One-step synthesis of 2-aryl-4,5-diphenylimidazoles under microwave irradiation

Article abstract of DOI:10.1081/SCC-200057281

A series of 2-aryl-4,5-diphenylimidazoles were synthesized by a one-step condensation reaction of benzil, aromatic aldehyde, and ammonium acetate in acetic acid under microwave irradiation. The reactions were completed in 4-11 min with good yields and easy workup. Copyright Taylor & Francis, Inc.

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One‐Step Synthesis of
2‐Aryl‐4,5‐diphenylimidazoles
Under Microwave Irradiation
Jian‐Feng Zhou a , Yuan‐Zhi Song a , Yan‐Ling Yang a
Yu‐Lan Zhu b & Shu‐Jiang Tu c
,
a Department of Chemistry, Huaiyin Teachers
College, Huaian, China
b Key Laboratory of Low‐Dimensional Materials
Chemistry of Jiangsu Province, Huaian, China
c Department of Chemistry, Xuzhou Normal
University, Xuzhou, China
Version of record first published: 16 Aug 2006.
To cite this article: Jian‐Feng Zhou , Yuan‐Zhi Song , Yan‐Ling Yang , Yu‐Lan Zhu
& Shu‐Jiang Tu (2005): One‐Step Synthesis of 2‐Aryl‐4,5‐diphenylimidazoles Under
Microwave Irradiation, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 35:10, 1369-1373
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Synthetic Communicationsw, 35: 1369–1373, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200057281
One-Step Synthesis of
2-Aryl-4,5-diphenylimidazoles Under
Microwave Irradiation
Jian-Feng Zhou
Department of Chemistry, Huaiyin Teachers College, Huaian, China and
Key Laboratory of Low-Dimensional Materials Chemistry of Jiangsu
Province, Huaian, China
Yuan-Zhi Song
Department of Chemistry, Huaiyin Teachers College, Huaian, China
Yan-Ling Yang and Yu-Lan Zhu
Department of Chemistry, Huaiyin Teachers College, Huaian, China and
Key Laboratory of Low-Dimensional Materials Chemistry of Jiangsu
Province, Huaian, China
Shu-Jiang Tu
Department of Chemistry, Xuzhou Normal University, Xuzhou, China
Abstract: A series of 2-aryl-4,5-diphenylimidazoles were synthesized by a one-step
condensation reaction of benzil, aromatic aldehyde, and ammonium acetate in acetic
acid under microwave irradiation. The reactions were completed in 4–11 min with
good yields and easy workup.
Keywords: Arylimidazole, arylaldehyde, microwave irradiation, synthesis
Triarylimidazole derivatives have many biological activities, for example,
herbicidal,[1] fungicidal,[2] antiinflammatory,[3] and antithrombotic activi-
ties.[4] In addition, they are used in photography as photosensitive
Received in Japan December 6, 2004
Address correspondence to Jian-Feng Zhou, Department of Chemistry, Huaiyin
Teachers College, Huaian 223300, China. E-mail: jfchow@sohu.com
1369

1370
J.-F. Zhou et al.
compounds.[5] Some substituted triarylimidazole are selective antagonists of
the glucagon receptor[6] and inhibitors of IL-1 biosynthesis.[7] Usually, the
preparation of triarylimidazole can be realized through the cyclocondensation
of benzil, aromatic aldehyde, and ammonia or ammonium acetic in HOAc as
the solvent under reflux and N2 atmosphere. However, the classic cyclo-
condensation requires long reaction times (1.5–10 h), has low yields, and
suffers from tedious and time-consuming workup.[8–10]
The wide applicability of microwave irradiation in chemical reaction
enhancement is due to the high reaction rate with formation of cleaner
products and operational simplicity.[11,12] Recently, Balalaie and coworkers
reported zeolite HY and silica gel as new and efficient heterogeneous catalysts
for the synthesis of triarylimidazoles under microwave irradiation,[13] and
Khmelnitsky and coworkers reported the synthesis of triarylimidazoles by
MICROCOS (microwave-assisted combinatorial synthesis) under solvent-
free conditions.[14,15] However, our research shows that one-step synthesis
of 2-aryl-4,5-diphenylimidazoles from benzil and aromatic aldehyde in the
presence of NH4OAc in HOAc as the solvent under microwave irradiation
was very easy and the reaction was finished in short time with good yields
and easier workup.
As a continuation of our interest in the development of efficient and
simple procedures for the synthesis of heterocyclic compounds,[16] we now
report an efficient synthesis of 2-aryl-4,5-diphenylimidazoles by one-step
cyclocondensation of benzil and aromatic aldehyde in the presence of
NH4OAc in HOAc as the solvent under microwave irradiation. The
reactions were generally finished in 4–11 minutes with 70–98% yields and
easy workup. All products (except 3j, 3 k, 3l, and 3m) are known
compounds which were characterized by mp, IR, 1H NMR, MS, and
Elemental analyzer.
Scheme 1.

