A simple one-pot synthesis of functionalised 6-(indol-3-yl)-2,2′-bipyridine derivatives via multi-component reaction under neat condition

Article abstract of DOI:10.1016/j.tetlet.2009.04.121

A series of 4-aryl-6-(1H-indol-3-yl)-2,2-bipyridine-5-carbonitrile derivatives were synthesized via a one-pot multi-component reaction of aromatic aldehydes, 3-(cyanoacetyl)indole and 2-acetyl pyridine in ammonium acetate by conventional heating and micro

Full text of DOI:10.1016/j.tetlet.2009.04.121

Tetrahedron Letters 50 (2009) 4145–4150
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Tetrahedron Letters
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A simple one-pot synthesis of functionalised 6-(indol-3-yl)-2,20-bipyridine
derivatives via multi-component reaction under neat condition
*
Prakasam Thirumurugan, Paramasivan T. Perumal
Organic Chemistry Division, Central Leather Research Institute, Adyar, Chennai 600 020, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 4-aryl-6-(1H-indol-3-yl)-2,2-bipyridine-5-carbonitrile derivatives were synthesized via a one-
pot multi-component reaction of aromatic aldehydes, 3-(cyanoacetyl)indole and 2-acetyl pyridine in
ammonium acetate by conventional heating and microwave irradiation under solvent-free condition.
Also a series of 6,60-di(1H-indol-3-yl)-4,40-diaryl-2,20-bipyridine-5,50-dicarbonitrile derivatives were syn-
thesized using cinnamils, 3-(cyanoacetyl)indole and ammonium acetate. The methodology affords high
yields of product at short reaction time.
Received 18 February 2009
Revised 23 April 2009
Accepted 29 April 2009
Available online 3 May 2009
Keywords:
Ó 2009 Elsevier Ltd. All rights reserved.
6-(Indol-3-yl)-2,20-bipyridine
Multi-component reaction
3-Cyanoacetyl indole
Neat condition
2,20-Bipyridine
Microwave irradiation
Cinnamils
The rapid assembly of molecular diversity is an important goal
of synthetic organic chemistry and is one of the key paradigms of
modern drug discovery. Recently, multi-component reactions
(MCRs) received paramount importance in organic and medicinal
chemistry.1 MCRs leading to interesting heterocyclic scaffolds are
particularly useful for the creation of diverse chemical libraries of
‘drug-like’ molecules for biological screening and the single opera-
tion of MCRs leads to a highly efficient synthesis in combinatorial
chemistry.2–4
The pyridine nucleus is a key constituent, present in a range of
bioactive compounds, occurring both synthetically and naturally
with wide range of biological applications.5,6 Among the successful
examples as drug candidates possessing pyridine nucleus are
streptonigrin, streptonigrone and lavendamycin which are de-
scribed in the literature as anticancer drugs, and cerivastatin is re-
ported as the HMG-CoA enzyme inhibitor.7 Substituted pyridines
are used as leukotriene B-4 antagonists.8 In particular 2,20-pyri-
dines and its derivatives have been invoked as functional modules
within the domain of supramolecular chemistry, coordination
chemistry and material science.9 They are employed as chelating
ligands in coordination chemistry, building blocks in supramolecu-
lar chemistry, as metal-containing polymers, molecular electron-
ics, optoelectronic devices, light-emitting diodes, solar cells and
as photo-activated species.10
On the other hand 3-substituted indole nucleus is prevalent in
numerous natural products and is extremely important in medicinal
chemistry.11,12 Many indole alkaloids are recognized as one of the
rapidly growing groups of marine invertebrate metabolites for their
broad spectrum of biological properties.13,14 In addition 3-substi-
tuted indole scaffolds are found in a number of biologically active
compounds especially with anticancer, anti tumour,15 hypoglyce-
mic, anti-inflammatory, analgesic and anti-pyretic activities.16
Due to the medicinal potential of pyridine and 3-substituted in-
dole derivatives, various methods for the preparation of these com-
pounds have been reported. Marchalin and Kuthan reported the
synthesis of 2, 4, 6 triaryl 3-cyanopyridines using condensation
of 3-aryl-2-benzylidene-3-oxopropanenitrile, acetyl derivative
and ammonium acetate in moderate yields.17 However these
methods suffer from tedious synthetic routes, longer reaction time,
drastic reaction conditions, as well as from narrow substrate
scope.9,10,18–21 To the best of our knowledge, there have been no re-
ports for the synthesis of 6-(indol-3-yl)-2,20-bipyridines. As part of
our ongoing research in the development of novel synthetic routes
for synthesis of biologically active heterocyclic compounds and use
of green chemical techniques in organic synthesis,22,23 herein, we
report a simple and facile one-pot procedure for the synthesis of
6-(indol-3-yl)-2,20-bipyridine derivatives under neat condition.
