Sonochemically assisted synthesis of N-substituted pyrroles catalyzed by ZnO nanoparticles under solvent-free conditions

Article abstract of DOI:10.1007/s00706-016-1904-6

Abstract: An efficient and rapid synthesis of 1,2,3,5-tetrasubstituted pyrrole derivatives from a one-pot multicomponent reaction of amines, 1,3-dicarbonyl compounds, and α-haloketones in the presence of ZnO nanoparticles catalyst under ultrasonic irradiation and solvent-free conditions is described. Graphical abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s00706-016-1904-6

Monatsh Chem
DOI 10.1007/s00706-016-1904-6
ORIGINAL PAPER
Sonochemically assisted synthesis of N-substituted pyrroles
catalyzed by ZnO nanoparticles under solvent-free conditions
Ashraf S Shahvelayati1 Maryam Sabbaghan2 Solmaz Banihashem1
•
•
Received: 5 May 2015 / Accepted: 30 December 2016
Ó Springer-Verlag Wien 2017
Abstract An efficient and rapid synthesis of 1,2,3,5-tetra-
substituted pyrrole derivatives from a one-pot multicomponent
reaction of amines, 1,3-dicarbonyl compounds, and a-haloke-
tones in the presence of ZnO nanoparticles catalyst under
ultrasonic irradiation and solvent-free conditions is described.
Graphical abstract
exist in various bioactive drugs such as antioxidant, anti-
inflammatory, antiviral, and antitumor agents [3–5].
Many methods have been developed for preparation of
pyrroles [6–9]. Despite these new developments, the clas-
sical Hantzsch reaction remains the most attractive method
for the synthesis of pyrroles [10]. Facile and green synthetic
procedures establish an important goal in organic synthesis.
Elimination of hazardous solvents, reduction of reaction
time, and using catalyst are among the most important
principles of the green chemistry [11–14]. The development
of multicomponent reactions (MCRs) in the presence of
nano-metal oxides such as ZnO nanostructures, used not
only as an environmentally benign reaction media, but also
as an efficient and reusable catalyst, is a new technique that
meets the requirements of green chemistry [15–17]. More-
over, ultrasound has increasingly been used in organic
synthesis in the last decades and a large number of organic
reactions can be carried out in higher yields, shorter reaction
time and milder conditions under it [18, 19].
Keywords Tetrasubstituted pyrrole derivatives Á
Multicomponent reaction Á ZnO nanoparticles Á
Ultrasonic irradiation Á 1,3-Dicarbonyl compounds
As part of our current studies on the development of new
routes in heterocyclic synthesis [20–22], we report an effi-
cient ultrasonic-assisted one-pot synthesis of functionalized
pyrroles 4a–4m in good yields by a three-component reac-
tion between amines 1, b-dicarbonyls 2, and a-
bromoketones 3 under solvent-free condition (Scheme 1).
Herein, ZnO nanoparticles (NPs) exhibited high activity and
products are produced in high yield in the presence of them.
Introduction
Pyrroles are considered as an important class of compounds
with different biological activities [1, 2]. The pyrrole
moiety is found in many naturally occurring compounds
such as heme, chlorophyll, and vitamin B12. Pyrroles also
& Ashraf S Shahvelayati
avelayati@yahoo.com
Results and discussion
1
Department of Chemistry, Yadegar-e-Imam Khomeini
(RAH) Shahre-rey Branch, Islamic Azad University, Tehran,
Iran
Structure and morphology of the ZnO-NPs
2
In general, a nanoparticle is considered to be more reactive
because it offers higher surface area and low coordinating
Chemistry Department, Faculty of Sciences, Shahid Rajaee
Teacher Training University, Tehran, Iran
123

A. S. Shahvelayati et al.
Scheme 1
Scheme 2
Fig. 1 Structure of dihexylimidazolium bromide
sites. The surface area of the catalyst increases tremen-
dously when the size decreases to nano levels, which is
responsible for the higher catalytic activity. Thus, we used
ZnO-NPs in preparation of tetrasubstituted pyrroles as an
efficient catalyst. The ZnO-NPs were obtained from zinc
acetate dihydrate as a zinc source, and the chemical reac-
tion can be formulated as shown in Scheme 2.
