Ferrite nanoparticles supported on natural wool in one-pot tandem oxidative reactions: strategy to synthesize benzimidazole, quinazolinone and quinoxaline derivatives

Article abstract of DOI:10.1002/aoc.3542

Two tandem oxidative two-component reactions (O-2CRs) and Ugi-type three-component reactions (OU-3CRs) of aromatic hydrocarbons of petroleum naphtha have been investigated for the synthesis of 2-phenyl-1H-benzo [d]imidazole, 2-aryl-4-quinazolinone and 3,4-dihydroquinoxalin-2-amine derivatives using six new biopolymer-supported ferrite nanocatalysts: CoFe₂O₄@wool-SO₃H, MnFe₂O₄@wool-SO₃H, ZnFe₂O₄@wool-SO₃H, MnCoFe₂O₄@wool-SO₃H, ZnCoFe₂O₄@wool-SO₃H and CrCoFeO₄@wool-SO₃H. The best results are obtained with the CrCoFeO₄@wool-SO₃H catalyst. All of the catalysts were characterized using flame atomic absorption spectrometry, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy-dispersive spectroscopy. To the best of our knowledge, this approach can be considered as the first example of O-2CRs and OU-3CRs of aromatic hydrocarbons of petroleum naphtha with ferrite nanocatalysts, which would be very useful from a practical point of view. Copyright

Full text of DOI:10.1002/aoc.3542

Full paper
Received: 5 March 2016
Revised: 15 May 2016
Accepted: 27 May 2016
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/aoc.3542
Ferrite nanoparticles supported on natural wool
in one-pot tandem oxidative reactions: strategy
to synthesize benzimidazole, quinazolinone
and quinoxaline derivatives
Ahmad Shaabani* and Zeinab Hezarkhani
Two tandem oxidative two-component reactions (O-2CRs) and Ugi-type three-component reactions (OU-3CRs) of aromatic hydro-
carbons of petroleum naphtha have been investigated for the synthesis of 2-phenyl-1H-benzo [d]imidazole, 2-aryl-4-
quinazolinone and 3,4-dihydroquinoxalin-2-amine derivatives using six new biopolymer-supported ferrite nanocatalysts:
CoFe2O4@wool-SO3H, MnFe2O4@wool-SO3H, ZnFe2O4@wool-SO3H, MnCoFe2O4@wool-SO3H, ZnCoFe2O4@wool-SO3H and
CrCoFeO4@wool-SO3H. The best results are obtained with the CrCoFeO4@wool-SO3H catalyst. All of the catalysts were character-
ized using flame atomic absorption spectrometry, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy
and energy-dispersive spectroscopy. To the best of our knowledge, this approach can be considered as the first example of O-
2CRs and OU-3CRs of aromatic hydrocarbons of petroleum naphtha with ferrite nanocatalysts, which would be very useful from
a practical point of view. Copyright © 2016 John Wiley & Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web site.
Keywords: aerobic oxidation; tandem oxidative synthesis; ferrite nanoparticles; natural wool
used to address this issue by transforming an inert substance into
a reactive substrate for IMCRs. One-pot oxidative MCRs involve in situ
Introduction
Mixtures of benzene, toluene and the three xylene isomers (BTX)
are co-generated, alongside other aromatics and non-aromatics,
during coal conversion and petroleum refining. Reformer gasoline,
pyrolysis gasoline and coke oven benzole are the most important
sources for BTX. Among the BTX family members, toluene and
xylenes can be modified by chemical procedures because of the
presence of the methyl substituents and used as precursors in
synthetic chemistry.[1–7]
oxidation of one reagent or the oxidation of one reagent or interme-
diate is performed as a separate step.[14] These transformations could
significantly widen the versatility and the scope of well-known
aldehyde-based MCRs. Recently, alcohols and N-alkylamines have
been directly used in Passerini and Ugi reactions, respectively.[15–26]
Tandem aerobic oxidation/MCRs can be a useful strategy with either
primary or secondary alkylarenes instead of their corresponding al-
dehydes or ketones in IMCRs.
