Nano indium oxide catalyzed tandem cyclization of amidine with nitroolefin

Article abstract of DOI:10.1016/j.tetlet.2013.07.050

A tandem cyclization of amidine with nitroolefin has been described using nano In₂O₃ as an efficient catalyst. The reaction is effective for the preparation of 4,5-unsymmetrically substituted 1-H imidazole in moderate to good yields. The catalyst was successfully reused for four consecutive cycles with similar catalytic activities.

Full text of DOI:10.1016/j.tetlet.2013.07.050

Tetrahedron Letters 54 (2013) 4982–4985
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Nano indium oxide catalyzed tandem cyclization of amidine
with nitroolefin
⇑
⇑
Shubhanjan Mitra, Avik Kumar Bagdi, Adinath Majee , Alakananda Hajra
Department of Chemistry, Visva-Bharati (A Central University), Santiniketan 731235, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 March 2013
Revised 3 July 2013
Accepted 6 July 2013
Available online 16 July 2013
A tandem cyclization of amidine with nitroolefin has been described using nano In2O3 as an efficient cat-
alyst. The reaction is effective for the preparation of 4,5-unsymmetrically substituted 1-H imidazole in
moderate to good yields. The catalyst was successfully reused for four consecutive cycles with similar
catalytic activities.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Nano indium oxide
Imidazole
Nitroolefin
Amidine
Cyclization
Recently metal nano catalysts have received considerable
importance in organic synthesis due to their better catalytic prop-
erties and selectivity compared to their bulk counterparts.1 In the
context of green chemistry they have earned more significance
due to their effective reusability as well as greater efficiency be-
cause of their higher surface area.2 Indium metal and its salts have
attracted attention of the synthetic community due to their wide
applications in the field of organic synthesis.3 Our group has been
actively engaged in utilizing indium metal and its salts for useful
reactions for more than a decade.4 It is significant to note that
the application of nano In2O3 as catalyst has not been well stud-
ied.5a,b Our recently reported work5c,d with nano In2O3 inspired
us to explore its catalytic activity for useful transformations and
preparation of important organic compounds.
Our previous work : Coupling between nitroolefin and phenol/napthols7
H
R2
R1
NO2
OH
O
R1
In(OTf)3 (5 mol %)
DCE, reflux
Ar
+
Ar
R2
Present work : Tandem cyclization between amidine and nitroolefin
R2
NH
NH2. HCl
H
nano In2O3 (5 mol %)
K2CO3 (1 equiv.)
HN
NO2
R2
R1
R3
R3
+
R1
N
EtOH, 70 oC
6 hr.
Scheme 1.
Nitroolefins are easily prepared6a and considered as a useful
substrate in many synthetic strategies like Michael addition,6b
cycloaddition,6c–e Morita–Baylis–Hillman reaction,6f and two com-
ponent coupling reaction.7 Previous work by our group7 on the
synthesis of arenofurans has demonstrated an important use to
nitroolefins (Scheme 1). It has been established that N-arylami-
dines serve as precursors to the synthesis of biologically important
heterocycles.8 We have used nitroolefins as starting material for
the synthesis of 4,5-unsymmetrically substituted 1-H imidazoles
(Scheme 1). Attempts made for the synthesis of imidazoles stem
from the broad range of their applications in biological9 as well
as synthetic fields.10 The traditional methods for the preparation
of both 2,4,5-substituted and 1,2,4,5-substituted imidazoles are
based on the multicomponent reaction using 1,2-dicarbonyl com-
pounds, different aldehydes, and a nitrogen source.11 There are a
number of methods in the literature following this strategy11 with
variation of parameters and catalysts.12 Most of these traditional
methods involved the synthesis of symmetrically substituted imid-
azole at 4,5-position. This is due to the lesser availability of unsym-
metric 1,2-diketones. Accordingly, a methodology for the synthesis
of 4,5-unsymmetrically substituted imidazoles using a simple two-
component one-pot reaction is highly desirable. Herein, we report
a method for the synthesis of 4,5-unsymmetrically substituted 1-H
imidazoles using nano In2O3 as catalyst, K2CO3 as base, and ethanol
as solvent (Scheme 1).
Being encouraged by our previous results,7 we initiated our
study taking amidine hydrochloride, nitroolefin, and In(OTf)3 as
⇑
Corresponding authors.
