Synthesis and biological evaluation of novel flavone/triazole/benzimidazole hybrids and flavone/isoxazole-annulated heterocycles as antiproliferative and antimycobacterial agents

Article abstract of DOI:10.1007/s11030-018-9833-4

Abstract: A series of new flavone/isoxazole fused heterocycles 5a–f and flavone/1,2,3-triazole/benzimidazole hybrid heterocycles compounds 7a–t were synthesized via an intramolecular cyclization and Cu(I)-catalyzed click 1,3-dipolar cycloaddition. The pro

Full text of DOI:10.1007/s11030-018-9833-4

Molecular Diversity
https://doi.org/10.1007/s11030-018-9833-4
ORIGINAL ARTICLE
Synthesis and biological evaluation of novel
flavone/triazole/benzimidazole hybrids and
flavone/isoxazole-annulated heterocycles as antiproliferative and
antimycobacterial agents
Yerrabelly Jayaprakash Rao1 · Thummala Sowjanya2 · Gogula Thirupathi1 ·
Nandula Yadagiri Sreenivasa Murthy3 · Sudha Sravanti Kotapalli4
Received: 5 September 2017 / Accepted: 14 May 2018
© Springer International Publishing AG, part of Springer Nature 2018
Abstract
A series of new flavone/isoxazole fused heterocycles 5a–f and flavone/1,2,3-triazole/benzimidazole hybrid heterocycles
compounds 7a–t were synthesized via an intramolecular cyclization and Cu(I)-catalyzed click 1,3-dipolar cycloaddition. The
products were evaluated for their antiproliferative activity against human breast cancer cell line (MCF-7) using sulforhodamine
B assay (SRB) and antimycobacterial activity using turbidometric assay. The majority of the tested compounds exhibited
antiproliferative activity and antimycobacterial activity. Compounds 7l, 7q and 7r showed moderate antiproliferative activity
with IC50 values 17.9, 14.2, 19.1µM, respectively, and compound 5a showed moderate antimycobacterial activity with 41.7%
of inhibition at 30µM concentration.
Graphical Abstract
Keywords 8-Formyl-7-hydroxy flavones · Click chemistry · 1, 2, 3-Triazole · Antimycobacterial activity · Antiproliferative
activity · Cycloaddition
Introduction
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s11030-018-9833-4) contains supplementary
material, which is available to authorized users.
The synthesis and functionalization of flavones has become
a major area of focus for synthetic organic chemists because
of the varied pharmacological activities flavone derivatives
Yerrabelly Jayaprakash Rao
yjpr_19@yahoo.com
B
exhibit [1]. Flavones are a class of natural products most
3
4
1
Department of Chemistry, Palamuru University,
Mahabubnagar, India
Department of Chemistry, University College of Science,
Saifabad, Osmania University, Hyderabad, India
2
Centre for Chemical Biology, Indian Institute of Chemical
Technology, Hyderabad, India
Department of Chemistry, Jawaharlal Nehru Technological
University, Hyderabad, India
123

Molecular Diversity
Fig. 1 Chemical structures of
some anti cancerous flavones
OH
O
O
O
OH
O
HO
O
O
HO
O
O
OH
OH
OH
OH
Chrysoeriol
Silybin
Fig. 2 Pharmacologically important triazole, benzimidazole and isoxazole based drugs
abundant in fruits, seeds, nuts and flowers and are impor-
tant components of human diet. These compounds exhibit
antioxidant[2], antihypertensive[3], antiallergic[4], antibac-
terial and antifungal [5,6] activities, and can act as plant
growth regulators [7]. Flavones have a number of positive
features among which the most significant is their antioxi-
dant effects, which provide enhanced protection of the body
against the harmful effects of free radical reactions [8].
Hydroxy flavones and their derivatives are potential anti-
cancer as well as antibacterial and antifungal agents [9,10].
Moreover, heterocyclic ring pendent or fused at 7/8 posi-
tions of flavones is reported to possess anticancer activities
[11]. Examples of commercially available anticancer flavone
drugs are depicted in Fig. 1 [12].
vulsant activities [23,24]. Isoxazoles are important structural
moieties, which are largely used in pharmaceuticals and
therapeutics[25–27]. Examplesofpharmacologicallyimpor-
tant triazole-, benzimidazole- and isoxazole- based drugs are
shown in Fig. 2.
In continuation of our efforts on structural modification
of hydroxy flavone moieties [28,29] to enhance their biolog-
ical activity, we planned for the synthesis of novel hybrid
heterocycles having benzimidazole, triazole and isoxazole
scaffolds in a single molecule by adopting Cu(I)-catalyzed
click chemistry and intramolecular cyclization reactions.
Results and discussion
Triazoles are a class of N-heterocyclic compounds with
diversified biological activities such as antimicrobial [13],
antiprotozoal [14], anti-inflammatory [15], antitubercular
[16], antibacterial [17], anticancer [18], antimalarial [19],
antiviral [20] and antiproliferative activities [21,22]. Ben-
zimidazole scaffolds are of special interest to medicinal
chemistry because its derivatives possess antioxidant, antimi-
crobial, antihelmintic, anticancer, antihypertensive, antineo-
plastic, anti-inflammatory, analgesic, antiprotozoal, anti-
hepatitis B virus, antiulcer, antiviral, antifungal and anticon-
Chemistry
A new series of heterocycles have been synthesized by
incorporating triazole and isoxazole moieties at the 7 and 8
positions of 8-formyl-7-hydroxy flavone. Further, these new
series of compounds were tested for their antimycobacterial
activity and antiproliferative activity against human breast
cancer cell line (MCF-7). 7-Hydroxy flavones 1a–f were
treated with HMTA/acetic acid at 100◦C to obtain 8-formyl-
123

Molecular Diversity
R1
R1
R1
CHO
CHO
Br
HO
O
HO
O
O
O
O
O
HMTA
AcOH, 90oC, 12 h
R
R
K2CO3, DMSO
R
O
1a-f
2a-f
3a-f
NH2OH.HCl
NaOAC, EtOH
O
N
OH
N
H
R1
R1
CAN, ACN
0-5oC
O
O
O
O
R
R
O
O
4a-f
5a-f
a R = CH3, R1 = H
d R = H, R1 = H
b R = CH3, R1 = OCH3
e R = H, R1 = OCH3
c R = CH3, R1 = NO2
f R = H, R1 = NO2
Scheme 1 Synthesis of flavone/isoxazole heterocyclic compounds
7-hydroxy flavones 2a–f [30,31]. Compounds 2a–f were
coupled with propargyl bromide in acetone/K2CO3 medium
to get 4-oxo-2-phenyl-7-(prop-2-ynyloxy)-4H-chromene-8-
carbaldehydes 3a–f. The formyl groups of compounds 3a–f
were converted into corresponding oximes 4a–f by treat-
ing them with hydroxyl amine hydrochloride in sodium
acetate/ethanol medium. Compounds 4a–f were subjected
to intramolecular cyclization using ceric ammonium nitrate
(CAN) and acetonitrile at 0–5◦C to yield final compounds
5a–f (Scheme 1). The structures of compounds 5a–f were
confirmed by spectral analysis.
The next step of the present study was the prepara-
tion of novel flavone/triazole/benzimidazole hybrid hete-
rocycles 7a–t from 3a and 3d. Compounds 3a and 3d
underwent smooth condensation with orthophenylenedi-
amine (OPDA) in ethanol/acetic acid medium to yield
compounds 6a and 6d, respectively. These were further
reacted with aromatic and aliphatic azides in the pres-
ence of CuSO4 and sodium ascorbate in DMF − H2O
medium. The terminal alkyne of 6a and 6d underwent
1,4 regioselective 1,3-dipolar cycloaddition (click chem-
istry) and produced 7-((1-alkyl/aralkyl-1H-1,2,3-triazol-4-
yl)methoxy)-8-(1H-benzo[d]imidazol-2-yl)-3-methyl-2
-phenyl-4H-chromen-4-onesingoodyields7a–t(Scheme2).
All the synthesized products 7a–t were characterized by 1H
NMR, 13C NMR, FTIR and mass spectral analysis.
Biological activity
The newly synthesized compounds 5a–f and 7a–t were
screened for their in vitro antiproliferative activity against
breast cancer cell line MCF-7 using standard SRB (Sulforho-
damine B), and the results are summarized in Table 1. Among
the tested compounds, one compound 7q showed moderate
activityagainstMCF-7celllinewithIC50 value14.5µM, two
compounds 7l and 7r with IC50 values of 17.9 and 19.1µM,
respectively, and nine compounds 7j, 7d, 7t, 5a, 7g, 7f, 7s, 7p
and 5b showed less activity with IC50 values of 25.1, 30.8,
31.9, 34.2, 37.6, 40.2, 41.2, 42.3 and 45.2µM, respectively.
The remaining compounds in the series showed little to no
antiproliferation against MCF-7 cell line.
Our structure–activity relationship study revealed that the
orientation of a substituent on 1,2,3-triazole ring and flavone/
benzimidazole hybrid is crucial for inducing antiprolifera-
tive activity against MCF-7 cancer cell line. In particular,
compounds 7q, 7l and 7r showed the best antiproliferative
profile of this compound series with IC50 values of 14.2, 17.9,
19.1µM, respectively. The activity was further enhanced in
the presence of an electron withdrawing group at the fourth
position of the benzene ring attached to the triazole hybrid.
Additionally, compounds 5a–f and 7a–t were evaluated
for antimycobacterial activity against Mycobacterium bovis
strain (BCG) using a turbidometric assay. The screening
123

