A novel ionic liquid based on imidazolium cation as an efficient and reusable catalyst for the one-pot synthesis of benzoxazoles, benzthiazoles, benzimidazoles and 2-arylsubstituted benzimidazoles

Article abstract of DOI:10.1002/jccs.201400372

A novel dicationic ionic liquid based on imidazolium cation is designed, synthesized and successfully used as catalyst for the one-pot synthesis of benzoxazoles, benzthiazoles, benzimidazoles and 2-arylsubstituted benzimidazoles. The remarkable feature of this new catalyst is its ethyleneoxy bridge which participates in dissolving organic compound in ionic liquid. The application of this ionic liquid is studied in a new one-pot method for synthesis of heterocyclic compounds under solvent-free conditions. Simple and convenient procedure, high conversion, reusability of catalyst, easy purification and shorter reaction time are the advantageous features of this method.

Full text of DOI:10.1002/jccs.201400372

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
A Novel Ionic Liquid Based on Imidazolium Cation as an Efficient and Reusable
Catalyst for the One-pot Synthesis of Benzoxazoles, Benzthiazoles, Benzimidazoles
and 2-Arylsubstituted Benzimidazoles
Maede Hasanpour, Hossein Eshghi,* Mehdi Bakavoli and Mahdi Mirzaei
Department of Chemistry, School of Sciences, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran
(Received: Sept. 3, 2014; Accepted: Dec. 25, 2014; Published Online: ??; DOI: 10.1002/jccs.201400372)
A novel dicationic ionic liquid based on imidazolium cation is designed, synthesized and successfully
used as catalyst for the one-pot synthesis of benzoxazoles, benzthiazoles, benzimidazoles and 2-arylsub-
stituted benzimidazoles. The remarkable feature of this new catalyst is its ethyleneoxy bridge which par-
ticipates in dissolving organic compound in ionic liquid. The application of this ionic liquid is studied in a
new one-pot method for synthesis of heterocyclic compounds under solvent-free conditions. Simple and
convenient procedure, high conversion, reusability of catalyst, easy purification and shorter reaction time
are the advantageous features of this method.
Keywords: Ionic liquid; Imidazolium cation; Benzoxazoles; Benzthiazoles; Benzimidazoles; Reus-
able catalyst.
INTRODUCTION
Benzo-fused heterocyclic systems such as benzimi-
rate, selectivity, and tendency to immobilize starting mate-
rials and catalyst.22–25
dazoles, benzoxazoles and benzothiazoles have been inter-
ested in numerous synthetic studies due to their diverse bi-
ological and therapeutic activities such as antitumor,1
antimicrobial,2 antivirus,3,4 anti-bacterial,5 anti-Parkin-
son,6 anti-cancer.7 Because of their great importance, many
synthetic routes have been developed. The most popular
methods generally involve the condensation of o-phenyl-
enediamines, 2-aminothiophenol and 2-aminophenol with
carboxylic acid derivatives under strong acid and high tem-
perature conditions.8–10 Another method is the condensa-
tion of an aldehyde with 2-aminothiophenol and 2-amino-
phenol in the presence of oxidative reagent and catalyst
such as In(OTf)3,11 MnO2,12 Fe(HSO4)3,13 DDQ,14,15 co-
balt(III)–salen complex supported on activated carbon,16
Sc(OTf)3,17 H2O2/Fe(NO3)3,9 H2O2/CAN18 and 4-methoxy-
TEMPO.19 Many of these reagents are expensive, corrosive
or toxic with protocols that require long reaction times and
tedious work-up. In other hand the importance of green re-
actions in organic synthesis has encouraged scientists to
explore the use of room-temperature ionic liquids (RTILs),
particularly those based on imidazolium cations,20,21 as a
powerful alternative to the conventional molecular organic
solvents or catalysts, due to some of the unique physical
and chemical properties such as thermal stability, negligi-
ble vapor pressure, recyclability, ability to dissolve a wide
range of organic and inorganic compounds, fast reaction
In recent year dicationic ILs would be interesting re-
search targets due to their high thermal stability, broad liq-
uid range, and biological activities such as antiviral, anti-
fungal and anticancer activities. In particular, imidazolium
based dicationic ILs showing high thermal stability were
used as effective reaction media for high temperature or-
ganic reactions.26–29 In continuations of our previous works
about design and synthesize of the novel ionic liquids and
use of these in organic synthesis, as catalyst and sol-
vent,30,31 we became interested in the synthesis of another
novel dicationic ionic liquid and application of this novel
catalyst as new and efficient method for the synthesis of
benzimidazoles, benzoxazoles and benzothiazoles in the
presence of catalytic amount of this novel ionic liquid un-
der solvent-free conditions. In designing this novel ionic
liquid we used 1,2-bis(2-chloroethoxy)ethane as a linker
between imidazolium rings that participates in dissolving
of organic compound in ionic liquid. We believe that this
novel ionic liquid can be applied as catalyst in many differ-
ent organic transformations.