E-mail address: adinath.majee@visva-bharati.ac.in (A. Majee).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.07.050

S. Mitra et al. / Tetrahedron Letters 54 (2013) 4982–4985
4983
Table 1
Table 2
Optimization of the reaction conditions
Scope of substrates
R2
CH3
H
NO2
R2
NH
NH2. HCl
NH
nano In2O3 (5 mol %)
HN
R3
H
NO2
CH3
Catalyst (5 mol %)
Base (1 equiv.)
HN
+
R1
R3
R1
N
Ph
K2CO3 ( 1 equiv.)
EtOH, 70 oC 6 hr.
+
Ph
NH2. HCl
N
Ph
Ph
3
2
1
6 hr.
Solvent
CH3
CH3
CH3
HN
HN
HN
HN
Entry
Catalyst
Base
Solvent
Temp (°C)
Yielda (%)
OCH3
Cl
N
N
N
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25b
26
27c
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
In(OTf)3
InCl3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Cs2CO3
KOH
EtOH
DCB
1,2-DCE
CH3CN
DMSO
DMF
PEG400
Toluene
H2O
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
70
Reflux
70
86
40
80
62
43
40
51
72
56
59
71
72
52
58
78
—
81
70
88
74
70
<5
58
53
90
89
78
3b, 80 %
3a, 88 %
3c, 70 %
CH3
CH3
CH3
HN
HN
CH3
Br
N
N
N
3e, 72 %
3f, 65 %
3d, 80 %
CH3
CH3
O
HN
HN
HN
HN
O
N
N
N
O
3i, 70 %
3g, 81 %
3h,79 %
KOAc
DABCO
Et3N
CH3
CH3
CH3
HN
HN
—
OCH3
N
N
N
H3
C
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Powder In2O3
Nano In2O3
Nano ZnO
3l, 55 %
3k, 82 %
NO2
NO2
3j, 85 %
Nano CuO
EtOH
Nano In2O3
Nano In2O3
Nano In2O3
Nano In2O3
Nano In2O3
Nano In2O3
1,2-DCE
CH3CN
PEG 400
EtOH
EtOH
EtOH
a
b
c
Isolated yield.
10 mol % catalyst used.
3 mol % catalyst used.
catalysts using 1,2-DCE as solvent and K2CO3 as base (Table 1, en-
try 3) and were able to synthesize the desired imidazole in 80%
yield. Other solvents like DCB, CH3CN, DMSO, DMF, dioxane, PEG-
400, toluene, and H2O (entries 2–10) gave lower yields. However,
EtOH (Table 1, entry 1) was found as the best solvent increasing
the product yield to a good extent (86%). We varied the bases like
Cs2CO3, KOH, and KOAc (Table 1, entries 11–13) instead of K2CO3
but no enhancement of yield was observed. Application of organic
bases like DABCO and Et3N (Table 1, entries 14 and 15) furnished
58% and 78% yields, respectively. The reaction did not proceed at
all, in the absence of base (Table 1, entry 16). Therefore, the choice
of base has important role in the reaction path and is probably re-
quired to free the amidine hydrochloride. Indium chloride was also
able to perform the reaction with good yields (81%, Table 1, entry
17). Motivated by this result, we then used powder In2O3 (Table
1, entry 18) and nano In2O3 (Table 1, entry 19) and obtained very
good yields, 70% and 88%, respectively. To investigate the effect
on the choice of catalyst, we have used different nano metal oxides
like ZnO and CuO, (Table 1, entries 20 and 21), but no enhancement
of yield has been observed. Thus we have found that nano In2O3 is
an effective catalyst under the reaction conditions. Further, the
efficiency of different solvents for nano In2O3-catalyzed reaction
(Table 1, entries 22–24) has been examined and no promising re-
sult was found. Next, with EtOH as the solvent we tested the cata-
lyst loading and observed that no considerable improvement was
made on increasing the amount of catalyst or increasing the tem-
perature from 70 °C to reflux (Table 1, entries 25 and 26). On low-
ering the amount of catalyst (3 mol %) yield of the reaction was
reduced (Table 1, entry 27). The detailed optimization is summa-
rized in Table 1.
Figure 1. Reusability of the catalyst.