Molecular Diversity
R1
CHO
NH2
HN
N
R1
HN
N
R1
O
O
O
N
N
N
R2-N3
R2
O
O
O
NH2
O
O
O
R
DMF-H2O
R
EtOH, AcOH
R
CuSO4-Sodium Ascorbate
3a and 3d
6a and 6d
7a-t
3a R = CH3, R1 = H
3d R = H, R1 = H
6a R = CH3, R1 = H
6d R = H, R1 = H
7a R = CH3, R1 = H, R2 = C6H5
7b R = CH3, R1 = H, R2 = p-Cl-C6H4
7d R = CH3, R1 = H, R2 = p-NO2-C6H4
7f R = CH3, R1 = H, R2 = 2,6-(CH3)2-C6H3
7h R = CH3, R1 = H, R2 = p-F-Benzyl
7j R = CH3, R1 = H, R2 = Hexyl
7l R = H, R1 = H, R2 = p-Cl-C6H4
7n R = H, R1 = H, R2 = p-NO2-C6H4
7p R = H, R1 = H, R2 = 2,6-(CH3)2-C6H3
7r R = H, R1 = H, R2 = p-F-Benzyl
7t R = H, R1 = H, R2 = Hexyl
7c R = CH3, R1 = H, R2 = m-CH3-C6H4
7e R = CH3, R1 = H, R2 = m-Cl-C6H4
7g R = CH3, R1 = H, R2 = p-NO2-Benzyl
7i R = CH3, R1 = H, R2 = Cyclopentyl
7k R = H, R1 = H, R2 = C6H5
7m R = H, R1 = H, R2 = m-CH3-C6H4
7o R = H, R1 = H, R2 = m-Cl-C6H4
7q R = H, R1 = H, R2 = p-NO2-Benzyl
7s R = H, R1 = H, R2 = Cyclopentyl
Scheme 2 Synthesis of new flavone/triazole/benzimidazole hybrid heterocyclic compounds
Table 1 IC50 µM values of
Entry
Tested compounds
BCG values % inhibition
STD DEV
0.040
MCF-7 IC50(µM)
SD
tested compounds against BCG
and MCF-7
1
7a
12.7
NA
0.1
NA
NA
2
7b
NA
NA
3
7c
0.048
0.043
0.057
0.050
0.045
0.063
0.052
0.012
0.005
0.013
0.025
0.011
0.017
0.057
0.026
0.005
0.084
0.054
0.012
0.009
0.045
0.064
0.025
0.019
–
NA
NA
4
7d
4.0
30.8
99.7
40.2
37.6
NA
0.003
0.102
0.039
0.052
NA
5
7e
0.2
6
7f
1.1
7
7g
1.4
8
7h
11.6
8.7
9
7i
91.4
25.1
NA
0.066
0.472
NA
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
7j
26.2
13.1
13.6
6.3
7k
7l
17.9
NA
0.001
NA
7m
7n
18.4
12.2
2.1
NA
NA
7o
NA
NA
7p
42.3
14.2
19.1
41.2
31.9
34.2
45.2
92.7
68.7
90.9
NA
0.004
0.018
0.083
0.001
0.008
0.052
0.078
0.009
0.472
0.213
NA
7q
5.7
7r
0.1
7s
5.2
7t
27.3
41.7
1.9
5a
5b
5c
9.9
5d
14.4
8.9
5e
5f
9.0
Doxorubicin
Rifampicin
–
6.2µM
–
–
97%
–
–
bold values indicate with moderate activity
123

Molecular Diversity
results revealed that the series of compounds 5a–f and 7a–t
inhibited the growth of the bacteria with a MIC range of 0.1 to
>40mg/mL. Compound 5a was found to be associated with
moderate antimycobacterial activity with BCG% inhibition
value of 41.7.
General procedure for the synthesis of 4-oxo-2-aryl-
7-(prop-2-ynyloxy)-4H-chromene-8-carbaldehydes
(3a–f)
7-Hydroxyflavone 1a-f (1.0 mmol) dissolved in acetic
acid (20 mL), then hexamethylenetetramine (HMTA) (4.0
mmol) was added, and the resulting solution was stirred at
90 ◦C for1 h. The reaction was treated with cold water and
filtered. The separated product was dried and recrystallized
from methanol to give 4-oxo-2-aryl-7-(prop-2-ynyloxy)-4H-
chromene-8-carbaldehydes 3a–f.
Conclusion
In summary, 2 libraries of new hybrid heterocyclic com-
pounds, 9-alkyl-10-arylpyrano[2ꢀ,3ꢀ:5,6]chromeno[4,3-c]
isoxazol-8(4H)-ones 5a–f and 7-((1-alkyl/aryl-1H-1,2,3-
triazol-4-yl)methoxy)-8-(1H-benzo[d]imidazol- 2-yl)- 2-
phenyl-4H-chromen-4-ones 7a–t, were synthesized by using
an intramolecular cyclization and click chemistry approach.
Compounds 7q, 7l and 7r showed moderate antiproliferative
activity against human breast cancer cell line MCF-7, and
compound 5a showed moderate antimycobacterial activity
against bovis strain. From this, we were able to identify a few
active molecules which are capable of inhibiting the growth
of Mycobacterium bovis strain (BCG) and human breast can-
cer cell line MCF-7.
3-Methyl-4-oxo-2-phenyl-7-(prop-2-ynyloxy)
-4H-chromene-8-carbaldehyde (3a)
Off-white solid, yield 75%; m.p. 240–242◦C. IR (KBr,
cm−1): 1725 (CHO), 1690 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.24 (s, 3H, CH3), 2.63 (s, 1H, CH), 4.97 (s, 2H,
CH2), 7.53–7.55 (m, 4H, Ar–H), 7.79–7.81 (m, 2H, Ar–H),
8.49 (d, J = 9.14Hz, 1H, Ar–H), 10.65 (s, 1H, CHO) ppm.
ESI-MS: m/z 319 [M + H]+.
Experimental
2-(4-Methoxyphenyl)-3-methyl-4-oxo-7-(prop-2-ynyloxy)-
4H-chromene-8-carbaldehyde (3b)
All reagents were purchased from Merck and commercial
sources and were used without further purification. Melt-
ing points (m.p.) were determined in open capillary tubes
on a Buchi 530 melting point apparatus and are uncor-
rected. Thin layer chromatography (TLC) was performed
to monitor progress of the reaction and assess purity of the
compounds; spots were detected by their absorption under
UV light. IR spectra were recorded using an IR prestige-
21 (FTIR, Shimadzu). Mass spectra were recorded using a
Off-white solid, yield 72%; m.p. 239–240◦C. IR (KBr,
cm−1): 1729 (CHO), 1695 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.19 (s, 3H, CH3), 2.65 (s, 1H, CH), 3.90 (s, 3H,
OCH3), 4.89 (s, 2H, CH2), 7.50–7.53 (m, 4H, Ar–H), 7.72–
7.75 (m, 2H, Ar–H), 10.55 (s, 1H, CHO) ppm. ESI-MS: m/z
349 [M + H]+.
1
3-Methyl-2-(4-nitrophenyl)-4-oxo-7-(prop-2-ynyloxy)
-4H-chromene-8-carbaldehyde (3c)
‘Hewlett–Packard’ HP GS/MS 5890/5972. H NMR spec-
tra were recorded on a Bruker DPX operating at 400MHz
in CDCl3 or DMSO − d6 solvent, using tetramethylsilane
(TMS) as an internal standard. Chemical shifts are shown as
δ values (ppm); the coupling constants (J) are expressed in
Hertz (Hz). Signals are represented as s (singlet), d (doublet),
t (triplet), q (quartet) or m (multiplet).
Off-white solid, yield 70%; m.p. 243–244◦C. IR (KBr,
cm−1): 1727 (CHO), 1700 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.27 (s, 3H, CH3), 2.67 (s, 1H, CH), 5.01 (s, 2H,
CH2), 7.54–7.57 (m, 2H, Ar–H), 7.75–7.77 (m, 2H, Ar–H),
8.29 (d, J = 9.14Hz, 2H, Ar–H), 10.63 (s, 1H, CHO) ppm.
ESI-MS: m/z 364 [M + H]+.
General procedure for the synthesis of
8-formyl-7-hydroxyflavones (2a–f)
7-Hydroxyflavones 1a–f (1.0mmol) dissolved in glacial
acetic acid (20mL), hexamethylenetetramine (HMTA)
(4.0mmol) were added, and the resulting solution was stirred
at 100◦C for 6h. The solution was treated with dil. HCl
(1:1) followed by further heating for 30min; it was diluted
to 500mL with cold water and left overnight in a refrig-
erator. Product was filtered, dried and purified by column
chromatography in ethyl acetate/n-hexane (9:1) to get 8-
formyl-7-hydroxyflavones 2a–f.
4-Oxo-2-phenyl-7-(prop-2-ynyloxy)-4H-chromene-8-
carbaldehyde (3d)
Off-white solid, yield 75%; m.p. 235–237◦C. IR (KBr,
cm−1): 1729 (CHO), 1699 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.64 (s, 1H, CH), 5.01 (s, 2H, CH2), 6.81 (s, 1H,
Ar–H), 7.49–7.53 (m, 4H, Ar–H), 7.78–7.83 (m, 2H, Ar–H),
8.39 (d, J = 9.14Hz, 1H, Ar–H), 10.52 (s, 1H, CHO) ppm.
ESI-MS: m/z 305 [M + H]+.
123

