Synthesis of N-substituted indole derivatives as potential antimicrobial and antileishmanial agents

Article abstract of DOI:10.1016/j.bioorg.2020.103787

Leishmaniasis and microbial infections are two of the major contributors to global mortality and morbidity rates. Hence, development of novel, effective and safer antileishmanial and antimicrobial agents having reduced side effects are major priority for researchers. Two series of N-substituted indole derivatives i.e. N-substituted indole based chalcones (12a-g) and N-substituted indole based hydrazide-hydrazones (18a-g, 19a-f, 21 a-g) were synthesized. The synthesized compounds were characterized by ¹H NMR, ¹³C NMR, Mass and FT-IR spectral data. Further these derivatives were evaluated for their antimicrobial potential against Escherichia coli, Bacillus subtilis, Pseudomonas putida and Candida viswanathii, and antileishmanial potential against promastigotes of Leishmania donovani. Compounds 18b, 18d and 19d exhibited significant activity with an IC₅₀ of 0.19 ± 0.03 μM, 0.14 ± 0.02 μM and 0.16 ± 0.06 μM against B. subtilis which was comparable to chloramphenicol (IC₅₀ of 0.25 ± 0.03 μM). Compounds 12b and 12c exhibited an IC₅₀ of 24.2 ± 3.5 μM and 21.5 ± 2.1 μM in the antileishmanial assay. Binding interactions of indole based hydrazide-hydrazones were studied with nitric oxide synthase in silico in order to understand the structural features responsible for activity.

Full text of DOI:10.1016/j.bioorg.2020.103787

Journal Pre-proofs
Synthesis of N-substituted indole derivatives as potential antimicrobial and
antileishmanial agents
Shweta Tiwari, Seema Kirar, Uttam Chand Banerjee, Neerupudi Kumar Balu,
Sushma Singh, Aabid Abdullah Wani, Prasad V. Bharatam, Inder Pal Singh
PII:
S0045-2068(19)32126-1
DOI:
https://doi.org/10.1016/j.bioorg.2020.103787
YBIOO 103787
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
12 December 2019
24 February 2020
21 March 2020
Please cite this article as: S. Tiwari, S. Kirar, U. Chand Banerjee, N. Kumar Balu, S. Singh, A. Abdullah Wani,
P.V. Bharatam, I. Pal Singh, Synthesis of N-substituted indole derivatives as potential antimicrobial and
antileishmanial agents, Bioorganic Chemistry (2020), doi: https://doi.org/10.1016/j.bioorg.2020.103787
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Synthesis of N-substituted indole derivatives as potential antimicrobial and
antileishmanial agents
a
b
b
c
c
d
Shweta Tiwari , Seema Kirar , Uttam Chand Banerjee , Neerupudi Kumar Balu , Sushma Singh , Aabid Abdullah Wani ,
d
a*
Prasad V. Bharatam , Inder Pal Singh
aDepartment of Natural Products, National Institute of Pharmaceutical Education and Research (NIPER), Sector-67,
S.A.S. Nagar, Punjab 160062, India
b
Department of Pharmaceutical Technology Biotechnology, National Institute of Pharmaceutical Education and Research
(
NIPER), Sector-67, S.A.S. Nagar, Punjab 160062, India
c
Department of Biotechnology, National Institute of Pharmaceutical Education and Research (NIPER), Sector-67, S.A.S.
Nagar, Punjab 160062, India
d
Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector-67,
S.A.S. Nagar, Punjab 160062, India
Corresponding author:
E-mail address: ipsingh@niper.ac.in (I.P. Singh)
1

Abstract
Leishmaniasis and microbial infections are two of the major contributors to global mortality
and morbidity rates. Hence, development of novel, effective and safer antileishmanial and
antimicrobial agents having reduced side effects are major priority for researchers. Two
series of N-substituted indole derivatives i.e. N-substituted indole based chalcones (12a-g)
and N-substituted indole based hydrazide-hydrazones (18a-g, 19a-f, 21 a-g) were
1
13
synthesized. The synthesized compounds were characterized by H NMR, C NMR, Mass
and FT-IR spectral data. Further these derivatives were evaluated for their antimicrobial
potential against Escherichia coli, Bacillus subtilis, Pseudomonas putida and Candida
viswanathii, and antileishmanial potential against promastigotes of Leishmania donovani.
Compounds 18b, 18d and 19d exhibited significant activity with an IC of 0.19±0.03 µM,
5
0
0
.14±0.02 µM and 0.16±0.06 µM against B. subtilis which was comparable to
chloramphenicol (IC of 0.25±0.03 µM). Compounds 12b and 12c exhibited an IC of
5
0
50
2
4.2±3.5 µM and 21.5±2.1 µM in the antileishmanial assay. Binding interactions of indole
based hydrazide-hydrazones were studied with nitric oxide synthase in silico in order to
understand the structural features responsible for activity.
Keywords: Antileishmanial activity, Antimicrobial activity, Chalcones, Indole, Hydrazide-
hydrazones
2

1
. Introduction
Infectious diseases are among the major contributors to global mortality and morbidity rates,
especially in the immunocompromised individuals, those suffering from tuberculosis, cancer
or AIDS.[1,2] They also lead to longer hospitalization and increased healthcare costs. Fungal
and bacterial infections constitute larger proportion of the infectious diseases resulting in
1
.5 million deaths each year worldwide.[3,4] Although a number of antimicrobial drugs are
available in the market, the ability of microbes to develop mutant strains, emergence of drug
resistance, lack of specificity of the drugs and narrow spectrum are major hindrances in
current microbial therapy.[5,6] Currently, there is stagnation in the development of new
antimicrobial drugs, hence, the development of more efficacious, safe and target specific
new antimicrobial agents is an issue of current medicinal importance. Despite a number of
antimicrobial agents being reported, new compounds are continually required to meet the
increasing demands of managing infections in the complex patient populations.
Leishmaniasis is a fatal, neglected and poverty associated disease caused by obligate
intracellular protozoa belonging to the genus Leishmania and transmitted to humans by
different species of phlebotomine sandflies.[7,8,9] Leishmaniasis is found in at least 88
countries, being more prevalent in underdeveloped or developing countries. According to
the World Health Organization (WHO) estimations, 90% of global visceral leishmaniasis
(VL) cases occur in 6 countries:ꢀBangladesh, Brazil, Ethiopia, India, South Sudan, and
Sudan. The estimated number of new cases per year may have decreased to <100,000, but
previous estimates ranged up to 400,000 or more cases with over 20,000 deaths.[10] There
are no vaccines or prophylactic drugs available in the market against any form of
Leishmaniasis thus, the management of the disease depends mainly on
chemotherapy.[11] Unfortunately, currently available drug therapy for treatment of
leishmaniasis suffers from a number of drawbacks such as high cost, toxicity of the drugs
and cases of emerging drug resistance.[12,13] In light of the above, the development of new,
efficient and safer antileishmanial agents is urgently needed.
The concept of hybridization is an appealing approach in medicinal chemistry as it generates
new scaffolds with fascinating biological profile that can be more useful in the treatment of
various physicopathologies. Here, distinct pharmacophores are covalently linked into a
single chemical moiety so as to produce a new hybrid compound with improved efficacy
and safety profile. Our present work entails the synthesis of compounds containing indole
and chalcone subunits as well as indole, coumarin and hydrazide-hydrazone subunits. These
3

pharmacophores have been reported to exhibit potential antimicrobial as well as
antileishmanial activity. Indolmycin (1), an antibacterial drug produced by bacterial strains
from both terrestrial and marine environments, such as Streptomyces griseus ATCC12648
and Pseudoalteromonas luteoviolacea was reported to exhibit potent antibacterial activity
against human pathogens, such as Helicobacter pylori, and methicillin-
resistant Staphylococcus aureus (MRSA). It displayed MIC of 0.25 and 0.5 mg/L against
5
0
methicillin-sensitive Staphylococcus aureus (MSSA) and MRSA respectively.[14]
Umbelliprenin (2) and osthol (3), sesquiterpene prenylated coumarins isolated from flowers
of Magydaris tomentosa exhibited MIC of 32 and 64 µg/mL against Gram positive bacteria,
S. epidermidis.[15] Nowakowska et al. synthesized a series of (E)-4-piperidino-N-
alkylthiochalcones and tested them for their antimicrobial potential. Amongst them,
compound 4 exhibited good antimicrobial activity against S. aureus and B. subtilis with MIC
value of 26 µg/mL.[16] Ozkay et al. synthesized a series of compounds bearing hydrazone
moiety and amongst them, compounds 5 and 6 had bactericidal effect on the growth of
Salmonella typhimurium, two times better (compound 5: MIC of 6.25 μg/mL) or equal
(compound 6: MIC of 12.5 μg/mL) to the activity of chloramphenicol (MIC of 12.5 μg/mL),
which was used as positive control.[17]
These scaffolds have also been well reported for their antileishmanial potential. An indole
alkaloid corynantheine (7), present in the bark of Corynanthe pachyceras (Rubiaceae)
exhibited antileishmanial activity against Leishmania major promastigotes with an IC50
value of about 3 μM.[18] Compounds 2 and 3 showed significant activity with IC value of
5
0
1
3.3 μM and 10.79 µg/mL against promastigotes of L. major.[19,20] Kharazmi et al. reported
that Licochalcone A (8), an oxygenated chalcone, exhibited IC value of 2.7 μM against L.
5
0
donovani promastigotes.[21] Taha et al. synthesized a library of Schiff bases of 2-
methoxybenzoyl hydrazides, compound 9 having 2-hydroxy-4-methoxy substituents at ring
[22]
A showed excellent activity against L. donovani promastigotes (IC of 1.95±0.04 μM).
5
0
4

O
NH
O
N
O
O
O
N
O
O
O
H
2
3
1
O
R
N
HN N
(
CH2)
N
5
N
O
S
H
4
5
6
: R = Cl;
: R = Br;
Figure 1. Various compounds reported for antimicrobial activity.
N
H
HO
OH
O
N
H
O
O
COOCH3
OCH3
H
H
N
H
N
H
H
O
O
OH
7
8
9
Figure 2. Various compounds reported for antileishmanial activity.
As the aforementioned scaffolds have exhibited favorable response as antimicrobial and
antileishmanial agents, it was envisaged that the synthesis of their hybrids is worth the
attempt. Therefore, these pharmacophores were subjected to structural modifications to
synthesize hybrid molecules and investigate them for their antimicrobial and antileishmanial
potency.
Herein, we report the synthesis and biological evaluation of two series of N- substituted
indole derivatives i.e. indole based chalcones and indole based hydrazide-hydrazones as
antimicrobial and antileishmanial agents.
2
2
2
. Results and Discussion
.1 Chemistry
.1.1. Synthesis of N-substituted indole chalcones
The synthesis of targeted hybrids was achieved as shown in Scheme 1. The synthesis of N-
substituted indole-3 carbaldehyde intermediate (11) was achieved by using commercially
available indole-3-carbaldehyde (10) and 3-dimethylamino-1-propyl chloride hydrochloride
as alkylating agent in the presence of cesium carbonate and potassium iodide as base.[23]
Subsequent base catalysed Claisen-Schmidt condensation of compound 11 with various
substituted acetophenones was tried using different reaction conditions as enlisted in Table
5

1
. In most of the cases, the results were unsatisfactory. The expected product was either not
formed or formed in very low yield (2-10%). The desired product was formed in 29-40%
ᵒ
yield with the use of 10% aq. NaOH in methanol as solvent at temperature of 70-80 C.
Table 1. Different reaction conditions tried for synthesis of N-substituted indole chalcones
Reagent/Solvent
Reaction conditions
Yield (%)
Piperidine, methanol
Piperidine, methanol
rt, 24-48 h
60-65 C, 24-48 h
rt, 24-48 h
rt, 72 h
0
5-10
0
ᵒ
Li(OH)
2
.H
2
O, ethanol
KOH, dioxane
0
1
1
0% aq. NaOH, ethanol/methanol
0% aq. NaOH, ethanol/methanol
rt, 72 h
70-80 C, 3-7 h
2-5
29-40
ᵒ
It was observed that the nature of the substituent present on the phenyl ring had no significant
effect on the yield of reaction but affected the rate of reaction. Compounds 12b and 12c
bearing electron withdrawing substituents on the phenyl ring were completed in a shorter
span of time as compared to compounds with electron donating substituents.
R1
O
H
O
O
O
H
Cl
N
.HCl
R
N
N
R
N
Cs CO , KI, dry CH CN
10 % NaOH, MeOH
70- 80 °C, 3-7 h
2
3
3
H
83 °C, 28 h, N2,
(yield 29-40 %)
(yield 87-89 %)
12a-g
11
N
N
1
0
Scheme 1. Synthesis of N-substituted indole chalcones
Table 2. Synthesized derivatives using scheme 1
Compound
R
R
1
Time
h)
Yield (%)
(
1
1
1
1
1
1
1
2a
2b
2c
2d
2e
2f
4-NH
4-I
4-Cl
4-OH
2,4-di-OCH
3,4-di-OCH
4-NH
2
H
H
H
H
H
H
4
3
3.5
6.5
7
37
36
33
29
32
35
40
3
3
7
5
2g
2
Br
All the derivatives (12a-g) showed C=O stretching absorption band in the region of 1700-
−
1
1
600 cm in IR spectra. In compounds 12d, 12e and 12f the olefinic protons (α and β) were
observed at chemical shifts of δ 7.58-7.60 and δ 7.94-8.06, respectively. The α-proton of
double bond was merged with other aromatic protons in compounds 12b and 12c. Coupling
1
constants > 15 Hz in H NMR revealed the presence of trans olefinic protons.
2
.1.2. Synthesis of N-substituted indole hydrazide-hydrazones
6