Ferrites are chemical compounds with ferrimagnetic properties
formed by iron oxides as their main component. Transition metal
ferrites of the spinel type with the general formula MFe2O4 are
attractive candidates for catalysis of organic compounds because
of their magnetic properties which means they can be easily recov-
ered after completion of reactions using a magnet.[8] These bimetal-
lic nanoparticles are especially interesting for oxidation of organic
compounds since magnetic and catalytically active components
are integrated in the same system. Mixed-metal ferrites, ferrites
containing two metal ions in addition to iron, are much more
widely used in nanocatalytic processes. Among them, cobalt-based
ferrite nanoparticles exhibit higher and more stable catalytic activ-
ity and selectivity in chemical transformations.[9]
Benzimidazole and 4-quinazolinone compounds are of impor-
tance from a biological and pharmaceutical point of view.[27,28]
These biologically active compounds are mainly synthesized by
two-component reaction of carbonyl sources (aldehydes or carbox-
ylic acids) and o-phenylenediamines and 2-aminobenzamide, re-
spectively. The tandem aerobic oxidative synthesis of 2-phenyl-
1H-benzo [d] imidazole and 2-aryl-4-quinazolinone compounds
using an oxidative two-component reaction (O-2CR) strategy could
considerably widen the diversity and the scope of these reactions.
In continuation of our studies towards the introduction of new cat-
alysts for organic transformations,[29–34] herein we report one-pot
tandem O-2CRs and Ugi-type three-component reactions (OU-
Multicomponent reactions (MCRs)[10,11] and especially isocyanide-
base MCRs (IMCRs)[12,13] are powerful tools for the synthesis of bio-
logical heterocyclic molecules such as quinoxaline compounds.
Some of the most important reactants in MCRs and especially IMCRs
are aldehydes and ketones and unfortunately this limits the versatil-
ity of MCRs and IMCRs. The one-pot oxidative MCR protocol can be
*
Correspondence to: Ahmad Shaabani, Faculty of Chemistry, Shahid Beheshti
University, GC, PO Box 19396-4716, Tehran, Iran. E-mail:a-shaabani@sbu.ac.ir
Faculty of Chemistry, Shahid Beheshti University, GCPOBox 19396-4716, Tehran,
Iran
Appl. Organometal. Chem. (2016)
Copyright © 2016 John Wiley & Sons, Ltd.

A. Shaabani and Z. Hezarkhani
3CRs) with toluene and xylenes for the synthesis of 2-phenyl-1H-
benzo [d]imidazole, 2-aryl-4-quinazolinone and 3,4-
dihydroquinoxalin-2-amine derivatives in the presence of six
biopolymer-supported ferrite nanocatalysts: CoFe2O4@wool-SO3H,
MnFe2O4@wool-SO3H, ZnFe2O4@wool-SO3H, MnCoFe2O4@wool-
solution of Na2SO3 (70 g lÀ1) and acetic acid (35 mol lÀ1) and stirred
at 50 °C. After 10 min the wool was returned to a white colour, and
was washed with water several times and then dried at 80 °C. The
number of H+ sites of wool-SO3H determined using acid–base titra-
tion was 1.0 meq. gÀ1
.
SO3H,
ZnCoFe2O4@wool-SO3H
and
CrCoFeO4@wool-SO3H
Preparation of MFe2O4@wool-SO3H (M
MCoFe2O4@wool-SO3H (M = Mn, Zn) and CrCoFeO4@wool-SO3H
=
Co, Mn, Zn),
(Scheme 1). The six synthesized nanocatalysts have dual properties:
they are not only used to carry out the oxidation processes but also
as acid catalysts to accelerate the condensation reactions.
