Synthesis and biological screening of 5-(alkyl(1H-indol-3-yl))-2- (substituted)-1,3,4-oxadiazoles as antiproliferative and anti-inflammatory agents

Article abstract of DOI:10.1016/j.ejmech.2013.05.024

A series of 5-(alkyl(1H-indol-3-yl))-2-(substituted)-1,3,4-oxadiazoles were efficiently synthesized by oxidative cyclisation of N0 -benzylidene-(1H-indol- 3-yl)alkane hydrazides using di(acetoxy)iodobenzene. N0 -Benzylidene-(1H-indol- 3-yl)alkane hydrazid

Full text of DOI:10.1016/j.ejmech.2013.05.024

Accepted Manuscript
Synthesis and biological screening of 5-(alkyl (1H-indol-3-yl))-2-(substituted)-1,3,4-
oxadiazoles as antiproliferative and anti-inflammatory agents
Sreevani Rapolu, Manjula Alla, Vittal Rao Bommena, Ramalinga Murthy, Nishant
Jain, Venkata Ramya Bommareddy, Madhava Reddy Bommineni
PII:
S0223-5234(13)00333-4
10.1016/j.ejmech.2013.05.024
EJMECH 6202
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 12 February 2013
Revised Date: 12 April 2013
Accepted Date: 19 May 2013
Please cite this article as: S. Rapolu, M. Alla, V.R. Bommena, R. Murthy, N. Jain, V.R. Bommareddy,
M.R. Bommineni, Synthesis and biological screening of 5-(alkyl (1H-indol-3-yl))-2-(substituted)-1,3,4-
oxadiazoles as antiproliferative and anti-inflammatory agents, European Journal of Medicinal Chemistry
(2013), doi: 10.1016/j.ejmech.2013.05.024.
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ACCEPTED MANUSCRIPT
Graphical abstract:
Synthesis and biological screening of 5-(alkyl(1H-indol-3-yl))-2-(substituted)-1,3,4-
oxadiazoles as anti-proliferative and anti-inflammatory agents
a
a
a
b
b
Sreevani Rapolu , Manjula Alla ,* Vittal Rao Bommena , Ramalinga Murthy , Nishant Jain
,
c
c
Bommareddy Venkata Ramya , Madhava Reddy
a
Crop Protection Chemicals Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad, 500607.
Centre for Chemical Biology, Indian Institute of Chemical Technology, Tarnaka, Hyderabad, 500607.
b
c
Department of pharmaceutical Chemistry, G. Pulla Reddy College of Pharmacy, Mehdipatnam, Hyderabad,
5
00028, India. E-mail: manjula@iict.res.in, manjula_alla@yahoo.com
A series of 5-(alkyl(1H-indol-3-yl))-2-(substituted)-1,3,4-oxadiazoles were synthesized and
evaluated for anti-proliferative activity against four different cancer cell lines and anti-
inflammatory activity. A correlation between the anti-proliferative anti-inflammatory activities
has been established.
O
N
N
n
n
OH
O
R
N
N
H
H

ACCEPTED MANUSCRIPT
Highlights
•
•
•
•
•
Titled compounds were synthesized using DIB mediated oxidative cyclisation.
Anti-inflammatory & anti-proliferative activities screened exhibit correlation.
Compound 6i and 6t showed better inhibition of paw edema compared to standard.
In vitro cytotoxicity evaluated against A-549, HeLa, HepG-2 and Du145 cancer cells.
6i, 6q and 6t are identified as good candidates against all the cancer cell lines tested.

ACCEPTED MANUSCRIPT
Synthesis and biological screening of 5-(alkyl (1H-indol-3-
yl))-2-(substituted)-1,3,4-oxadiazoles as antiproliferative and
anti-inflammatory agents
a
a,
a,
Sreevani Rapolu , Manjula Alla *, Vittal Rao Bommena *, Ramalinga
b
b
c
Murthy , Nishant Jain , Venkata Ramya Bommareddy , Madhava Reddy
c
Bommineni
a
b
Crop Protection Chemicals Division, Centre for Chemical Biology, CSIR-Indian Institute of Chemical Technology,
Tarnaka, Hyderabad, 500607.
c
Department of pharmaceutical Chemistry, G. Pulla Reddy College of Pharmacy, Mehdipatnam, Hyderabad,
5
00028, India.
E-mail: manjula@iict.res.in
Tel: 091 040 27191441; Fax: 091 040 27193382
Abstract A series of 5-(alkyl(1H-indol-3-yl))-2-(substituted)-1,3,4-oxadiazoles were efficiently
synthesized by oxidative cyclisation of N'-benzylidene-(1H-indol-3-yl)alkane hydrazides using
di(acetoxy)iodobenzene. N'-benzylidene-(1H-indol-3-yl)alkane hydrazides themselves were
derived from simple indole-3-carboxylic acids. The 5-(alkyl(1H-indol-3-yl))-2-(substituted)-
1
,3,4-oxadiazoles were evaluated for their anti-inflammatory and anti-proliferative activities.
Based on the results obtained structure and activity relationship (SAR) was established and a
correlation between the activities was observed. Compound 6i and 6t showed best activity
against proliferation of human cancer cell lines and as well as inflammation of rat paw edema.
Keywords: Indole-3-carboxlic acids, Indolyl-1,3,4-oxadiazoles, Antiproliferative agents, Anti-
inflammatory agents.
1

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1
. Introduction
Inflammation is a major cause in chronic illnesses, including diabetes, cardiovascular
disease, arthritis, psoriasis, and cancer [1]. Cancer, one of the prime life threat causes in the
present society. Chronic inflammation increases the threat of various cancers, indicating that
eliminating inflammation may represent a valid strategy for cancer prevention and therapy [2].
Investigation of new therapeutic agents for the treatment of cancer has become a major area of
research owing to its resistance to conventional single drug chemotherapeutic agents [3]. Since
mono-therapy is generally insufficient for treating cancer, the combined use of anti-inflammatory
agents and conventional cancer therapy is gaining attention as a new therapeutic approach.
Moreover, non steroidal anti-inflammatory drugs (NSAIDs) are in general recognized as
prototypical chemo-preventive agents against many forms of cancers [4].
Indole, the most active pharmacodynamic nucleus in nature [5], has been a major
constituent of number of bio-molecules such as a plant growth regulator hormone indole-3-acetic
acid, an amino acid tryptophan, the hormones serotonin and melatonin. It is also incorporated in
various natural products such as alkaloids [6]. In particular, 3-substituted indole derivatives have
been found to play an important role in many biologically active compounds especially with anti-
inflammatory, antitumor, hypoglycemic, analgesic and antipyretic activities [7]. Clinically
effective agents like anti-inflammatory drug indomethacin, the psychotropic drug LSD and the
anti-tumor agent vinblastine are few of the representative compounds possessing 3-substituted
indoles nucleus [8]. Recent reports on naturally occurring 5-(3’-indolyl)oxazoles indicate that
they are endowed with diverse biological activities [9-10], where Labradorin 1 (a) and
Labradorin 2 (b) (Figure 1) were found to exhibit anticancer activity against NCI-H 460 (lung-
NSC) with GI50 values 9.8 and 9.6 µg/ML, respectively [11]. Among the azoles, 1,3,4-
oxadiazoles have received a great deal of attention owing to their simple structure and wide
variety of pharmacological activities such as anti-inflammatory and anti-edema [12], anticancer
[
13], analgesic, antibacterial [14], antifungal, anticonvulsant [15] etc.
Non-steroidal anti-inflammatory drugs like indomethacin (c) and tenidap (d) have led to
exploration of indole ring, especially by modifying it at C-3 position. These modifications
mainly include the introduction of alkyl and heterocyclic groups to increasing its
pharmacological efficacy [16-17].Encouraged by the above observations and considering the
interesting anti-inflammatory and cytotoxic profiles of 3-substituted indoles, a project has been
2

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conceived to synthesize 1,3,4-oxadiazole skeleton appended to the C-3 position of the indole ring
with varying alkyl linkers between the two active heterocyclic units. The program also aims to
introduce diversity in substitutions at C-2 position of oxadiazole ring with (un)substituted phenyl
group to study the synergic effect on the pharmacological profile. These newly synthesized
compounds would be evaluated for anti-inflammatory and antiproliferative activities, with a view
to study the structure-activity relationship.
Fig. 1 Some of the biologically active 3-substituted indole representatives.
2
. Results and Discussion
.1 Chemistry
2
Synthesis of the 5-(alkyl(1H-indol-3-yl))-2-(substituted)-1,3,4-oxadiazoles, has been
accomplished by the simple chemical reactions outlined in the Scheme 1 below. Indole-3-
carboxylic acids namely, indole-3-propionic and indole-3-butyric acids are selected as starting
materials thus fixing the two different alkyl chain linkers for present study. Diversity at C-2
position of oxadiazole ring was envisaged by introducing various aromatic and hetero aromatic
aldehydes at an appropriate stage in the synthesis.
Esterification of the indole-3-carboxylic acids 1(a-b) was achieved with ethanol and
catalytic amount of con.H SO to afford the corresponding esters 2(a-b). The reaction of esters
2
4,
with 99% hydrazine monohydrate in ethanol medium produced the corresponding hydrazides
(a-b). Refluxing the hydrazides with various aldehydes 4(a-r) in ethanol for 5h resulted in the
3
formation of hydrazone intermediates 5(a-v).Target compounds 6(a–v) (Table 1) were accessed
by oxidative cyclisation of hydrazones using a benign and non-toxic hypervalent iodine reagent,
di(acetoxy)iodobenzene (DIB) [18–20]. All the synthesized compounds were characterized by
1
H NMR and MS data.
Scheme 1. Synthesis of compounds 6(a-v), Reagents and conditions: (a) H SO reflux, 3-4h (b)
2
4,
NH NH .H O (99%), EtOH, reflux, 5-6h. (c) EtOH, reflux, 4-5h. (d) DIB, DCM, rt, 4-6h.
2
2
2
Table 1 Synthesized 5-(3-(indolyl)alkyl)-2-(substituted)-1,3,4-oxadiazoles.
3