With using IL as a template, ZnO-NPs with smaller
crystallite size were obtained [23–27]. The structure of the
IL [HHIM]Br, used in this study, is shown in Fig. 1. The
characteristic results revealed that using ionic liquids in
water prevents a drastic increase in the crystallite size.
Without IL, the shielding effect of excess OH- on the
growth rate of various faces becomes slow. The structure of
these ZnO-NPs was studied using SEM and XRD (Figs. 2,
3). The figures indicate that the catalyst is consisted of pure
phases and no characteristic peaks is observed for other
impurities, such as Zn(OH)2.
Fig. 2 SEM image of ZnO-NPs
ethanol (Table 1) [28]. The structures of compounds 4a–
4m were deduced from their elemental analyses and their
1
IR, H NMR, and 13C NMR. The mass spectra of these
compounds displayed molecular ion peaks at appropriate
m/z values. The compounds 4d [29–31] and 4e, 4k [14]
1
have been reported before in the literatures. The H NMR
Catalytic activity of ZnO-NPs in the synthesis
of polysubstituted pyrroles
spectrum of 4m in CDCl3 showed three singlets in
d = 2.06, 2.27, 2.42 ppm for methyl groups, together with
one triplet and one quartet (1.18, 4.14 ppm, respectively)
for the ethoxy group, one singlet signal (7.11 ppm) for CH-
pyrrole and two doublets (6.99, 7.13 ppm) for the aromatic
protons. The 13C NMR spectrum of 4m showed 15 signals
in agreement with the proposed structure. Partial assign-
ments of these resonances are given in spectral data section
The reaction of aromatic and aliphatic amines 1, b-car-
bonyls 2, and a-bromoketones 3 under solvent-free
condition and ultrasonic irradiation was investigated to
produce pyrroles 4 in good yields and then, it was com-
pared with the reaction without catalyst under reflux in
123

Sonochemically assisted synthesis of N-substituted pyrroles catalyzed by ZnO nanoparticles…
room temperature for 24 h and used for the next catalytic
cycle.
The influence of various reaction parameters such as
solvent, catalyst loading, and time was examined. Initially
we have screened various solvents such as ethanol, ace-
tonitrile, n-hexane, and dichloromethane for 4a product
formation under reflux in the absence of catalyst (Table 2).
It was observed that the reaction proceeded very slowly
and the product yield was very low. The best result was
obtained under ultrasonic irradiation and solvent-free
conditions in the presence of ZnO-NPs at 40 °C (Table 2,
entry 6). The reaction was also studied under catalyst in the
absence of sonication, which resulted in lower product
yield at higher temperature for a longer time (Table 2,
entry 5).
Fig. 3 XRD of ZnO-NPs
1
(4m product). The H and 13C NMR spectra of the other
products are similar to those of 4m except for the alkyl and
aryl substituents, which exhibit characteristic signals in the
appropriate regions of the NMR spectra.
The catalyst loading was optimized by increasing the
amount of ZnO-NPs from 0.5 to 15% for 1 mmol scale
reaction (Table 3). The yield increased with the
increase of catalyst; however, there was a very marginal
increase when the catalyst loading increased to 20%.
Therefore, 15% catalyst was chosen as an optimal
amount.
