Solvent-free reaction between acenaphthoquinone, various benzils and ammonium acetate: Synthesis of 9,10-diaryl-7H-benzo[d,e]imidazo[2,1-a] isoquinolin-7-ones

Article abstract of DOI:10.1016/j.tetlet.2011.01.091

A simple synthesis of benzo[d,e]imidazo[2,1-a]isoquinolines is described. Heating a mixture of acenaphthoquinone, a benzil, and ammonium acetate under solvent-free conditions afforded 9,10-diaryl-7H-benzo[d,e]imidazo[2,1-a] isoquinolin-7-ones in good to e

Full text of DOI:10.1016/j.tetlet.2011.01.091

Tetrahedron Letters 52 (2011) 2299–2301
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Solvent-free reaction between acenaphthoquinone, various benzils and
ammonium acetate: synthesis of 9,10-diaryl-7H-benzo[d,e]imidazo[2,1-a]
isoquinolin-7-ones
Mehdi Adib a, , Bagher Mohammadi b, Samira Ansari a, Hamid Reza Bijanzadeh c, Long-Guan Zhu d
⇑
a School of Chemistry, University College of Science, University of Tehran, PO Box 14155–6455, Tehran, Iran
b Member of Young Researchers Club, Islamic Azad University, Takestan Branch, Takestan, Iran
c Department of Chemistry, Tarbiat Modarres University, PO Box 14115–175, Tehran, Iran
d Chemistry Department, Zhejiang University, Hangzhou 310027, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A simple synthesis of benzo[d,e]imidazo[2,1-a]isoquinolines is described. Heating a mixture of acenaph-
thoquinone, a benzil, and ammonium acetate under solvent-free conditions afforded 9,10-diaryl-7H-
benzo[d,e]imidazo[2,1-a]isoquinolin-7-ones in good to excellent yields.
Received 25 August 2010
Revised 5 January 2011
Accepted 21 January 2011
Available online 27 January 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Acenaphthoquinone
Benzils
9,10-Diaryl-7H-benzo[d,e]imidazo[2,1-
a]isoquinolin-7-ones
Imidazole synthesis
Imidazoles, an important class of heterocyclic compounds, are
of both biological and chemical interest, and their involvement in
catalytic processes at the active sites of enzymes have been well
documented. They are part of a large number of highly significant
biomolecules such as the essential amino acid histidine, biotin,
and imidazole alkaloids.1–4 The potency and wide applicability of
the imidazole pharmacophore can be attributed to its hydrogen
bond donor–acceptor ability, as well as its high affinity for metals
present in many protein active sites.5 Some imidazole derivatives
act as p38 mitogen activated protein kinase inhibitors,6a B-Raf ki-
nase inhibitors,6b transforming growth factor b1 type 1 activin
receptor-like kinase inhibitors,6c and cyclooxygenase-2 inhibi-
tors.6d Appropriately substituted imidazoles are used extensively
as glucagon receptors,7a CB1 cannabinoid receptor antagonists,7b
modulators of P-glycoprotein mediated multidrug resistance,7c
antibacterials,7d antitumor agents,7e and pesticides.7f Recent
advances in green chemistry and organometallic catalysis have ex-
tended the application of imidazoles as precursors to ionic liquids8
and N-heterocyclic carbenes.9
basis of the number of ring atoms in each of the components being
cyclized: (a) single bond formation, (b) formation of two bonds,
from [4+1] or [3+2] atom fragments, (c) formation of three or four
bonds; (ii) transformation of an existing heterocyclic ring, includ-
ing expansion of smaller rings, contraction of larger rings, and
transformation of other five-membered rings.3
There are several methods for the syntheses of highly substi-
tuted imidazoles. The most frequently used methods involve:
synthesis via hetero-Cope rearrangement,10 four-component con-
densation of arylglyoxals, primary amines, carboxylic acids, and
isocyanides on Wang resin,11 reaction of N-(2-oxo)amides with
12
NH4O2CCF3
and reaction of N-alkyl-N-(b-keto)amides with
NH4OAc.13 The synthesis of tri-/tetra-substituted imidazoles via
condensation of aldehydes, benzils, and NH4OAc/primary amines
is also a well established procedure.14
Fused imidazoles, for example, 7H-benzo[d,e]imidazo[2,1-a]iso-
quinolin-7-ones, have been used as electron acceptor molecules in
organic photovoltaic devices,15 discotic and lyotropic liquid crystal
systems,16,17 organic n-channel field-effect transistors,18 and as
new dyes and pigments.19,20 Some derivatives modulate interac-
tion of nerve growth factor with neurotrophic receptors,21 and
some examples have been polymerized and used in industrial
water systems.22
The most common synthetic routes reported for the preparation
of imidazole derivatives involve: (i) cyclizations, classified on the
⇑
The most common synthesis of 7H-benzo[d,e]imidazo
[2,1-a]isoquinolin-7-ones involves condensation of the corre-
Corresponding author. Tel./fax: +98 21 66495291.