Molecular Diversity
2-(4-Methoxyphenyl)-4-oxo-7-(prop-2-ynyloxy)
(E)-3-Methyl-2-(4-nitrophenyl)-4-oxo-7-(prop-2
-4H-chromene-8-carbaldehyde (3e)
-yn-1-yloxy)-4H-chromene-8-carbaldehyde oxime (4c)
Off-white solid, yield 71%; m.p. 238–239◦C. IR (KBr,
cm−1): 1739 (CHO), 1716 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.60 (s, 1H), 3.89 (s, 3H, OCH3), 5.05 (s, 2H,
CH2), 6.84 (s, 1H, Ar–H), 7.52–7.56 (m, 4H, Ar–H), 7.80–
7.84 (m, 2H, Ar–H), 10.59 (s, 1H, CHO) ppm. ESI-MS: m/z
335 [M + H]+.
Off-white solid, yield 76%; m.p. 252–254◦C. IR (KBr,
1
cm−1): 1729 (C=O). H NMR (400MHz, CDCl3) δ 2.12
(s, 3H, CH3), 3.62 (s, 1H, CH), 5.21 (s, 2H, CH2), 7.42–7.45
(d, J = 8.71Hz, 2H, Ar–H), 7.62–7.64 (m, 2H, Ar–H), 7.87
(s, 2H, Ar–H), 8.13–8.15 (d, J = 8.71Hz, 1H, CH), 11.59
(s, 1H, OH) ppm. ESI-MS: m/z 379 [M + H]+.
2-(4-Nitrophenyl)-4-oxo-7-(prop-2-ynyloxy)-4H-chromene-
(E)-4-Oxo-2-phenyl-7-(prop-2-yn-1-yloxy)-4H-chromene
8-carbaldehyde (3f)
-8-carbaldehyde oxime (4d)
Off-white solid, yield 70%, m.p. 242–244◦C. IR (KBr,
cm−1): 1735 (CHO), 1706 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.65 (s, 1H), 4.99 (s, 2H, CH2), 6.83 (s, 1H,
Ar–H), 7.55–7.59 (m, 2H, Ar–H), 7.75–7.79 (m, 2H, Ar–
H), 8.59 (d, J = 9.14Hz, 2H, Ar–H), 10.63 (s, 1H, CHO)
ppm. ESI-MS: m/z 350 [M + H]+.
Off-white solid, yield 79%; m.p. 249–250◦C. IR (KBr,
1
cm−1): 1735 (C=O). H NMR (400MHz, CDCl3) δ 3.72
(s, 1H, CH), 5.21 (s, 2H, CH2), 6.79 (s, 1H, Ar–H), 7.29–7.31
(d, J = 8.71Hz, 1H, Ar–H), 7.47–7.49 (m, 4H, Ar–H), 7.69
(s, 2H, Ar–H), 8.01–8.02 (d, J = 8.71Hz, 1H, CH), 11.42
(s, 1H, OH) ppm. ESI-MS: m/z 320 [M + H]+.
General procedure for the synthesis of
(E)-3-alkyl-4-oxo-2-aryl-7-(prop-2-yn-1-yloxy)
-4H-chromene-8-carbaldehyde oximes (4a–f)
(E)-2-(4-Methoxyphenyl)-4-oxo-7-(prop-2-yn-1-yloxy)
-4H-chromene-8-carbaldehyde oxime (4e)
Off-white solid, yield 74%; m.p. 254–255◦C. IR (KBr,
1
To a stirred solution of 4-oxo-2-phenyl-7-(prop-2-ynyloxy)-
4H-chromene-8-carbaldehydes 3a–f (1.0mmol) in EtOH
was added sodium acetate (1.5mmol) and hydroxylamine
hydrochloride (2.0mmol) at room temperature. The reaction
mixture was stirred for 1h at reflux temperature. After com-
pletion of reaction, as judged by TLC, solvent was removed
and diluted with cold water. The obtained precipitate was
filtered, dried and recrystallized from methanol to give the
products 4a–f.
cm−1): 1719 (C=O). H NMR (400MHz, CDCl3) δ 3.63
(s, 1H, CH), 3.95 (s, 3H, OCH3), 5.01 (d, J = 1.40Hz,
2H, CH2), 6.91 (s, 1H, Ar–H), 7.45–7.47 (d, J = 8.71Hz,
2H, Ar–H), 7.48–7.49 (m, 2H, Ar–H), 7.71 (s, 2H, Ar–H),
8.00–8.02 (d, J = 8.71Hz, 1H, CH), 11.47(s, 1H, OH) ppm.
ESI-MS: m/z 350 [M + H]+.
(E)-2-(4-Nitrophenyl)-4-oxo-7-(prop-2-yn-1-yloxy)
-4H-chromene-8-carbaldehyde oxime (4f)
(E)-3-Methyl-4-oxo-2-phenyl-7-(prop-2-yn-1-yloxy)
-4H-chromene-8-carbaldehyde oxime (4a)
Off-white solid, yield 72%; m.p. 256–258◦C. IR (KBr,
cm−1): 1740 (C=O). 1H NMR (400MHz, CDCl3)δ 3.55 (s,
1H, CH), 5.17 (S, 2H, CH2), 6.84 (s, 1H, Ar–H), 7.42–7.45
(d, J= 8.71Hz, 2H, Ar–H), 7.60–7.62 (m, 2H, Ar–H), 7.86
(s, 2H, Ar–H), 8.17–8.19 (d, J = 8.71Hz, 1H, CH), 11.49
(s, 1H, OH) ppm. ESI-MS: m/z364 [M + H]+.
Off-white solid, yield 80%; m.p. 250–252◦C. IR (KBr,
1
cm−1): 1739 (C=O). H NMR (400MHz, CDCl3) δ 2.08
(s, 3H, CH3), 3.72 (s, 1H, CH), 5.07 (s, 2H, CH2), 7.35–7.37
(d, J = 8.71Hz, 1H, Ar–H), 7.58–7.59 (m, 4H, Ar–H), 7.81
(s, 2H, Ar–H), 8.10–8.12 (d, J = 8.71Hz, 1H, CH), 11.58
(s, 1H, OH) ppm. ESI-MS: m/z 334 [M + H]+.
General procedure for the synthesis of
9-alkyl-10-arylpyrano[2ꢀ,3ꢀ:5,6]chromeno[4,3-
c]isoxazol-8(4H)-ones
(E)-2-(4-Methoxyphenyl)-3-methyl-4-oxo-7-(prop-2
-yn-1-yloxy)-4H-chromene-8-carbaldehyde oxime (4b)
(5a–f)
Compounds 4a–f (1.0mmol) were dissolved in acetonitrile
and then the ceric ammonium nitrate (2.0mmol) at 0–5◦C
was added; the resulting mixture was stirred at 5◦C for
30min. The reaction mixture was extracted with chloroform
and wash with brine solution. The crude material was purified
by column chromatography in chloroform/methanol (9:1) to
give the products 5a–f.
Off-white solid, yield 78%; m.p. 253–255◦C. IR (KBr,
cm−1): 1725 (C=O). 1H NMR (400MHz, CDCl3)δ 2.06 (s,
3H, CH3), 3.61 (s, 1H, CH), 3.91 (s, 3H, OCH3), 5.02 (s, 2H,
CH2), 7.32–7.36 (d, J = 8.79Hz, 2H, Ar–H), 7.55–7.57 (m,
2H, Ar–H), 7.76 (s, 2H, Ar–H), 8.08–8.10 (d, J = 8.79Hz,
1H, CH), 11.54(s, 1H, OH)ppm. ESI-MS:m/z365[M+H]+.
123