The catalyst can be reused two times without significant
loss of activity. The reusability of the catalyst was checked
for the synthesis of ethyl 4-acetyl-5-methyl-1-(p-tolyl)-1H-
pyrrole-2-carboxylate (Table 1, entry 13). After filtering
and washing out the catalyst in each run, it was dried at
Table 1 Reaction conditions for formation of pyrroles 4a–4m: amine (1 mmol), 1,3-dicarbonyl (1 mmol), a-bromoketone (1 mmol)
Entry
R1
R2
R3
Product
Yielda/%
Yieldb/%
1
Et
Me
OEt
Me
OEt
Me
Me
Me
OEt
Me
Me
Me
OEt
Me
C6H5
4a
4b
4c
4d
4e
4f
74
90
88
87
89
94
93
87
92
89
95
94
90
92c
2
Et
C6H5
71
3
Et
4-MeO-C6H4
C6H5
70
4
C6H5CH2
C6H5CH2
C6H5
72
5
C6H5
77
6
4-Br-C6H4
4-MeO-C6H4
CO2Et
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Trace
7
C6H5
4g
4h
4i
8
C6H5
9
C6H5
CO2Et
10
11
12
13
a
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-Br-C6H4
C6H5
4j
4k
4l
CO2Et
CO2Et
4m
Yield obtained after 3 days (no catalyst, reflux under ethanol)
b
c
Yield obtained after 30 min at 40 °C (ZnO-NPs as catalyst, solvent- free, ultrasonic irradiation)
4m, yield 92% under ZnO-NPs for the first time, 90% in the second run, and 89% in the third run with recycled catalyst
123

A. S. Shahvelayati et al.
sites (Zn2?) and Lewis basic sites (O2-). In this reaction,
the Zn2? sites are interacting with carbonyl groups in 1,3-
dicarbonyl compound and a-bromoketone and O2- site of
ZnO-NPs taking up a proton of 7 to generate 8 [32, 33].
In summary, we have efficiently synthesized some
tetrasubstituted pyrrole derivatives from the one-pot three-
component reactions of amine, 1,3-diketones, and a-
bromoketones in the presence of ZnO-NPs by ultrasonic
irradiation and under solvent-free conditions. Zinc oxide
nanoparticles satisfactorily catalyzed these reactions as a
green, mild, and effective catalyst. Surprisingly, synthesis
of N-arylpyrroles only proceeded in the presence of this
catalyst under ultrasonic and solvent-free conditions, which
is among the fastest reported procedure in the literature.
We have concluded, however, that primary aromatic ami-
nes such as aniline do not react with diketones and a-
bromoketones significantly in the absence of catalyst. The
catalyst was recyclable and has been reused for three
successive runs with little loss of the catalytic activity.
Table 2 Effect of solvent and catalyst on the synthesis of pyrrole 4a
Entry Solvent/catalyst Time/h Temperature Yield/%
1
2
3
4
5
6
Ethanol/none/reflux
CH3CN/none/reflux
n-Hexane/none/reflux
CH2Cl2/none/reflux
Solvent-free/ZnO-NPs
72
Reflux
Reflux
Reflux
Reflux
80 °C
40 °C
77
72
70
72
60
72
45
6–9
0.5
74a
90a
Solvent-free/ZnO-NPs/
Ultrasonic irradiation
a
ZnO-NPs are prepared according to the experimental section
Table 3 Effect of catalyst loading on the synthesis of pyrrole 4h
under ultrasonic irradiation
Entry
ZnO/mol%
Yield/%
1
2
3
4
5
No catalyst
Trace
43
5
10
15
20
75
92
Experimental
93
All chemicals were obtained from Fluka or Merck and
were used without further purification. The IL used in this
study was 1,3-dihexylimidazolium bromide ([HHIM]Br)
synthesized according to the procedure reported in the lit-
A tentative mechanism for this transformation is pro-
posed in Scheme 3. Presumably, enaminone 5, formed by
the initial reaction of amine 1 and 1,3-dicarbonyl 2, which
attacks a-bromoketones 3 and undergoes HBr elimination
to produce 6, which is in equilibrium with the enamine
tautomer 7. Cyclization of this intermediate followed
dehydration, affords products 4. ZnO-NPs have Lewis acid
1
erature [34]; its structure was confirmed by H NMR and
FT-IR spectra.