Initial studies were carried out with reaction of p-tolualdehyde
(1b), 2-acetyl pyridine (2) and 3-(cyanoacetyl)indole (3)24 in the
presence of ammonium acetate in various solvents such as DMF,
methanol, acetonitrile, water and ethanol under solvent-less
* Corresponding author. Tel.: +91 44 24913289; fax: +91 44 24911589.
E-mail address: ptperumal@gmail.com (P.T. Perumal).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.04.121

4146
P. Thirumurugan, P. T. Perumal / Tetrahedron Letters 50 (2009) 4145–4150
R3
R2
R1
CN
CHO
NC
R1
R2
O
NH4OAc
+
+
N
N
H
Neat, 120oC
(OR) MW
irradiation
N
N
R3
O
N
H
1a-j
2
4a-j
3
Scheme 1. Synthesis of 6-(indol-3-yl)-2,20-bipyridine derivatives 4a–j.
condition at 120 °C for 6 h. Excellent results were obtained under
neat condition at 120 °C with high yield in a shorter reaction time.
So we followed the reaction that employs, heating a mixture of
aldehyde, 2-acetyl pyridine, 3-(cyanoacetyl)indole and ammonium
acetate at 120 °C.
The reaction proceeded smoothly with a wide range of func-
tionalized aldehydes, including those containing ether, nitro, halo-
gens and polyaromatic groups (Scheme 1 and Table 1). We
extended our investigation to the microwave-activated synthesis
of 6-(indol-3-yl)-2,20-bipyridine derivatives. The yield of the prod-
uct was good and isolation was similar to that of conventional
method. The results are summarized in Table 1.
of the compound was confirmed by single-crystal X-ray diffraction
analysis.26 (Fig. 1)
Whereas from all aldehydes 1a–j the pyridylpyridines 4a–j
were obtained directly under the reaction conditions (especially,
admission of air), only from 2,4-dichlorobenzaldehyde 1k the Han-
tzsch 1,4-dihydropyridine 5 could be isolated (78% after conven-
tional heating, up to 81% after microwave activation) and had to
be separately dehydrogenated to 6 (Scheme 3).
The structure of the Hantzsch 1, 4-dihydropyridine (5) was
investigated with spectral studies, elemental analysis and single-
crystal X-ray diffraction25,27 (Fig. 2).
Urea nitrate (20 mol %) was used for the dehydrogenation of 5
Based on the above results, a tentative mechanistic interpreta-
tion to explain the formation of 6-(indol-3-yl)-2,20-bipyridine
derivatives (Scheme 2) is proposed. Initially, aryl aldehyde 1 reacts
with 3-(cyanoacetyl)indole 3 to form the unsaturated ketone 3a,
which in turn adds 2-acetylpyridine (2, in its enol form 20) to give
compound 3b/3b0. The latter reacts with ammonium acetate to
form an intermediate 3c/3c0, which by elimination of water gives
the Hantzsch 1,4-dihydropyridine 3d. Under the reaction condi-
tions the latter undergoes ready dehydrogenation to the aroma-
tized pyridine derivative 4.
