An efficient one-pot three-component synthesis of imidazol-2-ones using [Bmim]BF4 ionic liquid

Article abstract of DOI:10.1007/s13738-012-0110-7

A mild and efficient method was developed for preparation of imidazol-2-ones via one-pot three-component condensation of 1,3-cyclic diketones, aryl glyoxals and urea using [Bmim]BF₄ ionic liquid. Excellent yields, short reaction time, simple work-up, and reusability of IL are advantages of this procedure. Iranian Chemical Society 2012.

Full text of DOI:10.1007/s13738-012-0110-7

J IRAN CHEM SOC (2012) 9:933–937
DOI 10.1007/s13738-012-0110-7
ORIGINAL PAPER
An efficient one-pot three-component synthesis of imidazol-2-ones
using [Bmim]BF4 ionic liquid
•
•
•
S. Kanakaraju B. Prasanna P. Venkatanarayana
G. V. P. Chandramouli
Received: 19 December 2011 / Accepted: 16 May 2012 / Published online: 6 June 2012
Ó Iranian Chemical Society 2012
Abstract A mild and efficient method was developed for
preparation of imidazol-2-ones via one-pot three-compo-
nent condensation of 1,3-cyclic diketones, aryl glyoxals
and urea using [Bmim]BF4 ionic liquid. Excellent yields,
short reaction time, simple work-up, and reusability of IL
are advantages of this procedure.
continuously growing on simplifying the synthesis of
imidazole derivatives.
Literature survey reveals that the number of methods
[23] was reported on Biginelli reaction of 1,3-cyclic
diketones with aromatic aldehydes and urea or thiourea, but
analogous three-component condensations with participa-
tion of aryl glyoxals were not found in the literature.
One-pot multi-component condensation represents a
possible instrument for ideal synthesis because by this way
complex molecules could be built-up with maximum sim-
plicity [24, 25]. They offer significant advantages over
conventional linear step syntheses by the way of reducing
time, saving money, energy and raw-materials, thus
resulting in both economical and environmental benefits
[26].
Keywords One-pot Á [Bmim]BF4 Á 1,3-Cyclic diketone Á
Aryl glyoxals Á Imidazole-2-one
Introduction
The imidazole nucleus is present in large number of natural
products. Compounds with an imidazole ring system have
many pharmacological properties and play important roles
in biochemical processes [1–6]. Many of the substituted
imidazoles are known as of fungicides, herbicides, plant
growth regulators and therapeutic agents [7, 8]. Imidazole-
2-one derivatives exhibit antioxidant and cardiotonic
properties [9–20]. Recent advances in green chemistry and
organometallic chemistry have extended the boundary of
imidazoles to the synthesis and application of a large class
of imidazoles as ionic liquids as well as imidazole-related
N-heterocyclic carbenes [21, 22]. Therefore, the interest is
Recently, ionic liquids have emerged as very potential
green alternatives to the volatile and hazardous organic
solvents and have been used as efficient reaction media for
organic synthesis due to their special properties such as
good solvating capability, wide liquid range, negligible
vapour pressure, easy recycling, and high thermal stability
and rate enhancing ability [27–38]. In continuation of our
research work on the synthesis of heterocyclic compounds
using ionic liquids [39, 40], herein, we have reported an
efficient one-pot three-component synthesis of novel
imidazole-2-ones using 1,3-cyclic diketones, aryl glyoxals
and urea in the presence of ionic liquid [Bmim]BF4 at RT
in excellent yields with short reaction times (Scheme 1).
S. Kanakaraju Á G. V. P. Chandramouli (&)
Department of Chemistry, National Institute of Technology,
Warangal 506 004, Andhra Pradesh, India
e-mail: gvpc2000@gmail.com
Results and discussion
B. Prasanna Á P. Venkatanarayana
In order to find the optimum reaction conditions, a model
reaction of dimedone (1 mmol), 4-bromoglyoxal (1 mmol),
and urea (1 mmol) was performed in various solvents and
Research Centre, Department of Chemistry,
Chaitanya P.G. College (Autonomous),
Warangal 506 004, Andhra Pradesh, India
123

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J IRAN CHEM SOC (2012) 9:933–937
Scheme 1 Synthesis of
imidazole-2-ones using
[Bmim]BF4 ionic liquid
R1
O
O
C CHO
NH
O
OH
([Bmim]BF4)
RT, 5-15 min
O
H2N
NH2
N
+
+
H
R
O
R
R
O
R1
R
1
2
3
4a-l
ionic liquids at different temperatures. The efficiency and
the yield of the reaction in [Bmim]BF4 at RT were higher
than the reaction conducted in other solvents and ionic
liquids. The results are summarized in Table 1.