IR spectra were obtained using Shimadzu FTIR-460
spectrometer. 1H NMR and 13C NMR spectra were
Scheme 3
123

Sonochemically assisted synthesis of N-substituted pyrroles catalyzed by ZnO nanoparticles…
CDCl3): d = 11.90, 15.95, 28.54, 38.71, 110.33, 120.92,
recorded with a Bruker DRX-300 AVANCE instrument in
CDCl3 at 300.1 and 75.4 MHz, respectively (d in ppm, J in
Hz). Mass spectra were obtained on a Finnigan MAT-8430
at 70 eV. Elemental analyses (C, H, N) were performed
with a Heraeus CHN-O-Rapid analyzer.
127.66, 128.50, 129.40, 132.89, 132.96, 135.61,
195.06 ppm; MS: m/z = 227 (M?, 24), 211 (75), 198
(100), 77 (12).
Ethyl 1-ethyl-2-methyl-5-phenyl-1H-pyrrole-3-carboxylate
(4b, C16H19NO2)
All reactions were carried out under ultrasonic irradia-
tion. Sonication was performed in a LBS2-10 FALC
ultrasonic instrument clearer with a frequency of 60 kHz
and an intensity of 285 W. The reaction flask was located
in the water bath of the ultrasonic cleaner, and the tem-
perature of the water bath was controlled at 40 °C.
Pale yellow oil; IR (KBr): vꢀ = 1709, 1515, 1455, 1375,
690 cm-1; 1H NMR (300.1 MHz, CDCl3): d = 1.21 (t, 3H,
J = 7.1 Hz, CH3), 2.42 (s, 3H, CH3), 2.65 (t, 3H, J = 7.2 Hz,
Me), 3.92 (q, 2H, J = 7.1 Hz, CH2N), 4.29 (q, 2H,
J = 7.2 Hz, CH2O), 6.48 (s, 1H, CH), 7.32-7.38 (m, 5H, 5
CH) ppm; 13C NMR (75.4 MHz, CDCl3): d = 10.51, 15.40,
17.36, 30.38, 60.91, 104.78, 108.03, 127.54, 129.81, 129.29,
132.71, 133.16, 142.10, 166.00 ppm; MS: m/z = 257 (M?,
16), 228 (83), 211 (100), 185 (23), 77 (12).
Sonochemical synthesis of ZnO-NPs
Zinc acetate was employed as a zinc source. In a typical
experiment, 0.3 g Zn(AcO)2Á2H2O (1 mmol) was added to
the template, 1.5 g dihexylimidazolium bromide, and then
0.2 g NaOH (5 mmol) was added to them. The mixture was
stirred at room temperature; then was irradiated with
ultrasound (40 kHz, 70 W) for 1.5 h under ambient con-
dition. During the irradiation, the temperature of the
reaction mixture rose to 70 °C. After irradiation, the pre-
cipitate was washed by distilled water and ethanol (96%)
several times. Finally, the ZnO sample was dried in the air
at room temperature during 24 h.
1-[1-Ethyl-5-(4-methoxyphenyl)-2-methyl-1H-pyrrole-3-
yl]ethanone (4c, C16H19NO2)
Pale yellow oil; IR (KBr): vꢀ = 1713, 1520, 1450, 1376,
;
1172, 850, 690 cm-1 1H NMR (300.1 MHz, CDCl3):
d = 1.03 (t, 3H, J = 7.2 Hz, CH3), 2.26 (s, 3H, CH3), 2.48
(s, 3H, CH3), 3.70 (s, 3H, OCH3), 3.72 (q, 2H, J = 7.2 Hz,
CH2N), 6.27 (s, 1H, CH), 6.79 (d, 2H, J = 8.2 Hz, 2 CH),
7.13 (d, 2H, J = 8.2 Hz, 2 CH) ppm; 13C NMR
(75.4 MHz, CDCl3): d = 11.79, 16.30, 28.28, 37.41,
55.93, 112.79, 119.27, 122.84, 126.15, 129.20, 134.88,
137.26, 156.90, 198.63 ppm; MS: m/z = 257 (M?, 21),
241 (80), 228 (100), 107 (18).
