Oxidation of 2-imidazolines to 2-imidazoles with sodium periodate catalyzed by polystyrene-bound manganese(III) porphyrin

Article abstract of DOI:10.1016/j.poly.2011.02.040

In the present work, the dehydrogenation of 2-substituted imidazolines with sodium periodate in the presence of tetraphenylporphyrinatomanganese(III) chloride supported on polystyrene-bound imidazole, [Mn(TPP)Cl@PSI] is reported. A wide variety of 2-imidazolines were efficiently converted to their corresponding imidazoles by the [Mn(TPP)Cl@PSI]/NaIO₄ catalytic system in a 1:2 CH₃CN/H₂O mixture under agitation with magnetic stirring. Ultrasonic irradiation enhanced the catalytic activity of this catalyst in the oxidation of 2-imidazolines and this led to shorter reaction times and higher product yields. This catalyst could be reused several times without significant loss of its catalytic activity.

Full text of DOI:10.1016/j.poly.2011.02.040

Polyhedron 30 (2011) 1463–1468
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Oxidation of 2-imidazolines to 2-imidazoles with sodium periodate catalyzed
by polystyrene-bound manganese(III) porphyrin
b
b
b
Hadi Kargar a, , Majid Moghadam , Valiollah Mirkhani , Shahram Tangestaninejad ,
⇑
Iraj Mohammadpoor-Baltork b, Mahmood Naghipour a
a Chemistry Department, Payame Noor University, Tehran 19395-4697, Islamic Republic of Iran
b Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Islamic Republic of Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
In the present work, the dehydrogenation of 2-substituted imidazolines with sodium periodate in the
presence of tetraphenylporphyrinatomanganese(III) chloride supported on polystyrene-bound imidazole,
[Mn(TPP)Cl@PSI] is reported. A wide variety of 2-imidazolines were efficiently converted to their corre-
sponding imidazoles by the [Mn(TPP)Cl@PSI]/NaIO4 catalytic system in a 1:2 CH3CN/H2O mixture under
agitation with magnetic stirring. Ultrasonic irradiation enhanced the catalytic activity of this catalyst in
the oxidation of 2-imidazolines and this led to shorter reaction times and higher product yields. This
catalyst could be reused several times without significant loss of its catalytic activity.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 3 January 2011
Accepted 16 February 2011
Available online 3 March 2011
Keywords:
Manganese(III) porphyrin
Supported catalyst
Ultrasonic irradiation
Imidazolines
Imidazoles
1. Introduction
microwave-assisted in the presence of MnO2 [36] and the homoge-
neous Mn(TPP)Cl/NaIO4 catalytic system [37] have been previously
Cytochrome P-450 is an iron porphyrin surrounded by proteins
which can selectively catalyze a wide range of oxidation reactions
[1]. Synthetic metalloporphyrins, as models for cytochrome P-450,
have been found as highly efficient and homogeneous catalysts in
reported for this purpose. Some of these reagents suffer from lim-
itations such as low yields of the products, very long reaction
times, toxicity, the use of a large excess of the reagents and harsh
reaction conditions. Also, some of these reagents are not effective
for the oxidation of 2-alkylimidazolines. Therefore, the develop-
ment of a novel, mild and efficient method for the oxidation of
2-imidazolines to their corresponding imidazoles is of great
interest.
Over the last two decades, several homogeneous and heteroge-
nized metalloporphyrins have been developed for the oxidation of
organic compounds [38–53]. Previously, we have reported the use
of supported manganese(III) porphyrins in the oxidation of organic
compounds with NaIO4 [54–63]. Here, dehydrogenation of 2-
substituted imidazolines to 2-imidazoles in the presence of
tetraphenylporphyrinatomanganese(III) chloride supported on
chloromethylated polystyrene-bound imidazole, [Mn(TPP)Cl@PSI]
with NaIO4 under mechanical stirring (MS) and ultrasonic irradia-
tion (US) conditions is reported (Scheme 1).
the oxidation of organic compounds [2–8] in the presence of a sin-
gle oxygen atom donor, such as PhIO, ClOÀ, H2O2, ROOH and IO4
.