The structures of products 4a–j were confirmed by spectral
studies and elemental analysis as exemplified for compound 4h
as follows: The IR spectrum of 4h showed absorptions at 2217
and 3332 cmꢀ1 for CN and the indolic NH, respectively. The latter
group (D2O-exchangable) is also represented as a broad signal at
d 11.84 in the 1H NMR, which also shows the aryl proton signals
in the range d 7.21–8.71. The signal at d 103.1 in the 13C NMR con-
firms the presence of the cyano group, while all aryl C atoms gave
rise to signals in the range of d 112.6–157.8. The mass spectrum
displayed the (M++H+) peak at m/z 451.27.25 Further the structure
in acetonitrile to give an 86% yield of
6 under microwave
irradiation.28
The structure of 6 was supported by the NH and CN stretching
frequencies at 3312 and 2239 cmꢀ1, respectively. The aryl protons
gave rise to signals in the range d 7.23–8.72 ppm, and a broad sig-
nal at d 11.89 confirmed the presence of the D2O-exchangable
indolyl NH. The 13C NMR showed the CN carbon at d. 104.4 and
the aryl C-atoms at d 112.7–157.9 and at m/z = 441 the (M+H)+
ion was observed.
We extended our protocol to the synthesis of phenylene-1,4-
di[6-(1H-indol-3-yl)-2,20-bipyridine-5,50-dicarbonitrile]
deriva-
tives under optimized conditions. Many bis(bipyridiyl) ligands
are capable of forming multi-nuclear complexes. These chelating
ligands show particularly high affinities for transition metal ions
that frequently stabilize unusually low oxidation state species be-
cause of both dp
*–pp* back-bonding by the cations and their
capacity to form ligated anion radicals.29 Terephthaldialdehyde
(0.5 mmol), 3-(cyanoacetyl)indole (1.0 mmol) and 2-acetyl pyri-
dine (1.0 mmol) reacted under optimized conditions to give 68%
of product 8.(Scheme 4)
Table 1
Synthesis of 6-(indol-3-yl)-2,20-bipyridine derivatives 4a–j
Entry
Aldehyde (1)
R1
R2
R3
Product (4)a
Conventional heating
Time (h)
Yieldb (%)
Microwave irradiation
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
1g
1h
1i
H
H
H
H
H
H
CH3
H
OCH3
H
CH3
H
OCH3
OCH3
H
Cl
Br
F
H
4a
4b
4c
4d
4e
4f
4g
4h
4i
6.5
6.0
6.0
5.5
5.5
6.5
6.5
6.5
6.5
6.5
86
87
81
‘88
89
87
80
79
78
76
17
14
15
14
13
18
16
17
16
17
88
88
82
90
91
90
81
82
79
77
H
Phenyl
H
H
H
H
H
H
H
NO2
10
1j
4j
a
The products were characterized by NMR, IR and mass and elemental analysis.
Isolated yield.
b

P. Thirumurugan, P. T. Perumal / Tetrahedron Letters 50 (2009) 4145–4150
4147
CN
R1
CHO
R3
O
R1
R2
R2
R3
O
-H2O
+
CN
N
H
N
H
-
1
3a
3
O
N
N
O
2'
2
R3
R3
R2
R2
R1
R1
NH4OAc
CN
CN
HO
O
O
O
N
N
N
H
N
H
3b
3b'
R3
R3
R2
R1
R2
R1
CN
CN
HO
NH2
O
NH2
N
N
N
H
N
H
3c'
3c
R3
R3
R2
R1
R2
R1
-2H
H
-H2O
CN
CN
N
N
N
N
H
N
N
H
H
3d
4
Scheme 2. A plausible rationale of the reaction.
