The efficient solvent-free reduction of oximes to amines with NaBH3CN catalyzed by ZrCl4/nano Fe3O4 system

Article abstract of DOI:10.1007/s13738-014-0550-3

Reduction of various aldoximes and ketoximes to the corresponding amines was carried out easily and efficiently with NaBH₃CN in the presence of ZrCl₄/nano Fe₃O₄ system. The reactions were carried out under solvent-free conditions at room temperature or 75-80°C to afford amines in high to excellent yields.

Full text of DOI:10.1007/s13738-014-0550-3

J IRAN CHEM SOC
DOI 10.1007/s13738-014-0550-3
ORIGINAL PAPER
The efficient solvent‑free reduction of oximes to amines
with NaBH3CN catalyzed by ZrCl4/nano Fe3O4 system
Leila Sadighnia · Behzad Zeynizadeh
Received: 8 June 2014 / Accepted: 18 October 2014
© Iranian Chemical Society 2014
Abstract Reduction of various aldoximes and ketoxi-
mes to the corresponding amines was carried out easily
and efficiently with NaBH3CN in the presence of ZrCl4/
nano Fe3O4 system. The reactions were carried out under
solvent-free conditions at room temperature or 75–80 °C to
afford amines in high to excellent yields.
NaBH4/Raney Ni [44–46]. Though most of the reported
methods are useful and efficient, however, some of them
suffer from some disadvantages such as using acidic or
basic reaction conditions, use of volatile organic solvents,
long reaction times, and running the reactions at high
temperature.
NaBH3CN with an electron withdrawing cyanide group
is a remarkable stable hydroborate agent, and has been
widely used for reduction of various organic compounds
[47–51]. It is also well known that the reducing capability
of NaBH3CN is greatly depended to use a reaction media
with low pH value (3–4) [52, 53]. The literature review
shows that reduction of oximes with NaBH3CN has been
rarely studied. A study shows that under acidic condi-
tions (pH 4), reduction of ketoximes proceeds smoothly
to the corresponding N-alkylhydroxylamine. Reduction
of aldoximes is very pH dependent: when the reduction
is carried out at pH 4, the major product is a dialkylhy-
droxylamine, while at pH 3 the major product is a mono-
alkylhydroxylamine [52]. It means that NaBH3CN under
acidic conditions reduces oximes to the corresponding
hydroxylamines without over reduction to primary amines.
Moreover, using harsh reaction conditions (strongly acidic
media) and limitation to use acid-sensitive functional
groups are the main disadvantages of this protocol. To
overcome these shortcomings, we have recently reported
the convenient reduction of oximes to primary amines by
NaBH3CN/MoCl5/NaHSO4·H2O system under neutral
reaction conditions [54]. Reduction reactions were carried
out in EtOH to afford amines in high yields.
Keywords Amines · NaBH3CN · Nano Fe3O4 · Oxime ·
Reduction · ZrCl4
Introduction
Amines are important synthetic materials and they have
been used for manufacturing dyes, photographic, pharma-
ceutical and agriculture chemicals, antioxidants and cor-
rosion inhibitors [1–4]. Thus, the particular interests have
been devoted to the preparation of amines by many ways
[5, 6]. Reduction of oximes to primary amines is one of
the most important and straightforward methods for the
preparation of amines. This goal has been achieved by
various reducing systems such as catalytic hydrogena-
tion [7–15], SmI2/base [16], LiAlH4 [17–21], NaAlH2(O
CH2CH2OMe)2 [22], i-Bu2AlH2 [23], Zn/HCO2NH4 [24],
Mg/HCO2NH4 [25], BH3/Me2NH/[Ru(p-cymene)Cl2]2
[26], B2H6 [27], NaBH2S3 [28], BER-Ni(OAc)2 [29],
(Py)Zn(BH4)2 [30], NaBH4 in basic [31] or acidic [32,
33] media, NaBH4/RCO2H [34], NaBH4/CuSO4 [35],
NaBH4/TiCl4 [36–39], NaBH4/NiCl2 [40], NaBH4/MoO3
[40, 41], NaBH4/ZrCl4 [42], NaBH4/ZrCl4/Al2O3 [43], and
Herein, in line of the outlined strategies and continua-
tion of our research program to explore the reducing capa-
bility of NaBH3CN in the absence of any acidic media [54,
55], we wish to introduce a novel and convenient method
for reduction of various aldoximes and ketoximes to the
L. Sadighnia · B. Zeynizadeh (*)
Department of Chemistry, Faculty of Science, Urmia University,
57159-165 Urmia, Iran
e-mail: bzeynizadeh@gmail.com
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J IRAN CHEM SOC
NaBH3CN/ZrCl4/Nano Fe3O4
Solvent-free, r.t. or 75-80 oC
conditions and varying the molar equivalents of the reac-
tants. The results showed that NaBH3CN under the men-
tioned reaction conditions did not show any efficiency
(Table 1, entries 1–5).