As shown in Scheme 2, 7-hydroxy coumarin (13) and 4-hydroxy coumarin (15) were reacted
with 1,2-dibromoethane and 1,3-dibromopropane to yield 7-bromoalkoxy (14) and 4-
bromoalkoxy (16) coumarin as per the reported method.[24] The compounds 14 and 16 were
reacted with indole-3 carbaldehyde (10) in presence of cesium carbonate and dry DMF to
give compounds 17 and 20, respectively, which were further reacted with various substituted
benzhydrazides. For the reaction of compounds 17 and 20 with various substituted
benzhydrazides, different reaction conditions were tried as shown in Table 3.
Table 3: Optimization of conditions for synthesis of N-substituted indole-3 hydrazide-hydrazones
Reagent/Solvent
Ethanol
Ethanol, glacial acetic acid (cat. amt)
Ethanol, conc. HCl
Glacial acetic acid
DMSO
Reaction condition
Yield (%)
0
0
0
ᵒ
80-90 C, 24h
ᵒ
80-90 C, 24h
ᵒ
80-90 C, 12 h
ᵒ
110-120 C, 30 min
0
ᵒ
110 C, 3-6 h
46-63
The reaction of N-substituted 3-carbaldehyde (17 and 20) with various substituted
benzhydrazides in the presence of DMSO as solvent gave the desired product in good to
moderate yield. To the best of our knowledge, there are no earlier reports on the synthesis
of hydrazide-hydrazones using DMSO as solvent. It was observed that in case of compounds
possessing 4-alkoxy coumarin substituent on the indole ring, the rate of reaction was slow
and the yield was low as compared to compounds bearing 7-alkoxy coumarin substituent.
The length of alkyl linker didn’t have any significant effect on the rate as well as yield of
the reaction. The reaction time of 3-6 h was found to be optimum and the increase in reaction
time didn’t have any significant effect on the yield of reaction.
All the derivatives (18a-g, 19a-f, 21a-g) showed NH stretching absorption band in the region
−
1
1
of 3300–3100 cm in IR spectra and NH proton signal in the range of 11–12 ppm in H
NMR spectra. Apart from this, imine proton CH=N was observed in the range of 8–9 ppm
1
in H NMR spectra.
1
13
All the synthesized compounds were confirmed using H NMR, CNMR, mass and IR
spectral data. Percentage purity of all synthesized compounds were determined using HPLC
and observed at their respective λmax values (found to be >95%).
7

BrCH2CH2Br
or
BrCH2CH2CH2Br
Br
O
O
O
n
HO
O
O
CH3CN, 60-80 °C, 12-14 h
(Yield 64-69 %)
14a: n = 2
14b: n = 3
13
Br
OH
O
nO
BrCH2CH2Br
CH3CN, 60-80 °C, 18 h
O
O
O
(Yield 58 %)
1
5
1
6: n = 2
R
HN
N
O
O
Substituted
benzhydrazides
O
H
Cs2CO3,dry DMF,
0 °C, 14-16 h
H
4
Br
O
O
O
n
DMSO, 110 °C, 3-4 h,
(yield 36-64 %)
N
N
N
(Yield 51-57 %)
H
n
1
1
4a: n = 2
4b: n = 3
n
O
O
1
0
O
O
O
O
1
1
7a: n = 2
7b: n = 3
18a-g (n = 2)
19a-f (n = 3)
Br
R
HN
N
O
O
O
O
O
H
H
Cs CO ,dry DMF,
Substituted
benzhydrazides
2
3
40 °C, 16 h
O
N
O
N
N
(Yield 49 %)
DMSO, 110 °C, 4-6 h,
yield 20-35 %)
H
(
1
6
1
0
O
O
O
O
O
21a-g
20
Scheme 2. Synthesis of N-substituted indole based hydrazide-hydrazones.
8

R
O
HN
N
O
O
R =
O
1
8a
18b
(36%)
18c
(63%)
1
8d
N
(
49%)
(
64%)
O
O
O
1
8f
18g
(51%)
1
8e
(
54%)
(
62%)
O
18a-g
R
HN
N
O
O
R =
O
O
1
9a
19b
(52%)
19c
(57%)
19d
(55%)
N
(
49%)
O
O
19e
19f
O
(39%)
(36%)
19a-f
R
O
HN
N
O
O
R =
O
2
1a
21b
(32%)
21c
(35%)
21d
(25%)
N
(
29%)
O
O
O
O
2
1g
2
1e
21f
(21%)
(
39%)
21a-g
(22%)
2
.2 In vitro evaluation for antimicrobial activity
The synthesized compounds were tested for in vitro antimicrobial activity against two Gram
negative strains (Escherichia coli 443, Pseudomonas putida 1237), one Gram positive strain
(Bacillus subtilis 1427) and one fungus (Candida viswanathii 5158) using colony counting
method.[25] Chloramphenicol was used as a positive control. The results obtained are shown
in Table 4.
9

Table 4. In vitro antimicrobial activity of indole derivatives represented as IC (µM)
5
0
Compound
E. coli
MTCC 443
P. putida
MTCC 1237
B. subtilis
MTCC 1427
C. viswanathii
MTCC 5158
1
1
1
1
1
1
1
1
2a
2b
2c
2d
2e
2f
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
0.46±0.03
0.76±0.06
0.81±0.15
0.56±0.12
0.25±0.09
0.21±0.06
0.69±0.13
0.35±0.17
0.19±0.03
0.39±0.09
0.14±0.02
0.44±0.07
0.34±0.16
0.28±0.06
0.81±0.03
0.50±0.05
0.38±0.11
0.16±0.06
0.21±0.08
0.39±0.02
NI
0.50±0.06
0.21±0.02
0.18±0.07
0.55±0.05
0.62±0.01
0.38±0.07
0.26±0.06
0.45±0.08
0.52±0.05
0.56±0.01
NI
NI
0.22±0.03
2g
8a
NI
NI
NI
NI
1
1
1
1
8b
8c
8d
8e
8f
NI
NI
0.19±0.06
0.45±0.18
NI
NI
0.36±0.04
NI
NI
NI
NI
NI
NI
0.34±0.04
NI
1
1
1
8g
9a
0.74±0.07
0.23±0.03
0.72±0.08
0.22±0.05
0.56±0.01
0.48±0.05
NI
0.45±0.06
0.69±0.09
NI
NI
NI
0.65±0.08
0.57±0.05
0.23±0.07
NI
NI
NI
1
9b
9c
9d
9e
9f
1a
1b
1c
1d
1e
1f
1g
Chloramphenicol
1
1
1
1
0.28±0.03
0.64±0.07
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
NI
2
2
2
2
2
2
2
NI
0.41±0.07
NI
0.58±0.04
NI
NI
0.21±0.06
0.23±0.05
0.25±0.02
IC50-Concentration showing 50% inhibition (µM); NI-No inhibition up to 4 µM
The
results indicate that the compounds were active against Gram positive bacteria (B. subtilis).
The highest activity was shown by the compound 18d with an IC value of 0.14±0.02 µM.
5
0
Compounds 18b and 19d also exhibited remarkable antimicrobial activity with IC values
5
0
of 0.19±0.03 and 0.16±0.06 µM, respectively. Compounds 12f and 19e exhibited IC values
5
0
of 0.21±0.06 and 0.21±0.08 µM, very well comparable to chloramphenicol (IC50 of
.21±0.06 µM). Based on these results, it is evident that among N-substituted indole based
0
chalcones (12a-g), compounds with electron donating groups showed better activity
compared to electron withdrawing groups. Among, N-substituted indole based hydrazide
hydrazones (18a-g, 19a-f, 21a-g), compounds having a 7-alkoxy coumarin substitution on
indole ring were more active compared to compounds with 4-alkoxy coumarin substitution.
Also, increasing the chain length of the alkyl linker (19a-f) did not show any significant
change in the activity. Compounds with para substitution on the phenyl ring showed better
activity than those with meta substitution (18d>18c; 18g>18b; 18f>18e). Among the para
1
0

substituted compounds, the compounds with ethoxy substituent on the phenyl ring showed
better activity than those having methoxy or methyl substituents.
Compounds 12f and 18d showed better activity than chloramphenicol (IC 0.21±0.03
5
0
µMand 0.19±0.06 µM) against E. coli. All the other compounds were less active than
chloramphenicol. All the compounds displayed very weak activity against P. putida.
Compound 12c exhibited highest activity against C. viswanathii with IC of 0.18±0.07 µM.
5
0
Compounds 12b and19c also showed better activity than chloramphenicol with IC values
5
0
of 0.21±0.02 µM and 0.22±0.05 µM respectively. All the other compounds showed weaker
activity than chloramphenicol.
2
.3. In silico analysis
To confirm the possibility of interactions between the new ligands and the macromolecular
target, in silico molecular docking analysis was carried out. A number of possible
macromolecular targets are available for this work. Nitric Oxide synthase (NOS) was
selected as a target as it is the most possible macromolecule with which the synthesized
compounds may interact. Our earlier work has established that semicarbazones do not show
any 1,3-tautomeric shift in the lead compounds, though the corresponding hydrazones are
prone to exhibit Azine-Hydrazone tautomerism.[26] Hence, the molecular docking was
carried out in the semicarbazone tautomeric state of the compounds (18a-21g). Glide
software was used to perform molecular docking of series of compounds (7-alkoxy coumarin
deivatives and 4-alkoxy coumarin derivatives) using the crystal structure of Nitric Oxide
synthase (NOS) of B. Subtilis (PDB ID: 4D7H). Figure 3a shows the interaction diagram
between the most active compound 18d and NOS. Figure 3b shows the superimposition of
co-crystallized ligand and the compound 18d in the corresponding docking pose. Table 5
lists the emodel score values. The most important interactions of 18d in the co-crystallized
ligand binding site of NOS are: Hydrogen bonding interaction of C=O group of 18d with
TYR362, hydrogen bonding interaction of C-O of ethoxy group of 18d with GLY234,  - π
interaction of indole ring of 18d with ARG132, π - π interaction of coumarin ring of 18d
with HIS128; in addition to these interactions there are several hydrophobic interactions that
stabilize the 18d in the active site of NOS.
1
1

Figure 3: a) 3D interaction diagram for 18d in the binding pocket of Nitric Oxide Synthase (NOS),
b) overlapping of Cocrystallized ligand (Magenta) and 18d (Orange), Black dots represent the
interactions and the distances are in Å.
In case of 4-alkoxycomarins, the most active compound 21c was found to have no significant
interactions as shown in Figure 4. Upon comparison, it became clear that 4-alkoxy coumarin
derivatives exhibit minimal stabilizing interactions whereas the 7-alkoxy coumarin
derivatives are associated with many clear interactions. This difference is the origin of
observed differences in the activities of the two sets of compounds.
Figure 4: C) Overlapping of co-crystallized ligand (Magenta) and 21c (yellow) D) 2D-
interactions of 21c with the target site.
Table 5: emodel scores of designed ligands
Compound code
Cocrystallized ligand
emodel score
-92.17
-91.60
-89.04
-89.59
-91.09
-86.97
-86.05
-86.92
-84.96
-91.95
-95.70
-87.16
1
8a
8b
8c
8d
8e
8f
8g
9a
9b
9c
9d
1
1
1
1
1
1
1
1
1
1
1
2