E-mail address: madib@khayam.ut.ac.ir (M. Adib).
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.01.091

2300
M. Adib et al. / Tetrahedron Letters 52 (2011) 2299–2301
Ar
Ar
O
O
N
N
O
Ar
O
solvent-free
200 °C, 3 h
+
+
NH4OAc
O
Ar
3
1
2
Scheme 1.
sponding 1,8-naphthalenedicarboxylic anhydrides and vicinal
diamines.18,19,23
As part of our current studies on the development of efficient
and simple syntheses of biologically active heterocyclic com-
pounds,24 we herein describe a new synthesis of 7H-benzo[d,e]
imidazo[2,1-a]isoquinolin-7-ones. Thus a mixture of acenaphtho-
quinone (1), benzil 2 and excess ammonium acetate underwent a
1:1:2 addition reaction, under solvent-free conditions, to produce
the corresponding 7H-benzo[d,e]imidazo[2,1-a]isoquinolin-7-
ones, 3a–k in 80–92% yields (Scheme 1 and Table 1). All the reac-
tions proceeded at 200 °C and reached completion within 3 h. TLC
analysis of the reaction mixtures clearly indicated the formation of
the corresponding highly fluorescent 7H-benzo[d,e]imidazo[2,1-
a]isoquinolin-7-ones 3.25
The structures of the isolated products 3 were deduced on the
basis of IR, 1H and 13C NMR spectroscopy, mass spectrometry,
and elemental analysis. The mass spectrum of 3c displayed the
molecular ion (M+) peak at m/z = 400, which was consistent with
the 1:1:2 adduct of acenaphthoquinone, 1,2-bis(4-methyl-
phenyl)-1,2-ethanedione and ammonia with loss of three H2O mol-
ecules. The IR spectrum of 3c showed an absorption at 1695 cmÀ1
indicating the presence of an amide. The 1H NMR spectrum of 3c
exhibited two sharp singlets at 2.34 and 2.49 ppm due to the
methyl groups of the two aryl substituents along with characteris-
tic signals with appropriate chemical shifts and coupling constants
for the 14 aromatic H atoms. The 1H-decoupled 13C NMR spectrum
of 3c showed characteristic signals at 21.25 and 21.59 ppm (due to
the two methyl substituents), a deshielded signal at 160.40 ppm
(due to the amide carbonyl group), as well as 21 other distinct res-
onances (10 CH and 11 C) in agreement with the proposed
structure.25
Figure 1. ORTEP diagram of the molecular structure of 3k.
yields of the products, the use of simple and readily available
starting materials and fairly short reaction times are the main
advantages of this reaction. The highly fluorescent 7H-benzo
[d,e]imidazo[2,1-a]isoquinolin-7-ones prepared may find useful
applications in bioorganic and medicinal chemistry, and also in
light-emitting devices. Further investigations on the reaction
mechanism, the scope and the limitations of this reaction are
underway.
Acknowledgment
This research was supported by the Research Council of the Uni-
versity of Tehran as research project (6102036/1/03).