R1R2C=NOH
R1R2CH-NH2
Scheme 1 Reduction of oximes with NaBH3CN at solvent-free con-
ditions
Our good experience in reduction of various oximes with
NaBH4/ZrCl4/Al2O3 system [43] prompted us to use ZrCl4
as a promoter in reduction of benzaldehyde oxime with
NaBH3CN/nano Fe3O4 system. An experiment showed that
by adding ZrCl4 to a mixture of oxime/NaBH3CN/nano
Fe3O4 at solvent-free conditions, the rate of reduction was
dramatically accelerated and benzylamine was obtained as
the sole product. The influence of ZrCl4 on the reducing
capability of NaBH3CN was further studied by performing
the reduction of benzaldehyde oxime with NaBH3CN/ZrCl4
system in the absence of nano Fe3O4. The result showed
that ZrCl4 as nano Fe3O4 can not individually affect the
reducing potential of NaBH3CN (entry 6). Although the
mechanism is unknown, however, it is seen that the incor-
poration of catalytic amounts of nano Fe3O4 into ZrCl4
greatly enhances the capability of NaBH3CN for reduc-
tion of benzaldehyde oxime. More examinations resulted
that using a molar equivalent of oxime/NaBH3CN/ZrCl4/
nano Fe3O4 (1:5:1:0.2) at solvent-free conditions was the
requirement to produce benzylamine in high yield (Table 1,
entry 8). We also found that the rate of reduction of ben-
zaldehyde oxime with NaBH3CN/ZrCl4/nano Fe3O4 sys-
tem (1:5:1:0.2) extremely depended to use nano particles
of Fe3O4. Therefore, such reduction with the same molar
equivalents of NaBH3CN, ZrCl4, Fe3O4 (using the simple
one) had only 20 % conversion within 120 min (Table 1,
entry 11). This result obviously shows that the catalytic
corresponding primary amines with NaBH3CN/ZrCl4/nano
Fe3O4 system at solvent-free conditions (Scheme 1).
Results and discussion
Nowadays, nano particles exhibit high catalytic activity
and chemical selectivity under mild conditions [56]. The
extreme small-sized particles maximize the surface area
and allow more reactions to occur at the same time [57].
In this context, the highly reactive and ultra-sized magnetic
nano Fe3O4 has been found in some useful applications in
organic synthesis [58].
The literature review shows that reduction of oximes
with NaBH3CN catalyzed by magnetic nano Fe3O4 has not
been reported yet. This subject and our goals to investigate
the reducing capability of NaBH3CN catalyzed by nano
catalysts and in the absence of any acidic media encour-
aged us to study the capability of NaBH3CN/nano Fe3O4
system for the titled transformation.
We preliminary examined reduction of benzaldehyde
oxime with NaBH3CN in the presence and absence of
nano Fe3O4 under different reaction conditions including:
occurrence of reaction inside solvent and at solvent-free
Table 1 Optimization experiments for reduction of benzaldehyde oxime to benzylamine with NaBH3CN under different conditions
Entry
Reaction components (Molar ratio)
Conditiona
Time (min)
Conversion (%)b
1
Oxime/NaBH3CN (1:4)
Solvent-free/oil bath
Solvent-free/oil bath
CH3CN/reflux
120
120
120
120
120
120
120
30
0
2
Oxime/NaBH3CN/nano Fe3O4 (1:4:0.4)
Oxime/NaBH3CN/nano Fe3O4 (1:4:0.4)
Oxime/NaBH3CN/nano Fe3O4 (1:4:0.4)
Oxime/NaBH3CN/nano Fe3O4 (1:5:1)
5
3
0
4
THF/reflux
0
5
Solvent-free/oil bath
Solvent-free/oil bath
Solvent-free/oil bath
Solvent-free/oil bath
Solvent-free/r.t.
10
10
70
100
20
60
20
Mix.
Mix.