The structure of 1,4-di[6-(1H-indol-3-yl)-2,20-bipyridine-5,50-
dicarbonitrile] derivative (8) was characterized on the basis of ele-
mental analysis and spectral studies. The IR spectrum of compound
8 showed strong absorption band at 2210 cmꢀ1 and 3224 cmꢀ1 for
cyano and indolic NH functional groups. The indolic NH character-
istic peak appeared as a broad singlet (D2O-exchangeable) at d
11.88 in 1H NMR spectrum and the aromatic ring protons were res-
onated in the region of d 7.23–8.80. A distinguishing peak at d
102.6 in the 13C NMR spectrum confirmed the presence of cyano
carbon and the aromatic carbons were seen in the region of d
111.8–157.3. The mass spectrum displayed the [M++H+] peak at
m/z 667.40.
Encouraged by the above results and due to the unique supra-
molecular properties of oligopyridine derivatives, we extended
the protocol to the synthesis of 6,60-di(1H-indol-3-yl)-4,40-diaryl-
2,20-bipyridine-5,50-dicarbonitriles under optimized conditions.
1,6-Diarylhexa-l,5-diene-3,4 dione (cinnamil) is
a
versatile
precursor for the synthesis of oligopyridines. Oligopyridines are

4148
P. Thirumurugan, P. T. Perumal / Tetrahedron Letters 50 (2009) 4145–4150
Figure 1. Ortep diagram of compound 4h.
Figure 2. Ortep diagram of compound 5.
extremely versatile ligands for the assembly of metallosupramo-
lecular systems.30 1,6-Diarylhexa-1,5-diene-3,4-diones (cinnamils)
9a–e,30 3-(cyanoacetyl)indole (3) and ammonium acetate reacted
under optimized conditions to give 2,20-bi[6-(indol-3-yl)pyridines]
10a–e. (Scheme 5 and Table 2).
The structures of compounds (10a–e) were evaluated based on
detailed spectroscopic studies as exemplified for compound 10d as
follows: IR spectrum showed absorption peaks in the region of
2392 and 3416 cmꢀ1 indicating the presence of C„N and NH func-
tional groups, respectively. The 1H NMR spectrum showed aro-
matic protons in the region of d. 7.15–8.44. The NH proton was
demonstrated at d 11.87 (br s, D2O-exchangeable) and methoxy
protons appeared at d 3.85 as a sharp singlet. In 13C NMR spectra
all the aromatic carbons appeared in the region of d 112.6–161.4
and the distinguishable cyano carbon resonated at d 103.7. The
mass spectra displayed the [M++H+] peak at m/z 649.47.31
In summary, we have demonstrated a simple, facile and eco-
friendly method for the synthesis of 6-(indol-3-yl)-2,20-bipyridine
derivatives through multi-component reaction. The 3-indolyl oli-
gopyridines are versatile ligands in the field of coordination chem-
istry and supramolecular chemistry. 6-(indol-3-yl)-2,20-bipyridine
derivatives may have enhanced biological activities. Further stud-
ies to delineate the scope and limitations of the present methodol-
ogy are underway.
Cl
Cl
CN
CHO
Cl
N
Cl
N
Cl
O
NC
NH4OAc
NC
(O)
+
+
Urea
Nitrate
N
H
Neat, 120 ºC
(OR) MW
irradiation
N
N
H
N
O
Cl
N
N
H
H
1k
2
3
5
6
Scheme 3. Intermediacy of the dihydropyridine derivative 5.

P. Thirumurugan, P. T. Perumal / Tetrahedron Letters 50 (2009) 4145–4150
4149
H
N
N
N
CN
CN
CN
CHO
O
NH4OAc
+
+
Neat, 120oC
CH3
N
H
N
O
CHO
7
2
3
N
N
N
H
8
Scheme 4. Synthesis of phenylene-1,4-di[6-(1H-indol-3-yl)-2,20-bipyridine-5,50-dicarbonitriles].
R2
R2
R1
R1
CN
NH
NH
CN
O
N
O
O
NH4OAc
Neat, 120 ºC
+
N
H
N
CN
R1
R1
R2
R2
9a-e
10a-e
3
Scheme 5. Synthesis of 6,60-di(1H-indol-3-yl)-4,40-diaryl-2,20-bipyridine-5,50-dicarbonitrile derivatives 10a–e.
