Design and synthesis of novel 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives, and their evaluation of topoisomerase inhibitory activity and cytotoxicity

Article abstract of DOI:10.1016/j.bmc.2014.11.010

For the development of potential anticancer agents, we designed and synthesized 30 new 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives containing aryl moiety such as furyl, thienyl, pyridyl, and phenyl at 2- and 4-position of 5H-indeno[1,2-b]pyridine. The

Full text of DOI:10.1016/j.bmc.2014.11.010

Accepted Manuscript
Design and synthesis of novel 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives,
and their evaluation of topoisomerase inhibitory activity and cytotoxicity
Tara Man Kadayat, Chanmi Park, Kyu-Yeon Jun, Til Bahadur Thapa Magar,
Ganesh Bist, Han Young Yoo, Youngjoo Kwon, Eung-Seok Lee
PII:
S0968-0896(14)00784-6
DOI:
http://dx.doi.org/10.1016/j.bmc.2014.11.010
BMC 11899
Reference:
To appear in:
Bioorganic & Medicinal Chemistry
Received Date:
Revised Date:
Accepted Date:
8 October 2014
5 November 2014
6 November 2014
Please cite this article as: Kadayat, T.M., Park, C., Jun, K-Y., Magar, T.B.T., Bist, G., Yoo, H.Y., Kwon, Y., Lee,
E-S., Design and synthesis of novel 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives, and their evaluation of
topoisomerase inhibitory activity and cytotoxicity, Bioorganic & Medicinal Chemistry (2014), doi: http://dx.doi.org/
1
0.1016/j.bmc.2014.11.010
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‘REVISED’
Design and synthesis of novel 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives, and their
evaluation of topoisomerase inhibitory activity and cytotoxicity
a,#
b,#
b
a
Tara Man Kadayat, Chanmi Park, Kyu-Yeon Jun, Til Bahadur Thapa Magar, Ganesh
a
a
b,*
a,*
Bist, Han Young Yoo, Youngjoo Kwon, Eung-Seok Lee
a
College of Pharmacy, Yeungnam University, Gyeongsan 712-749, Republic of Korea
b
College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Global Top5
program, Ewha Womans University, Seoul 120-750, Republic of Korea
#
Authors are equal contributors
*Corresponding Authors:
Tel: +82 2 3277-4653, fax: +82 2 3277-2851, email: ykwon@ewha.ac.kr (Y.K.)
Tel: +82 53 810-2827, fax: +82 53 810-4654, email: eslee@ynu.ac.kr (E.-S.L.)
1

Design and synthesis of novel 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives, and their
evaluation of topoisomerase inhibitory activity and cytotoxicity
a,#
b,#
b
a
Tara Man Kadayat, Chanmi Park, Kyu-Yeon Jun, Til Bahadur Thapa Magar, Ganesh
a
a
b,*
a,*
Bist, Han Young Yoo, Youngjoo Kwon, Eung-Seok Lee
a
College of Pharmacy, Yeungnam University, Gyeongsan 712-749, Republic of Korea
b
College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Global Top5
program, Ewha Womans University, Seoul 120-750, Republic of Korea
Abstract
For the development of potential anticancer agents, we designed and synthesized 30 new 2,4-
diaryl-5H-indeno[1,2-b]pyridine derivatives containing aryl moiety such as furyl, thienyl,
pyridyl, and phenyl at 2- and 4-position of 5H-indeno[1,2-b]pyridine. They were evaluated
for topoisomerase I and II inhibitory activity, and cytotoxicity against several human cancer
cell lines. Among prepared 30 compounds, 7, 8, 9, 10, 12, 14, 16, 19, 20, 22, and 23 with 2-
or 3-furyl and/or 2- or 3-thienyl either at 2- or 4-position of central pyridine showed the
significant or moderate topoisomerase II inhibitory activity. Compounds 7, 8, 11, 12, 13, and
2
2 with 2-furyl, 2- thienyl or 3-thienyl at 2-position of central pyridine showed the significant
or moderate topoisomerase I inhibitory activity. Especially, compound 12 with strong
topoisomerase II inhibitory activity at 100 µM and 20 µM, and moderate topoisomerase I
inhibitory activity displayed strong cytotoxicity against several human cancer cell lines.
Keywords: 2,4-Diaryl-5H-indeno[1,2-b]pyridine; Topoisomerase I and II inhibition;
Cytotoxicity; Anticancer agents
2

1. Introduction
Human DNA topoisomerases (topo) have been established as one of the most important
1
molecular targets for the development of anticancer agents. These are nuclear enzymes that
transiently break one or two strands of DNA allowing to solve various DNA topological
problems associated with DNA replication, transcription, recombination, and other vital
2
cellular processes. Depending on their mechanism of action, making either single or double-
stranded breaks, DNA topoisomerases are generally classified into two categories, topo I and
3
topo II. In the course of several years of its discovery, topoisomerase inhibitors such as
etoposide, teniposide, and camptothecin have been clinically used for treatment of cancer.
However, due to their severe side effects many researchers in medicinal chemistry are attracted
to develop a new class of topoisomerase inhibitors that possess less side effects and greater
1
,4
potency. With the similar goal, our research group has been studying various flexible
terpyridine derivatives and evaluated for topo I and/or II inhibitory activity, and cytotoxicity
5
,6
against several human cancer cell lines. Previously reported study has revealed that the
number of aryl groups in terpyridine derivatives is important for determining the anticancer
5
e
activity.
Moreover, our group has reported that conformationally constrained rigid analogs of 2,4,6-
trisubstituted pyridine [Fig. 1a] containing 5,6-dihydrobenzo[h]quinolone, 5H-chromeno[4,3-
b]pyridine,
5,6-dihydro[1,10]phenanthroline,
5,6-dihydrothieno[2,3-h]quinolone,
and
benzofuro[3,2-b]pyridines, which showed considerable topo I and II inhibitory activities, and
7
cytotoxicity against several human cancer cell lines. It is well documented that rigidification
of the flexible ring provides planar configuration to compound which facilitates molecule to
8
intercalate into the enzyme-DNA complex. In addition, as compared to flexible structures,
3

rigid structures have little conformational entropy, and can be more efficiently fitted into the
9
active site of enzyme. In continuation of latter work, herein we have designed and synthesized
2,4-diaryl-5H-indeno[1,2-b]pyridines as conformationally constrained rigid molecule in
terpyridine skeleton (Fig. 1b). Furthermore, it is reported that compounds possessing
indenopyridine moiety have several biological activities such as anticancer and anti-
1
0
inflammatory activity.
Based on reported biological activities, in this study, we designed and synthesized 30 novel
rigid analogs of 2,4-diaryl-5H-indeno[1,2-b]pyridines employing 7 aryl groups such as 2- or 3-
furyl, 2- or 3-thienyl, 2- or 3-pyridyl, and phenyl attached to the central pyridine ring at 2- and
4
-position as shown in Figure 1. Our work represents the first systematic study of the 2,4-
diaryl-5H-indeno[1,2-b]pyridines for evaluation of human topo I and II inhibitory activity, and
cytotoxicity.
(
Figure 1)
2
2
2
. Results and discussion
. 1. Synthetic chemistry
,4-Diaryl-5H-indeno[1,2-b]pyridine derivatives (7-36) were synthesized in three steps
11,12
(
Scheme 1), based on the previously reported methods.
In the first step, pyridinium
iodides salts 2 (R = c-g) were synthesized by the reaction of appropriate aryl methyl ketones
1
(R = c-g) with equivalent amount of iodine in pyridine for 3 h at 140 °C. Compounds 2 (R
1
=
c-g) were obtained in 38.4-98.3% yield. Secondly, 1-indanone intermediates 5 (R = a-f)
11
were prepared using the Clasien-Schmidt condensation reaction, where 1-indanone (3) was
4