References and notes
1. Grimmett, M. R. In Comprehensive Heterocyclic Chemistry I; Katritzky, A. R., Rees,
C. W., Potts, K. T., Eds.; Pergamon Press: New York, 1984; Vol. 5, pp 457–497.
2. Grimmett, M. R. In Comprehensive Heterocyclic Chemistry II; Katritzky, A. R.,
Rees, C. W., Scriven, E. F. V., Eds.; Pergamon Press: New York, 1996; Vol. 3, pp
77–220.
3. Xi, N.; Huang, Q.; Liu, L. In Comprehensive Heterocyclic Chemistry III; Katritzky, A.
R., Ramsden, C. A., Scriven, E. F. V., Taylor, R. J. K., Eds.; Elsevier Science: Oxford,
2008; Vol. 4, pp 143–348. and references therein.
Single-crystal X-ray analysis of product 3k confirmed conclu-
sively its structure, and by analogy, those of the other isolated
products. An ORTEP diagram of 3k is shown in Figure 1.26
In conclusion, we have reported a novel reaction for the prepa-
ration of 7H-benzo[d,e]imidazo[2,1-a]isoquinolin-7-ones from an
addition reaction between acenaphthoquinone, various benzils,
and ammonium acetate. Solvent-free conditions, good to excellent
4. De Luca, L. Curr. Med. Chem. 2006, 13, 1–23.
5. Rotstein, D. M.; Kertesz, D. J.; Walker, K. A. M.; Swinney, D. C. J. Med. Chem.
1992, 35, 2818–2825.
6. (a) Lee, J. C.; Laydon, J. T.; McDonnell, P. C.; Gallagher, T. F.; Kumar, S.; Green, D.;
McNulty, D.; Blumenthal, M. J.; Keys, J. R.; Vatter, S. W. L.; Strickler, J. E.;
McLaughlin, M. M.; Siemens, I. R.; Fisher, S. M.; Livi, G. P.; White, J. R.; Adams, J.
L.; Young, P. R. Nature 1994, 372, 739–746; (b) Takle, A. K.; Brown, M. J. B.;
Davies, S.; Dean, D. K.; Francis, G.; Gaiba, A.; Hird, A. W.; King, F. D.; Lovell, P. J.;
Naylor, A.; Reith, A. D.; Steadman, J. G.; Wilson, D. M. Bioorg. Med. Chem. Lett.
2006, 16, 378–381; (c) Khanna, I. K.; Weier, R. M.; Yu, Y.; Xu, X. D.; Koszyk, F. J.;
Collins, P. W.; Koboldt, C. M.; Veenhuizen, A. W.; Perkins, W. E.; Casler, J. J.;
Masferrer, J. L.; Zhang, Y. Y.; Gregory, S. A.; Seibert, K.; Isakson, P. C. J. Med.
Chem. 1997, 40, 1634–1647; (d) Lange, J. H. M.; Van Stuivenberg, H. H.; Coolen,
H. K. A. C.; Adolfs, T. J. P.; McCreary, A. C.; Keizer, H. G.; Wals, H. C.; Veerman,
W.; Borst, A. J. M.; de Looff, W.; Verveer, P. C.; Kruse, C. G. J. Med. Chem. 2005,
48, 1823–1838.
7. (a) de Laszlo, S. E.; Hacker, C.; Li, B.; Kim, D.; MacCoss, M.; Mantlo, N.;
Pivnichny, J. V.; Colwell, L.; Koch, G. E.; Cascieri, M. A.; Hagmann, W. K. Bioorg.
Med. Chem. Lett. 1999, 9, 641–646; (b) Eyers, P. A.; Craxton, M.; Morrice, N.;
Cohen, P.; Goedert, M. Chem. Biol. 1998, 5, 321–328; (c) Newman, M. J.; Rodarte,
J. C.; Benbatoul, K. D.; Romano, S. J.; Zhang, C.; Krane, S.; Moran, E. J.; Uyeda, R.
T.; Dixon, R.; Guns, E. S.; Mayer, L. D. Cancer Res. 2000, 60, 2964–2972; (d)
Antolini, M.; Bozzoli, A.; Ghiron, C.; Kennedy, G.; Rossi, T.; Ursini, A. Bioorg. Med.