The IL could be reused up to five runs without evident loss
in activity (Table 1, entry 8). The results are summarized in
Table 2. All the synthesized compounds were character-
1
ized by elemental analysis, IR, H NMR, mass and 13C
Based on the optimum reaction conditions, one-pot
three-component condensation of various glyoxals, 1,3-
cyclic diketones and urea was then explored. As can be
seen from Table 2, the reactions were carried out effi-
ciently and the desired products were obtained in excellent
yield (92–96 %) and very short reaction time (5–15 min).
NMR techniques.
IR spectra of compound 4c exhibited absorptions at
3,423 cm-1 for OH, 3,250 cm-1 for NH, 3,059 cm-1 for
aromatic C–H stretching, 1,695 cm-1 for C=O, and
1,665 cm-1 for C=O, amide. The 1H NMR of compound 4c
showed singlet at d 11.05, 10.30 and 9.79 ppm for OH, and
two NH protons, respectively. Four aromatic protons were
observed as doublets at d 7.42 and 7.19 ppm, it also showed
multiplet at d 2.21–2.43 ppm for 2 9 CH2 and singlet at d
1.05 ppm for 2 9 CH3 of dimedone. The 13C NMR spec-
trum is in good agreement with the structure assigned. The
carbonyl carbon was observed at d 193.4 ppm and the
signal at d 185.3 ppm is assigned to carbon attached with
OH group. The signal at d 154.1 ppm is due to C=O of
amide. All aromatic carbons were observed at around d
124.2–131.0 ppm. The structure was further confirmed by
its mass spectral studies. It gave molecular ion peak at
m/z 378 (M ? 1) corresponding to molecular formula
C17H17BrN2O3. The elemental analysis values are in good
agreement with theoretical data. Similarly, all these com-
pounds were characterized on the basis of spectral studies.
Table 1 Solvent optimization for the synthesis of 4c
Entry Solvent
Temperature Time Yield
(oC)
(min) (%)a
1
2
3
4
5
6
7
8
a
CH3CN
EtOH
Reflux
Reflux
Reflux
480
420
450
360
120
100
150
5
Trace
32
n-Propanol
25
EtOH ? AcOH Reflux
62
[Bmim]Br
[Bmim]Cl
[Bmim]PF6
[Bmim]BF4
80
72
90
65
100
RT
60
95, 93, 91, 90, 89b
Yield of isolated product
b
[Bmim]BF4 was reused five times
Conclusion
Table 2 Synthesis of imidazol-2-one derivatives 4a–l
Entry
Compound
R
R1
Time (min)
Yield (%)a
In conclusion, we have demonstrated an efficient method
for the synthesis of substituted imidazol-2-ones by one-pot
three-component condensation of 1,3-cyclic diketones, aryl
glyoxals and urea using ([Bmim]BF4) ionic liquid. The
reactions are very fast (5–15 min) and high yielding; IL
was reused for five times.
1
4a
4b
4c
4d
4e
4f
Me
Me
Me
Me
Me
Me
H
H
5
6
96
93
95
94
92
93
95
93
94
92
93
92
2
Cl
3
Br
5
4
Me
OMe
NO2
H
8
5
10
15
7
6
7
4g
4h
4i
Experimental
8
H
Cl
9
9
H
Br
12
14
10
15
Melting points were recorded in open capillary and were
10
11
12
a
4j
H
Me
OMe
NO2
uncorrected. IR spectra (mmax) were recorded on a Bruker
WM-4(X) spectrometer (577 model) using KBr disks. H
4k
4l
H
1
NMR (300 MHz) and 13C NMR (75 MHz) spectra were
H
recorded on Bruker AC-300 spectrometer in DMSO-d6
Isolated yield
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J IRAN CHEM SOC (2012) 9:933–937
935
with TMS as an internal standard. Mass spectra (EI-MS)
were determined on Perkin Elmer (SCIEX API-2000, ESI)
at 12.5 eV. CHN analysis was done by Carlo Erba EA 1108
automatic elemental analyzer. All the solvents and chem-
icals used were pure, purchased from commercial sources
and were used without further purification unless otherwise
stated.
