Epoxidation of alkenes and oxidation of sulfides catalyzed by a new binuclear vanadium bis-oxazoline complex

Article abstract of DOI:10.1007/s13738-014-0505-8

Bis(oxazoline) ligand, [2,2′-(1,3-phenylene)bis(oxazole-4,2-diyl)]-dimethanol, derived from dicyanobenzene was applied as ligand for complexation with vanadium.The catalyst was characterized by FT-IR, UV-Vis, ¹H NMR spectroscopic methods, CHNS, ICP and thermal analyses, and magnetic susceptibility. The catalytic activity of this complex was then studied in the epoxidation of alkenes with TBHP (tert-butyl hydroperoxide), in acetonitrile. The effect of reaction parameters such as kind of solvent and oxygen donors was studied in the epoxidation of cyclooctene. The catalytic activity of this catalyst was also investigated in the oxidation of sulfides with H₂O2 in ethanol and the corresponding sulfoxides and sulfones were produced.

Full text of DOI:10.1007/s13738-014-0505-8

J IRAN CHEM SOC
DOI 10.1007/s13738-014-0505-8
ORIgINAl PAPER
Epoxidation of alkenes and oxidation of sulfides catalyzed
by a new binuclear vanadium bis‑oxazoline complex
Maedeh Moshref Javadi · Majid Moghadam ·
Iraj Mohammadpoor‑Baltork ·
Shahram Tangestaninejad · Valiollah Mirkhani
Received: 19 February 2014 / Accepted: 10 Juꢀy 2014
©
Iranian Chemicaꢀ Society 2014
Abstract Bis(oxazoꢀine) ꢀiꢁand, [2,2′-(1,3-phenyꢀene)bis
oxazoꢀe-4,2-diyꢀ)]-dimethanoꢀ, derived from dicyanoben-
speciaꢀ interest. Many vanadium compꢀexes have aꢀready
been synthesized and estabꢀished oraꢀ insuꢀin mimetic activity
[5]. Vanadium (V) centers, havinꢁ ꢀow radius/charꢁe ratio, are
usuaꢀꢀy stronꢁ lewis acids, which makes them suitabꢀe for
the activation of peroxidic reaꢁents [6]. Consequentꢀy, vana-
dium (V) compꢀexes have been estabꢀished to act as cataꢀyst
precursors in numerous oxidation reactions such as epoxida-
tions of aꢀkenes and aꢀꢀyꢀic aꢀcohoꢀs, oxidations of suꢀfides
to suꢀfoxides and suꢀfones, bromination reactions, oxida-
tions of primary and secondary aꢀcohoꢀs to the correspond-
inꢁ aꢀdehydes and ketones, and hydroxyꢀations of aꢀkanes
and arenes [7]. Bis-oxazoꢀine (= bis[4,5-dihydrooxazoꢀe];
box) ꢀiꢁands have estabꢀished the ꢁreatest share of attention
in N-containinꢁ ꢀiꢁands, for instance saꢀen [8], semicorrins
[9], suꢀfoximines [10], 2,2′-bipyridines [11], diimines [12],
amidines [13], and ꢀateꢀy, imidates with an exocycꢀic coordi-
natinꢁ N-atom [14]. Box ꢀiꢁands are known as inexpensive,
easiꢀy avaiꢀabꢀe, and pretty much stabꢀe [11]. These ꢀiꢁands
are very versatiꢀe and present severaꢀ points of ranꢁe. The
seꢀectivity and activity can be modified by chanꢁinꢁ the start-
inꢁ amino acid, the nature and substituents at the bridꢁe, and
the nature of the metaꢀ [15]. Consequentꢀy, the desiꢁn, syn-
(
zene was appꢀied as ꢀiꢁand for compꢀexation with vanadium.
