Investigation of the catalytic activity of an electron-deficient vanadium(IV) tetraphenylporphyrin: A new, highly efficient and reusable catalyst for ring-opening of epoxides

Article abstract of DOI:10.1016/j.poly.2011.06.008

In this work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V ^IV(TPP)(OTf)₂], in the nucleophilic ring-opening of epoxides is reported. This new V(IV) catalyst was used as an efficient catalyst for alcoholysis with primary (methanol, ethanol and n-propanol), secondary (iso-propanol) and tertiary alcohols (tert-butanol), hydrolysis and acetolysis of epoxides with acetic acid and also for the conversion of epoxides to 1,2-diacetates with acetic anhydride, conversion of epoxides to thiiranes with ammonium thiocyanate and thiourea, and for conversion of epoxides to acetonides with acetone. The catalyst was reused several times without loss of its activity.

Full text of DOI:10.1016/j.poly.2011.06.008

Polyhedron 30 (2011) 2244–2252
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Investigation of the catalytic activity of an electron-deficient vanadium(IV)
tetraphenylporphyrin: A new, highly efficient and reusable catalyst
for ring-opening of epoxides
⇑
⇑
S. Abdolmanaf Taghavi, Majid Moghadam , Iraj Mohammadpoor-Baltork , Shahram Tangestaninejad,
Valiollah Mirkhani, Ahmad Reza Khosropour, Venus Ahmadi
Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746-73441, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
In this work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluorometh-
anesulfonate, [VIV(TPP)(OTf)2], in the nucleophilic ring-opening of epoxides is reported. This new V(IV)
catalyst was used as an efficient catalyst for alcoholysis with primary (methanol, ethanol and n-propa-
nol), secondary (iso-propanol) and tertiary alcohols (tert-butanol), hydrolysis and acetolysis of epoxides
with acetic acid and also for the conversion of epoxides to 1,2-diacetates with acetic anhydride, conver-
sion of epoxides to thiiranes with ammonium thiocyanate and thiourea, and for conversion of epoxides to
acetonides with acetone. The catalyst was reused several times without loss of its activity.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 23 February 2011
Accepted 1 June 2011
Available online 7 July 2011
Keywords:
Homogeneous catalyst
Epoxide
Ring-opening
Vanadium porphyrin
Electron-deficient
1. Introduction
reported the use of chromium and iron porphyrins in organic
synthesis. They used Cr(tpp)Cl for regioselective [3,3]
Epoxides are versatile intermediates in synthetic organic chem-
istry and can be opened under a variety of conditions [1]. The most
practical and widely employed strategy for the synthesis of 1,2-
bifunctional compounds is via nucleophilic ring-opening using a
Lewis acid or a strong base [2–8].
rearrangement of aliphatic allyl vinyl ethers and for the Claisen
rearrangement of simple aliphatic allyl vinyl ethers, Fe(tpp)OTf
for rearrangement of
a,b-epoxy ketones into 1,2-diketones and
rearrangement of monoalkyl-substituted epoxides into aldehydes,
and Cr(tpp)OTf for highly regio- and stereoselective rearrangement
of epoxides to aldehydes [24–30].
Recently, we have reported the use of tetraphenylporphyrinato-
tin(IV) perchlorate [31–33], tetraphenylporphyrinatotin(IV) triflu
oromethanesulfonate [34–39] and tetraphenylporphyrinatotin(IV)
tetrafluoroborate [40–42] in organic transformations.
Epoxide ring-opening reactions to give b-substituted alcohols
with carbon- and heteroatomic nucleophiles, rearrangement reac-
tions providing carbonyl compounds, and isomerization reactions
leading to allylic alcohols are useful tools in organic synthesis. Re-
cently, several reagents have been reported in the literature that
can promote ring opening of epoxides [9–21]. In most of the epox-
ide ring-opening reactions under acidic conditions, the formation
of a mixture of regioisomers and polymerization are observed.
Some of the reported catalysts suffer from disadvantages such as
high acidity, the non-catalytic nature of the reagents, long reaction
times and inconvenient handling [22,23]. Therefore, the introduc-
tion of new methods for the nucleophilic ring-opening of epoxides,
which work under mild conditions, is important in synthetic or-
ganic chemistry.
Vanadium is required for normal health, and could act in vivo
either as a metal cation or as a phosphate analog, depending on
the oxidation state, V(lV) or V(V), respectively. Vanadium in sea
squirt (tunicate), a primitive vertebrate, is concentrated in blood
cells, apparently as the major cellular transition metal, but whe
ther it participates in the transport of dioxygen (as iron and copper
do) is not known. In proteins, vanadium is a cofactor in an algal
bromoperoxidase and in certain prokaryotic nitrogenases. How-
ever, its oxidation state within organisms seems to be highly vari-
able. The biochemistry of vanadium potentially involves four oxid
ation states that are relatively stable in aqueous solution. These are
In the last decade, electron-deficient metalloporphyrins have
been used as mild Lewis acid catalysts. The Suda group has
V2+, V3+, VO2+ and VO2 (the oxidation states 2, 3, 4 and 5, respec-
+
tively) [43]. Contrary to the oxidation states +III and +IV, the hydro-
lysis of vanadium(V) produces almost exclusively anionic species
(the only exception is the pale yellow pervanadyl ion, VO2+, in very
⇑
Corresponding authors. Tel.: +98 311 7932712; fax: +98 311 6689732.