MFe2O4 (M = Co, Mn, Zn) nanoparticles supported on wool-SO3H
were prepared from FeCl3 and MCl2 solutions using a method sim-
ilar to a previously reported one.[35] Wool-SO3H-supported MFe2O4
nanoparticles were prepared in an aqueous solution with a molar
ratio of Fe(III)/M(II) = 2 and pH = 12. To a magnetically stirred sus-
pension of wool-SO3H (1.0 g) in 100 ml of deionized water, 3.0 mmol
of FeCl3 and 1.5 mmol of MCl2 were added. A solution of NaOH
(1.0 M) was added into the resulting mixture under vigorous stirring
to obtain a solution with pH = 12. The mixture was stirred under re-
Materials and methods
General
Natural white wool (sheep of Kangavar, Iran) was washed with
NaOH solution, distilled water and ethanol, and then cut with scis-
sors to very short pieces (about 100 μm–1 mm, based on scanning
electron microscopy (SEM) images). All reagents were obtained
from Aldrich or Merck and used without further purification. SEM
observations were carried out with a Philips XL-30 ESEM electron
microscope. All samples were sputtered with gold before observa-
tion. Metal determination was carried out with flame atomic ab-
sorption spectrometry (FAAS; Shimadzu model AA-680
spectrometer) using an air–acetylene flame. Thermogravimetric
analysis (TGA) was carried out using an STA 1500 instrument at a
heating rate of 10 °C minÀ1 in air. X-ray diffraction (XRD) patterns
of products were recorded with a STOE STADI P with scintillation
detector and secondary monochromator using Cu Kα radiation
(λ = 0.1540 nm). Products were analysed using a Varian 3900 GC.
Melting points were measured with an Electrothermal 9200
apparatus.
flux conditions for
4
h
to afford MFe2O4@wool-SO3H.
MFe2O4@wool-SO3H was separated and washed several times with
dilute HCl and distilled water and dried at 80 °C.
MCoFe2O4 (M = Mn, Zn) and CrCoFeO4 nanoparticles supported
on wool-SO3H were prepared in the same way with a molar ratio
of Fe(III)/Co(II)/M(II) = 2/0.5/0.5 and Fe(III)/Co(II)/Cr(III) = 1/1/1, re-
spectively, and pH = 12.
General Procedure for preparation of products 3a–d and 5a–d
In a two-necked flask, to a solution of o-phenylenediamine or 2-
aminobenzamide (1.0 mmol) in toluene or xylene (5.0 ml) was
Preparation of catalysts
Preparation of wool-SO3H
For the modification of wool and the synthesis of wool-SO3H, a
0.1 M solution of KMnO4 (150 ml) was added dropwise to a magnet-
ically stirred suspension of the natural wool pieces (1.0 g) in 250 ml
of water during 12 h at room temperature. The mixture was filtered
to give brown MnO2@wool. This brown wool was dipped in a
Figure 1. TGA curves of wool (I), wool-SO3H (II), CoFe2O4@wool-SO3H (III),
MnFe2O4@wool-SO3H (IV), ZnFe2O4@wool-SO3H (V), MnCoFe2O4@wool-
SO3H (VI), ZnCoFe2O4@wool-SO3H (VII) and CrCoFeO4@wool-SO3H (VIII)
catalysts in air.
Scheme 1. Oxidative synthesis of 2-phenyl-1H-benzo[d]imidazole, 2-aryl-4-
quinazolinone and 3,4-dihydroquinoxalin-2-amine derivatives.
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Appl. Organometal. Chem. (2016)

Ferrite nanoparticles supported on natural wool
added catalyst and the mixture was stirred magnetically under re-
flux conditions and air blowing for the required time. The progress
of the reaction was monitored by TLC. After completion, the reac-
tion mixture was filtered and washed with ethanol and the filtrate
was evaporated under reduced pressure to afford the crude prod-
uct. The crude product was separated on a silica gel column to give
final products 3a–d or 5a–d. The 1H NMR data for the synthesized
compounds are available as Supporting Information.