1
The cataꢀyst was characterized by FT-IR, UV–Vis, H NMR
spectroscopic methods, CHNS, ICP and thermaꢀ anaꢀyses,
and maꢁnetic susceptibiꢀity. The cataꢀytic activity of this
compꢀex was then studied in the epoxidation of aꢀkenes with
TBHP (tert-butyꢀ hydroperoxide), in acetonitriꢀe. The effect
of reaction parameters such as kind of soꢀvent and oxyꢁen
donors was studied in the epoxidation of cycꢀooctene. The
cataꢀytic activity of this cataꢀyst was aꢀso investiꢁated in the
oxidation of suꢀfides with H O in ethanoꢀ and the corre-
2
2
spondinꢁ suꢀfoxides and suꢀfones were produced.
Keywords Bis(oxazoꢀine) · Epoxidation · Suꢀfoxidation ·
Vanadium compꢀex · TBHP · H O2
2
Introduction
The oxidation of orꢁanic substrates by transition metaꢀ com-
pꢀexes has become an important research area in both orꢁanic
synthesis and bioinorꢁanic modeꢀinꢁ of oxyꢁen transfer
metaꢀꢀoenzymes [1–4]. Amonꢁ these metaꢀs vanadium has
thesis, and appꢀication of C -symmetric box ꢀiꢁands have
2
received a ꢀot of attention [16]. Since their initiaꢀ report, a ꢀot
of research have been devoted toward the synthesis and appꢀi-
cation of these box ꢀiꢁands. Durinꢁ the ꢀast decade, numerous
chiraꢀ box ꢀiꢁands with different backbones, such as aꢀiphatic
chains, aromatic rinꢁs, 4,5-dioxoꢀane, dibenzocycꢀoheptene,
biphenyꢀ and binaphthyꢀ, and cycꢀic rinꢁs have been reported
Electronic supplementary material The onꢀine version of this
articꢀe (doi:10.1007/s13738-014-0505-8) contains suppꢀementary
materiaꢀ, which is avaiꢀabꢀe to authorized users.
M. M. Javadi · M. Moꢁhadam (*) · I. Mohammadpoor-Baꢀtork ·
S. Tanꢁestaninejad · V. Mirkhani
Department of Chemistry, Cataꢀysis Division, University
of Isfahan, 81746-73441 Isfahan, Iran
[
17–19]. Interest is aꢀso ꢁrowinꢁ in the desiꢁn of poꢀydentate
ꢀiꢁands that couꢀd form di- and poꢀy-nucꢀear compꢀexes [20].
Recent studies indicate that dinucꢀear and cꢀuster compꢀexes
have been used in the cataꢀysis [21, 22], and modeꢀinꢁ the
cataꢀytic activity of metaꢀꢀoenzymes [23]. Severaꢀ exampꢀes
reveaꢀ that dinucꢀear metaꢀ compꢀexes can exhibit discrete
e-maiꢀ: moꢁhadamm@sci.ui.ac.ir
I. Mohammadpoor-Baꢀtork
e-maiꢀ: imbaꢀtork@sci.ui.ac.ir
1
3

J IRAN CHEM SOC
TBHP, CH CN
3
+
Oxidation products
O
O
N
O
O
O
H O
V
OH2
2
H
2
O
V
OH
2
O
O
N
O
O
or
S
R
R'
O
S
O
O
S
R
R'
+
R
R'
H O , EtOH
2
2
Scheme 1 Epoxidation of aꢀkenes and oxidation of suꢀfides
1
advantaꢁes over mononucꢀear metaꢀ compꢀexes. Such com-
pꢀexes can meditate muꢀtieꢀectron transfers [24] and aꢀso
activate a substrate by simuꢀtaneous coordination to two (or
more) metaꢀ centers [25].
or siꢀica to remove peroxide impurities. H NMR spectra
were recorded in CH OH-d or DMSO-d soꢀvent on a
Bruker-Avance 400 MHz spectrometer. FT-IR spectra were
obtained as potassium bromide peꢀꢀets in the ranꢁe of 400–
4,000 cm and were run on a Jasco 6300D instrument.
gas chromatoꢁraphy experiments (gC) were performed
on a Shimadzu gC-16A instrument usinꢁ a 2 m coꢀumn
packed with siꢀicon DC-200 or Carbowax 20 m. UV–Vis
spectra were obtained on a Shimadzu UV 265 spectrom-
eter. The vanadium content of the cataꢀyst was determined
by a Jarreꢀꢀ-Ash 1100 ICP spectrophotometer.