E-mail addresses: moghadamm@sci.ui.ac.ir, majidmoghadamz@yahoo.com
(M. Moghadam), imbaltork@sci.ui.ac.ir (I. Mohammadpoor-Baltork).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.06.008

S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
2245
acidic solutions). The metavanadate ion, (VO3)nnÀ, however, exists
in the solid state only, and when the compound is dissolved in
water, it forms a mixture of mono- and oligovanadates, depending
on the pH, vanadium total concentration and the ionic strength of
the medium [44,45].
In the present work, the catalytic activity of high-valent tetra-
phenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [VIV
(TPP)(OTf)2], in alcoholysis, hydrolysis, acetolysis and for the con-
version of epoxides to 1,2-diacetates with acetic anhydride, for
conversion of epoxides to thiiranes with ammonium thiocyanate
and thiourea, and also for the preparation of 1,3-dioxolanes from
epoxides and acetone is reported (Schemes 1–4).
0.45 lM filter. The resulting solution was evaporated at room
temperature. Then, the [VIV(TPP)(OTf)2] was extracted with CH2Cl2
and crystals were obtained after evaporation of solvent at room
temperature.
Visible spectrum: 456 (Soret), 585, 628 nm;
m (KBr): 1030, 1168,
1224, 1298 cmÀ1 (belong to SO3 groups and porphyrin ring); Anal.
Calc. for CHNS: C, 57.44; H, 2.93; N, 5.83; S, 6.67. Found: C, 57.35;
H, 2.88; N, 5.91; S, 6.65%.
2.2. General procedure for the alcoholysis and acetolysis of epoxides
catalyzed by [VIV(TPP)(OTf)2]
To a solution of epoxide (1 mmol) in the appropriate alcohol or
acetic acid (4 mL), [VIV(TPP)(OTf)2] (0.01–0.02 mmol) was added
and the mixture was stirred for a specified time and at the appro-
priate temperature, according to Tables 1 and 2. The progress of the
reaction was monitored by GC. After completion of the reaction,
the solvent was evaporated, Et2O (10 mL) was added and the cata-
lyst was filtered. The mixture was concentrated under reduced
pressure and chromatographed on a silica gel column to give the
pure product in 80–100% yield.
2. Experimental
Chemicals were purchased from Fluka and Merck chemical
companies. 1H NMR spectra were recorded in CDCl3 solvent on a
Bruker-Avance 400 MHz spectrometer using TMS as an internal
standard. Infrared spectra were run on a Philips PU9716 or Shima-
dzu IR-435 spectrophotometer. All analyses were performed on a
Shimadzu GC-16A instrument with a flame ionization detector
using silicon DC-200 or Carbowax 20M columns. Tetraphenylpor-
phyrin, [VO(TPP)] and [V(TPP)Cl2] were prepared according to the
literature [46–48].
2.3. General procedure for the hydrolysis of epoxides catalyzed by
[VIV(TPP)(OTf)2]
To a solution of epoxide (1 mmol) in an equal mixture of
CH3CN/H2O (v/v, 5 mL), [VIV(TPP)(OTf)2] (0.02 mmol) was added
and the mixture was stirred for the appropriate time under reflux
conditions according to Table 3. The progress of the reaction was
monitored by GC. After completion of the reaction, the solvent
was evaporated, Et2O (10 mL) was added and the catalyst was fil-
tered. The mixture was concentrated under reduced pressure and
chromatographed on a silica gel column to give the pure product
in 92–99% yield.
2.1. Preparation of tetraphenylporphyrinatovanadium(IV)
trifluoromethanesulfonate, [VIV(TPP)(OTf)2]
To a solution of V(TPP)Cl2 (0.97 g, 1 mmol) in THF (50 mL), at
55 °C, AgCF3SO3 (0.54 g, 2 mmol) was added. The solution was stir-
red at 55 °C for 30 min. The AgCl precipitate was filtered through a
R
[VIV(TPP)(OTf)2], Nu:
rt or heat
R
R
2.4. General procedure for conversion of epoxides to 1,2-diacetates
catalyzed by [VIV(TPP)(OTf)2]
or
O
Nu
OH
HO
Nu
To a mixture of epoxide (1 mmol) in CH3CN (0.5 mL), Ac2O
(0.5 mL) and [VIV(TPP)(OTf)2] (1 mol%) were added and the mixture
was stirred under reflux conditions. After completion of the reac-
tion, as indicated by GC, the solvent was evaporated; Et2O was
added (20 mL) and the catalyst was filtered. Evaporation of the sol-
vent followed by chromatography on a short column of silica gel
afforded the pure 1,2-diacetate in high yield.