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Pharmacology
.1 In vivo anti-inflammatory activity
3
The in vivo anti-inflammatory screening of the synthesized compounds was carried out
by employing the carrageenan-induced paw edema bioassay in rats [21]. From the results
obtained (Table 2), it has been noticed that all the tested oxadiazole derivatives exhibit
considerable inhibition of inflammation i.e., paw-edema. In addition, it has been noticed that,
several synthetic compounds (6f, 6h, 6i, 6k, 6q, 6t) reveal remarkable inhibition of paw-edema
(61.0-70.9% inhibition of edema) comparable to that of Ibuprofen which is used as a reference
standard (72.8% inhibition of edema). Compound 6i exhibit better inhibition of inflammation
(78.3% inhibition of edema) compared to that of the reference standard (Ibuprofen) at the end of
rd
3
hour (Table 3).
Another feature observed during the study is that, the analogues derived from indole-3-
propionic acid (n=2), show better anti-inflammatory properties than the analogues derived from
indole-3-butyric acid (n=3). Among the substitutions at C-2 position of the oxadiazole ring, 6i
having 4-chlorophenyl and 6t having m-phenoxyphenyl substitution shows inhibition of
inflammation comparable to that of the standard employed (Figure 2).
Table 2 Anti-inflammatory activity of 5-(3-(indolyl)alkyl)-2-(substituted)-1,3,4-oxadiazoles.
Table 3 Percentage protection against edema formation
Fig. 2. Graphical representation of the percentage protection of 5-(3-(indolyl)alkyl)-2-
(substituted)-1,3,4-oxadiazoles against edema formation.
3
.2 In vitro anticancer activity
The in vitro antiproliferative activity of the synthesized compounds were evaluated
against four human cancer cell lines, i.e., human epithelial lung carcinoma (A549), human
epithelial cervical cancer (HeLa), human liver carcinoma (HepG2), and human prostate cancer
(Du145) cells and the IC50 values determined are summarized in table 4. From the results
obtained (Table 4), it is clear that, all the 1,3,4-oxadiazoles reduce the cancer cell viability
significantly with IC values ranging from 20µM-100µM. MTT assay reveals that compounds
5
0
6
a, 6e, 6i, 6m, 6p, 6r, 6t and 6u are potent against all the cell lines at IC values less than
50
4

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5
0µM. Interestingly, majority of these active compounds are derived from indole-3-propionic
acid i.e., analogues having two carbon linker between the indole and oxadiazole (n=2).
The SAR study reveals that, alkyl linkers at C-5 position and substitutions on phenyl ring
at C-2 of the oxadiazole ring are playing an important role. Comparing the inhibitory
concentrations of the pairs (with similar substitution and variation in n) 6e and 6f, 6i and 6j, 6u
and 6v clearly indicate that, a shorter alkyl side chain (n=2) show relatively enhanced activity
than longer alkyl side chain (n=3). Compound 6i having 4-chlorophenyl substitution at C-2
position of the oxadiazole ring exhibited the effective cytotoxicity against all the four cell lines,
with the best inhibition concentrations 23.4 µM and 21.2 µM against HeLa and HepG2,
respectively. Compound 6q with 4-methoxyphenyl substitution at C-2 of oxadiazole ring showed
IC values 23.2 µM and 22.2 µM against A549 and HeLa, respectively, while 6t with C-2 meta-
5
0
phenoxyphenyl group also inhibited the proliferation of A549 (23.3 µM) and HeLa (25.4 µM)
cell lines. Comparison of these two compounds indicates that there is no selectivity between 4-
methoxyphenyl and 3-phenoxyphenyl groups with respect to bulkiness of the group or
substituent position. Compound 6a with a phenyl group at C-2 showed good activity against all
the cell lines. While 6b having 1-naphthyl ring at C-2 exhibited moderate activity against HepG2
(101.9 µM) and relatively good activity against all other. Introduction of 2,6-dichlorophenyl
group at the C-2 position of 1,3,4-oxadiazole ring in 6n results in reduction of activity against
different cancer cell lines except against HeLa (47.5 µM). On the other hand, 3,4-dichlorophenyl
group at the C-2 position in 6o proved to be a better in inhibition of cell proliferation against all
cell lines when compared 2,6-dichlorophenyl group. 2,4,6-trimethoxyphenyl group in 6s
displayed moderate activity against HepG2 (366.16 µM) and good with other cell lines (between
2
6.3-31.5 µM). Comparing the anti-inflammatory and antiproliferative activities reveal that,
compounds that inhibit inflammation also exhibit good antiproliferative activity. The best among
them are 6i and 6t both with n=2 linker.
Table 4 Anti-proliferative activity profile of synthesized 5-(3-(indolyl)alkyl)-2-(substituted)-
1
,3,4-oxadiazoles.
. Conclusion
3
5

ACCEPTED MANUSCRIPT
In conclusion, we have successfully synthesized 22 analogues of 5-(alkyl(1H-indol-3-
yl))-2-(substituted)-1,3,4-oxadiazole. These analogues were evaluated for their anti-
inflammatory and antiproliferative activities. Majority of the compounds showed good inhibition
of paw edema and cancer cell line growth. Compound 6i having 4-chloro phenyl substitution at
C-2 position of the oxadiazole ring exhibited better inhibition of inflammation than that of the
standard reference Ibuprofen, whereas the anti-inflammatory activity of 6t is comparable with
standard. Similarly, among the oxadiazoles tested for antiproliferative activity 6i exhibited better
inhibition concentration against all the cell lines. Compounds 6q and 6t displayed good
antiproliferative activity against all the cell lines. A correlation between the anti-inflammatory
and anti-proliferative activities among the 5-(alkyl(1H-indol-3-yl))-2-(substituted)-1,3,4-
oxadiazole analogues was observed. Interestingly, compound 6i and 6t proved to be good in both
the activities, thus justifying our contention that good anti-inflammatory agents are likely to good
antiproliferative agents as well. Studies on mode of action of these 5-(alkyl(1H-indol-3-yl))-2-
(substituted)-1,3,4-oxadiazoles, and improvisation of lead molecules as both anti-inflammatory
and antiproliferative agents is underway.
Experimental
5
.1 Chemistry
All the chemicals used are of synthetic grade procured from Sd-fine, Spectrochem and
Aldrich chemicals. Completion of the reactions was monitored by analytical thin layer
chromatography (TLC) using E-Merck 0.25 mm silica gel plates using ethyl acetate/hexane (4:6)
as eluting medium. Visualization was accomplished with UV light (256 nm) and iodine chamber.
Synthesized compounds were purified by column chromatography using a mixture of hexane and
ethyl acetate. All the solvents are dried using appropriate drying agents before use. By
employing standard laboratory techniques, the reagents are purified. Melting points were
1
13
determined on ANALAB melting point apparatus and are uncorrected. All the H and
C
spectra were recorded in CDCl and DMSO-D solvents unless otherwise mentioned. Chemical
3
6
shifts are reported on AVANCE 300 MHz, INNOVA 500 MHz and JCAMP DX-50 (300 MHz
1
13
for H and 75 MHz for C) relative to TMS internal standard on the δ-scale. The IR spectra were
recorded on SCHIMADZU FT-IR SPECTROPHOTOMETER by using 1% potassium bromide
6

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discs. The Electron Ionization mass spectra were recorded on Agilent 1100 series & HRMS done
on high resolution QSTAR XL Hybrid /MS system.
5
.2 General Procedure for Preparation of indole-3-carboxylates (2a-b):
The indole-3-carboxylic acids (1a-b) (10 mmol) were esterified in a classical manner
with ethanol and catalytic amount of con.H SO under reflux for 3 h. After completion, the
2
4
reaction mixture was cooled and solvent ethanol was removed under reduce pressure, The
residue was then poured onto crushed ice and treated with aq. NaOH solution (10%) drop wise
till the reaction mixture became slightly basic in nature. The solid product obtained was filtered,
washed with water and dried and characterized.
0
Ethyl-3-(1H-indol-3-yl)propanoate (2a): Yield: 95%; m. p.: 32-35 C; FTIR (KBr) ν (cm-1):
1
3
322 (N-H), 1718 (C=O), 1187 (C-O); H NMR (CDCl 300 MHz, ppm) : δ 1.23 (t, 3H, J = 7.2
3,
Hz, CH ), 2.69 (t, 2H, J = 7.7 Hz, CH ), 3.07 (t, 2H, J = 7.4 Hz, CH ), 4.12 (q, 2H, J = 7.2 &
3
2
2
1
4.2 Hz, CH ), 6.93 (s, 1H, ArH), 7.03-7.15 (m, 2H, ArH), 7.27 (d, 1H, J = 7.9 Hz, ArH), 7.55
2
+
(
d, 1H, J = 7.7 Hz, ArH), 7.9 (s, 1H, -NH); MS (ESI) m/z : 217 [M] .
0
Ethyl-4-(1H-indol-3-yl)butanoate (2b): Yield: 80%; m. p.: 35-37 C; FTIR (KBr) ν (cm-1): 3334
1
(
N-H), 1720 (C=O), 1185 (C-O); H NMR (CDCl 300 MHz, ppm) : δ 1.24 (t, 3H, J = 7.0 Hz,
3
,
CH ), 1.98 -2.07 (m, 2H, CH ), 2.34 (t, 2H, J = 7.4 Hz, CH ), 2.79 (t, 2H, J = 7.4 Hz, CH ), 4.10
3
2
2
2
(
q, 2H, J = 7.2 & 14.2 Hz, CH ), 6.92 (s, 1H, ArH), 7.02-7.14 (m, 2H, ArH), 7.25 (d, 1H, J = 8.1
2
+
Hz, ArH), 7.55 (d, 1H, J = 7.7 Hz, ArH),7.87 (s, 1H, -NH), MS (EI) m/z: 231 [M] .
5
.3 General procedure for preparation of indole-3-carboxylic acid hydrazides (3a-b):
An aqueous solution of hydrazine hydrate (15 ml, 99%) was added to a solution of
appropriate indole-3-carboxylates (2a-b) (10 mmol) in ethanol (15 ml). The reaction mixture was
refluxed for 5 h. At the end, the reaction mixture was cooled and poured onto crushed ice
followed by extraction with ethyl acetate (3x10ml). The organic layer was dried over anhydrous
sodium sulphate and evaporated under reduced pressure to yield the product.
7

