The synthesis of imidazoles and evaluation of their antioxidant and antifungal activities

Article abstract of DOI:10.1007/s00706-018-2167-1

Abstract: Tri- and tetra-substituted imidazole compounds were synthesized through in situ oxidation–condensation in the presence of catalytic amount of H₂PW₁₂O₄₀ˉ loaded on the ionic liquid-functionalized magnetic nanopart

Full text of DOI:10.1007/s00706-018-2167-1

Monatshefte für Chemie - Chemical Monthly
https://doi.org/10.1007/s00706-018-2167-1(0123456789(). -, vo Vl
)
0
1
2
3
4
5
6
7
8
9
(
)
.
-
v
o
l
V
)
ORIGINAL PAPER
The synthesis of imidazoles and evaluation of their antioxidant
and antifungal activities
Ramin Ghorbani-Vaghei1 Vida Izadkhah1 Jafar Mahmoodi1 Roya Karamian2 Masoumeh Ahmadi Khoei2
•
•
•
•
Received: 11 December 2017 / Accepted: 29 January 2018
Ó Springer-Verlag GmbH Austria, part of Springer Nature 2018
Abstract
Tri- and tetra-substituted imidazole compounds were synthesized through in situ oxidation–condensation in the presence of
¯
catalytic amount of H2PW12O40 loaded on the ionic liquid-functionalized magnetic nanoparticles. Then, the antioxidant
and antifungal activities of the new imidazoles were evaluated. The effectiveness of the samples as DPPH radical
scavengers was confirmed by the measured IC50 values and thiophenyl-containing product showed the best IC50 of 0.12
when compared to the standard ascorbic acid. Moreover, all compounds have antifungal activity against Fusarium
oxysporum.
Graphical Abstract
.
Keywords Imidazole Á Antioxidant Á Fungicide Á Phosphotungstic acid Á Magnetic properties
Introduction
nucleic acids, sugars) leading to tissue injury, DNA dam-
aging, and various diseases such as arthritis, cancer, and
Alzheimer’s disease [1]. Antioxidants are commonly
organic compounds which by preventing the oxidation of
biomolecules can inhibit DNA mutations, oxidative stress,
and other forms of cell damage. Antioxidant activity of
organic compounds is usually evaluated using a spec-
trophotometer with regard to the ability to scavenge 2,2-
diphenyl-1-picrylhydrazyl (DPPH) radical. This method is
straightforward, cost-effective, and rapid to find the non-
enzymatic antioxidants [2].
Through physiological and metabolic processes and food
products, free radicals and partially reduced oxygen-con-
taining compounds are produced. These species are toxic
since they oxidize the vital biomolecules (proteins, lipids,
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00706-018-2167-1) contains supplementary
material, which is available to authorized users.
& Ramin Ghorbani-Vaghei
rgvaghei@yahoo.com
1.35 Million people die annually as a result of fungal
infection. Among the pathogens and parasites, fungi are the
ones that endanger the health of humans and other crea-
tures. Some antifungal compounds are produced naturally
although resistance to these compounds occurs
1
Faculty of Chemistry, Bu-Ali Sina University,
Hamedan 6517838683, Iran
2
Department of Biology, Faculty of Science, Bu-Ali Sina
University, Hamedan, P. O. Box 65175/4161, Iran
123

R. Ghorbani-Vaghei et al.
correspondingly. Therefore, development of new antifun-
gal agents is inevitable [3].
the mentioned catalyst (Table 1). Among the tested con-
ditions as shown in entries 1–4 of Table 1, refluxing in a
solvent was better than the solvent-free condition. Protic
solvent (EtOH) plays a significant role in the formation of
the product since the used catalyst can exchange proton to
activate the starting materials. Therefore, refluxing in
EtOH was selected as the best condition for this reaction in
the presence of the catalyst. To examine the effect of
Imidazole is a nitrogen-rich heterocyclic compound
which derivatives are applied in different fields of study
including sensors [4], catalysis [5–7] and electrocatalysis
[8], drug discovery [9–13], producing fuel cells [14], and
conducting polymers [15]. Due to the importance of imi-
dazole compounds, an optimized methodology is essential
for their synthesis [16–21]. Therefore, according to the
significance of imidazole compounds, herein we used a
new phosphotungstate-based catalyst for the preparation of
tri- and tetra-substituted imidazole compounds. Then, the
antioxidant and antifungal activities of the produced imi-
dazoles are investigated and discussed.