3
4
6
−1
Aꢀthouꢁh the potentiaꢀ of muꢀtidentate oxazoꢀine-based
ꢀ
ꢀ
iꢁands is obvious, reports describinꢁ their use are stiꢀꢀ
imited. This reason and the successfuꢀ appꢀications of bis-
oxazoꢀines, prompted us to expꢀore the prospective of these
types of ꢀiꢁands with the combination of exceptionaꢀ fea-
tures of vanadium, as cataꢀyst in the epoxidation of aꢀkenes
and oxidation of suꢀfides (Scheme 1).
The bis-oxazoꢀine ꢀiꢁand was synthesized usinꢁ our pre-
viousꢀy reported method [26].
Experimental
generaꢀ procedure for synthesis of vanadium compꢀex
Aꢀꢀ materiaꢀs and chemicaꢀs were of commerciaꢀ rea-
ꢁ
ent ꢁrade and prepared from Merck, Aꢀdrich or Fꢀuka.
The bis-oxazoꢀine was metaꢀꢀated as foꢀꢀows: A deꢁassed
ethanoꢀ soꢀution (40 mꢀ) of the correspondinꢁ bis-oxazo-
ꢀine (276 mꢁ, 1 mmoꢀ) was added to a soꢀution of V(O)
Aꢀkenes were obtained from Merck or Fꢀuka and were
passed throuꢁh a coꢀumn containinꢁ active aꢀumina and/
Scheme 2 Preparation route for
cataꢀyst
NC
CN
OH
HO
OH
SSA
N
N
+
Reflux or .))))
O
O
HO
NH2
VO(acac)2
Ethanol
Reflux
O
O
O
O
OH2
H O
V
OH2
2
H O
2
V
O
O
N
N
O
O
1
3

J IRAN CHEM SOC
(
acac) (1 mmoꢀ, 265.16 mꢁ) in absoꢀute ethanoꢀ (20 mꢀ)
unreacted V(O)(acac) . This dark ꢁreen product was then
2
2
under arꢁon atmosphere. The reaction was stirred under
reflux conditions for 24 h. The soꢀution was then cooꢀed,
fiꢀtered, and evaporated under reduced pressure. This crude
product was then dissoꢀved in dichꢀoromethane to remove
dissoꢀved in methanoꢀ, fiꢀtered, and the soꢀvent was evap-
orated under reduced pressure to ꢁive the pure product.
Yieꢀd: (119 mꢁ, 39.3 %, yeꢀꢀow-brownish powder). Eꢀe-
mentaꢀ Anaꢀysis: Anaꢀ. found C, 33.35; H, 5.25; N, 4.86.
Caꢀc. for C H N O V (M = 512.21) C, 32.83; H,
1
4
22
2
12
2
W
5
.33; N, 4.97.
1
00
3
hrs.
6hrs.
generaꢀ procedure for oxidation of aꢀkenes with TBHP
cataꢀyzed by vanadium BOX compꢀex
8
6
4
2
0
0
0
0
0
In a round-bottom flask (25 ml) equipped with a con-
denser, a ꢁas inꢀet, and a maꢁnetic stirrer, a soꢀution of
aꢀkene (1 mmoꢀ) in acetonitriꢀe (4 ml) was prepared.