1
reacted with aryl aldehydes 4 (R = a-f) in the presence of EtOH and 5% aqueous NaOH.
1
Total 6 1-indanone intermediates 5 (R = a-f) were synthesized in 90.1-95.8% yield. Finally,
1
2
using modified Krönke pyridine synthesis method, pyridinium iodide salts 2 (R = c-g) and
1
1
-indanone intermediates 5 (R = a-f) were reacted in the presence of NH
4
OAc and glacial
acetic acid for 16-24 h at 100 °C to yield 23.5-53.3% of 2,4-diaryl-5H-indeno[1,2-b]pyridines
(
(
7-36). Synthesized 30 compounds compounds are as shown in Figure 2. Yield (%), purity
%) by HPLC, and melting point of the compounds are shown in Table 1.
(
(
(
Scheme 1)
Figure 2)
Table 1)
2
. 2. Topoisomerase I and II inhibitory activity
We evaluated the conversion of supercoiled plasmid DNA to relaxed DNA by topo I and II in
the presence of the prepared 2,4-diaryl-5H-indeno[1,2-b]pyridines (7-30) as shown in Fig. 3
and 4, and Table 2. From the preliminary study, compounds 31-36 did not show significant
topo I and II inhibitory activities. Camptothecin and etoposide, well-known topo I and II
inhibitors, respectively, were used as positive controls. Inhibitory activities were evaluated
both at 100 µM and 20 µM.
2
.2.1. Topoisomerase I inhibitory activity
Most of compounds did not show significant topo I inhibitory activity as shown in Figure 3
and Table 2. However, compounds 22 and 13 have shown significant topo I inhibitory activity
5

of 90.9% and 76.3%, respectively, which were stronger inhibitory activity than that of
camptothecin (62.9%, 45.2%, respectively) at 100 µM. Compounds 7, 8, 11, 12, and 27
displayed moderate topo I inhibitory activity of 38.2%, 52.5%, 41.3%, 40.7%, and 58.5% (as
compared to 45.2% or 62.9% of camptothecin), respectively, at 100 µM. Topo I inhibitory
activities of evaluated compounds are summarized in Table 2.
(
(
Table 2)
Figure 3)
2
.2.2. Topoisomerase II inhibitory activity
It was observed that compounds 9, 10, 12, 14, and 19 displayed significant topo II inhibitory
activity of 83.9%, 100%, 100%, 100%, and 84.1%, respectively, at 100 µM, and 79.6%,
9
3.0%, 100%, 66.7%, and 68.5%, respectively, at 20 µM, which were stronger inhibitory
activity than that of positive control, etoposide, at both 100 µM and 20 µM concentrations as
shown in Figure 4. Especially, compound 12 displayed the most strong topo II inhibitory
activity as well as moderate topo I inhibitory activity. Compounds 8, 16, and 22 displayed
1
00% topo II inhibition as compared to 87.8% of etoposide at 100 µM concentration, while
compounds 7 and 13 exhibited significant topo II inhibitory activity of 44.6% and 40.5%,
respectively as compared to 32.4% of etoposide at 100 µM. Compound 20 displayed potent
topo II inhibitory activity of 95.9% as compared to 83.7% of etoposide at 100 µM.
Compounds 17 and 23 exhibited considerable topo II inhibitory activity, although weaker
than that of etoposide. Table 2 summarizes the topo II inhibitory activities of evaluated
compounds both at 100 and 20 µM.
6

(
Figure 4)
Figure 5 shows structures of previously synthesized representative rigid analogs of 2,4,6-
triarylsubstituted pyridines, and table 3 exhibits relative potencies of the representative
compounds including 2,4-diaryl-5H-indeno[1,2-b]pyridines at 100 µM compared to positive
controls, camptothecin (topo I) and/or etoposide (topo II) for easier comparison with
previously synthesized rigid analogs of 2,4,6-triarylsubstituted pyridines and 2,4-diaryl-5H-
indeno[1,2-b]pyridines. Generally, relative potencies of 2,4-diaryl-5H-indeno[1,2-b]pyridines
against etoposide (topo II) is much greater than those of previously synthesized representative
rigid analogs of 2,4,6-triarylsubstituted pyridines.
(
(
Figure 5)
Table 3)
2
. 3. Cytotoxicity
Compounds 7-30 were evaluated for cytotoxicity against four different human cancer cell
lines: human breast adenocarcinoma cell line (MCF-7), human cervix tumor cell line (HeLa),
human colorectal adenocarcinoma cell line (HCT15), human prostate tumor cell line
(
DU145). The inhibitory activity (IC50) is expressed as micromolar concentration as shown in
Table 2. Compounds 7, 11-13, and 27 showed considerable cytotoxicity against tested cell
lines. Compound 7 possessing moderate topo I and II inhibitory activity showed moderate
cytotoxicity against MCF-7 and HeLa. Compounds 11 and 27, and 13 possessing moderate
and strong topo I inhibitory activity, respectively, displayed considerable (the same or a little
7

weaker) cytotoxicity against tested cell lines compared to positive controls. In addition,
Compounds 12 possessing strong topo II and moderate topo I inhibitory activity, displayed
the strongest cytotoxicity against tested cell lines. It is interesting to note that compounds 8-
1
0, 14, 16, 19, 20, 22, and 23 which have displayed strong to moderate topo I and/or II
inhibitory activities did not show considerable cytotoxicity. It is common in biological study
6
e
in vitro that cytotoxicity did not correlate directly to topoisomerase inhibitory activity.
2
.4. Structure-activity relationship study (SAR)
Structure-activity relationship study was performed according to the results of topo I and II
inhibitory activity of the evaluated compounds. From the prepared compounds not many
compounds showed strong topo I and II inhibitory activities at both 100 µM and 20 µM
concentrations, it is not facile to be determined to concrete structure-activity relationship.
However, compounds 7-12 which shares the common 2-(furan-2-yl)-5H-indeno[1,2-
b]pyridine skeleton possess moderate to strong topo II inhibitory activity. Similarly,
compounds 13, 14, and 16, and compounds 19, 20, and 22 with 2-thienyl and 3-thienyl
moiety at 2-position of the central pyridine, respectively, possess significant topo II inhibitory
5
b,d, 6a-d, 7b,f
activity. This results are similar to previous studies,
which supports importance of
2
-furyl, 2-thienyl or 3-thienyl moiety at 2-position and/or 4-position on central pyridine for
significant topo II inhibitory activity. In addition, compounds with 2-furyl (7, 13, 19) or 3-
furyl (8, 14, 20) at 4-position of the central pyridine also possess significant topo II inhibitory
activity. Interestingly, compounds 10, 16, and 22 which possess 3-thienyl at 4-position of the
central pyridine have 100% topo II inhibitory activity at 100 µM concentration (Fig. 5). In
contrast, except compound 12 and 27, all the compounds bearing pyridyl or phenyl moiety at
2- or 4-position did not show any significant topo inhibitory activity. This indicates that
8

introduction of furyl or thienyl moiety at 2- or 4-position of central pyridine is crucial than
pyridyl or phenyl moiety for topo II inhibitory activity.
Compounds 13 and 22 which showed strong topo I inhibitory activity and compounds 7, 8, 11,
1
2, and 27 which displayed moderate topo I inhibitory activity possess 2-furyl, 2-thienyl, or
3
-thienyl at 2-position of central pyridine. The results indicated that substitution of furyl or
thienyl at 2-position of central pyridine is important for topo I inhibitory activity.
(
Figure 6)
The concrete correlation between topo inhibitory activity and cytotoxicity was not observed
since many compounds showing strong or moderate topo I and/or topo II inhibitory activities
did not show significant cytotoxicity against tested cell lines. But compounds 7, 11-13, and
2
7 possessing significant cytotoxicity displayed strong to moderate topo I and/or topo II
inhibitory activities.
3
. Conclusion
We have designed and synthesized thirty 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives and
evaluated for their topo I and II inhibitory activity, and cytotoxicity against several human
cancer cell lines. SAR study indicated that furyl or thienyl moiety at 2- or 4-position of
central pyridine may play an important role for topoisomerase I and II inhibitory activity. In
addition, combination of 2-(furan-2-yl)-5H-indeno[1,2-b]pyridine skeleton with furyl, or
thienyl moiety rather than pyridyl or phenyl moiety at 2-position is more important for topo II
inhibitory activity. No direct correlation between cytotoxicity and topoisomerase inhibitory
9