RESULTS AND DISCUSSION
Preparation and characterization of dicationic ionic
liquid
We designed and synthesized a novel ionic liquid
based on imidazolium cations with a triethylenoxy spacer.
* Corresponding author. Telfax: +00985138795457; Email: heshghi@um.ac.ir
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Hasanpour et al.
1,2-bis(2-(1H-imidazol-1-yl)ethoxy)ethane (1) has been
synthesized according to our previously published method.32
This compound (1) is then converted into the novel ionic
liquid by the reaction with propyl bromide, and ionic liq-
uid (2) was obtained in 96% yield as viscous oil (Scheme
1).
Synthesis of 2-arylsubstituted benzimida-
zoles
Scheme 3
Molecular geometry of the novel ionic liquid
Scheme 1 Synthesis of dicationic ionic liquid
The optimized geometry of synthesized dicationic
ionic liquid is shown in Figure 2 and the minimum-energy
geometries of the novel ionic liquid were computed by per-
forming ab initio geometry optimizations at the RHF/6-
31G level of theory. All calculations were carried out using
Gaussian 09.47 The optimized molecular structure of the
novel ionic liquid is demonstrated in Figs. 1 and 2 (top
view). The results are shown in Table 3. This optimized
structure reveals that, the most stable form of the novel
ionic liquid is anti-direction of bromide ions in addition to
the anti-direction of two imidazolium rings toward each
other. The distances of bromide ion from hydrogen and ni-
In designing of this novel ionic liquid, propyl group
that is covalently bonded to the imidazolium rings, help to
increase hydrophobicity of ionic liquid, also short oligo
(ethylene glycol) chain that is used as linker between two
imidazolium ring increase flexibility and hydrophobicity.
In addition this synthesized dicationic ionic liquid is hydro-
philic in nature. Oligo chain spacer responsible of hydro-
philicity. Actually the oxygen atoms in ethyleneoxy bridges
act as hydrogen bond acceptor and also help to form strong
hydrogen bond with organic compounds and polar sol-
vent.32,33 This feature lead to dissolving polar organic com-
pounds and enhance the significant catalytic activity of this
novel dicationic ionic liquid in organic transformations.
The application of this ionic liquid is studied in a new one-
pot method for the synthesis of benzimidazoles, benzo-
xazoles and benzothiazoles from o-phenylenediamines,
2-aminothiophenol, 2-aminophenol, di amino pyrimidins
and triethyl orthoformate in the presence of catalytic
amount of this novel ionic liquid under solvent-free condi-
tions (Scheme 2). Also this study shows that this novel
ionic liquid is an efficient catalyst in the synthesis of the 2-
arylsubstituted benzimidazoles from o-phenylenediamine
and various aromatic aldehydes in the same above condi-
tion (Scheme 3). The corresponding desired products were
isolated in excellent yields and the results are summarized
in Table 1 and Table 2, respectively.
Synthesis of benzimidazoles, benzoxazoles
and benzothiazoles
Scheme 2
2
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A Novel Dicationic Ionic Liquid
trogen of imidazolium ring, for two active sites, are (H49-
molecular structure of intermediate (1) was computed by
performing ab initio geometry optimizations at the Freq-
RHF/6-31G level of theory. The optimized structure of this
intermediate is demonstrated in Figs. 3 and 4 (top view).