À
These reactions reveal some information about the mechanism of
the cytochrome P-450 monooxygenation enzyme [9–14]. One ma-
jor drawback associated with these homogeneous catalysts is their
degradation in reaction media, a result of which is they cannot be
recovered. One way to overcome this disadvantage is their immo-
bilization on solid supports [15–19].
Oxidation of 2-imidazolines to their corresponding imidazoles
is biologically and pharmaceutically very important, since many
imidazole derivatives possess antihypertensive, antiinflammatory,
antibacterial and antidiabetic activities [20]. 2-Imidazolines can
be easily prepared from nitriles and ethylenediamine [21,22].
Dehydrogenation of 2-imidazolines by an oxidizing agent should
provide an efficient method for the preparation of imidazole deriv-
atives. Several reagents such as Zn–Al2O3 [23], Ni [24], Se [25], Pd/C
[26], MnO2 [27], BaMnO4 [28], DMSO [29], KMnO4@SiO2 [30],
KMnO4@K10 [31], KMnO4@Al2O3 [32], trichloroisocyanuric acid
[33], KMnO4-refluxing dioxane [34], activated carbon–O2 [35],
2. Experimental
All materials were of commercial reagent grade. All materials
were purchased from Merck. Tetraphenylporphyrin was prepared,
metallated and supported according to a reported procedure
[56,64]. All the 2-substituted imidazolines were synthesized by
⇑
Corresponding author. Tel.: +98 352 7220011; fax: +98 352 7228110.
E-mail addresses: hkargar@pnu.ac.ir, majidmoghadamz@yahoo.com (H. Kargar).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.02.040

1464
H. Kargar et al. / Polyhedron 30 (2011) 1463–1468
zene, 4–5% Cl content, 1.14–1.40 mmol/g Cl) was treated with an
N
N
Mn(TPP)Cl@PSI, NaIO4
appropriate quantity of imidazole in refluxing acetonitrile for
48 h [65]. The PSI was characterized by elemental analysis. The
nitrogen content of this resin was 2.06%. According to this value,
the degree of imidazole, which was introduced into the polymer
composition, was 0.736 mmol/g of support. This shows that only
53–64% of the total chlorines were substituted by imidazole.
R
R
CH3CN/H2O
N
H
N
H
.
MS or
)
)
))
1a-j
2a-j
Scheme 1. Oxidation of imidazolines with sodium periodate catalyzed by
[Mn(TPP)Cl@PSI].
3.2. Preparation and characterization of the catalyst, [Mn(TPP)Cl@PSI]
The supported catalyst was prepared by stirring a suspension of
the support (PSI) in a solution of Mn(TPP)Cl in toluene, because of
better solvation and swelling of the polymer in it. The free manga-
nese porphyrin was removed by subsequent washing of the cata-
lyst with toluene, dichloromethane and acetone, respectively. The
reflectance of the [Mn(TPP)Cl@PSI] clearly indicated the presence
of manganese porphyrin on the polymer surface. The manganese
content of the supported catalyst, determined by neutron activa-
tion analysis (NAA), showed a value of about 0.024 mmol/g.
In order to ascertain the attachment of the metalloporphyrin on
the support, the IR spectra of PSI and [Mn(TPP)Cl@PSI] were re-
corded. The sharp CACl peak (due to ACH2Cl groups) at 1264 cmÀ1
in the starting polymer was practically omitted or was seen as a
weak band after introduction of imidazole and manganese(III) por-
phyrin on the polymer. The C@N vibration band of imidazole group
appeared at 1601 cmÀ1, which is an indication of the introduction of
the catalyst on the support (Fig. 1). The reflectance of the polymer-
bound porphyrin resembles the solution counterpart spectrum,
with only a slight shift and a Soret band at 478 nm and Q bands at
583 and 618 nm, which clearly indicates the presence of the metal-
loporpyhrin on the surface (Fig. 2). The SEM image of the catalysts
showed that the polystyrene has retained its spherical nature and
was not altered during the catalyst preparation (Fig. 3).