The morphology of ZnO-NPs was determined using
scanning electron microscopy (SEM) with a Holland Phi-
lips XL30 microscope. X-ray diffraction (XRD) analysis
was carried out at room temperature using a Holland Phi-
lips Xpert X-ray powder diffractometer with Cu Ka
radiation (k = 0.15406 nm), over the 2h collection range
of 20°–80°.
Ethyl 1-benzyl-2-methyl-5-phenyl-1H-pyrrole-3-carboxy-
late (4d) [29–31]
Yellow oil; IR (KBr): vꢀ = 1715, 1457, 1375, 761 cm-1; 1H
NMR (300.1 MHz, CDCl3): d = 1.10 (t, 3H, J = 7.1 Hz,
CH3), 2.05 (s, 3H, CH3), 4.02 (q, 2H, J = 7.1 Hz, CH2O),
4.81 (s, 2H, CH2N), 6.27 (s, 1H, CH), 6.69 (d, 2H,
J = 8.2 Hz, 2 CH), 6.87–6.93 (m, 3H, 3 CH), 7.05-7.45
(m, 5H, 5 CH) ppm; 13C NMR (75.4 MHz, CDCl3):
d = 12.06, 14.11, 43.72, 60.94, 107.82, 121.67, 126.15,
126.55, 128.48, 129.27, 129.91, 133.14, 132.72, 133.13,
136.29, 142.13, 166.05 ppm; MS: m/z = 319 (M?, 19),
273 (76), 228 (76), 91 (29).
General procedure for the synthesis of pyrrole
derivatives 4a–4m
A mixture of b-dicarbonyl compound (1 mmol), aliphatic
and aromatic amines (1 mmol), and a-haloketone (1 mmol)
and ZnO-NPs (15% mmol) was irradiated under ultrasound
at 40 °C for the appropriate time. After completion of the
reaction as indicated by TLC, the residue was purified by
column chromatography (silica gel 230–240 mesh; Merck)
using ethyl acetate/n-hexane (1:9) as eluent to afford the
pure products. All products gave satisfactory spectral data
in accordance with the assigned structures.
1-(1-Benzyl-2-methyl-5-phenyl-1H-pyrrole-3-yl)ethanone
(4e)
Yellow oil; IR (KBr): vꢀ = 1716, 1459, 1374, 761 cm-1; 1H
NMR spectrum was found to agree with the one described
in Murthy et al. [14].
1-(1-Ethyl-2-methyl-5-phenyl-1H-pyrrole-3-yl)ethanone
(4a, C15H17NO)
1-[5-(4-Bromophenyl)-2-methyl-1-phenyl-1H-pyrrole-3-
yl]ethanone (4f, C19H16BrNO)
Pale yellow oil; IR (KBr): vꢀ = 1706, 1512, 1273, 1222,
;
688 cm-1 1H NMR (300.1 MHz, CDCl3): d = 1.05 (t,
3H, J = 7.2 Hz, CH3), 2.27 (s, 3H, CH3), 2.49 (s, 3H,
CH3), 3.77 (q, 2H, J = 7.2 Hz, CH2N), 6.32 (s, 1H, CH),
7.20–7.29 (m, 5H, 5 CH) ppm; 13C NMR (75.4 MHz,
Pale yellow oil; IR (KBr): vꢀ = 1711, 1504, 1409, 1228,
696 cm-1 1H NMR (300.1 MHz, CDCl3): d = 2.43 (s,
;
3H, CH3), 2.51 (s, 3H, CH3), 6.73 (s, 1H, CH), 7.04 (d, 2H,
J = 7.8 Hz, 2 CH), 7.13–7.17 (m, 5H, 5 CH) 7.40 (d, 2H,
123

A. S. Shahvelayati et al.
J = 8.2 Hz, 2 CH) ppm; 13C NMR (75.4 MHz, CDCl3):
d = 13.84, 30.60, 117.23, 125.34, 126.81, 127.96, 128.72,
129.73, 130.40, 131.65, 131.85, 132.24, 133.81, 137.63,
199.12 ppm; MS: m/z = 355 (M??2, 56), 353 (M?, 52),
339 (100), 337 (97), 312 (23), 310 (21).
z = 369 (M??2, 58), 367 (M?, 57), 353 (100), 351 (98),
326 (19), 324 (18), 91 (24).
