A new method for synthesis of 2, 4, 5-triaryl-1H-imidazole derivatives using SiO2-NaHSO4 under solvent-free conditions

Article abstract of DOI:10.13005/ojc/300143

A mixture of benzyl, aromatic aldehyde and ammonium acetate in presence of SiO₂-NaHSO₄ under solvent-free condition were converted to 2, 4, 5-Triaryl H-Imidazoles. The short reaction time, cleaner reaction, and easy workup make this

Full text of DOI:10.13005/ojc/300143

ISSN: 0970-020 X
CODEN: OJCHEG
2014, Vol. 30, No. (1):
Pg. 329-331
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
A New Method for Synthesis of 2,4,5-Triaryl-1H-Imidazole
Derivatives using SiO2-NaHSO4 under Solvent-free Conditions
FARHAD HATAMJAFARI and HADISEH KHOJASTEHKOUHI*
Department of Chemistry, Faculty of Science, Islamic Azad University,
Tonekabon Branch, Tonekabon, Iran.
*Corresponding author E-mail: hadiseh00@gmail.com
http://dx.doi.org/10.13005/ojc/300143
(Received: December 13, 2013; Accepted: January 10, 2014)
AbSTRACT
A mixture of benzyl, aromatic aldehyde and ammonium acetate in presence of SiO2-NaHSO4
under solvent-free condition were converted to 2,4,5-Triaryl-1H-Imidazoles.The short reaction time,
cleaner reaction, and easy workup make this protocol practical and economically attractive.
Key words: Imidazoles, Solvent-free, Multicomponent reactions, SiO2-NaHSO4
INTRODUCTION
which has made them privileged structures in
combinational drug discovery libraries. They have
the biological roles and also found application as a
chromophore with high extinction coefficient, readily
tunable absorption wavelength, and fluorophoric
properties and was desirable as a large planar
synthetic building block in supramolecular chemistry.
Recently, several improved methodologies have
been developed that use HY/silica gel, acidic Al2O3,
AcOH, ionic liquid, NH4OAc, sodium bisulfate among
others5-8.Previously, we have synthesized a number
Multicomponent reactions (MCRs) refers
to a reaction in which two or more ingredients are
combined within a single process and the products
they create, which is part of all the components are
present1-3. Since the multi-component reactions
for the synthesis of organic compounds and these
compounds can be used as a drug and precursor
multicomponent reactions, so to investigate them
out is important4.
of heterocyclic compounds9-17
.
Imidazoles are important heterocycle
compounds in medicinal chemistry. Imidazoles
widely have been used of biological activity
In this study, we have used of SiO2-NaHSO4
asacatalyststodevelopanewandeasymethodology

330
HATAMJAFARI & KHOJASTEHKOUHI, Orient. J. Chem., Vol. 30(1), 329-331 (2014)
for the synthesis of 2,4,5-triaryl imidazole derivatives. 3000(CHarom Str.);1600(C=C Str.);1470(C=N Str.).
The experiments were started with the study of 1H NMR (400.13 MHz CDCl3) d (ppm):7.22-7.49(14H,
one-pot, a simple, mild and efficient method for the m, CHarom), 7.94(2H,d,J=8Hz,2CH), 9.40(H, s, NH).
preparation of the 2,4,5-triarylimidazoles by using
SiO2-NaHSO4 as a catalyst (Scheme1).
2-(4-Chlorophenyl)-4,5-diphenyl-1H-imidazole
(A2)
EXPERIMENTAL
Bright crystals, Yield: 0.28 g (85%), mp:
260-262°C. IR (λmax/cm-1)(KBr): 3400(NH Str.);
All chemicals were obtained from Merck 3000(CHarom Str.); 1600(C=C Str.); 1500(C=N
or Fluka without further purification. Silica gel SILG/ Str.). 1H NMR (400.13 MHz CDCl3) d (ppm): 7.09-
UV 254 plates were used for TLC. IR spectra were 7.84 (11H,m,CHarom),7.82-7.84(2H,d,J=8Hz 2CH),
measured on a Shimadzu IR-470 Spectrophotometer. 9.53(H,s, NH).
1H NMR spectra were determined on Bruker 500 DRX
AVANCE instrument at 500 MHz, respectively.
2-(4-Methoxyphenyl)-4,5-diphenyl-1H-imidazole
(A3)
General procedure for preparation of 2a–l
Pale yellow crystals, Yield: 0.28 g (86%),
A mixture of aldehyde (1 mmol), benzil mp: 227-230°C. IR (λmax/cm-1)(KBr): 3442(NH Str.);
(1 mmol), ammonium acetate (3 mmol) and SiO2- 3070(CHarom Str.); 1599(C=C Str.); 1450(C=N
1
NaHSO4 (10 mol %) as a catalyst was stirred at 120 Str.). H NMR (400.13 MHz CDCl3) d (ppm):
oC for 30 min.The progress of reaction was monitored 3.84(3H,s,CH3);6.93(2H,d,J=8Hz, 2CH); 7.27-7.53
by TLC. After finishing, recrystallized from ethanol (10H,m,10CH),7.82(2H,d,3J=8Hz, 2CH).
95% to give pure products (A1-A4)
2-(3-Nitrophenyl)-4,5-diphenyl-1H-imidazole
spectral data
(A4)
2,4,5-Triphenyl-1H-imidazole (A1)
Pale yellow crystals, Yield: 0.3 g (88%),
Pale yellow crystals, Yield: 0.26 g (89%), mp> 300°C. IR (λmax/cm-1)(KBr): 3400(NH); 3055
mp: 274-276°C. IR (λmax/cm-1)(KBr): 3400(NH Str.); (CHarom);1600(C=C);1475(C=N);1420,1375(NO2).
H
Ph
O
N
O
O
Ph
SiO2 - NaHSO4
Solvent-free , 120 oC
Ar
2NH4OAc
+
+
N
Ar
H
Ph
Ph
1H NMR (400.13 MHz CDCl3) d (ppm):7.39-7.85(10H, Therefore, reported SiO2-NaHSO4 as catalyst which
m, CHarom); 7.98-8.0(2H , d, J=8Hz , 2CH); 8.10(1H could provide an efficient, cheap, easy separation,
, s, CH).
high yield and simple route under solvent-free
condition for the synthesis of imidazoles.
RESULTS AND DISCUSSION
ACKNOWLEDGEMENTS
We have been able to introduce an efficient
and environmentally friendly for the synthesis of
We gratefully acknowledge the financial
imidazole derivatives via condensation of benzil with support from the Research Council of Tonekabon
various aromatic aldehydes and ammonium acetate. Branch Islamic Azad University.

HATAMJAFARI & KHOJASTEHKOUHI, Orient. J. Chem., Vol. 30(1), 329-331 (2014)
331
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