1
1
2
2
9e
9f
1a
1b
1c
-98.49
-75.40
-66.76
-56.80
-69.01
2
2
.4 In vitro evaluation for antileishmanial activity
The antileishmanial activity was performed against promastigotes of L. donovani using
MTT assay. Miltefosine was used as positive control for the study. The results are shown in
Table 6.
Table 6: In vitro antileishmanial activity of indole derivatives against promastigotes of L. donovani
Compound
2a
2b
2c
2d
2e
2f
IC50 (µM)
59±4.2
24.25±3.53
21.5±2.12
69.5±4.9
NI
Compound
19a
IC50 (µM)
NI
1
1
1
1
1
1
19b
19c
19d
19e
NI
NI
NI
NI
NI
19f
NI
1
1
2g
8a
50±0.0
NI
21a
21b
NI
NI
1
1
1
1
1
1
8b
8c
8d
8e
8f
8g
NI
NI
NI
NI
NI
NI
21c
21d
21e
21f
NI
NI
NI
NI
NI
12±0.0
21g
Miltefosine
IC50- Concentration at which 50% inhibition occurs; NI-No inhibition upto 100 µM
Based on the results, it is inferred that among indole based chalcones (12a-g), the
compounds with electron withdrawing groups showed better activity. Compound 12c with
chloro substituent at para position showed good antileishmanial activity with IC50 of
2
2
1.5±2.12 µM, while compound 12b with iodo substituent at para position showed IC of
50
4.25±3.53 µM. Compounds 12a and 12d with electron donating groups i.e. NH and OH
2
substituents at para position exhibited moderate antileishmanial activity with IC of 59±4.2
5
0
µM and 69.5±4.9 µM respectively. Compound 12g with bromo substituent on the indole
ring and amino group at para position on phenyl ring showed IC50 of 50±0.0 µM.
Compounds 12e and 12f with electron donating groups were found to be inactive.
Among, N-substituted indole based hydrazide hydrazones (18a-g, 19a-f, 21a-g), none of the
compounds were found to be active against promastigotes of L. donovani.
3
. Conclusions
1
3

Twenty-seven N-substituted indole derivatives were synthesized and evaluated for in vitro
antimicrobial and antileishmanial activity. Among these, compound 12c with chloro
substituent at para position showed good antileishmanial activity with IC of 21.5±2.12 µM
5
0
against promastigotes of Leishmania donovani. In case of antimicrobial activity, compound
8d exhibited highest activity against Bacillus subtilis with IC value of 0.14±0.02 µM
1
5
0
while compound 12c displayed highest activity against Candida viswanathii with IC value
5
0
of 0.18±0.07 µM. All the compounds showed weak activity against Gram negative bacteria
Escherichia coli and Pseudomonas putida). The docking results revealed that 7-alkoxy
(
coumarin derivatives showed higher binding interactions with nitric oxide synthase as
compared to their 4-alkoxy counterparts and hence, exhibited better activity than the latter.
4
. Experimental
4
.1. General
All chemicals were purchased from Sigma-Aldrich, Merck, SD fine chemicals, Loba
Chemie, Spectrochem and Central Drug House (CDH) etc. and used without further
purification unless otherwise specified. Solvents purchased from commercial sources were
of analytical grade.
Solvents used for the chemical synthesis were dehydrated and distilled according to standard
protocols. Compounds were purified either by crystallization or silica gel column
chromatography (60-120, 230-400 # size, Merck, Germany). TLC developments were
performed on silica gel coated aluminium sheets (TLC Silica Gel 60 F , 0.2 mm thickness,
2
54
Merck, Germany). Developed plates were visualized under UV light and derivatized using
Dragendorff reagent. Melting points of compounds were recorded on Veego melting point
apparatus (Mumbai, India). IR spectra were recorded on FT-IR spectrometer (Perkin Elmer,
1
13
USA). H and C NMR spectra were recorded at 400 MHz and 100 MHz respectively on
Bruker Avance III spectrometer (Bruker, Germany) using TMS as internal standard and the
chemical shifts were reported in δ ppm. 2D NMR data was recorded for assigning proton
and carbon signals for compounds 12f and 18d. The signals in other molecules were
assigned on the basis of chemical shifts. Mass spectra were recorded on Thermo LTQ
(ESI/APCI)-XL mass spectrometer (Thermo, USA) equipped with APCI and ESI probes.
HPLC % purity of compounds were carried out on a reverse-phase C column (Sun Fire,
1
8
4
.6 × 250 mm; 5μ) connected to a Shimadzu HPLC system (Shimadzu Corporation, Kyoto,
Japan) consisting of a model LC-20 AD fitted with a SIL-20 AC HT autosampler and SPD-
M20A photodiode-array detector. An isocratic method was run using solvent A (water) and
1
4

solvent B (methanol) at a flow rate of 1.0 mL/min followed by washing with 100% of solvent
°
B for 10 min. The temperature of the column was set at 40 C. Injection volume was 5 or 10
μL of sample solution (1 mg/mL). LC Solution software (Shimadzu) was used both for data
collection and integration. The chromatograms were recorded in range of 190–600 nm and
observed at the respective λmax for percentage purity of compounds.
4
.2. Synthesis of N-substituted indole chalcones
4
.2.1. Synthesis of N-(3-Dimethylaminopropyl)-1H-indole-3-carbaldehyde (11)
°
To a stirred solution of indole-3-carbaldehyde (10) (1.72 mmol) in acetonitrile at 0 C,
cesium carbonate (8.60 mmol) and potassium iodide (3.44 mmol) were added in small
portions (under nitrogen atmosphere). After 10-15 min, 3-dimethylamino-1-propyl chloride
hydrochloride (3.44 mmol) was added to the resulting mixture. The reaction mixture was
heated to reflux for 28 h. The reaction progress was monitored by TLC. After the completion
of the reaction, the reaction mixture was cooled down to room temperature, dissolved in
water and extracted with ethyl acetate. The ethyl acetate layer was collected and evaporated
to give the desired compound 11 as yellow oil.[23]
N-(3-Dimethylaminopropyl)-1H-indole-3-carbaldehyde (11)
1
Yellow oil, yield 89%, H NMR (CDCl , 400 MHz): δ 9.97 (s, 1H), 8.31-8.29 (m, 1H), 7.75
3
(s, 1H), 7.42-7.39 (m, 1H), 7.34-7.27 (m, 2H), 4.26 (t, 2H, J = 6.8 Hz), 2.21 (t, 2H, J = 6.9
Hz, overlapped with 2 × CH groups), 2.21 (s, 6H, overlapped with CH group), 2.00 (quint,
3
2
2
H, J = 6.8 Hz); ESI-MS found m/z 231 [M+H]+.[23]
4
.2.2 Synthesis of N-(3-Dimethylaminopropyl)-1H-indole chalcone (12a-g)
°
To a solution of substituted acetophenone (1.09 mmol) in methanol at 0 C, 1-2 mL of 10%
aq. NaOH solution was added. After a few minutes, the aldehyde (11) (1.09 mmol) was
°
added to the resulting mixture. The mixture was refluxed at 70-80 C for 4-6 h. The reaction
progress was monitored by TLC. After the completion of the reaction, water was added to
the reaction mixture and it was neutralized to pH 7 using dil. HCl followed by partitioning
with chloroform. The chloroform layer was concentrated to give the crude mixture, which
was purified by column chromatography on silica gel using chloroform:methanol as eluent
to obtain the pure compounds (12a-g).
4
.2.2.1. (E)-1-(4-aminophenyl)-3-(1-(3-(dimethylamino)propyl)-1H-indol-3-yl)prop-2-en-1-one
(12a)
ᵒ
-1
Yellow solid; yield 37%; m.p.179-180 C; IR (KBr): ʋ cm 3339, 3221, 2939, 1633, 1598,
max
1
1
527, 1284, 1170, 743; H NMR (DMSO-d , 400 MHz): δ 8.03-7.90 (m, 2H), 7.89 (d, 2H,
6
1
5

J = 8.4 Hz, Ar-H), 7.86 (s, 1H, indole H-2), 7.61 (d, 1H, J = 15.4 Hz, C=CH-), 7.58 (d, 1H,
J = 7.9 Hz, indole H-7), 7.29-7.21 (m, 2H, indole H-5,6), 6.63 (d, 2H, J =8.6 Hz, Ar-H),
6
.04 (s, 2H, NH ), 4.23 (t, 2H, J = 7.5 Hz, CH ), 2.18 (t, 2H, J = 6.7 Hz, CH ), 2.13 (s, 6H,
2 2 2
1
3
CH ), 1.92 (quint, 2H, J = 6.8 Hz, CH ) ; C NMR (DMSO-d , 100 MHz): δ 186.1 (C=O),
3
2
6
1
53.4 (Ar C-4), 137.3 (C=CH-), 135.8, 134.4, 130.7 (Ar C-2,4), 126.0 (Ar C-1), 125.8, 122.7
C=CH-), 121.2 (indole C-6), 120.5 (indole C-5), 116.0 (indole C-4), 112.9 (Ar C-3,5),
12.1 (indole C-3), 110.8 (indole C-7), 55.9, 45.1, 43.9, 27.5 (CH ); APCI-MS calculated
(
1
2
+
+
for C H N O [M+H] 348, found m/z 348 [M+H] ; anal. HPLC t = 3.4 min, >99.0% at
2
2
25
3
R
2
84 nm.
4
.2.2.2. (E)-3-(1-(3-(dimethylamino)propyl)-1H-indol-3-yl)-1-(4-iodophenyl)prop-2-en-1-one
(12b)
ᵒ
-1
Yellow solid; yield 36%; m.p.174-175 C; IR (KBr): ʋ cm 2947, 2818, 1649, 1583, 1281,
max
1
7
49; H NMR (CDCl , 400 MHz): δ 8.09 (d, 1H, J = 15.0 Hz, C=CH-), 8.00-7.97 (m, 1H,
3
indole H-4), 7.86 (d, 2H, J = 8.4 Hz, Ar-H), 7.76 (d, 2H, J = 8.4 Hz, Ar-H), 7.56 (s, 1H,
indole H-2), 7.48-7.42 (m, 2H), 7.35-7.28 (m, 2H, indole H-5,6), 4.25 (t, 3H, J = 6.8 Hz,
CH ), 2.22 (t, 6H, J = 7.9 Hz, overlapped with 2 × CH groups, CH ), 2.22 (s, 6H, overlapped
2
3
2
1
3
with 1 × CH group, CH ), 2.00 (quint, 2H, J = 6.6 Hz, CH ); C NMR (CDCl , 100 MHz):
2
3
2
3
δ 190.1 (C=O), 139.5 (C=CH-), 138.6, 137.8, 137.7, 134.6, 129.9, 129.7, 126.3, 123.3,
1
2
21.8, 120.9, 116.3, 113.0 (indole C-3), 110.6 (indole C-7) , 99.7 (Ar C-4), 55.9, 45.4, 44.4,
+
+
7.7 (CH ). APCI-MS calculated for C H IN O [M+H] 459, found m/z 459 [M+H] ; anal.
2
22 23
2
HPLC t = 5.8 min, >99.0% at 330 nm.
R
4
.2.2.3. (E)-1-(4-chlorophenyl)-3-(1-(3-(dimethylamino)propyl)-1H-indol-3-yl)prop-2-en-1-one
(12c)
ᵒ
-1
Yellow solid; yield 33%; m.p.192-193 C; IR (KBr): ʋ cm 3057, 2940, 2770, 1650, 1587,
max
1
1
3
5
282, 1099, 743; H NMR (CDCl , 400 MHz): δ 8.09 (d, 1H, J = 15.5 Hz, C=CH-), 7.99 (d,
3
H, J = 8.5 Hz), 7.56 (s, 1H, indole H-2),7.51-7.43 (m, 4H), 7.35-7.29 (m, 2H, indole H-
,6), 4.25 (t, 2H, J = 6.8 Hz, CH ), 2.23 (t, 2H, J = 6.7 Hz, CH ), 2.23 (s, 6H, overlapped
2
2
1
3
with 1 × CH group, CH ), 2.00 (quint, 2H, J = 6.7 Hz, CH ); C NMR (CDCl , 100 MHz):
2
3
2
3
δ 189.4 (C=O), 139.4, 138.5, 137.7 (C=CH-), 137.6, 134.6 (indole C-2), 129.8, 128.9, 126.3,
23.3, 121.7, 120.9, 116.3, 113.0 (indole C-3), 110.6 (indole C-7), 55.9, 45.4, 44.4, 27.7
1
+
+
(
CH ); APCI-MS calculated for C H ClN O [M+H] 367, found m/z 367 [M+H] , 369
2 22 23 2
+
[
M+H+2] ; anal. HPLC t = 5.3 min, >99.0% at 320 nm.
R
1
6