1-[2-Methyl-5-phenyl-1-(p-tolyl)-1H-pyrrole-3-yl]etha-
none (4k)
White powder; m.p.: 57–58 °C; IR (KBr): vꢀ = 1641, 1354,
1
1-[5-(4-Methoxyphenyl)-2-methyl-1-phenyl-1H-pyrrole-3-
yl]ethanone (4g, C20H19NO2)
1122, 686 cm-1; H NMR spectrum was found to agree
with the one described in Murthy et al. [14].
Pale yellow oil; IR (KBr): vꢀ = 1712, 1524, 1405, 1179,
763, 695 cm-1; 1H NMR (300 MHz, CDCl3): d = 2.08 (s,
3H, CH3), 2.41 (s, 3H, CH3), 3.85 (s, 3H, CH3O), 6.54 (s,
1H, CH), 6.94 (d, 2H, J = 8.1 Hz, CH2O), 7.48 (d, 2H,
J = 8.1 Hz, 2 CH), 7.26–7.52 (m, 5H, 5 CH) ppm; 13C
NMR (75 MHz, CDCl3): d = 12.95, 31.06, 55.27, 113.71,
120.40, 122.58, 125.89, 126.22, 128.03, 128.32, 129.31,
130.39, 135.19, 138.79, 158.68, 197.68 ppm; MS: m/
z = 305 (M?, 49), 289 (100), 262 (28), 107 (14).
Diethyl 5-methyl-1-(p-tolyl)-1H-pyrrole-2,4-dicarboxylate
(4l, C18H21NO4)
White powder; m.p.: 60–62 °C; IR (KBr): vꢀ = 1710, 1525,
1431, 819, 760 cm-1 1H NMR (300.1 MHz, CDCl3):
;
d = 1.32 (t, 3H, J = 7.1 Hz, CH3), 1.36 (t, 3H,
J = 7.1 Hz, CH3), 2.28 (s, 3H, CH3), 2.42 (s, 3H, CH3),
4.28 (q, 2H, J = 7.1 Hz, CH2O), 4.34 (q, 2H, J = 7.1 Hz,
CH2O), 7.13 (d, 2H, J = 8.2 Hz, 2 CH), 7.21 (s, 1H, CH),
7.27 (d, 2H, J = 8.2 Hz, 2 CH) ppm; 13C NMR
(75.4 MHz, CDCl3): d = 11.83, 14.28, 14.32, 21.09,
60.17, 60.34, 113.78, 115.88, 125.98, 126.68, 130.01,
135.38, 135.71, 138.68, 164.14, 165.35 ppm; MS: m/
z = 315 (M?, 46), 300 (19), 270 (100), 242 (65), 91 (25).
Diethyl 5-methyl-1-phenyl-1H-pyrrole-2,4-dicarboxylate
(4h, C17H19NO4)
Pale yellow oil; IR (KBr): vꢀ = 1713, 1559, 1418, 1354,
1249, 727 cm-1; 1H NMR (300.1 MHz, CDCl3): d = 1.32
(t, 3H, J = 7.2 Hz, CH3), 1.36 (t, 3H, J = 7.2 Hz, CH3),
2.30 (s, 3H, CH3), 4.31 (q, 2H, J = 7.2 Hz, CH2O), 4.32
(q, 2H, J = 7.2 Hz, CH2O), 7.24 (s, 1H, CH), 7.26–7.50
(m, 5H, 5 CH) ppm; 13C NMR (75.4 MHz, CDCl3):
d = 11.85, 14.26, 14.30, 60.18, 60.37, 113.96, 116.03,
126.17, 126.57, 128.58, 129.45, 135.22, 138.21, 164.05,
165.29 ppm; MS: m/z = 301 (M?, 57), 286 (9), 256 (100),
228 (45), 77 (16).