activity was observed but compounds possessing significant cytotoxicity displayed strong to
moderate topo I and/or topo II inhibitory activities. This result may provide valuable
information to researchers in medicinal chemistry, and further study including optimization
may lead to develop novel topo inhibitor as anticancer drugs.
4
. Experimental
Compounds used as starting materials and reagents were obtained from Aldrich Chemical Co.,
Junsei or other chemical companies, and utilized without further purification. HPLC grade
acetonitrile (ACN) and methanol were purchased from Burdick and Jackson, USA. Thin-
layer chromatography (TLC) and column chromatography (CC) were performed with
Kieselgel 60 F254 (Merck) and silica gel (Kieselgel 60, 230-400 mesh, Merck) respectively.
Since all the compounds prepared contain aromatic ring, they were visualized and detected on
TLC plates with UV light (short wave, long wave or both). NMR spectra were recorded on a
1
13
Bruker AMX 250 (250 MHz, FT) for H NMR and 62.5 MHz for C NMR, and chemical
shifts were calibrated according to TMS. Chemical shifts (δ) were recorded in ppm and
coupling constants (J) in hertz (Hz). Melting points were determined in open capillary tubes
on electrothermal 1A 9100 digital melting point apparatus and were uncorrected.
HPLC analyses were performed using two Shimadzu LC-10AT pumps gradient-controlled
HPLC system equipped with Shimadzu system controller (SCL-10A VP) and photo diode
array detector (SPD-M10A VP) utilizing Shimadzu Class VP program. Sample volume of 10
®
μL, was run in Waters X- Terra 5 μM reverse-phase C18 column (4.6 ⅹ250 mm) with a
gradient elution of 75% to 100% of B in A for 10 min followed by 100% to 75% of B in A for
2
0 min at a flow rate of 1.0 mL/min at 254 nm UV detection, where mobile phase A was
1
0

doubly distilled water with 50 mM ammonium formate (AF) and B was 90% ACN in water
with 20 mM AF. Purity of compound is described as percent (%), and retention time is given
in minutes.
®
ESI LC/MS analyses were performed with a Finnigan LCQ Advantage LC/MS/MS
®
spectrometry utilizing Xcalibur program. For ESI LC/MS, LC was performed with 10 μL
®
injection volume on a Waters X Terra 3.5 μm reverse-phase C18 column (2.1ⅹ 100 mm)
with a gradient elution from 10% to 95% of B in A for 10 min followed by 95% to 10% of B
in A for 10 min at a flow rate of 200 μL/min, where mobile phase A was 100% distilled water
with 50 mM AF and mobile phase B was 100% ACN. MS ionization conditions were: Sheath
gas flow rate: 70 arb, aux gas flow rate: 20 arb, I spray voltage: 4.5 KV, capillary temp.:
2
15°C, capillary voltage: 21V, tube lens offset: 10 V.
4
. 1. General method for preparation of 2 (R = c-g)
Pyridinium iodide salts 2 (R = c-g) were synthesized by refluxing aryl methyl ketones 1 (R =
c-g) with equivalent amount of iodine in pyridine at 140 °C for 3 h. Precipitate occurred
during reaction was cooled to room temperature which was filtered and washed with cold
pyridine followed by drying overnight to yield 38.4-98.3% of 2 (R = c-g). Compounds were
used without further purification.
1
4
. 2. General method for preparation of 5 (R = a-f)
1
-Indanone (3) was added in ethanol followed by the addition of equivalent amount of aryl
1
aldehydes 4 (R = a-f). The 5% aqueous solution of NaOH was added drop wise to the
mixture at 0 °C which resulted in precipitation. The mixture was then cooled for 30 min,
1
1

filtered, washed with cold methanol, and dried to yield 90.1-95.8% solid compound. Total six
1
1
H-inden-1-one derivatives 5 (R = a-f) were synthesized following the same method.
4
.2.1. Synthesis of 2-benzylidene-2,3-dihydro-1H-inden-1-one (5a)
The procedure described in Section 4.2 was employed with 1-indanone (1.32 g, 10 mmol)
and benzaldehyde (1.01 mL) to yield 2.04g (92.9%) as a whitish yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:10) R
f
= 0.27, mp: 147.9-148.6 C , HPLC: Retention time:
+
1
2.76 min, purity: 95.1%; ESI LC/MS m/z calcd for C16
H
12O [MH] 221.10; found 221.20
1
H NMR (250 MHz, CDCl ) δ 7.9 (d, J = 7.6 Hz, 1H, indeno H-7), 7.7-7.6 (m, 3H, indeno
3
H-5, phenyl H-2, H-6), 7.6-7.5 ( m, 2H, indeno H-4, =CH-), 7.5-7.4 (m, 4H, phenyl H-3, H-4,
H-5, indeno H-6), 4.06 (s, 2H, indeno H-3).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 194.84, 150.06, 138.35, 135.74, 135.07, 134.36, 131.14,
1
30.10, 129.34, 128.08, 126.59, 124.83, 32.85.
4
.2.2. Synthesis of 2-(furan-3-ylmethylene)-2,3-dihydro-1H-inden-1-one (5b)
The procedure described in Section 4.2 was employed with 1-indanone (1.32 g, 10 mmol)
and 3-furaldehyde (0.83 mL) to yield 1.98 g (94.6%) as a whitish yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.2, mp: 139.6-141.1 C, HPLC: Retention time:
+
1
1.10 min, purity: 97.5%; ESI LC/MS m/z calcd for C14
H
10
O
2
[MH] 211.08; found 211.12
1
3
H NMR (250 MHz, CDCl ) δ 7.89 (d, J = 7.6 Hz, 1H, indeno H-7), 7.82 (s, 1H, =CH-),
7
.65-7.52 (m, 4H, indeno H-4, H-5, furan H-2, H-5), 7.4 (t, J = 7.27 Hz, 1H, indeno H-6), 6.7
(
d, J = 1.6 Hz, 1H, furan H-4), 3.89 (s, 2H, indeno H-3).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 193.87, 148.95, 145.77, 144.29 138.32, 134.47, 133.83,
1
27.57, 126.14, 124.21, 123.99, 122.41, 109.91, 31.89.
1
2

4
.2.3. Synthesis of 2-(furan-2-ylmethylene)-2,3-dihydro-1H-inden-1-one (5c)
The procedure described in Section 4.2 was employed with 1-indanone (1.32 g, 10 mmol)
and 2-furaldehyde (0.82 mL) to yield 1.89 g (90.1%) as a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.28, mp: 124.2-125.6 C, HPLC: Retention time:
+
1
1.62 min, purity: 97.8%; ESI LC/MS m/z calcd for C14
H
10
O
2
[MH] 211.08; found 211.14
1
H NMR (250 MHz, CDCl
3
) δ 7.88 (d, J = 7.64 Hz, 1H, indeno H-7), 7.63 (s, 1H, =CH-),
.61-7.53 (m, 2H, furan H-5, indeno H-5), 7.47-7.39 (m, 2H, indeno H-4, H-6), 6.77 (d, J =
.4 Hz, 1H, furan H-3), 6.56 (br, 1H, furan H-4), 4.05 (s, 2H, indeno H-3).
7
3
1
3
3
C NMR (62.5 MHz, CDCl ) δ 193.97, 152.27, 149.76, 145.35, 138.45, 134.42, 132.53,
1
27.44, 126.17, 124.20, 120.03, 116.61, 112.64, 32.32.
4
.2.4. Synthesis of 2-(thiophen-3-ylmethylene)-2,3-dihydro-1H-inden-1-one (5d)
The procedure described in Section 4.2 was employed with 1-indanone (1.32 g, 10 mmol)
and 3-thiophene carboxaldehyde (0.91 mL) to yield 2.1 g (95.8%) as a whitish brown solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
=0.3, mp: 147.9-148.6 C, HPLC: Retention time:
+
1
2.21 min, purity: 96.9%; ESI LC/MS m/z calcd for C14
H
10OS [MH] 227.05; found 227.12
1
H NMR (250 MHz, CDCl ) δ 7.88 (d, J = 7.6 Hz, 1H, indeno H-7), 7.70-7.66 (m, 2H,
3
thiophene H-2, H-5), 7.64 (dt, J = 7.8, 1.12 Hz, 1H, indeno H-5), 7.56 (d, J = 7.07 Hz, 1H,
indeno H-4), 7.44-7.38 (m, 3H, =CH-, indeno H-6, thiophene H-4), 3.96 (s, 2H, indeno H-3).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 194.25, 149.21, 138.45, 137.76, 134.49, 133.44, 129.46,
1
28.30, 127.65, 127.26, 126.60, 126.16, 124.32, 32.34.
4
.2.5. Synthesis of 2-(thiophen-2-ylmethylene)-2,3-dihydro-1H-inden-1-one (5e)
1
3