Nu: ROH, H2O, AcOH
Scheme 1. Alcoholysis, acetolysis and hydrolysis of epoxides.
R
R
[VIV(TPP)(OTf)2]
O
2.5. General procedure for conversion of epoxides to thiiranes with
NH4SCN or H2NCSNH2 in the presence of [VIV(TPP)(OTf)2
Ac2O/CH3CN
rt or heat
AcO
OAc
In a round-bottomed flask (25 mL) equipped with a condenser
and a magnetic stirrer, a mixture of epoxide (1 mmol), ammonium
thiocyanate or thiourea (2 mmol) in acetonitrile (4 mL) was pre-
pared. [VIV(TPP)(OTf)2] (0.01 mmol for ammonium thiocyanate
and 0.01–0.02 mmol for thiourea) was added to this solution and
the reaction mixture was stirred magnetically under reflux condi-
tions. After completion of the reaction (monitored by GC), the sol-
vent was evaporated, Et2O (10 mL) was added and the catalyst was
filtered. Evaporation of the solvent followed by chromatography on
a short column of silica gel gave pure thiirane.
Scheme 2. Conversion of epoxides to 1,2-diacetates.
R
R
[VIV(TPP)(OTf)2], CH3CN
O
S
NH4SCN or H2NCSNH2 / heat
Scheme 3. Conversion of epoxides to thiiranes.
R
2.6. General procedure for conversion of epoxides to 1,3-dioxolanes
catalyzed by [VIV(TPP)(OTf)2]
R
[VIV(TPP)(OTf)2], acetone
O
O
Me
O
rt or heat
In a round-bottomed flask (25 mL) equipped with a condenser
and a magnetic stirrer, a solution of epoxide (1 mmol) in acetone
(5 mL) was prepared. [VIV(TPP)(OTf)2] (0.015 mmol) was added to
Me
Scheme 4. Conversion of epoxides to 1,3-dioxolanes.

2246
S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
Table 1
Alcoholysis of epoxides catalyzed by [VIV(TPP)(OTf)2].a
Entry
Epoxide
ROH/condition
Wcat (g)
Time (min)
Product/yield (%)b,c
Selectivity (%)
TOF (hÀ1
)
OR
O
OH
1
2
3
4
5
R = CH3/R.T.
R = C2H5/R.T.
R = n-Pr/R.T.
R = i-Pr/R.T.
R = t-Bu/Ref.
0.005
0.005
0.005
0.005
0.01
6
6
25
90
4
100
100
96
100
100
100
100
100
100
100
2000.0
2000.0
460.8
133.3
1500.0
O
OR
OH
6
7
8
9
R = CH3/R.T.
R = C2H5/R.T.
R = n-Pr/R.T.
R = i-Pr/Ref.
R = t-Bu/Ref.
0.005
0.005
0.005
0.005
0.005
5
5
8
10
15
100
99
99
96
90
100
100
100
100
100
2400.0
2376.0
1485.0
1152.0
720.0
10
Cl
OH
O
Cl
OR
11
12
13
14
15
R = CH3/Ref.
R = C2H5/Ref.
R = n-Pr/Ref.
R = i-Pr/Ref.
R = t-Bu/Ref.
0.015
0.015
0.02
0.02
0.02
90
80
55
70
60
88
92
99
92
91
100
100
100
100
100
39.1
46.0
54.0
39.4
45.5
OH
O
O
O
OR
16
17
18
19
20
R = CH3/Ref.
R = C2H5/Ref.
R = n-Pr/Ref.
R = i-Pr/Ref.
R = t-Bu/Ref.
0.005
0.005
0.005
0.005
0.005
5
86
85
100
99
90
100
100
100
100
100
2064.0
1020.0
800.0
297.0
270.0
10
15
40
40
O
OR
OH
21
22
23
24
25
R = CH3/R.T.
R = C2H5/Ref.
R = n-Pr/Ref.
R = i-Pr/Ref.
R = t-Bu/Ref.
0.01
0.01
0.01
0.01
0.01
15
3
5
10
35
100
99
99
95
96
100
100
100
100
100
400.0
1980.0
1188.0
570.0
164.6
O
OH
O
O
OR
26
27
28
29
30
R = CH3/Ref.
R = C2H5/Ref.
R = n-Pr/Ref.
R = i-Pr/Ref.
R = t-Bu/Ref.
0.01
0.01
0.015
0.015
0.01
15
15
15
20
97
95
98
85
97
100
100
100
100
100
388.0
380.0
261.3
170.0
52.9
110
OH
O
O
O
OR
31
32
33
34
35
R = CH3/Ref.
R = C2H5/Ref.
R = n-Pr/Ref.
R = i-Pr/Ref.
R = t-Bu/Ref.