the reported procedures [21,22]. 1H NMR spectra were recorded on
a Bruker-Avance AQS 400 MHz. TLC monitored all reactions and all
yields refer to isolated products. A UP 400S ultrasonic processor
equipped with a 3 mm wide and 140 mm long probe, which was
immersed directly into the reaction mixture, was used for sonica-
tion. The operating frequency was 24 kHz and the output power
was set at 0–400 W through manual adjustment. The total volume
of the solution was 15 mL. The temperature reached to 40 °C dur-
ing sonication.
2.1. General procedure for the dehydrogenation of imidazolines with
NaIO4 catalyzed by [Mn(TPP)Cl@PSI]under MS or US irradiation
A solution of NaIO4 (2 mmol) in H2O (10 mL) was added to a
mixture of the 2-imidazolines (1 mmol) and [Mn(TPP)Cl@PSI]
(0.012 mmol) in CH3CN (5 mL), and the reaction mixture was stir-
red at room temperature or exposed to ultrasonic irradiation. The
progress of the reaction was monitored by TLC (eluent: EtOAc/
MeOH: 4/1). After the reaction was completed, the catalyst was fil-
tered. Water (30 mL) was added to the filtrates and the corre-
sponding imidazoles were extracted with CH2Cl2 (2 Â 20 mL). The
solvent was evaporated and the resulting crude material was puri-
fied by column chromatography on alumina to afford the pure
imidazole derivatives. IR and 1H NMR spectral data confirmed
the identities of the products.
3.3. Dehydrogenation of imidazolines with NaIO4 catalyzed by
[Mn(TPP)Cl@PSI] under MS or US irradiation
3. Results and discussion
The successful application of [Mn(TPP)Cl@PSI] in the oxidation
of organic compounds [52,53], prompted us to investigate its cata-
lytic activity in the biomimetic dehydrogenation of 2-imidazoline
with NaIO4 under agitation with magnetic stirring (MS) and under
ultrasonic irradiation (US). First, the amount of catalyst was
optimized in the dehydrogenation of the 2-phenyl imidazolines
3.1. Preparation of polystyrene-bound imidazole
Scheme 2 shows the preparation route for the catalyst. First,
chloromethylated polystyrene (cross-linked with 2% divinylben-
N
N
Mn
N
N
CH3CN, Imidazole
NaI, Reflux
Cl
N
Toluene, 80 oC
48 h
N
N
N
N
N
Mn
N
N
Scheme 2. Preparation route for [Mn(TPP)Cl@PSI].

H. Kargar et al. / Polyhedron 30 (2011) 1463–1468
1465
Fig. 2. Diffuse reflectance UV–Vis spectrum of [Mn(TPP)Cl@PSI].
Fig. 3. SEM image of [Mn(TPP)Cl@PSI].
Table 1
Optimization of the catalyst amount in the oxidation of 2-phenyl imidazoline with
NaIO4 under MS and US irradiation.a
Entry Catalyst amount (mg) MS
US
Time (h) Yield (%)b Time (h) Yield (%)b
1
2
3
4
5
6
100 (2.4
200 (4.8
300 (7.2
400 (9.6
500 (12.0
600 (14.4
l
l
l
l
l
l
mol)
mol)
mol)
mol)
mol)
mol)
10
10
10
10
10
10
45
60
72
77
81
81
1
1
1
1
1
1
48
62
73
78
82
82
a
Reaction conditions: 2-imidazoline (1 mmol), catalyst, NaIO4 (2 mmol), CH3CN
(5 mL), H2O (10 mL), T = 25 °C for MS and 40 °C for US.
b
Isolated yield.