1.05 (s, 6H, 2 9 CH3), 2.21–2.43 (m, 4H, 2 9 CH2), 7.19
(d, J = 8.4 Hz, 2H, ArH), 7.42 (d, J = 8.4 Hz, 2H, ArH),
9.79 (s, 1H, NH), 10.30 (s, 1H, NH), 11.05 (s, 1H, OH)
ppm; 13C NMR (DMSO-d6, 75 MHz): d 193.4, 185.3,
154.1, 131.0, 130.3, 126.1, 124.2, 117.7, 111.7, 105.5,
51.8, 47.2, 31.4, 29.6, 27.9 ppm; MS: m/z = 378
(M? ? 1); Anal. Calcd for C17H17BrN2O3: C, 54.13; H,
4.54; N, 7.43. Found: C, 54.07; H, 4.57; N, 7.47 %.
Typical procedure
5-(2-Hydroxy-4,4-dimethyl-6-oxocyclohex-1-enyl)-4-
A mixture of cyclic 1,3-diketone (1 mmol), aryl glyoxal
(1 mmol) and urea (1 mmol) in [Bmim]BF4 ionic liquid
(5 mL) was stirred at RT for 5–15 min. The solid separated
was filtered and washed with water to leave the crude
product which was recrystallized from ethanol to afford
colorless solid in excellent yield (92–96 %). The IL was
recovered by evaporating the solvent under vacuum and it
was reused for five runs without evident loss of activity.
This procedure was followed for the synthesis of all the
compounds 4a–l.
(4-methylphenyl)-1H-imidazol-2-one (4d)
M.p.: 223–225 °C; IR (KBr, cm-1) m = 3,398, 3,253,
1
3,054, 1,702, 1,664; H NMR (DMSO-d6, 300 MHz): d
1.02 (s, 6H, 2 9 CH3), 2.20 (s, 3H, CH3), 2.28–2.40 (m,
4H, 2 9 CH2), 7.12 (d, J = 8.0 Hz, 2H, ArH), 7.37 (d,
J = 8.0 Hz, 2H, ArH), 9.69 (s, 1H, NH), 10.25 (s, 1H,
NH), 10.93 (s, 1H, OH) ppm; 13C NMR (DMSO-d6,
75 MHz): d 192.9, 185.0, 154.0, 136.7, 133.2, 127.3,
122.2, 117.3, 111.1, 105.4, 51.4, 47.0, 30.9, 29.2, 24.6,
27.5 ppm; MS: m/z = 313 (M? ? 1); Anal. Calcd for
C18H20N2O3: C, 69.21; H, 6.45; N, 8.97. Found: C, 69.27;
H, 6.36; N, 8.92.
5-(2-Hydroxy-4,4-dimethyl-6-oxocyclohex-1-enyl)-4-
phenyl-1H-imidazol-2)-one (4a)
M.p.: 235–237 °C; IR (KBr, cm-1) m = 3,391, 3,260,
3,058, 1,705, 1,666; H NMR (DMSO-d6, 300 MHz): d
5-(2-Hydroxy-4,4-dimethyl-6-oxocyclohex-1-enyl)-4-
1
(4-methoxyphenyl)-1H-imidazol-2-one (4e)
1.05 (s, 6H, 2 9 CH3), 2.26–2.42 (m, 4H, 2 9 CH2),
7.12–7.33 (m, 5H, ArH), 9.79 (s, 1H, NH), 10.27 (s, 1H,
NH), 11.01 (s, 1H, OH) ppm; 13C NMR (DMSO-d6,
75 MHz): d 193.2, 185.3, 154.1, 136.4, 130.2, 126.6, 122.1,
117.0, 111.0, 105.4, 51.6, 47.2, 31.1, 29.1, 27.9 ppm; MS:
m/z = 299 (M? ? 1); Anal. Calcd for C17H18N2O3: C,
68.44; H, 6.08; N, 9.39. Found: C, 68.50; H, 6.01; N, 9.45.