The substrate scope and limitations of our method were inves-
tigated and are summarized in Table 2. The reaction of (2-nitro-
propenyl)-benzene with benzamidine was very clean giving 88%
yield (3a). We have performed the reactions varying the amidines
with a wide range of structurally diverse nitroolefins and isolated
the desired products in good yields. As it is evident from Table 2,
this procedure is uniformly effective for nitroolefins with different
substituents on the benzene ring as well as for aliphatic nitroolefin
(3f). Nitroolefins with a methylenedioxy group on the aromatic
moiety underwent smooth reaction with 81% yield (3g). The het-
erocyclic moiety (3h) remains unaffected under the present reac-
tion conditions and furnished good yield (79%). However, using
acetamidine (31) over benzamidine resulted in a lower yield
(55%). The reaction did not proceed for (2-nitro-vinyl)-benzene
with acetamidine or benzamidine under the present reaction
conditions.
To check the reusability of the catalyst, the catalyst after each
run, the latter was centrifuged and washed with ethanol and water
followed by drying at 110 °C. The recovered catalyst was reused for
four subsequent runs without any significant deactivation of the
catalytic activity (Fig. 1).

4984
S. Mitra et al. / Tetrahedron Letters 54 (2013) 4982–4985
6. (a) Maity, S.; Manna, S.; Rana, S.; Naveen, T.; Mallick, A.; Maiti, D. J. Am. Chem.
In III
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Soc. 2013, 135, 3355; (b) Tripathi, C. B.; Kayal, S.; Mukherjee, S. Org. Lett. 2012,
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2010, 132, 5338; (f) Basavaiah, D.; Reddy, B. S.; Badsara, S. S. Chem. Rev. 2010,
110, 5447.
O
N
H
NO2
R2
NH
R2
nano In2O3
K2CO3
NH
H
+
R1
NH2 . HCl
R3
R3
R1
NH2
7. Kundu, D.; Samim, M.; Majee, A.; Hajra, A. Chem.-Asian J. 2011, 6, 406.
8. (a) Wang, Y.-F.; Zhu, X.; Chiba, S. J. Am. Chem. Soc. 2012, 134, 3679; (b) Wang,
Y.; Wang, H.; Peng, J.; Zhu, Q. Org. Lett. 2011, 13, 4604; (c) Ma, B.; Wang, Y.;
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Rees, C. W., Eds.; Pergamon Press: London, 1984; Vol. 5, p 374; (b) Misono, M.
Chem. Commun. 2001, 1141; (c) Blank, J. W.; Durant, G. J.; Emmett, J. C.;
Ganellin, C. R. Nature 1974, 248, 65; (d) Murry, J. A. Curr. Opin. Drug Discovery
Dev. 2003, 6, 945; (e) Laufer, S. A.; Zimmermann, W.; Ruff, K. J. J. Med. Chem.
2004, 47, 6311.
HO
O
OH
R2
N
R2
N
- HNO
- H2O
HO
HN
R2
HN
NH
R3
R3
R3
R1
N
H
R1
R1
N
N
H
H
10. (a) Chowdhury, S.; Mohan, R. S.; Scott, J. L. Tetrahedron 2007, 63, 2363; (b)
Bourissou, D.; Guerret, O.; Gabbai, F. P.; Bertrand, G. Chem. Rev. 2000, 100, 39;
(c) Arnold, P. L.; Liddle, S. T. Chem. Commun. 2006, 3959; (d) Kuhl, O. Chem. Soc.
Rev. 2007, 36, 592.
B
A
Scheme 2. Plausible mechanism for the synthesis of 2,4,5-trisubstituted imidazole.
11. (a) Debus, H. Ann. Chem. Pharm. 1858, 107, 199; (b) Radziszewski, B. Chem. Ber.
1882, 15, 1493.
12. For recent review see: (a) Chawla, A.; Sharma, A.; Sharma, A. K. Der Pharm.
Chem. 2012, 4, 116; (b) Rahman, M.; Bagdi, A. K.; Kundu, D.; Majee, A.; Hajra, A.
J. Heterocycl. Chem. 2012, 49, 1224; (c) Ramesh, K.; Murthy, S. N.; Karnakar, K.;
Nageswar, Y. V. D.; Vijayalakhshmi, K.; Prabhavathi Devi, B. L. A.; Prasad, R. B.