ACCEPTED MANUSCRIPT
0
3
-(1H-Indol-3-yl)propanehydrazide (3a): Yield: 92%; m. p.: 123-126 C; FTIR (KBr) ν (cm-1):
1
3
308 (N-H), 1638 (C=O); H NMR (CDCl +DMSO-d , 300 MHz, ppm) : δ 2.43 (t, 2H, J = 7.5
3
6
Hz, CH ), 2.99 (t, 2H, J = 7.5 Hz, CH ), 3.91 (s, 2H, -NH ), 6.92-7.04 (m, 3H, ArH), 7.30 (d, 1H
2
2
2
J = 7.9 Hz, ArH), 7.48 (d, 1H, J = 7.7 Hz, ArH), 8.88 (s, 1H, -NH), 10.41 (s, 1H, ArH); MS (EI)
+
m/z: 203 [M] .
0
4
3
2
6
7
-(1H-Indol-3-yl)butanehydrazide (3b): Yield: 93%; m. p.: 102-106 C; FTIR (KBr) ν (cm-1):
1
321, 3269 (N-H), 1667 (C=O); H NMR (CDCl +DMSO-d , 300 MHz, ppm) : δ 1.92-1.99 (m,
3
6
H, CH ); 2.13 (t, 2H, J = 6.8 Hz, CH ), 2.71 (t, 2H, J = 7.8 Hz, CH ), 3.89 (s, 2H, -NH ), 6.89-
2
2
2
2
.96 (m, 2H, ArH), 7.01 (t, 1H, J = 6.8 Hz, ArH), 7.27 (d, 1H, J = 7.8 Hz, ArH), 7.46 (d, 1H, J =
+
.8 Hz, ArH), 8.77 (s, 1H, -NH),10.29 (s, 1H, -NH), MS (EI) m/z: 217 [M] .
5
.4 General procedure for preparation of N'-benzylidene-(1H-indol-3-yl)alkane hydrazide (5a-
v):
A mixture of substituted benzaldehydes (4a-r) (1 mmol), indole-3-carboxylic acid
hydrazides (3a-b) (1 mmol) in ethanol were refluxed for 3-4 h. As the reaction progresses, the
N'-benzylidene-(1H-indol-3-yl)alkane hydrazide separates out as a solid product in the reaction
mixture and was collected by simple filtration. The product obtained so was dried and purified
by recrystallisation from hot ethylacetate/hexane.
N'-benzylidene-4-(1H-indol-3-yl)butanehydrazide (5a): White solid, Yield: 95%; m. p.: 146-
0
1
1
48 C; FTIR (KBr) ν (cm-1): 3279 (N-H), 1654 (C=O); H NMR (DMSO-d , 500 MHz, ppm) :
6
δ 1.99-2.05 (m, 2H, CH ), 2.70-2.73 (t, 2H, J = 7.5 Hz, CH ), 2.78-2.82 (t, 2H, J = 7.5 Hz, CH ),
2
2
2
6
.91-6.95 (q, 1H, J = 6.1 Hz, ArH), 7.00-7.04 (t, 2H, J = 6.8 Hz, ArH), 7.29-7.35 (m, 5H, ArH),
.49-7.54 (dd, 2H, J = 6.8 & 8.2 Hz, ArH), 7.90 (s, 1H, ArH), 10.42 (brs, 1H, -NH), 11.02 (brs,
7
+
1
H, -NH); MS (ESI) m/z: 306 [M+H] ; HRMS: m/z Calculated value C H ON Na = 328.1420,
19
19
3
Observed value = 328.1408.
N'-(naphthalen-1-ylmethylene)-4-(1H-indol-3-yl)butanehydrazide (5b): White solid, Yield: 86%;
0
1
m. p.: 155-157 C; FTIR (KBr) ν (cm-1): 3409 (N-H), 1669 (C=O); H NMR (DMSO-d , 300
6
MHz, ppm) : δ 2.03-2.13 (q, 2H, CH ), 2.77-2.87 (q, 4H, 2CH ), 6.90-7.02 (m, 3H, ArH), 7.28-
2
2
7
.31 (d, 1H, J = 7.9 Hz, ArH), 7.45-7.57 (m, 4H, ArH), 7.76-7.78 (d, 1H, J = 6.9 Hz, ArH), 7.93
(m, 2H, ArH), 8.60-8.79 (m, 2H, ArH), 10.39 (brs, 1H, -NH), 11.14 (brs, 1H, -NH); MS (ESI)
8

ACCEPTED MANUSCRIPT
+
m/z: 356 [M+H] ; HRMS: m/z Calculated value C H ON Na = 356.1733, Observed value =
21
23
3
3
56.1751.
N'-(pyridin-2-ylmethylene)-3-(1H-indol-3-yl)propanehydrazide (5c): White solid, Yield : 82%;
0
1
m.p. 201-202 C; FTIR (KBr) ν (cm-1): 3312 (N-H), 1697 (C=O); H NMR (CDCl 300 MHz,
3
,
ppm): δ 2.59 (s, 4H, 2CH ), 6.39-6.52 (m, 3H, ArH), 6.65-6.69 (d, 1H, J = 7.7 Hz, ArH), 6.88-
2
6
.92 (t, 1H, J = 7.3 Hz, ArH), 7.06-7.08 (d, 1H, J = 6.7 Hz, ArH), 7.22-7.26 (t, 1H, J = 7.5 Hz,
ArH), 7.48-7.51 (d, 1H, J = 7.3 Hz, ArH), 7.65-7.66 (d, 1H, J = 4.3 Hz, ArH), 8.08 (s, 1H,
+
ArH),10.20 (brs, 1H, -NH), 10.99 (brs, 1H, -NH); ESI Mass (m/z) 293 [M+Na] .
N'-(pyridin-3-ylmethylene)-3-(1H-indol-3-yl)propanehydrazide (5d): White solid, Yield : 84%;
0
1
m.p. 153-155 C; FTIR (KBr) ν (cm-1): 3285 (N-H), 1616 (C=O); H NMR (CDCl 300 MHz,
3
,
ppm): δ 2.98 (s, 4H, 2CH ),6.98-7.14 (m, 3H, ArH), 7.16-7.26 (m, 2H, ArH), 7.23-7.26 (d, 1H, J
2
=
8.3 Hz, ArH), 7.38 (d, 1H, J = 7.9 Hz, ArH), 7.52-7.59 (d, 1H, J = 8.1 Hz, ArH), 7.67-7.69
(dd, 1H, J = 1.3 & 5.1 Hz, ArH), 8.06 (s, 1H, ArH),10.33 (brs, 1H, -NH), 11.09 (brs, 1H, -NH);
+
ESI Mass (m/z) 293 [M+H] .
N'-(thiophen-2-ylmethylene)-3-(1H-indol-3-yl)propanehydrazide (5e): White solid, Yield: 87%;
0
1
m. p.: 152-154 C; FTIR (KBr) ν (cm-1): 3409 (N-H), 1660 (C=O); H NMR (DMSO-d , 300
6
MHz, ppm) : δ 2.94-3.03 (q, 4H, CH ), 6.94-7.06 (m, 4H, CH ), 7.18-7.23 (dd, 1H, J = 2.6 &
2
2
1
2.0 Hz, ArH), 7.28-7.37 (m, 2H, CH ), 7.52-7.59 (dd, 1H, J = 7.5 & 14.3 Hz, ArH), 8.09 (s, 1H,
2
+
ArH), 10.32 (brs, 1H, -NH), 11.07 (brs, 1H, -NH); MS (ESI) m/z: 298 [M+H] .
N'-(thiophen-2-ylmethylene)-4-(1H-indol-3-yl)butanehydrazide (5f): White solid, Yield: 84%;
0
1
m. p.: 164-166 C; FTIR (KBr) ν (cm-1): 3390 (N-H), 1659 (C=O); H NMR (DMSO-d , 300
6
MHz, ppm) : δ 1.98-2.08 (q, 2H, CH ), 2.67-2.72 (t, 2H, J = 7.3 Hz, CH ), 2.78-2.83 (q, 2H, J =
2
2
7
2
.3 Hz, CH ), 6.91-7.04 (m, 4H, ArH), 7.14-7.24 (dd, 1H, J = 3.2 &17.1Hz, ArH), 7.28-7.34 (m,
2
H, ArH), 7.48-7.52 (t, 1H, J = 7.5 Hz, ArH), 8.05 (s, 1H, ArH), 10.20 (brs, 1H, -NH), 10.98
+
(
brs, 1H, -NH); MS (ESI) m/z: 334 [M+H] ; HRMS: m/z Calculated value C H O N =
1
8
14
3
4
3
34.1060, Observed value = 334.0973.
N'-(4-nitrobenzylidene)-3-(1H-indol-3-yl)propanehydrazide (5g): Yellow solid, Yield: 82%; m.
0
1
p.: 189-192 C; FTIR (KBr) ν (cm-1): 3390 (N-H), 1665 (C=O); H NMR (DMSO-d , 300 MHz,
6
ppm) : δ 3.05-3.13 (q, 4H, CH ), 6.95-7.07 (m, 3H, CH ), 7.29-7.31 (d, 1H, J = 7.7 Hz, ArH),
2
2
9

ACCEPTED MANUSCRIPT
7
8
.54-7.56 (d, 1H, J = 7.3 Hz, ArH), 7.73-7.76 (d, 2H, J = 8.8 Hz, ArH), 7.96 (s, 1H, ArH), 8.15-
.18 (d, 2H, J = 8.6 Hz, ArH), 10.20 (brs, 1H, -NH), 11.39 (brs, 1H, -NH); MS (ESI) m/z: 337
+
[
M+H] .
′
N -(4-Fluorobenzylidene)-4-(1H-indol-3-yl)butanehydrazide (5h): White solid, Yield: 85%; m.
0
1
p.: 147-150 C; FTIR (KBr) ν (cm-1): 3263 (N-H), 1658 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
00 MHz, ppm) : δ 1.95 -2.06 (m, 2H, CH ), 2.26 (t, 1H, J = 7.4 Hz, CH ), 2.71 (t, 1H, J = 7.4
2 2
Hz, CH ), 2.81 (t, 2H, J = 7.0 Hz, CH ), 6.91-7.11 (m, 5H, ArH), 7.32 (d, 1H, J = 7.9 Hz, ArH),
2
2
7
.49 -7.54 (m, 2H, Ar-H), 7.67-7.75 (m, 1H, ArH), 7.87 (s, 1H, ArH), 10.31 (s, 1H, -NH), 10.98
+
+
(
s, 1H, -NH); MS (ESI) m/z: 324 [M+H] , 346 [M+Na] .
′
N -(4-Chlorobenzylidene)-3-(1H-indol-3-yl)propanehydrazide (5i): White solid, Yield: 87%; m.
0
1
p.: 190-192 C; FTIR (KBr) ν (cm-1): 3382 (N-H), 1660 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
7
00 MHz,) : δ 2.54-2.62 (m, 1H, CH ), 3.02-3.13 (m, 3H, CH ), 6.94-7.07- (m, 3H, ArH), 7.29-
2 2
.33 (m, 3H, 3 ArH), 7.50-7.59 (m, 2H, ArH), 7.62-7.69 (m, 1H, ArH), 7.87 (s, 1H, ArH), 10.18
+
+
(
s, 1H, -NH), 11.09 (s, 1H, -NH); MS (ESI) m/z: 326 [M+H] , 348 [M+Na] .
′
N -(4-Chlorobenzylidene)-4-(1H-indol-3-yl)butanehydrazide (5j): White solid, Yield: 87%; m.
0
1
p.: 155-160 C; FTIR (KBr) ν (cm-1): 3416 (N-H), 1658 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
00 MHz, ppm) : δ 1.96-2.08 (m, 2H, CH ), 2.26 (t, 1H, J = 7.2 Hz, CH ), 2.71 (t, 1H, J = 7.4
2 2
Hz, CH ), 2.82 (t, 2H, J = 7.2 Hz, CH ), 6.91-7.06 (m, 3H, ArH), 7.29-7.34 (m, 3H, ArH), 7.46-
2
2
7
.52 (m, 2H, ArH), 7.66 (d, 1H, J = 8.3 Hz, ArH), 7.85 (s, 1H, ArH), 10.31 (s, 1H, -NH), 11.06
+
+
(
s, 1H, -NH); MS (ESI) m/z: 340 [M+H] , 362 [M+Na] .
′
N -(3-Chlorobenzylidene)-3-(1H-indol-3-yl)propanehydrazide (5k): White solid, Yield: 86%; m.
0
1
p.: 170-173 C; FTIR (KBr) ν (cm-1): 3449 (N-H), 1667 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
7
00 MHz, ppm) : δ 2.53-2.62 (m, 1H, CH ), 3.03-3.13 (m, 3H, CH ), 6.95-7.06 (m, 3H, ArH),
2 2
.25-7.35 (m, 3H, ArH), 7.45-7.63 (m, 3H, ArH), 7.88 (s, 1H, ArH), 10.29 (s, 1H, ArH), 11.17
+
+
(
s, 1H, -NH); MS (ESI) m/z: 326 [M+H] , 348 [M+Na] .
′
N -(3-Chlorobenzylidene)-4-(1H-indol-3-yl)butanehydrazide (5l): White solid, Yield: 86%; m.
0
1
p.: 128-132 C; FTIR (KBr) ν (cm-1): 3312 (N-H), 1654 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
00 MHz, ppm) : δ 1.99-2.16 (m, 2H, CH ), 2.27 (t, 1H, J = 6.4 Hz, CH ), 2.69-2.87 (m, 3H,
2 2
CH ), 6.94-7.07 (m, 3H, ArH), 7.23-7.31 (m, 3H, ArH), 7.36-7.41 (m, 1H, ArH), 7.50-7.59 (m,
2
1
0