Synthesis 2003, 1471; (d) Weber, L.; Illgen, K.; Almstetter, M. Synlett 1999, 366;
(e) Evans, B. E. et al J. Med. Chem. 1988, 31, 2235.
2. Huang, Y. J.; Yang, F. Y.; Zhu, C. J. J. Am. Chem. Soc. 2005, 127, 16386.
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899.
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6. (a) Boger, D. L.; Nakahara, S. J. Org. Chem. 1991, 56, 880; (b) Boger, D. L.; Kasper,
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Table 2
Synthesis of 6,60-di(1H-indol-3-yl)-4,40-diaryl-2,20-bipyridine-5,50-dicarbonitrile
derivatives 10a–e
Entry
R1
R2
Product (10)a
Time (h)
Yieldb (%)
1
2
3
4
5
H
CH3
H
OCH3
OCH3
H
H
CH3
H
OCH3
10a
10b
10c
10d
10e
12.0
11.0
12.0
10.0
11.0
65
66
62
68
70
a
The products were characterized by NMR, IR and mass and elemental analysis.
Isolated yield.
b
9. (a) Cooke, M. W.; Hanan, G. S. Chem. Soc. Rev. 2007, 36, 1466; (b) Constable, E. C.
Chem. Soc. Rev. 2007, 36, 246; (c) Medlycott, E. A.; Hanan, G. S. Chem. Soc. Rev.
2005, 34, 133.
10. (a) Lehn, J. M. Supramolecular Chemistry, Concepts and Perspectives; VCH:
Weinheim, 1995; (b) Kaes, C.; Katz, A.; Hosseini, M. W. Chem. Rev. 2000, 100,
3553; (c) Gribble, G. W. J. Chem. Soc., Perkin Trans. 1 2000, 1045.
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12. Franco, L. H.; Joffe, E. B. K.; Puricelly, L.; Tatian, M.; Seldes, A. M.; Palermo, J. A. J.
Nat. Prod. 1998, 61, 1130.
13. Zhu, S. L.; Ji a, S. J.; Zhao a, K.; Liu a, Y. Tetrahedron Lett. 2008, 49, 2578.
14. Zhu, S. L.; Ji a, S. J.; Su a, X. M.; Sun a, C.; Liu a, Y. Tetrahedron Lett. 2008, 49,
1777.
Acknowledgement
One of the authors, P.T., thanks the Council of Scientific and
Industrial Research, New Delhi, India, for the research fellowship.
15. Farghaly, A. M.; Habib, N. S.; Khalil, M. A.; El-Sayed, O. A.; Alexandria J. Pharm.
Sci. 1989, 3, 90.
Supplementary data
16. (a) Tietze, L. F. Chem. Rev. 1996, 96, 115; (b) Domling, A. Chem. Rev. 2006, 106,
17.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2009.04.121.
17. Marchalin, S.; Kuthan, J. Czech. Chem. Commun. 1985, 50, 1862.
18. Radwana, M. A. A.; El-Sherbiny, M. Bioorg. Med. Chem. 2007, 15, 1206.
19. (a) Sun, C.; Jun Ji, S.; Liu, Y. Tetrahedron Lett. 2007, 48, 8987; (b) Radwan, M. A.
A.; Ragab, E. A.; Sabrya, N. M.; El-Shenawyc, S. M. Bioorg. Med. Chem. 2007, 15,
3832.
References and notes
1. (a) Cui, S. L.; Lin, X. F.; Wang, Y. G. J. Org. Chem. 2005, 70, 2866; (b) Ramo´n, D. J.;
Miguel, Y. Angew. Chem., Int. Ed. 2005, 44, 1602; (c) Orru, R. V. A.; de Greef, M.