The procedure described in Section 4.2 was employed with 1-indanone (1.32 g, 10 mmol)
and 2-thiophene carboxaldehyde (0.93 mL) to yield 2.16 g (95.6%) as a white solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
=0.25, mp:172.2-173.1 C, HPLC: Retention time:
+
1
2.53 min, purity: 100%; ESI LC/MS m/z calcd for C14
H
10OS [MH] 227.05; found 227.13
1
3
H NMR (250 MHz, CDCl ) δ 7.90-7.88 (m, 2H, thiophene H-3, H-5), 7.62-7.55 (m, 3H,
indeno H-4, H-5, H-7), 7.45-7.42 (m, 2H, =CH-, indeno H-6), 7.17 (t, J = 4.97 Hz, 1H,
thiophene H-4), 3.93 (s, 2H, indeno H-3).
1
3
C NMR (62.5 MHz, CDCl ) δ 193.73, 149.03, 139.94, 138.57, 134.50, 133.01, 132.80,
3
1
30.44, 128.17, 127.64, 126.51, 126.21, 124.30, 32.34.
4
.2.6. Synthesis of -2-(pyridin-2-ylmethylene)-2,3-dihydro-1H-inden-1-one (5f)
The procedure described in Section 4.2 was employed with 1-Indanone (1.32 g, 10 mmol)
and 2-pyridine carboxaldehyde (0.95 mL) to yield 2.01 g (91.9%) as a white solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.18, mp: 152.8-155.3 C, HPLC: Retention time:
+
1
0.98 min, purity: 98.2%; ESI LC/MS m/z calcd for C15
H
11NO [MH] 222.09; found 222.21
1
H NMR (250 MHz, CDCl ) δ 8.74 (br, 1H, pyridine H-6), 7.89 (d, J = 7.62 Hz, 1H, indeno
3
H-7), 7.71 (dt , J = 7.05, 0.9 Hz, 1H, pyridine H-3) 7.62-7.57 (m, 3H, =CH-, indeno H-4, H-
), 7.51 (d, J = 7.92 Hz, 1H, pyridine H-4), 7.38 (t, J = 7.27 Hz, 1H, indeno H-6), 7.21-7.19
5
(
m, 1H, pyridine H-5), 4.28 (s, 2H, indeno H-3).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 194.89, 154.88, 151.24, 150.05, 139.11, 137.94, 136.35,
1
34.80, 130.94, 127.36, 127.35, 126.32, 124.37, 122.95, 33.37.
4
. 3. General method for preparation of 7-36
1
4

On the basis of Kröhnke synthesis method [24], 2,4-diaryl indenopyridine derivatives (7-36)
1
were synthesized by reacting previously synthesized 1-indanone derivatives 5 (R = a-f) and
pyridinium iodide salts 2 (R = c-g) in the presence of anhydrous ammonium acetate (10.0
equiv) and glacial acetic acid. The mixture was heated at 100 °C for 16-24 h. The reaction
mixture was then extracted with ethyl acetate, washed with water and saturated NaCl. The
organic layer was dried with magnesium sulfate and filtered. The filtrate was concentrated
under reduced pressure and dried in vacuum pump, which was then purified by silica gel
column chromatography with the gradient elution of ethyl acetate and n-hexane to afford
solid compounds 7-36 in 23.5-53.3% yield.
4
.3.1. Synthesis of 2,4-di(furan-2-yl)-5H-indeno[1,2-b]pyridine (7)
The compound was synthesized as described in section 4.3 with 5c (0.84 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2c (1.26 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 329 mg (27.5%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.4, mp : 136.5-140.9 C, HPLC: Retention time:
+
7
.94 min, purity: 100%; ESI LC/MS m/z calcd for C20
H13NO
2
[MH] 300.10; found 300.25
1
H NMR (250 MHz, CDCl
3
) δ 8.2 (dd, J = 6.4, 2.08 Hz, 1H, indenopyridine H-9), 7.94 (s,
1
7
3
1
H, indenopyridine H-3), 7.65-7.58 (m, 3H, 2-furan H-5, indenopyridine H-7, H-8), 7.48-
.44 (m, 2H, 4-furan H-5, indenopyridine H-6), 7.2 (d, J = 3.3 Hz, 2-furan H-3), 7.00 (d, J =
.46 Hz, 4-furan H-3), 6.61 (dd, J = 3.39, 1.7 Hz, 1H, 2-furan H-4), 6.58 (dd, J = 3.29, 1.7 Hz,
H, 4-furan H-4), 4.09 (s, 2H, indenopyridine H-5).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.48, 154.18, 151.44, 148.80 143.96, 143.64, 143.01,
1
3
40.58, 134.17, 129.09, 128.85, 127.13, 124.89, 121.32, 112.11, 112, 111.03, 110.70, 108.45,
5.63
1
5

4
.3.2. Synthesis of 2-(furan-2-yl)-4-(furan-3-yl)-5H-indeno[1,2-b]pyridine (8)
The compound was synthesized as described in section 4.3 with 5b (0.84 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2c (1.26 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 481 mg (40.2%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.4, mp : 176.4-178.2 C, HPLC: Retention time:
+
7
.80 min, purity: 98.1%; ESI LC/MS m/z calcd for C20
H13NO
2
[MH] 300.10; found 300.25
1
3
H NMR (250 MHz, CDCl ) δ 8.2 (d, J = 6.3 Hz, 1H, indenopyridine H-9), 8.01 (s,1H, 4-
furan H-2), 7.73 (s, 1H, indenopyridine H-3), 7.60-7.57 (m, 3H, 2-furan H-5, 4-furan H-5 and
indenopyridine H-8), 7.50-7.40 (m, 2H, indenopyridine H-6, H-7), 7.2 (dd, J = 3.31 Hz, 1H,
2
2
-furan H-3), 6.9 (s, 1H, 4-furan H-4), 6.5 (dd, J = 4.30, 1.74 Hz, 1H, 2-furan H-4), 3.96 (s,
H, indeno H-5).
1
3
C NMR (62.5 MHz, CDCl ) δ 161.23, 154.19, 148.94, 143.81 143.53, 142.98, 141.54,
3
1
1
40.76, 136.81, 131.25, 128.84, 127.25, 124.90, 123.71, 121.38, 113.79, 112.05, 109.18,
08.47, 35.42.
4
.3.3. Synthesis of 2-(furan-2-yl)-4-(thiophen-2-yl)-5H-indeno[1,2-b]pyridine (9)
The compound was synthesized as described in section 4.3 with 5e (0.226 g, 1 mmol), dry
ammonium acetate (0.77 g, 10 mmol), 2c (0.315 g, 1 mmol) with methanol (5 mL) to yield 96
mg (30.42%) of a white solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.39, mp : 141.6-142.9 C, HPLC: Retention time:
+
9
.42 min, purity: 96.7%; ESI LC/MS m/z calcd for C20
H
13NOS [MH] 316.08; found 316.25
1
H NMR (250 MHz, CDCl ) δ 8.22 (d, J = 8.17 Hz, 1H, indenopyridine H-9), 7.87 (s, 1H,
3
indenopyridine H-3), 7.69 (d, J = 3.67 Hz, 1H, 2-furan H-5), 7.63-7.58 (m, 1H, 4-thiophene
1
6