¯
H2PW12O40 and ionic liquid phase on this reaction, syn-
thesis of 4a was tested in the presence of naked MNPs and
silica-coated MNPs under modified conditions (entries 5
and 6, respectively). The results demonstrated that both of
them affect this reaction but not efficiently. Low reaction
yield after 3 h in the absence of the catalyst displays the
vital role of catalyst in this reaction. To study the generality
of this reaction, various tri- and tetra-substituted imidazole
derivatives (Scheme 1 and 2) were synthesized in the
presence of H3PW12O40/Fe3O4@SiO2–Pr–Pi (Table 2).
The high yield of products proves the efficiency of the
prepared catalyst. It is essential to mention that separation
of the catalyst by the use of an external super magnet is the
main advantage of this procedure.
Results and discussion
Magnetite is a perfect metal oxide support, easy to make,
having a very active surface for immobilization of metals,
silica, and ligands, which can be separated by an external
magnet after the reaction, thus converting it to a more
sustainable catalyst [22]. Therefore, we selected magnetic
nanoparticles (MNPs) as the core of the catalyst to make an
easily separable heterogeneous catalyst. Then, the surface
of MNPs was covered with silica and subsequently, the
surface of silica was modified with a new type of ionic
liquid including a piperidinium moiety which is different
from the traditional types containing the imidazolium
cations [23, 24]. Consequently, the synthesis of imidazole
The proposed mechanism is shown in Scheme 3. Ini-
tially, the oxygen atom of aldehyde carbonyl group is
protonated by the catalyst and then, the released ammonia
from ammonium acetate attacks the activated carbonyl
group. The amine 5 is added to the formed imine 7 to gain
intermediate 8. Afterward, the latter is condensed with the
activated benzil 9 (which is produced through oxidation of
¯
benzoin 1 by the H2PW12O40, following protonation), and
the final product is obtained after dehydration and aroma-
¯
compounds was catalyzed by H2PW12O40 loaded on the
ionic liquid-functionalized magnetic nanoparticles (see ESI
for the preparation and characterization of the catalyst).
The oxidizing nature of catalyst was tested through the
multicomponent reaction of benzoin, aldehyde, aniline
derivative, and ammonium acetate. As it is evident, ben-
zoin is oxidized to benzil in the presence of H3PW12O40
loaded on the catalyst surface and then, benzil follows the
reactions. The reaction of benzoin (1), ammonium acetate
(2) and 4-fluorobenzaldehyde was selected as the model
reaction, and its condition was modified in the presence of
tization of intermediate 10.
Antioxidant activity of tetra-substituted
imidazoles
In this research, all new imidazoles were investigated for
antioxidant activity and all of them showed lower scav-
enging activity than that of ascorbic acid as a standard
antioxidant except the sample 4n. The radical scavenging
activity of the new imidazoles decreased in the following
Table 1 Optimizing the
reaction conditions or the
synthesis of imidazole 4a
Entry
Catalyst
Solvent
Condition
Time/h
Yield/%
1
2
3
4
5
6
7
8
H3PW12O40/Fe3O4@SiO2–Pr–Pi
H3PW12O40/Fe3O4@SiO2–Pr–Pi
H3PW12O40/Fe3O4@SiO2–Pr–Pi
H3PW12O40/Fe3O4@SiO2–Pr–Pi
Fe3O4
–
30 °C
Reflux
Reflux
Reflux
r.t.