0.015
0.015
0.015
0.015
0.015
15
15
15
30
40
99
97
95
98
95
100
100
100
100
100
264.0
258.7
253.3
130.7
95.0
a
b
c
Reaction conditions: epoxide (1 mmol), alcohol (4 mL), catalyst.
All products were identified by comparison of their physical and spectral data with those of authentic samples [13,15].
Yields refer to GC yields.
this solution and the reaction mixture was stirred magnetically
under reflux conditions or at room temperature. The reaction pro-
gress was monitored by GC. After completion of the reaction, the
solvent was evaporated, Et2O (10 mL) was added and the catalyst
was filtered. The solvent was evaporated under reduced pressure
and the crude product was obtained in a quantitative yield. Distil-
lation of the product under reduced pressure resulted the corre-
sponding 1,3-dioxolane in 75–92% yield.

S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
2247
Table 2
Acetolysis of various epoxides catalyzed by [VIV(TPP)(OTf)2].a
Entry
1
Epoxide
Time (min)/condition
Productb
Yield (%)c
86
Selectivity (%)
100
TOF (hÀ1
)
5/R.T.
688.0
O
OAc
OAc
OH
2
15/R.T.
94
100
250.7
O
OH
3
4
35/Ref.
15/Ref.
96
98
100
100
109.7
261.3
Cl
OH
O
Cl
OAc
O
OH
O
O
OAc
OAc
5
6
10/Ref.
35/Ref.
98
98
100
100
392.0
112.0
O
OH
OH
O
O
O
OAc
7
25/Ref.
98
100
156.8
OH
O
O
O
OAc
a
b
c
Reaction conditions: epoxide (1 mmol), acetic acid (4 mL), catalyst (1.5 mol%).
All products were identified by comparison of their physical and spectral data with those of authentic samples [13,15].
Yields refer to GC yields.
Table 3
Hydrolysis of epoxides catalyzed by [VIV(TPP)(OTf)2].a
Entry
1
Epoxide
Time (min)/condition
5/Ref.
Productb
Yield (%)c
99
TOF (hÀ1
594.0
)
O
OH
OH
OH
2
30/R.T.
98
98.0
O
OH
OH
3
4
100/Ref.
120/Ref.
99
90
29.7
22.5
Cl
O
Cl
OH
OH
O
O
O
OH
5
6
35/Ref.
92
92
78.8
18.4
O
OH
OH
OH
150/Ref.
O
O
O
O
OH
7
100/Ref.
96
28.8
OH
O
O
OH
a
b
c
Reaction conditions: epoxide (1 mmol), CH3CN (2.5 mL), H2O (2.5 mL), catalyst (2 mol%).
All products were identified by comparison of their physical and spectral data with those of authentic samples [13,15].
Yields refer to GC yields.

2248
S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
ether, isopropyl oxiranylmethyl ether and 1,2-epoxyoctane were
3. Results and discussion
subjectedto alcoholysiswith primary (methanol, ethanol and n-pro-
panol), secondary (iso-propanol) and tertiary (tert-butanol) alco-
hols, and the corresponding b-alkoxy alcohols were obtained in
high yields (80–100%). The results are summarized in Table 1. In
the case of cyclohexene oxide, the reactions were stereoselective,
and only trans-products were obtained (entries 1–5).
3.1. Alcoholysis, hydrolysis and acetolysis of epoxides catalyzed by
[VIV(TPP)(OTf)2]
Scheme 5 shows the preparation route for [VIV(TPP)(OTf)2]. Fig. 1
shows the UV–Vis spectrum of this catalyst, in which three bands at
456 (Soret band), 585 and 628 nm (Q bands) were observed. Since
V(IV) is an electron-deficient species, we decided to investigate
the catalytic activity of this new catalyst for the nucleophilic ring-
opening of epoxides. First, the catalytic activity of different vana-
dium(IV) porphyrins, such as [VIVO(TPP)], [VIV(TPP)Cl2] and [VIV
(TPP)(OTf)2], were investigated in the methanolysis of styrene oxide.
The results showed that the catalytic activity of the catalysts, using
equal amounts of catalysts, is as following:[VIV (TPP)(OTf)2]
(100%) > [VIV(TPP)Cl2] (43%) > [VIVO(TPP)] (12%). These observa-
tions show that introducing of triflate groups on the porphyrin moi-
ety increases the electron-deficiency of V(IV) species, which in turns
increases the catalytic activity of [VIV(TPP)(OTf)2] toward ring-open-
ing of epoxides.
In the case of unsymmetrical epoxides, the reactions were regio-
selective, and the attack of the nucleophile (alcohol) on the less
substituted oxirane carbon yielded the anti-Markovnikov type prod-
ucts (entries 11–35). The only exception is the alcoholysis of styrene
oxide, in which the reactions occur on the more substituted carbon
and the Markovnikov type products were produced (entries 6–10). In
the case of active epoxides and when the alcohol has higher nucleo-
philicity, the reactions were carried out at room temperature.