Molecular Diversity
9-Methyl-10-phenylpyrano[2ꢀ,3ꢀ
10-(4-Methoxyphenyl)pyrano[2ꢀ,3ꢀ:5,6]chromeno[4,3-
:5,6]chromeno[4,3-c]isoxazol-8(4H)-one (5a)
c]isoxazol-8(4H)-one (5e)
Light brown color solid, yield 70%; m.p. 298–300◦C. IR
Light brown color solid, yield 62%; m.p. 293–295◦C. IR
(KBr, cm−1): 1627 (C=O). 1H NMR (400MHz, CDCl3) δ
3.89 (s, 3H, OCH3), 5.45 (s, 2H, O − CH2), 7.05 (d, J =
8.70Hz, 1H, Ar–H), 7.56 (m, 5H, Ar–H), 8.18 (m, 2H, Ar–H)
ppm. 13C NMR (100MHz, DMSO-d6) δ 56.5, 64.5, 102.7,
110.3, 115.8, 116.6, 116.8, 128.4, 128.6, 129.0, 129.4, 130.1,
132.5, 148.9, 152.7, 159.9, 160.2, 176.3 ppm. ESI-MS: m/z
348 [M + H]+. Anal. calcd. for C20H13NO5: C, 69.16; H,
3.77; N, 4.03%. Found: C, 69.80; H, 4.18; N, 3.88%.
1
(KBr, cm−1): 1623 (C=O). H NMR (400MHz, CDCl3)δ
2.28(s, 3H, CH3), 5.39(s, 2H, O-CH2), 7.08(d, J = 8.70Hz,
1H, Ar–H), 7.54 (m, 5H, Ar–H), 8.26 (m, 2H, Ar–H) ppm.
13C NMR(100MHz, DMSO − d6) δ 11.8, 62.2, 102.7,
110.3, 115.8, 116.6, 116.8, 128.4, 128.6, 129.1, 129.3, 130.5,
132.3, 150.2, 152.5, 159.0, 160.0, 176.3 ppm. ESI-MS: m/z
332 [M + H]+. Anal. calcd. for C20H13NO4: C, 72.50; H,
3.95; N, 4.23%. Found: C, 72.02; H, 4.12; N, 4.32%.
10-(4-Methoxyphenyl)-9-methylpyrano[2ꢀ
10-(4-Nitrophenyl)pyrano[2ꢀ,3ꢀ:5,6]chromeno[4,3-
c]isoxazol-8(4H)-one (5f)
,3ꢀ:5,6]chromeno[4,3-c]isoxazol-8(4H)-one (5b)
Light brown color solid, yield 68%; m.p. 299–300◦C. IR
(KBr, cm−1): 1628 (C=O). 1H NMR (400MHz, CDCl3) δ
2.19 (s, 3H, CH3), 3.73 (s, 3H, OCH3), 5.24 (s, 2H, OCH2),
7.06 (d, J = 8.70Hz, 1H, Ar–H), 7.55 (m, 4H, Ar–H), 8.28
(m, 2H, Ar–H) ppm. 13C NMR (100MHz, DMSO − d6) δ
12.1, 56.5, 62.8, 102.7, 110.3, 115.8, 116.6, 116.8, 128.4,
128.6, 129.0, 129.4, 130.1, 132.5, 150.0, 152.7, 159.9, 160.2,
176.8 ppm. ESI-MS: m/z 362 [M+1]+. Anal. calcd. for
C21H15NO5: C, 69.80; H, 4.18; N, 3.88%. Found: C, 70.01;
H, 3.98; N, 3.70%.
Light brown color solid, yield 65%; m.p. 297–299◦C. IR
(KBr, cm−1): 1635 (C=O). 1H NMR (400MHz, CDCl3) δ
5.39 (s, 2H, O − CH2), 7.08 (d, J = 8.70Hz, 1H, Ar–H),
7.54 (m, 5H, Ar–H), 8.26 (m, 2H, Ar–H) ppm. 13C NMR
(100MHz, DMSO − d6)δ 63.4, 102.7, 110.3, 115.8, 116.6,
116.8, 128.4, 128.6, 129.0, 129.4, 130.1, 132.5, 148.9, 152.7,
159.9, 160.2, 177.5 ppm. ESI-MS: m/z 363 [M+H]+. Anal.
calcd. for C19H10N2O6: C, 62.99; H, 2.78; N, 7.73%. Found:
C, 63.83; H, 3.21; N, 7.44%.
General procedure for the synthesis of
8-(1H-benzo[d ]imidazol-2-yl)-2-phenyl-7-(prop
-2-ynyloxy)-4H -chromen-4-one (6a and 6d)
9-Methyl-10-(4-nitrophenyl)pyrano[2ꢀ
,3ꢀ:5,6]chromeno[4,3-c]isoxazol-8(4H)-one (5c)
Light brown color solid, yield 65%; m.p. 295–296◦C. IR
(KBr, cm−1):1630(C=O). 1HNMR(400MHz, CDCl3)2.31
(s, 3H, CH3), 5.42 (s, 2H, O-CH2), 7.11 (d, J= 8.70Hz,
1H, Ar–H), 7.56 (m, 4H, Ar–H), 8.29 (m, 2H, Ar–H) ppm.
13CNMR(100MHz, DMSO-d6) δ 12.1, 63.4, 102.7, 110.3,
115.8, 116.6, 116.8, 128.4, 128.6, 129.0, 129.4, 130.1, 132.5,
148.9, 152.7, 159.9, 160.2, 177.5 ppm. ESI-MS: m/z 377
[M + H]+. Anal. calcd. for C20H12N2O6: C, 63.83; H, 3.21;
N, 7.44%. Found: C, 64.01; H, 3.31; N, 7.24%.
4-Oxo-2-phenyl-7-(prop-2-ynyloxy)-4H-chromene-8-carbal-
dehydes 3a and 3d (1.0mmol) were dissolved in 50mL
of ethanol, orthophenylenediamine (OPDA) (1.0mmol) was
added, and 4–5 drops of acetic acid were added and the
resulting solution was stirred at 80◦C for 4h. The sol-
vent was evaporated, and ice-cold water was added. The
obtainedprecipitatewasfilteredandpurifiedbycolumnchro-
matography using ethyl acetate/hexane (9:2) to get 8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-7-(prop-2-ynyloxy)-4H
-chromen-4-ones 6a and 6d.
10-Phenylpyrano[2ꢀ,3ꢀ:5,6]chromeno[4,3-c]isoxazol-8(4H)-
one (5d)
8-(1H-Benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-7
-(prop-2-ynyloxy)-4H-chromen-4-one (6a)
Light brown color solid, yield 69%; m.p. 297–298◦C. IR
1
(KBr, cm−1): 1633 (C=O). H NMR (400MHz, CDCl3)δ
5.39 (s, 2H, O-CH2), 6.71 (s, 1H, Ar–H), 7.07 (d, J =
8.70Hz, 1H, Ar–H), 7.57 (m, 5H, Ar–H), 8.30 (m, 2H, Ar–
H) ppm. 13C NMR (100MHz, DMSO-d6) δ 65.2, 102.7,
110.3, 115.8, 116.6, 116.8, 128.4, 128.6, 129.0, 129.4, 130.1,
132.5, 148.9, 152.7, 159.9, 160.2, 176.3 ppm. ESI-MS: m/z
318 [M + H]+. Anal. calcd. for C19H11NO4: C, 71.92; H,
3.49; N, 4.41%. Found: C, 72.32; H, 3.38; N, 4.30%.
Light brown color solid, yield 79%; m.p. 260–261◦C. IR
(KBr, cm−1): 3086 (NH), 1717 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.16 (s, 3H, CH3), 2.57 (s, 1H, CH), 4.84 (s, 2H,
CH2), 7.15–7.17 (d, J = 9.03Hz, 1H, Ar–H), 7.28–7.37 (m,
5H, Ar–H), 7.48 (s, 1H, Ar–H), 7.65–7.67 (m, 2H, Ar–H),
7.82 (s, 1H, Ar–H), 8.25 (d, J = 8.70Hz, 1H, Ar–H), 10.52
(s, 1H, NH) ppm. ESI-MS: m/z 407 [M + H]+.
123