M.p.: 252–254 °C; IR (KBr, cm-1) m = 3,411, 3,254,
3,056, 1,710, 1,666; H NMR (DMSO-d6, 300 MHz): d
1
1.06 (s, 6H, 2 9 CH3), 2.26–2.43 (m, 4H, 2 9 CH2), 3.82
(s, 3H, OCH3), 7.08 (d, J = 8.2 Hz, 2H, ArH), 7.32 (d,
J = 8.2 Hz, 2H, ArH), 9.77 (s, 1H, NH), 10.28 (s, 1H,
NH), 10.95 (s, 1H, OH) ppm; 13C NMR (DMSO-d6,
75 MHz): d 193.0, 185.2, 154.2, 142.9, 134.4, 122.7,
120.2, 117.6, 111.5, 105.3, 56.3, 51.5, 47.1, 31.2, 29.5,
27.7 ppm; MS: m/z = 329 (M? ? 1); Anal. Calcd for
C18H20N2O4: C, 65.84; H, 6.14; N, 8.53. Found: C, 65.76;
H, 6.21; N, 8.49.
4-(4-Chlorophenyl)-5-(2-hydroxy-4,4-dimethyl-6-
oxocyclohex-1-enyl)-1H-imidazol-2-one (4b)
M.p.: 267–269 °C; IR (KBr, cm-1) m = 3,420, 3,155,
1
3,057, 1,694, 1,662; H NMR (DMSO-d6, 300 MHz): d
1.06 (s, 6H, 2 9 CH3), 2.20–2.42 (m, 4H, 2 9 CH2), 7.16
(d, J = 8.4 Hz, 2H, ArH), 7.40 (d, J = 8.4 Hz, 2H, ArH),
9.79 (s, 1H, NH), 10.28 (s, 1H, NH), 11.02 (s, 1H, OH)
ppm; 13C NMR (DMSO-d6, 75 MHz): d 193.2, 185.3,
154.0, 131.0, 130.1, 126.0, 124.2, 117.2, 111.3, 105.3,
51.6, 47.1, 31.1, 29.3, 27.7 ppm; MS: m/z = 333
(M? ? 1); Anal. Calcd for C17H17ClN2O3: C, 61.36; H,
5.15; N, 8.42. Found: C, 61.42; H, 5.11; N, 8.46.
5-(2-Hydroxy-4,4-dimethyl-6-oxocyclohex-1-enyl)-4-
(4-nitrophenyl)-1H-imidazol-2-one (4f)
M.p.: 292–294 °C; IR (KBr, cm-1) m = 3,407, 3,257,
1
3,056, 1,698, 1,662; H NMR (DMSO-d6, 300 MHz): d
1.04 (s, 6H, 2 9 CH3), 2.29–2.43 (m, 4H, 2 9 CH2), 7.52
(d, J = 8.7 Hz, 2H, ArH), 8.35 (d, J = 8.7 Hz, 2H, ArH),
9.75 (s, 1H, NH), 10.24 (s, 1H, NH), 10.97 (s, 1H, OH)
ppm; 13C NMR (DMSO-d6, 75 MHz): d 193.1, 185.2,
154.0, 143.2, 138.1, 126.5, 124.2, 117.4, 111.5, 105.2,
51.5, 47.1, 31.2, 29.6, 27.6 ppm; MS: m/z = 344
(M? ? 1); Anal. Calcd for C17H17N3O5: C, 59.47; H, 4.99;
N, 12.24. Found: C, 59.54; H, 5.04; N, 12.14.