The vanadium bis-oxazoꢀine compꢀex (0.013 mmoꢀ,
0
.026 mmoꢀ V) and TBHP (2 mmoꢀ) were added to this
soꢀution and the reaction mixture was stirred under reflux
conditions. The reaction proꢁress was monitored by gC.
After compꢀetion of the reaction, the mixture was directꢀy
passed throuꢁh a short coꢀumn of siꢀica-ꢁeꢀ (1:1, n-hex-
ane–ethyꢀ acetate) to remove the cataꢀyst. The eꢀute was
evaporated under reduced pressure and the remaininꢁ
residue was purified by pꢀate thin ꢀayer chromatoꢁraphy
(eꢀuted with CCꢀ :Et O = 9:1) to afford the correspondinꢁ
No catalyst
0.003
0.007
0.01
0.013
Catalyst Amount (mmole)
Fig. 1 Optimization of cataꢀyst amount in the epoxidation of
cycꢀooctene
100
4
2
3hrs.
6hrs.
epoxide.
80
60
40
20
0
generaꢀ procedure for oxidation of suꢀfides with H O
cataꢀyzed by vanadium BOX compꢀex
2
2
In a 25 ml round-bottom flask equipped with a maꢁ-
netic stirrinꢁ bar, a soꢀution of suꢀfide (1 mmoꢀ), cataꢀyst
(0.01 mmoꢀ, 0.02 mmoꢀ V) in ethanoꢀ (4 ml) was prepared.
H O (2 mmoꢀ) was added to this soꢀution and the reaction
H2O2
TBHP
NaIO4
UHP
KHSO5
2
2
Oxidant
mixture was stirred under reflux conditions. The reaction
proꢁress was monitored by TlC. After the reaction was
compꢀeted, the isoꢀation and purification of the products
were done as described above.
Fig. 2 The effect of different oxidants in the oxidation of cycꢀooc-
tene cataꢀyzed by vanadium compꢀex
Fig. 3 The effect of different
soꢀvents in the oxidation of
cycꢀooctene cataꢀyzed by vana-
dium compꢀex
100
3hrs.
6hrs.
80
60
40
20
0
Solvent
1
3

J IRAN CHEM SOC
4
4
Results and discussion
δ = 8.34 (t, J
= 1.6 Hz, 1H), 7.94 (dd, J
= 1.6 Hz,
H−H
H–H
3
3
J
= 7.6 Hz, 2H), 7.55 (t, J
= 7.6 Hz, 1H),
H–H
H–H
Preparation and characterization of the bis-oxazoꢀine
and the vanadium compꢀex
4.84–4.80 (m, 2H, 2 × CHN = C), 4.45–4.29 (m, 4H,
2 × CH O), 3.56–3.31 (m, 4H, 2 × CH OH) (Fiꢁ. S2).
2
2
As seen in Fiꢁ. S3, the [V (O) (H O) BOX] shows
2
4
2
4
The preparation route for cataꢀyst is shown in Scheme 2.
The prepared cataꢀyst was characterized by eꢀementaꢀ
anaꢀysis, maꢁnetic susceptibiꢀity, FT-IR, and UV–Vis spec-
troscopic methods. The FT-IR spectrum of homoꢁeneous
a peak at ꢀ
= 214 nm which is attributed to the
max
O(pπ) → V(dπ) charꢁe-transfer transition [27]. Tg and
DTg data show that this compꢀex decomposes in three steps
at about 180, 400, and 600 °C (Fiꢁ. S4). This is in accord-
ance with the data obtained from meꢀtinꢁ point studies.
Accordinꢁ to the ICP and CHN anaꢀyses, the ratio
between V and the ꢀiꢁand was 1.93 that confirms that the
cataꢀyst consists of two vanadium metaꢀs and is therefore
binucꢀear. The maꢁnetic susceptibiꢀity experiments showed
that this compꢀex is diamaꢁnetic and therefore it is a V(V)
compꢀex with no d eꢀectron.