Molecular Diversity
8-(1H-Benzo[d]imidazol-2-yl)-2-phenyl-7-(prop-2-ynyloxy)-
4H-chromen-4-one (6d)
111.1, 115.3, 116.9, 123.0, 126.4, 128.0, 128.7, 128.9, 130.4,
131.3, 131.6, 134.3, 138.9, 144.5, 152.9, 154.2, 160.4, 163.9,
177.8 ppm. ESI-MS: m/z 560 [M + H]+. Anal. calcd. for
C32H22N5O3Cl: C, 68.63; H, 3.96; N, 12.51%. Found: C,
69.83; H, 3.36; N, 12.93%.
Light brown color solid, yield 80%; m.p. 259–261◦C. IR
(KBr, cm−1): 3079 (NH), 1719 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.58 (s, 1H, CH), 4.85 (s, 2H, CH2), 6.84 (s, 1H,
Ar–H), 7.14–7.16 (d, J = 9.03Hz, 1H, Ar–H), 7.31–7.39
(m, 5H, Ar–H), 7.51 (s, 1H, Ar–H), 7.62–7.64 (m, 2H, Ar–
H), 7.84 (s, 1H, Ar–H), 8.30 (d, J = 8.70Hz, 1H, Ar–H),
10.61 (s, 1H, NH) ppm. ESI-MS: m/z 393 [M + H]+
7-((1-m-Toulyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-chromen-4-
one (7c)
General procedure for the synthesis of
7-((1-alkyl/aryl-1H -1,2,3-triazol-4-yl)methoxy)-8-(1H
-benzo[d ]imidazol-2-yl)-2-phenyl-4H
-chromen-4-ones (7a–t)
Light brown color solid, yield 79%; m.p. 236–237◦C. IR
(KBr, cm−1): 3086(NH), 1739 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.09 (m, 6H, CH3), 5.52 (s, 2H, CH2), 7.31–
7.71(m, 16H, Ar–H), 8.80 (s, 1H, NH) ppm. 13C NMR
(100MHz, DMSO-d6) δ 12.0, 24.3, 72.6, 104.3, 109.5,
8-(1H-Benzo[d]imidazol-2-yl)-2-phenyl-7-(prop-2-ynyloxy)- 111.1, 115.3, 116.9, 123.0, 124.3, 126.4, 126.9, 128.0, 128.4,
4H-chromen-4-ones 6a and 6d (1mmol) and the correspond-
ing alkyl or aryl azides (1mmol) were dissolved in 8mL
of DMF. The reaction mixture was stirred at room tem-
perature for 10min, and then CuSO4 · 5H2O (1mmol) and
sodium ascorbate (0.2mmol) were added. The reaction mix-
turewasstirredatroomtemperatureuntilthestartingmaterial
was consumed as judged by TLC analysis. The precipitate
was filtered, dried and purified by column chromatogra-
phy to give the products 7-((1-alkyl/aryl-1H-1,2,3-triazol-4-
yl)methoxy)-8-(1H-benzo[d]imidazol-2-yl)-2-phenyl- 4H-
chromen-4-ones 7a–t as light brown solids with 60–80%
yield.
128.7, 130.4, 131.6, 138.4, 138.9, 144.5, 152.9, 154.2, 160.2,
163.9, 177.6 ppm. ESI-MS: m/z 540 [M + H]+. Anal. calcd.
for C33H25N5O3: C, 73.43; H, 4.67; N, 12.98%. Found: C,
74.63; H, 4.45; N, 12.32%.
7-((1-(3-Nitrophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-chromen-4-
one (7d)
Light brown color solid, yield 78%; m.p. 226–228◦C. IR
(KBr, cm−1): 3097 (NH), 1623 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.09 (s, 3H, CH3), 5.67 (s, 2H, CH2), 7.19–7.95
(m, 12H, Ar–H), 8.32 (m, 3H, Ar–H), 8.65 (s, 1H, Ar–H),
9.10 (s, 1H, NH) ppm. 13C NMR (100MHz, DMSO − d6)δ
11.8, 72.4, 104.3, 109.5, 111.1, 115.3, 116.9, 121.0, 123.4,
124.0, 126.4, 128.0, 128.7, 129.6, 130.5, 131.6, 136.0, 138.9,
144.5, 148.0, 152.9, 154.2, 160.2, 163.9, 177.6ppm. ESI-
MS: m/z571 [M + H]+. Anal. calcd. for C32H22N6O5: C,
67.36; H, 3.89; N, 14.73. Found: C, 67.19; H, 3.93; N, 14.23.
7-((1-Phenyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-one (7a)
Light brown color solid, yield 80%; m.p. 240–242◦C. IR
(KBr, cm−1): 3086 (NH), 1739 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.07 (s, 3H, CH3), 5.50 (s, 2H, CH2), 7.50–7.79
(m, 17H, Ar–H), 8.87 (s, 1H, NH) ppm. 13C NMR (100MHz,
DMSO-d6) δ 13.8, 53.2, 102.5, 109.5, 110.5, 115.8, 116.4,
116.8, 117.8, 128.0, 128.4, 128.6, 128.8, 129.1, 129.3, 129.9,
130.5, 131.8, 132.3, 152.5, 152.8, 160.0, 177.1 ppm. ESI-
MS: m/z 526 [M + H]+. Anal. calcd. for C32H23N5 = O3:
C, 73.13; H, 4.41; N, 13.33%. Found: C, 72.79; H, 4.49; N,
13.67%.
7-((1-(3-Chlorophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-
(1H-benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-
chromen-4-one (7e)
Light brown color solid, yield 75%; m.p. 238–239◦C. IR
(KBr, cm−1): 3084 (NH), 1740 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.07 (s, 3H, CH3), 5.36 (s, 2H, CH2), 7.19 (s, 1H,
Ar–H), 7.53–7.79 (m, 15H, Ar–H), 8.87 (s, 1H, NH) ppm.
13C NMR (100MHz, DMSO−d6)δ 13.8, 72.3, 104.3, 109.5,
111.1, 115.3, 116.9, 123.0, 126.4, 128.0, 128.7, 128.9, 129.9,
130.2, 130.4, 131.6, 134.3, 138.8, 144.5, 152.9, 154.2, 160.2,
163.9, 177.6 ppm. ESI-MS: m/z 560 [M + H]+. Anal. calcd.
for C32H22N5O3Cl: C, 68.63; H, 3.96; N, 12.51%. Found:
C, 69.83; H, 3.36; N, 12.93%.
7-((1-(4-Chlorophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-
(1H-benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-
chromen-4-one (7b)
Light brown color solid, yield 75%; m.p. 239–240◦C. IR
(KBr, cm−1): 3084 (NH), 1740 (C=O). 1H NMR(400MHz,
CDCl3) δ 2.07(s, 3H, CH3), 5.36 (s, 2H, CH2), 7.19 (s,
1H, Ar–H), 7.53–7.79 (m, 15H, Ar–H), 8.87(s, 1H, NH)
ppm. 13C NMR (100MHz, DMSO-d6) δ 13.8, 52.7, 104.3,
123