Although the actual mechanism of these reactions is not clear at
present, due to the high oxophilicity of the vanadium active site,
the most probable interaction is the activation of epoxide by
[VIV(TPP)(OTf)2] to afford 1. Alcohol attacks 1 to give 2, which in
turns converts to the final product and releases the catalyst for
the next catalytic cycle (Scheme 6). It seems that the mechanism
is similar to that of tin(IV) porphyrins [34,41].
Therefore, the [VIV(TPP)(OTf)2] (0.5–2 mol%) was chosen as the
catalyst for alcoholysis of epoxides. In this manner, aliphatic, alicy-
clic, activated and deactivated epoxides such as styrene oxide,
cyclohexene oxide, (chloromethyl)oxirane, allyl oxiranylmethyl
When acetic acid was used instead of alcohols, b-acetoxy alco-
hols were produced in high yields (86–98%) in the presence of a
O
N
N
N
N
V
SOCl2, CH2Cl2
Cl
N
N
N
N
V
Cl
o
THF, 60 C
AgOTf, 0.5 h
OTf
N
N
N
V
AgCl +
N
OTf
Scheme 5. The preparation route for [VIV(TPP)(OTf)2].

S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
2249
R
O
R
OTf
O
V
IV
V
IV
OTf
OTf
1
Fig. 1. UV–Vis spectrum of [VIV(TPP)(OTf)2].
R
R
catalytic amount (1.5 mol%) of [VIV(TPP)(OTf)2] (Table 2). Conver-
sion of the epoxides to 1,2-diols was also performed in aqueous
acetonitrile in the presence of 2 mol% of [VIV(TPP)(OTf)2] (Table
3). In these reactions, the diols were obtained in excellent yields
(90–99%).
H+
ROH
O
OR
HO
OR
IV
V
OTf
The most important advantages of this catalyst is that in all
cases the product selectivity is 100%, while by using other Lewis
acids in the alcoholysis of epoxides, two products have been de-
tected in the reaction mixture.
2
Scheme 6. The proposed mechanism for the ring opening of epoxides.
was investigated in the presence of [VIV(TPP)(OTf)2] (1 mol%). In
this manner, different epoxides were efficiently converted to their
corresponding 1,2-diacetates in good to excellent yields (Table 4).
The ring opening of epoxides with Ac2O by internal or external at-
tack of the nucleophile afforded similar products.
3.2. Conversion of epoxides to 1,2-diacetates with Ac2O catalyzed by
[VIV(TPP)(OTf)2]
1,2-Diacetates bearing easily removable protecting groups are
the most important intermediates in the synthesis of natural prod-
ucts [49,50], particularly for carbohydrates and steroid chemistry
[51,52]. In addition, these compounds are of interest in the manu-
facturing of pharmaceuticals and fragrances [53–56]. Therefore,
the conversion of epoxides to 1,2-diacetates with acetic anhydride
3.3. Conversion of epoxides to thiiranes catalyzed by [VIV(TPP)(OTf)2]
Conversion of epoxides to thiiranes with a sulfur-containing re-
agent such as NH4SCN and thiourea in the presence of a suitable
Table 4
Conversion of epoxides to 1,2-diacetates with acetic anhydride catalyzed by [VIV(TPP)(OTf)2] in refluxing acetonitrile.a
Entry
1
Epoxide
Productb
Time (h)
1.5
Conversion (%)c
90
TOF (hÀ1
60.0
)
O
OAc
OAc
2
3
1.5
2
99
86
66.0
43.0
OAc
OAc
O
O
OAc
O
O
OAc
4
5
2.5
3
82
80
32.8
26.7
O
OAc
OAc
OAc
O
OAc
O
O
O
O
6
2
85
42.5
O
OAc
OAc
a
b
c
Reaction conditions: epoxide (1 mmol), Ac2O (0.5 mL), CH3CN (0.5 mL), catalyst (1 mol%).
All products were identified by comparison of their physical and spectral data with those of authentic samples [52,53].
Yields refer to GC yields.

2250
S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
catalyst under non-aqueous conditions is important in organic
chemistry [57–61]. Different aliphatic and cyclic epoxides bearing
different substituents were efficiently converted to their
corresponding thiiranes with NH4SCN or thiourea in refluxing ace-
tonitrile. The results are summarized in Table 5. The effect of other
solvents such as acetone, dichloromethane, chloroform and carbon
Table 5
Conversion of epoxides to thiiranes with NH4SCN and NH2CSNH2 catalyzed by [VIV(TPP)(OTf)2] in refluxing acetonitrile.a
Entry
1
Epoxide
NH4SCN
Wcat (g)
0.01
NH2CSNH2
Wcat (g)
0.01
Product
Time (min)
15
Yield (%)b
96
Time (min)
45
Yield (%)b
95
O
S
2
0.01
12
99
0.01
30
95
S
O
3
4
0.01
0.01
12
15
95
93
0.02
0.02
90
30
92
95
Cl
Cl
Cl
O
S
S
S
O
5
6
0.01
0.01
12
10
96
99
0.02
0.01
90
30
94
95
O
S
O
O
S
S
O
O
O
O
7
0.01
20
97
0.02
30
95
a
Reaction conditions: epoxide (1 mmol), catalyst, NH4SCN or NH2CSNH2 (2 mmol), CH3CN (5 mL).