4-(4-Bromophenyl)-5-(2-hydroxy-4,4-dimethyl-6-
oxocyclohex-1-enyl)-1H-imidazol-2-one (4c)
M.p.: 276–278 °C; IR (KBr, cm-1) m = 3,423, 3,250,
1
3,059, 1,695, 1,665; H NMR (DMSO-d6, 300 MHz): d
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J IRAN CHEM SOC (2012) 9:933–937
m/z = 285 (M? ? 1); Anal. Calcd for C16H16N2O3: C,
67.59; H, 5.67; N, 9.85. Found: C, 67.53; H, 5.50; N, 9.93.
5-(2-Hydroxy-6-oxocyclohex-1-enyl)-4-phenyl-1H-
imidazol-2-one (4g)
M.p.: 235–237 °C; IR (KBr, cm-1) m = 3,361, 3,245,
3,068, 1,701, 1,666; H NMR (DMSO-d6, 300 MHz): d
5-(2-Hydroxy-6-oxocyclohex-1-enyl)-4-(4-
1
methoxyphenyl)-1H-imidazol-2-one (4k)
1.91–1.95 (m, 2H, CH2), 2.26–2.31 (m, 2H, CH2),
2.61–2.64 (m, 2H, CH2), 7.20–7.53 (m, 5H, ArH), 9.75 (s,
1H, NH), 10.26 (s, 1H, NH), 10.97 (s, 1H, OH) ppm; 13C
NMR (DMSO-d6, 75 MHz): d 193.0, 185.6, 154.5, 136.7,
130.2, 126.8, 123.1, 117.9, 111.0, 105.7, 36.6, 27.3,
20.4 ppm; MS: m/z = 271 (M? ? 1); Anal. Calcd for
C15H14N2O3: C, 66.66; H, 5.22; N, 10.36. Found: C, 67.60;
H, 5.19; N, 10.29.
M.p.: 252–254 °C; IR (KBr, cm-1) m = 3,374, 3,276,
3,063, 1,714, 1,666; H NMR (DMSO-d6, 300 MHz): d
1
1.94–1.96 (m, 2H, CH2), 2.24–2.31 (m, 2H, CH2),
2.63–2.67 (m, 2H, CH2), 7.18 (d, J = 8.1 Hz, 2H, ArH),
7.81 (d, J = 8.1 Hz, 2H, ArH), 9.77 (s, 1H, NH), 10.31 (s,
1H, NH), 10.99 (s, 1H, OH) ppm; 13C NMR (DMSO-d6,
75 MHz): d 193.3, 185.5, 154.3, 143.4, 134.7, 122.5,
120.6, 118.4, 111.2, 105.6, 56.3, 37.1, 27.6, 20.8 ppm; MS:
m/z = 301 (M? ? 1); Anal. Calcd for C16H16N2O4: C,
63.99; H, 5.37; N, 9.33. Found: C, 63.86; H, 5.21; N, 9.44.
4-(4-Chlorophenyl)-5-(2-hydroxy-6-oxocyclohex-1-
enyl)-1H-imidazol-2-one (4h)
M.p.: 267–269 °C; IR (KBr, cm-1) m = 3,378, 3,245,
3,057, 1,699, 1,662; H NMR (DMSO-d6, 300 MHz): d
5-(2-Hydroxy-6-oxocyclohex-1-enyl)-4-(4-
1
nitrophenyl)-1H-imidazol-2-one (4l)
1.90–1.93 (m, 2H, CH2), 2.22–2.30 (m, 2H, CH2),
2.60–2.63 (m, 2H, CH2), 7.16 (d, J = 8.2 Hz, 2H, ArH),
7.70 (d, J = 8.2 Hz, 2H, ArH), 9.80 (s, 1H, NH), 10.38 (s,
1H, NH), 10.95 (s, 1H, OH) ppm; 13C NMR (DMSO-d6,
75 MHz): d 193.5, 185.4, 154.6, 131.3, 130.7, 126.2,
124.5, 118.1, 109.5, 106.2, 36.1, 27.1, 20.2 ppm; MS: m/
z = 305 (M? ? 1); Anal. Calcd for C15H13ClN2O3: C,
59.12; H, 4.30; N, 9.19. Found: C, 59.21; H, 4.37; N, 9.06.