ACCEPTED MANUSCRIPT
+
2
3
H, ArH), 7.82 (s, 1H, CH), 9.81 (s, 1H, -NH), 10.99 (s, 1H, -NH); MS (ESI) m/z: 340 [M+H] ,
+
62 [M+Na] .
N'-(3-bromobenzylidene)-3-(1H-indol-3-yl)propanehydrazide(5m): White solid, Yield: 89%; m.
0
1
p.: 165-167 C; FTIR (KBr) ν (cm-1): 3438 (N-H), 1664 (C=O); H NMR (DMSO-d , 500 MHz,
6
ppm) : δ 2.99- 3.02 (q, 4H, 2CH ), 6.93-7.03 (m, 3H, ArH), 7.22-7.29 (q, 2H, CH ), 7.41-7.45 (d,
2
2
1
7
3
3
H, J = 8.9 Hz, ArH), 7.51-7.54 (t, 1H, J = 7.5 Hz, ArH), 7.58-7.60 (d, 1H, J = 8.2 Hz, ArH),
.74 (s, 1H, ArH), 7.86 (s, 1H, ArH), 10.35 (brs, 1H, -NH), 11.17 (brs, 1H, -NH); MS (ESI) m/z:
+
70 [M+H] ; HRMS: m/z Calculated value C H ON Br = 370.0549, Observed value =
18
17
3
70.0548.
N'-(2,6-dichlorobenzylidene)-3-(1H-indol-3-yl)propanehydrazide(5n): White solid, Yield: 89%;
0
1
m. p.: 172-174 C; FTIR (KBr) ν (cm-1): 3436 (N-H), 1590 (C=O); H NMR (DMSO-d , 300
6
MHz, ppm) : δ 2.5-2.55 (t, 2H, J = 1.7 Hz, CH ), 2.99-3.01 (t, 2H, J = 2.0 Hz, CH ), 6.89-7.04
2
2
(m, 3H, ArH), 7.24-7.29 (t, 2H, J = 8.3 Hz, ArH), 7.35-7.38 (d, 2H, J = 7.3 Hz, ArH), 7.50-7.52
(d, 1H, J = 7.3 Hz, ArH), 8.18 (s, 1H, ArH), 10.29 (brs, 1H, -NH), 11.31 (brs, 1H, -NH); MS
+
(
ESI) m/z: 360 [M+H] ; HRMS: m/z Calculated value C H ON Cl = 360.0664, Observed
1
8
16
3
2
value = 360.0665.
N'-(3,4-dichlorobenzylidene)-4-(1H-indol-3-yl)butanehydrazide (5o): White solid, Yield: 88%;
0
1
m. p.: 166-168 C; FTIR (KBr) ν (cm-1): 3321 (N-H), 1658 (C=O); H NMR (DMSO-d , 300
6
MHz, ppm) : δ 1.97- 2.11 (m, 2H, CH ), 2.69-2.75 (t, 2H, J = 7.5 Hz, CH ), 2.76-2.83 (q, 2H, J =
2
2
7
.1 Hz, CH ), 6.91-7.04 (m, 3H, ArH), 7.29-7.31 (d, 1H, J = 7.9 Hz, ArH), 7.39-7.59 (m, 3H,
2
ArH), 7.67 (s, 1H, ArH), 7.82-7.84 (d, 1H, J = 6.4 Hz, ArH), 10.40 (brs, 1H, -NH), 11.21 (brs,
+
1
3
H, -NH); MS (ESI) m/z: 374 [M+H] ; HRMS: m/z Calculated value C H ON Cl Na =
19
17
3
2
96.0640, Observed value = 396.0634.
′
N -(4-methylbenzylidene)-3-(1H-Indol-3-yl)propanehydrazide (5p): White solid, Yield: 92%; m.
0
1
p.: 147-150 C; FTIR (KBr) ν (cm-1): 3435 (N-H), 1656 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
7
00 MHz, ppm) : δ 2.36 (s, 3H, CH ), 2.53-2.61 (m, 1H, CH ), 2.97-3.11 (m, 3H, CH ), 6.94-
3 2 2
.06- (m, 3H, ArH), 7.15 (t, 2H, J = 4.9 Hz, ArH), 7.29 (d, 1H, J = 7.7 Hz, ArH), 7.47 (d, 1H, J
7.9 Hz, ArH), 7.57 (d, 2H, J = 7.0 Hz, ArH), 7.88 (s, 1H, ArH), 10.33 (s, 1H, -NH), 10.99 (s,
=
+
+
1
H, -NH),; MS (ESI) m/z: 306 [M+H] , 328 [M+Na] .
1
1

ACCEPTED MANUSCRIPT
′
N -(4-methoxybenzylidene)-3-(1H-Indol-3-yl)propanehydrazide (5q): White solid, Yield: 90%;
0
1
m. p.: 162-164 C; FTIR (KBr) ν (cm-1): 3432 (N-H), 1656 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
2
00 MHz, ppm) : δ 2.54-2.62 (m, 1H, CH ), 2.96-3.13 (m, 3H, CH ), 3.81 (s, 3H, CH ), 6.83 (d,
2 2 3
H, J = 8.3 Hz, ArH), 6.94-7.06 (m, 3H, ArH), 7.29 (d, 1H, J = 7.9 Hz, ArH), 7.51-7.64 (m, 3H,
+
ArH), 7.85 (s, 1H, ArH), 10.21 (s, 1H, ArH), 10.88 (s, 1H, -NH); MS (ESI) m/z: 322 [M+H] ,
+
3
44 [M+Na] .
′
N -(4-methoxybenzylidene)-4-(1H-indol-3-yl)butanehydrazide (5r): White solid, Yield: 83%; m.
0
1
p.: 156-158 C; FTIR (KBr) ν (cm-1): 3278 (N-H), 1651 (C=O); H NMR (CDCl +DMSO-d ,
3
6
3
00 MHz, ppm) : δ 1.97-2.10 (m, 2H, CH ), 2.24 (t, 1H, J = 7.4 Hz, CH ), 2.71 (t, 1H, J = 7.5
2 2
Hz, CH ), 2.82 (t, 2H, J = 7.4 Hz, CH ), 3.82 (s, 3H, CH ), 6.80-7.05 (m, 5H, ArH), 7.29 (d, 1H,
2
2
3
J = 8.1 Hz, ArH), 7.42-7.54 (m, 2H, ArH), 7.62 (d, 1H, J = 8.5 Hz, ArH), 7.82 (s, 1H, ArH),
+
+
1
0.29 (s, 1H, -NH), 10.85 (s, 1H, -NH); MS (ESI) m/z: 336 [M+H] , 358 [M+Na] .
N'-(2,4,6-trimethoxybenzylidene)-4-(1H-indol-3-yl)butanehydrazide (5s): Yellow solid, Yield :
0
1
8
2%; m.p. 189-191 C; FTIR (KBr) ν (cm-1): 3304 (N-H), 1651 (C=O); H NMR (CDCl 300
3,
MHz, ppm): δ 2.27-2.34 (q, 2H, CH ), 2.94-2.98 (t, 2H, J = 7.2 Hz, CH ), 3.02-3.06 (t, 2H, J =
2
2
7
1
.3 Hz, CH ), 3.77-3.81(s, 9H, 3CH ), 6.11 (s, 2H, ArH), 6.89-7.04 (s, 3H, ArH), 7.27-7.30 (d,
2 3
H, J = 7.9 Hz, ArH), 7.54-7.56 (d, 1H, J = 7.7 Hz, ArH), 8.08 (s, 1H, ArH), 10.29 (brs, 1H, -
+
NH) 10.56 (brs, 1H, -NH); ESI Mass (m/z) 396 [M+H] ; HRMS: m/z Calculated value
C H N O = 396.1676, Observed value = 396.1653.
22
24
3
4
N'-(4-(3,5,6-trichloropyridin-2-yloxy)benzylidene)-3-(1H-indol-3-yl)propanehydrazide
(5u):
0
1
White solid, Yield: 91%; m. p.: 169-172 C; FTIR (KBr) ν (cm-1): 3405 (N-H), 1673 (C=O); H
NMR (DMSO-d , 300 MHz, ppm) : δ 3.03-3.13 (q, 4H, 2CH ), 6.94-7.06 (m, 3H, ArH), 7.11-
6
2
7
.16 (t, 2H, J = 6.6 & 8.4 Hz, ArH), 7.28-7.31 (d, 1H, J = 7.9 Hz, ArH), 7.55-7.58 (d, 1H, J = 7.5
Hz, ArH), 7.65-7.68 (d, 1H, J = 8.6 Hz, ArH),7.73-7.78 (t, 1H, J = 8.8 Hz, ArH), 7.94 (s, 1H,
ArH), 7.99 (s, 1H, ArH), 10.23 (brs, 1H, -NH), 11.06 (brs, 1H, -NH); MS (ESI) m/z: 489
+
[
M+H] .
N'-(4-(3,5,6-trichloropyridin-2-yloxy)benzylidene)-4-(1H-indol-3-yl)butanehydrazide
(5v):
0
1
White solid, Yield: 93%; m. p.: 167-168 C; FTIR (KBr) ν (cm-1): 3400 (N-H), 1658 (C=O); H
NMR (DMSO-d , 300 MHz, ppm) : δ 1.99-2.09 (q, 2H, CH ), 2.70-2.75 (t, 2H, J = 7.5 Hz, CH ),
6
2
2
1
2