Yields refer to GC yields.
b
Table 6
Conversion of epoxides to acetonides catalyzed by [VIV(TPP)(OTf)2].a
Entry
1
Epoxide
Condition
Time (min)
Conversion (%)c
Selectivity (%)
TOF (hÀ1
)
Productb
R.T.
Reflux
50
5
90
92
100
72.0
736.0
Me
O
O
Me
O
2
3
R.T.
45
93
75
100
100
82.7
20.0
Me
Me
O
O
O
Reflux
150
Me
Cl
O
O
Me
Cl
O
Me
O
4
Reflux
190
87
100
18.3
O
Me
O
O
O
5
6
Reflux
Reflux
210
240
90
90
100
100
17.1
15.0
Me
O
O
Me
O
Me
O
O
O
Me
O
O
O
7
Reflux
200
92
100
18.4
Me
O
O
O
Me
O
a
b
c
Reaction conditions: epoxide (1 mmol), CH3COCH3 (5 mL), catalyst (1.5 mol%).
All products were identified by comparison of their physical and spectral data with those of authentic samples [34].
Yields refer to GC yields.

S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
2251
Table 7
Comparison of the results obtained for the methanolysis of epoxides catalyzed by [VIV(TPP)(OTf)2] with those obtained by recently reported catalysts.
OH
Catalyst
O
PhO
PhO
OMe
Entry
Catalyst
Catalyst (mol%)
Temperature
Time (min)
Yield (%)
TOF (hÀ1
)
Ref.
1
2
3
4
5
6
7
8
[VIV(TPP)(OTf)2]
AlPW12O40
(NH4)8[CeW12O36
Fe(III)-montmorillonite
FeCl3
Ce(OTf)4
1
3
4
Reflux
R.T.
Reflux
R.T.
65 °C
Reflux
R.T.
15
15
10
90
94
95
85
95
93
90
100
94
98
99
99
95
388.00
125.33
142.50
[9]
]
[10]
[11]
[12]
[13]
[14]
[17]
[18]
[19]
[20]
[34]
[41]
0.2 g
15
5
0.01 g
5
10
10
0.75
2
120
180
20
360
15
120
90
20
2.11
55.80
Fe(III)-polymer
K5[CoW12O40
Fe(TFA)3
BiCl3
]
R.T.
80.00
4.70
14.70
396.00
626.26
285.00
9
65 °C
Reflux
Reflux
Reflux
Reflux
10
11
12
13
ZrO(OTf)2
[SnIV(TPP)(OTf)2]
[SnIV(TPP)(BF4)2]
5
10
2
tetrachloride was also investigated. Compared to acetonitrile, the
reaction times were longer and the yields of thiiranes were lower
in all of the other solvents.
addition, in the presence of this catalyst, efficient conversion of
epoxides to their corresponding thiiranes and acetonides was also
performed. The obtained results clearly show that replacing Cl
with OTf makes [VIV(TPP)(OTf)2] a highly efficient Lewis acid which
can catalyze reactions that [VIV(TPP)Cl2] was not able to catalyze.
Finally the catalyst was reused several times without loss of its
activity. It is also noteworthy that in comparison with most of
the reported methods for the ring-opening of epoxides, the present
method is superior in terms of yields, reaction times and the
amounts of catalyst.
3.4. Conversion of epoxides to acetonides catalyzed by [VIV(TPP)(OTf)2]
1,3-Dioxolanes are widely used as protecting groups for car-
bonyl compounds [62]. These compounds are useful intermediates,
especially in carbohydrate and steroid chemistry. Direct conver-
sion of an epoxide into 1,3-dioxolane, instead of adding water to
form a diol, with subsequent elimination in the presence of ace-
tone has been studied with relatively few reagents [63–66]. There-
fore, direct synthesis of acetonides form epoxides and acetone in
the presence of [VIV(TPP)(OTf)2] was also performed. In this man-
ner, different aliphatic and cyclic epoxides were reacted with
refluxing acetone (except for cyclohexene and styrene oxides
which were carried out at room temperature) in the presence of
1.5 mol% of [VIV(TPP)(OTf)2], and the corresponding 1,3-dioxolanes
were obtained in excellent yields (Table 6).
In order to show the effectiveness of the presented method in
the ring-opening of epoxides, the obtained results in the methan-
olysis of 2,3-epoxypropylphenyl ether in the presence of [VIV(TP-
P)(OTf)2] was compared to some of the methods reported in the
literature (Table 7). Although most of the Lewis acids of these other
methods are cheaper than [VIV(TPP)(OTf)2], in most cases our re-
ported catalyst has a higher TOF in the ring-opening reactions.