4
.2.2.4. (E)-3-(1-(3-(dimethylamino)propyl)-1H-indol-3-yl)-1-(4-hydroxyphenyl)prop-2-en-1-one
(12d)
ᵒ
-1
Yellow solid; yield 29%; m.p.166-167 C; IR (KBr): ʋ cm 3056, 2962, 1646, 1587, 1260,
max
1
1
1
020, 800, 742; H NMR (CD OD, 400 MHz): δ 8.01 (d, 2H, J = 15.5 Hz, C=CH-), 7.98 (s,
3
H), 7.96 (dd, 1H, J = 2.7 and 7.4 Hz), 7.77 (s, 1H), 7.59 (d, 1H, J = 15.5 Hz, C=CH-), 7.48
(dd, 1H, J = 1.6 and 8.5 Hz), 7.30-7.23 (m, 2H), 6.90 (d, 2H, J = 8.7 Hz, Ar-H), 4.23 (t, 2H,
J = 6.9 Hz, CH ), 2.56 (dd, 2H, J = 7.5 and 10.1 Hz, CH ), 2.40 (s, 6H, CH ), 2.08 (quint,
2
2
3
1
3
2
H, J = 6.8 Hz, CH ); C NMR (CD OD, 100 MHz): δ 191.3 (C=O), 163.6 (Ar C-4), 139.6
2 3
(
C=CH-), 139.0, 135.5, 132.0 (Ar C-2,6), 131.5, 127.7, 124.3, 122.8, 121.6, 117.3, 116.5
Ar C-3,5), 114.4, 111.6, 57.0 (CH ), 45.1 (CH ), 44.7 (CH ), 27.9 (CH ); APCI-MS
(
2
2
3
2
+
+
calculated for C H N O [M+H] 349, found m/z 349 [M+H] ; anal. HPLC t = 3.2 min,
2
2
24
2
2
R
>
99.0% at 284 nm.
4
.2.2.5. (E)-1-(2,4-dimethoxyphenyl)-3-(1-(3-(dimethylamino)propyl)-1H-indol-3-yl)prop-2-en-1-
one (12e)
ᵒ
-1
Yellow solid; yield 32%; m.p.183-184 C; IR (KBr): ʋ cm 3493, 3430, 2955, 1643, 1594,
max
1
1
564, 1290, 1260, 748; H NMR (CDCl , 400 MHz): δ 7.98 (dd, 1H, J = 1.1 and 6.8 Hz,
3
indole H-4), 7.94 (d, 1H, J = 15.7 Hz, C=CH-), 7.77 (d, 1H, J= 8.3 Hz, Ar-H), 7.58 (d, 1H,
J = 15.7 Hz, C=CH-), 7.48 (s, 1H), 7.40 (d, 1H, J = 8.0 Hz, indole H-7), 7.31-7.23 (m, 2H,
indole H-5,6), 6.56 (dd, 1H, J = 2.2 and 8.5 Hz, Ar-H), 6.52 (d, 1H, J = 2.2 Hz, Ar-H), 4.23
(
t, 2H, J = 6.7 Hz, CH ), 3.92 (s, 3H, OCH ), 3.86 (s, 3H, OCH ), 2.31 (t, 2H, J = 7.3 Hz,
2 3 3
1
3
CH ), 2.27 (s, 6H, CH ), 2.03 (quint, 2H, J = 6.5 Hz, CH ); C NMR (CDCl , 100 MHz): δ
2
3
2
3
1
1
90.8 (C=O), 163.7 (Ar C-4), 160.1 (Ar C-2), 137.5 (C=CH-), 136.5, 133.5, 132.6, 126.3,
22.93, 122.90, 122.6, 121.3 120.9, 113.3 (indole C-3), 110.3, 105.1, 98.8 (Ar C-3), 55.9
(
OCH ), 55.8 (OCH ), 55.6 (CH ), 45.1 (CH ), 44.1 (CH ), 27.4 (CH ). APCI-MS calculated
3 3 2 2 3 2
+
+
for C H N O [M+H] 393, found m/z 393 [M+H] ; anal. HPLC t = 5.9 min, >99.0% at
2
4
28
2
3
R
3
29 nm.
4
.2.2.6. (E)-1-(3,4-dimethoxyphenyl)-3-(1-(3-(dimethylamino)propyl)-1H-indol-3-yl)prop-2-en-1-
one (12f)
ᵒ
-1
Yellow solid; yield 35%; m.p.198-199 C; IR (KBr): ʋ cm 3424,1642, 1594, 1417, 1260,
max
1
7
49; H NMR (CDCl , 400 MHz): δ 8.06 (d, 1H, J = 15.7 Hz, C=CH-), 8.00 (d, 1H, J = 7.9
3
Hz, indole H-4), 7.73 (d, 1H, J = 8.4 Hz, Ar-H), 7.65 (d, 2H, J = 6.4 Hz, Ar-H, indole H-2),
.60 (d, 1H, J = 15.7 Hz, C=CH-), 7.42 (d, 1H, J = 9.4 Hz, indole H-7), 7.35-7.29 (m, 2H,
indole H-5,6), 6.95 (d, 1H, J = 7.9 Hz, Ar-H), 4.37 (t, 2H, J = 5.4 Hz, CH ), 3.98 (s, 3H,
7
2
1
7

OCH ), 3.97 (s, 3H, OCH ), 2.81 (t, 2H, J = 7.1 Hz, CH ), 2.63 (s, 6H, CH ), 2.36 (quint,
3
3
2
3
1
3
2
1
H, J = 7.3 Hz, CH ); C NMR (CDCl , 100 MHz): δ 188.9 (C=O),152.9 (Ar C-4 (OCH )),
2 3 3
49.3 (Ar C-3 (OCH )), 137.4 (C=CH-), 132.7 (indole C-2), 132.1 (Ar C-1), 126.6 (indole
3
C-7), 123.5, 122.7 (indole C-6, Ar C-6), 121.8 (indole C-5), 120.9 (indole C-4), 117.5
(
C=CH-), 113.8 (indole C-3), 111.0 (Ar C-2), 110.2 (Ar C-5), 56.1 (OCH ), 55.4 (CH ),
3 2
+
4
3.9 (CH ), 43.5 (CH ), 25.7 (CH ). APCI-MS calculated for C H N O [M+H] 393,
2 3 2 24 28 2 3
+
found m/z 393 [M+H] ; anal. HPLC t = 6.1 min, >99.0% at 330 nm.
R
4
1
.2.2.7. (E)-1-(4-aminophenyl)-3-(5-bromo-1-(3-(dimethylamino)propyl)-1H-indol-3-yl)prop-2-en-
-one (12g)
ᵒ
-1
Yellow solid; yield 40%; m.p. 220-225 C; IR (KBr): ʋ cm 3341, 3217, 2928, 1598,
max
1
1
526, 1283, 798; H NMR (DMSO-d , 400 MHz): δ 8.17-8.16 (m, 2H), 7.90 (d, 2H, J = 8.6
6
Hz, Ar-H), 7.85 (d, 1H, J = 15.5 Hz, C=CH-), 7.60 (d, 1H, J = 7.5 Hz), 7.57 (s, 1H), 7.39
dd, 1H, J = 1.7 and 8.7 Hz), 6.64-6.62 (m, 2H), 6.03 (s, 2H, NH ), 4.24 (t, 2H, J = 6.9 Hz,
(
2
CH ), 2.17 (t, 2H, J = 6.8 Hz, CH ), 2.13 (s, 6H, CH ), 1.92 (quint, 2H, J = 6.9 Hz, CH );
2
2
3
2
1
3
C NMR (DMSO-d , 100 MHz): δ 186.0 (C=O), 153.3 (Ar C-4), 135.8 (C=CH-), 134.5,
6
1
4
30.6, 127.5, 125.9, 124.9, 122.2, 116.9, 113.7, 112.8, 112.7, 111.6, 55.7 (CH ), 45.0 (CH ),
2
3
+
3.9 (CH ), 27.4 (CH ); APCI-MS calculated for C H BrN O [M+H] 426, found m/z 426
2
2
22 24
3
+
+
[
M+H] , 428 [M+H+2] ; anal. HPLC t = 3.8 min, >99.0% at 308 nm.
R
4
4
.3. Synthesis of N-substituted indole hydrazide-hydrazones
.3.1 Synthesis of 7-Bromoalkoxy-2H-chromen-2-ones (14) and 4-Bromoalkoxy-2H-
chromen-2-ones (16)
Compound 13 or 15 (3.08 mmol, 1 equiv.) was dissolved in acetonitrile (2 mL) followed by
addition of anhydrous K CO (6 equiv.). Then an appropriate alkyl halide (9.25 mmol, 3
2
3
equiv.) was added dropwise to the stirred reaction mixture. The stirring was continued for
°
4
-5 h at 60 C. The reaction mixture was extracted with CH Cl (80 mL), the organic extracts
2
2
were washed with water (100 mL), dried over anhydrous Na SO , filtered and the solvent
2
4
was removed in vacuo. The crude mixture was purified by column chromatography on silica
gel using hexane:ethyl acetate as eluent to obtain the pure compounds (14 or 16).[24]
4
.3.1.1. 7-(2-bromoethoxy)-2H-chromen-2-one (14a)
ᵒ
ᵒ
1
White solid; yield 69%; m.p. 137-138 C [lit. 134-135 C]; H NMR (CDCl , 400 MHz): δ
3
7
.63 (d, 1H, J = 9.5 Hz), 7.38 (d, 1H, J = 8.6 Hz), 6.86 (dd, 1H, J = 1.8 and 8.6 Hz), 6.80
(bs, 1H), 6.26 (dd, 1H, J = 2.1 and 9.5 Hz), 4.34 (t, 2H, J = 6.7 Hz), 3.66 (t, 2H, J = 6.0 Hz);
1
8

1
3
C NMR (CDCl , 100 MHz): δ 161.2, 161.1, 155.8, 143.4, 129.0, 113.6, 113.1, 112.9,
3
1
01.7, 68.2, 28.5.
4
.3.1.2. 7-(3-bromopropoxy)-2H-chromen-2-one (14b)
ᵒ
1
White solid; yield 64%; m.p. 153-154 C; H NMR (CDCl , 400 MHz): δ 7.64 (d, 1H, J =
3
9
.5 Hz), 7.38 (d, 1H, J = 8.4 Hz), 6.86-6.82 (m, 2H), 6.26 (d, 1H, J = 9.4 Hz), 4.17 (t, 2H, J
1
3
=
5.8 Hz), 3.61 (t, 2H, J = 6.4 Hz), 2.36 (quint, 2H, J = 6.0 Hz); C NMR (CDCl , 100
3
MHz): δ 161.9, 161.2, 155.9, 143.4, 128.9, 113.3, 112.8, 112.7, 101.6, 65.9, 32.0, 29.6.
4
.3.1.3. 4-(2-bromoethoxy)-2H-chromen-2-one (16)
ᵒ
ᵒ
1
White solid; yield 58%; m.p. 144-145 C [lit. 142-146 C ]; H NMR (CDCl , 400 MHz): δ
3
7
2
.87 (dd, 1H, J = 1.5 and 7.9 Hz), 7.57 (ddd, 1H, J = 1.6, 7.4 and 9.8 Hz), 7.33-7.27 (m,
1
3
H), 5.66 (s, 1H), 4.45 (t, 2H, J = 5.7 Hz), 3.76 (t, 2H, J = 5.9 Hz); C NMR (CDCl , 100
3
MHz): δ 164.9, 162.6, 153.4, 132.8, 124.1, 123.2, 116.9, 115.4, 90.9, 68.5, 27.7.
4
.3.2 Synthesis of N-substituted indole-3- carbaldehyde (17a, 17b, 20)
ᵒ
To a solution of indole-3-carbaldehyde (1.72 mmol, 1 eq.) in dry DMF at 0 C, cesium
carbonate (1.5 eq.) was added. The mixture was stirred for 15-20 min followed by the
addition of 4-bromoalkoxy-2H-chromen-2-ones (16) or 7-bromoalkoxy-2H-chromen-2-
ones (14) (2.07 mmol, 1.2 eq.). The resultant mixture was stirred at room temperature for
1
2-18 h. The progress of reaction was monitored by TLC. After the completion of reaction,
the reaction mixture was quenched with water followed by partitioning with ethyl acetate.
The combined ethyl acetate layers were washed with brine solution and concentrated to get
crude product. The crude mixture was purified through column chromatography on silica
gel using hexane:ethyl acetate as eluent.
4
.3.2.1.1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indole-3-carbaldehyde (17a)
ᵒ
1
Beige solid; yield 57%; m.p. 177-178 C; H NMR (DMSO-d , 400 MHz): δ 9.93 (s, 1H),
6
8
7
2
4
1
1
.37 (s, 1H), 8.10 (d, 1H, J = 7.8 Hz), 7.95 (d, 1H, J = 9.5 Hz), 7.72 (d, 1H, J = 8.2 Hz),
.58 (d, 1H, J = 8.6 Hz), 7.33 (t, 1H, J = 7.3 Hz), 7.26 (t, 1H, J = 7.5 Hz), 6.98 (d, 1H, J =
.2 Hz), 6.87 (dd, 1H, J = 2.3 and 8.6 Hz), 6.27 (d, 1H, J = 9.5 Hz), 4.73 (t, 2H, J = 5.0 Hz),
1
3
.49 (t, 2H, J = 5.0 Hz); C NMR (DMSO-d , 100 MHz): δ 184.7, 160.9, 160.1, 155.2,
6
44.2, 141.2, 137.2, 129.5, 124.6, 123.5, 122.5, 120.9, 117.4, 112.71, 112.67, 112.64, 111.2,
01.3, 67.0, 45.6.
4
.3.2.2.1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-indole-3-carbaldehyde (17b)
1
9