Then, two equivalent benzaldehyde molecules in the pres-
ent of two active sites of ionic liquid (3) were optimized
Br58 = 2.80156 Å), (H39-Br57 = 2.80156 Å), (N35-Br58
=
3.83383 Å) and (N36-Br57 = 3.83360 Å) showing the sym-
metrical structure of this novel ionic liquid. The distance of
bromide ion from the imidazolium ring hydrogen ((N)2C-
H) was confirmed that, hydrogen bond is present between
cationic and anionic moiety in synthesized ionic liquid.
In a possible mechanism, the acidic hydrogen of the
imidazolium cation forms hydrogen bond with the oxygen
of triethyl orthoformate and the carbonyl component.48 For
more investigation about these interactions, the optimized
Fig. 2. Top view of optimized molecular structure of
ionic liquid (2) using RHF/6-31G.
Fig. 1. Optimized molecular structure of ionic liquid
(2) using RHF/6-31G.
Fig. 3. Optimized molecular structure of intermediate
(1) using Freq-RHF/6-31G.
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Article
Hasanpour et al.
Table 3. The geometry parameters of ionic liquid calculated at
RHF/6-31G level of theory
between two nitrogen atoms for two active sites of interme-
diate (1) and benzaldehyde in the present of ionic liquid (3)
are (C3-H7 = 1.06986 Å), (C30-H33 = 1.06986 Å), (C3-H7 =
1.07269 Å), and (C30-H33 = 1.07269 Å), respectively. As
the results show, the bond lengths are longer than interme-
diate (1). This difference represents a hydrogen bond formed
between carbonyl group and (N)2C-H part of the ionic liq-
uid. By comparing vibrational frequency of (N)2C-H bond
for two optimized structures, (n1 = 3 454.19 cm-1) and (n3 =
3418.76 cm-1), it could be confirmed that the formation of
new hydrogen bond is occurred. Hydrogen bond formation
of (N)2C-H with carbonyl group leads to a longer bond
length and thus vibration of carbon-hydrogen bond at
lower frequencies, in other words a blue shift. If the bond
length of (N)2C-H---O is closer to 1.8 Å and H-C-O angle
is closer to 180°, a stronger hydrogen bond is formed as
mentioned by Li et al.49 The bond distance of (N)2C-H---O
for two active sites of ionic liquid are (H7-O83 = 2.08112 Å)
and (H33-O69 = 2.08106 Å). Also, bond angles C=O---H are
(H7-C82-O83 = 157.23106°) and (H33-C68-O69 = 157.23017°)
that is suitable bond angle for formation of hydrogen bond
between oxygen atom and hydrogen atom of (N)2C-H
bond.
Parameter[a],[b]
(N)2C-H
C3-H7 = 1.08716
C30-H33 = 1.08716
(N)2C-H---Br
H---Br
N---Br
H7-Br58 = 2.30399 H33-Br57 = 2.30426
H49-Br58 = 2.80156 H39-Br57 = 2.80156
N35-Br58 = 3.83383 N36-Br57 = 3.83360
N-H---Br (angle)
C3-H7-Br58
=
C30-H33-Br57
150.51692
=
150.54922
-6207.59302753
24.1852
E (a.u.)
Dipole Moment (D)
[a] Bond distance (Å), [b] Angles (deg)
and the calculation were carried out at Freq-RHF/6-31G,
the optimized structure is shown in Figs. 5 and 6 (top view).
The most stable forms of intermediate (1) and (3) are anti-
direction of imidazolium ring in addition to the two benz-
aldehyde molecules that are anti toward each other (Fig. 6).
Some parameters of these optimized molecular structures
summarized in Table 4. The hydrogen-carbon bond length
Thereby the electrophilicity of the carbon in triethyl
orthoformate and various aldehydes is increased due to the
formation of the intermediates 1 and 2 that is shown in
Scheme 4 and 5 respectively. The suggested mechanism
Fig. 4. Top view of optimized molecular structure of
intermediate (1) using Freq-RHF/6-31G.
Fig. 5. Optimized molecular structure of benzalde-
hyde in the present of ionic liquid (3) using
Freq-RHF/6-31G.