Chem. Lett. 1999, 9, 1023–1028; (e) Wang, L.; Woods, K. W.; Li, Q.; Barr, K. J.;
McCroskey, R. W.; Hannick, S. M.; Gherke, L.; Credo, R. B.; Hui, Y.-H.; Marsh, K.;
Warner, R.; Lee, J. Y.; Zielinsky-Mozng, N.; Frost, D.; Rosenberg, S. H.; Sham, H.
Table 1
Synthesis of 7H-benzo[d,e]imidazo [2,1-a]isoquinolin-7-
ones 3a–k
Product
Ar
Yielda (%)
3a
3b
3c
3d
3e
3f
3g
3h
3i
C6H5
92
85
88
83
80
89
87
86
89
80
86
3-CH3C6H4
4-CH3C6H4
3-CH3OC6H4
4-CH3OC6H4
4-O2NC6H4
4-ClC6H4
4-BrC6H4
4-FC6H4
3j
3k
2-Furyl
2-Pyridyl
a
Isolated yield.

M. Adib et al. / Tetrahedron Letters 52 (2011) 2299–2301
2301
L. J. Med. Chem. 2002, 45, 1697–1711; (f) Maier, T.; Schmierer, R.; Bauer, K.;
Bieringer, H.; Buerstell, H.; Sachse, B. U.S. Patent 4820335, 1989; Chem. Abstr.
1989, 111, 19494w.
(d, J = 7.2 Hz, 1H, CH). 13C NMR (125.8 MHz, DMSO-d6): d 120.34 and 122.79
(2C), 125.00 (CH), 125.14 and 126.62 (2C), 127.09, 127.16, 127.42, 127.57,
128.05, 128.12, 128.35, 130.69 and 130.70 (9CH), 131.09 (C), 131.64 (CH),
131.71 and 133.06 (2C), 135.67 (CH), 139.83 and 144.78 (2C) 159.47 (C@O).
8. (a) Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Chem. Rev. 2002, 102, 3667–3692;
(b) Chowdhury, S.; Mohan, R. S.; Scott, J. L. Tetrahedron 2007, 63, 2363–2389.
9. (a) Bourissou, D.; Guerret, O.; Gabbai, F. P.; Bertrand, G. Chem. Rev. 2000, 100,
39–92; (b) Arnold, P. L.; Liddle, S. T. Chem. Commun. 2006, 3959–3971; (c) Kühl,
O. Chem. Soc. Rev. 2007, 36, 592–607.
10. Lantos, I.; Zhang, W. Y.; Shui, X.; Eggleston, D. S. J. Org. Chem. 1993, 58, 7092–
7095.
11. (a) Zhang, C.; Moran, E. J.; Woiwode, T. F.; Short, K. M.; Mjalli, A. M. M.
Tetrahedron Lett. 1996, 37, 751–754; (b) Sarshar, S.; Siev, D.; Mjalli, A. M. M.
Tetrahedron Lett. 1996, 37, 835–838.
12. Claiborne, C. F.; Liverton, N. J.; Nguyen, K. T. Tetrahedron Lett. 1998, 39, 8939–
8942.
13. Lee, H. B.; Balasubramanian, S. Org. Lett. 2000, 2, 323–326.
14. Das Sharma, S.; Hazarika, P.; Konwar, D. Tetrahedron Lett. 2008, 49, 2216–2220.
and references cited therein.
15. Shin, W. S.; Jeong, H. H.; Kim, M. K.; Jin, S. H.; Kim, M. R.; Lee, J. K.; Lee, J. W.;
Gal, Y. S. J. Mater. Chem. 2006, 16, 384–390.
16. Wicklein, A.; Kohn, P.; Ghazaryan, L.; Thurn-Albrecht, T.; Thelakkat, M. Chem.
Commun. 2010, 46, 2328–2330.