ᵒ
1
Beige solid; yield 51%; m.p. 201-202 C; H NMR (DMSO-d , 400 MHz): δ 9.89 (s, 1H),
6
8
.35 (s, 1H), 8.12 (dd, 1H, J = 1.6 and 6.9 Hz), 7.98 (d, 1H, J = 9.5 Hz), 7.65 (d, 1H, J = 7.7
Hz), 7.61 (d, 1H, J = 8.6 Hz), 7.31-7.23 (m, 2H), 6.97 (d, 1H, J = 2.3 Hz), 6.91 (dd, 1H, J =
2
2
1
1
.4 and 8.6 Hz), 6.28 (d, 1H, J = 9.5 Hz), 4.48 (t, 2H, J = 6.8 Hz), 4.08 (t, 2H, J = 5.9 Hz),
1
3
.31 (quint, 2H, J = 6.3 Hz); C NMR (DMSO-d , 100 MHz): δ 184.5, 161.4, 160.2, 155.3,
6
44.3, 140.8, 137.0, 129.4, 124.6, 123.5, 122.4, 121.0, 117.2, 112.6, 112.5, 112.4, 110.9,
01.2, 65.4, 43.2, 28.8.
4
.3.2.3.1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indole-3-carbaldehyde (20)
ᵒ
1
Beige solid; yield 49%; m.p. 193-194 C; H NMR (DMSO-d , 400 MHz): δ 9.94 (s, 1H),
6
8
.52 (s, 1H), 8.10 (d, 1H, J = 7.8 Hz), 7.79 (d, 1H, J = 8.2 Hz), 7.64 (d,1H, J = 7.9 Hz), 7.61
(t, 1H, J = 7.7 Hz), 7.38-7.33 (m, 2H), 7.30-7.25 (m, 2H), 5.91 (s, 1H), 4.85 (t, 2H, J = 4.6
1
3
Hz), 4.60 (t, 2H, J = 4.8 Hz); C NMR (DMSO-d , 100 MHz): δ 184.7, 164.4, 161.4, 152.7,
6
1
9
41.4, 137.2, 132.8, 124.6, 124.1, 123.6, 122.8, 122.6, 121.0, 117.6, 116.4, 114.9, 111.3,
1.1, 68.1, 45.1.
4
.3.3 Synthesis of N-substituted indole-3 hydrazides (18a-g, 19a-f, 21a-g)
To a solution of substituted indole-3-carbaldehyde (0.29 mmol, 1 eq.) in DMSO, substituted
benzhydrazide (0.32 mmol, 1.1 eq.) was added and the resultant mixture was refluxed at 110
ᵒC for 3-6 h. The progress of the reaction was monitored by TLC. After the completion of
reaction, the reaction mixture was allowed to cool to room temperature. The mixture was
poured in ice cold water. The precipitates thus obtained were filtered, washed with methanol
and dried to obtain the desired compound.
4
.3.3.1.(E)-N'-((1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indol-3-
yl)methylene)benzohydrazide (18a)
ᵒ
-1
Beige solid; yield 59%; m.p. 201-202 C; IR (KBr): ʋ cm 3234, 3165, 2918, 2847, 1724,
max
1
1
640, 1612, 1383, 1278, 1124, 835, 747; H NMR (DMSO-d , 400 MHz): δ 11.57 (s, 1H,
6
NH), 8.61 (s, 1H, CH=N), 8.31 (d, 1H, J = 8.0 Hz, indole H-4), 7.96 (d, 1H, J = 9.8 Hz,
coumarin H-4), 7.92 (dd, 3H, J = 2.1 and 10.0 Hz), 7.65 (d, 1H, J = 9.3 Hz, indole H-7),
7
7
6
5
.59-7.56 (m, 2H), 7.54-7.50 (m, 2H), 7.29 (t, 1H, J = 6.4 Hz, indole H-6), 7.21 (t, 1H, J =
.5 Hz, indole H-5), 7.00 (d, 1H, J = 2.3 Hz), 6.88 (dd, 1H, J = 2.6 and 9.0 Hz, coumarin H-
), 6.28 (d, 1H, J = 9.8 Hz, coumarin H-3), 4.66 (t, 2H, J = 5.2 Hz, CH ), 4.47 (t, 2H, J =
2
1
3
.2 Hz, CH ); C NMR (DMSO-d , 100 MHz): δ 162.5 (CONH), 161.1, 160.2 (coumarin
2
6
C=O), 155.3, 144.34 (coumarin C-4), 144.28 (C=N), 137.1, 134.0, 133.4 (indole C-2), 131.4,
2
0

1
1
29.6, 128.4, 127.5, 124.9, 122.8 (indole C-6),122.2 (indole C-4), 120.8 (indole C-5),112.7,
12.6 (indole C-3), 111.3, 110.6 (indole C-7), 101.3 (coumarin C-8), 67.3 (CH ), 45.1 (CH );
2
2
+
+
ESI-MS calculated for C H N O [M+H] 452, found m/z 452 [M+H] ; anal. HPLC t =
2
7
21
3
4
R
3
.8 min, >99.0% at 325 nm.
4
.3.3.2. (E)-3-methoxy-N'-((1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (18b)
ᵒ
-1
White solid; yield 46%; m.p. 247-248 C; IR (KBr): ʋ cm 2917, 2849, 1716, 1610, 1463,
max
1
1
266, 752; H NMR (DMSO-d , 400 MHz): δ 11.52 (s, 1H, NH), 8.61 (s,1H, CH=N), 8.30
6
(
d, 1H, J = 7.8 Hz, indole H-4), 7.96 (d, 1H, J = 9.6 Hz, coumarin H-4), 7.93 (s, 1H), 7.64
d, 1H, J = 8.2 Hz, indole H-7), 7.58 (d, 1H, J = 8.7 Hz, coumarin H-5), 7.49 (d, 1H, J = 7.5
(
Hz), 7.44 (d, 2H, J = 7.9 Hz), 7.28 (t, 1H, J = 7.4 Hz, indole H-6), 7.20 (t, 1H, J = 7.8 Hz,
indole H-5), 7.14 (dd, 1H, J = 2 and 7.1 Hz), 6.99 (d, 1H, J = 2.2 Hz, coumarin H-8), 6.88
(dd, 1H. J = 2.3 and 8.6 Hz, coumarin H-6), 6.28 (d, 1H, J = 9.5 Hz, coumarin H-3), 4.66 (t,
1
3
2
H, J = 4.8 Hz, CH ), 4.47 (t, 2H, J = 4.8 Hz, CH ), 3.83 (s, 3H, OCH ); C NMR (DMSO-
2 2 3
d6, 100 MHz): δ 162.3 (CONH), 161.1 (Ar C-3), 160.2 (coumarin C=O), 159.2 (coumarin
C-7), 155.3, 144.5 (coumarin C-4), 144.3 (C=N), 137.1, 135.4, 133.5 (indole C-2), 129.6
(coumarin C-5), 129.5, 124.8, 122.8, 122.2, 120.8, 119.7, 117.0, 112.8, 112.7, 112.6 (indole
C-3), 111.3, 110.6 (indole C-7),101.3 (coumarin C-8), 67.3 (CH ), 55.3 (OCH ), 45.1 (CH );
2
3
2
+
+
ESI-MS calculated for C H N O [M+H] 482, found m/z 482 [M+H] ; anal. HPLC t =
2
8
23
3
5
R
3
.8 min, >99.0% at 325 nm.
4
.3.3.3. (E)-3-ethoxy-N'-((1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indol-3-yl)
methylene) benzohydrazide (18c)
ᵒ
-1
White solid; yield 63%; m.p. 221-222 C; IR (KBr): ʋ cm 3230, 3053, 2984, 1729, 1611,
max
1
1
8
580, 1384, 1281, 1182, 1048, 747; H NMR (DMSO-d , 400 MHz): δ 11.50 (s, 1H, NH),
6
.61 (s, 1H, CH=N), 8.31 (d, 1H, J = 7.8 Hz, indole H-4), 7.95 (d, 1H, J = 9.5 Hz, coumarin
H-4), 7.93 (s, 1H, indole H-2), 7.64 (d, 1H, J = 8.2 Hz, indole H-7), 7.58 (d, 1H, J = 8.6 Hz,
coumarin H-5), 7.48 (d, 1H, J = 7.6 Hz), 7.44 (d, 1H, J = 1.8 Hz), 7.41 (d, 1H, J = 7.8 Hz),
7
1
.28 (t, 1H, J = 7.2 Hz, indole H-6), 7.20 (t, 1H, J = 7.5 Hz, indole H-5), 7.12 (dd, 1H, J =
.8 and 8.1 Hz), 6.99 (d, 1H, J = 2.1 Hz, coumarin H-8), 6.87 (dd, 1H, J = 2.3 and 8.6 Hz,
coumarin H-6), 6.27 (d, 1H, J = 9.5 Hz, coumarin H-3), 4.66 (t, 2H, J = 4.7 Hz, CH ), 4.47
2
1
3
(
t, 2H, J = 4.8 Hz, CH ), 4.09 (q, 2H, J = 6.9 Hz, OCH ), 1.36 (t, 3H, J = 6.9 Hz, CH ); C
2 2 3
NMR (DMSO-d , 100 MHz): δ 162.2 (CONH), 161.1 (Ar C-3), 160.2 (coumarin C=O),
6
1
58.4 (coumarin C-7), 155.3, 144.4 (coumarin C-4), 144.3 (C=N), 137.1, 135.3, 133.4
2
1