20. Abdallah, T. A. J. Heterocycl. Chem. 2007, 44, 961.
21. Zaki, M. E. A.; Proenc, M. F. Tetrahedron 2007, 63, 3745.

4150
P. Thirumurugan, P. T. Perumal / Tetrahedron Letters 50 (2009) 4145–4150
22. Sridharan, V.; Perumal, P. T.; Avendano, C.; Menendez, J. C. Tetrahedron 2007,
63, 4407.
23. Thirumurugan, P.; Muralidharan, D.; Perumal, P. T. Dyes Pigments 2009, 81, 245.
24. Slatt, J.; Romero, I.; Bergman, J. Synthesis 2004, 16, 2760.
dihydropyridyl aryl H), 7.14 (t, 1H, J = 7.6 Hz, aryl H), 7.19 (t, 1H, J = 7.6 Hz, aryl
H), 7.34–7.37 (m, 1H, aryl H), 7.48–7.52 (m, 2H, aryl H), 7.56 (d, 1H, J = 8.4 Hz,
aryl H), 7.63 (d, 1H, J = 2.3 Hz), 7.72 (d, 1H, J = 7.6 Hz, aryl H), 7.80–7.83 (m, 1H,
aryl H), 7.87 (d, 1H, J = 8.4 Hz, aryl H), 7.95 (d, 1H, J = 3.1 Hz, aryl H), 8.54 (d,
1H, J = 4.6 Hz, aryl H), 8.64 (br s, 1H, NH), 11.83 (br s, 1H, –NH); 13C NMR
(125 MHz, DMSO-d6): 74.5, 100.6, 107.8, 112.5, 119.2, 119.3, 120.4, 121.6,
122.2, 123.7, 124.6, 127.6, 128.3, 128.9, 132.0, 132.4, 133.5, 136.2, 137.3, 141.6,
146.2, 148.4, 149.4; MS (EI): m/z 443.32 [M++H+]; Anal. Calcd for C25H16Cl2N4:
C, 67.73; H, 3.64; N, 12.64. Found: C, 67.89; H, 3.62; N, 12.60.
25. Typical experimental procedure for 4h and 5a: Method I:
A
mixture of
dichloro-
3-(cyanoacetyl)indole (1 mmol), 4-bromobenzaldehyde or 2,
4
benzaldehyde (1 mmol) and 2-acetyl pyridine (1 mmol) in 5 g of ammonium
acetate under neat condition was refluxed at 120 °C for 6–8 h in atmospheric
condition. After the completion of the reaction (as monitored by TLC), it was
poured into water and extracted with ethyl acetate. The organic layer was
dried over sodium sulfate and concentrated under vacuo. The crude product
was chromatographed in silica gel with ethyl acetate and petroleum ether
26. Ramesh, P.; Subbiahpandi, A.; Thirumurugan, P.; Perumal, P. T.; Ponnuswamy,
M. N. Acta Crystallogr., Sect. E 2009, 65, o450.
27. Ramesh, P.; Subbiahpandi, A.; Thirumurugan, P.; Perumal, P. T.; Ponnuswamy,
M. N. Acta Crystallogr., Sect. E 2008, 64, o1891.
mixture. Method II:
A mixture of 3-(cyanoacetyl)indole (1 mmol), 4-
bromoaldehyde or 2,4-dichlorobenzaldehyde (1 mmol) and 2-acetyl pyridine
(1 mmol) in 5 g of ammonium acetate in a sealed tube was kept in microwave
oven (BPL BMG 800 TS model) irradiated at 150 W at pulse rate 30 s for 16–
18 min under neat condition. The product isolation was similar to that of
conventional method. Spectral data for compound 4h: 6-(1H-Indol-3-yl)-4-(4-
bromophenyl)-2,20-bipyridine-5-carbonitrile (Table 2, entry 8) Pale Yellow solid;
mp 298–300 °C; Rf 0.33 (20% AcOEt/petroleum ether); IR (KBr): 1010, 1140,
28. Anniyappan, M.; Muralidharan, D.; Perumal, P. T. Tetrahedron 2002, 58, 5069.
29. Kelly, T. R.; Lebedev, R. L. J. Org. Chem. 2002, 67, 2197.
30. Constable, E. C.; Harverson, P.; Smlth, D. F.; Whall, L. A. Tetrahedron 1994, 50,
7799.