3.5
1.5
1.5
1
70
70
60
95
50
70
75
30
CH3CN
THF
EtOH
EtOH
EtOH
EtOH
EtOH
3
Fe3O4@SiO2
60 °C
Reflux
Reflux
3
Fe3O4@SiO2–Pr–Pi
–
2
3
123

The synthesis of imidazoles and evaluation of their antioxidant and antifungal activities
Scheme 1 .
Scheme 2 .
Scheme 3 .
oxysporum, especially the samples 4d, 4c, and 4o. So they
may be considered as promissory antifungal agents.
order: 4n [ ascorbic acid [ 4 m [ 4p [ 4o [ 4c [ 4d
(Table 3). The higher antioxidant activity is reflected in a
lower IC50. On the other hand, the effectiveness of the
samples as DPPH radical scavengers was confirmed by the
measured IC50 values (Fig. 1).
Conclusion
In this paper, the synthesis of tri- and tetra-substituted
imidazole derivatives was investigated in the presence of
Antifungal activity
¯
H2PW12O40 loaded on the magnetic nanoparticle-supported
Evaluation of new antifungal agents through in vitro sus-
ceptibility testing can help establish guidelines for the
potential clinical application of new the rapiers. Fusarium
is an essential genus of fungal pathogens, responsible for
devastating diseases such as cereal scab, which has epi-
demic levels [30]. Antifungal activity of the new com-
pounds was evaluated here against Fusarium oxysporum
through mycelial growth inhibition using a microscale-
amended-medium assay (Table 4). Our results showed that
all compounds have antifungal activity against Fusarium
ionic liquid phase. Simple preparation and also easy iso-
lation of this catalyst from the reaction mixture using an
external magnet are its advantages. The new imidazole
compounds were also analyzed for their antioxidant prop-
erties by DPPH free radical scavenging assay. Also, the
antifungal activity of the synthesized compounds was
assessed by the cultivation of the fungus Fusarium oxys-
porum on potato dextrose agar medium containing them.
The results showed that these compounds exhibited ranges
of biological activities.
Table 2 H3PW12O40
/
Entry
No.
Ar1
Ar2
Yield/%
M.p./°C
Lit. m.p./°C
Fe3O4@SiO2–Pr–Pi-catalyzed
synthesis of tri- and tetra-
substituted imidazoles
1
4a
4b
4c
4d
4e
4f
4-F-C6H4
H
95
95
90
96
98
95
95
96
97
97
96
95
95
92
93
90
252–253
260–261
220–221
232–233
223–225
209–210
219–220
226–227
220–223
280–281
253–254
244–247
248–249
201–203
189–191
216–218
250–251 [25]
262–264 [25]
228–231 [25]
230–232 [25]
224–226 [26]
209–211 [27]
221–223 [26]
228–230 [28]
220–222 [28]
281–283 [28]
253–255 [28]
246–248 [28]
247–251 [29]
–
2
4-Cl-C6H4
H
3
4-OMe-C6H4
4-Me-C6H4
4-Cl-C6H4
H
4
H
5
4-Me-C6H4
4-Cl-C6H4
4-Cl-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Cl-C6H4
C6H5
6
4-Cl-C6H4
7
4g
4h
4i
4-Me-C6H4
4-Me-C6H4
4-OMe-C6H4
4-Biphenyl
2-Naphthyl
2,4-Cl2-C6H3
Thiophen-2-yl
Thiophen-2-yl
Thiophen-2-yl
Thiophen-2-yl
8
9
10
11
12
13
14
15
16
4j
4k
4l
4m
4n
4o
4p
4-Me-C6H4
4-OMe-C6H4
4-Cl-C6H4
–
–
123