(indole C-2), 129.6 (coumarin C-5), 129.5, 124.9, 122.8, 122.2, 120.8, 119.6, 117.3, 113.3,
1
12.7, 112.6 (indole C-3), 111.3, 110.6 (indole C-7), 101.3 (coumarin C-8), 67.3 (CH ), 63.3
2
+
(
OCH ), 45.1 (CH ), 14.6 (CH ); ESI-MS calculated for C H N O [M+H] 496, found
2
2
3
29 25
3
5
+
m/z 496 [M+H] ; anal. HPLC t = 4.3 min, >99.0% at 300 nm.
R
4
.3.3.4. (E)-4-ethoxy-N'-((1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indol-3-yl)
methylene) benzohydrazide (18d)
ᵒ
-1
White solid; yield 64%; m.p. 252-253 C; IR (KBr): ʋ cm 3169, 2919, 1724, 1608, 1262,
max
1
1
8
119, 833, 752; H NMR (DMSO-d , 400 MHz): δ 11.41 (s, 1H, NH), 8.59 (s, 1H, CH=N),
6
.31 (d, 1H, J = 7.7 Hz, indole H-4), 7.96 (d, 1H, J = 9.5 Hz, coumarin H-4), 7.90 (d, 3H, J
=
8.9 Hz, Ar H-2,6; indole H-2), 7.64 (d, 1H, J = 8.1 Hz, indole H-7), 7.58 (d, 1H, J = 8.6
Hz, coumarin H-5), 7.28 (t, 1H, J = 7.1 Hz, indole H-6), 7.19 (t, 1H, J = 7.4 Hz, indole H-
5
8
), 7.03 (d, 2H, J = 8.6 Hz, Ar H-3,5), 6.99 (s, 1H, coumarin H-8), 6.88 (dd, 1H, J = 1.8 and
.5 Hz, coumarin H-6), 6.27 (d, 1H, J =9.5 Hz, coumarin H-3), 4.65 (t, 2H, J = 5.4 Hz,
CH ), 4.47 (t, 2H, J = 4.5 Hz, CH ), 4.10 (q, 2H, J = 6.7 Hz, OCH ), 1.35 (t, 3H, J = 6.8 Hz,
2
2
2
1
3
CH ); C NMR (DMSO-d , 100 MHz): δ 161.9 (CONH), 161.1 (Ar C-4), 160.1 (coumarin
3
6
C=O), 155.3, 144.2 (coumarin C=N), 143.7, 137.1, 133.1 (indole C-2), 129.5 (coumarin C-
), 129.3 (Ar C-2,6), 125.9 (Ar C-1), 124.9, 122.7 (indole C-6), 122.2 (indole C-4), 120.7
5
(
indole C-5), 114.0 (Ar C-3,5), 112.7, 112.6 (indole C-3), 111.4, 110.5 (indole C-7), 101.3
coumarin C-8), 67.3 (CH ), 63.3 (OCH ), 45.1 (CH ),14.5 (CH ); ESI-MS calculated for
(
2
2
2
3
+
+
C H N O [M+H] 496, found m/z 496 [M+H] ; anal. HPLC t = 4.2 min, >99.0% at 325
2
9
25
3
5
R
nm.
4
.3.3.5. (E)-3-methyl-N'-((1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indol-3-yl)
methylene) benzohydrazide (18e)
ᵒ
-1
White solid; yield 62%; m.p. 234-235 C; IR (KBr): ʋ cm 3494, 3179, 3008, 2865, 1750,
max
1
1
638, 1613, 1582, 1278, 1118, 830, 744; H NMR (DMSO-d , 400 MHz): δ 11.51 (s, 1H,
6
NH), 8.60 (s, 1H, CH=N), 8.31 (d, 1H, J = 7.8 Hz, indole H-4), 7.96 (d, 1H, J = 9.5 Hz,
coumarin H-4), 7.92 (s, 1H), 7.73 (s, 1H), 7.70 (d, 1H, J = 6.5 Hz), 7.64 (d, 1H, J = 8.2 Hz,
indole H-7), 7.58 (d, 1H, J = 8.6 Hz, coumarin H-5), 7.39 (m, 2H), 7.28 (t, 1H, J = 7.4 Hz,
indole H-6), 7.20 (t, 1H, J = 8.5 Hz, indole H-5), 6.99 (d, 1H, J = 2.1 Hz, coumarin H-8),
6
4
.87 (dd, 1H, J = 2.5 and 8.6 Hz, coumarin H-6), 6.27 (d, 1H, J = 9.5 Hz, coumarin H-3),
1
3
.66 (t, 2H, J = 4.7 Hz, CH ), 4.47 (t, 2H, J = 4.8 Hz, CH ), 2.39 (s, 3H, CH ); CNMR
2
2
3
(
DMSO-d , 100 MHz): δ 162.6 (CONH), 161.1 (Ar C-3), 160.3 (coumarin C=O), 160.2
6
(coumarin C-7), 155.3, 144.28 (coumarin C-4), 144.22 (C=N), 137.7, 137.1, 134.0, 133.4
2
2

(indole C-2), 131.9, 129.6 (coumarin C-5), 128.3, 128.0, 124.9, 124.7, 122.8 (indole C-6),
1
22.2 (indole C-4), 120.8 (indole C-5), 112.7, 111.3, 110.6 (indole C-7), 101.3 (coumarin
+
C-8), 67.4 (CH ), 45.1 (CH ), 21.0 (CH ); ESI-MS calculated for C H N O [M+H] 466,
2
2
3
28 23
3
4
+
found m/z 466 [M+H] ; anal. HPLC t = 4.2 min, >99.0% at 326 nm.
R
4
.3.3.6. (E)-4-methyl-N'-((1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (18f)
ᵒ
-1
White solid; yield 54%; m.p. 254-255 C; IR (KBr): ʋ cm 3201, 3008, 1709, 1635, 1549,
max
1
1
8
7
7
1
276, 1124, 749; H NMR (DMSO-d , 400 MHz): δ 11.47 (s, 1H, NH), 8.61 (s, 1H, CH=N),
6
.31 (d, 1H, J = 7.3 Hz, indole H-4), 7.95(d, 1H, J = 9.5 Hz, coumarin H-4), 7.91 (s, 1H),
.83 (d, 2H, J = 7.9 Hz), 7.64 (d, 1H, J = 8.4 Hz), 7.58 (d, 2H, J = 8.6 Hz), 7.32 (d, 2H, J =
.9 Hz), 7.27 (d, 1H, J = 7.3 Hz, indole H-6), 7.20 (t, 1H, J = 6.3 Hz, indole H-5), 6.99 (s,
H, coumarin H-8), 6.88 (dd, 1H, J = 1.4 and 8.2 Hz, coumarin H-6), 6.27 (d, 1H, J = 9.5
Hz, coumarin H-3), 4.65 (t, 2H, J = 4.4 Hz, CH ), 4.47 (t, 2H, J = 4.7 Hz, CH ), 2.38 (s, 3H,
2
2
1
3
CH ); C NMR (DMSO-d , 100 MHz): δ 162.4 (CONH), 161.1 (Ar C-4), 160.2 (coumarin
3
6
C=O), 155.3, 144.3 (coumarin C-4), 144.1 (C=N), 141.3, 137.1, 133.2 (indole C-2), 131.1,
29.5 (coumarin C-5), 128.9, 127.5, 124.9, 122.8 (indole C-6), 122.2 (indole C-4), 120.7
1
(indole C-5), 112.7, 112.6 (indole C-3), 111.4, 110.5 (indole C-7), 101.3 (coumarin C-8),
+
6
7.4 (CH ), 45.1 (CH ), 21.0 (CH ); APCI-MS calculated for C H N O [M+H] 466,
2
2
3
28 23
3
4
+
found m/z 466 [M+H] ; anal. HPLC t = 4.1 min, >99.0% at 325 nm.
R
4
.3.3.7. (E)-4-methoxy-N'-((1-(2-((2-oxo-2H-chromen-7-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (18g)
ᵒ
-1
White solid; yield 51%; m.p. 247-248 C; IR (KBr): ʋ cm 3206, 2930, 2851, 1716, 1641,
max
1
1
1
7
7
8
612, 1548, 1260, 1124, 751; H NMR (DMSO-d , 400 MHz): δ 11.42 (s, 1H, NH), 8.60 (s,
6
H, CH=N), 8.31 (d, 1H, J = 7.7 Hz, indole H-4), 7.95 (d, 1H, J = 9.6 Hz, coumarin H-4),
.91 (d, 3H, J = 8.2 Hz), 7.63 (d, 1H, J = 8.1 Hz), 7.58 (d, 1H, J = 8.6 Hz, coumarin H-5),
.27 (t, 1H, J = 8.8 Hz, indole H-6), 7.19 (t, 1H, J = 9.0 Hz, indole H-5), 7.05 (d, 2H, J =
.6 Hz), 6.98 (s, 1H, coumarin H-8), 6.87 (d, 1H, J = 8.5 Hz, coumarin H-6), 6.27 (d, 1H, J
=
9.4 Hz, coumarin H-3), 4.65 (t, 2H, J = 4.6 Hz, CH ), 4.46 (t, 2H, J = 4.3 Hz, CH ), 3.83
2 2
1
3
(
s, 3H, OCH ); C NMR (DMSO-d , 100 MHz): δ 161.9 (CONH), 161.7 (Ar C-4), 161.1
3 6
(coumarin C=O), 160.2 (coumarin C-7), 155.3, 144.2 (coumarin C-4), 143.8 (C=N), 137.1,
1
5
33.1, 129.5, 129.3, 126.0, 124.9, 122.8 (indole C-6), 122.2 (indole C-4), 120.7 (indole C-
), 113.6, 112.7, 112.6 (indole C-3), 111.4, 110.5 (indole C-7), 101.3 (indole C-8), 67.3
2
3

+
(
CH ), 55.4 (OCH ), 45.1 (CH ); APCI-MS calculated for C H N O [M+H] 482, found
2 3 2 28 23 3 5
+
m/z 482 [M+H] ; anal. HPLC t = 4.2 min, >99.0% at 327 nm.
R
4
.3.3.8. (E)-N'-((1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-indol-3-yl)methylene)
benzohydrazide (19a)
ᵒ
-1
White solid; yield 49%; m.p. 220-221 C; IR (KBr): ʋ cm 3441, 2925, 1725, 1611, 1384,
max
1
1
276, 1126, 834, 750; H NMR (DMSO-d , 400 MHz): δ 11.53 (s, 1H, NH), 8.58 (s, 1H,
6
CH=N), 8.32 (d, 1H, J = 7.6 Hz, indole H-4), 7.97 (d, 1H, J = 9.5 Hz, coumarin H-4), 7.91
d, 2H, J = 7.5 Hz), 7.88 (s, 1H, indole H-2), 7.61 (d, 1H, J = 8.6 Hz), 7.56 (d, 2H, J = 7.6
(
Hz), 7.51 (t, 2H, J = 7.08 Hz), 7.23 (t, 1H, J = 7.1Hz, indole H-6), 7.18 (t, 1H, J = 7.1 Hz,
indole H-5), 6.97 (s, 1H, coumarin H-8), 6.92 (d, J = 8.7 Hz, coumarin H-6), 6.28 (d, 1H, J
=
9.4 Hz, coumarin H-3), 4.41 (t, 2H, J = 6.5 Hz, CH ), 4.05 (t, 2H, J = 5.6 Hz, CH ), 2.28
2 2
1
3
(
(
(
(
(
4
quint, 2H, J = 7.0 Hz, CH ); C NMR (DMSO-d , 100 MHz): δ 162.5 (CONH), 161.5
2 6
coumarin C=O), 160.3, 155.3, 144.34 (coumarin C-4), 144.29 (C=N), 136.9, 134.0, 133.0
indole C-2), 131.3, 129.5, 128.4, 127.5, 124.8, 122.8 (indole C-6), 122.3 (indole C-4), 120.7
indole C-5), 112.6, 112.5, 112.4, 111.2, 110.2 (indole C-7), 101.3 (coumarin C-8), 65.5
+
CH ), 42.6 (CH ), 29.0 (CH ); ESI-MS calculated for C H N O [M+H] 466, found m/z
2
2
2
28 23
3
4
+
66 [M+H] ; anal. HPLC t = 4.2 min, >99.0% at 290 nm.
R
4
.3.3.9. (E)-3-methoxy-N'-((1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-indol-3-
yl)methylene) benzohydrazide (19b)
ᵒ
-1
White solid; yield 52%; m.p. 234-235 C; IR (KBr): ʋ cm 3224, 3056, 2919, 2847, 1728,
max
1
1
1
612, 1553, 1386, 1283, 1127, 1047, 835, 746; H NMR (DMSO-d , 400 MHz): δ 11.49 (s,
6
H, NH), 8.58 (s, 1H, CH=N), 8.32 (d, 1H, J = 7.6 Hz, indole H-4), 7.97 (d, 1H, J = 9.5 Hz,
coumarin H-4), 7.87 (s, 1H, indole H-2), 7.61 (d, 1H, J = 8.6 Hz, indole H-7), 7.56 (d, 1H,
J = 8.0 Hz, coumarin H-5), 7.50 (d, 1H, J = 7.6 Hz), 7.45 (d, 1H, J = 3.6 Hz), 7.42 (d, 1H, J
=
7.8 Hz), 7.23 (t, 1H, J = 7.0 Hz, indole H-6), 7.18 (t, 1H, J = 7.2 Hz, indole H-5), 7.14
(dd, 1H, J = 2.0 and 8.3 Hz), 6.97 (d, 1H, J = 1.6 Hz, coumarin H-8), 6.92 (dd, 1H, J = 1.9
and 8.6 Hz, coumarin H-6), 6.28 (d, 1H, J = 9.5 Hz, coumarin H-3), 4.41 (t, 2H, J = 6.6 Hz,
CH ), 4.04 (t, 2H, J = 5.7 Hz, CH ), 3.83 (s, 3H, OCH ), 2.28 (quint, 2H, J = 6.9 Hz, CH );
2
2
3
2
1
3
C NMR (DMSO-d , 100 MHz): δ 162.2 (CONH), 161.5 (Ar C-3), 160.3 (coumarin C=O),
6
1
59.2 (coumarin C-7), 155.3, 144.4 (coumarin C-4), 144.3 (C=N), 136.9, 135.4, 133.1
(indole C-2), 129.6 (coumarin C-5), 129.5, 124.9, 122.8, 122.3, 120.7, 119.7, 116.9, 112.8,
1
1
12.7,
112.5,
112.4,
111.2,
110.2
(indole
C-7),
01.3 (coumarin C-8), 65.5 (CH ), 55.3 (OCH ), 42.6 (CH ), 29.0 (CH ); APCI-MS
2
3
2
2
2
4