ACCEPTED MANUSCRIPT
2
7
.78-2.84 (q, 2H, J = 6.9 Hz, CH ), 6.91-7.04 (m, 3H, ArH), 7.11-7.17 (t, 2H, J = 7.9 Hz, ArH),
2
.29-7.32 (d, 1H, J = 7.9 Hz, ArH), 7.50-7.52 (d, 1H, J = 7.7 Hz, ArH), 7.59-7.61 (d, 1H, J = 8.4
Hz, ArH), 7.76-7.86 (dd, 1H, J = 8.4 Hz, ArH), 7.92 (s, 1H, ArH), 8.04-8.05 (d, 1H, J = 5.4 Hz,
+
+
ArH), 10.35 (brs, 1H, -NH), 11.03 (brs, 1H, -NH); MS (ESI) m/z: 501 [M+H] , 523 [M+Na] ;
HRMS: m/z Calculated value C H O N Cl = 501.0646, Observed value = 501.0639.
2
4
20
2
4
3
5
.5 General procedure for the synthesis of 5-(alkyl(1H-indol-3-yl))-2-(substituted)-1,3,4-
oxadiazoles (6a-6v):
To the solution of N'-benzylidene-(1H-indol-3-yl)alkane hydrazides (5a-y) (1 mmol) in
DCM was added PhI(OAc) (1.2 mmol) and the mixture was allowed to stir at room temperature.
2
Progress of the reaction was monitored by TLC using ethyl acetate/hexane (4:6) as eluting
medium. At the end of the reaction, reaction mixture was diluted with water (5 mL) and
extracted with DCM (3x5mL). The combined organic layers were dried over sodium sulphate,
filtered, concentrated under vacuum and purified by silica gel column chromatography using
ethyl acetate:hexane as eluent to afford pure compounds. All the synthesized compounds are
1
characterized by H-NMR and mass spectroscopic techniques.
5
.6 5-(3-(1H-indol-3-yl)propyl)-2-phenyl-1,3,4-oxadiazole (6a): White solid, Yield : 78%; R =
f
0
1
0
.31; m.p. 122-124 C; FTIR (KBr) ν (cm-1): 3226 (N-H), 1022 (C-O); H NMR (CDCl 300
3,
MHz, ppm): δ 2.19-2.26 (m, 2H, CH ), 2.84-2.92 (m, 4H, 2CH ), 6.93 (s, 1H, ArH), 6.98-7.01 (t,
2
2
1
7
H, J = 7.3 Hz, ArH), 7.04-7.08 (t, 1H, J = 7.3 Hz, ArH), 7.19-7.22 (t, 1H, J = 8.0 Hz, ArH),
.41 (m, 3H, ArH), 7.48-7.50 (d, 1H, J = 7.3 Hz, ArH), 7.89-7.91 (d, 2H, J = 7.3 Hz, ArH), 7.95
1
3
(
brs, 1H, NH); C NMR (CDCl +DMSO-d , 75 MHz, ppm): δ 21.5, 23.3, 25.5, 110.7, 111.8,
3 6
1
17.2, 117.9, 120.5, 121.4, 124.2, 126.0, 127.2, 128.5, 129.1, 135.6, 159.8, 165.1; ESI Mass
+
(
m/z) 304 [M+H] ; HRMS: m/z Calculated value C H N ONa = 326.1269, Observed value =
1
9
17
3
3
26.1271.
5
.7 5-(3-(1H-indol-3-yl)propyl)-2-(naphthalen-1-yl)-1,3,4-oxadiazole (6b): White solid, Yield :
0
1
6
9%; R = 0.37; m.p. 143-146 C; FTIR (KBr) ν (cm-1): 3230 (N-H), 1128 (C-O); H NMR
f
(
DMSO-d 300 MHz, ppm): δ 2.29-2.34 (t, 2H, J = 7.3 Hz, CH ), 2.94-2.99 (t, 2H, J =7.1 Hz,
6
,
2
CH ), 3.02-3.07 (t, 2H, J = 7.5 Hz, CH ), 7.03-7.17 (m, 3H, ArH), 7.35-7.38 (d, 1H, J = 7.9 Hz,
2
2
ArH), 7.54-7.68 (m, 4H, ArH), 7.92-7.95 (d, 1H, J = 7.9 Hz, ArH), 8.02-8.08 (dd, 2H, J = 7.3 &
1
3

ACCEPTED MANUSCRIPT
1
3
1
0.3 Hz, ArH), 9.16-9.19 (d, 1H, J = 8.4 Hz, ArH), 9.82 (brs, 1H, NH); C NMR
(
CDCl +DMSO-d , 75MHz, ppm): δ 23.1, 23.6, 25.7, 110.2, 112.3, 117.1, 117.3, 119.1, 119.9,
3
6
1
21.1, 123.8, 124.7, 125.4, 125.9, 126.7, 126.9, 127.4, 128.5, 131.0, 132.4, 135.4, 163.0, 165.2;
+
ESI Mass (m/z) 376 [M+Na] ; HRMS: m/z Calculated value C H ON Na = 376.1420,
2
3
19
3
Observed value = 376.1418.
5
.8 5-(3-(1H-indol-3-yl)ethyl)-2-(pyridin-2-yl)-1,3,4-oxadiazole (6c): White solid, Yield : 70%;
0
1
R = 0.33; m.p. 190-193 C; FTIR (KBr) ν (cm-1): 3210 (N-H), 1097 (C-O); H NMR (CDCl
f
3,
3
00 MHz, ppm): δ 2.83 (s, 4H, 2CH ), 6.50-6.63 (m, 3H, ArH), 6.84-6.87 (d, 1H, J = 7.9 Hz,
2
ArH), 6.96-7.01 (t, 1H, J = 7.5 Hz, ArH), 7.04-7.06 (d, 1H, J = 6.6 Hz, ArH), 7.38-7.43 (t, 1H, J
7.7 Hz, ArH), 7.64-7.67 (d, 1H, J = 7.7 Hz, ArH), 8.25-8.26 (d, 1H, J = 4.5 Hz, ArH), 9.60
=
1
3
(
brs, 1H, NH); C NMR (CDCl , 125MHz, ppm): δ 22.4, 26.5, 111.1, 114.0, 118.5, 119.5,
3
1
21.7, 122.2, 123.0, 125.7, 127.0, 136.2, 137.23, 143.6, 150.1, 163.9, 167.7; ESI Mass (m/z) 313
+
[
M+Na] ; HRMS: m/z Calculated value C H N ONa = 313.1059, Observed value =
1
7
14
4
3
13.10618.
5
.9 5-(3-(1H-indol-3-yl)ethyl)-2-(pyridin-3-yl)-1,3,4-oxadiazole (6d): White solid, Yield : 72%;
0
1
R = 0.33; m.p. 140-142 C; FTIR (KBr) ν (cm-1): 3183 (N-H), 1016 (C-O); H NMR (CDCl
f
3,
3
7
00 MHz, ppm): δ 3.36 (s, 4H, 2CH ), 7.08-7.23 (m, 3H, ArH), 7.36-7.46 (m, 2H, ArH), 7.60-
2
.62 (d, 1H, J = 8.3 Hz, ArH), 8.07 (brs, 1H, NH), 8.26-8.29 (d, 1H, J = 8.3 Hz, ArH), 8.74-8.76
13
(
dd, 1H, J = 1.5 & 5.2 Hz, ArH), 9.18 (d, 1H, J = 1.5 Hz, ArH); C NMR (CDCl +DMSO-d ,
3 6
1
1
25MHz, ppm): δ 21.2, 25.3, 110.5, 116.8, 117.6, 120.2, 121.2, 121.7, 122.8, 124.8, 125.8,
+
32.8, 135.4, 136.3, 146.2, 149.0, 151.0; ESI Mass (m/z) 291 [M+H] ; HRMS: m/z Calculated
value C H N O = 291.1002, Observed value = 291.1235.
1
7
14
4
5
.10 5-(3-(1H-indol-3-yl)ethyl)-2-(thiophen-2-yl)-1,3,4-oxadiazole (6e): White solid, Yield :
0
1
7
5%; R = 0.31; m.p. 132-134 C; FTIR (KBr) ν (cm-1): 3179 (N-H), 1009 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 3.29-3.32 (m, 4H, 2CH ), 7.03-7.04 (d, 1H, J = 2.6 Hz, ArH), 7.07-
3
,
2
7
7
.17 (m, 3H, ArH), 7.28-7.31(d, 1H, J = 7.7 Hz, ArH), 7.48-7.49 (d, 1H, J = 4.9 Hz, ArH), 7.55-
13
.57 (d, 1H, J = 7.7 Hz, ArH), 7.64-7.65 (d, 1H, J = 3.7 HZ, ArH), 7.94 (brs, 1H, NH); C NMR
(
CDCl , 75MHz, ppm): δ 22.3, 26.3, 111.2 113.9, 118.4, 119.5, 121.7, 122.2,126.9, 128.0, 129.5,
3
+
1
29.8 136.2; 139.1, 157.5, 167.5; ESI Mass (m/z) 296 [M+H] ; HRMS: m/z Calculated value
C H N ONaS = 318.0677, Observed value = 318.0674.
16
13
3
1
4