H-5), 7.54-7.42 (m, 4H, indenopyridine H-6, H-7, H-8, 4-thiophene H-3), 7.26-7.22 (m, 2H,
-thiophene H-4, 2-furan H-3), 6.60-6.58 (m, 1H, 2-furan H-4), 4.11 (s, 2H, indenopyridine
H-5).
4
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.62, 154.03, 148.90, 143.75, 143.07, 140.69, 140.61,
1
1
38.40, 130.62, 128.94, 128.01, 127.29, 127.23, 127.01, 124.89, 121.43, 113.69, 112.05,
08.59, 35.78.
4
.3.4. Synthesis of 2-(furan-2-yl)-4-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (10)
The compound was synthesized as described in section 4.3 with 5d (0.90 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2c (1.26 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 471 mg (37.2%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.5, mp : 146.6-148.2 C, purity: HPLC: Retention
+
time: 9.02 min, purity: 96.3%; ESI LC/MS m/z calcd for C20
H
13NOS [MH] 316.08; found
3
16.23
1
3
H NMR (250 MHz, CDCl ) δ 8.2 (dd, J = 7.38, 1.2 Hz, 1H, indenopyridine H-9), 7.79-7.76
(
m, 2H, indenopyridine H-3, 4-thiophene H-2), 7.59-7.56 (m, 3H, 4-thiophene H-4, H-5, 2-
furan H-5), 7.52-7.42 (m, 3H, indenopyridine H-6, H-7, H-8), 7.2 (d, J = 3.35 Hz, 1H, 2-
furan H-3), 6.5 (dd, J = 3.4, 1.7 Hz, 1H, 2-furan H-4), 4.05 (s, 2H, indenopyridine H-5).
1
3
C NMR (62.5 MHz, CDCl ) δ 161.36, 154.16, 148.97, 143.78 143.01, 140.72, 140.18,
3
1
1
39.13, 131.74, 128.81, 127.20, 127.13, 126.39, 124.87, 124.53, 121.40, 114.95, 112.04,
08.45, 35.32.
4
.3.5. Synthesis of 2-(furan-2-yl)-4-phenyl-5H-indeno[1,2-b]pyridine (11)
1
7

The compound was synthesized as described in section 4.3 with 5a (0.87 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2c (1.32 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 603 mg (48.6%) of a whitish yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.5, mp : 129.2-130.6 C, HPLC: Retention time:
+
9
.50 min, purity: 96.2%; ESI LC/MS m/z calcd for C22
H
15NO [MH] 310.12; found 310.28
1
H NMR (250 MHz, CDCl ) δ 8.2 (d, J = 6.7 Hz, 1H, indenopyridine H-9), 7.68-7.65 (m, 3H,
3
indenopyridine H-3, 4-phenyl H-2, H-6), 7.56-7.38 (m, 7H, 4-phenyl H-3, H-4, H-5,
indenopyridine H-6, H-7, H-8, 2-furan H-5), 7.2 (d, J = 3.3 Hz, 1H, 2-furan H-3), 6.5 (dd, J =
3
.3, 1.7 Hz, 1H, 2-furan H-4), 3.98 (s, 2H, indenopyridine H-5).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.03, 154.19, 148.99, 146.30 144.06, 143.04, 140.79,
1
1
38.59, 132.75, 128.81, 128.76, 128.57, 128.21, 127.14, 124.88, 121.46, 116.14, 112.01,
08.46, 34.50.
4
.3.6. Synthesis of 2-(furan-2-yl)-4-(pyridin-2-yl)-5H-indeno[1,2-b]pyridine (12)
The compound was synthesized as described in section 4.3 with 5f (0.88 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2c (1.26 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 454 mg (36.4%) of a whitish yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:2) R
f
= 0.46, mp : 138.1-140.7 C, HPLC: Retention time:
+
1
0.51 min, purity: 97.3%; ESI LC/MS m/z calcd for C21
H
14
N
2
O [MH] 311.12; found 311.31
1
3
H NMR (250 MHz, CDCl ) δ 8.8 (d, J = 4.67 Hz, 1H, 4-pyridine H-6), 8.2 ( dd, J = 7.17,
1
.57 Hz, 1H, indenopyridine H-9), 8 (s, 1H, indenopyridine H-3), 7.89-7.86 (m, 2H, 4-
pyridine H-5, H-4), 7.61-7.57 (m, 2H, 4-pyridine H-3, 2-furan H-5), 7.48-7.34 (m, 3H,
indenopyridine H-6, H-7, H-8), 7.2 (d, J = 3.73 Hz, 1H, 2-furan H-3), 6.5 (dd, J = 3.3, 1.7 Hz,
1
H, 2-furan H-4), 4.26 (s, 2H, indenopyridine H-5).
1
8

1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.11, 152.07, 145.34, 143.84, 143.52, 141.49, 140.71,
1
3
36.81, 131.29, 128.82, 127.91, 127.26, 124.88, 124.42, 123.62, 121.40, 114.16, 109.12,
5.37.
4
.3.7. Synthesis of 4-(furan-2-yl)-2-(thiophen-2-yl)-5H-indeno[1,2-b]pyridine (13)
The compound was synthesized as described in section 4.3 with 5c (0.84 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2e (1.32 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 360 mg (23.5%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.4, mp : 136.3-138.4 C, HPLC: Retention time:
+
1
1.24 min, purity: 98.4%; ESI LC/MS m/z calcd for C20
H
13NOS [MH] 316.08; found 316.27
1
3
H NMR (250 MHz, CDCl ) δ 8.18 (d, J = 6.9 Hz, 1H, indenopyridine H-9), 7.8 (s, 1H,
indenopyridine H-3), 7.7 (d, J = 3.6 Hz, 1H, 4-furan H-5), 7.6 (m, 2H, indenopyridine H-7, 2-
thiophene H-3), 7.48-7.40 (m, 3H, indenopyridine H-6, H-8, 2-thiophene H-5), 7.1 (dt, J =
3
.9, 0.8 Hz, 1H, 4-furan H-3), 7 (d, J = 3.3 Hz 1H, 2-thiophene H-4), 6.61-6-58 (m, 1H, 4-
furan H-4), 4 (s, 2H, indenopyridine H-5).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.32, 151.96, 151.26, 145.41 143.88, 143.58, 140.56,
1
1
34.16, 129.06, 128.82, 127.90, 127.15, 127.05, 124.86, 124.49, 121.33, 112.14, 111.24,
10.74, 35.58.
4
.3.8. Synthesis of 4-(furan-3-yl)-2-(thiophen-2-yl)-5H-indeno[1,2-b]pyridine (14)
The compound was synthesized as described in section 4.3 with 5b (0.84 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2e (1.32 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 306 mg (24.2%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.3, mp : 153.5-155.4 C, HPLC: Retention time:
+
9
.92 min, purity: 96.3%; ESI LC/MS m/z calcd for C20
H
13NOS [MH] 316.08; found 316.27
1
9

1
H NMR (250 MHz, CDCl
3
) δ 8.2 (dd, J = 7.35, 1.45 Hz, 1H, indenopyridine H-9), 7.99 (s,
1
H, 4-furan H-2), 7.7 (dd, J = 3.19, 0.91 Hz, 1H, 2-thiophene H-3), 7.64 (s, 1H,
indenopyridine H-3), 7.61-7.58 (m, 2H, 2-thiophene H-5, 4-furan H-5), 7.51-7.40 (m, 3H,
indenopyridine H-6, H-7, H-8), 7.1 (dd, J = 4.9, 3.7 Hz, 1H, 2-thiophene H-4), 6.9 (d, J =
0
.97 Hz, 1H, 4-furan H-4), 3.94 (s, 2H, indenopyridine H-5).
1
3
C NMR (62.5 MHz, CDCl ) δ 161.11, 152.07, 145.34, 143.84, 143.52, 141.49, 140.71,
3
1
3
36.81, 131.29, 128.82, 127.91, 127.26, 124.88, 124.42, 123.62, 121.40, 114.16, 109.12,
5.37.
4
.3.9. Synthesis of 2,4-di(thiophen-2-yl)-5H-indeno[1,2-b]pyridine (15)
The compound was synthesized as described in section 4.3 with 5e (0.90 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2e (1.32 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 397 mg (27.3%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.5, mp : 138.2-140.6 C, HPLC: Retention time:
+
1
2.65 min, purity: 98.3%; ESI LC/MS m/z calcd for C20
H13NS
2
[MH] 332.06; found 332.29
1
H NMR (250 MHz, CDCl ) δ 8.2 (d, J = 6.76 Hz, 1H, indenopyridine H-9), 7.78 (s, 1H,
3
indenopyridine H-3), 7.72 (d, J = 3.49 Hz, 1H, 2-thiophene H-3), 7.65 (d, J = 3.5 Hz, 1H, 4-
thiophene H-5), 7.6 (d, J = 7.11 Hz, 1H, indenopyridine H-8), 7.51 (d, J = 5.1 Hz, 1H, 2-
thiophene H-5), 7.48-7.41 (m, 3H, 4-thiophene H-3, indenopyridine H-6, H-7), 7.26-7.13 (m,
2
H, 2-thiophene H-4, 4-thiophene H-4), 4.1 (s, 2H, indenopyridine H-5).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.48, 152.08, 145.19, 143.74 140.59, 138.43, 130.68,
1
28.90, 128.02, 127.91, 127.23, 127.16, 126.92, 124.85, 124.52, 121.45, 114.08, 35.70.
4
.3.10. Synthesis of 2-(thiophen-2-yl)-4-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (16)
2
0