M.p.: 292–294 °C; IR (KBr, cm-1) m = 3,380, 3,267,
3,056, 1,697, 1,662; H NMR (DMSO-d6, 300 MHz): d
1
1.90–1.93 (m, 2H, CH2), 2.21–2.33 (m, 2H, CH2),
2.63–2.66 (m, 2H, CH2), 7.17 (d, J = 8.6 Hz, 2H, ArH),
7.77 (d, J = 8.6 Hz, 2H, ArH), 9.77 (s, 1H, NH), 10.28 (s,
1H, NH), 10.96 (s, 1H, OH) ppm; 13C NMR (DMSO-d6,
75 MHz): d 193.4, 185.4, 154.7, 143.6, 138.8, 127.2,
124.5, 118.2, 111.0, 106.1, 37.2, 27.4, 20.6 ppm; MS: m/
z = 316 (M? ? 1); Anal. Calcd for C15H13N3O5: C, 57.14;
H, 4.16; N, 13.33. Found: C, 57.20; H, 4.21; N, 13.28.
4-(4-Bromophenyl)-5-(2-hydroxy-6-oxocyclohex-1-
enyl)-1H-imidazol-2-one (4i)
M.p.: 276–278 °C; IR (KBr, cm-1) m = 3,384, 3,265,
3,056, 1,712, 1,674; H NMR (d, DMSO-d6): d 1.92–1.96
Acknowledgments The authors are thankful to the Director,
National Institute of Technology, Warangal for providing research
facilities and financial support.
1
(m, 2H, CH2), 2.25–2.32 (m, 2H, CH2), 2.62–2.66 (m, 2H,
CH2), 7.14 (d, J = 8.2 Hz, 2H, ArH), 7.72 (d, J = 8.2 Hz,
2H, ArH), 9.83 (s, 1H, NH), 10.44 (s, 1H, NH), 11.12 (s,
1H, OH) ppm; 13C NMR (DMSO-d6, 75 MHz): d 193.8,
185.5, 154.4, 131.7, 130.5, 126.3, 124.7, 118.5, 109.9,
105.5, 36.7, 27.4, 20.5 ppm; MS: m/z = 350 (M? ? 1);
Anal. Calcd for C15H13BrN2O3: C, 51.60; H, 3.75; N, 8.02.
Found: C, 51.72; H, 3.83; N, 7.95.
References
1. J. Heers, L.J.J. Backx, J.H. Mostmans, J. Van Cutsem, J. Med.
Chem. 22, 1003 (1979)
2. W. Hunkeler, H. Mohler, L. Pieri, P. Polc, E.P. Bonetti, R.
Cumin, R. Schaffner, W. Haefely, Nature 290, 514 (1981)
3. R.W. Brimblecombe, W.A.M. Duncan, G.J. Durant, J.C. Emmett,
C.R. Ganellin, M.E.J. Parons, Int. Med. Res. 3, 86 (1975)
4. Y. Tanigawara, N. Aoyama, T. Kita, K. Shirakawa, F. Komada,
M. Kasuga, K. Okumura, Clin. Pharmacol. Ther. 66, 528 (1999)
5. A. Wauquier, W.A.E. Van Den Broeck, J.L. Verheyen, P.A.J.
Janssen, Eur. J. Pharmacol. 47, 367 (1978)