N. Tetrahedron Lett. 2012, 53, 1126; (d) Niknam, K.; Deris, A.; Naeimi, F.;
Majleci, F. Tetrahedron. Lett. 2011, 52, 4642; (e) Hasaninejad, A.; Zare, A.;
Shekouhy, M.; Rad, J. A. J. Comb. Chem. 2010, 12, 844; (f) Murthy, N. S.; Madhav,
B.; Nageswar, Y. V. D. Tetrahedron. Lett. 2010, 51, 5252; (g) Mukhopadhyay, C.;
Tapaswi, P. K.; Drew, M. G. B. Tetrahedron Lett. 2010, 51, 3944; (h) Zhang, P.-F.;
Chen, Z. C. Z. Synthesis 2001, 2075.
13. (a) Anwar, S.; Huang, W.-Y.; Chen, C.-H.; Cheng, Y.-S.; Chen, K. Chem. Eur. J.
2013. http://dx.doi.org/10.1002/chem.201204221; (b) Nair, D. K.; Mobin, S. M.;
Namboothiri, I. N. N. Org. Lett. 2012, 14, 4580; (c) Shiraishi, H.; Nishitani, T.;
Sakaguchi, S.; Ishii, Y. J. Org. Chem. 1998, 63, 6234; (d) Ranu, B. C.; Hajra, A.
Tetrahedron 2001, 57, 4767.
14. During preparation of our manuscript for submission a very closely related
work has been published. But analysis of their method proved that our
mechanistic path is totally different. Ref. Tang, D.; Wu, P.; Liu, X.; Chen,; Y.-X.;
Guo, S.-B.; Chen, W.-L.; Li, J.-G.; Chen, B.-H. J. Org. Chem. 2013, 78, 2746.
Typical procedure for the synthesis of 5-Methyl-2,4-diphenyl-1H-imidazole
(Table 2, 3a): In an oven dried 10 mL round bottom flask, benzamidine
hydrochloride (78 mg, 0.5 mmol), (2-nitro-propenyl)-benzene (81 mg,
0.5 mmol), nano In2O3 (7 mg, 5 mol %), K2CO3 (69 mg, 1 equiv), and dry EtOH
(2 mL) were added and stirred for 6 h at 70 °C. The progress of the reaction was
monitored by TLC. After completion of the reaction the excess EtOH was
evaporated in a rotary evaporator and the crude reaction mixture was diluted
with water (3 mL), and extracted with DCM. The organic layer was dried over
anhydrous Na2SO4 and evaporated under vacuum. The residue was purified by
column chromatography (hexane/ethyl acetate as eluent) to afford the
analytically pure product as a white solid (103 mg, 88%). mp 180–184 °C. IR
(KBr) 3357, 3076, 2692, 2584, 1872, 1735, 1598, 1492, 1456, 1406, 1278, 1126,
975 cmÀ1; d 1H NMR (400 MHz, DMSO-d6): d 8.15 (d, J = 7.2 Hz, 2H), 7.72 (d,
J = 7.2 Hz, 2H), 7.54–7.45 (m, 5H), 7.34 (t, J = 7.6 Hz, 1H), 2.47 (s, 3H); 13C NMR
(DMSO-d6, 100 MHz): d 143.4, 132.1, 131.5, 129.9, 129.3, 129.0, 127.6, 127.3,
127.0, 126.1, 11.5; Anal. Calcd for C16H4N2: C, 82.02; H, 6.02; N, 11.96%. Found:
C, 82.17; H, 6.10; N, 12.02%.
Based on our previous results,7 a likely mechanistic pathway for
the reaction is described in Scheme 2. Michael addition of ami-
dine–nitroolefin forms the Michael adduct A. It is possible that
the indium (III) catalyst promotes this addition by activating the
double bond. Then the intermediate A undergoes cyclization to
give the five membered cyclic intermediate B. Removal of HNO
and H2O from the latter leads to aromatization providing the de-
sired product.7,13,14
In conclusion, we have explored the use of nano In2O3 as an
effective and versatile catalyst for the synthesis of 4,5-unsymmet-
rically substituted 1-H imidazoles. The use of an environmentally
friendly and inexpensive base and solvent, along with reusability
of the catalyst provides a good example of a competitive, alterna-
tive synthetic methodology for these compounds.
Acknowledgments
A.H. and A.M. acknowledge the financial support from DST,
Govt. of India (Grant No. SR/S5/GC-05/2010). We are thankful to
DST–FIST and UGC–SAP. S.M. and A.K.B. thank DST and CSIR for
their fellowships. We thank Professor B. C. Ranu for editing the
manuscript. We also thank the reviewer for useful suggestions.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.