ACCEPTED MANUSCRIPT
5
.11 5-(3-(1H-indol-3-yl)propyl)-2-(thiophen-2-yl)-1,3,4-oxadiazole (6f): White solid, Yield :
0
1
7
7%; R = 0.31; m.p. 114-116 C; FTIR (KBr) ν (cm-1): 3181 (N-H), 1015 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 2.21-2.31 (m, 2H, 2CH ), 2.89-2.95 (m, 4H, 2CH ), 6.98-6.99 (d,
3, 2 2
1
1
H, J = 2.2 Hz, ArH), 7.02-7.14 (m, 3H, ArH), 7.26-7.29 (d, 1H, J = 8.3 Hz, ArH), 7.48-7.49 (d,
H, J = 5.2 Hz, ArH), 7.53-7.56 (d, 1H, J = 7.5 Hz, ArH), 7.62-7.63 (dd, 1H, J = 1.5 & 3.7 Hz,
1
3
ArH), 8.00 (brs, 1H, NH); C NMR (CDCl , 75MHz, ppm): δ 24.3, 24.9, 26.8 111.1, 114.8,
3
1
18.7, 119.2, 121.7, 121.9, 124.0, 126.7, 127.2, 128.9, 131.4, 136.4, 164.6, 166.8; ESI Mass
+
(
m/z) 332 [M+Na] ; HRMS: m/z Calculated value C H N ONaS = 332.0833, Observed value
1
7
15
3
=
332.0831.
5
.12 5-(3-(1H-indol-3-yl)ethyl)-2-(4-nitrophenyl)-1,3,4-oxadiazole (6g): White solid, Yield :
0
1
6
5%; R = 0.34; m.p. 160-163 C; FTIR (KBr) ν (cm-1): 3233(N-H), 1098 (C-O); H NMR
f
(
DMSO-d 300 MHz, ppm): δ 3.31 (s, 4H, 2CH ), 6.92-7.06 (m, 3H, ArH), 7.31-7.33 (d, 1H, J =
6
,
2
7
.9 Hz, ArH), 7.45-7.48 (d, 1H, J = 7.7 Hz, ArH), 8.15-8.18 (d, 2H, J = 8.4 Hz, ArH), 8.34-8.39
1
3
(
d, 2H, J = 8.8 Hz, ArH), 10.52 (brs, 1H, ArH). C NMR (CDCl +DMSO-d , 75MHz, ppm): δ
3 6
2
1
3
1.2, 25.4, 110.5, 111.3, 116.8, 117.6, 120.2, 121.3, 123.1, 125.7, 126.5 128.3, 135.4, 148.1,
+
61.7, 166.5; ESI Mass (m/z) 335 [M+H] ; HRMS: m/z Calculated value C H N O Na =
18
14
4
3
57.0963, Observed value = 357.0957.
5
.14 5-(3-(1H-Indol-3-yl)propyl)-2-(4-fluorophenyl)-1,3,4-oxadiazole (6h): White solid, Yield :
0
1
6
7%; R = 0.31; m. p. 153-157 C; FTIR (KBr) ν (cm-1): 3216 (N-H), 1089 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 2.21-2.33 (m, 2H, CH ), 2.90-2.99 (m, 4H,2 CH ), 6.99 (s, 1H, ArH),
3, 2 2
7
3
1
.01-7.18 (m, 4H, ArH), 7.23-7.28 (m, 1H, ArH), 7.53 (d, 1H, J = 7.5 Hz, ArH), 7.88-7.99 (m,
1
3
H, ArH); C NMR (CDCl + DMSO-d 75 MHz, ppm): δ 23.7, 24.2, 26.2, 110.8, 113.2,
3
6,
15.5,115.8, 117.8, 118.0, 120.7, 121.6, 126.6,128.4, 128.4, 135.9, 162.2, 163.1, 165.5, 166.3;
+
ESI Mass (m/z) 344 [M+Na] ; HRMS: m/z Calculated value C H N OFNa = 344.1175,
1
9
16
3
Observed value = 344.1180.
5
.15 5-(2-(1H-Indol-3-yl)ethyl)-2-(4-chlorophenyl)-1,3,4-oxadiazole (6i): White solid, Yield :
0
1
7
0%; R = 0.34; m. p. 160-161 C; FTIR (KBr) ν (cm-1): 3232 (N-H), 1093 (C-O); H NMR
f
(
DMSO-d 300 MHz, ppm): δ 3.29 (s, 4H, 2CH ), 6.94-7.08 (m, 3H, ArH), 7.31 (d, 1H, J = 7.9
6
,
2
Hz, ArH), 7.5 (dd, 3H, J = 2.3, & 1.89 Hz, ArH), 7.93 (d, 2H, J = 8.5 Hz, ArH), 10.42 (s, 1H,
1
3
NH); C NMR (CDCl +DMSO-d 50 MHz, ppm): δ 21.7, 25.8, 110.8, 112.0, 117.3, 118.1,
3
6,
1
5

ACCEPTED MANUSCRIPT
1
20.7, 121.5, 121.7, 126.2, 127.2, 128.6, 135.8, 136.7, 163.0, 166.1; ESI Mass (m/z) 324
+
[
M+H] ; HRMS: m/z Calculated value = C H N ONaCl = 346.0723, Observed value =
1
8
14
3
3
46.0726.
5
.16 5-(3-(1H-Indol-3-yl)propyl)-2-(4-chlorophenyl)-1,3,4-oxadiazole (6j): White solid, Yield :
0
1
7
1%; R = 0.34; m. p. 149-150 C; FTIR (KBr) ν (cm-1): 3217 (N-H), 1095 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 2.21-2.33 (m, 2H, CH ), 2.88-2.98 (m, 4H, 2CH ), 6.98 (s, 1H, ArH),
3, 2 2
7
7
2
1
3
.01-7.16 (m, 2H, ArH), 7.25-7.28 (m, 1H, ArH), 7.43 (d, 2H, J = 8.3 Hz, ArH), 7.53 (d, 1H, J =
1
3
.5 Hz, ArH), 7.87-7.92 (m, 3H, 1 ArH); C NMR (CDCl +DMSO-d 75 MHz, ppm): δ 22.7,
3
6,
3.1, 25.2, 109.9, 111.6, 116.6, 116.7, 119.4, 120.7, 120.9 125.5, 126.4, 127.7, 135.8, 135.5,
+
61.6, 165.1; ESI Mass (m/z) 338 [M+H] ; HRMS: m/z Calculated value C H N ONaCl =
1
9
16
3
60.0879, Observed value = 360.0893.
5
.17 5-(2-(1H-Indol-3-yl)ethyl)-2-(3-chlorophenyl)-1,3,4-oxadiazole (6k): White solid, Yield :
0
1
6
3%; R = 0.37; m. p. 117-118 C; FTIR (KBr) ν (cm-1): 3287 (N-H), 1077 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 3.32 (s, 4H, 2CH ), 7.02-7.17 (m, 3H, ArH), 7.29 (d, 1H, J = 8.3 Hz,
3
,
2
ArH), 7.37-7.48 (m, 2H, ArH), 7.53 (d, 1H, J = 7.5 Hz, ArH), 7.85 (d, 1H, J = 6.8 Hz, ArH),
1
3
7
1
1
3
.92 (s, 1H, ArH), 7.98 (s, 1H, -NH); C NMR (CDCl +DMSO, 75 MHz, ppm): δ 21.4, 25.5,
3
10.5, 111.6, 117.0, 117.7, 120.4, 121.3, 123.8, 124.5, 125.4, 125.9, 129.5, 130.4, 133.8, 135.5,
+
62.3, 165.9; ESI Mass (m/z) 324 [M+H] ; HRMS: m/z Calculated value C H N ONaCl =
1
8
14
3
46.0723, Observed value = 346.0731.
5
.18 5-(3-(1H-Indol-3-yl)propyl)-2-(3-chlorophenyl)-1,3,4-oxadiazole (6l): White solid, Yield :
0
1
6
5%; R = 0.37; m. p. 116-117 C; FTIR (KBr) ν (cm-1): 3221 (N-H), 1079 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 2.24-2.33 (m, 2H, CH ), 2.90-2.98 (m, 4H, 2CH ), 6.97 (s, 1H, ArH),
3, 2 2
7
.037-14 (m, 2H, ArH), 7.27 (s, 1H, ArH), 7.37-7.47 (m, 2H, ArH), 7.53 (d, 1H, J = 7.5 Hz,
1
3
ArH), 7.84 (d, 1H, J = 7.5 Hz, ArH), 7.91 (s, 1H, ArH), 7.96 (s, 1H, -NH); C NMR
(
CDCl +DMSO-d 75 MHz, ppm): δ 24.1, 24.6, 26.5, 111.1, 113.9, 118.2, 118.6, 121.4, 121.8,
3 6,
1
24.5, 125.2, 126.3, 126.9, 130.1, 131.2, 134.7, 136.2, 163.2, 167.0; ESI Mass (m/z) 338
+
[
M+H] ; HRMS: m/z Calculated value C H N ONaCl = 360.0879, Observed value =
1
9
16
3
3
60.0892.
1
6