The compound was synthesized as described in section 4.3 with 5d (0.90 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2e (1.32 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 333 mg (25.1%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.31, mp : 152.5-154.9 C, HPLC: Retention time:
+
1
1.32 min, purity: 99.4%; ESI LC/MS m/z calcd for C20
H13NS
2
[MH] 332.06; found 332.28
1
H NMR (250 MHz, CDCl
.71 (m, 2H, 2-thiophene H-3, 4-thiophene H-2), 7.69 (s, 1H, indenopyridine H-3), 7.58-7.40
m, 6H, indenopyridine H-6, H-7, H-8, 4-thiophene H-4, H-5, 2-thiophene H-5), 7.1 (dd, J =
, 3.68 Hz, 1H, 2-thiophene H-4), 4.02 (s, 2H, indenopyridine H-5).
3
) δ 8.2 (dd, J = 7.34, 1.14 Hz, 1H, indenopyridine H-9), 7.74-
7
(
5
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.23, 152.13, 145.37, 143.79, 140.71, 140.27, 139.10,
1
3
31.81, 128.79, 127.93, 127.21, 127.08, 126.47, 124.84, 124.45, 124.43, 121.43, 115.30,
5.24.
4
.3.11. Synthesis of 4-phenyl-2-(thiophen-2-yl)-5H-indeno[1,2-b]pyridine (17)
Same procedure described as above for 17 was employed with 5a (0.33 g, 1.5 mmol), dry
ammonium acetate (1.156 g, 15 mmol), 2e (0.99 g, 3 mmol) with methanol (15 mL) to yield
1
64 mg (33.3%) of a white solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.47, mp : 132.3-134.4 C, HPLC: Retention time:
+
1
0.32 min, purity: 98.1%; ESI LC/MS m/z calcd for C22
H
15NS [MH] 326.10; found 326.46
1
3
H NMR (250 MHz, CDCl ) δ 8.21 (d, J = 6.87 Hz, 1H, indenopyridine H-9), 7.69 (dd, J =
3
.62, 0.95 Hz, 1H, 2-thiophene H-3), 7.65-7.61 (m, 2H, 4-phenyl H-2, H-6), 7.57 (s, 1H,
indenopyridine H-3), 7.56-7.36 (m, 7H, indenopyridine H-6, H-7, H-8, 2-thiophene H-5, 4-
phenyl H-3, H-4, H-5), 7.12 (t, J = 3.67 Hz, 1H, 2-thiophene H-4), 4.94 (s, 2H,
indenopyridine H-5).
2
1

1
3
3
C NMR (62.5 MHz, CDCl ) δ 160.95, 152.22, 146.36, 145.49, 144.08, 140.87, 138.68,
1
1
32.77, 128.85, 128.73, 128.58, 128.19, 127.89, 127.16, 127.05, 124.86, 124.47, 121.51,
16.42, 34.47.
4
.3.12. Synthesis of 4-(pyridin-2-yl)-2-(thiophen-2-yl)-5H-indeno[1,2-b]pyridine (18)
The compound was synthesized as described in section 4.3 with 5f (0.88 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2e (32 g, 4 mmol) with glacial acetic acid (10 mL) to
yield 385 mg (29.4%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 2:1) R
f
= 0.4, mp : 169.4-172.6 C, HPLC: Retention time:
+
1
3.57 min, purity: 96.8%; ESI LC/MS m/z calcd for C21
H
14
N
2
S [MH] 327.10; found 327.29
1
H NMR (250 MHz, CDCl
3
) δ 8.8 (d, J = 4.54 Hz, 1H, 2-pyridine H-6), 8.2 (d, J = 6.6 Hz,
1
2
2
H, indenopyridine H-9), 7.96 (s, 1H, indenopyridine H-3), 7.88-7.83 (m, 2H, 4-pyridine H-4,
-thiophene H-3), 7.7 (dd, J = 3.2, 0.80 Hz, 1H, 2-thiophene H-3), 7.58 (d, J = 6.88 Hz, 1H,
-pyridine H-5), 7.51-7.34 (m, 4H, indenopyridine H-6, H-7, H-8, 2-pyridine H-3), 7.1 (dd, J
=
5.9, 3.7 Hz, 1H, 2-thiophene H-4), 4.21 (s, 2H, indenopyridine H-5).
1
3
C NMR (62.5 MHz, CDCl ) δ 161.62, 156.19, 152.28, 149.87 145.44, 144.61, 143.88,
3
1
1
40.54, 136.78, 133.10, 128.82, 127.92, 127.08, 124.85, 124.58, 123.28, 122.75, 121.42,
15.35, 35.55.
4
.3.13. Synthesis of 4-(furan-2-yl)-2-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (19)
Same procedure described as above for 19 was employed with 5c (0.105 g, 0.5 mmol), dry
ammonium acetate (0.385 g, 5 mmol), 2d (0.165 g, 0.5 mmol) with methanol (5 mL) to yield
8
4 mg (53.3%) of a white solid.
2
2

o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.36, mp : 149.4-151.7 C, HPLC: Retention time:
+
9
.43 min, purity: 97.4%; ESI LC/MS m/z calcd for C20
H
13NOS [MH] 316.08; found 316.44
1
H NMR (250 MHz, CDCl
3
) δ 8.19 (d, J = 7.11 Hz, 1H, indenopyridine H-9), 8.07-8.06 (m,
1
5
8
H, 2-thiophene H-2), 7.84 (s, 1H, indenopyridine H-3), 7.82 (d, J = 4.32 Hz, 1H, 4-furan H-
), 7.64-7.59 (m, 2H, 2-thiophene H-4, H-5), 7.50-7.40 (m, 3H, indenopyridine H-6, H-7, H-
), 6.97 (d, J = 3.45 Hz, 1H, 4-furan H-3), 6.62-6.60 (m, 1H, 4-furan H-4), 4.04 (s, 2H,
indenopyridine H-5).
1
3
C NMR (62.5 MHz, CDCl ) δ 161.39, 152.92, 151.42, 143.91, 143.50, 142.61, 140.83,
3
1
1
34.17, 128.87, 128.73, 127.14, 126.52, 126.07, 124.91, 123.37, 121.15, 112.64, 112.12,
10.59, 35.53
4
.3.14. Synthesis of 4-(furan-3-yl)-2-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (20)
The compound was synthesized as described in section 4.3 with 5b (0.84 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2d (1.32 g, 4 mmol) with glacial acetic acid (10 mL)
to yield 452 mg (35.8%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.3, mp : 145.4-146.8 C, HPLC: Retention time:
+
9
.71 min, purity: 98.9%; ESI LC/MS m/z calcd for C20
H
13NOS [MH] 316.08; found 316.28
1
H NMR (250 MHz, CDCl ) δ 8.18 (d, J = 6.9 Hz, 1H, indenopyridine H-9), 8 (d, J = 2.97
3
Hz, 1H, 2-thiophene H-2), 7.98 (s, 1H, indenopyridine H-3), 7.79 (d, J = 5.03 Hz, 1H, 2-
thiophene H-5), 7.60-7.58 (m, 3H, 4-furan H-2, H-5, 2-thiophene H-4), 7.51-7.40 (m, 3H,
indenopyridine H-6, H-7, H-8), 6.9 (dd, J = 1.3, 0.8 Hz, 1H, 4-furan H-4), 3.9 (s, 2H,
indenopyridine H-5).
2
3