The amounts of CoFe2O4, MnFe2O4, ZnFe2O4, MnCoFe2O4,
ZnCoFe2O4 and CrCoFeO4 in CoFe2O4@wool-SO3H, MnFe2O4@wool-
SO3H,
ZnFe2O4@wool-SO3H,
MnCoFe2O4@wool-SO3H,
ZnCoFe2O4@wool-SO3H and CrCoFeO4@wool-SO3H were deter-
mined as 16.23, 17.18, 18.13, 18.42, 17.91 and 12.93%, respectively.
Figure 1 shows the thermal behaviour of the six catalysts. TGA
demonstrated that these catalysts were decomposed above
270 °C in two stages, which showed the relatively high thermal sta-
bility of the obtained catalysts in air.
General Procedure for preparation of products 7a–d
In a typical reaction, 5.0 ml of toluene or xylene was added to a two-
necked flask containing catalyst and was stirred under reflux condi-
tions and air blowing. The progress of the reaction was monitored
by TLC and GC. The reaction mixture was cooled after the required
time. o-Phenylenediamine (1.0 mmol), cyclohexyl isocyanide
(1.0 mmol) and 5.0 ml of ethanol (96%) were added to the reaction
media and stirred at room temperature. The progress of the reac-
tion was followed by TLC. After completion, the reaction mixture
was filtered off and washed with ethanol. Finally, the product was
separated on a silica gel column. The 1H NMR data for the synthe-
sized compounds are provided in Supporting Information.
Characterization of catalysts
CoFe2O4@wool-SO3H, MnFe2O4@wool-SO3H, ZnFe2O4@wool-SO3H,
MnCoFe2O4@wool-SO3H,
ZnCoFe2O4@wool-SO3H
and
CrCoFeO4@wool-SO3H were characterized using FAAS, XRD, TGA,
SEM and energy-dispersive spectroscopy (EDS). The metal content
of the obtained catalysts was determined using the FAAS method.
Figure 2. XRD patterns of wool (I), wool-SO3H (II), CoFe2O4@wool-SO3H (III),
MnFe2O4@wool-SO3H (IV), ZnFe2O4@wool-SO3H (V), MnCoFe2O4@wool-
SO3H (VI), ZnCoFe2O4@wool-SO3H (VII) and CrCoFeO4@wool-SO3H (VIII)
catalysts.
Figure 3. SEM images of wool (a), wool-SO3H (b), CoFe2O4@wool-SO3H (c,d),
MnFe2O4@wool-SO3H (e,f), ZnFe2O4@wool-SO3H (g,h), MnCoFe2O4@wool-
SO3H (i,j), ZnCoFe2O4@wool-SO3H (k,l) and CrCoFeO4@wool-SO3H (m,n)
catalysts.
Appl. Organometal. Chem. (2016)
Copyright © 2016 John Wiley & Sons, Ltd.
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A. Shaabani and Z. Hezarkhani
The structure and morphology of the six catalyst nanocompos-
ites were investigated using SEM (Fig. 3). It is evident that the syn-
thesis and impregnation of ferrite nanoparticles on wool has not
altered the morphology of the wool support. From Figs 3(d), (f),
(h), (j), (l) and (n), ferrite nanostructures can be observed on the
wool fibre surfaces, and nanoparticles are well dispersed on the
wool fibre surfaces.
EDS analysis was employed for determination of the chemical
composition of the six catalyst nanocomposites (Fig. 4).
Results and discussion
The coagulation of unsupported nanoparticles during reaction is fre-
quently unavoidable. Aggregation and agglomeration of ferrite
nanoparticles into less active large particles and bulk ferrite during
reaction decrease their catalytic activities. Wool contains numerous
amino acid units with ─ NH ─ CO ─ , ─ NH2 and ─ S ─ S ─ functional
groups. The uptake of metal oxide nanoparticles by wool fibres can
be done via the functional groups of wool. Due to the structurally or-
dered amino acid chains, the aggregation of ferrite nanoparticles can
be prevented. Also, a suitable oxidizing agent can attack the disulfide
linkages of wool, and they are easily oxidized to ─ SO3H groups to
produce solid acid catalyst.