Molecular Diversity
7-((1-(2,6-Dimethylphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-
8-(1H-benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-
chromen-4-one (7f)
CDCl3) δ 1.46–2.39 (m, 11H, Aliphatic-H), 3.71 (m, 1H,
CH), 5.08 (s, 2H, CH2), 6.85 (s, 2H, Ar–H), 7.29–7.95 (m,
6H, Ar–H), 8.29 (m, 3H, Ar–H), 8.68 (s, 1H, Ar–H), 9.12 (s,
1H, NH)ppm. 13CNMR(100MHz, DMSO−d6)δ 12.5, 25.7,
32.1, 62.8, 72.4, 104.3, 109.5, 111.1, 115.3, 116.8, 120.9,
123.0, 126.4, 128.0, 128.7, 130.1, 131.6, 138.9, 142.4, 152.9,
154.2, 160.2, 163.9, 178.2 ppm. ESI-MS: m/z 518 [M+H]+.
Anal. calcd. for C31H27N5O3: C, 71.94; H, 5.26; N, 13.53%.
Found: C, 72.03; H, 5.86; N, 13.12%.
Light brown color solid, yield 68%; m.p. 235–237◦C. IR
(KBr, cm−1): 3086 (NH), 1739 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.32 (m, 9H, CH3), 5.52 (s, 2H, CH2), 7.31–7.71
(m, 15H, Ar–H), 8.80 (s, 1H, NH) ppm. 13C NMR (100MHz,
DMSO-d6) δ 12.1, 15.9, 72.5, 104.3, 109.5, 111.1, 115.1,
116.9, 123.0, 126.1, 128.0, 128.6, 128.7, 129.7, 130.4, 131.6,
133.8, 138.9, 144.5, 152.9, 154.2, 160.2, 163.9, 177.6 ppm.
ESI-MS: m/z 554 [M + H]+. Anal. calcd. for C34H27N5O3:
C, 73.76; H, 4.92; N, 12.65%. Found: C, 74.04; H, 4.98; N,
12.40%.
7-((1-Hexyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-chromen-4-
one (7j)
Light brown color solid, yield 65%; m.p. 214–216◦C. IR
(KBr, cm−1): 3082 (NH), 1738 (C=O). 1H NMR (400MHz,
CDCl3) δ 1.46–2.39 (m, 14H, Aliphatic CH2), 3.71 (t,
J = 1.42Hz, 2H, CH2), 5.08 (s, 2H, CH2), 6.92 (s, 2H,
Ar–H), 7.29–7.95 (m, 6H, Ar–H), 8.29 (m, 3H, Ar–H), 8.68
(s, 1H, Ar–H), 9.12 (s, 1H, NH) ppm. 13C NMR (100MHz,
DMSO-d6) δ 12.5, 14.1, 22.8, 26.9, 28.4, 31.6, 52.5, 72.3,
104.3, 109.5, 111.1, 115.3, 116.8, 120.9, 123.0, 126.4, 128.0,
128.7, 130.4, 131.6, 138.9, 142.4, 152.9, 154.2, 160.2, 163.9,
178.1 ppm. ESI-MS: m/z 535 [M + H]+. Anal. calcd. for
C32H31N5O3:C, 72.03;H, 5.86;N, 13.13%. Found:C, 71.94;
H, 5.2 6; N, 13.52%.
7-((1-(4-Nitrobenzyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-chromen-4-
one (7g)
Light brown color solid, yield 72%; m.p. 216–218◦C. IR
(KBr, cm−1): 3097 (NH), 1623 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.09 (s, 3H, CH3), 5.00 (s, 2H, CH2), 5.87 (s,
2H, CH2), 7.19 (s, 2H, Ar–H), 7.67 (m, 5H, Ar–H), 7.95
(d, J = 8.92Hz, 3H, Ar–H), 8.32 (m, 6H, Ar–H), 9.09 (s,
1H, NH) ppm. 13C NMR (100MHz, DMSO − d6) δ 12.1,
57.0, 72.2, 104.3, 109.5, 111.1, 115.3, 116.8, 120.9, 121.0,
123.0, 126.4, 128.0, 128.7, 130.0, 130.4, 131.6, 138.9, 142.4,
145.2, 152.9, 154.3, 160.2, 163.9, 177.8 ppm. ESI-MS: m/z
585 [M + H]+. Anal. calcd. for C33H24N6O5: C, 67.80; H,
4.14; N, 14.38%. Found: C, 67.60; H, 4.40; N, 14.58%.
7-((1-Phenyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-one (7k)
Light brown color solid, yield 79%; m.p. 240–242◦C. IR
(KBr, cm−1): 3086 (NH), 1739 (C=O). 1H NMR (400MHz,
CDCl3) δ 5.50 (s, 2H, CH2), 6.71 (s, 1H, Ar–H), 7.50–7.79
(m, 17H, Ar–H), 8.87 (s, 1H, NH) ppm. 13C NMR (100MHz,
DMSO-d6) δ 72.4, 104.3, 109.5, 111.1, 115.3, 116.8, 120.9,
123.0, 126.4, 128.0, 128.7, 130.4, 131.6, 138.9, 142.4, 152.9,
154.2, 160.2, 163.9, 177.6 ppm.ESI-MS: m/z 512 [M+H]+.
Anal. calcd. for C31H21N5O3: C, 72.79; H, 4.14; N, 13.69%.
Found: C, 72.81; H, 4.49; N, 13.42%.
7-((1-(4-Fluorobenzyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-
(4,5-dihydro-1H-benzo[d]imidazol-2-yl)-3-methyl-2-
phenyl-4H-chromen-4-one (7h)
Light brown color solid, yield 71%; m.p. 213–215◦C. IR
(KBr, cm−1): 3097 (NH), 1623 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.39 (s, 3H, CH3), 5.28 (s, 2H, CH2), 5.68 (s, 2H,
CH2), 7.29 (m, 4H, Ar–H), 7.68 (m, 2H, Ar–H), 7.82 (m, 5H,
Ar–H), 8.01(m, 3H, Ar–H), 8.29 (s, 2H, Ar–H), 9.15 (s, 1H,
NH) ppm. 13C NMR (100MHz, DMSO-d6) δ 11.8, 57.0,
72.2, 104.3, 109.5, 111.1, 115.4, 115.6, 116.8, 120.9, 123.0,
126.4, 128.0, 128.7, 130.5, 130.7, 131.6, 138.9, 142.4, 152.9,
154.2, 159.9, 163.9, 177.6 ppm. ESI-MS: m/z 559 [M+H]+.
Anal. calcd. forC33H24N5O3F:C, 71.09;H, 4.34;N, 12.58%.
Found: C, 71.45; H, 4.25; N, 12.09%.
7-((1-(4-Chlorophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-
(1H-benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-
one (7l)
Light brown color solid, yield 76%; m.p. 225–227◦C. IR
(KBr, cm−1): 3084 (NH), 1740(C=O). 1H NMR (400MHz,
CDCl3) δ 5.55 (s, 2H, CH2), 6.67 (s, 1H, Ar–H), 7.19–
7.82 (m, 15H, Ar–H), 8.24 (s, 1H, Ar–H), 8.97 (s, 1H, NH)
ppm. 13C NMR (100MHz, DMSO-d6) δ 72.6, 104.5, 111.1,
115.3, 116.8, 116.9, 123.0, 126.4, 128.0, 128.5, 128.7, 130.4,
131.6, 138.9, 144.5, 152.9, 154.2, 163.7, 163.9, 176.9 ppm.
ESI-MS: m/z 547 [M+H]+. Anal. calcd. for C31H20N5O3Cl:
7-((1-Cyclopentyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-3-methyl-2-phenyl-4H-chromen-4-
one (7i)
Light brown color solid, yield 65%; m.p. 219–221◦C. IR
(KBr, cm−1): 3097 (NH), 1623 (C=O). 1H NMR (400MHz,
123