07.050.
4-(4-Methoxy-phenyl)-5-methyl-2-phenyl-1H-imidazole (3b). White solid (80%
yield): mp 176–178 °C; IR (KBr) 3431, 3045, 2912, 2769, 2644, 1641, 1606,
1253, 1186, 1012, 840, 821, 700 cmÀ1 1H NMR (400 MHz, DMSO-d6) d 8.14 (d,
;
J = 7.2 Hz, 2H), 7.64 (d, J = 8.4 Hz, 2H), 7.58–7.50 (m, 3H), 7.07 (d, J = 8.8 Hz,
2H), 3.81 (s, 3H), 2.44 (s, 3H); 13C NMR (100 MHz, DMSO-d6) d 159.3, 142.7,
131.0, 130.5, 129.4, 129.0, 126.4, 126.0, 122.7, 114.5, 55.6, 11.1; Anal. Calcd for
References and notes
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Polshettiwar, V.; Baruwati, B.; Varma, R. S. Green Chem. 2009, 11, 127; (c) Adak,
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Tian, Y.; Yue, Y.; Guo, Y.; Wang, Z. J. Org. Chem. 2011, 76, 4741.
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113, 271; (b) Yadav, J. S.; Antony, A.; George, J.; Reddy, B. V. S. Eur. J. Org. Chem.
2010, 591; (c) Ranu, B. C. Eur. J. Org. Chem. 2000, 2347; (d) Li, C. J. Tetrahedron
1999, 55, 11149; (e) Cintas, P. Synlett 1995, 1087.
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Majee, A.; Hajra, A. Tetrahedron Lett. 2009, 50, 2668; (c) Ranu, B. C.; Hajra, A.;
Jana, U. J. Org. Chem. 2000, 65, 6270; (d) Ranu, B. C.; Samanta, S.; Hajra, A.
Synlett 2002, 987; (e) Ranu, B. C.; Majee, A. Chem. Commun. 1997, 1225.
5. (a) Bahari, S.; Mehdi, A. S. J. Chem. Sci. 2013, 125, 153; (b) Reddy, V. P.; Kumar, A.
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C17H16N2O: C, 77.25; H, 6.10; N, 10.60%. Found: C, 77.28; H, 6.14; N, 10.62%.
4-(4-Chloro-phenyl)-5-methyl-2-phenyl-1H-imidazole (3c). Pale yellow solid
(70% yield): mp 164–166 °C; IR (KBr) 3276, 3240, 3045, 2964, 2852, 1909,
1596, 1517, 1494, 1361, 1255, 1164, 1091, 1014, 833, 682 cmÀ1 1H NMR
;
(400 MHz, DMSO-d6) d 7.98 (d, J = 7.2 Hz, 2H), 7.72 (d, J = 8.4 Hz, 2H), 7.47–7.43
(m, 4H), 7.34 (t, J = 7.6 Hz, 1H), 2.44 (s, 3H); 13C NMR (100 MHz, DMSO-d6) d
144.3, 133.8, 130.7, 130.6, 129.3, 129.1, 128.7, 128.3, 128.0, 125.1, 12.2; Anal.
Calcd for C16H13N2Cl: C, 71.51; H, 4.88; N, 10.42%. Found: C, 71.62; H, 4.96; N,
10.53%.
5-Methyl-2-phenyl-4-p-tolyl-1H-imidazole (3d). White solid (80% yield): mp
179 °C; IR (KBr) 3353, 3043, 2966, 2927, 2852, 1676, 1598, 1517, 1369, 1172,
1116, 1029, 767, 700, 659 cmÀ1 1H NMR (400 MHz, CDCl3) d 7.79 (d, J = 6.8 Hz,
;
2H), 7.23 (d, J = 6.8 Hz, 2H), 7.17–7.16 (m, 3H), 7.00 (d, J = 6.8 Hz, 2H), 2.19 (s,
3H), 2.12 (s, 3H); 13C NMR (100 MHz, CDCl3) d 143.7, 137.1, 131.3, 129.2, 129.1,
128.6, 127.5, 127.1, 126.9, 125.9, 21.1, 11.0; Anal. Calcd for C17H16N2: C, 82.22;
H, 6.49; N, 11.28%. Found: C, 82.30; H, 6.68; N, 11.37%.
