst).

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Comparison of this work with other published works for the cyclooctene
epoxidation
Entry
Catalyst
Oxidant
Time (h) Conversion
(%)
Ref.
1
VO(acac)Sb@SMNPs
TBHP (70%
aq)
7
88
This
work
[31]
[31]
[32]
2
3
4
VO(Sal-Tryp)/AmpSCMNPs
VO(Sal-His)/AmpSCMNPs
Fe3O4@SiO2@ PTMS @Mel-
Naph-VO
TBHP
TBHP
TBHP
8
8
8
50
70
80
5
V-MCM-41
TBHP (70%
aq)
24
90
[33]

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