Ethyl 4-acetyl-5-methyl-1-(p-tolyl)-1H-pyrrole-2-carboxy-
late (4m, C17H19NO3)
White powder; m.p.: 63–64 °C; IR (KBr): vꢀ = 1699, 1396,
1164, 824, 630 cm-1 1H NMR (300.1 MHz, CDCl3):
;
d = 1.18 (t, 3H, J = 7.1 Hz, CH3), 2.06 (s, 3H, CH3), 2.27
(s, 3H, CH3), 2.42 (s, 3H, CH3), 4.14 (q, 2H, J = 7.1 Hz,
CH2O), 6.99 (d, 2H, J = 8.2 Hz, 2 CH), 7.11 (s, 1H, CH),
7.13 (d, 2H, J = 8.2 Hz, 2 CH) ppm; 13C NMR
(75.4 MHz, CDCl3): d = 12.09, 14.31, 21.11, 31.51,
60.21, 114.79, 123.54, 125.96, 127.66, 130.04, 134.89,
135.55, 138.79, 164.19, 198.97 ppm; MS: m/z (%) = 285
(M?, 63), 270 (24), 242 (75), 239 (100), 91 (22).
Ethyl 4-acetyl-5-methyl-1-phenyl-1H-pyrrole-2-carboxy-
late (4i, C16H17NO3)
Pale yellow oil; IR (KBr): vꢀ = 730, 1502, 1403, 1245,
1028, 695 cm-1; 1H NMR (300.1 MHz, CDCl3): d = 1.18
(t, 3H, J = 7.1 Hz, CH3), 2.08 (s, 3H, CH3), 2.42 (s, 3H,
CH3), 4.14 (q, 2H, J = 7.1 Hz, CH2O), 7.15 (s, 1H, CH),
7.17–7.32 (m, 3H, 3 CH), 7.33 (2H, d, J = 7.5 Hz, 2 CH)
ppm; 13C NMR (75.4 MHz, CDCl3): d = 12.11, 14.30,
31.51, 60.24, 114.99, 123.70, 126.18, 127.56, 128.70,
129.50, 134.72, 138.11, 164.13, 198.95 ppm; MS: m/
z = 271 (M?, 61), 256 (30), 228 (72), 225 (100), 77 (18).
Acknowledgements Funding was provided by Yadegar-e-Imam
Khomeini (RAH) Branch, Islamic Azad University.
References
1. Fu¨rstner A (2003) Angew Chem Int Ed 42:3528
2. Sundberg RJ, Katritzky AR, Rees CW, Scriven EFV (eds) (1996)
Comprehensive Heterocyclic Chemistry V, II, vol 2. Pergamon
Press, London
3. Narule MN, Gaidhane MK, Gaidhane PK (2013) J Pharm Res
6:626
4. Battilocchio C, Poce G, Alfonso S, Porretta GC, Consalvi S,
Sautebin L, Pace S, Rossi A, Ghelardini C, Mannelli LD, Sche-
none S, Giordani A, Francesco LD, Patrignani P, Biava M (2013)
Bioorg Med Chem 21:3695
5. Liu F, Qian X, Cui J, Xiao Y, Zhang R, Li G (2006) Bioorg Med
Chem 14:4639
1-[5-(4-Bromophenyl)-2-methyl-1-(p-tolyl)-1H-pyrrole-3-
yl]ethanone (4j, C20H18BrNO)
White powder; m.p.: 58–60 °C; IR (KBr): vꢀ = 1721, 1508,
1418, 823, 660 cm-1 1H NMR (300.1 MHz, CDCl3):
;
d = 2.24 (s, 3H, CH3), 2.34 (s, 3H, CH3), 2.71 (s, 3H,
CH3), 6.56 (s, 1H, CH), 6.76 (2H, d, J = 8.2 Hz, 2 CH),
6.84 (d, 2H, J = 8.2 Hz, 2 CH), 7.05 (d, 2H, J = 8.2 Hz, 2
CH), 7.13 (d, 2H, J = 8.2 Hz, 2 CH) ppm; 13C NMR