Molecular Diversity
C, 68.20; H, 3.69; N, 12.83%. Found: C, 68.96; H, 3.48; N,
12.61%.
1H, Ar–H), 7.31–7.71 (m, 15H, Ar–H), 8.80 (s, 1H, NH)
ppm. 13C NMR (100MHz, DMSO-d6) δ 15.9, 72.7, 104.5,
109.5, 111.1, 115.3, 116.8, 116.9, 123.0, 126.1, 126.4, 128.0,
128.6, 128.7, 129.7, 130.4, 131.6, 133.8, 138.9, 144.5, 152.9,
154.2, 163.7, 163.9, 177.7 ppm. ESI-MS: m/z 540 [M+H]+.
Anal. calcd. for C33H25N5O3: C, 73.46; H, 4.67; N, 12.98%.
Found: C, 74.04; H, 4.98; N, 12.40%.
7-((1-m-Toulyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-one (7m)
Light brown color solid, yield 78%; m.p. 231–232◦C. IR
(KBr, cm−1): 3086(NH), 1739(C=O). 1H NMR (400MHz,
CDCl3) δ 2.09 (m, 3H, CH3), 5.52 (s, 2H, CH2), 6.67 (s, 1H,
Ar–H), 7.31–7.71 (m, 16H, Ar–H), 8.80 (s, 1H, NH) ppm.
13C NMR (100MHz, DMSO-d6) δ 24.3, 72.8, 104.5, 109.5,
111.1, 115.3, 116.8, 116.9, 123.0, 124.3, 126.4, 126.9, 128.0,
128.4, 128.7, 129.1, 130.4, 131.6, 138.1, 138.9, 144.5, 152.9,
154.2, 163.7, 163.9, 178.7 ppm. ESI-MS: m/z 526 [M+H]+.
Anal. calcd. for C32H23N5O3: C, 73.13; H, 4.41; N, 13.33%.
Found: C, 73.91; H, 3.63; N, 13.48%.
7-((1-(4-Nitrobenzyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-one (7q)
Light brown color solid, yield 70%; m.p. 210–212◦C. IR
(KBr, cm−1): 3097 (NH), 1623 (C=O). 1H NMR (400MHz,
CDCl3) δ 5.00 (s, 2H, CH2), 5.65 (s, 2H, CH2), 6.71 (s, 1H,
Ar–H), 7.19–7.97 (m, 12H, Ar–H), 8.32 (m, 2H, Ar–H), 8.65
(s, 2H, Ar–H), 9.10 (s, 1H, NH) ppm. 13C NMR (100MHz,
DMSO-d6) δ 57.0, 71.8, 104.6, 109.5, 111.1, 115.3, 116.6,
120.9, 121.0, 123.0, 126.4, 128.0, 128.7, 130.0, 131.6, 138.9,
142.4, 145.4, 152.9, 154.2, 163.7, 163.9, 177.6 ppm. ESI-
MS: m/zm/z 571 [M + H]+. Anal. calcd. for C32H22N6O5:
C, 67.36; H, 3.89; N, 14.73%. Found: C, 67.45; H, 3.88; N,
14.53%.
7-((1-(3-Nitrophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-one (7n)
Light brown color solid, yield 77%; m.p. 226–228◦C. IR
(KBr, cm−1): 3097 (NH), 1623 (C=O). 1H NMR (400MHz,
CDCl3) δ 5.67 (s, 2H, CH2), 7.19–7.95 (m, 10H, Ar–H),
8.12 (m, 6H, Ar–H), 8.32 (s, 1H, Ar–H), 8.92 (s, 1H, NH)
ppm. 13C NMR (100MHz, DMSO-d6) δ 71.9, 104.5, 109.5,
111.1, 115.3, 116.8, 116.9, 121.1, 123.0, 124.0, 126.4, 128.0,
128.7, 129.4, 129.7, 130.4, 131.6, 138.9, 144.5, 148.0, 152.9,
154.2, 163.9, 178.2 ppm. ESI-MS: m/z 557 [M + H]+.
Anal. calcd. for C31H20N6O5: C, 66.90; H, 3.62; N, 15.13%.
Found: C, 66.32; H, 3.45; N, 15.50%.
7-((1-(4-Fluorobenzyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-
(1H-benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-
one (7r)
Light brown color solid, yield 69%; m.p. 213–215◦C. IR
(KBr, cm−1): 3083 (NH), 1645 (C=O). 1H NMR (400MHz,
CDCl3) δ 5.08 (s, 2H, CH2), 5.68 (s, 2H, CH2), 6.79 (s, 1H,
Ar–H), 7.29–7.95 (m, 12H, Ar–H), 8.29 (m, 2H, Ar–H), 8.68
(s, 2H, Ar–H), 9.12 (s, 1H, NH) ppm. 13C NMR (100MHz,
DMSO−d6) δ 57.0, 72.0, 104.3, 109.5, 111.1, 115.3, 115.4,
116.8, 120.9, 123.0, 126.4, 128.0, 128.7, 130.4, 130.7, 131.6,
138.9, 142.4, 152.9, 154.3, 159.9, 163.9, 178.6 ppm. ESI-
MS: m/z 544 [M + H]+. Anal. calcd. for C32H22N5O3F: C,
70.71; H, 4.08; N, 12.88%. Found: C, 70.95; H, 4.88; N,
12.38%.
7-((1-(3-Chlorophenyl)-1H-1,2,3-triazol-4-yl)methoxy)-8-
(1H-benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-
one (7o)
Light brown color solid, yield 76%; m.p. 223–225◦C. IR
(KBr, cm−1): 3084 (NH), 1740(C=O). 1H NMR (400MHz,
CDCl3) δ 5.36 (s, 2H, CH2), 6.94 (s, 2H, Ar–H), 7.49 (m,
6H, Ar–H), 7.92 (m, 5H, Ar–H), 8.32 (m, 3H, Ar–H), 8.87(s,
1H, Ar–H), 8.94 (s, 1H, NH) ppm.13C NMR (100MHz,
DMSO-d6) δ 72.0, 104.5, 109.5, 111.1, 115.3, 116.8, 116.9,
123.0, 125.4, 126.4, 128.0, 128.7, 128.9, 129.9, 130.4, 131.6,
134.3, 138.9, 144.5, 152.9, 154.2, 163.9, 177.8 ppm.ESI-MS:
m/z547 [M+H]+. Anal. calcd. for C31H20N5O3Cl: C, 68.20;
H, 3.69; N, 12.83. Found: C, 68.96; H, 3.48; N, 12.61.
7-((1-Cyclopentyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-one (7s)
Light brown color solid, yield 65%; m.p. 213–214◦C. IR
(KBr, cm−1): 3097 (NH), 1623 (C=O). 1H NMR(400MHz,
CDCl3) δ 1.46–2.39 (m, 8H, Aliphatic CH2), 3.71 (m, 1H,
CH), 5.08 (s, 2H, CH2), 6.87 (s, 2H, Ar–H), 7.29–7.95 (m,
6H, Ar–H), 8.29 (m, 3H, Ar–H), 8.68 (s, 2H, Ar–H), 9.12
(s, 1H, NH) ppm. 13C NMR (100MHz, DMSO-d6) δ 25.7,
32.1, 62.8, 72.1, 104.5, 109.5, 111.1, 115.3, 116.8, 120.9,
123.0, 126.4, 128.0, 128.7, 130.4, 131.6, 138.9, 142.4, 152.9,
154.2, 163.7, 163.9, 178.5 ppm. ESI-MS: m/z 504 [M+H]+.
Anal. calcd. for C30H25N5O3: C, 71.56; H, 5.00; N, 13.91%.
Found: C, 71.01; H, 5.02; N, 14.12%.
7-((1-(2,6-Dimethylphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-
8-(1H-benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-
one (7p)
Light brown color solid, yield 65%; m.p. 212–213◦C. IR
(KBr, cm−1): 3086 (NH), 1739 (C=O). 1H NMR (400MHz,
CDCl3) δ 2.32 (m, 6H, CH3), 5.52 (s, 2H, CH2), 6.69 (s,
123

Molecular Diversity
7-((1-Hexyl-1H-1,2,3-triazol-4-yl)methoxy)-8-(1H-
benzo[d]imidazol-2-yl)-2-phenyl-4H-chromen-4-one (7t)
aliquotwasaddedtotheeachwelltomakefinalconcentration
of compound 10µM. Each compound was tested in tripli-
cate. DMSO and doxorubicin (as standard control anti cancer
drug) were used as vehicle and positive controls, respectively.
After 48 h, the cells were fixed with 10% trichloroacetic acid
solution and incubated the plates at 4◦C for 1h after which
the plate was rinsed carefully with MQ water and air-dried
followed by the addition of 0.057% SRB solution and kept
for approx. 30min before it was washed off with 1% acetic
acid. The plates were then air-dried, and the absorbance was
measured at 510nm using a PerkinElmer Multimode Reader.
To measure the absorbance 100µL of 10mM unbuffered tris
base solution was added to each well to dissolve the SRB.
The measure of absorbance is proportional to cell growth;
the absorption data are used to obtain IC50 values.
Light brown color solid, yield 64%; m.p. 209–210◦C. IR
(KBr, cm−1): 3082 (NH), 1738 (C=O). 1H NMR (400MHz,
CDCl3) δ 1.46–2.39 (m, 11H, Aliphatic CH2), 3.75 (t, J =
1.42Hz, 2H, CH2), 5.08 (s, 2H, CH2), 6.87 (s, 2H, Ar–H),
7.29–7.95 (m, 6H, Ar–H), 8.29 (m, 3H, Ar–H), 8.68 (s, 2H,
Ar–H), 9.12 (s, 1H, NH) ppm. 13C NMR (100MHz, DMSO-
d6) δ 14.1, 22.8, 26.9, 28.4, 31.6, 52.5, 72.3, 104.5, 109.5,
111.1, 115.3, 116.5, 120.9, 123.0, 126.4, 128.0, 128.7, 130.4,
131.6, 138.9, 142.4, 152.9, 154.2, 163.7, 163.9, 178.9 ppm.
ESI-MS: m/z 535 [M + H]+. Anal. calcd. for C31H29N5O3:
C, 71.66; H, 5.63; N, 13.48%. Found: C, 71.16; H, 5.41; N,
13.98%.
Acknowledgements The authors are thankful to Vetindia pharmaceu-
ticals Ltd, Leavo chem. Laboratories for providing laboratory facilities
to carry out this work.
Biological activity
Antimycobacterial activity
References
The newly synthesized compounds were analyzed for their
antimycobacterial effect on
1. Serra H, Mendes T, Bronze MR, Simplício AL (2008) Prediction of
intestinal absorption and metabolism of pharmacologically active
flavones and flavanones. Bioorg Med Chem 16:4009–4018. https://
doi.org/10.1016/j.bmc.2008.01.028
2. Yao H, Kim SH, Lee J, Kim HJ, Seo SH, Chung BY, Jin C, Lee
YS(2005)Synthesisandantioxidantactivityof3-methoxyflavones.
Korean Chem Soc 26:2057–2060. https://doi.org/10.5012/bkcs.
2005.26.12.205
3. Balasuriya N, Vasantha Rupasinghe HP (2012) Antihyperten-
sive properties of flavonoidrich apple peel extract. Food Chem
135:2320–2325. https://doi.org/10.1016/j.foodchem.2012.07.023
4. Kawai M, Hirano T, Higa S, Arimitsu J, Maruta M, Kuwahara Y,
Ohkawara T, Hagihara K, Yamadori T, Shima Y, Ogata A, Kawase
I, Tanaka T (2007) Flavonoids and related compounds as anti-
allergic substances. Allergol Int 56:113–123. https://doi.org/10.
2332/allergolint.R-06-135
5. Orhan DD, Ozçelik B, Ozgen S, Ergun F (2010) Antibacterial,
antifungal, and antiviral activities of some flavonoids. Microbial
Res 165:496–504. https://doi.org/10.1016/j.micres.2009.09.002
6. Li JX, Xub B, Chai Q, Liu ZX, Zhao AP, Chan LB (2005)
Antihypertansive effect of total flavonoid fraction of Astragalus
complanatus in hypertensive rats. Chin J Physiol 48:101–106
7. Inoue T, Sugimoto Y, Masuda H, Kamei C (2002) Antiallergic
effect of flavonoid glycosides obtained from Mentha piperita L.
Biol Pharm Bull 25:256–259
Mycobacterium bovisstrain (BCG) using a turbidometric
assay. 20mMstocksolutionswerepreparedusing100%(v/v)
DMSO. The inoculum for the assay maintained in Middle-
brook 7H9 broth supplemented with 0.1% Tween 80 and
0.2% glycerol. At the time of inoculation 10% OADC was
added to the media and the culture was incubated in a shaker
incubator at 37◦C and 200rpm. The assay was conducted
in a 96-well microtiter plate; a 2µL aliquot of the 1.5mM
dilution of compound was added to each well in triplicate, to
which 98µL of inoculum dilution was added to make final
concentration of the compound to 30µM. To each plate a set
of controls was added to better ascertain the activity of the
compounds. These included DMSO which was taken as a
growth control, media control (Blank) as well as Rifampicin
which was taken as positive control of inhibition. After the
completion of the incubation period, the absorbance of the
inoculum in wells was measured at 600nm using a Mul-
tiMode Reader (Perkin Elmer). Percentage inhibition was
determined against DMSO.
8. Havsteen BH (2002) The biochemistry and medical significance of
the flavonoids. Pharmcol Ther 96:67–202. https://doi.org/10.1016/
S0163-7258(02)00298-X
Antiproliferative activity
9. Zhu Z-Y, Wang W-X, Wang Z-Q, Chen L-J, Zhang J-Y, Liu X,
Shao-ping W, Zhang Y (2014) Synthesis and antitumor activity
evaluation of chrysin derivatives. Eur J Med Chem 75:297–300.
https://doi.org/10.1016/j.ejmech.2013.12.044
10. Cotelle N, Jl B, Catteau JP, Pommery J, Wallet JC, Gaydou EM
(1996) Antioxidant properties of hydroxy-flavones. Free Radical
Bio Med 20:35–43
11. Manjinder S, Maninder KS (2014) Flavones: an important scaffold
for medicinal chemistry. Eur J Med Chem 84:206–239. https://doi.
org/10.1016/j.ejmech.2014.07.013
The cytotoxicity of the compound was tested by carrying
out a Sulforhodamine B (SRB) Assay. The MCF-7 cell line
was seeded in to a clear flat bottom 96-well plate (5000
cells/100µL) in a medium supplemented with 10% serum
and allowed to incubate for 18–20 h. To ensure the proper
adherence of the cells to the surface bottom of the wells,
incubator was continuously supplied with 5% CO2. Vari-
able dilutions of the compounds were prepared, and 2µL
123