Fig. 1. FTIR spectra of: (a) chloromethylated polystyrene, (b) PSI and (c)
[Mn(TPP)Cl@PSI].
(entries 1a–h) under MS at room temperature (Table 3). Some of
the reported reagents, such as DMSO [29] and Pd/C [29], were
not effective for dehydrogenation of 2-alkylimidazolines. Thus,
efficient oxidation of 2-alkylimidazolines to their imidazoles by
the [Mn(TPP)Cl@PSI]/NaIO4 catalytic system is an interesting fea-
ture of the presented method (entries 1i–j). The results show that
in the absence of catalyst, only 5–10% of the imidazoles were
produced.
with NaIO4 under MS and US. As shown in Table 1, the highest
yield was obtained in the presence of 500 mg (12 lmol) of catalyst.
Then, the effect of different solvents was investigated for choosing
the reaction media. The results show that a 2:1 mixture of H2O/
CH3CN is the best solvent for conversion of 2-imidazolines to their
corresponding 2-imidazoles (Table 2). Under these conditions a
wide range of 2-aryl-2-imidazolines were dehydrogenated to their
corresponding imidazoles with NaIO4 in good to excellent yields
In comparison with its homogeneous counterpart [37],
[Mn(TPP)Cl@PSI] has a higher catalytic activity in these reactions.

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H. Kargar et al. / Polyhedron 30 (2011) 1463–1468
Table 2
The TOFs for this heterogeneous system are higher than those for
the homogeneous system. This may be due to the isolation of cat-
alytic active sites (Table 3).
The effect of solvent on the dehydrogenation of 2-phenyl imidazolines with NaIO4
catalyzed by [Mn(TPP)Cl@PSI] under MS and US irradiation.a
Entry Solvent
MS
US
The exact mechanism of the reaction is not clear at present.
However, a plausible explanation is that the catalyst is first trans-
formed to the corresponding oxo compound 1 by the oxidant. The
oxo compound reacts with imidazoline to afford 2, which in turn is
converted to 3 by proton transfer. The intermediate 3 is converted
to 4 by elimination of water and releases the catalyst for the next
catalytic cycle. The intermediate 4 is finally converted to the
desired product 5 by a hydrogen shift (Scheme 3). It seems that
the stabilization of 3 by resonance and also by the electron-
withdrawing character of the R group is a good indication for the
proposed mechanism. These explanations are also supported by
the results in Table 4, in which imidazolines bearing electron
with-drawing groups (entries 5–7) are more reactive in these
transformations.
Time (h) Yield (%)b Time (h) Yield (%)b
1
2
3
4
5
6
7
8
9
CH3CN:H2O (1:2)
CH3CN:H2O (1:1)
CH3CN:H2O (2:1)
10
10
10
81
70
42
68
47
51
30
39
15
1
1
1
1
1
1
1
1
1
82
73
45
70
50
55
35
45
18
CH3COCH3:H2O (1:2) 10
CH3OH:H2O (1:2) 10
CH3CH2OH:H2O (1:2) 10
CHCl3:H2O (1:2)
CH2Cl2:H2O (1:2)
CCl4:H2O (1:2)
10
10
10
a
Reaction conditions: 2-imidazoline (1 mmol), catalyst (12
lmol), NaIO4
(2 mmol), solvent. T = 25 °C for MS and 40 °C for US.
b
Isolated yield.