(75.4 MHz, CDCl3): d = 14.11, 22.69, 29.36, 110.53,
126.61, 128.03, 128.91, 129.52, 130.01, 131.25, 131.42,
131.94, 132.50, 134.60, 138.37, 198.18 ppm; MS: m/
6. Gilchrist TL (2001) J Chem Soc Perkin Trans 1:2491
7. Rao HSP, Jothilingam S (2001) Tetrahedron Lett 42:6595
8. Xue H, Ma T, Wang L, Liu G (2010) Chin Chem Lett 21:1291
9. Yuan SZ, Liu J, Xu L (2010) Chin Chem Lett 21:664
123

Sonochemically assisted synthesis of N-substituted pyrroles catalyzed by ZnO nanoparticles…
10. Moss TA, Nowak T (2012) Tetrahedron Lett 53:3056
11. Yanlong GU (2012) Green Chem 14:2091
12. Ghosh PP, Pal G, Paul S, Das AR (2012) Green Chem 14:2691
13. Sandaroos R, Damavandi S, Salimi M (2012) Monatsh Chem
143:1655
14. Murthy SN, Madhav B, Kumar AV, Rao KR, Nageswar YVD
(2009) Helv Chim Acta 92:2118
15. Bahrami K, Khodaei MM, Farrokhi A (2009) Synth Commun
39:1801
23. Li WJ, Shi EW, Zhong WZ, Yin ZW (1999) J Cryst Growth
203:186
24. Jiang Y, Zhu YJJ (2005) J Phys Chem B 109:4361
25. Liu X, Ma J, Zheng W (2011) Rev Adv Mater Sci 27:43
26. Sabbaghan M, Shahvelayati AS, Bashtani SE (2012) Solid State
Sci 14:1191
27. Sabbaghan M, Beheshtian J, Mirsaeidi SAM (2014) Ceram Int
40:7769
28. Yavari I, Ghazvini M, Azad L, Sanaeishoar T (2011) Chin Chem
Lett 22:1219
29. Li P, Zhao J, Xia Ch, Li F (2014) Org Lett 16:5992
30. Estevez V, Villacampa M, Menendez JC (2013) Chem Commun
49:591
31. Kang SY, Park E-J, Park W-K, Kim HJ, Jeong D, Jung ME, Song
K-S, Lee SH, Seo HJ, Kim MJ, Lee MW, Han H-K, Son E-J, Pae
AN, Kim J, Lee J (2010) Bioorg Med Chem Lett 20:1705
32. Hosseini-Sarvari M, Tavakolian M (2012) Appl Catal A 65:441
33. Sabbaghan M, Ghalaei A (2014) J Mol Liq 193:116
34. Vygodskii YS, Lozinskaya EI, Shaplov AS (2002) Macromol
Rapid Commun 23:676
16. Bhattacharyya P, Pradhan K, Paul S, Das AR (2012) Tetrahedron
Lett 53:4687
17. Saeidian H, Abdoli M, Salimi R (2013) C R Chim 16:1063
18. Habibi D, Nasrollahzadeh M (2013) C R Chim 16:1008
19. Zhang ZH, Li JJ, Li TSh (2008) Ultrason Sonochem 15:673
20. Yavari I, Ghazvini M, Shahvelayati AS, Ghanbari M (2011)
Phosphorus. Sulfur Relat Elem 186:134
21. Yavari I, Shahvelayati AS, Malekafzali A (2010) J Sulfur Chem
31:499
22. Shahvelayati AS, Yavari I, Delbari AS (2014) Chin Chem Lett
25:119
123