4-(4-Bromo-phenyl)-5-methyl-2-phenyl-1H-imidazole (3e). White solid (72%
yield): mp 168–169 °C; IR (KBr) 3429, 3153, 3043, 2912, 2759, 2634, 2439,
2318, 1907, 1641, 1477, 1936, 1317, 1072, 823, 688 cmÀ1 1H NMR (400 MHz,
;

S. Mitra et al. / Tetrahedron Letters 54 (2013) 4982–4985
4985
DMSO-d6) d 7.98 (d, J = 8.4 Hz, 2H), 7.67 (d, J = 8.8 Hz, 2H), 7.59 (d, J = 8.8 Hz,
2H), 7.45 (t, J = 7.6 Hz, 2H), 7.34 (t, J = 7.6 Hz, 1H), 2.45 (s, 3H); 13C NMR
(100 MHz, DMSO-d6) d 172.4, 144.3, 131.6, 130.7, 129.1, 128.6, 128.4, 128.3,
127.9, 125.1, 119.0, 12.2; Anal. Calcd for C16H13BrN2: C, 61.36; H, 4.18; N,
8.94%. Found: C, 61.46; H, 4.26; N, 9.06%.
189 °C; IR (KBr) 3373, 3076, 2964, 2738, 2694, 2549, 1595, 1490, 1454, 1398,
1122, 939, 698 cmÀ1 1H NMR (400 MHz, DMSO-d6) d 7.77 (d, J = 7.2 Hz, 2H),
;
7.41 (d, J = 7.2 Hz, 2H), 7.23–7.16 (m, 4H), 7.09 (t, J = 7.2 Hz, 1H), 2.57 (q,
J = 7.6 Hz, 2H), 1.03 (t, J = 7.6 Hz, 3H); 13C NMR (100 MHz, DMSO-d6) d 163.9,
144.4, 135.1, 131.0, 129.1, 129.0, 128.8, 128.2, 126.8, 126.4, 125.2, 14.7, 11.0;
Anal. Calcd for C17H16N2: C, 82.22; H, 6.49; N, 11.28%. Found: C, 82.34; H, 6.58;
N, 11.39%.
4-Isopropyl-5-methyl-2-phenyl-1H-imidazole (3f). White solid (65% yield): mp
180–182 °C; IR (KBr) 3195, 3076, 3041, 2966, 2810, 2694, 2626, 2551, 1865,
1598, 1492, 1456, 1404, 1375, 1276, 1126, 1070, 975, 921, 702 cmÀ1
;
1H NMR
5-Methyl-2-(3-nitro-phenyl)-4-phenyl-1H-imidazole (3j). Yellow solid (85%
yield): mp 210–213 °C; IR (KBr) 3512, 3082, 3047, 2854, 2347, 1731, 1591,
(400 MHz, CDCl3) d 8.50 (s, 1H), 7.78 (d, J = 8.4 Hz, 2H), 7.18–7.12 (m, 3H),
2.96–2.85 (m, 1H), 2.08 (s, 3H), 1.12 (d, J = 7.2 Hz, 6H); 13C NMR (100 MHz,
CDCl3) d 143.5, 136.4, 131.0, 128.3, 127.1, 125.2, 25.3, 22.3, 10.9; Anal. Calcd for
1525, 1438, 1348, 1265, 1091, 923, 889, 730, 690 cmÀ1 1H NMR (400 MHz,
;
DMSO-d6) d 8.81 (s, 1H), 8.40 (d, J = 7.2 Hz, 1H), 8.14 (d, J = 7.26 Hz, 1H), 7.74–
7.69 (m, 3H), 7.43 (t, J = 7.2 Hz, 2H), 7.27 (t, J = 6.8 Hz, 1H), 2.45 (s, 3H); 13C
NMR (100 MHz, DMSO-d6) d 148.7, 141.9, 135.5, 134.1, 132.2, 131.0, 130.7,
128.8, 126.6, 123.8, 122.5, 119.3, 12.4; Anal. Calcd for C16H13N3O2: C, 68.81; H,
4.69; N, 15.05%. Found: C, 68.84; H, 4.76, N, 15.08%.
C
13H16N2: C, 77.96; H, 8.05; N, 13.99%. Found: C, 78.10; H, 8.16; N, 14.14%.