Acknowledgement
We are thankful to the Center of Excellence of Chemistry of Uni-
versity of Isfahan (CECIU) for financial support of this work.
References
[1] J.G. Smith, Synthesis (1984) 629.
[2] H. Sharghi, Ali M. Nasseri, K. Niknam, J. Org. Chem. 66 (2001) 7287.
[3] D.M. Hodgson, A.R. Gibbs, G.P. Lee, Tetrahedron 52 (1996) 14361.
[4] I. Paterson, D.J. Berrisford, Angew. Chem., Int. Ed. Engl. 31 (1992) 1180.
[5] S.K. Taylor, Tetrahedron 56 (2000) 1149.
[6] R.E. Parker, N.S. Isaacs, Chem. Rev. 59 (1959) 737.
[7] A.S. Rao, S.K. Paknikar, J.G. Kirtane, Tetrahedron 39 (1983) 2323.
[8] N. Iranpoor, I. Mohammadpour-Baltork, Synth. Commun. 20 (1990) 2789.
[9] H. Firouzabadi, N. Iranpoor, A.A. Jafari, S. Makarem, J. Mol. Catal. A: Chem. 250
(2006) 237.
[10] V. Mirkani, S. Tangestaninejad, B. Yadollahi, L. Alipanah, Tetrahedron 59 (2003)
8213.
[11] B.M. Cheudary, Y. Sudha, Synth. Commun. 26 (1996) 2989.
[12] N. Iranpoor, P. Salehi, Synthesis (1994) 1152.
3.5. Catalyst reusability
[13] N. Iranpoor, M. Shekarriz, F. Shiriny, Synth. Commun. 28 (1998) 347.
[14] R.V. Yarapathi, S.M. Reddy, S. Tammishetti, React. Funct. Polym. 64 (2005) 157.
[15] J. Barluenga, H. Vazquez-Villa, A. Ballesteros, J. Gonzalez, Org. Lett. 4 (2002)
2817.
[16] K. Fagnou, M. Lautens, Org. Lett. 2 (2000) 2319.
[17] S. Tangestaninejad, M. Moghadam, V. Mirkhani, B. Yadollahi, S.M.R.
Mirmohammadi, Monat. Fur Chem. 137 (2006) 235.
[18] N. Iranpoor, H. Adibi, Bull. Chem. Soc. Jpn. 73 (2000) 675.
[19] I. Mohammadpoor-Baltork, S. Tangestaninejad, H. Aliyan, V. Mirkhani, Synth.
Commun. 30 (2000) 2365.
[20] M. Moghadam, I. Mohammadpoor-Baltork, S. Tangestaninejad, V. Mirkhani, L.
Shariati, M. Babaghanbari, M. Zarea, J. Iran. Chem. Soc. 6 (2009) 789.
[21] E.N. Jacobsen, F. Kakiuchi, R.G. Konsler, J.F. Larrow, M. Tokunaga, Tetrahedron
Lett. 38 (1997) 773.
The reusability of the catalyst was checked in the methanolysis
of styrene oxide. At the end of each reaction, the solvent was evap-
orated, Et2O was added and the catalyst was filtered. Then, the cat-
alyst was used with fresh styrene oxide and methanol. The
obtained results showed that after using the catalyst several times
(five consecutive times were checked), the corresponding 2-meth-
oxy-2-phenylethanol was obtained without any decrease in its
yield.
4. Conclusion
[22] G.A. Olah, A.P. Fung, D. Mieder, Synthesis (1981) 280.
[23] G.H. Posner, D.Z. Rogers, C.H. Kinzig, G.M. Gurria, Tetrahedron Lett. 16 (1975)
3597.
[24] K. Suda, M. Sashima, M. Izutsu, F. Hino, J. Chem. Soc., Chem. Commun. (1994)
949.
In conclusion, [VIV(TPP)(OTf)2] was used as a mild Lewis acid for
the efficient ring-opening of epoxides with different nucleophiles
under both solvolytic and non-solvolytic reaction conditions. In
[25] T. Takanami, R. Hirabe, M. Ueno, F. Hino, K. Suda, Chem. Lett. (1996) 1031.

2252
S.A. Taghavi et al. / Polyhedron 30 (2011) 2244–2252
[26] T. Takanami, M. Hayashi, K. Iso, H. Nakamoto, K. Suda, Tetrahedron 62 (2006)
9467.
[44] D. Rehder, in: H. Sigel, A. Sigel (Eds.), Metal ions in Biological Systems, vol. 31,
Marcel Dekker, New York, 1995 (Chapter 1).
[27] T. Takanami, M. Hayashi, K. Suda, Tetrahedron Lett. 46 (2005) 2893.
[28] K. Suda, K. Baba, S. Nakajima, T. Takanami, Chem. Commun. (2002) 2570.
[29] K. Suda, K. Baba, S. Nakajima, T. Takanami, Tetrahedron Lett. 40 (1999) 7243.