The preparation of catalysts was based on a modification of natural
wool by oxidation of ─ S ─ S ─ to ─ SO3H groups using KMnO4 as
oxidant and then loading of MnO2 on the wool surface. Subsequently,
the MnO2 loaded on the surface of modified wool was removed from
the support by washing with an aqueous solution of Na2SO3 and
acetic acid to give wool-SO3H (Scheme 2). Sulfonated wool-supported
ferrite nanoparticles were prepared as also shown in Scheme 2.
Initially, the possibility of the synthesis of 2-phenyl-1H-benzo [d]
imidazole (3a) by tandem O-2CR of aromatic hydrocarbons of pe-
troleum naphtha using these catalysts was examined under various
conditions (Table 1). Toluene (1a) and o-phenylenediamine (2)
were added to a two-necked flask containing catalyst and stirred
under reflux conditions and air blowing. After completion of the re-
action, the reaction mixture was filtered and washed and the crude
product was separated on a silica gel column to give product 3a.
The results are summarized in Table 1.
In continuation, 1a and 2-aminobenzamide (4) were selected as
the test substrates for optimization of the reaction conditions for
the synthesis of 2-aryl-4-quinazolinones (Table 1).
Figure 4. SEM–EDS results for CoFe2O4@wool-SO3H (I), MnFe2O4@wool-
SO3H (II), ZnFe2O4@wool-SO3H (III), MnCoFe2O4@wool-SO3H (IV),
ZnCoFe2O4@wool-SO3H (V) and CrCoFeO4@wool-SO3H (VI) catalysts.
In addition to TGA, the XRD patterns of wool, wool-SO3H and the
six catalysts were employed to investigate the structure of the syn-
thetic catalysts (Fig. 2).
Scheme 2. Preparation of catalysts.
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Appl. Organometal. Chem. (2016)

Ferrite nanoparticles supported on natural wool
Table 1. Optimization of reaction conditions for oxidative synthesis of 2-phenyl-1H-benzo[d]imidazole (3a) and 2-phenylquinazolin-4(3H)-one (5a)
catalysed by wool-supported ferrite nanocatalystsa
Entry
Catalyst (ferrite content, mol%)
t (h)
Yield (%)b
Entry
Catalyst (ferrite content, mol%)
t (h)
Yield (%)b
1
CoFe2O4@wool-SO3H (10)
CoFe2O4@wool-SO3H (8)
CoFe2O4@wool-SO3H (6)
MnFe2O4@wool-SO3H (18)
MnFe2O4@wool-SO3H (15)
MnFe2O4@wool-SO3H (12)
ZnFe2O4@wool-SO3H (15)
ZnFe2O4@wool-SO3H (12)
ZnFe2O4@wool-SO3H (9)
MnCoFe2O4@wool-SO3H (8)
MnCoFe2O4@wool-SO3H (6)
MnCoFe2O4@wool-SO3H (4)
ZnCoFe2O4@wool-SO3H (7)
ZnCoFe2O4@wool-SO3H (6)
ZnCoFe2O4@wool-SO3H (5)
CrCoFeO4@wool-SO3H (7)
CrCoFeO4@wool-SO3H (6)
CrCoFeO4@wool-SO3H (5)
9
9
9
9
9
9
9
9
9
7
7
7
7
7
7
7
7
7
68
37
29
61
39
30
62
41
28
69
38
24
71
42
33
75
47
36
1
2
CoFe2O4@wool-SO3H (10)
CoFe2O4@wool-SO3H (8)
CoFe2O4@wool-SO3H (6)
MnFe2O4@wool-SO3H (18)
MnFe2O4@wool-SO3H (15)
MnFe2O4@wool-SO3H (12)
ZnFe2O4@wool-SO3H (15)
ZnFe2O4@wool-SO3H (12)
ZnFe2O4@wool-SO3H (9)
MnCoFe2O4@wool-SO3H (8)
MnCoFe2O4@wool-SO3H (6)
MnCoFe2O4@wool-SO3H (4)
ZnCoFe2O4@wool-SO3H (7)
ZnCoFe2O4@wool-SO3H (6)
ZnCoFe2O4@wool-SO3H (5)
CrCoFeO4@wool-SO3H (7)
CrCoFeO4@wool-SO3H (6)
CrCoFeO4@wool-SO3H (5)
18
18
18
18
18
18
18
18
18
12
12
12
12
12
12
12
12
12
72
43
32
70
51
38
73
55
41
78
52
30
80
60
51
87
61
46
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
11
12
13
14
15
16
17
18
10
11
12
13
14
15
16
17
18
aReaction conditions for the synthesis of 3a: toluene (5.0 ml), o-phenylenediamine (1.0 mmol), reflux. Reaction conditions for the synthesis of 5a: toluene
(5.0 ml), 2-aminobenzamide (1.0 mmol), reflux.