Mix.
6
Oxime/NaBH3CN/ZrCl4 (1:4:1)
7
Oxime/NaBH3CN/ZrCl4/nano Fe3O4 (1:4:1:0.2)
Oxime/NaBH3CN/ZrCl4/nano Fe3O4 (1:5:1:0.2)
Oxime/NaBH3CN/ZrCl4/nano Fe3O4 (1:5:1:0.2)
Oxime/NaBH3CN/ZrCl4/nano Fe3O4 (1:5:0.5:0.2)
Oxime/NaBH3CN/ZrCl4/Fe3O4 (1:5:1:0.2)
Oxime/NaBH3CN/ZnCl2/nano Fe3O4 (1:5:1:0.2)
Oxime/NaBH3CN/MoCl5/nano Fe3O4 (1:5:1:0.2)
Oxime/NaBH3CN/FeCl3/nano Fe3O4 (1:5:1:0.2)
8
9
120
30
10
11c
12
13
14
Solvent-free/oil bath
Solvent-free/oil bath
Solvent-free/oil bath
Solvent-free/oil bath
Solvent-free/oil bath
120
120
120
120
a
The reaction mixture was heated in an oil bath until its temperature reaches 75–80 °C
Mix. means mixture of products
b
c
This reaction was carried out with simple Fe3O4
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J IRAN CHEM SOC
Table 2 Reduction of aldoximes with NaBH3CN/ZrCl4/nano Fe3O4 system
Time
(min)
Yield
(%)b
Entry
Substrate
Product
Molar ratioa
Mp/bp (oC) [lit.]
1
2
3
CH2NH2
1:5:1:0.2
1:5:1:0.2
1:5:1:0.2
15
93
92
95
CH=NOH
bp 185/760 mmHg
[61, 62]
120
50
Cl
Cl
CH=NOH
CH=NOH
Cl
Cl
CH2NH2
CH2NH2
bp 217/760 mmHg
[61, 62]
bp 222/760 mmHg
[61, 62]
Cl
Cl
Cl
Cl
1:5:1:0.2
1:5:1:0.2
bp 251/760 mmHg
[61]
4
5
6
60
60
94
93
CH=NOH
CH2NH2
Cl
Cl
mp 41-45 [62]
bp 267/760 mmHg
[61]
CH=NOH
CH2NH2
O2N
H2N
1:5:1:0.2
1:5:1:0.2
70
20
85
92
mp 37
O2N
CH=NOH
CH=NOH
H2N
CH2NH2
CH2NH2
bp 349/760 mmHg
[61]
7
bp 295/760 mmHg
[61, 62]
Me
MeO
MeO
CH=NOH
Me
8
CH2NH2
CH2NH2
CH2NH2
1:5:1:0.2
1:5:1:0.2
1:5:1:0.2
120
50
5
82
91
96
bp 195/760 mmHg
[61]
bp 237/760 mmHg
[61]
CH=NOH MeO
CH=NOH MeO
9
mp 193-195 [62]
as HCl salt
10
HO
HO
NOH
H
11
1:5:1:0.2
30
85
bp 219/760 mmHg
[63]
CH2NH2
All reactions were carried out under solvent-free conditions at 75–80 °C
a
Molar ratio as: Subs./NaBH3CN/ZrCl4/nano Fe3O4
b
Yields refer to isolated pure products
activity of nano Fe3O4 is decreased by raising the particle
size of Fe3O4 or their aggregation.
(75–80 °C) to produce amines in 82–96 % yields (Table
2). The capability of NaBH3CN/ZrCl4/nano Fe3O4 system
towards the reduction of ketoximes was also studied by
solvent-free reduction of acetophenone oxime. An exami-
nation showed that a molar ratio of 5:1:0.2 for NaBH3CN,
ZrCl4 and nano Fe3O4, respectively, was sufficient to com-
plete reduction of acetophenone oxime (1 mmol) into
α-methylbenzylamine in 92 % yield (Table 3, entry 1).
Versatility of this synthetic protocol for solvent-free reduc-
tion of various ketoximes is shown in Table 3. All ketoxi-
mes were reduced successfully within 5–60 min to afford
the corresponding amines in high to excellent yields. We
also found that under the experimental conditions and in
More studies showed that the influence of other Lewis
acids such as ZnCl2, MoCl5 or FeCl3 on the reducing capa-
bility of NaBH3CN/nano Fe3O4 did not compare with
ZrCl4, and reduction of benzaldehyde oxime encountered
with the formation of various unknown products (Table 1,
entries 12–14).