−
V (O) (H O) BOX] (Fiꢁ. S1) shows a band at 1,642 cm
2 4 2 4
1
[
−
1
for ν(C = N), and the band at 972 cm is attributed
1
to the ν(V = O) bonds. H NMR (400 MHz, DMSO-d )
6
100
3hrs.
6hrs.
8
0
0
0
0
6
4
2
Cataꢀytic aꢀkene epoxidation with TBHP in the presence
of the vanadium compꢀex as cataꢀyst
Initiaꢀꢀy, the cataꢀytic activity of the prepared cataꢀyst was
tested usinꢁ cycꢀooctene as reference aꢀkene. Aꢀꢀ reactions
were continued untiꢀ no proꢁress was observed. Oxida-
tion was carried out in the presence of cataꢀytic amounts
of vanadium bis-oxazoꢀine. First, we optimized the cataꢀyst
amount in the oxidation of cycꢀooctene. The resuꢀts showed
that when 0.013 mmoꢀ of cataꢀyst was used in the oxidation
0
25°C
60°C
Reflux
Temperature
Fig. 4 The effect of temperature in the oxidation of cycꢀooctene cata-
yzed by vanadium compꢀex
ꢀ
a
Table 1 Epoxidation of aꢀkenes with [V (O) (H O) BOX] in the presence of acetonitriꢀe and TBHP.
2
4
2
4
Conversion
Epoxide
Time TOF
a
Row Substrate
1
Product
b
-1
(%)
Yield (%)
(h)
(h )
O
96
96
4
6
6.0
O
2
3
4
100
91
10
6
3.8
5.7
4.7
O
O
O
O
H
45
0
O
99
8
O
5
6
7
8
96
94
64
25
96
94
64
25
10
10
10
10
3.6
3.5
2.4
0.9
O
O
O
a Reaction conditions: aꢀkene (1 mmoꢀ), TBHP (2 mmoꢀ), cataꢀyst (0.013 mmoꢀ, 0.026 mmoꢀ V), acetonitriꢀe (4 ml)
b
gC yieꢀd based on the startinꢁ aꢀkene
1
3

J IRAN CHEM SOC
Table 2 Comparison of the resuꢀts obtained for epoxidation of aꢀkenes cataꢀyzed by [V (O) (H O) BOX] with some previousꢀy reported sys-
2
4
2
4
tems
o
−1
)
Entry
Cataꢀyst
Aꢀkene
Oxidant
Conditions ( C)/soꢀvent
TOF (h
References
1
2
3
4
[V (O) (H O) BOX]
Styrene
TBHP
TBHP
TBHP
TBHP
Reflux/acetonitriꢀe
Reflux/DCE
55/DCE
5.7
5.4
2
This work
[26]
2
4
2
4
Mo O (acac) box
Styrene
2
4
2
[MoI (CO) (pheH)]
Cycꢀooctene
Cycꢀooctene
[28]
2
3
[MoO [1,2-diphenyꢀethyꢀenebis(3-
Reflux/DCE
5
[29]
2
oxyethyꢀpyrroꢀe)saꢀicyꢀideneiminate]]
a
5
6
[(l ) V = O]
Styrene
Styrene
TBHP
TBHP
RT/toꢀuene
RT/toꢀuene
0.4
0
[30]
[30]
1
2
a
[(l ) MoO ]
1
2
2
a
Hl = 2-(4,4′-dimethyꢀ-3′,4′-dihydroxazoꢀ-2′-yꢀ)phenoꢀ
1
Fig. 5 The effect of cataꢀyst
amount in the oxidation of
100
5
min.
10 min.
15 min.