Fig. 6. Top view of optimized molecular structure of
benzaldehyde in the present of ionic (3) liquid
using Freq-RHF/6-31G.
Table 4. The geometry parameters of intermediate (1) and benzaldehyde in the present of ionic liquid (3) calculated
at Freq-RHF/6-31G basis set
Parameter[a],[b]
1
1
3
3
(N)2C-H
C3-H7 = 1.06986 C30-H33 = 1.06986
C3-H7 = 1.07269
H7-O83 = 2.08112
H7-C82-O83 = 157.23106 H33-C68-O69 = 157.23017
C30-H33 = 1.07269
H33-O69 = 2.08106
(N)2C-H---O
C=O---H (angle)
(N)2C-H (í)
E (a.u.)
-
-
-
-
3454.19
-1067.3837
0.2867
3418.76
-1754.32008
7.6433
Dipole Moment (D)
[a] Bond distance (Å), [b] Angles (deg)
4
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A Novel Dicationic Ionic Liquid
The suggested mechanism and the hydrogen
bond interaction of an imidazolium cation
with the oxygen of triethyl orthoformate
In order to illustrate the merit of the novel ionic liquid
in comparison with other reported results, we compared the
results and reaction conditions of this work with some
other methods reported in the literature used in the synthe-
sis of 2-arylsubstituted benzimidazoles (Table 3). As
shown in Table 3, this novel ionic liquid is an effective,
green and eco-friendly catalyst with high catalytic activity
and short reaction time for the synthesis of 2-arylsubsti-
tuted benzimidazoles. One of the most important advan-
tages of this novel ionic liquid is its ability as solvent and
dissolving of organic compound with formation of hydro-
gen bond with the oxygen of ethyleneoxy bridge.
Scheme 4
Recycling of dicationic ionic liquid
One of the advantages of this novel ionic liquid is its
ability to be recycled from the reaction medium. In the syn-
thesis of benzoxazoles, benzthiazoles, benzimidazoles
from triethyl orthoformate, the catalyst was separated eas-
ily by washing with ethyl acetate and gave 93% yields (Ta-
ble 4). Also after the completion of the preparation reaction
of 2-arylsubstituted benzimidazoles, the catalyst was re-
covered by washing the aqueous layer thoroughly whit
ethyl acetate and evaporation of the water at 50–60 °C in a
vacuum oven and gave 90% yields and reused for the same
experiment for five times (Table 5).
The suggested mechanism and the hydrogen
bond interaction of an imidazolium cation
with the oxygen of carbonyl group in vari-
ous aldehydes
Scheme 5
Table 5. Recycling of ionic liquid in the synthesis of benzimid-
azoles
Reusability[a]
Yield (%)[g]
IL
93
1[b]
90
2[c]
90
3[d]
87
4[e]
80
5[f]
80
[a] Reusability of the recovered catalyst. [b]-[f] Reusability of the
recovered catalyst in new runs from run 2(b) to run 5(f). [g] Iso-
lated yield.
Table 6. Recycling of ionic liquid in the synthesis of 2-arylsub-
stituted benzimidazoles
Reusability[a]
Yield (%)[g]
IL
90
1[b]
88
2[c]
89
3[d]
85
4[e]
80
5[f]
82
[a] Reusability of the recovered catalyst. [b]-[f] Reusability of the
recovered catalyst in new runs from run 2(b) to run 5(f). [g] Iso-
lated yield.
could be explained the treatment of differently substituted
aldehydes depicted in Table 2 for the synthesis of 2-aryl-
substituted benzimidazoles. Electron-withdrawing groups
on benzaldehyde accelerate the reaction rate in comparison
to electron-donating groups which decrease the rate.