The utility of NaBH3CN/ZrCl4/nano Fe3O4 system
was further studied by reduction of structurally different
aldoximes to the corresponding primary amines at the opti-
mized reaction conditions. All reactions were carried out
successfully within 5–120 min at solvent-free conditions
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J IRAN CHEM SOC
Table 3 Reduction of ketoximes with NaBH3CN/ZrCl4/nano Fe3O4 system
Time
(min)
Yield
(%)b
Substrate
NOH
Product
Molar ratioa
Mp/bp (oC) [lit.]
Entry
NH2
1:5:1:0.2
1:5:1:0.2
20
50
92
96
1
bp 188/760 mmHg
[61]
Ph
Ph
Ph
2
bp 301/760 mmHg
[61]
NOH
NOH
NH2
Ph
NH2
NH2
NH2
NH2
60
45
40
30
94
96
90
88
3
4
5
6
Me
Br
Cl
Me
Br
Cl
1:5:1:0.2
1:5:1:0.2
1:5:1:0.2
1:5:1:0.2
bp 208/760 mmHg
[61]
NOH
NOH
NOH
bp 259/760 mmHg
[61]
bp 82-83/2.8 mmHg
[64]
mp 55-58 [62]
O2N
H2N
NOH
NOH
NH2
NH2
7
bp 328/760 mmHg
[61]
1:5:1:0.2
1:5:1:0.2
1:5:1:0.2
1:5:1:0.2
20
5
96
94
83
85
8d
mp 138-143
[61, 62]
HON
H2N
9d
5
bp 134/760 mmHg
[61, 62]
NOH
NH2
10d
NOH
NH2
bp 279/760 mmHg
[65]
5
All reactions were carried out under solvent-free conditions at 75–80 °C
a
Molar ratio as: Subs./NaBH3CN/ZrCl4/nano Fe3O4.
b
Yields refer to isolated pure products
c
The reaction was carried out at room temperature
the case of oximes having nitro group, the present proto-
col was not selective and both of oxime and nitro groups
were reduced with the same reactivity (Table 2, entries 5,
6; Table 3, entry 6). In addition, a comparison of the results
in Tables 2 and 3 shows that reduction of ketoximes with
NaBH3CN/ZrCl4/nano Fe3O4 system is generally faster
than aldoximes.
benefits of solvent-free conditions are the main advantages
which make this protocol a useful addition to the present
methodologies.
Experimental
In conclusion, we have shown that the incorporation
of catalytic amounts of nano Fe3O4 into ZrCl4 effectively
promotes the reducing capability of NaBH3CN towards
the reduction of various aldoximes and ketoximes. Reduc-
tion reactions were carried out under solvent-free condi-
tions at room temperature or 75–80 °C to afford primary
amines in high to excellent yields. The enhanced reducing
capability of NaBH3CN in the absence of any Brønsted
acid, versatility of this protocol for reduction of various
aldoximes and ketoximes, and high efficiency as well as the
General
All reagents and solvents were purchased from commercial
sources with the best quality and they were used without
further purification. Oximes [59] and nano Fe3O4 [60] are
prepared in high purity according to the reported proce-
1
dures. IR and H NMR spectra were recorded on Thermo
Nicolet Nexus 670 FT-IR and 300 MHz Bruker spectrome-
ters, respectively. All yields refer to isolated pure products.
TLC was applied for the purity determination of substrates,
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J IRAN CHEM SOC
15. K. Pfister, C.A. Robinson, A.C. Shabica, M. Tishler, J. Am.
Chem. Soc. 70, 2297 (1948)
16. Y. Kamochi, T. Kudo, Tetrahedron Lett. 32, 3511 (1991)
17. H.C. Brown, P.M. Weissman, N.M. Yoon, J. Am. Chem. Soc. 88,
1458 (1966)
products and reaction monitoring over silica gel 60 F254
aluminum sheet. All products are known and were char-
acterized by their H NMR and IR spectra followed by a
1
comparison with the authentic data in literature [61–65].