Table 3
Oxidation of 2-imidazolines with NaIO4 catalyzed by [Mn(TPP)Cl@PSI] under MS and US irradiation.a
Row Imidazoline
Imidazole
MS
US
Homogeneous Mn(TPP)Cl
[37]
Time
(h)
Yield
(%)b,c
TOF
(hÀ1
Time
(h)
Yield
(%)b
TOF
(hÀ1
TOF (hÀ1
)
)
)
N
N
1
10
10
10
10
81 (79)
6.75
6.00
6.50
6.08
1
1
1
1
82
68.33
66.67
65.83
61.67
3.36
2.92
3.08
3.00
N
H
N
H
(2a)
(1a)
N
N
2
72 (71)
78 (71)
73 (65)
80
79
74
Me
Cl
Me
N
H
N
H
(2b)
(1b)
N
N
3
Cl
N
H
N
H
(1c)
(2c)
N
N
4
N
H
N
H
(2d)
(2e)
(1d)
Cl
N
Cl
N
N
5
10
10
10
92 (84)
90 (85)
82 (78)
7.67
7.50
6.83
1
1
1
94
92
85
78.33
76.67
70.83
3.68
3.44
3.24
N
N
H
N
H
(1e)
N
N
6
7
N
H
N
N
H
N
N
N
(1f)
(2f)
N
H
N
H
N
N
(2g)
(1g)
N
N
8
9
Me O
10
10
70 (68)
88 (81)
5.83
7.33
1
1
78
91
65.00
75.83
2.88
3.80
Me O
N
H
N
H
(2h)
(1h)
N
N
N
H
N
H
(2i)
(1i)
N
N
10
10
90 (84)
7.50
1
92
76.67
3.68
Me
Me
N
H
N
H
(1j)
(2j)
a
Reaction conditions: 2-imidazoline (1 mmol), catalyst (12
lmol), NaIO4 (2 mmol), CH3CN (5 mL), H2O (10 mL). T = 25 °C for MS, 80 °C for reflux conditions and 40 °C for
US.
b
Isolated yield.
c
Yields in the parenthesis refer to the reflux conditions after 7 h.

H. Kargar et al. / Polyhedron 30 (2011) 1463–1468
1467
-
IO4
Mn
PSI
-
IO3
H
H
N
N
+
H2O
R
R
N
N
O
H
H
4
O
Mn
Mn
N
N
R
PSI
PSI
3
R
N
1
N
H
H
5
O
H
N
R
Mn
N
H
H
PSI
2
Scheme 3. The proposed mechanism for oxidation of imidazolines with sodium periodate catalyzed by [Mn(TPP)Cl@PSI].
ment may be due to the break-up of the agglomerates during the
sonication process. A part of the ultrasonic irradiation effect is
due to this phenomenon. To stress this point, the catalytic activity
of a sonicated sample catalyst was studied in the oxidation of 2-
phenyl imidazoline under mechanical stirring. It was found that
the reaction time reduced from 10 to 6 h for the complete dehydro-
genation of 2-phenyl imidazoline to its corresponding 2-phenyl
imidazole. These results show that in addition to break-up of the
agglomerates, other factors such as thorough mixing of the reac-
tants and producing of hot spots are other reasons for catalytic
enhancement by ultrasonic irradiation. On the other hand, when
the oxidation reactions were carried out under reflux conditions,
the reaction times decreased, which confirms the effect of produc-
ing the hot spots on the enhancement of catalytic activity (Table 3).
Table 4
The results of [Mn(TPP)Cl@PSI] catalyst recovery and the manganese leached in the
oxidation of 2-phenyl imidazoline with sodium periodate under magnetic stirring and
ultrasonic irradiation.
Run
Yield (%)a
MS
Mn leached (%)b
MS
US
US
1
2
3
4
5
81
79
79
76
75
82
78
76
75
74
1.5
1.0
0
0
0
2
1.4
0.6
0
0
a
GLC yield based on starting imidazoline.
Determined by atomic absorption spectroscopy.
b
The main effect of ultrasonic irradiation in liquids is the cavita-
3.4. Catalyst reusability
tion phenomenon, which involves numerous tiny gas bubbles
called cavitation bubbles. The collapse of the bubbles generates
high temperature and pressure at the center of the bubbles. These
local effects produce a variety of radicals and highly active inter-
mediates, which initiate other secondary chemical reactions in
the bulk liquid. These radicals can react with contaminants to form
by-products.
The most successful applications of ultrasound have been found
in the field of heterogeneous chemistry involving solids and metals.