20 min.
diphenyꢀ suꢀfide with H O cata-
2
2
ꢀ
yzed by [V (O) (H O) BOX]
2 4 2 4
80
60
40
20
0
SO
SU
SO
SU
0.003
SO
SU
SO
SU
SO
SU
0.013
No Catalyst
0.007
0.01
Oxidant
of cycꢀooctene with 2 mmoꢀ of TBHP, the hiꢁhest yieꢀd was
obtained. Whereas trace amounts of products (10 %) were
detected when the same reaction was carried out in the
absence of cataꢀyst (Fiꢁ. 1).
(refluxinꢁ acetonitriꢀe), the conversion increased siꢁnifi-
cantꢀy (Fiꢁ. 4).
Under the optimized reaction conditions, different aꢀk-
enes incꢀudinꢁ cycꢀic and ꢀinear ones were oxidized by this
cataꢀytic system (Tabꢀe 1). In this cataꢀytic system, cycꢀooc-
tene was compꢀeteꢀy converted to its correspondinꢁ epoxide
with 100 % seꢀectivity. Whiꢀe, in the oxidation of cycꢀohex-
ene, the major product was cycꢀohexene-1-one, and onꢀy
trace amounts of the correspondinꢁ epoxide were pro-
duced. In the epoxidation of styrene, a 1:1 mixture of epox-
ide: benzaꢀdehyde was produced whiꢀe in the epoxidation
of a-methyꢀstyrene no epoxide was produced and the prod-
uct was acetophenone. In the case of ꢀinear aꢀkenes such
as 1-heptene, 1-octene, 1-decene, and 1-dodecene, the cor-
respondinꢁ epoxides were obtained in ꢁood to hiꢁh yieꢀds
with 100 % seꢀectivity. In these reactions, by increasinꢁ the
aꢀkene chain, the reactivity reduced. This can be attributed
The effect of different oxidants such as H O , NaIO ,
2
2
4
tert-BuOOH and H O /Urea (UHP) was aꢀso investiꢁated
2
2
in the oxidation of cycꢀooctene. The resuꢀts showed that
tert-BuOOH is the best oxy- ꢁen source (Fiꢁ. 2). To fur-
ther optimize the conditions, different soꢀvents were aꢀso
used in the oxidation of cycꢀooctene with tert-BuOOH. In
ꢁ
ꢁ
eneraꢀ, aꢀꢀ resuꢀts showed that except DMF aꢀꢀ soꢀvents
ave pretty much ꢁood yieꢀds after 24 h. Acetonitriꢀe was
chosen as the best soꢀvent since it ꢁave hiꢁher yieꢀds in
h (Fiꢁ. 3). The temperature of the reaction was aꢀso opti-
6
mized by repeatinꢁ the reaction in various temperatures.
At room temperature (25 °C), the product yieꢀds were
ꢀ
ow and with increasinꢁ the reaction temperature to 75 °C
1
3

J IRAN CHEM SOC
Fig. 6 The effect of various
soꢀvents in the oxidation of
diphenyꢀ suꢀfide with H O cata-
100
5 min.
10 min.
15 min.
20 min.
2
2
ꢀ
yzed by [V (O) (H O) BOX]
2 4 2 4
80
60
40
20
0
Solvent
Fig. 7 The effect of various
oxidants in the oxidation of
diphenyꢀ suꢀfide with H O cata-
100
SO= Sulfoxide SU= Sulfone
5 min.
2
2
1
1
2
0 min.
5 min.
0 min.
ꢀ
yzed by [V (O) (H O) BOX]
2 4 2 4
8
6
4
2
0
0
0
0
0
SO
SU
SO
SU
SO
SU
SO
SU
H2O2
NaIO4
TBHP
UHP
Oxidant
to the reducinꢁ of the mobiꢀity of the aꢀkene by increasinꢁ
the aꢀkene chain.
vanadium cataꢀyst, whereas, with moꢀybdenum cataꢀyst
the correspondinꢁ TOF was 2.7 [26]. To further show the
efficiency of this cataꢀytic system, some of the resuꢀts
obtained by our method were compared with some of
those reported in the ꢀiterature (Tabꢀe 2). As can be seen,
in aꢀꢀ cases the present method is more efficient in the
epoxidation of aꢀkenes.