Molecular Diversity
12. Maheep K, Sharma N, Mahabeer PD, Yogesh CJ (2011)
Flavonoids: a versatile source of anticancer drugs. Pharmacogn
Rev 5:1–12. https://doi.org/10.4103/0973-7847.79093
13. Garudachari B, Isloor AM, Satyanarayana MN, Fun HK, Hegde G
(2014) Click chemistry approach: tegioselective one-pot synthesis
of some new 8-trifluoromethylquinoline based 1,2,3-triazoles as
potent antimicrobial agents. Eur J Med Chem 74:324–332. https://
doi.org/10.1016/j.ejmech.2014.01.008
14. Bakunov SA, Bakunova SM, Wenzler T, Ghebru M, Werbovetz
KA, Brun R, Tidwell RR (2010) Synthesis and antiprotozoal
activity of cationic 1,4-diphenyl-1H-1,2,3-triazoles. J Med Chem
53:254–272. https://doi.org/10.1021/jm901178d
15. Wuest F, Tang X, Kniess T, Pietzsch J, Suresh M (2009)
Synthesis and cyclooxygenase inhibition of various (aryl-1,2,3-
triazole-1-yl)-methanesulfonylphenyl derivatives. Bioorg Med
Chem 17:1146–1151. https://doi.org/10.1016/j.bmc.2008.12.032
16. Somu RV, Boshoff H, Qiao C, Bennett EM, Barry CE, Aldrich
CC (2006) Rationally designed nucleoside antibiotics that inhibit
siderophore biosynthesis of Mycobacterium tuberculosis. J Med
Chem 49:31–34. https://doi.org/10.1021/jm051060o
21. KumarR, ShaharYarM, ChaturvediS, SrivastavaA(2013)Triazole
as pharmaceuticals potentials. Int J Pharm Tech Res 5:1844–1869
22. Naseem A, Naveen Kumar K, Sarfaraz A, Mohammad O (2014)
Design, synthesis and antiproliferative activity of functionalized
flavone-triazole-tetrahydropyran conjugates against human cancer
cell lines. Eur J Med Chem 82:552–564. https://doi.org/10.1016/j.
ejmech.2014.06.009
23. Khokra SL, Choudhary D (2011) Benzimidazole an important scaf-
fold in drug discovery. Asian J Bio Chem Pharm Res 1:476–480
24. Gurvinder S, Maninderjit K, Mohan C (2013) Benzimidazoles. The
latest information on biological activities. Int Res J Pharm 4:82–87
25. Ajay Kumar K, Jayaroopa P (2013) Isoxazoles: molecules with
potential medicinal properties. Int J Pharm Chem Biol Sci 3:294–
304
26. Vorobyeva DV, Natalya M, Karimova IL, Odinets G-VR,
Osipov SN (2011) Click-chemistry approach to isoxazole-
containing α-CF3-substituted α-amino carboxylates and α-
aminophosphonates. Org Biomol Chem 9:7335–7342. https://doi.
org/10.1039/C1OB06040F
27. Angelika S, Boz˙ena OM (2017) Isoxazole ring as a useful scaffold
in a search for new therapeutic agents. Eur J Med Chem 137:292–
309. https://doi.org/10.1016/j.ejmech.2017.06.002
28. Thirupathi G, JayaprakashRao Y (2016) Synthesis of diverse
oxa-carbocycle annulated flavones using the combined Claisen
rearrangement and ring-closing metathesis. Helv Chim Acta
99:547–557. https://doi.org/10.1002/hlca.201600028
29. Thirupathi G, Yadaiahgoud E, Hemasri Y, JayaprakashRao Y
(2017) A tandem synthesis of 3-aroylcoumarinoflavones catalyzed
byL-prolineandtheirantioxidantactivity. JIranChemSoc14:477–
483. https://doi.org/10.1007/s13738-016-0995-7
30. Lee YR, Morehand AT Jr (1995) A new route for the synthesis of
furanoflavone and furanochalcone natural products. Tetrahedron
51:4909–4922. https://doi.org/10.1016/0040-4020(95)98689-F
31. Tsueneo S, Takaaki H, Takahachi S, Teishiro A (1983) Benzofuran
derivatives. I. On the effects of substituents in benzofuran synthe-
ses. Bull Chem Soc Jpn 56:2762–2767. https://doi.org/10.1246/
bcsj.56.2762
17. Wang XL, Wan K, Zhou CH (2010) Synthesis of novel
sulfanilamide-derived 1,2,3-triazoles and their evaluation for
antibacterial and antifungal activities. Eur J Med Chem 45:4631–
4639. https://doi.org/10.1016/j.ejmech.2010.07.031
18. Kamal A, Prabhakar S, Ramaiah MJ, Reddy PV, Reddy CR,
Mallareddy A, Shankaraiah N, Narayan Reddy TL, Pushpavalli
SNGVL, Bhadra M (2011) Synthesis and anticancer activity
of chalcone-pyrrolobenzodiazepine conjugates linked via 1,2,3-
triazole ring side-armed with alkane spacers. Eur J Med Chem
46:3820–3831. https://doi.org/10.1016/j.ejmech.2011.05.050
19. Chan DCM, Laughton CA, Queener SF, Stevens MFG (2002)
Structural studies on bioactive compounds. Part 36: design, synthe-
sis and biological evaluation of pyrimethamine-based antifolates
against PneumoCystis carinii. Bioorg Med Chem 10:3001–3010.
https://doi.org/10.1016/S0968-0896(02)00128-1
20. Jordao AK, Afonso PP, Ferreira VF, De Souza MC, Almeida MC,
Beltrame CO, Paiva DP, Wardell SM, Wardell JL, Tiekink ER,
Damaso CR, Cunha AC (2009) Antiviral evaluation of N-amino-
1,2,3-triazoles against Cantagalo virus replication in cell culture.
Eur J Med Chem 44:3777–3783. https://doi.org/10.1016/j.ejmech.
2009.04.046
123