[30] K. Suda, T. Kikkawa, S. Nakajima, T. Takanami, J. Am. Chem. Soc. 126 (2004)
9554.
[31] S. Tangestaninejad, V. Mirkhani, Synth. Commun. 29 (1999) 2079.
[32] S. Tangestaninejad, M.H. Habibi, V. Mirkhani, M. Moghadam, J. Chem. Res. (S)
(2001) 365.
[33] S. Tangestaninejad, M.H. Habibi, V. Mirkhani, M. Moghadam, Synth. Commun.
32 (2002) 1337.
[34] M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork, R.
Shaibani, J. Mol. Catal. A: Chem. 219 (2004) 73.
[35] M. Moghadam, S. Tangestaninejad, V. Mirkhani, R. Shaibani, Tetrahedron 60
(2004) 6105.
[36] S. Gharaati, M. Moghadam, S. Tangestaninejad, V. Mirkhani, I.
Mohammadpoor-Baltork, F. Kosari, Inorg. Chim. Acta 363 (2010) 1995.
[37] M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork, S.
Gharaati, Appl. Organomet. Chem. 23 (2009) 446.
[38] M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork, S.
Gharaati, Inorg. Chim. Acta 363 (2010) 1523.
[39] M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork, M.
Khajehzadeh, F. Kosari, M. Araghi, Polyhedron 29 (2010) 238.
[40] M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork,
S.A. Taghavi, J. Mol. Catal. A: Chem. 274 (2007) 217.
[45] L. Pettersson, K. Elvingson, in: A.S. Tracey, D.C. Crans (Eds.), Vanadium
Compounds: Chemistry, Biochemistry and Therapeutic Applications, ACS
Symposium Series, vol. 711, ACS Publications, Washington, DC, 1998
(Chapter 2).
[46] A.D. Adler, F.R. Longo, J.D. Finarelli, J. Goldmacher, J. Assour, L. Korsakoff, J. Org.
Chem. 32 (1976) 476.
[47] S. Bencosme, M. Labady, C. Romero, Inorg. Chim. Acta 123 (1986) 15.
[48] P. Richard, J.L. Poncet, J.M. Barbe, R. Guilard, J. Goulon, D. Rinaldi, A. Cartier, P.
Tola, J. Chem. Soc., Dalton Trans. (1982) 1451.
[49] K.G. Watson, Y.M. Fung, M. Gredley, G.J. Bird, W.R. Jackson, H. Gountzos, V.
Mattews, Chem. Commun. (1990) 1018.
[50] H.C. Kulb, K.B. Sharpless, Tetrahedron 48 (1992) 10515.
[51] F.A. Meskens, Synthesis (1981) 501.
[52] B.A.B. Prasad, G.V. Sekar, K. Sigh, Tetrahedron Lett. 41 (2000) 4677.
[53] M. Tokunaga, J.F. Larrow, F. Kakiuchi, E.N. Jacobsen, Science 277 (1997) 936.
[54] R.H. Fan, X.L. Hou, Tetrahedron Lett. 44 (2003) 4411.
[55] N. Azizi, B. Mirmashhori, M.R. Saidi, Catal. Commun. 8 (2007) 2198.
[56] B. Das, V.S. Reddy, F. Tehseen, Tetrahedron Lett. 47 (2006) 6865.
[57] I. Mohammadpoor-Baltork, A.R. Khosropour, Ind. J. Chem. 38B (1999) 605.
[58] N. Iranpoor, B. Zaynizadeh, Synth. Commun. 28 (1998) 3913.
[59] B. Tamami, A.R. Kiasat, Synth. Commun. 26 (1996) 3953.
[60] N. Iranpoor, F. Kazemi, Synthesis (1996) 821.
[61] N. Iranpoor, F. Kazemi, Tetrahedron 53 (1997) 11377.
[62] T.H. Green, P.G.M. Wuts, in: Protective Groups in Organic Synthesis, second
ed., Wiley, New York, 1991, pp. 188–195.
[63] R.P. Hanzlik, M. Leinwetter, J. Org. Chem. 43 (1978) 438.
[64] I. Mohammdpoor-Baltork, A.R. Khosropour, H. Aliyan, Synth. Commun. 31
(2001) 3411.
[41] M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork,
S.A. Taghavi, Catal. Commun. 8 (2007) 2087.
[42] M. Moghadam, S. Tangestaninejad, V. Mirkhani, I. Mohammadpoor-Baltork, S.
Gharaati, Polyhedron 29 (2010) 212.
[43] I. Bertini, H.B. Gray, S.J. Lippard, J.S. Valentine, Bioinorganic Chemistry,
University Science Books, 1994.
[65] N. Iranpoor, B. Zaynizadeh, J. Chem. Res. (S) (1998) 466.
[66] F. Kazemi, A.R. Kiasat, S. Ebrahimi, Synth. Commun. 35 (2005) 1441.