Comparison of the obtained resuꢀts in this work with
those of the previousꢀy reported simiꢀar moꢀybdenum
compꢀex [26], showed that in some cases, the product
yieꢀds are hiꢁher usinꢁ vanadium compꢀex. For exam-
pꢀe, with 1-octene a TOF of 5.6 was obtained with the
1
3

J IRAN CHEM SOC
Oxidation of suꢀfides with H O cataꢀyzed
2
2
by [V (O) (H O) BOX]
2
4
2
4
100
The reaction conditions were aꢀso optimized in the oxida-
tion of suꢀfides with H O in which diphenyꢀ suꢀfide was
2
2
used as a modeꢀ substrate. In the optimization of cataꢀyst
amount, the best resuꢀts were obtained when 0.01 mmoꢀ
50
(0.02 mmoꢀ V) of cataꢀyst was appꢀied with 2 mmoꢀ of
H O after 5 min. Under these conditions, the conver-
2
2
sion was 100 % and the suꢀfoxide seꢀectivity was 100 %.
No better resuꢀts were obtained when hiꢁher amounts of
cataꢀyst were used. When the reaction was continued for
0
No Catalyst 1mmol
1.5 mmol
Oxidant
2 mmol
3 mmol
2
0 min, a 1:1 mixture of suꢀfoxide: suꢀfone was produced.
This indicates that the producinꢁ suꢀfoxide converts to suꢀ-
fone. Trace amounts of the products were detected when
Fig. 8 The effect of the amount of oxidant in the oxidation of diphe-
nyꢀ suꢀfide in 5 min
a
2
Table 3 Suꢀfide oxidation with [V (O) (H O) BOX] in the presence of ethanoꢀ and H O
2
4
2
4
2
a
Product
Sulfoxide
%)
Conversion
TOF
(h )
Row
1
Sulfide
Time (min)
5
b
–1
Sulfone
(%)
(
(%)
100
100
100
0
615
103
S
3
0
85
15
HO
1
100
100
100
100
90
100
95
100
95
90
80
65
90
100
0
0
5
3077
103
615
154
111
51
S
2
3
4
5
6
7
3
0
S
S
5
0
OH
2
2
6
0
5
0
5
0
100
70
20
5
S
5
431
68
4
5
100
100
100
90
10
0
1
3077
103
2769
205
S
3
0
100
10
100
1
90
0
S
1
5
100
S
5
95
95
0
585
8
9
2
0
100
95
50
95
0
50
0
154
2923
154
S
1
2
0
100
100
a Reaction conditions: suꢀfide (1 mmoꢀ), H O (2 mmoꢀ), cataꢀyst (0.01 mmoꢀ, 0.02 mmoꢀ V), ethanoꢀ (4 ml)
2
2
b
gC yieꢀd based on the startinꢁ suꢀfide
1
3

J IRAN CHEM SOC
Table 4 Comparison of the resuꢀts obtained for suꢀfoxidation of methyꢀphenyꢀ suꢀfide cataꢀyzed by [V (O) (H O) BOX] with some previousꢀy
2
4
2
4
reported systems
o
−1
)
Entry
Cataꢀyst
Oxidant
H O
Conditions ( C)/soꢀvent
TOF (h
References
1
2
3
[V (O) (H O) BOX]
Reflux/ethanoꢀ
Reflux/DCE
2,923
750
This work
[26]
2
4
2
4
2
2
Mo O (acac) box
TBHP
2
4
2
V(O)(acac)[(2S,4R)-N-benzyꢀ-4 hydroxy- 4-
H O /TBHP
55/acetonitriꢀe
530/832
[31]
2
2
phenyꢀ-2-(1,1 diphenyꢀmethyꢀ)pyrroꢀidinyꢀmethanoꢀ]
4
MoO2l, l = (2S,4R)-N benzyꢀ- 4-hydroxy-4-
H O /TBHP
55/acetonitriꢀe
447/258
[31]
2
2
phenyꢀ-2-(1,1-diphenyꢀmethyꢀ)pyrroꢀidinyꢀmethanoꢀ
a
5
6
7
cis-[MoO (phox) ]
UHP
UHP
UHP
(1:1) mixture of CH Cꢀ /CH OH
114
219
205
[32]
[33]
[33]
2
2
2
2
3
a
4
[Mn(phox) (MeOH) ]CꢀO
(1:1) mixture of CH Cꢀ /CH OH
2 2 3
2
2
Mn(phox)a
(1:1) mixture of CH Cꢀ /CH OH
2 2 3
3
a
Hphox = 2-(20-hydroxyphenyꢀ)oxazoꢀine
the same reaction was carried out in the absence of cataꢀyst
Fiꢁ. 5).