Synthesis of 2-Aryl-4,5-diphenylimidazoles
1371
Table 1. Microwave irradiation synthesis of 4a–m
Time
(min)
Yield
(%)a
Compound
Ar
Mp 8C (Lit.)
4a
4b
4c
4d
4e
4f
C6H5
2-ClC6H4
4-ClC6H4
10
5
98
85
91
71
86
97
74
98
98
84
73
70
98
275–276 (276–277)[13]
196–197 (197.3–197.8)[10]
261–262 (261–263)[13]
238–239 (236–238)[13]
256–258 (257–258)[13]
226–228 (227–228)[13]
230–231 (231–232)[13]
267–268 (268–268.5)[10]
213–214 (214–215)[10]
216–218
8
4-O2NC6H4
4-(CH3)2NC6H4
4-CH3O C6H4
4-CH3C6H4
4-HOC6H4
4
6
10
8
4g
4h
4i
9
2-HOC6H4
8
4j
3,4-(CH3O)2C6H3
3,4-(OCH2O)C6H3
3-O2NC6H4
Furyl
9
4k
4l
11
4.5
5
300
.300
202–203
4m
aYields of the isolated products.
EXPERIMENTAL SECTION
Mps were determined in WRS-1B digital melting point apparatus and uncor-
rected. IR spectra were recorded on a Nicolet Avatar 360FT-IR instrument.
1H NMR were measured on a Burke 300 MHz spectrometer in CDCl3 with
TMS as internal standard. MS spectra were recorded on a LCQ Advantage
instrument. Elemental analyses were determined using Perkin-Elmer 240C
elemental analyzer. The reactions were carried out with a modified commer-
cial microwave oven (Sanle WP650D 650 w) under atmospheric pressure. All
the reagents are commercially available.
General Procedure for 2-Aryl-4,5-diphenylimidazole Derivatives
A mixture of the benzil (1 mmol), aromatic aldehyde (1 mmol), and NH4OA c
(1 mmol) in the presence of in HOAc (3 mL) in an Erlenmeyer flask (25 mL)
equipped with reflux condenser was irradiated in a microwave oven for
0.5–7 min (as indicated by TLC). Ice water was added to reaction mixture.
The crude product was collected and recystallized from ethanol and water
(v : v ¼ 1.5 : 1).
4j: Mp 216–2188C; 1H NMR (400 MHz, DMSO-d6) d 7.66–7.30
(m, 13H, arom H), 3.85 (s, 6H, 2OCH3); IR (KBr) n: 3318, 3062, 3002,
2960, 1593, 1512, 1265, 1023, 765 cm21; MS (M þ H)þ 357; Anal. calcd.
for C23H20N2O2: C, 77.53; H, 5.62; N, 7.87. Found: C, 77.24; H, 5.59; N, 7.82.
1
4k: Mp 3008C; H NMR (400 MHz, DMSO-d6) d 7.63–7.32 (m, 13H,
arom H), 6.09 (s, 2H, OCH2O); IR (KBr) n: 3426, 3062, 3021, 2873, 1603,

1372
J.-F. Zhou et al.
1502, 1483, 1038, 765 cm21; MS (M þ H)þ 341; Anal. calcd. for
C22H16N2O2: C, 77.65; H, 4.71; N, 8.24. Found: C, 77.35; H, 4.67; N, 8.19.
1
4l: Mp .3008C; H NMR (400 MHz, DMSO-d6) d 8.97 (s, 1H, NH),
7.79–7.34 (m, 14H, arom H); IR (KBr) n: 3380, 3068, 1541, 1522, 1348,
1348, 1050, 767 cm21; MS (M þ H)þ 342; Anal. calcd. for C21H15N3O2: C,
73.90; H, 4.40; N, 12.32. Found: C, 73.66; H, 4.37; N, 12.26.
4m: Mp 202–2038C;1H NMR (400 MHz, DMSO-d6) d 7.94–6.65
(m, 13H, arom H); IR (KBr) n: 3380, 3119, 3062, 1599, 1149, 1015,
740 cm21; MS (M þ H)þ 287; Anal. calcd. for C19H14N2O: C, 79.72; H,
5.24; N, 9.79. Found: C, 79.31; H, 5.21; N, 9.74.
ACKNOWLEDGMENTS
We thank the Nature Science Foundation of Jiangsu Province Education
Department of China (No. 02KJD 150006) and the Nature Science Foundation
of China (Nos. 20372057, 20162005) for financial support.
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