17. Nazarov, V. V.; Sidorenko, E. N. U.S. Patent 215,015 A1, 2004; Chem. Abstr. 2004,
141, 386740m.
18. Ortiz, R. P.; Herrera, H.; Blanco, R.; Huang, H.; Facchetti, A.; Marks, T. J.; Zheng,
Y.; Segura, J. L. J. Am. Chem. Soc. 2010, 132, 8440–8452.
19. Graciet, J. C. Eur. Patent 1,422,267 A1, 2004; Chem. Abstr. 2004, 140, 408230d.
20. Flatt, T. U.S. Patent 139,813 A1, 2008; Chem. Abstr. 2008, 149, 33650k.
21. Vohra, R.; Dube, G.; Gan, Z.; Gill, N.; Cui, X. U.S. Patent 82,368 A1, 2009; Chem.
Abstr. 2009, 150, 351920d.
22. Morris, J. D.; Moriarty, B. E. Wei, M.; Murray, P. G.; Reddinger, J. L. U.S. Patent
135,124 A1, 2004; Chem. Abstr. 2004, 141, 76327n.
23. Feiler, L.; Langhals, H.; Polborn, K. Liebigs Ann. 1995, 1229–1244.
24. (a) Adib, M.; Ansari, S.; Feizi, S.; Bijanzadeh, H. R. Synlett 2010, 921–923; (b)
Adib, M.; Ansari, S.; Fatemi, S.; Bijanzadeh, H. R.; Zhu, L. G. Tetrahedron 2010,
66, 2723–2727; (c) Adib, M.; Ansari, S.; Mohammadi, A.; Bijanzadeh, H. R.
Tetrahedron Lett. 2010, 51, 30–32; (d) Adib, M.; Ansari, S.; Feizi, S.; Asgarian
Damavandi, J.; Mirzaei, P. Synlett 2009, 3263–3266; (e) Adib, M.; Mahdavi, M.;
Ansari, S.; Malihi, F.; Zhu, L. G.; Bijanzadeh, H. R. Tetrahedron Lett. 2009, 50,
7246–7248; (f) Adib, M.; Sheibani, E.; Bijanzadeh, H. R.; Zhu, L. G. Tetrahedron
2008, 64, 10681–10686; (g) Adib, M.; Sayahi, M. H.; Ziyadi, H.; Zhu, L. G.;
Bijanzadeh, H. R. Synthesis 2008, 3289–3294; (h) Adib, M.; Mohammadi, B.;
Bijanzadeh, H. R. Synlett 2008, 3180–3182; (i) Adib, M.; Mohammadi, B.;
Bijanzadeh, H. R. Synlett 2008, 177–180; (j) Adib, M.; Sayahi, M. H.; Ziyadi, H.;
Bijanzadeh, H. R.; Zhu, L. G. Tetrahedron 2007, 63, 11135–11140.
9,10-Bis(4-methylphenyl)-7H-benzo[d,e]imidazo[2,1-a]isoquinolin-7-one
(3c):
Yield: 0.35 g (88%); yellow crystals, mp 400–402 °C. IR (KBr) (
m
max/cmÀ1):
1695 (C@O), 1605, 1548, 1494, 1448, 1378, 1344, 1300, 1240, 1172, 1113,
1023, 965, 908, 876, 824, 770, 728, 682. EI–MS, m/z (%): 400 (M+, 28), 384 (4),
371 (2), 343 (5), 254 (7), 177 (2), 119 (100), 91 (14), 65 (14), 55 (9), 43 (9). Anal.