ACCEPTED MANUSCRIPT
5
.19 5-(3-(1H-indol-3-yl)ethyl)-2-(3-bromophenyl)-1,3,4-oxadiazole (6m): White solid, Yield :
0
1
6
6%; R = 0.34; m.p. 112-114 C; FTIR (KBr) ν (cm-1) : 3167 (N-H), 1117 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 3.30 (s, 4H, 2CH ), 6.95-7.09 (m, 3H, ArH), 7.32-7.43 (m, 2H, ArH),
3
,
2
7
.47-7.50 (d, 1H, J = 7.7 Hz, ArH), 7.62-7.65 (d, 1H, J = 7.1 Hz, ArH), 7.89-7.92 (d, 1H, J = 7.7
+
Hz, ArH), 8.06 (s, 1H, ArH), 10.23 (brs, 1H, NH); ESI Mass (m/z) 368 [M] ; HRMS: m/z
Calculated value C H N ONaBr = 390.0217, Observed value = 390.0234.
1
8
14
3
5
.20 5-(3-(1H-indol-3-yl)ethyl)-2-(2,6-dichlorophenyl)-1,3,4-oxadiazole (6n): White solid, Yield
0
1
:
68%; R = 0.34; m.p. 154-156 C; FTIR (KBr) ν (cm-1): 3263 (N-H), 1024 (C-O); H NMR
f
(
DMSO-d , 300 MHz, ppm): δ 3.31 (s, 4H, 2CH ), 6.98-7.09 (m, 3H, ArH), 7.30-7.33 (d, 1H, J =
6
2
1
3
8
7
1
.1 Hz, ArH), 7.47-7.56 (m, 4H, ArH), 10.14 (brs, 1H, NH); C NMR (CDCl +DMSO-d ,
3 6
5MHz, ppm): δ 21.8, 25.8, 110.8, 111.9, 117.4, 118.1, 120.8, 121.6, 123.6, 126.2, 127.6, 132.3,
+
35.5, 135.8, 159.0, 167.1; ESI Mass (m/z) 358 [M] ; HRMS: m/z Calculated value
C H N ONaCl = 380.0333, Observed value = 380.0336.
18
13
3
2
5
.21 5-(3-(1H-indol-3-yl)propyl)-2-(3,4-dichlorophenyl)-1,3,4-oxadiazole (6o): White solid,
0
1
Yield : 69%; R = 0.34; m.p. 134-136 C; FTIR (KBr) ν (cm-1): 3249 (N-H), 1035 (C-O); H
f
NMR (DMSO-d , 300 MHz, ppm): δ 2.22-2.32 (m, 2H, CH ), 2.89-2.94 (t, 2H, J = 7.3Hz, CH ),
6
2,
2
2
7
.96-3.01 (t, 2H, J = 7.3Hz, CH ), 7.03-7.14 (m, 3H, ArH), 7.34-7.36 (d, 1H, J = 7.9Hz, ArH),
2
.52-7.61 (m, 2H, ArH), 7.80-7.84 (dd, 1H, J = 1.8 & 8.3Hz, ArH), 8.05-8.06 (d, 1H, J = 1.8 Hz,
1
3
ArH), 9.87 (brs, 1H, NH); C NMR (CDCl +DMSO-d , 75MHz, ppm): δ 23.4, 23.9, 25.8,
3
6
1
10.5, 112.6, 117.4, 117.6, 120.3, 121.3, 124.9, 127.3, 130.3, 132.2, 134.5, 135.6, 161.7, 166.4;
+
ESI Mass (m/z) 372 [M+H] ; HRMS: m/z Calculated value C H N ONaCl = 372.06649,
1
9
15
3
2
Observed value = 372.06700.
5
.22 5-(2-(1H-Indol-3-yl)ethyl)-2-p-tolyl-1,3,4-oxadiazole (6p): White solid, Yield : 55%; R =
f
0
1
0
.34; m. p. 163-165 C; FTIR (KBr) ν (cm-1): 3215 (N-H), 1090 (C-O); H NMR (CDCl 300
3,
MHz, ppm): δ 2.42 (s, 3H, CH ), 3.31 (t, 4H, J = 3.4 Hz, 2CH ), 7.18-7.02 (m, 3H, ArH), 7.31-
3
2
7
.24 (m, 3H, ArH), 7.57 (d, 1H, J = 7.7 Hz, ArH), 7.84 (d, 2H, J = 8.1 Hz, ArH), 7.98 (s, 1H, -
1
3
NH); C NMR (CDCl +DMSO-d 75 MHz, ppm): δ 21.0, 21.8, 25.9, 111.0, 112.4, 117.5,
3
6,
1
18.3, 120.5, 120.9, 121.6, 126.0, 126.3, 129.1, 135.9, 141.4, 164.1, 165.8; ESI Mass (m/z) 304
+
[
M+H] ; HRMS: m/z Calculated value C H N O = 304.1449, Observed value = 304.1461.
1
9
18
3
1
7

ACCEPTED MANUSCRIPT
5
.24 5-(2-(1H-Indol-3-yl)ethyl)-2-(4-methoxyphenyl)-1,3,4-oxadiazole (6q): White solid, Yield :
0
1
6
4%; R = 0.31; m. p. 154-157 C; FTIR (KBr) ν (cm-1): 3181 (N-H), 1025 (C-O); H NMR
f
(
CDCl +DMSO-d 300 MHz, ppm): δ 3.09-3.27 (m, 4H, 2CH ), 3.87 (s, 3H, CH ), 6.99-7.03 (s,
3 6, 2 3
1
3
5
H, ArH), 7.31 (s, 1H, ArH), 7.50 (s, 1H, ArH), 7.868 (s, 2H, ArH), 10.53 (brs, 1H, -NH); C
NMR (CDCl +DMSO-d 75 MHz, ppm): δ 21.1, 25.1, 54.0, 110.3, 111.3, 113.1, 115.1, 116.7,
3
6,
+
1
17.3, 120.0, 121.0, 125.6, 127.0, 135.2, 160.7, 162.9, 164.6; ESI Mass (m/z) 320 [M+H] , 342
+
(
M+Na ); HRMS: m/z Calculated value C H N O Na = 342.1218, Observed value = 342.1225.
1
9
17
3
2
5
.25 5-(3-(1H-indol-3-yl)propyl)-2-(4-methoxyphenyl)-1,3,4-oxadiazole (6r): White solid, Yield
0
1
:
69%; R = 0.31; m. p. 139-142 C; FTIR (KBr) ν (cm-1): 3218 (N-H), 1024 (C-O); H NMR
f
(
CDCl 300 MHz, ppm): δ 2.22-2.33 (m, 2H, CH ), 2.88-2.96 (m, 4H, 2CH ), 3.87 (s, 3H, CH ),
3, 2 2 3
7
.18-6.91 (m, 5H, ArH), 7.28 (d, J = 8.3 Hz, 1H, ArH), 7.54 (d, J = 7.5 Hz, 1H, ArH), 7.91-7.85
1
3
(
m, 3H, ArH); C NMR (CDCl +DMSO-d 75 MHz, ppm): δ 23.9, 24.4, 26.4, 54.9, 110.9,
3 6,
1
13.4, 113.9, 115.9, 117.9, 118.1, 120.8, 121.6, 126.7, 127.8, 136.1, 161.6, 163.9, 165.8; ESI
+
+
Mass (m/z) 334 [M+H] , 356 [M+Na] ; HRMS: m/z Calculated value C H N O Na =
2
0
19
3
2
3
56.1374, Observed value = 356.1383.
5
.26 5-(3-(1H-indol-3-yl)propyl)-2-(2,4,6-trimethoxyphenyl)-1,3,4-oxadiazole (6s): Yellow solid,
1
Yield : 50%; R = 0.30; m.p. semisolid; FTIR (KBr) ν (cm-1): 3289 (N-H), 1131(C-O); H NMR
f
(CDCl 300 MHz, ppm): δ 2.18-2.24 (q, 2H, CH ), 2.84-2.87 (t, 2H, J = 7.2 Hz, CH ), 2.91-2.94
3, 2 2
(
t, 2H, J = 7.2 Hz, CH ), 3.71 (s, 6H, 2CH ), 3.81 (s, 3H, CH ), 6.51 (s, 2H, ArH), 6.95 (s, 1H,
2
3
3
ArH), 7.04-7.07 (t, 1H, J = 7.2 Hz, ArH), 7.10-7.14 (t, 1H, J = 7.2 Hz, ArH), 7.30-7.31 (t, 1H, J
=
7.2 Hz, ArH), 7.56-7.57 (d, 1H, J = 7.2 Hz, ArH), 8.88 (brs, 1H, -NH); ESI Mass (m/z) 394
+
[
M+H] ; HRMS: m/z Calculated value C H N O = 394.1766, Observed value = 394.1753.
2
2
24
3
4
5
6
5
7
7
1
1
.27 5-(3-(1H-indol-3-yl)ethyl)-2-(3-phenoxyphenyl)-1,3,4-oxadiazole (6t): White solid, Yield :
0
1
9%; R = 0.31; m.p. 75-78 C; FTIR (KBr) ν (cm-1): 3221 (N-H), 1231 (C-O); H NMR (CDCl
f
3,
00 MHz, ppm): δ 3.31 (s, 4H, 2CH ), 7.03-7.04 (m, 3H, ArH), 7.10-7.20 (m, 4H, ArH), 7.33-
2
.38 (q, 3H, J = 7.9 & 15.8 Hz, ArH), 7.41-7.44 (t, 1H, J = 7.9 Hz, ArH), 7.59 (s, 2H, ArH),
1
3
.71-7.72 (d, 1H, ArH), 8.00 (brs, 1H, NH); C NMR (75 MHz, DMSO-d ): δ 20.4, 24.5, 109.7,
6
10.6, 114.1, 116.2, 116.7, 117.4, 119.4, 119.7, 120.7, 122.3, 123.6, 125.1, 126.1, 128.3 129.1,
+
34.6, 154.3, 155.9, 161.8, 164.9. ESI Mass (m/z) 382 [M+H] ; HRMS: m/z Calculated value
C H N O = 382.1550, Observed value = 382.1553.
24
20
3
2
1
8

ACCEPTED MANUSCRIPT
5
.28 5-(2-(1H-indol-3-yl)ethyl)-2-(4-(3,5,6-trichloropyridin-2-yloxy)-1,3,4-oxadiazole (6u):
0
White solid, Yield : 82%; R = 0.34; m.p. 158-160 C; FTIR (KBr) ν (cm-1): 3223 (N-H), 1063
f
1
(
C-O) cm-1; H NMR (DMSO-d 300 MHz, ppm): δ 3.29 (s, 4H, 2CH ), 6.94-7.05 (m, 3H,
6
,
2
ArH), 7.29-7.31 (t, 3H, ArH), 7.48-7.51 (d, 1H, J = 7.5 Hz, ArH), 8.02-8.05 (d, 2H, J = 8.3 Hz,
1
3
ArH), 8.08 (s, 1H, ArH), 10.50 (brs, 1H, -NH); C NMR (75 MHz, CDCl +DMSO-d ): δ 21.3,
3
6
2
5.4, 110.5, 111.6, 117.0, 117.2, 117.7, 120.1, 120.3, 120.5 (2C), 121.2, 123.4, 125.8, 127.2
+
(
2C), 135.4, 140.2, 142.3, 154.3, 162.3, 162.7, 165.5; ESI Mass (m/z) 485 [M+H] ; HRMS: m/z
Calculated value C H N O Cl = 507.0158, Observed value = 507.0158.
2
3
17
4
2
2
5
.29
5-(3-(1H-indol-3-yl)propyl)-2-(4-(3,5,6-trichloropyridin-2-yloxy)phenyl)-1,3,4-xadiazole
0
(
6v): White solid, Yield : 84%; R = 0.34; m.p. 156-158 C; FTIR (KBr) ν (cm-1): 3254 (N-H),
f
1
1
2
=
082 (C-O); H NMR (CDCl 300 MHz, ppm): δ 2.24-2.33 (m, 2H, CH ), 2.91-2.98 (m, 4H,
3,
2
CH ), 6.98 (s, 1H, ArH), 7.03-7.14 (m, 2H, ArH), 7.25-7.30 (m, 3H, ArH), 7.54-7.56 (d, 1H, J
2
1
3
6.7 Hz, ArH), 7.86 (s, 2H, ArH), 7.98-8.01 (d, 2H, J =7.3 Hz, ArH); C NMR (DMSO-d ,
6
7
1
5MHz, ppm): δ 24.3, 25.0, 26.7, 111.2, 114.7, 118.1, 118.7, 119.2, 121.1, 121.5, 121.90,
21.97, 124.5, 127.2, 128.3 136.3, 141.0, 143.7, 155.3, 155.4, 164.0, 166.9; ESI Mass (m/z) 499
+
[
M+H] ; HRMS: m/z Calculated value C H N O NaCl = 521.0314, Observed value =
2
4
17
4
2
3
5
21.0303.
5
.31 In vivo Anti-inflammatory activity:
In the present investigation, in vivo anti-inflammatory activity of the synthesized
compounds were tested by carrageenan induced rat paw edema method [22-24] using Ibuprofen
as standard. Young adult male Wistar rats weighing 150-200 g were used, which were
acclimatized to the laboratory conditions and maintained on standard laboratory rat feed and
clean water. Rats were fasted for 12 h prior to the experiment, while allowing free access to
water throughout the experiment. The rats were divided into the groups of 6 animals each. A
mark was made on the hind paw (left) just beyond the tibio-tarsal junction, so that every time the
paw was dipped in the mercury column up to the marked level to ensure constant paw volume.
To each group, except the control group, test and standard drugs were administered orally
in a dose of 100 mg/kg of the body weight (0.5 ml of 20 mg/ml drug solutions per 100 g body
weight). The control group received an equivalent amount of vehicle (1% carboxy methyl
1
9