18. D.R. Smith, M. Maienthal, J. Tipton, J. Org. Chem. 17, 294
(1952)
19. S. Dev, Proc. Indian Acad. Sci. 93, 1015 (1984)
20. D. Carr, B. Iddon, H. Suschitzky, R.T. Parfitt, J. Chem. Soc. Per-
kin Trans. I, 2374 (1980)
A typical procedure for solvent‑free reduction
of benzaldehyde oxime to benzylamine
with NaBH3CN/ZrCl4/nano Fe3O4 system
21. K. Kotera, K. Kitahonoki, Org. Synth. 48, 20 (1968)
22. S.R. Landor, O.O. Sonola, A.R. Tatchell, J. Chem. Soc. Perkin
Trans. I, 1294 (1974)
A mixture of benzaldehyde oxime (0.121 g, 1 mmol)
and nano Fe3O4 (0.046 g, 0.2 mmol) (nano particle size
≈70 nm) was ground in a porcelain mortar. ZrCl4 (0.233 g,
1 mmol) was then added and grinding the mixture was con-
tinued for a moment at room temperature. The mortar was
heated in an oil bath until the temperature of reaction mix-
ture reaches 75–80 °C. NaBH3CN (0.314 g, 5 mmol) was
then added portion wisely and the mixture was ground for
15 min at 75–80 °C. After completion of the reaction, H2O
(5 mL) was added and the mixture was stirred for 5 min.
The mixture was extracted with EtOAc (2 × 5 mL) and
then dried over anhydrous Na2SO4. Evaporation of the
solvent affords the pure liquid benzylamine in 93 % yield
23. S. Sasatani, T. Miyazaki, K. Maruoka, H. Yamamoto, Tetrahedron
Lett. 24, 4711 (1983)
24. K. Abiraj, D.C. Gowda, J. Chem. Res. 332 (2003)
25. K. Abiraj, D.C. Gowda, Synth. Commun. 34, 599 (2004)
26. T.D. Nixon, M.K. Whittlesey, J.M.J. Williams, Tetrahedron Lett.
52, 6652 (2011)
27. H. Feuer, D.M. Braunstein, J. Org. Chem. 34, 1817 (1969)
28. J.M. Lalancette, J.R. Brindle, Can. J. Chem. 48, 735 (1970)
29. B.P. Bandgar, S.M. Nikat, P.P. Wadgaonkar, Synth. Commun. 25,
863 (1995)
30. B. Zeynizadeh, K. Zahmatkesh, J. Chin. Chem. Soc. 52, 109
(2005)
31. K.H. Bell, Aust. J. Chem. 23, 1415 (1970)
32. G.W. Gribble, R.W. Leiby, M.N. Sheehan, Synthesis 856 (1977)
33. G.W. Gribble, C.F. Nutaitis, Org. Prep. Proced. Int. 17, 317
(1985)
34. G.W. Gribble, Chem. Soc. Rev. 27, 395 (1998)
35. H.S.P. Rao, B. Bharathi, Indian J. Chem. 41B, 1072 (2002)
36. H. Spreitzer, G. Buchbauer, C. Püringer, Tetrahedron 45, 6999
(1989)
37. C. Hoffman, R.S. Tanke, M.J. Miller, J. Org. Chem. 54, 3750
(1989)
1
(0.1 g, Table 2, entry 1). H NMR (CDCl3, 300 MHz): δ
7.25–7.33 (m, 5H), 3.83 (s, 2H), 2.04 (s, 2H). 13C NMR
(CDCl3, 75.5 MHz): δ 140.06, 128.56, 128.41, 128.20,
127.65, 127.00, 53.05. FT-IR (KBr, υ cm−1): 3,368, 3,292,
3,061, 3,026, 2,920, 2,858, 1,605, 1,585, 1,511, 1,494,
1,452, 1,246, 1,026, 866, 736, 698.
38. J.P. Leeds, H.A. Kirst, Synth. Commun. 18, 777 (1988)
39. S. Kano, Y. Tanaka, E. Sugino, S. Hibino, Synthesis 695 (1980)
40. J. Ipaktschi, Chem. Ber. 117, 856 (1984)
41. J. Herscovici, M.-J. Egron, K. Antonakis, J. Chem. Soc. Perkin
Trans. I, 1219 (1988)
Acknowledgments The financial support of this work was grate-
fully acknowledged by the Research Council of Urmia University.