bIsolated yield.
Table 2. Synthesis of 2-phenyl-1H-benzo[d]imidazole, 2-aryl-4-quinazolinone and 3,4-dihydroquinoxalin-2-amine derivatives catalysed by wool-sup-
ported ferrite nanocatalystsa
Entry
Arene
Catalyst
t (h)
Yield (%)b
M.p. (°C)
Found
Reported
1
Toluene
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
9
9
9
7
7
7
9
9
9
7
7
7
9
9
9
7
7
3a
68
61
62
69
71
75
80
68
71
82
80
87
88
81
79
90
93
289–290
292–293[36]
2
3
4
5
6
7
o-Xylene
p-Xylene
3b
3c
224–226
273–275
223–224[36]
275–276[36]
(Continues)
8
9
10
11
12
13
14
15
16
17
Appl. Organometal. Chem. (2016)
Copyright © 2016 John Wiley & Sons, Ltd.
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A. Shaabani and Z. Hezarkhani
Table 2. (Continued)
Entry
Arene
Catalyst
t (h)
Yield (%)b
M.p. (°C)
Found
Reported
18
19
20
21
22
23
24
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
7
9
9
9
7
7
7
96
51
47
45
52
50
54
m-Xylene
3d
232–233
231–232[36]
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
Toluene
o-Xylene
p-Xylene
m-Xylene
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
18
18
18
12
12
12
18
18
18
12
12
12
18
18
18
12
12
12
18
18
18
12
12
12
5a
5b
5c
5d
72
70
73
78
80
87
73
69
71
77
79
84
78
75
74
83
81
90
39
36
37
42
41
45
232–233
211–212
232–234
208–210
232–235[37]
212–215[37]
231–234[37]
210–211[38]
49
50
Toluene
CoFe2O4@wool-SO3H
MnFe2O4@wool-SO3H
9
9
7a
84
86
186–187
185–187[39]
(Continues)
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Ferrite nanoparticles supported on natural wool
Table 2. (Continued)
Entry
Arene
Catalyst
t (h)
Yield (%)b
M.p. (°C)
Found
Reported
51
52
53
54
55
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
9
7
7
7
9
82
91
85
90
89
o-Xylene
p-Xylene
m-Xylene
7b
7c
7d
215–216
216–217[32]
56
57
58
59
60
61
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
9
9
7
7
7
9
85
83
90
91
93
84
200–201
201[39]
62
63
64
65
66
67
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
CoFe2O4@wool-SO3H
9
9
7
7
7
9
78
80
83
89
91
41
188–190
189–192[32]
68
69
70
71
72
MnFe2O4@wool-SO3H
ZnFe2O4@wool-SO3H
MnCoFe2O4@wool-SO3H
ZnCoFe2O4@wool-SO3H
CrCoFeO4@wool-SO3H
9
9
7
7
7
39
35
42
38
50
aReaction conditions: arene (5.0 ml), o-phenylenediamine (entries 1–24 and 49–72: 1.0 mmol), 2-aminobenzamide (entries 25–48: 1.0 mmol), cyclohexyl
isocyanide (entries 49–72: 1.0 mmol), catalyst (CoFe2O4@wool-SO3H (0.14 g), MnFe2O4@wool-SO3H (0.24 g), ZnFe2O4@wool-SO3H (0.20 g),
MnCoFe2O4@wool-SO3H (0.12 g), ZnCoFe2O4@wool-SO3H (0.12 g) and CrCoFeO4@wool-SO3H (0.15 g)).
bIsolated yield.