Calcd for C28H20N2O (400.47): C, 83.97; H, 5.03; N, 7.00. Found: C, 83.81; H,
5.23; N, 6.85. 1H NMR (500.1 MHz, CDCl3): d 2.34 and 2.49 (2s, 6H, 2CH3), 7.11
(d, J = 8.1 Hz, 2H, 2CH), 7.31 (d, J = 8.0 Hz, 2H, 2CH), 7.42 (d, J = 8.0 Hz, 2H,
2CH), 7.55 (d, J = 8.1 Hz, 2H, 2CH), 7.72 (t, J = 7.8 Hz, 1H, CH), 7.76 (t, J = 7.8 Hz,
1H, CH), 8.03 (d, J = 8.1 Hz, 1H, CH), 8.22 (d, J = 8.0 Hz, 1H, CH), 8.60 (d,
J = 6.7 Hz, 1H, CH), 8.77 (d, J = 7.2 Hz, 1H, CH). 13C NMR (125.8 MHz, CDCl3): d
21.25 and 21.59 (2CH3), 121.18 and 123.50 (2C), 125.57 (CH), 125.93 (C),
126.68, 127.39 and 127.67 (3CH), 128.46 (C), 128.96 and 129.13 (2CH), 129.74
(C), 130.16 (CH), 130.59 (C), 130.74 and 131.99 (2CH), 132.05 (C), 135.27 (CH),
137.23, 138.34, 141.20 and 145.23 (4C), 160.40 (C=O). 9,10-Bis(4-chlorophenyl)-
7H-benzo[d,e]imidazo[2,1-a]isoquinolin-7-one (3g): Yield: 0.38 g (87%); yellow
crystals, mp 441–444 °C. IR (KBr) (m
max/cmÀ1): 1703 (C@O), 1585, 1551, 1472,
1392, 1345, 1303, 1231, 1168, 1129, 1088, 1015, 965, 910, 836, 775, 740. EI–
MS, m/z (%): 444 (M+ 37Cl2, <1), 442 (M+ 37Cl35Cl, 3), 440 (M+ 35Cl2, 4), 380 (58),
363 (18), 349 (19), 315 (17), 293 (18), 273 (47), 179 (43), 149 (22), 111 (20), 97
(31), 83 (43), 69 (51), 57 (100), 43 (78). Anal. Calcd for C26H14Cl2N2O (441.31):
C, 70.76; H, 3.20; N, 6.35. Found: C, 70.70; H, 3.24; N, 6.34. 1H NMR
(500.1 MHz, CDCl3): d 7.27 (d, J = 8.6 Hz, 2H, 2CH), 7.44 (d, J = 8.6 Hz, 2H, 2CH),
7.47 (d, J = 8.6 Hz, 2H, 2CH), 7.53 (d, J = 8.6 Hz, 2H, 2CH), 7.78 (dd, J = 7.8,
7.6 Hz, 1H, CH), 7.81 (dd, J = 7.9, 7.5 Hz, 1H, CH), 8.11 (d, J = 8.2 Hz, 1H, CH),
8.29 (d, J = 8.0 Hz, 1H, CH), 8.64 (d, J = 7.3 Hz, 1H, CH), 8.79 (d, J = 7.3 Hz, 1H,
CH). 13C NMR (125.8 MHz, CDCl3): d 120.83 and 123.14 (2C), 125.97 (CH),
126.00 (C), 126.86, 127.50, 128.58, 128.80 and 129.08 (5CH), 129.09 and
129.53 (2C), 130.72 (CH), 131.56 and 132.12 (2C), 132.22 and 132.31 (2CH),
133.71 and 134.98 (2C), 135.70 (CH), 140.61 and 145.81 (2C) 160.44 (C@O).