+
+
calculated for C H N O [M+H] 496, found m/z 496 [M+H] ; anal. HPLC t = 4.8 min,
2
9
25
3
4
R
>
99.0% at 300 nm.
4
.3.3.10. (E)-3-ethoxy-N'-((1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-indol-3-
yl)methylene) benzohydrazide (19c)
ᵒ
-1
White solid; yield 57%; m.p. 248-249 C; IR (KBr): ʋ cm 3443, 1728, 1641, 1610, 1555,
max
1
1
1
7
386, 1283, 1122, 996, 745; H NMR (DMSO-d , 400 MHz): δ 11.48 (s, 1H, NH), 8.57 (s,
6
H, CH=N), 8.31 (d, 1H, J = 7.6 Hz, indole H-4), 7.98 (d, 1H, J = 9.5 Hz, coumarin H-4),
.88 (s, 1H, indole H-2), 7.61 (d, 1H, J = 8.6 Hz, indole H-7), 7.56 (d, 1H, J = 8.1 Hz,
coumarin H-5), 7.49-7.39 (m, 3H), 7.23 (t, 1H, J = 7.1 Hz, indole H-6), 7.18 (t, 1H, J = 7.1
Hz, indole H-5), 7.12 (d, 1H, J =7.9 Hz), 6.98 (d, 1H, J = 2.0 Hz, coumarin H-8), 6.93 (dd,
1
H, J = 1.9 and 8.6 Hz, coumarin H-6), 6.28 (d, 1H, J = 9.5 Hz, coumarin H-3), 4.41 (t, 2H,
J = 6.6 Hz, CH ), 4.09 (q, 2H, J = 6.9 Hz, OCH ), 4.05 (t, 2H, J = 5.8 Hz, CH ), 2.28 (quint,
2
2
2
1
3
2
1
H, J = 6.8 Hz, CH ), 1.36 (t, 3H, J = 7.1 Hz, CH ); C NMR (DMSO-d , 100 MHz): δ
2 3 6
62.2 (CONH), 161.5 (Ar C-3), 160.3 (coumarin C=O), 158.4 (coumarin C-7), 155.3, 144.4
(coumarin C-4), 144.3 (C=N), 136.9, 135.3, 133.1 (indole C-2), 129.6 (coumarin C-5),
1
1
29.5, 124.8, 122.8, 122.3, 120.7, 119.6, 117.3, 113.3, 112.7, 112.6 (indole C-3), 112.4,
11.2, 110.2 (indole C-7), 101.3 (coumarin C-8), 65.5 (CH ), 63.3 (OCH ), 42.6 (CH ), 29.0
2
2
2
+
(
CH ), 14.6 (CH ); APCI-MS calculated for C H N O [M+H] 510, found m/z 510
2 3 30 27 3 5
+
[
M+H] ; anal. HPLC t = 5.9 min, 97.8% at 329 nm.
R
4
.3.3.11. (E)-4-ethoxy-N'-((1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-indol-3-
yl)methylene) benzohydrazide (19d)
ᵒ
-1
White solid; yield 55%; m.p. 251-252 C; IR (KBr): ʋ cm 3437, 2083, 1639, 1613, 1555,
max
1
1
1
7
386, 1279, 1044, 833, 750; H NMR (DMSO-d , 400 MHz): δ 11.41 (s, 1H, NH), 8.56 (s,
6
H, CH=N), 8.31 (d, 1H, J = 7.5 Hz, indole H-4), 7.98 (d, 1H, J = 9.5 Hz, coumarin H-4),
.88 (3H, overlapped aromatic protons), 7.61 (d, 1H, J = 8.6 Hz, indole H-7), 7.55 (d, 1H, J
=
7.9 Hz), 7.24-7.15 (m, 2H), 7.03 (d, 2H, J = 8.4 Hz, Ar H-3,5), 6.98 (s, 1H, coumarin H-
8
2
), 6.93 (d, 1H, J = 8.6 Hz, coumarin H-6), 6.28 (d, 1H, J = 9.5 Hz, coumarin H-3), 4.40 (t,
H, J = 5.8 Hz, CH ), 4.09 (q, 2H, J = 6.4 Hz, OCH ), 4.04 (t, 2H, J = 5.1 Hz, CH ), 2.28
2
2
2
1
3
(
quint, 2H, J = 6.3 Hz, CH ), 1.34 (t, 3H, J = 6.7 Hz, CH ); C NMR (DMSO-d , 100 MHz):
2 3 6
δ 161.9 (CONH), 161.5 (Ar C-4), 160.9 (coumarin C=O), 160.3, 155.3, 144.3 (coumarin C-
), 143.7 (C=N), 136.9, 132.8 (indole C-2), 129.5 (coumarin C-5), 129.3 (Ar C-2,6), 125.9
Ar C-1), 124.9, 122.7 (indole C-6), 122.3 (indole C-4), 120.6 (indole C-5), 114.0, 112.7,
3
(
1
12.5, 112.4, 111.3, 110.2 (indole C-7),101.3 (coumarin C-8), 65.5 (CH ), 63.3 (OCH ),
2
2
2
5

+
4
2.6 (CH ), 29.0 (CH ), 14.6 (CH ); APCI-MS calculated for C H N O [M+H] 510,
2 2 3 30 27 3 5
+
found m/z 510 [M+H] ; anal. HPLC t = 4.6 min, >99.0% at 290 nm.
R
4
.3.3.12. (E)-3-methyl-N'-((1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-indol-3-
yl)methylene) benzohydrazide (19e)
ᵒ
-1
White solid; yield 39%; m.p. 212-213 C; IR (KBr): ʋ cm 2936,1723,1611, 1463, 1384,
max
1
1
8
7
278, 1124, 749; H NMR (DMSO-d , 400 MHz): δ 11.48 (s, 1H, NH), 8.56 (s, 1H, C=N),
6
.31 (d, 1H, J = 7.7 Hz, indole H-4), 7.98 (d, 1H, J = 9.5 Hz, coumarin H-4), 7.87 (s, 1H),
.72-7.69 (m, 2H), 7.62 (d, 1H, J = 8.6 Hz, indole H-7), 7.56 (d, 1H, J = 8.0 Hz, coumarin
H-5), 7.39 (m, 2H), 7.23 (t, 1H, J = 8.4 Hz, indole H-6), 7.18 (t, 1H, J = 7.5 Hz, indole H-
5
1
2
1
), 6.97 (s, 1H, coumarin H-8), 6.93 (dd, 1H , J = 1.6 and 8.6 Hz, coumarin H-6), 6.28 (d,
H, J = 9.5 Hz, coumarin H-3), 4.41 (t, 2H, J = 6.6 Hz, CH ), 4.05 (t, 2H, J = 5.7 Hz, CH ),
2
2
1
3
.39 (s, 3H, CH ), 2.28 (quint, 2H, J = 6.3 Hz, CH ); C NMR (DMSO-d , 100 MHz): δ
3
2
6
62.6 (CONH), 161.5 (Ar C-3), 160.3 (coumarin C=O), 155.3, 144.3 (coumarin C-4), 144.2
(
C=N), 137.7, 136.9, 134.0, 132.9 (indole C-2), 131.9, 129.5, 128.3, 127.9, 124.8, 124.6,
22.7 (indole C-6), 122.3 (indole C-4), 120.7 (indole C-5), 112.7, 112.5, 112.4, 111.2, 110.2
indole C-7), 101.3 (coumarin C-8), 65.5 (CH ), 42.6 (CH ), 29.0 (CH ), 20.9 (CH ); APCI-
1
(
2
2
2
3
+
+
MS calculated for C H N O [M+H] 480, found m/z 480 [M+H] ; anal. HPLC t = 4.7
2
9
25
3
4
R
min, >99.0% at 290 nm.
4
.3.3.13. (E)-4-methyl-N'-((1-(3-((2-oxo-2H-chromen-7-yl)oxy)propyl)-1H-indol-3-
yl)methylene) benzohydrazide (19f)
ᵒ
-1
White solid; yield 36%; m.p. 221-222 C; IR (KBr): ʋ cm 2931, 1727, 1612, 1384, 1277,
max
1
1
8
7
7
1
1
2
1
126, 834, 750; H NMR (DMSO-d , 400 MHz): δ 11.44 (s, 1H, NH), 8.57 (s, 1H, Ar C-4),
6
.31 (d, 1H, J = 7.6 Hz, indole H-4), 7.97 (d, 1H, J = 9.6 Hz, coumarin H-4), 7.87 (s, 1H),
.83 (d, 2H, J = 8.0 Hz), 7.62 (d, 1H, J = 8.6 Hz), 7.56 (d, 1H, J = 8.0 Hz). 7.32 (d, 2H, J =
.9 Hz), 7.22 (t, 1H, J = 8.5 Hz, indole H-6), 7.17 (t, 1H, J = 7.9 Hz, indole H-5), 6.98 (d,
H, J = 1.8 Hz, coumarin H-8), 6.93 (dd, 1H, J = 2.1 and 8.6 Hz, coumarin H-6), 6.28 (d,
H, J = 9.5 Hz, coumarin H-3), 4.41 (t, 2H, J = 7.2 Hz, CH ), 4.05 (t, 2H, J = 5.8 Hz, CH ),
2
2
1
3
.37 (s, 3H, CH ), 2.28 (quint, 2H, J = 6.0 Hz, CH ); C NMR (DMSO-d , 100 MHz): δ
3
2
6
62.3 (CONH), 161.5 (Ar C-4), 160.2 (coumarin C=O), 155.3, 144.3 (coumarin C-4), 144.0
C=N), 141.2, 136.9, 132.9 (indole C-2), 131.1, 129.5 (coumarin C-5), 128.9, 127.4, 124.8,
22.7 (indole C-6), 122.3 (indole C-4), 120.6 (indole C-5), 112.6, 112.5, 112.4, 111.2, 110.2
indole C-7), 101.3 (coumarin C-8), 65.5 (CH ), 42.6 (CH ), 28.9 (CH ), 20.9 (CH ); APCI-
(
1
(
2
2
2
3
2
6