6. J.G. Lambardino, E.H. Wiseman, J. Med. Chem. 17, 1182 (1974)
7. T. Maier, R. Schmierer, K. Bauer, H. Bieringer, H. Buerstell, B.
Sachse (1989) US Patent 820335
8. T. Maier, R. Schmierer, K. Bauer, H. Bieringer, H. Buerstell, B.
Sachse, Chem Abstr 111, 19494 (1989)
5-(2-Hydroxy-6-oxocyclohex-1-enyl)-4-(4-
methylphenyl)-1H-imidazol-2-one (4j)
M.p.: 223–225 °C; IR (KBr, cm-1) m = 3,371, 3,243,
1
3,061, 1,698, 1,664; H NMR (DMSO-d6, 300 MHz): d
1.87–1.91 (m, 2H, CH2), 2.18–2.23 (m, 2H, CH2),
2.59–2.62 (m, 2H, CH2), 7.11 (d, J = 7.9 Hz, 2H, ArH),
7.67 (d, J = 7.9 Hz, 2H, ArH), 9.66 (s, 1H, NH), 10.22 (s,
1H, NH), 10.91 (s, 1H, OH) ppm; 13C NMR (DMSO-d6,
75 MHz): d 193.2, 185.1, 154.5, 136.9, 133.6, 127.8,
122.7, 117.6, 109.0, 106.3, 36.1, 27.4, 26.5, 19.7 ppm; MS:
9. R.C. Smith, J.C. Reeves, R.C. Dage, R.A. Schnettler, Biochem
Pharmacol 36, 1457 (1987)
10. R.C. Smith, J.C. Reeves, R.C. Dage, R.A. Schnettler, Chem Abstr
107, 70771d (1987)
123

J IRAN CHEM SOC (2012) 9:933–937
937
11. R.C. Smith, J.H. Hargis, Microchem J 31, 18 (1985)
12. R.C. Smith, J.H. Hargis, Chem Abstr 103, 53851c (1985)
13. M. Weiss, E.M. Schneider, S. Libert, S. Mettier, H. Lemoine,
Immunopharmacol Immunotoxicol 19, 239 (1997)
14. M. Weiss, E.M. Schneider, S. Libert, S. Mettier, H. Lemoine,
Chem. Abstr. 127, 788d (1997)
15. M. Buerke, T. Cyrus, H. Darius, Thromb. Res. 88, 89 (1997)
16. M. Buerke, T. Cyrus, H. Darius, Chem. Abstr. 127, 303133c
(1997)
17. S.F. Katircioglu, Z. Satrias, A.T. Ulus, B. Yamak, Jpn. Circ. J. 62,
122 (1998)
18. S.F. Katircioglu, Z. Satrias, A.T. Ulus, B. Yamak, Chem. Abstr.
128, 289973p (1998)
25. T. Hudlicky, Chem. Rev. 96, 3 (1996)
´
26. J. Zhu, H. Bienayme (eds.), Multicomponent reactions (Wiley,
Weinheim, 2005)
27. P. Wasserscheid, T. Welton, Ionic liquids in synthesis (Wiley,
Weinheim, 2003)
28. R. Sheldon (2001) Chem Commun 2399
29. C.M. Gordon (2001) Appl Catal A 101
30. P. Wasserscheid, W. Keim, Angew. Chem. Int. Ed. 39, 3772
(2000)
31. J.S. Wilkes, Green Chem. 4, 73 (2002)
32. N. Jain, A. Kumar, S. Chauhan, S.M.S. Chauhan, Tetrahedron 61,
1015 (2005)
33. M.J. Earle, S.P. Katdare, K.R. Seddon, Org. Lett. 6, 707 (2004)
34. M.J. Earle, K.R. Seddon, Pure Appl. Chem. 72, 1391 (2000)
35. Q. Yao, Org. Lett. 4, 2197 (2002)
19. R.C. Dage, F.P. Palopoli, R.A. Schnettler (1984) US Patent
4405628
20. R.C. Dage, F.P. Palopoli, R.A. Schnettler, Chem. Abstr. 100,
6516c (1984)
21. T. Welton, Chem. Rev. 99, 2071 (1999)
22. W.A. Hermann, C. Kocher, Angew. Chem. Int. Ed. 36, 2162
(1997)
36. D. Zhao, M. Wu, Y. Kou, E. Min (2002) Catal Today 157
37. H.M. Zerth, N.M. Leonard, R.S. Mohan, Org. Lett. 5, 55 (2003)
38. A. Kumar, S.S. Pawar, J. Org. Chem. 69, 1419 (2004)
39. M. Maradolla, S.K. Allam, A. Mandha, G.V.P. Chandramouli,
Arkivoc 15, 42 (2008)
23. Z. Hassani, M.R. Islami, M. Kalantari, Bio. Med. Chem. Lett. 16,
4479 (2006)
40. M. Maradolla, G.V.P. Chandramouli, Phosphorus Sulfur Silicon
Relat. Elem. 186, 1650 (2011)
24. P.A. Wender, S.L. Handy, D.L. Wright (1997) Chem Ind (Lon-
don) 765
123