Table 3. Comparison of efficiency of obtained catalysts in same reac-
tion time for synthesis of compound 3aa
Entry
Catalyst (ferrite content, mol%)
t (h)
Yield (%)b
1
2
3
4
5
6
CoFe2O4@wool-SO3H (10)
MnFe2O4@wool-SO3H (18)
ZnFe2O4@wool-SO3H (15)
MnCoFe2O4@wool-SO3H (8)
ZnCoFe2O4@wool-SO3H (7)
CrCoFeO4@wool-SO3H (7)
5
5
5
5
5
5
45
44
39
48
49
64
Scheme
dihydroquinoxalin-2-amine (7a).
3. Oxidative
synthesis
of
N-cyclohexyl-3-phenyl-3,4-
As mentioned above, one-pot O-2CRs and MCRs involve in situ
oxidation of one reagent or the oxidation of the reagent is per-
formed as a separate step. By in situ oxidation of toluene, the de-
sired products 3a and 5a are obtained. Since the boiling point of
cyclohexyl isocyanide is lower than 60 °C, it can be predicted that
aReaction conditions: toluene (5.0 ml), o-phenylenediamine (1.0 mmol).
bIsolated yield.
Appl. Organometal. Chem. (2016)
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

A. Shaabani and Z. Hezarkhani
by in situ oxidation of toluene the product 7a will not be formed be-
cause of the high reaction temperature; therefore, oxidation of tol-
uene as a separate step was carried out. With this approach, toluene
was oxidized in the presence of the ferrite catalysts under reflux
reaction conditions for the reaction times presented in Table 2.
After cooling the reaction media, o-phenylenediamine (2),
cyclohexyl isocyanide (6) and commercially available ethanol
(96%) were added and allowed to react at room temperature. The
successful synthesis of compound 7a confirms the utility of the
CoFe2O4@wool-SO3H, MnFe2O4@wool-SO3H, ZnFe2O4@wool-
SO3H, MnCoFe2O4@wool-SO3H, ZnCoFe2O4@wool-SO3H and
CrCoFeO4@wool-SO3H nanocomposites as catalysts for the aerobic
oxidation processes and condensation reactions (Scheme 3).
Table 2 summarizes the results of investigation of the scope and
limitations of oxidative synthesis of 2-phenyl-1H-benzo [d]imidaz-
ole, 2-aryl-4-quinazolinone and 3,4-dihydroquinoxalin-2-amine de-
rivatives from various aromatic hydrocarbons of petroleum
naphtha (1a–d) under the optimized conditions.
To select the best catalyst, the synthesis of 2-phenyl-1H-benzo [d]
imidazole (3a) was studied as a model reaction for the same reac-
tion times. As evident from Table 3, CrCoFeO4@wool-SO3H acts as
the best catalyst for the reaction process.
Because the presence of a methyl functional group as an electron-
donating group can affect the activity of alkylarenes in oxidation reac-
tions, to examine the effect of the methyl functional group, a reaction
with 1:1 ratio of toluene and o-xylene was performed using the
prepared catalysts in a limited time. The obtained results show that
o-xylene is more active in the mentioned reaction using the prepared
catalytic systems and o-xylene gives the only product (Table 4).
To find the fast step in the oxidative synthesis of the mentioned
compounds, the oxidation of p-xylene and the synthesis of 2-(p-
tolyl)-1H-benzo [d]imidazole using 4-methylbenzaldehyde or p-
xylene and o-phenylenediamine were carried out as three model
reactions in the presence of CrCoFeO4@wool-SO3H as catalyst. As
evident from Table 5, the oxidation process of p-xylene (entry 1)
is faster than both the condensation reactions (entries 2 and 3).