R. Ghorbani-Vaghei et al.
Table 3 Antiradical activity (%) of the new imidazole compounds and ascorbic acid as standard
Sample
Concentration/mg cm-3
Average
0.2
0.4
0.6
0.8
1
4 m
75.35c 0.40
81.13c 1.3
74.71b 1.7
61.67c 0.20
70.37b 0.5
67.76b 0.39
80.84a 0.80
75.63c 2.7
82.85bc 1.6
71.27b 0.72
61.13c 0.72
71.22b 0.06
68b 0.06
79.31b 0.04
85.58b 2.7
72.31b 0.12
61.71c 0.24
70.88b 0.47
67.55b 0.48
81.21a 1.40
81.54b 1.33
88.84a 0.011
82.85a 0.7
65.31b 1.57
72.91a 0.05
69.58a 0.05
80.80a 2.30
85.11a 1.06
88.67a 0.08
83.34a 1.03
69.58a 0.14
74.02a 1.3
70.69a 1.3
80.16a 1.90
79.38
85.41
77.11
63.88
71.88
75.69
80.61
4n
4p
4d
4c
4o
Ascorbic acid
81.84a 1.70
The experiment was performed in triplicate and expressed as mean SD. Values in each row with different superscripts are significantly
different (p B 0.05)
instrument was used to capture transmission electron
microscopy (TEM) images. Brunauer–Emmett–Teller
(BET) analysis was performed on a BELSORP instrument.
Preparation of piperidine-modified silica-coated
magnetic nanoparticles (Fe3O4@SiO2–Pr–Pi)
The silica-coated magnetic Fe3O4 nanoparticles were pre-
pared through the method published before [31, 32].
Afterward, 3 g Fe3O4@SiO2 and (3-chloropropyl)tri-
ethoxysilane (10 mmol) in 80 cm3 of dry toluene were
refluxed under nitrogen for 12 h. The treated Fe3O4@-
SiO2–Pr–Cl was filtered, washed well with toluene and
Fig. 1 Comparison of antioxidant activity (IC50 values) of the
diethyl ether, and dried at 80 °C for 6 h under reduced
samples and ascorbic acid as standard
pressure. To prepare piperidine-modified magnetic
nanoparticles (Fe3O4@SiO2–Pr–Pi), first 1.0 g Fe3O4@-
Experimental
SiO2–Pr–Cl was dispersed in a mixture of 50 cm3 dry
toluene and 3 cm3 piperidine for 30 min. Then, the reac-
tion mixture was refluxed for 72 h. The solid phase was
filtered off, washed with toluene and ethanol, and dried at
60 °C in a vacuum.
All chemicals were commercially available substances
purchased from Merck and Fluka Companies and used
without further purification. 1H and 13C NMR spectra were
recorded at 400 and 100 MHz, respectively (Bruker
Avance). A Perkin-Elmer GX FT-IR spectrometer was
used for Fourier transform infrared (FT-IR) spectra. Ele-
mental analyses (CHN) were obtained by the use of an
Elemental Combustion System 4010. Thermo-gravimetric
analyses (TGA) were performed on a PYRIS DIAMOND.
The images of scanning electron microscopy (SEM) and
energy-dispersive X-ray (EDX) analyses were done on a
FESEM-SIGMA (Germany) instrument. A ZEISS-EM3200
Loading the H3PW12O40 on the Fe3O4@SiO2–Pr–
Pi nanoparticles
Fe3O4@SiO2–Pr–Pi (0.5 g) and 1 g H3PW12O40 were dis-
persed in 70 cm3 methanol and the mixture was refluxed
for 24 h under N2 atmosphere. Then, the solid was sepa-
rated using an external super magnet and washed
Table 4 Antifungal activity (%)
of the new imidazole
compounds
Concentration/ppm
200
Sample
4 m
4n
4p
4d
4c
4o
41f 1.11
49e 1.3
30g 1.6
53d 1.8
61c 1.7
72b 1.2
The experiment was performed in triplicate and expressed as mean SD. Values in the row with different
superscripts are significantly different (p B 0.05)
123

The synthesis of imidazoles and evaluation of their antioxidant and antifungal activities
ppm; 13C NMR (75 MHz, DMSO-d6): d = 125.6, 126.2,
126.6, 127.3, 127.5, 128.1, 128.5, 128.6, 129.4, 129.7, 131,
thoroughly with methanol using a Soxhlet apparatus and
then dried for characterization (see ESI).