This is due to the mechanical impact of ultrasound on solid surfaces.
The mechanical effects of ultrasound offer the opportunity to over-
come the following types of problem associated with conventional
solid/metal reactions: the break-up of the surface structure allows
penetration of reactants and/or release of materials from the sur-
face, degradation of large solid particles occurs due to shear forces
induced by shock waves, microstreaming leads to a reduction of
particle size and an increase of the surface area, and accelerated
motion of suspended particles leads to better mass transfer [66].
When the same reactions were carried out under US irradiation,
the reaction times were reduced to 1 h (Table 3). It seems that the
effect of ultrasonic irradiation on the catalytic activity enhance-
The stability of the supported catalyst was monitored using mul-
tiple sequential dehydrogenations of 2-phenyl imidazoline with so-
dium periodate under agitation with magnetic stirring or under
ultrasonic irradiation. For each of the repeated reactions, the cata-
lyst was recovered, washed exhaustively with water, methanol,
acetonitrile and diethyl ether, and then dried before being used
with fresh 2-phenyl imidazolines and sodium periodate. In both
cases, the catalyst was consecutively reused five times without
any detectable catalyst leaching or any significant loss of its activity
(Table 4). Also, the catalytic behavior of the separated liquid was
tested by addition of fresh 2-phenyl imidazoline and NaIO4 to the
filtrates after each run. Execution of the oxidation reaction under
the same reaction conditions, as for the catalyst, showed that the
obtained results were the same as the blank experiments.
Acknowledgement
The partial support of this work by Payame Noor University
(PNU) of Ardakan is acknowledged.

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H. Kargar et al. / Polyhedron 30 (2011) 1463–1468
[36] A. de la Hoz, Á. Díaz-Ortiz, M. del Carmen Mateo, M. Moral, A. Moreno, J.
References
Elguero, C. Foces-Foces, M.L. Rodríguez, A. Sánchez-Migallón, Tetrahedron 62
(2006) 5868.
[1] M.C. Feiters, A.E. Rowan, R.J.M. Nolte, Chem. Soc. Rev. 29 (2000) 375.
[2] R.A. Sheldon, in: B. Meunier (Ed.), Biomimetic Oxidations Catalyzed by
Transition Metal Complexes, Imperial College Press, London, 2000.
[3] B. Meunier, Chem. Rev. 92 (1992) 1411.
[4] D. Mansuy, P. Battioni, J.P. Battioni, Eur. J. Biochem. 184 (1989) 267.
[5] D. Mansuy, Pure Appl. Chem. 59 (1987) 759.
[6] J.R. Lindsay-Smith, in: R.A. Sheldon (Ed.), Metalloporphyrins in Catalytic
Oxidations, Marcel Dekker, New York, 1994, p. 325 (Chapter 11).
[7] D. Mansuy, Coord. Chem. Rev. 125 (1993) 129.
[8] B.A. Arndtsen, R.G. Bergman, T.A. Mobley, T.H. Peterson, Acc. Chem. Res. 28
(1995) 154.
[9] M.J. Coon, R.E. White, in: T.G. Spiro (Ed.), Dioxygen Binding and Activation by
Metal Centers, Wiley, New York, 1980.
[10] J.T. Groves, T.E. Nemo, J. Am. Chem. Soc. 105 (1983) 5786.
[11] O. Bortolini, B. Meunier, J. Chem. Soc., Perkin Trans. 2 (1984) 1967.
[12] B. Meunier, E. Guilmet, M.E. De Carvalho, R. Poilblanc, J. Am. Chem. Soc. 106
(1984) 6668.
[13] D. Mohajer, S. Tangestaninejad, J. Chem. Soc., Chem. Commun. (1993) 240.
[14] D. Mohajer, S. Tangestaninejad, Tetrahedron Lett. 35 (1994) 945.
[15] C.K. Chang, T.G. Traylor, Proc. Natl. Acad. Sci. USA 70 (1973) 2647.