The recyclability of the prepared catalysts was examined. To
that end, the catalysts were recovered from the O-2CR between
toluene and o-phenylenediamine by filtration, dried and reused
four times (Fig. 5). It is clear that on successive use of the
CoFe2O4@wool-SO3H, MnFe2O4@wool-SO3H, ZnFe2O4@wool-
SO3H, MnCoFe2O4@wool-SO3H, ZnCoFe2O4@wool-SO3H and
CrCoFeO4@wool-SO3H nanocomposites, their reactivity and
performance are not decreased to a significant extent (Fig. 5).
Table 4. Efficiency of methyl group of alkylarene in oxidative synthesis
of 2-phenyl-1H-benzo[d]imidazole derivatives using the prepared
catalystsa
Entry
Catalyst (ferrite content, mol%)
t (h)
Yield (%)b
3a
3b
1
2
3
4
5
6
CoFe2O4@wool-SO3H (10)
MnFe2O4@wool-SO3H (18)
ZnFe2O4@wool-SO3H (15)
MnCoFe2O4@wool-SO3H (8)
ZnCoFe2O4@wool-SO3H (7)
CrCoFeO4@wool-SO3H (7)
4
4
4
4
4
4
—
—
—
—
—
—
32
29
24
33
35
43
aReaction conditions: toluene (2.5 ml), o-xylene (2.5 ml), o-
phenylenediamine (1.0 mmol).
bIsolated yield.
Table 5. Comparison of rate of oxidation of p-xylene and condensation of o-phenylenediamine with 4-methylbenzaldehyde
Entry
Reaction
Yield (%)
8c
3c
1a
12
—
2b
11
14
Trace
Trace
3c
aReaction conditions: p-xylene (5.0 ml), CrCoFeO4@wool-SO3H (0.15 g), reflux, 30 min.
bReaction conditions: o-phenylenediamine (1.0 mmol), p-xylene (5.0 ml), CrCoFeO4@wool-SO3H (0.15 g), reflux, 30 min.
cReaction conditions: o-phenylenediamine (1.0 mmol), 4-methylbenzaldehyde (1.0 mmol), p-xylene (5.0 ml), CrCoFeO4@wool-SO3H (0.15 g), reflux, 30 min.
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Appl. Organometal. Chem. (2016)

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Conclusions
We synthesized, characterized and applied CoFe2O4@wool-SO3H,
MnFe2O4@wool-SO3H, ZnFe2O4@wool-SO3H, MnCoFe2O4@wool-
SO3H, ZnCoFe2O4@wool-SO3H and CrCoFeO4@wool-SO3H nano-
composites as six new biopolymer-based oxidation and solid acid
catalysts in O-2CRs and OU-3CRs with toluene and three xylene iso-
mers. These ferrite nanocatalysts have been used successfully in the
oxidation of low-price toluene and xylenes to valuable aldehydes in
the absence of additional oxidizing reagent. The distribution of fer-
rites on the surface of wool fibres gives a biopolymer-based cata-
lytic system, which has high catalytic activity and selectivity in the
one-pot tandem aerobic oxidative synthesis of 2-phenyl-1H-benzo
[d]imidazole, 2-aryl-4-quinazolinone and 3,4-dihydroquinoxalin-2-
amine derivatives. Use of air as (inexpensive) oxidant), renewability
and recyclability (with no loss in activity) are some of the advan-
tages of the prepared catalysts.
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Acknowledgements
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7046–51.
[38] J. Zhou, J. Fang, J. Org. Chem. 2011, 76, 7730–6.
[39] A. Shaabani, A. Maleki, H. Mofakham, H. R. Khavasi, J. Comb. Chem.
2008, 10, 323–6.
We gratefully acknowledge the financial support of the Iran Na-
tional Elites Foundation (INEF) and the Research Council of Shahid
Beheshti University.
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Appl. Organometal. Chem. (2016)
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