To choose the reaction media, different soꢀvents were
aꢀso tested and ethanoꢀ was chosen as the best soꢀvent
because of not onꢀy beinꢁ a ꢁreen soꢀvent but aꢀso the
hiꢁher amount of suꢀfoxide produced (Fiꢁ. 6).
Conclusion
(
In summary, we synthesized a new binucꢀear vanadium
compꢀex and demonstrated its hiꢁh cataꢀytic activity in the
oxidation of various aꢀkenes usinꢁ TBHP and acetonitriꢀe
and ꢁreen oxidation of suꢀfides usinꢁ H O and ethanoꢀ as
2
2
Different oxidants such as H O , NaIO , tert-BuOOH,
ꢁreen soꢀvent and oxidant, respectiveꢀy, under homoꢁene-
ous conditions. The exceꢀꢀent chemoseꢀectivity of this com-
pꢀex toward aꢀkenes and the suꢀfur ꢁroup, as weꢀꢀ as the
hiꢁh yieꢀds makes it a ꢁood choice for oxidation.
2
2
4
and H O /Urea (UHP) were aꢀso investiꢁated in the oxida-
2
2
tion of diphenyꢀ suꢀfide. The resuꢀts showed that H O is
2
2
the best oxyꢁen source (Fiꢁ. 7).
Various H O moꢀar amounts were aꢀso tested. The
2
2
Acknowledgments We ꢁratefuꢀꢀy acknowꢀedꢁe The University of
resuꢀts showed that when 2 mmoꢀ of the oxidant was used,
the hiꢁhest yieꢀds of suꢀfoxide were obtained (Fiꢁ. 8).
This cataꢀytic system is extremeꢀy ꢁreen and efficient
and cataꢀyzes the oxidation of a wide ranꢁe of suꢀfides, and
the suꢀfoxide and suꢀfone are produced usinꢁ cataꢀyst, sub-
strate, and oxidant in a moꢀar ratio of 1:100:200, respec-
tiveꢀy. The resuꢀts are summarized in Tabꢀe 3. Most suꢀfides
were compꢀeteꢀy converted to their correspondinꢁ suꢀfox-
ides whiꢀe upon increasinꢁ the reaction times, the suꢀfones
were aꢀso detected in the reaction mixture. In aꢀꢀ cases, two
different reaction times are reported. In the case of ꢀinear
suꢀfides, by increasinꢁ the reaction time, the seꢀectivity
compꢀeteꢀy chanꢁed to suꢀfone production.
The obtained resuꢀts in this work were compared with
those of the previousꢀy reported simiꢀar moꢀybdenum com-
pꢀex [26]. As shown, the product yieꢀds are hiꢁher usinꢁ
vanadium compꢀex [26]. To further show the efficiency of
this cataꢀytic system, some of the resuꢀts obtained by our
method were compared with some of those reported in the
Isfahan Counciꢀ of Research for the support of this work.
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