1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.21, 153.12, 143.83, 143.57 142.62, 141.42, 141.02,
1
3
36.83, 131.10, 128.74, 127.26, 126.51, 126.14, 124.93, 123.77, 123.36, 121.25, 115.60,
5.31.
4
.3.15. Synthesis of 4-(thiophen-2-yl)-2-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (21)
Same procedure described as above for 21 was employed with 5e (0.45 g, 2 mmol), dry
ammonium acetate (1.54 g, 20 mmol), 2d (0.99 g, 3 mmol) with methanol (15 mL) to yield
1
93 mg (29.1%) of a light yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.44, mp : 155.2-157.5 C, HPLC: Retention time:
+
1
1.11 min, purity: 96.7%; ESI LC/MS m/z calcd for C20
H13NS
2
[MH] 332.06; found 332.44
1
3
H NMR (250 MHz, CDCl ) δ 8.18 (d, J = 6.65 Hz, 1H, indenopyridine H-9), 8.04 (s, 1H, 2-
thiophene H-2), 7.80 (d, J = 4.87 Hz, 1H, 4-thiophene H-5), 7.64 (s, 1H, indenopyridine H-3),
.62-7.51 (m, 2H, 2-thiophene H-5, 4-thiophene H-3), 7.49-7.40 (m, 4H, indenopyridine H-6,
7
H-7, H-8, 4-thiophene H-4), 7.24-7.19 (m, 1H, 2-thiophene H-4), 4.06 (s, 2H, indenopyridine
H-5).
1
3
C NMR (62.5 MHz, CDCl ) δ 161.62, 156.19, 152.28, 149.87 145.44, 144.61, 143.88,
3
1
1
40.54, 136.78, 133.10, 128.82, 127.92, 127.08, 124.85, 124.58, 123.28, 122.75, 121.42,
15.35, 35.55.
4
.3.16. Synthesis of 2,4-di(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (22)
The compound was synthesized as described in section 4.3 with 5d (0.90, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2d (1.32 g, 4 mmol) with glacial acetic acid (10 mL)
to yield 389 mg (30.8%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.3, mp : 145.4-146.8 C, HPLC: Retention time:
+
1
0.57 min, purity: 95.6%; ESI LC/MS m/z calcd for C20
H13NS
2
[MH] 332.06; found 332.28
2
4

1
H NMR (250 MHz, CDCl
3
) δ 8.2 (d, J = 7.51 Hz, 1H, indenopyridine H-9), 8 (dd, J = 3.03,
.12 Hz, 1H, 2-thiophene H-2), 7.8 (d, J = 5.02 Hz, 1H, 2-thiophene H-5), 7.7 (dd, J = 4.78,
.4 Hz, 1H, 4-thiophene H-2), 7.67 (s, 1H, indenopyridine H-3), 7.61-7.40 (m, 6H, 2-
1
1
thiophene H-4, 4-thiophene H-4, H-5, indenopyridine H-6, H-7, H-8), 4.05 (s, 2H,
indenopyridine H-5).
1
3
C NMR (62.5 MHz, CDCl ) δ 161.33, 153.16, 143.82, 143.57 142.61, 141, 141.31, 139.29,
3
1
3
31.62, 128.72, 127.22, 126.50, 126.46, 123.17, 124.91, 124.34, 123.36, 121.27, 116.76,
5.20.
4
.3.17. Synthesis of 4-phenyl-2-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (23)
The compound was synthesized as described in section 4.3 with 5a (0.88 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2d (1.32 g, 4 mmol) with glacial acetic acid (10 mL)
to yield 386 mg (29.4%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.3, mp : 144.8-146.4 C, HPLC: Retention time:
+
1
1.22 min, purity: 97.1%; ESI LC/MS m/z calcd for C22
H
15NS [MH] 326.10; found 326.32
1
H NMR (250 MHz, CDCl
3
) δ 8.2 (d, J = 7.03 Hz, 1H, indenopyridine H-9), 8 (dd, J = 2.4,
.14 Hz, 1H, 2-thiophene H-2), 7.8 (dd, J = 4.5, 1 Hz, 1H, 2-thiophene H-5), 7.6 (dd, J = 7.4,
.5 Hz, 2H, 4-phenyl H-2, H-6), 7.56-7.47 (m, 6H, indenopyridine H-3, 4-phenyl H-3, H-4,
1
1
H-5, indenopyridine H-7, H-8), 7.45-7.41 (m, 2H, 2-thiophene H-4 and indenopyridine H-6),
.9 (s, 2H, indenopyridine H-5)
3
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161, 153.14, 146.33, 144.07 142.62, 141.06, 138.77, 132.55,
1
3
28.83, 128.65, 128.53, 128.18, 127.15, 126.51, 126.14, 124.92, 123.34, 121.30, 117.85,
4.39.
4
.3.18. Synthesis of 4-(pyridin-2-yl)-2-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (24)
2
5

The compound was synthesized as described in section 4.3 with 5f (0.88 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2d (1.32 g, 4 mmol) with glacial acetic acid (10 mL)
to yield 341 mg (26.1%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 2:1) R
f
= 0.4, mp : 179.5-181.6 C, HPLC: Retention time:
+
1
3.21 min, purity: 95.4%; ESI LC/MS m/z calcd for C21
H
14
N
2
S [MH] 327.10; found 327.30
1
H NMR (250 MHz, CDCl
3
) δ 8.8 (dt, J = 4.5, 1.3 Hz, 1H, 4-pyridine H-6), 8.2 (dd, J = 7.34,
1
.37 Hz, 1H, indenopyridine H-9), 8.1 (dd, J = 3, 1.2 Hz, 1H, 2-thiophene H-2), 7.94 (s, 1H,
indenopyridine H-3), 7.94-7.84 (m, 3H, 4-pyridine H-4, 2-thiophene H-4, H-5), 7.6 (d, J = 7
Hz, 1H, 4-pyridine H-5), 7.51-7.35 (m 4H, 4-pyridine H-3, indenopyridine H-6, H-7, H-8),
4
.22 (s, 2H, indenopyridine H-5).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.67, 156.31, 153.23, 149.86, 144.59, 143.88, 142.61,
1
1
40.78, 136.77, 132.87, 128.73, 127.04, 126.58 126.08, 124.90, 123.41, 123.23, 122.76,
21.23, 116.76, 35.46.
4
.3.19. Synthesis of 4-(furan-2-yl)-2-(pyridin-2-yl)-5H-indeno[1,2-b]pyridine (25)
The compound was synthesized as described in section 4.3 with 5c (0.84 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2f (1.30 g, 4 mmol) with glacial acetic acid (12 mL) to
yield 367 mg (29.6%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.44, mp : 167.2-168.1 C, HPLC: Retention time:
+
1
2.99 min, purity: 97.7%; ESI LC/MS m/z calcd for C21
H
14
N
2
O [MH] 311.12; found 311.35
1
H NMR (250 MHz, CDCl
3
) δ 8.7 (dd, J = 4.74, 0.8 Hz, 1H, 2-pyridine H-6), 8.69-8.66 (m,
H, 2-pyridine H-3, indenopyridine H-3), 8.2 (dd, J = 7.7, 1.7 Hz, 1H, indenopyridine H-9),
.8 (dt, J = 7.7, 1.7 Hz, 1H, 2-pyridine H-4), 7.66-7.62 (m, 2H, 4-furan H-5, indenopyridine
2
7
H-7), 7.5-7.4 (m, 2H, indenopyridine H-6, H-8), 7.3 (ddd, J = 7.16, 5.07, 1.09 Hz, 1H, 2-
2
6