EXPERIMENTAL
Materials and instrumentation: All reagents were pur-
chased from Merck Company and used without further purifica-
tion. The melting points of products were determined with an
Electrothermal Type 9100 melting point apparatus. The FT-IR
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Hasanpour et al.
spectra were recorded on an Avatar 370 FT-IR Therma Nicolet
spectrometer. The mass spectra were recorded on a 5973 Network
tored by thin-layer chromatography, TLC), the mixture was
cooled to room temperature and extracted thoroughly with ethyl
acetate (3 × 10 mL). The combined organic layer was washed
with water (2 × 20 mL), dried with anhydrous Na2SO4, and the
solvent was removed under reduced pressure to afford the crude
product, which was purified by recrystallization from ethyl ace-
tate and n-hexane. The catalyst which does not dissolve in ethyl
acetate, remain in residue.
1
Mass Selective Detector. The H and 13C NMR spectra were re-
corded on a Bruker DRX-400 Avance spectrometers at 400 MHz,
using DMSO-d6 or CDCl3 as the deuterated solvents. Chemical
shifts are reported in ppm downfield from TMS as internal stan-
dard; coupling constants J are given in Hertz.
Synthesis of 1,2-bis(2-(1H-imidazol-1-yl)ethoxy)ethane
(1): Amixture of imidazole (32 mmol, 2.176 g) and potassium hy-
droxide (32 mmol, 1.792 g) in DMSO (25 mL) was stirred at 70
°C for one hour. After this time 1,2-bis(2-chloroethoxy)ethane
(16 mmol, 2.48 mL) was added to the reaction mixture and stirred
for 24 h. The resulting mixture was poured into 100 mL of water
and extracted with methylene chloride (5 × 20 mL). The com-
bined organic layer was washed with water (3 × 20 mL), dried
with anhydrous Na2SO4, and concentrated to give the 1,2-bis(2-
(1H-imidazol-1-yl)ethoxy)ethane (1) as a pale yellow viscous oil,
General procedure for preparation of 2-arylsubstituted
benzimidazoles: A mixture of 2-aminothiophenol (1 mmol), an
appropriate aldehyde (1 mmol) and ionic liquid (0.05 mmol) was
stirred at 80 °C for 5–20 min. The progress of the reaction was
monitored by TLC. When the reaction was completed, the mix-
ture was cooled to room temperature and water (20 mL) was
added to the mixture. The resulting solid product was filtered and
washed with water. The crude product purified by recrystalliza-
tion from ethyl acetate and n-hexane or ethanol.
1
3.10 g, 77% yield. H NMR (CDCl3, 400 MHz) d: 3.45 (s, 4H),
Selected spectroscopic data
3.59 (t, 4H, J = 4.8 Hz), 4.01 (t, 4H, J = 4.8 Hz), 6.90 (t, 2H, J =
1.2 Hz), 6.94 (t, 2H, J = 1.2 Hz), 7.45 (s, 2H). 13C NMR (CDCl3,
400 MHz) d: 46.98, 70.38, 70.49, 119.39, 128.93, 137.48. IR
(KBr, cm-1): 1642, 1525, 1425. m/z, calcd. for C12H18N4O2[M]+:
250.30, found: 250.0.
1H-benzo[d]imidazole (1a): mp 173 °C. 1H NMR (CDCl3,
400 MHz) d: 7.31-7.35 (m, 2H), 7.69-7.73 (m, 2H), 8.19 (s, 1H),
11.02 (s, 1H). 13C NMR (CDCl3, 400 MHz) d: 115.55, 122.91,
137.72, 140.69. IR (KBr, cm-1): 3113, 3062, 2968, 2863, 1580,
1477, 1458, 1364, 1245, 1139, 958, 745, 628. 5-nitro-1H-benzo-
[d]imidazole (2a): mp 202 °C. IR (KBr, cm-1): 3103, 3027, 2966,
1621, 1593, 1516, 1465, 1342, 1267, 1067, 952, 816, 739, 624.