9,10-Di(2-pyridyl)-7H-benzo[d,e]imidazo[2,1-a]isoquinolin-7-one (3k): Yield:
0.32 g (86%); red crystals; mp 374–376 °C. IR (KBr) (m
max/cmÀ1): 1696 (C@O),
1584, 1469, 1423, 1384, 1342, 1298, 1224, 1156, 1087, 1034, 992, 908, 838,
777, 742, 710, 681. EI–MS, m/z (%): 374 (M+, 100), 345 (40), 317 (5), 197 (12),
187 (13), 172 (15), 152 (11), 126 (8), 78 (16), 57 (13), 43 (13). Anal. Calcd for
C24H14N4O (374.39): C, 76.99; H, 3.77; N, 14.96. Found: C, 76.76; H, 3.88; N,
14.72. 1H NMR (500.1 MHz, CDCl3): d 7.13 (ddd, J = 7.4, 4.9, 1.1 Hz, 1H, CH),
7.41 (ddd, J = 7.6, 4.8, 1.1 Hz, 1H, CH), 7.59 (dt, J = 1.8, 7.8 Hz, 1H, CH), 7.62 (d,
J = 7.8 Hz, 1H, CH), 7.66 (d, J = 7.9 Hz, 1H, CH), 7.73 (dd, J = 7.8, 7.6 Hz, 1H, CH),
7.77 (dd, J = 7.8, 7.6 Hz, 1H, CH), 7.81 (dt, J = 1.8, 7.7 Hz, 1H, CH), 8.07 (d,
J = 8.1 Hz, 1H, CH), 8.25 (d, J = 8.1 Hz, 1H, CH), 8.54 (dd, J = 4.1, 0.9 Hz, 1H, CH),
8.60 (dd, J = 7.3, 0.9 Hz, 1H, CH), 8.81 (d, J = 4.2 Hz, 1H, CH), 8.87 (dd, J = 7.3,
0.8 Hz, 1H, CH). 13C NMR (125.8 MHz, CDCl3): d 120.75 (C), 122.37, 122.67 and
123.15 (3CH), 126.14 (C), 126.48, 126.56, 126.72 and 127.40 (4CH), 127.59 (C),
130.81 (CH), 132.09 (C), 132.33, 135.70, 135.96 and 136.08 (4CH), 138.12,
141.76 and 148.30 (3C), 149.28 and 149.59 (2CH), 151.06 and 152.11 (2C),
160.15 (C@O).
25. General procedure for the preparation of compounds 3a–k:
A mixture of
acenaphthoquinone (1 mmol), the appropriate benzil (1 mmol), and
ammonium acetate (4 mmol) was heated at 200 °C for 3 h. The reaction
mixture was cooled to room temperature and the product was purified by
column chromatography using n-hexane–EtOAc (3:1) as eluent. 9,10-Diphenyl-
7H-benzo[d,e]imidazo[2,1-a]isoquinolin-7-one (3a): Yield: 0.34 g (92%); yellow
crystals, mp 390–393 °C. IR (KBr) (
m
max/cmÀ1): 1698 (C@O), 1600, 1556, 1485,
26. Selected X-ray crystallographic data for compound 3k: C24H14N4O, orthorhombic,
space group = Pna21, a = 10.5295(20) Å, b = 9.7580(18) Å, c = 17.3399(33) Å,
1388, 1293, 1170, 1158, 1091, 1028, 997, 898, 825, 770, 742, 706. EI–MS, m/z
(%): 372 (M+, 100), 332 (37), 295 (19), 281 (22), 269 (14), 247 (10), 217 (9), 207
(19), 196 (15), 179 (46), 105 (74), 91 (38), 77 (52), 57 (60), 43 (18). Anal. Calcd
for C26H16N2O (372.42): C, 83.85; H, 4.33; N, 7.52. Found: C, 84.04; H, 4.47; N,
7.26. 1H NMR (500.1 MHz, DMSO-d6): d 7.22–7.29 (m, 3H, 3CH), 7.44–7.51 (m,
7H, 7CH), 7.85 (t, J = 7.8 Hz, 1H, CH), 7.86 (t, J = 7.7 Hz, 1H, CH), 8.26 (d,
J = 8.2 Hz, 1H, CH), 8.47 (d, J = 8.2 Hz, 1H, CH), 8.48 (d, J = 7.2 Hz, 1H, CH), 8.62
V = 1781.62(6) Å3, T = 295(2) K, Z = 4, Dcalcd = 1.396 g cmÀ3 = 0.089 mmÀ1
, l ,
1684 observed reflections, final R1 = 0.072, wR2 = 0.173 and for all data
R1 = 0.125, wR2 = 0.205. CCDC 782758 contains the supplementary
crystallographic data for this Letter. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.