131.2, 132.5, 133.8, 134.1, 135, 136.8, 141.3 ppm.
General procedure for the preparation of tri-
substituted imidazoles 4a–4d
Acknowledgements We are thankful to Bu-Ali Sina University,
Center of Excellence in Development of Environmentally Friendly
Methods for Chemical Synthesis (CEDEFMCS), for financial support.
A mixture of 0.21 g benzoin (1, 1 mmol), the corre-
sponding aldehyde 3 (1 mmol), and 0.12 g ammonium
acetate (2, 1.5 mmol) dissolved in 3 cm3 EtOH was heated
in the presence of 2 mg of the magnetic catalyst under
reflux condition. The progress of the reaction was moni-
tored by thin layer chromatography (TLC) with a tank of
EtOAc and n-hexane (ratio of 2:5). After completion of the
reaction, the catalyst was separated using an external
magnet, and the residue was dissolved in an excess amount
of hot EtOH to obtain a clear solution and then to gain pure
crystals of the product. The obtained products were ana-
lyzed by melting points, FT-IR and NMR spectra.
References
1. Lobo V, Patil A, Phatak A, Chandra N (2010) Pharmacogn Rev
4:118
2. Pisoschi AM, Pop A (2015) Eur J Med Chem 97:55
3. Parker JE, Warrilow AGS, Price CL, Mullins JGL, Kelly DE,
Kelly SL (2014) J Chem Biol 7:143
4. Jain A, Gupta R, Agarwal M (2017) Synth Commun 47:1307
5. Hartikka A, Hojabri L, Bose PP, Arvidsson PI (2009) Tetrahe-
dron Asymmetry 20:1871
ˇ
´
6. Bures F, Szotkowski T, Kulhanek J, Pytela O, Ludwig M, Hol-
ˇ
capek M (2006) Tetrahedron Asymmetry 17:900
7. Shen X-B, Gao T-T, Lu J-M, Shao L-X (2011) Appl Organomet
Chem 25:497
General procedure for the preparation of tetra-
substituted imidazoles 4e–4p
8. Nasirizadeh N, Shekari Z, Zare HR, Shishehbore MR, Fakhari
AR, Ahmar H (2013) Biosens Bioelectron 41:608
9. Needleman P, Raz A, Ferrendelli JA, Minkes M (1977) Proc Natl
Acad Sci 74:1716
10. Matsui H, Sakanashi Y, Oyama TM, Oyama Y, Yokota S-I,
Ishida S, Okano Y, Oyama TB, Nishimura Y (2008) Toxicology
248:142
A mixture of 0.21 g benzoin (1, 1 mmol), the corre-
sponding aldehyde 3 (1 mmol), amine 5 (1 mmol), and
0.12 g ammonium acetate (2, 1.5 mmol) dissolved in
3 cm3 EtOH was heated in the presence of 2 mg of the
magnetic catalyst under reflux condition. The progress of
the reaction was monitored by thin layer chromatography
(TLC) with a tank of EtOAc and n-hexane (ration of 2:5).
The workup process was same as the procedure mentioned
before.
`
11. Salerno L, Pittala V, Romeo G, Modica MN, Siracusa MA, Di
Giacomo C, Acquaviva R, Barbagallo I, Tibullo D, Sorrenti V
(2013) Bioorg Med Chem 21:5145
12. Assadieskandar A, Amini M, Salehi M, Sadeghian H, Alimardani
M, Sakhteman A, Nadri H, Shafiee A (2012) Bioorg Med Chem
20:7160
¨
13. Kus¸ C, Ayhan-Kılcıgil G, Ozbey S, Kaynak FB, Kaya M, C¸ oban
T, Can-Eke B (2008) Bioorg Med Chem 16:4294
4,5-Diphenyl-2-(thiophen-2-yl)-1-(p-tolyl)-1H-imidazole (4n,
¨
¨
14. Tolle P, Cavalcanti WL, Hoffmann M, Kohler C, Frauenheim T
(2008) Fuel Cells 8:236
15. Kreuer KD, Fuchs A, Ise M, Spaeth M, Maier J (1998) Elec-
trochim Acta 43:1281
C26H20N2S) White solid; m.p.: 201–203 °C; FT-IR (KBr):
1
vꢀ = 3433, 3059, 2917, 1600, 1512, 1226 cm-1; H NMR
(400 MHz, DMSO-d6): d = 2.30 (s, 3H, –CH3), 6.49–7.44
(m, 17H) ppm; 13C NMR (75 MHz, DMSO-d6):
d = 125.2, 126.2, 126.4, 127, 127.4, 128.1, 128.4, 128.7,
129.4, 129.9, 130, 131, 131.2, 132.9, 133.4, 134, 136.7,
139, 141.4 ppm.