31. Experimental procedure for compound 10d: A mixture of 3-(cyanoacetyl)indole
(2 mmol), 1,6-bis(4-methoxyphenyl)hexa-1,5-diene-3,4-dione (1 mmol) and
5 g of ammonium acetate under neat condition was refluxed at 120 °C for 10 h.
After the completion of the reaction (as monitored by TLC), it was poured into
water and then filtered, washed with ethanol and then dried. The crude solid
obtained was purified further by recrystallisation with DMF and isolated yield
1212, 1435, 1535, 2217, 3332 cmꢀ1 1H NMR (500 MHz, DMSO-d6): d 7.21–7.24
;
(m, 2H, aryl H), 7.52–7.54 (m, 2H, aryl H), 7.67 (d, 2H, J = 8.4 Hz, aryl H), 7.74 (d,
2H, J = 8.4 Hz, aryl H), 8.02 (t, 1H, J = 8.4 Hz, aryl H), 8.21 (s, 1H, aryl H), 8.34–
8.37 (m, 2H, aryl H), 8.50 (d, 1H, J = 8.4 Hz, aryl H), 8.71 (d, 1H, J = 4.56 Hz, aryl
H), 11.84 (br s, 1H, –NH); 13C NMR (125 MHz, DMSO-d6): 103.1, 112.6, 113.2,
116.5, 119.0, 121.4, 121.7, 122.0, 122.9, 124.0, 125.8, 126.5, 129.3, 131.3, 132.3,
136.4, 136.9, 138.2, 150.1, 154.2, 154.3, 157.7, 157.8; MS (EI): m/z 451.27
[M++H+]; Anal. Calcd for C25H15Br N4: C, 66.53; H, 3.35; N, 12.41. Found: C,
66.43; H, 3.36; N, 12.46. Spectral data for compound 5: 4-(2,4-Dichlorophenyl)-
6-(1H-indol-3-yl)-1,4-dihydro-2,20-bipyridine-5-carbonitrile Yellow solid; mp
212–214 °C; Rf 0.23 (20% AcOEt/petroleum ether); IR (KBr): 1046, 1100,
was
68%.
6,60-Bis-(1H-indol-3-yl)-4-40-di-4-methoxyphenyl2,20bipyridinyl-
5,50dicarbonitrile (Table 2, entry 4) Yellow solid; mp >350 °C; Rf 0.15 (20%
AcOEt/petroleum ether); IR (KBr): 1027, 1251, 1428, 1529, 1609, 2392,
3416 cmꢀ1 1H NMR (500 MHz, DMSO-d6): d 3.85 (s, 6H, aryl-OCH3), 7.15–
;
7.24 (m, 8H, aryl H), 7.52 (d, 2H, J = 8.4 Hz, aryl H), 7.79 (d, 4H, J = 8.4 Hz), 8.40–
8.44 (m, 6H, aryl H), 11.87 (br s, 2H, –NH); 13C NMR (125 MHz, DMSO-d6): 56.0,
103.7, 112.6, 113.5, 115.0, 117.8, 119.1, 121.1, 121.9, 122.9, 126.7, 129.3, 129.5,
130.6, 137.1, 155.5, 156.5, 158.1, 161.4; MS (EI): m/z 649.47 [M++H+]; Anal.
Calcd for C42H28N6O2: C, 77.76; H, 4.35; N, 12.95. Found: C, 77.65; H, 4.36; N,
13.00.
;
1432, 1432, 1465, 1561, 1593, 2188, 3385 cmꢀ1 1H NMR (500 MHz, DMSO-
d6): d 5.06 (d, 1H, J = 5.35 Hz, dihydropyridyl aryl H), 5.83 (d, 1H, J = 5.35 Hz,