ACCEPTED MANUSCRIPT
cellulose (CMC)). After one hour, carrageenan (0.1 ml, 1% w/v solution in saline) was injected
into the dorsal region of sub-plantar surface of hind paw of control and drug treated groups
subcutaneously with the help of 26G needle. The paw volumes were measured using the
plethysmometer at 0 h, 0.5 h, 1 h, 2 h, 3 h and 4 h after the carrageenan challenge.
Inflammation was expressed as the change in paw edema volume.
Edema = T – T Where T = volume at 0 h, T = Volume at t h.
t
0
0
t
The average value of edema was calculated by taking the average of each group at
different hours. Percentage inhibition of edema was calculated for each group with respect to the
control group.
Percentage inhibition = (V – V )/V × 100. Where, V0 = Volume of the paw of control at
0
t
0
time‘t’
Data are expressed as the mean ± SEM, significant difference between the control and the
treated groups was obtained using Student’s t-test and P values. The difference in results was
considered significant when P < 0.001, percentage reduction in edema formation was calculated
for each compound. The results revealed that of all the tested compounds exhibited significant
inhibition of edema (% protection 68.8, 67.4, 78.3, 62.0, 61.0, 70.9 respectively) comparable to
that of standard Ibuprofen (% protection 72.8).
5
.32 Evaluation of the anti-proliferative activity against A549, HeLa, HepG2 and DU145 cell
lines:
(a) Materials and Methods
All cell lines used in this study were purchased from the American Type Culture
Collection (ATCC, USA). A549, HepG2, and HeLa cells were grown in Dulbecco’s modified
Eagle’s medium containing fetal bovine serum (FBS, 10%) in a humidified atmosphere of 5%
0
CO at 37 C. DU145 cells were cultured in Eagle’s minimal essential medium containing
2
-1
nonessential amino acids, sodium pyruvate (1 mm), bovine insulin (10 mgmL ), and FBS (10%).
Cells were trypsinized when sub-confluent from T75 flasks/90 mm dishes, and seeded in 12-well
5
-1
or 6-well plates at a concentration of 2.5x10 cellsmL in complete medium, and treated with the
2
0

ACCEPTED MANUSCRIPT
test compounds at the desired concentrations for 48 h, then harvested as required. For
immunohistochemistry experiments, wells were seeded on cover slips in a 6-well plate [25].
(b) Anti-proliferative Assay
The synthesized compounds were evaluated for their in vitro cytotoxicity. A protocol of
8 h continuous drug exposure was used, and a 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl
4
tetrazolium bromide (MTT) protein assay was used to estimate cell viability or growth. The cell
lines were grown in the respective media containing FBS (10%) and 2µmL-glutamine and were
inoculated into 96-well micro-titer plates in 200 µL aliquots at plating densities depending on the
0
doubling time of individual cell lines. The micro-titer plates were incubated at 37 C, 5% CO ,
2
9
5% air, and 100% relative humidity for 24 h prior to addition of the experimental drugs.
Aliquots of 2 µL of the drug dilutions were added to the appropriate micro-titer wells already
containing 200 µL of cells, resulting in the required final drug concentrations. For each
compound, four concentrations (1, 10, and 100 µm) were evaluated and each was performed in
triplicate wells. Plates were incubated further for 48 h, and the assay was terminated by the
0
addition of MTT (5%, 10 µL) and incubated for 60 min at 37 C. Later, the plates were air dried.
Bound stain was subsequently eluted with DMSO (100 µL), and the absorbance was read on an
ELISA plate reader at a wavelength of 560 nm. Percent growth was calculated on a plate-by-
plate basis for test wells relative to control wells. The above determinations were repeated three
times. The inhibitory effects of the compounds on cell growth were analyzed by generating dose-
response curves as a plot of the percentage of surviving cells versus drug concentration.
Sensitivity of the cancer cells to the drug treatment was expressed in terms of IC value, a value
5
0
defined as the concentration of compound that produced a 50% reduction relative to the control
absorbance. The percentage of cells killed was obtained from the formula:
Percentage cells killed = 100-mean OD sample x100
mean OD at day 0
Acknowledgement
SR would like to thank UGC (New Delhi) for the Research Fellowship. All authors wish
to thank the Director, IICT and Head of the Crop Protection Chemical Division, for the facilities.
2
1

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2
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Captions:
Fig. 1 Some of the biologically active 3-sustituted indole representatives.
Fig. 2 Graphical representation of the percentage protection of of 5-(3-(indolyl)alkyl)-2-
(substituted)-1,3,4-oxadiazoles against edema formation.
Scheme 1: Synthesis of compounds 6(a-v), Reagents and conditions: (a) H SO reflux, 3-4h (b)
2
4,
NH NH .H O (99%), EtOH, reflux, 5-6h. (c) EtOH, reflux, 4-5h. (d) DIB, DCM, rt, 4-6h.
2
2
2
Table 1 Synthesized 5-(3-(indolyl)alkyl)-2-(substituted)-1,3,4-oxadiazoles.
Table 2 Anti-inflammatory activity of 5-(3-(indolyl)alkyl)-2-(substituted)-1,3,4-oxadiazoles.
Table 3 Percentage protection against edema formation
Table 4 Anti-proliferative activity profile of synthesized 5-(3-(indolyl)alkyl)-2-(substituted)-
1
,3,4-oxadiazoles.
2
5

ACCEPTED MANUSCRIPT
Table 1 Synthesized 5-(3-(indolyl)alkyl)-2-(substituted)-1,3,4-oxadiazoles.
0
Entry
Product
n
R
M. P ( C)
1
2
3
4
5
6
7
8
9
6a
6b
6c
6d
6e
6f
3
3
2
2
2
3
2
3
2
3
2
3
2
2
3
2
2
3
3
2
C H
122-124
143-146
190-193
140-142
132-134
114-116
160-163
153-157
160-161
149-150
117-118
116-117
112-114
154-156
134-136
163-165
154-157
139-142
Hygroscopic
75-78
6
5
1-C H
7
1
0
2-C H N
5
4
3-C H N
5
4
2-C H S
4
3
2-C H S
4
3
6g
6h
6i
4-NO -C H
2 6
4
4-F-C H
6
4
4-Cl-C H
6
4
4
4
4
1
1
1
1
1
1
1
1
1
1
2
0
1
2
3
4
5
6
7
8
9
0
6j
4-Cl-C H
6
6k
6l
3-Cl-C H
6
3-Cl-C H
6
6m
6n
6o
6p
6q
6r
6s
3-Br-C H
6 4
2,6-C H Cl
6
3
2
2
4
3,4-C H Cl
6
3
4-CH -C H
3
6
4-OCH -C H
3
6
4
4
4-OCH -C H
3
6
2,4,6-OCH -C H
2
3
6
6t
4-OC H -C H
6 5 6 4
4
4
-(3,5,6-OC HNCl )-
5 3
2
2
1
2
6u
6v
2
3
136-138
156-158
C H
6
4
-(3,5,6-OC HNCl )-
5
3
C H
6
4
2
6

ACCEPTED MANUSCRIPT
Table 2 Anti-inflammatory activity of 5-(3-(indolyl)alkyl)-2-(substituted)-1,3,4-oxadiazoles.
ab
Dose
Mean paw edema volume in mL±SEM
Treatment
Control
(
mg/kg)
0
.5 h
1 h
2 h
3 h
4 h
100
100
100
100
0.17 ± 0.004
0.13 ± 0.011
0.15 ± 0.018
0.18 ± 0.011
0.36 ± 0.003
0.73 ± 0.003
0.93 ± 0.004
0.91 ± 0.003
6
f
0.27 ± 0.003
0.21 ± 0.008
0.19 ± 0.024
0.39 ± 0.008
0.25 ± 0.018
0.21 ± 0.008
0.29 ± 0.004
0.30 ± 0.013
0.20 ± 0.018
0.48 ± 0.012
0.39 ± 0.008
0.40 ± 0.012
6
h
6
i
6
j
100
0.14 ± 0.008
0.19 ± 0.008
0.35 ± 0.022
0.37 ± 0.011
0.40 ± 0.022
6
6
6
k
p
q
100
100
100
100
100
0.15 ± 0.022
0.16 ± 0.008
0.15 ± 0.013
0.15 ± 0.013
0.14 ± 0.003
0.25 ± 0.022
0.20 ± 0.018
0.17 ± 0.011
0.20 ± 0.018
0.24 ± 0.004
0.42 ± 0.011
0.15 ± 0.018
0.30 ± 0.022
0.24 ± 0.008
0.38 ± 0.005
0.35 ± 0.018
0.39 ± 0.008
0.36 ± 0.008
0.40 ± 0.013
0.31 ± 0.00
0.50 ± 0.013
0.60 ± 0.018
0.38 ± 0.01
0.40 ± 0.013
0.35 ± 0.003
6
r
6
t
Standard
Ibuprofen)
1
00
0.12 ± 0.011
0.22 ± 0.011
0.32 ± 0.011
0.25 ± 0.018
0.33 ± 0.011
(
a
b
All values are represented as means ± SE ‘standard error’. All data significantly different from control value at p < 0.001
Table 3 Percentage protection against edema formation
Dose
mg/kg)
% protection against edema formation
Treatment
(
0
.5 h
1 h
25.0
44.7
2 h
46.5
65.3
3 h
4 h
47.2
56. 7
6
f
100
100
100
100
100
100
100
100
100
23.5
25.0
10.0
30.0
25.0
20.0
25.0
25.0
23.5
68.8
67.4
78.3
59.8
62.0
57.6
61.0
56.5
70.9
6
h
6
i
50.0
50.0
34.2
47.4
55.3
47.4
47.2
70.8
51.4
41. 7
79.2
58.3
66.7
64.3
56.9
55.6
44.4
33.3
57.8
55.6
53.8
6
j
6
6
6
k
p
q
6
r
6
t
Standard
Ibuprofen)
1
00
40.0
42.1
55.5
72.8
63.3
(
2
7