[16] J.P. Collman, C.A. Reed, J. Am. Chem. Soc. 95 (1973) 2048.
[17] O. Leal, D.L. Anderson, R.C. Bowman, F. Basalo, R.L. Burwell, J. Am. Chem. Soc.
97 (1975) 5125.
[18] L.D. Rollman, J. Am. Chem. Soc. 97 (1975) 2132.
[19] J.H. Wang, Acc. Chem. Res. 3 (1970) 90.
[20] M.R. Grimmett, in: K.T. Potts (Ed.), Comprehensive Heterocyclic Chemistry,
vol. 4, Pergamon, Oxford, 1984, p. 345.
[21] I. Mohammadpoor-Baltork, M. Abdollahi-Alibeik, Bull. Korean Chem. Soc. 24
(2003) 1354.
[22] V. Mirkhani, M. Moghadam, S. Tangestaninejad, H. Kargar, Tetrahedron Lett. 47
(2006) 2129.
[23] T. Dockner, A. Frank, Ger. Offen. 2729,017, Chem. Abstr. (1979) 204100.
[24] L.P. Kyrides, F.B. Zienty, G.W. Steahly, H.L. Morrill, J. Org. Chem. 12 (1947)
577.
[25] R.E. Klem, H.F. Skinner, H. Walba, R.W. Isensee, J. Heterocycle Chem. 7 (1970) 403.
[26] Y. Amemiya, D.D. Miller, F.L. Hsu, Synth. Commun. 20 (1990) 2483.
[27] P.K. Martin, H.R. Matthews, H. Rapoport, G. Thyagarajan, J. Org. Chem. 33
(1968) 3758.
[28] J.L.I.V. Hughey, S. Knapp, H. Schugar, Synthesis (1980) 489.
[29] M. Anastassiadou, G. Baziard-Mouysset, M. Payard, Synthesis (2000)
1814.
[30] I. Mohammadpoor-Baltork, M.A. Zolfigol, M. Abdollahi-Alibeik, Tetrahedron
Lett. 45 (2004) 8687.
[37] H. Kargar, M. Moghadam, V. Mirkhani, S. Tangestaninejad, I. Mohammadpoor-
Baltork, I. Nameni, Biorog. Med. Chem. Lett. 21 (2011) 2146.
[38] M. Nakamura, T. Tatsumi, H. Tominaga, Bull. Chem. Soc. Jpn. 63 (1990) 3334.
[39] W. Nam, H.J. Han, S.Y. Oh, Y.J. Lee, M.H. Choi, S.Y. Han, C. Kim, S.K. Woo, W.
Shin, J. Am. Chem. Soc. 122 (2000) 8677.
[40] R. Naik, P. Joshi, S. Umbarkar, R.K. Deshpande, Catal. Commun. 6 (2005) 125.
[41] F.S. Vinhado, P.R. Martins, A.P. Masson, D.G. Abreu, E.A. Vidoto, O.R.
Nascimento, Y. Iamamoto, J. Mol. Catal. A: Chem. 188 (2002) 141.
[42] P.R. Cooke, J.R. Lindsay Smith, J. Chem. Soc., Perkin Trans. 1 (1994) 1913.
[43] Z. Li, C.-G. Xia, X.-M. Zhang, J. Mol. Catal. A: Chem. 185 (2002) 47.
[44] J. Poltowicz, E.M. Serwicka, E. Bastardo-Gonzalez, W. Jones, R. Mokaya, Appl.
Catal. A 218 (2001) 211.
[45] M.A. Schiavon, Y. Iamamoto, O.R. Nascimento, M.D. Assis, J. Mol. Catal. A:
Chem. 174 (2001) 213.
[46] M.A. Martinez-Lorente, P. Battioni, W. Kleemiss, J.F. Bartoli, D. Mansuy, J. Mol.
Catal. A: Chem. 113 (1996) 343.
[47] M. Benaglia, T. Danelli, G. Pozzi, Org. Biomol. Chem. 1 (2003) 454.