2-(Methylthio)-1H-purin-6(7H)-one (5a): mp 292 °C. IR (KBr,
cm-1): 3121, 3031, 2933, 1711, 1695, 1577, 1462, 1359, 1227,
1115, 959, 878, 781, 673. m/z, calcd. for C6H6N4OS [M]+: 182.03,
Synthesis of 1,1¢-((ethane-1,2-diylbis(oxy))bis(ethane-
2,1-diyl))bis(3-propyl-1H-imidazol-3-ium) bromide (2): A 25
mL round-bottomed flask was charged with 1,2-bis(2-(1H-imi-
dazol-1-yl)ethoxy)ethane (1) (12.4 mmol, 3.1 g) and 1-bromopro-
pane (24.8 mmol, 3.05 g) without any solvent was stirred at 70 °C
for 24 hours. After this time, the reaction mixture was cooled to
room temperature, the residue was washed with dry CH2Cl2 (3 ×
20 mL) and dried under vacuum to give 1,1¢-((ethane-1,2-diyl-
bis(oxy))bis(ethane-2,1-diyl))bis(3-propyl-1H-imidazol-3-ium)
1
found: 182.0. Thiazolo[4,5-b]quinoxaline (7a): mp 181 °C. H
NMR (CDCl3, 400 MHz) d: 7.88-7.92 (m, 2H), 8.22-8.24 (m,
1H), 8.33-8.36 (m, 1H), 9.69 (s, 1H). 13C NMR (CDCl3, 400
MHz) d: 128.41, 130.03, 130.25, 130.43, 141.13, 141.18, 151.73,
156.13, 163.36. IR (KBr, cm-1): 3060, 1544, 1463, 1324, 1301,
1241, 1143, 1127, 1059, 902, 838, 770, 759, 733, 669. m/z, calcd.
for C9H5N3S [M]+: 187.02, found: 187.0. 5-Nitrobenzo[d]oxazole
(9a): mp 113 °C. 1H NMR (DMSO-d6, 400 MHz) d: 8.03 (d, 1H, J
= 8.8 Hz), 8.34 (d, d, 1H, J = 2 Hz), 8.66 (d, 1H, J = 2.4 Hz),
9.03(s, 1H). 13C NMR (DMSO-d6, 400 MHz) d: 112.55, 116.76,
122.09, 140.52, 145.41, 153.53, 157.82. IR (KBr, cm-1): 3117,
3068, 1670, 1521, 1430, 1342, 1298, 115, 1038, 913, 824, 794,
739,687,620. m/z, calcd. for C7H4N2O3 [M]+: 164.02, found:
164.0. 2-(4-Nitrophenyl)-1H-benzo[d]imidazole (2b): mp 200
°C. IR (KBr, cm-1): 3059, 2962, 2918, 1603, 1515, 1434, 1341,
1280, 1103, 855, 743. 2-(4-Isopropylphenyl)-1H-benzo[d]imi-
dazole (5b): mp 248 °C. 1H-NMR (DMSO-d6, 400 MHz) d: 1.24
(d, J = 6.8 Hz, 6H, CH3), 2.92-2.99 (m, 1H, CH), 7.18-7.20 (m,
2H, Ar-H), 7.42 (d, J = 8.0 Hz, 2H, Ar-H), 7.57-7.59 (m, 2H,
1
bromide (2) as a viscous yellowish oil, 2.37 g, 96.3%, yield. H
NMR (DMSO-d6, 400 MHz) d: 0.809 (t, 6H, J = 7.2 Hz), 1.74-
1.89 (m, 4H), 3.52 (s, 4H), 3.76 (t, 4H, J = 4.8 Hz), 4.207 (t, 4H, J
= 6.8 Hz), 4.38 (t, 4H, J = 4.8 Hz), 7.84 (d, 2H, J = 1.2 Hz), 7.90
(s, 2H), 9.39 (s, 2H). 13C NMR (DMSO-d6, 400 MHz) d: 10.77,
23.38, 49.18, 50.66, 68.55, 69.85, 122.69, 123.16, 136.74. IR
(KBr, cm-1): 3137, 3075, 2965, 2876, 1630, 1563, 1456, 1167,
1113, 768, 643. m/z, calcd. for C18H32Br2N4O2 [M]+: 496.2, found:
495.8.