16. Mohammadi Ziarani G, Badiei A, Lashgari N, Farahani Z (2016)
J Saudi Chem Soc 20:419
17. Mohammadi Ziarani G, Dashtianeh Z, Shakiba Nahad M, Badiei
A (2015) Arabian J Chem 8:692
18. Gholamzadeh P, Mohammadi Ziarani G, Lashgari N, Badiei A,
Asadiatouei P (2014) J Mol Catal A: Chem 391:208
19. Akbari A (2016) Tetrahedron Lett 57:431
20. Esmaeilpour M, Javidi J, Zandi M (2015) New J Chem 39:3388
21. Sharma GVM, Jyothi Y, Lakshmi PS (2006) Synth Commun
36:2991
22. Zhu Y, Stubbs LP, Ho F, Liu R, Ship CP, Maguire JA, Hosmane
NS (2010) ChemCatChem 2:365
23. Xie Y, Wei Z, Liu C-J, Cui L, Wang C (2012) J Colloid Interface
Sci 374:40
24. Wei Z, Liu C-J (2011) Mater Lett 65:353
25. Maleki B, Shirvan HK, Taimazi F, Akbarzadeh E (2012) Int J
Org Chem 2:93
1-(4-Methoxyphenyl)-4,5-diphenyl-2-(thiophen-2-yl)-1H-im-
idazole (4o, C26H20N2OS) White solid; m.p.: 189–191 °C;
FT-IR (KBr): vꢀ = 3104, 3064, 2929, 1607, 1512,
1
1254 cm-1; H NMR (400 MHz, DMSO-d6): d = 3.75 (s,
3H, OCH3), 6.55–7.51 (m, 17H) ppm; 13C NMR (75 MHz,
DMSO-d6): d = 55.3, 114.4, 125.2, 126.2, 126.4, 127,
127.4, 128.1, 128.4, 128.5, 130.1, 130.2, 131, 131.4, 132.9,
134.1, 136.6, 141.6, 159.5 ppm.
26. Sivakumar K, Kathirvel A, Lalitha A (2010) Tetrahedron Lett
51:3018
27. Karimi AR, Alimohammadi Z, Azizian J, Mohammadi AA,
Mohammadizadeh MR (2006) Catal Commun 7:728
1-(4-Chlorophenyl)-4,5-diphenyl-2-(thiophen-2-yl)-1H-imi-
dazole (4p, C25H17ClN2S) White solid; m.p.: 216–218 °C;
FT-IR (KBr): vꢀ = 3430, 3055, 1600, 1580, 1490 cm-1; 1H
NMR (400 MHz, DMSO-d6): d = 6.58–7.54 (m, 17H)
123

R. Ghorbani-Vaghei et al.
28. Zolfigol MA, Baghery S, Moosavi-Zare AR, Vahdat SM (2015)
RSC Adv 5:32933
31. Ghorbani-Vaghei R, Izadkhah V, Mahmoodi J (2017) Res Chem
Intermed 43:2299
29. Kidwai M, Mothsra P (2006) Tetrahedron Lett 47:5029
30. Windels CE (2000) Phytopathology 90:17
32. Ghorbani-Vaghei R, Sarmast N, Mahmoodi J (2016) Appl
Organomet Chem 31:e3681
123