42. S. Itsuno, Y. Sakurai, K. Ito, Synthesis 995 (1988)
43. B. Zeynizadeh, M. Kouhkan, Bull. Korean Chem. Soc. 32, 3448
(2011)
References
44. Y. Yang, S. Liu, J. Li, X. Tian, X. Zhen, J. Han, Synth. Commun.
1. A. Ricci, Modern amination methods (Wiley-VCH, Weinheim,
2000)
42, 2540 (2012)
45. A. Kascheres, R.A.F. Rodrigues. Tetrahedron 52, 12919 (1996)
46. Q.-C. Zhu, R.O. Hutchins, M.K. Hutchins, Org. Prep. Proced. Int.
26, 193 (1994)
2. S.A. Lawrence, Amines: synthesis, properties and applications
(Cambridge University Press, UK, 2004)
3. T.C. Nugent, Chiral amine synthesis: methods, developments and
applications (Wiley-VCH, Weinheim, 2010)
47. C.F. Lane, Synthesis 135, (1975)
48. R.O. Hutchins, I.M. Taffer, W. Burgoyne, J. Org. Chem. 46, 5214
(1981)
49. S. Kim, C.H. Oh, J.S. KO, K.H. Ahn, Y.J. Kim. J. Org. Chem. 50,
1927 (1985)
50. O. Han, Y. Shih, L.-D. Liu, H.-W. Liu, J. Org. Chem. 53, 2105
(1988)
51. L.A. Paquette, D. Crich, P.L. Fuchs, G.A. Molander, Encyclope‑
dia of reagents for organic synthesis, 2nd edn. (Wiley, Weinheim,
2009)
52. R.F. Borch, M.D. Bernstein, H.D. Durst, J. Am. Chem. Soc. 93,
2897 (1971)
53. R.O. Hutchins, D. Kandasamy, J. Org. Chem. 40, 2530 (1975)
54. M. Kouhkan, B. Zeynizadeh, Bull. Korean Chem. Soc. 32, 3323
(2011)
55. M. Kouhkan, B. Zeynizadeh, Bull. Korean Chem. Soc. 31, 2961
(2010)
56. R.B. Nasir Baig, R.S. Varma, Chem. Commun. 49, 752 (2013)
4. T. Farooqui, A.A. Farooqui, Biogenic amines: pharmacological,
neurochemical and molecular aspects in the CNS (Nova Science
Publisher, New York, 2010)
5. J. Hagen, Industrial catalysis: a practical approach, 2nd edn.
(Wiley-VCH, Weinheim, 2006)
6. H.J. Arpe, Industrial organic chemistry, 5th edn. (Wiley-VCH,
Weinheim, 2010)
7. H. Adkins, H.R. Billica, J. Am. Chem. Soc. 70, 695 (1948)
8. M. Freifelder, W.D. Smart, G.R. Stone, J. Org. Chem. 27, 2209
(1962)
9. C.F. Winans, H. Adkins, J. Am. Chem. Soc. 54, 306 (1932)
10. P. Anziani, R. Cornubert, Bull. Soc. Chim. Fr. 857 (1948)
11. F.E. King, J.A. Barltrop, R.J. Walley, J. Chem. Soc. 277 (1945)
12. H. Adkins, E.W. Reeve, J. Am. Chem. Soc. 60, 1328 (1938)
13. N.F. Alberstron, B.F. Tullar, J.A. King, B.B. Fishburn, S. Archer,
J. Am. Chem. Soc. 70, 1150 (1948)
14. T. Ishimaru, Nippon Kagaku Zusshi 81, 643 (1960)
1 3

J IRAN CHEM SOC
57. H. Montazeri, A. Amani, H.R. Shahverdi, E. Haratifar, A.R.
Shahverdi, J. Nanostruct. Chem. 3, 25 (2013)
62. SigmaAldrich online catalogue. http://www.sigmaaldrich.com.
Accessed 22 Sep. 2014
58. V. Polshettiwar, R. Luque, A. Fihri, H. Zhu, M. Bouhrara, J.M.
63. Integrating Global Trade Leads. http://www.weiku.com.
Accessed 22 Sep. 2014
Basset, Chem. Rev. 111, 3036 (2011)
59. B. Zeynizadeh, E. Amjadi, Asian J. Chem. 21, 3611 (2009)
60. X. Ma, L. Cui, G. Xu, Appl. Mech. Mater. 271–272, 320 (2013)
61. Global Chemical Network. http://www.chemnet.com. Accessed
22 Sep. 2014
64. Acros Organics. http://www.acros.com. Accessed 22 Sep. 2014
65. OXchem. http://demo.xmlsite.cn/ark/web/index.html. Accessed
22 Sept 2014
1 3