General procedure for preparation of benzoxazoles,
benzthiazoles, benzimidazoles: A 10 mL round-bottom flask
was charged with the mixture of o-phenylenediamines, or 2-ami-
nothiophenol or 2-aminophenol (1 mmol), triethyl orthoformate
(1.2 mmol) and ionic liquid (0.05 mmol). The mixture was stirred
at 80 °C for 5–20 min. After completion of the reaction (moni-
6
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JOURNAL OF THE CHINESE
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A Novel Dicationic Ionic Liquid
7. Kumar, D.; Jacob, M. R.; Reynolds, M. B.; Kerwin, S. M.
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Ar-H), 8.10 (d, J = 8.4 Hz, 2H, Ar-H), 12.69 (bs, 1H, NH).
13C-NMR (DMSO-d6, 100 MHz) d: 24.14, 33.81, 115.89, 122.42,
126.96, 127.35, 128.24, 150.83, 151.80. IR (KBr, cm-1): 3070,
2961, 2923, 2864, 1621, 1498, 1373, 1279, 1112, 966, 843, 741.
m/z, calcd. for C16H16N2 [M]+: 236.13, found: 236.0. 4-(1H-
benzo[d]imidazol-2-yl)-N,N-dimethylaniline (6b): mp 295 °C. IR
(KBr, cm-1): 3101, 3056, 2929, 2851, 2806, 1610, 1504, 1439,
1368, 1202, 939, 747. m/z, calcd. for C15H15N3 [M]+: 237.13,
found: 237.0.
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13. Eshghi, H.; Rahimizadeh, M.; Shiri, A.; Sedaghat, P. Bull.
Korean Chem. Soc. 2012, 33, 515.
4-(1H-benzo[d]imidazol-2-yl)-N,N-diethylaniline (7b):
mp 230 °C. 1H NMR (CDCl3, 400 MHz) d: 1.19 (t, 6H, J = 7.2 Hz,
CH3), 3.37-3.42 (m, 4H, CH2), 5.59 (bs, 1H, NH), 6.68 (dd, 2H, J1
= 7.2 Hz, J2 = 2 Hz, Ar-H), 7.18-7.20 (m, 2H, Ar-H), 7.56-7.58
14. Eynde, J. J.; Delfosse, F.; Lor, P.; Haverbeke, Y. Tetrahedron
1995, 51, 5813.
(m, 2H, Ar-H), 7.96 (dd, 2H, J1 = 6.8 Hz, J2 = 2 Hz, Ar-H). 13
C
15. Lee, K. J.; Janda, K. D. Can. J. Chem. 2001, 79, 1556.
16. Sharghi, H.; Aberi, M.; Doroodmanda, M. M. Adv. Synth.
Catal. 2008, 350, 2380.
NMR (CDCl3, 400 MHz) d: 12.57, 44.38, 111.35, 114.48, 115.76,
122.22, 128.09, 149.16, 152.70. IR (KBr, cm-1): 3415, 3064,
2974, 2929, 2888, 1608, 1501, 1451, 1355, 1268, 1199, 1008,
820, 748. m/z, calcd. for C17H19N3 [M]+: 265.16, found: 265.0.
2-(Naphthalen-1-yl)-1H-benzo[d]imidazole (9b): mp 264 °C. 1H
NMR (DMSO-d6, 400 MHz) d: 7.25-7.27 (m, 2H, Ar-H), 7.59-
7.64 (m, 2H, Ar-H), 7.65-7.75 (m, 2H, Ar-H), 8.01-8.06 (m, 2H,
Ar-H), 8.10 (d, 1H, J = 8 Hz, Ar-H), 9.11 (dd, 1H, J1 = 8 Hz, J2 =
1.2 Hz, Ar-H), 12.85 (bs, 1H, NH), 13C NMR (DMSO-d6, 400
MHz) d: 111.82, 119.54, 122.17, 122.97, 125.74, 126.80, 127.53,
127.98, 128.32, 128.85, 130.60, 130.96, 134.07, 151.80. IR (KBr,
cm-1): 3048, 2974, 2872, 1593, 1531, 1449, 1402, 1361, 1281,
1229, 1037, 955, 804, 774, 748, 657. m/z, calcd. for C17H12N2
[M]+: 244.10, found: 244.0.
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ACKNOWLEDGEMENTS
We are grateful to Ferdowsi University of Mashhad
Research Council for their financial support of this work
(GN: 3/28349).
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J. Chin. Chem. Soc. 2015, 62, 000-000