+
+
MS calculated for C H N O [M+H] 480, found m/z 480 [M+H] ; anal. HPLC t = 4.6
2
9
25
3
4
R
min, >99.0% at 290 nm.
4
.3.3.14. (E)-3-methoxy-N'-((1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (21a)
ᵒ
-1
White solid; yield 29%; m.p. 255-256 C; IR (KBr): ʋ cm 2917, 2849, 1713, 1618, 1565,
max
1
1
382, 1275, 934, 749; H NMR (DMSO-d , 400 MHz): δ 11.53 (s, 1H, NH), 8.62 (s, 1H,
6
CH=N), 8.32 (d, 1H, J = 7.8 Hz, indole H-4), 8.05 (s, 1H, indole H-2), 7.71 (d, 1H, J = 8.3
Hz, coumarin H-5), 7.63 (d, 1H, J = 7.9 Hz, coumarin H-7), 7.59 (t, 1H, J = 7.4 Hz), 7.50
(d, 1H, J = 7.6 Hz), 7.45-7.41 (m, 2H), 7.33-7.19 (m, 4H), 7.13 (dd, 1H, J = 1.8 and 8.1 Hz),
5
3
1
.89 (s, 1H, coumarin H-3), 4.77 (t, 2H, J = 4.7 Hz, CH ), 4.57 (t, 2H, J = 4.2 Hz, CH ),
2 2
1
3
.82 (s, 3H, CH ); C NMR (DMSO-d , 100 MHz): δ 164.5 (coumarin C-4), 162.2 (CONH),
3
6
61.4 (coumarin C=O), 159.2 (Ar C-3), 152.7, 144.4 (CH=N), 137.2, 135.4 (Ar C-1), 133.5
(indole C-2), 132.8, 129.6, 124.9, 124.0, 122.8, 122.3, 120.9, 119.7, 117.0, 116.4, 114.9,
1
12.8, 111.5 (indole C-3), 110.6 (indole C-7), 91.0 (coumarin C-3), 68.5 (CH ), 55.3
2
+
(
OCH ), 44.6 (CH ); APCI-MS calculated for C H N O [M+H] 482, found m/z 482
3
2
28 23
3
5
+
[
M+H] ; anal. HPLC t = 3.9 min, >99.0% at 315 nm.
R
4
.3.3.15. (E)-3-ethoxy-N'-((1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (21b)
ᵒ
-1
White solid; yield 32%; m.p. 239-240 C; IR (KBr): ʋ cm 3203, 3061, 2932, 1719, 1620,
max
1
1
8
1
566, 1382, 1276, 1238, 1183, 748; H NMR (DMSO-d , 400 MHz): δ 11.51 (s, 1H, NH),
6
.61 (s, 1H, CH=N), 8.32 (d, 1H, J = 7.8 Hz, indole H-4), 8.05 (s, 1H, indole H-2), 7.71 (d,
H, J = 8.2 Hz, coumarin H-5), 7.64 (d, 1H, J = 7.9 Hz, coumarin H-7), 7.59 (t, 1H, J = 8.2
Hz), 7.49-7.39 (m, 3H), 7.34-7.19 (m, 4H), 7.11 (d, 1H, J = 6.7 Hz), 5.89 (s, 1H, coumarin
H-3), 4.76 (t, 2H, J = 4.2 Hz, CH ), 4.57 (t, 2H, J = 4.5 Hz, CH ), 4.09 (q, 2H, J = 6.9 Hz,
2
2
1
3
OCH ), 1.35 (t, 3H, J = 6.9 Hz, CH ); C NMR (DMSO-d , 100 MHz): δ 164.5 (coumarin
2
3
6
C-4), 162.2 (CONH), 161.5 (coumarin C=O), 158.4 (Ar C-3), 152.7, 144.3 (CH=N), 137.2,
1
1
6
35.3 (Ar C-1), 133.5 (indole C-2), 132.8, 129.6, 124.9, 124.0, 122.8, 122.3, 120.9, 119.6,
17.3, 116.4, 114.9, 113.3, 111.5 (indole C-3), 110.6 (indole C-7), 90.9 (coumarin C-3),
8.5 (CH ), 63.3 (OCH ), 44.6 (CH ), 14.6 (CH ); ESI-MS calculated for C H N O
2
2
2
3
29 25
3
5
+
+
[
M+Na] 518, found m/z 518 [M+Na] ; anal. HPLC t = 4.3 min, >99.0% at 309 nm.
R
4
.3.3.16. (E)-4-ethoxy-N'-((1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (21c)
2
7

ᵒ
-1
White solid; yield 35%; m.p. 182-183 C; IR (KBr): ʋ cm 3419, 1725, 1610, 1383, 1258,
max
1
1
119, 1045, 832, 742; H NMR (DMSO-d , 400 MHz): δ 11.41 (s, 1H, NH), 8.59 (s, 1H,
6
CH=N), 8.31 (d, 1H, J = 7.8 Hz, indole H-4), 8.03 (s, 1H, indole H-2), 7.89 (d, 2H, J = 8.6
Hz), 7.71 (d, 1H, J = 8.4 Hz, coumarin H-5), 7.66 (d, 1H, J = 7.4 Hz), 7.61 (t, 1H, J = 8.2
Hz), 7.36-7.26 (m, 3H), 7.21 (t, 1H, J = 7.6 Hz), 7.03 (d, 2H, J = 8.4 Hz), 5.91 (s, 1H,
coumarin H-3), 4.77 (t, 2H, J = 4.3 Hz, CH ), 4.59 (t, 2H, J = 3.9 Hz, CH ), 4.10 (q, 2H, J
2
2
1
3
=
7.1 Hz, OCH ), 1.35 (t, 3H, J = 7.0 Hz, CH ); C NMR (DMSO-d , 100 MHz): δ 164.4
2 3 6
(
coumarin C-4), 161.9 (CONH), 161.4 (coumarin C=O), 160.9 (Ar C-4), 152.7, 143.6
CH=N), 137.1, 133.1 (indole C-2), 132.8, 129.3, 125.8, 124.9, 124.0, 122.8, 122.7, 122.2,
(
1
6
20.7, 116.4, 114.9, 114.0, 111.6 (indole C-3), 110.5 (indole C-7), 90.9 (coumarin C-3),
8.5 (CH ), 63.3 (OCH ), 44.6 (CH ), 14.5 (CH ); APCI-MS calculated for C H N O
5
2
2
2
3
29 25
3
+
+
[
M+H] 496, found m/z 496 [M+H] ; anal. HPLC t = 4.2 min, >99.0% at 326 nm.
R
4
.3.3.17. (E)-3-methyl-N'-((1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (21d)
ᵒ
-1
White solid; yield 25%; m.p. 219-220 C; IR (KBr): ʋmax cm 2917, 2849,1726, 1463, 1386,
1
1
264, 744; H NMR (DMSO-d , 400 MHz): δ 11.50 (s, 1H, NH), 8.60 (s, 1H, CH=N), 8.31
6
(
d, 1H, J = 7.7 Hz, indole H-4), 8.04 (s, 1H, indole H-2), 7.72-7.69 (m, 3H), 7.65 (d, 1H, J
7.9 Hz), 7.61 (t, 1H, J = 8.1 Hz), 7.42-7.34 (m, 3H), 7.29 (dd, 2H, J = 8.1 and 15.9 Hz),
.22 (t, 1H, J = 7.5 Hz), 5.91 (s, 1H, coumarin H-3), 4.77 (t, 2H, J = 5.2 Hz, CH ), 4.58 (t,
=
7
2
2
1
3
H, J = 4.2 Hz, CH ), 2.39 (s, 3H, CH ); C NMR (DMSO-d , 100 MHz): δ 164.5 (coumarin
2
3
6
C-4), 162.6 (CONH), 161.4 (coumarin C=O), 152.7, 144.1 (CH=N), 137.7, 137.2, 134.0,
1
1
33.4 (indole C-2), 132.8, 131.9, 128.3, 127.9, 124.9, 124.6, 124.0, 122.8, 122.3, 120.9,
16.4, 114.9, 111.6 (indole C-3), 110.6 (indole C-7), 91.0 (coumarin C-3), 68.6 (CH ), 44.6
2
+
(
CH ), 20.9 (CH ); APCI-MS calculated for C H N O [M+H] 466, found m/z 466
2
3
28 23
3
4
+
[
M+H] ; anal. HPLC t = 4.2 min, >99.0% at 320 nm.
R
4
.3.3.18. (E)-4-methyl-N'-((1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (21e)
ᵒ
-1
White solid; yield 22%; m.p. 240-241 C; IR (KBr): ʋ cm 3193, 3006, 2864, 1749, 1637,
max
1
1
1
7
8
613, 1463, 1336, 1119, 744; H NMR (DMSO-d , 400 MHz): δ 11.48 (s, 1H, NH), 8.61 (s,
6
H, CH=N), 8.31 (d, 1H, J = 7.8 Hz, indole H-4), 8.04 (s, 1H, indole H-2), 7.82 (d, 2H, J =
.8 Hz), 7.71 (d, 1H, J = 8.2 Hz, coumarin H-5), 7.65 (d, 1H, J = 7.8 Hz), 7.61 (t, 1H, J =
.1 Hz), 7.35-7.26 (m, 5H), 7.21 (t, 1H, J = 7.6 Hz), 5.91 (s, 1H, coumarin H-3), 4.77 (t, 2H,
1
3
J = 4.2 Hz, CH ), 4.58 (t, 2H, J = 4.8 Hz, CH ), 2.37 (s, 3H, CH ); C NMR (DMSO-d ,
2
2
3
6
2
8

1
00 MHz): δ 164.5 (coumarin C-4), 162.3 (CONH), 161.4 (coumarin C=O), 152.7
(coumarin H-8a), 144.0 (CH=N), 141.3, 137.2 (indole C-7a), 133.3 (indole C-2), 132.8,
1
1
31.1, 128.9, 127.5, 124.9, 124.1, 122.8, 122.3, 120.8, 116.4, 114.9, 111.6 (indole C-3),
10.5 (indole C-7), 91.0 (coumarin C-3), 68.6 (CH ), 44.6 (CH ), 21.0 (CH ); APCI-MS
2
2
3
+
+
calculated for C H N O [M+H] 466, found m/z 466 [M+H] ; anal. HPLC t = 4.2 min,
2
8
23
3
4
R
>
99.0% at 325 nm.
4
.3.3.19. (E)-4-methoxy-N'-((1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indol-3-
yl)methylene) benzohydrazide (21f)
ᵒ
-1
White solid; yield 21%; m.p. 268-269 C; IR (KBr): ʋ cm 3208, 2917, 2847, 1711, 1638,
max
1
1
613, 1554, 1259; H NMR (DMSO-d , 400 MHz): δ 11.42 (s, 1H, NH), 8.60 (s, 1H,
6
CH=N), 8.31 (d, 1H, J = 7.8 Hz, indole H-4), 8.03 (s, 1H, indole H-2), 7.91 (d, 2H, J = 8.5
Hz), 7.71 (d, 1H, J = 8.2 Hz, coumarin H-5), 7.64 (d, 1H, J = 7.8 Hz), 7.61 (t, 1H, J = 7.8
Hz), 7.34 (d, 1H, J = 8.4 Hz), 7.28 (dd, 2H, J = 7.7 and 15.4 Hz), 7.21 (t, 1H, J = 7.5 Hz),
7
2
.05 (d, 2H, J = 8.4 Hz), 5.90 (s, 1H, coumarin H-3), 4.76 (t, 2H, J = 5.1 Hz, CH ), 4.58 (t,
2
1
3
H, J = 4.3 Hz, CH ), 3.83 (s, 3H, OCH ); C NMR (DMSO-d , 100 MHz): δ 164.5
2
3
6
(
coumarin C-4), 161.9 (CONH), 161.7 (coumarin C=O), 161.4 (Ar C-4), 152.7 (coumarin
C-8a), 143.7 (CH=N), 137.1, 133.2 (indole C-2), 132.8, 129.3, 125.9, 124.9, 124.0, 122.8,
22.7, 122.3, 120.8, 116.4, 114.9, 113.6, 111.6 (indole C-3), 110.5 (indole C-7), 91.0
coumarin C-3), 68.5 (CH ), 55.4 (OCH ), 44.6 (CH ); APCI-MS calculated for C H N O
1
(
[
2
3
2
28 23
3
5
+
+
M+H] 482, found m/z 482 [M+H] ; anal. HPLC t = 5.0 min, 97.3% at 327 nm.
R
4
.3.3.20. (E)-N'-((1-(2-((2-oxo-2H-chromen-4-yl)oxy)ethyl)-1H-indol-3-yl)methylene)
benzohydrazide (21g)
ᵒ
-1
White solid; yield 20%; m.p. 190-191 C; IR (KBr): ʋ cm 3015, 2937, 1725, 1611, 1553,
max
1
1
1
7
384, 1277, 1176, 834, 751; H NMR (DMSO-d , 400 MHz): δ 11.55 (s, 1H, NH), 8.61 (s,
6
H, CH=N), 8.31 (d, 1H, J = 7.8 Hz, indole H-4), 8.05 (s, 1H, indole H-2), 7.91 (d, 2H, J =
.2 Hz), 7.72 (d, 1H, J = 8.2 Hz), 7.65 (d, 1H, J = 7.8 Hz), 7.61-7.50 (m, 4H), 7.56 (d, 1H,
J = 7.1 Hz),7.35 (d, 1H, J = 8.5 Hz), 7.29 (dd, 2H, J= 7.6 and 15.1 Hz), 7.22 (t, 1H, J = 7.5
Hz), 5.91 (s, 1H, coumarin H-3), 4.77 (t, 2H, J = 4.4 Hz, CH ), 4.58 (t, 2H, J = 4.4 Hz, CH );
2
2
1
3
C NMR (DMSO-d , 100 MHz): δ 164.5 (coumarin C-4), 162.5 (CONH), 161.4 (coumarin
6
C=O), 152.7 (coumarin C-8a), 144.2 (CH=N), 137.2, 134.0, 133.5 (indole C-2), 132.8,
1
1
31.4, 128.4, 127.5, 124.9, 124.1, 122.8, 122.3, 120.9, 116.4, 114.9, 111.5 (indole C-3),
10.5 (indole C-7), 91.0 (coumarin C-3), 68.5 (CH ), 44.6 (CH ); APCI-MS calculated for
2
2
2
9