4-Benzo[1,3]dioxol-5-yl-5-methyl-2-phenyl-1H-imidazole (3g). White solid (81%
yield): mp 184–186 °C; IR (KBr) 3434, 3355, 3276, 3199, 3122, 2927, 2547,
1865, 1735, 1693, 1602, 1525, 1346, 1249, 1124, 1041, 939, 815, 688.54 cmÀ1
;
1H NMR (400 MHz, DMSO-d6) d 8.00 (d, J = 7.2 Hz, 2H), 7.44 (t, J = 7.6 Hz, 2H),
7.32 (t, J = 7.2 Hz, 1H), 7.27–7.26 (m, 1H), 7.17–7.15 (m, 1H), 6.97 (d, J = 8.0 Hz,
1H), 6.04 (s, 2H), 2.41 (s, 3H); 13C NMR (100 MHz, DMSO-d6) d 159.3, 147.8,
145.9, 143.8, 130.8, 129.0, 128.8, 128.2, 127.9, 125.1, 120.0, 108.7, 107.2, 101.2,
12.3; Anal. Calcd for C17H14N2O2: C, 73.37; H, 5.07; N, 10.07%. Found: C, 73.39;
H, 5.10; N, 10.10%.
4-(4-Methoxy-phenyl)-5-methyl-2-(3-nitro-phenyl)-1H-imidazole (3k). Yellow
solid (82% yield): mp 242–243 °C; IR (KBr) 3388, 3184, 3082, 2912, 2744,
2638, 1643, 1608, 1525, 1346, 1253, 842 cmÀ1 1H NMR (400 MHz, DMSO-d6) d
;
8.84 (s, 1H), 8.43 (d, J = 8.0 Hz, 1H), 8.19 (d, J = 8.0 Hz, 1H), 7.76 (t, J = 8.0 Hz,
1H), 7.62 (d, J = 8.4 Hz, 2H), 7.03 (d, J = 8.8 Hz, 2H), 3.79 (s, 3H), 2.43 (s, 3H); 13
C
NMR (100 MHz, DMSO-d6) d 158.2, 148.3, 141.0, 135.2, 130.9, 130.5, 129.4,
127.8, 126.6, 122.6, 119.2, 114.3, 114.0, 55.1, 11.8; Anal. Calcd for C17H15N3O3:
C, 66.01; H, 4.89; N, 13.58%. Found: C, 66.08; H, 4.92; N, 13.60%.
4-Furan-2-yl-5-methyl-2-phenyl-1H-imidazole (3h). White solid (79% yield): mp
172–174 °C; IR (KBr) 3355, 3151, 3078, 2927, 2852, 2646, 2397, 2310, 2231,
1895, 1745, 1728, 1604, 1448, 1267, 1159, 1012, 844, 750, 700 cmÀ1
;
1H NMR
2,5-Dimethyl-4-phenyl-1H-imidazole (3l). Yellowish liquid (55% yield): IR (KBr)
3487, 3043, 2665, 2590, 1893, 1818, 1596, 1444, 1390, 1271, 1170, 1095, 923,
(400 MHz, DMSO-d6) d 8.23 (d, J = 7.6 Hz, 2H), 7.89 (s, 1H), 7.63–7.60 (m, 3H),
7.16 (s, 1H), 6.71–6.70 (m, 1H), 2.55 (s, 3H); 13C NMR (100 MHz, DMSO-d6) d
144.0, 143.1, 131.8, 129.6, 127.2, 126.6, 124.2, 122.2, 112.3, 109.3, 10.6; Anal.
Calcd for C14H12N2O: C, 74.98; H, 5.39; N, 12.49%. Found: C, 75.03; H, 5.43; N,
12.54%.
781 cmÀ1 1H NMR (400 MHz, CDCl3) d 7.36 (t, J = 7.2 Hz, 2H), 7.28 (t, J = 7.6 Hz,
;
1H), 7.18 (d, J = 8.4 Hz, 2H), 2.33 (s, 3H) 2.20 (s, 3H); 13C NMR (100 MHz, CDCl3)
d 165.1, 158.6, 130.4, 129.1, 129.0, 128.7, 127.4, 116.6, 11.5, 10.7; Anal. Calcd
for C11H12N2: C, 76.71; H, 7.02; N, 16.27%. Found: C, 76.78; H, 7.04; N, 16.30%.
5-Ethyl-2,4-diphenyl-1H-imidazole (3i). Pale yellow solid (70% yield): mp 188–