[48] G.R. Geier III, T.P. Lybrand, T. Sasaki, Tetrahedron 55 (1999) 1871.
[49] E. Brule, K.K. Hii, Y.R. de Miguel, Org. Biomol. Chem. 3 (2005) 1971.
[50] E. Brule, Y.R. de Miguel, K.K. Hii, Tetrahedron 60 (2004) 5913.
[51] R. Zhang, W.-Y. Yu, H.-Z. Sun, W.-S. Liu, C.-M. Che, Chem. Eur. J. 8 (2002) 2495.
[52] X.-Q. YU, J.-S. Huang, W.-Y. Yu, C.-M. Che, J. Am. Chem. Soc. 122 (2000) 5337.
[53] J.-L. Zhang, C.-M. Che, Org. Lett. 4 (2002) 1911.
[54] S. Tangestaninejad, M.H. Habibi, V. Mirkhani, M. Moghadam, J. Chem. Res. (S)
(2001) 444.
[55] M. Moghadam, S. Tangestaninejad, M.H. Habibi, V. Mirkhani, J. Mol. Catal. A:
Chem. 217 (2004) 9.
[56] M. Moghadam, S. Tangestaninejad, V. Mirkhani, H. Kargar, H. Komeili-Isfahani,
Catal. Commun. 6 (2005) 688.
[57] M. Moghadam, M. Nasr-Esfahani, S. Tangestaninejad, V. Mirkhani, Bioorg. Med.
Chem. Lett. 16 (2006) 2026.
[58] M. Moghadam, M. Nasr-Esfahani, S. Tangestaninejad, V. Mirkhani, M.A.
Zolfigol, Can. J. Chem. 84 (2006) 1.
[59] S. Tangestaninejad, M. Moghadam, V. Mirkhani, H. Kargar, Ultrason.
Sonochem. 10 (2006) 32.
[60] M. Moghadam, V. Mirkhani, S. Tangestaninejad, I. Mohammadpoor-Baltork,
A.A. Abbasi-Larki, Appl. Catal. A: Gen. 349 (2008) 177.
[61] M. Moghadam, V. Mirkhani, S. Tangestaninejad, I. Mohammadpoor-Baltork, H.
Kargar, J. Mol. Catal. A: Chem. 288 (2008) 116.
[62] V. Mirkhani, M. Moghadam, S. Tangestaninejad, I. Mohammadpoor-Baltork, H.
Kargar, M. Araghi, Appl. Catal. A: Gen. 363 (2009) 61.
[63] M. Moghadam, I. Mohammadpoor-Baltork, S. Tangestaninejad, V. Mirkhani, H.
Kargar, N. Zeini-Isfahani, Polyhedron 28 (2009) 3816.
[64] A.D. Adler, F.R. Long, J.D. Finarellii, J. Goldmacher, J. Assour, L. Korsakoff, J. Org.
Chem. 32 (1967) 476.
[65] M.L. Linares, N. Sanchez, R. Alajarin, J.J. Vaquero, J. Alvarez-Builla, Synthesis
(2001) 382.
[31] I. Mohammadpoor-Baltork, M. Abdollahi-Alibeik, Can. J. Chem. 83 (2005)
110.
[32] M. Abdollahi-Alibeik, I. Mohammadpoor-Baltork, M.A. Zolfigol, Bioorg. Med.
Chem. Lett. 14 (2004) 6079.
[33] I. Mohammadpoor-Baltork, M.A. Zolfigol, M. Abdollahi-Alibeik, Synlett (2004)
2803.
[66] T. Mason, D. Peters, Practical Sonochemistry, second ed., Horwood Publishing,
Chichester, 2002. p. 17.
[34] M.E. Campos, R. Jimenez, F. Martinez, H. Salgado, Heterocycles 40 (1995) 841.
[35] S. Haneda, A. Okui, C. Ueba, M. Hayashi, Tetrahedron 63 (2007) 2414.