2
H. Ghafuri et al. / C. R. Chimie xxx (2016) 1e9
2
-aminothiophenol with acyl chlorides or aldehydes. In
3 4
Fe O nanoparticles were separated by using an external
this case, synthesis procedures include the use of ionic
liquid [31] and/or microwave irradiation with a SiO cata-
lyst [32] and/or refluxing in the presence of homo/hetero-
magnet in isoelectric point (pH ~ 8). Then, the collected
precipitate was poured in EtOH 50% and separated by using a
magnet (rinsed using magnet separation) three times.
2
geneous catalysts such as acetic acid [33], active carbon in
3 4
Finally, Fe O nanoparticles were dried in a vacuum oven.
3 4
toxic solvents [34] and Chitosan-supported Fe O [35].
To the best of our knowledge, most of the methods for
the synthesis of benzimidazoles and benzothiazoles suffer
from one or some disadvantages such as low yields, harsh
reaction conditions, time consuming process, use of
expensive catalysts and tedious workups. Thus presently,
the development of environmentally benign, high-yielding
and fast synthesis of benzimidazole and benzothiazole
derivatives remains a desired goal in organic synthesis. In
this work, we report a highly efficient procedure for the
preparation of benzimidazole and benzothiazole de-
2.3. Preparation of the Fe O @SiO /collagen nanocatalyst
3
4
2
First, 2 g of Fe O nanoparticles and 5 mL of tetraethyl
3
4
orthosilicate (TEOS) were added in a 500-mL round bottom
flask that contains 150 mL EtOH 50%. In the second vessel,
10 g of collagen was dissolved in 100 mL of a dilute acetic
acid solution (5%) under vigorous stirring. A homogeneous
supernatant of the second mixture was added to the Fe O
3
4
mixture. The flask was poured in an ultrasonic bath for
30 min. Then, NH OH (10%) was added dropwise to the
4
rivatives in ethanol (EtOH) media using Fe
3
O
4
2
@SiO /
mixture until the pH reached about eight. In the next step,
collagen as an efficient magnetic reusable nanocatalyst.
the residue was collected by using an external magnet; it
was poured in a Teflon autoclave that contains EtOH (50%)
and heated at 90 C for 6 h. The resulting product was
separated by external magnetic fields, dispersed in EtOH
ꢀ
2
. Experimental
.1. Materials and methods
Hydrolysed collagen was of industrial grade (Parvar
2
50% and rinsed three times. Finally, it was dried in a vac-
ꢀ
uum oven at 60 C for 12 h.
Novin-e Tehran Co., Mw ¼ 2000e20,000 Da), which is
available in the market, and it has approximately 20%
insoluble inorganic salts [36,37]. All chemicals were pur-
chased from Merck, Fluka and SigmaeAldrich companies
and were used without further purification.
2
.4. Synthesis of the non-magnetic nanocatalyst (SiO
2
/
collagen)
The nonmagnetic nanocatalyst (SiO
synthesised by the same procedure (mentioned in 2.3.)
without using Fe and tripling the amount of TEOS.
2
/collagen) was
All reactions and the purity of benzimidazole and ben-
zothiazole derivatives were monitored by thin-layer chro-
matography (TLC) using aluminium plates coated with silica
gel F254 plates (Merck) using ethyl acetate, n-hexane and
methanol as eluents. Melting points were determined in
open capillaries using an Electrothermal 9100 instrument.
Fourier transform infrared (FT-IR) spectra were recor-
ded on a Shimadzu FT-IR 8400s using KBr plates of samples.
3 4
O
2.5. Synthesis of the non-silicate magnetic nanocatalyst
(
Fe @collagen)
3 4
O
3 4
The non-silicate magnetic nanocatalyst (Fe O @collagen)
was synthesised by the same procedure (mentioned in 2.3)
without using TEOS in the synthesis procedure.
1
Proton nuclear magnetic resonance ( H NMR) spectra were
recorded on a Bruker 400 ultrashield and DMSO-d
used as the solvent. A transmission electron microscope
TEM) from day-petronic company of Iran was used. Scan-
ning electron microscopy (SEM) and energy dispersive X-
ray (EDX) analysis were performed on a VEGA II TESCAN
using 30 KV in high vacuum and Au spin coating for SEM
sample preparation. Wide-angle powder X-ray diffraction
6
was
Table 1
a
Optimization of the catalysts and solvents for synthesis of benzimidazole.
(
Entry Type & amount of catalystb Solvent
Time Yield (%)
(min)
1
2
3
4
5
6
7
Non-additive
50 (Collagen)
50 (Collagen)
EtOH
1080 25
c
H O
2
_
_
50 85
240 30
20 96
25 95
150 53
d
EtOH
EtOH
EtOH
EtOH
EtOH
50 (Fe
50 (Fe
3
3
O
O
4
)
(
XRD) patterns of the solids were obtained in a JEOL with a
4
@collagen)
Cu K q
a
(
l
¼ 0.15420 nm) X-ray irradiation source in a 2
2
50 (SiO @collagen)
ꢀ
ꢀ
range between 5 and 80 . Magnetic properties were
recorded by the vibrational sampling magnetometry (VSM)
technique in 1.5 T external magnetic fields at room tem-
perature, by using a MDK-6 instrument.
50 (Fe
3
O
4
@SiO
2
)
8
9
1
1
1
1
1
1
10 (Fe
50 (Fe
80 (Fe
3
3
3
O
4
O
4
O
4
@SiO
@SiO
@SiO
2
/collagen)
2
/collagen)
2
/collagen)
EtOH
EtOH
EtOH
20 68
20 97
20 56
20 30
15 97
15 Trace
15 80
15 49
0
1
2
3
4
5
160 (Fe
3
O
4
@SiO
2
/collagen) EtOH
50 (Fe
50 (Fe
50 (Fe
50 (Fe
3
3
3
3
O
4
O
4
O
4
O
4
@SiO
2
/collagen)
2
/collagen)
2
/collagen)
2
/collagen)
EtOH
H O
2
2
3 4
.2. Preparation of Fe O magnetic nanoparticles
@SiO
@SiO
@SiO
CH
2
Cl
2
Fe
tion method by using ferric chloride (FeCl
ferrous chloride (FeCl $4H O) that was introduced in our
O
3 4
nanoparticles were synthesised via a coprecipita-
CHCl
3
3
$6H O) and
2
16
50 (Fe O @SiO /collagen)
3
4
2
3
CH CN
15
e
2
2
17
50 (Fe
3
O
4
@SiO
2
/collagen)
Solvent free
15
previous paper [38]. Briefly, Ferric chloride and ferrous
chloride dissolved in degassed water and ammonia solution
were addedtothis mixture undervigorous stirring. WhenpH
e
a
Benzimidazoles synthesis conditions: 1 mmol 1,2 phenylendiamine,
1
mmol 3-nitrobenzaldehyde, 4 mL solvent at rt.
Catalyst (mg).
b
increases, black colloids of Fe
O
3 4
nanoparticles were formed.
3 4 2
Please cite this article in press as: H. Ghafuri, et al., Fe O @SiO /collagen: An efficient magnetic nanocatalyst for the synthesis of