pyridine H-5), 7 (d, J = 3.4 Hz, 1H, 4-furan H-3), 6.6 (dd, J = 3.4, 1.7 Hz, 1H, 4-furan H-4),
.16 (s, 2H, indenopyridine H-5).
4
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.29, 156.56, 155.44, 151.82, 149.07, 144.12, 143.65,
1
1
40.78, 136.89, 134.48, 130.89, 128.82, 127.17, 125.02, 123.55, 121.29, 121.08, 113.57,
12.07, 110.66, 35.73.
4
.3.20. Synthesis of 4-(furan-3-yl)-2-(pyridin-2-yl)-5H-indeno[1,2-b]pyridine (26)
The compound was synthesized as described in section 4.3 with 5b (0.84 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2f (1.30 g, 4 mmol) with glacial acetic acid (12 mL) to
yield 502 mg (38.4%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.44, mp : 157.3-160.3 C, HPLC: Retention time:
+
1
1.59 min, purity: 97.8%; ESI LC/MS m/z calcd for C21
H
14
N
2
O [MH] 311.12; found 311.33
1
H NMR (250 MHz, CDCl ) δ 8.7 (dd, J = 4.3, 1.83 Hz, 1H, 2-pyridine H-6), 8.6 (d, J = 7.9
3
Hz, 1H, 2-pyridine H-3), 8.48 (s, 1H, 4-furan H-2), 8.2 (dd, J = 7.34, 1.23 Hz, 1H,
indenopyridine H-9), 8.05 (s, 1H, indenopyridine H-3), 7.8 (dt, J = 7.7, 1.7 Hz, 1H, 2-
pyridine H-4), 7.63-7.59 (m, 2H, 4-furan H-5, indenopyridine H-8), 7.52-7.41 (m, 2H,
indenopyridine H-6, H-7), 7.3 (ddd, J = 7.3, 4.8, 1 Hz, 1H, 2-pyridine H-5), 7 (d, J = 0.98 Hz,
1
H, 4-furan H-4), 3.99 (s, 2H, indenopyridine H-5).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 160.94, 156.56, 155.51, 148.98, 143.70, 143.55, 141.63,
1
1
40.91, 137.04, 136.93, 132.96, 128.79, 127.28, 125.01, 123.85, 123.57, 121.35, 121.11,
16.22, 109.38, 35.86.
4
.3.21. Synthesis of 2-(pyridin-2-yl)-4-(thiophen-2-yl)-5H-indeno[1,2-b]pyridine (27)
2
7

The compound was synthesized as described in section 4.3 with 5e (0.90 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2f (1.30 g, 4 mmol) with glacial acetic acid (12 mL) to
yield 377 mg (28.9%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.44, mp : 169.2-172.4 C, HPLC: Retention time:
+
1
4.76 min, purity: 95.1%; ESI LC/MS m/z calcd for C21
H
14
N
2
S [MH] 327.10; found 327.35
1
H NMR (250 MHz, CDCl
7.83 Hz, 1H, 2-pyridine H-3), 8.64 (s, 1H, indenopyridine H-3), 8.2 (dd, J = 7.42, 1.47 Hz,
H, indenopyridine H-9), 7.8 (dt, J = 7.73, 1.7 Hz, 1H, 2-pyridine H-4), 7.7 (dd, J = 3.7, 1.7
Hz, 1H, 4-thiophene H-5), 7.6 (dd, J = 6.44, 1.17 Hz, 1H, indenopyridine H-7), 7.54-7.45 (m,
H, 4-thiophene H-3, indenopyridine H-6, H-8), 7.3 (ddd, J = 7.4, 4.8, 1.2 Hz, 1H, 2-pyridine
H-5), 7.2 (dt, J = 6.02, 2.29 Hz, 1H, 4-thiophene H-4), 4.16 (s, 2H, indenopyridine H-5).
3
) δ 8.7 (ddd, J = 4.7, 1.7, 0.89 Hz, 1H, 2-pyridine H-6), 8.68 (d, J
=
1
3
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.35, 156.45, 155.57, 149.07, 143.79, 140.86, 140.82,
1
3
38.67, 136.89, 132.31, 128.88, 127.93, 127.28, 127.15, 125, 123.59, 121.32, 121.18, 116.15,
5.85.
4
.3.22. Synthesis of 2-(pyridin-2-yl)-4-(thiophen-3-yl)-5H-indeno[1,2-b]pyridine (28)
The compound was synthesized as described in section 4.3 with 5d (0.90 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2f (1.30 g, 4 mmol) with glacial acetic acid (12 mL) to
yield 583 mg (42.6%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:5) R
f
= 0.44, mp : 178.4-181.1 C, HPLC: Retention time:
+
1
3.22 min, purity: 100%; ESI LC/MS m/z calcd for C21
H
14
N
2
S [MH] 327.10; found 327.35
1
3
H NMR (250 MHz, CDCl ) δ 8.72-8.70 (m, 2H, 2-pyridine H-3, H-6), 8.55 (s, 1H, 4-
thiophene H-2), 8.2 (d, J = 6.9 Hz, 1H, indenopyridine H-9), 8.08 (s, 1H, indenopyridine H-
), 7.9 (dd, J = 7.8, 1.7 Hz, 1H, 2-pyridine H-4), 7.8 (dd, J = 1.27, 3 Hz, 1H, 4-thiophene H-
3
2
8

5
), 7.67 (dd, J = 5.06, 1.2 Hz, 1H, 4-thiophene H-4), 7.6 (dd, J = 6.71, 0.87 Hz, 1H,
indenopyridine H-8), 7.51-7.44 (m, 3H, indenopyridine H-6, H-7, thiophene H-4), 7.3 (ddd, J
6.87, 4.36, 1.06 Hz, 1H, 2-pyridine H-5), 4.33 (s, 2H, indenopyridine H-5).
=
1
3
3
C NMR (62.5 MHz, CDCl ) δ 161.57, 156.59, 156.55, 155.67, 149.59, 149.04, 144.95,
1
1
43.88, 140.70, 136.90, 136.69, 135.29, 128.78, 126.98, 125, 123.53, 123.14, 122.88, 121.30,
21.10, 117.28, 35.36.
4
.3.23. Synthesis of 4-phenyl-2-(pyridin-2-yl)-5H-indeno[1,2-b]pyridine (29)
The compound was synthesized as described in section 4.3 with 5a (0.88 g, 4 mmol), dry
ammonium acetate (3.17 g, 40 mmol), 2f (1.30 g, 4 mmol) with glacial acetic acid (12 mL) to
yield 581 mg (45.3%) of a yellow solid.
o
TLC (ethyl acetate / n-hexane = 1:3) R
f
= 0.28, mp : 153.7-155.4 C, HPLC: Retention time:
+
1
4.15 min, purity: 95.4%; ESI LC/MS m/z calcd for C23
H
16
N
2
[MH] 321.14; found 321.40
1
H NMR (250 MHz, CDCl ) δ 8.71-8.68 (m, 2H, 2-pyridine H-3, H-6), 8.43 (s, 1H,
3
indenopyridine H-3), 8.2 (dd, J = 7.33, 0.9 Hz, 1H, indenopyridine H-9), 7.87 (dd, J = 7.60,
1
4
2
.56 Hz, 1H, 2-pyridine H-4), 7.73-7.69 (m, 2H, indenopyridine H-6, H-7), 7.56-7.39 (m, 6H,
-phenyl H-2, H-3, H-4, H-5, H-6, indenopyridine H-8), 7.3 (ddd, J = 7.46, 4.66, 1.31 Hz, 1H,
-pyridine H-5), 4.04 (s, 2H, indenopyridine H-5).
1
3
3
C NMR (62.5 MHz, CDCl ) δ 160.37, 156.65, 155.66, 149.06, 146.56, 144.09, 141.01,
1
1
38.70, 136.88, 134.52, 128.71, 128.48, 128.234, 127.19, 125, 123.51, 121.33, 121.21,
18.58, 34.57.
4
.3.24. Synthesis of 2,4-di(pyridin-2-yl)-5H-indeno[1,2-b]pyridine (30)
2
9