Microwave assisted synthesis of new indophenazine 1,3,5-trisubstruted pyrazoline derivatives of benzofuran and their antimicrobial activity

Article abstract of DOI:10.1016/j.bmcl.2009.03.161

2-[1-(5,8-Dihydro quinoxalino[2,3-b]indoloacetyl)-3-(1-benzofuran-2-yl)-4,5-dihydro-1H-pyr azol-5-yl] phenyl derivatives were synthesized from 2-(5,8-dihydro quinoxalino[2,3-b]indol-5-yl) acetohydrazide and (2E)-1-(1-benzofuran-2-yl)-4-phenylbut-2-en-1-on

Full text of DOI:10.1016/j.bmcl.2009.03.161

Bioorganic & Medicinal Chemistry Letters 19 (2009) 2688–2692
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Microwave assisted synthesis of new indophenazine 1,3,5-trisubstruted
pyrazoline derivatives of benzofuran and their antimicrobial activity
*
Kuntal Manna , Yadvendra K. Agrawal
Institute of Pharmacy, Nirma University of Science and Technology, Sarkhej-Gandhinagar Highway, Ahmedabad 382 481, Gujarat, India
a r t i c l e i n f o
a b s t r a c t
Article history:
2-[1-(5,8-Dihydro quinoxalino[2,3-b]indoloacetyl)-3-(1-benzofuran-2-yl)-4,5-dihydro-1H-pyrazol-5-yl]
phenyl derivatives were synthesized from 2-(5,8-dihydro quinoxalino[2,3-b]indol-5-yl) acetohydrazide
and (2E)-1-(1-benzofuran-2-yl)-4-phenylbut-2-en-1-ones derivatives using microwave-assisted route.
The structures of all the compounds have been established on the basis of analytical and spectral data.
Among the 14 compounds IPB-1, IPB-5, IPB-10, IPB-11 and IPB-12 were found good antibacterial activity
Received 31 January 2009
Revised 20 March 2009
Accepted 26 March 2009
Available online 11 April 2009
and MICs were found bellow 10
aureus, which can compared with sparfloxacin and norfloxacin.
lg/mL against Escherichia coli, Pseudomonas aeruginosa and Streptococcus
Keywords:
Icrowave assisted synthesis
Indophenazine hydrazide
1,3,5-Trisubstruted pyrazoline
Benzofuran
Ó 2009 Elsevier Ltd. All rights reserved.
Antimicrobial activity
Pyrazoline and benzofuran heterocyclic systems are known to
exhibit a wide range of biological properties such as antihypergly-
cemic1, analgesic2, antiinflammatory3, antibacterial4, antifungal4,
and antitumor5 activities. The incorporation of heterocyclic ring
into the benzofuran and pyrazoline ring would be more potent
against multidrug resistant bacteria6,7 than benzofuran and pyra-
zoline ring alone. An in-depth study has been directed toward
the design and synthesis of fused-pyrazole derivatives.8–10 Pyrazo-
lo-oxazinones ring systems11 have not been studied yet regarding
its activity against multidrug resistant bacteria. The present study
has been described the microwave-assisted synthesis12–14 of 2-[1-
(5,8-dihydro quinoxalino[2,3-b]indoloacetyl)-3-(1-benzofuran-2-
The antibacterial activity was screened against multidrug
resistant Escherichia coli, Pseudomonas aeruginosa, Streptococcus
pneumoniae, Streptococcus agalactiae, Salmonella typhi, Streptococcus
aureus, and Streptococcus pyogenes bacteria and carried out by
cylinder and well method.24,25 The MICs were determined using
Mueller–Hinton Broth (MHB) culture media. Agar media (2% in
water) was supplemented in 5% sheep blood and then incubated
in 10% CO2 atmosphere for overnight. After incubation inoculates
were diluted with ringer (oxoid) solution. The final concentration
of inoculums was made approximately 10 CFU/mL. The multidrug
resistant strains of E. coli, P. aeruginosa, S. pneumoniae, S. agalactiae,
S. typhi, S. aureus, and S. pyogenes were treated in Todd–Hewitt
yl)-4,5-dihydro-1H-pyrazol-5-yl] phenyl derivatives19
7
from
medium (Oxoid).6,7 2
lL of the diluted strains were inoculated onto
2-(5,8-dihydro quinoxalino[2,3-b]indol-5-yl) acetohydrazide18
5
6
the individual agar plates. The drug spots were then applied on the
agar culture plate and final size of spots were around 5 Â 103 CFU/
spot. The inoculated plates were then incubated at 37 °C for 20 h in
an incubator. After 20 h of incubation, the zone of inhibitions2 were
measured in mm and compared with standard drugs and vehicle
(Table 1).
with (2E)-1-(1-benzofuran-2-yl)-4-phenylbut-2-en-1-ones20–23
(benzofuran chalcones) and their antibacterial activity against
multidrug resistant bacteria. Microwave-assisted synthetic route
has also been developed for the synthesis of 5,8-dihydro quinoxa-
lino[2,3-b]indole (indophenazine)15 3, ethyl 5,8-dihydro quinoxali-
no[2,3-b]indol-5-yl acetate (6-carbethoxymethyl indophenazine)17
4 and 2-(5,8-dihydro quinoxalino[2,3-b]indol-5-yl) acetohydrazide
(Indophenazine-6-acetic acid hydrazide) 5 using a domestic con-
vection microwave oven (Model No: Samsung, CE1072L-TS).
The antifungal activity was screened against Candida albicans
using agar couture medium.7,24 All the compounds were prepared
with different concentration in DMF and were injected into the
6 mm wells. The plates were incubated at 30 °C for 30–72 h and
then measured zone of inhibitions in mm and compared with stan-
dard drugs.
The microwave-assisted reactions26,27 are more economical,
environmentally friendly (green synthesis), good yield and more
time saving method, which was adopted for the synthesis of all
the compounds in Scheme 1. The microwave-assisted synthetic
* Corresponding author. Tel.: +91 2717 241911/12/13/14/15x723; fax: +91 2717
241917; mob.: 09427042577.
E-mail addresses: k_manna2002@yahoo.com (K. Manna), drykagrawal@yahoo.
com (Y.K. Agrawal).
Tel.: +91 2717 241911/12/13/14/15x723; fax: +91 2717 241917.
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.03.161

K. Manna, Y. K. Agrawal / Bioorg. Med. Chem. Lett. 19 (2009) 2688–2692
2689
Table 1
Antibacterial activities measure by zone of inhibition in mm and MICs were measure by
l
g/mL of all final compounds
Name of compd
–R
Gram-negative bacteria
P. aeruginosa S. typhi
Gram-positive bacteria
E. coli
MIC
1.00
S. agalactiae
S. pneumoniae
S. aureus
S. pyogenes
mm
mm
MIC
mm
MIC
mm
MIC
mm
MIC
mm
MIC
mm
MIC
IPB-1
IPB-2
IPB-3
IPB-4
IPB-5
IPB-6
IPB-7
IPB-8
IPB-9
IPB-10
IPB-11
IPB-12
IPB-13
IPB-14
–OH (o)
18
9
15
12
11
14
16
10
8
10
9
12
13
11
8
3.5
14.5
14.0
6.5
12
10
13
12
14
16
12
15
14
13
16
20
14
12
9.5
11.5
9
10.5
8
11
9
7
22.0
25.0
36.5
24.0
26.0
28.0
32.5
28.0
30.0
22.0
19.0
28.5
26.5
22.5
13
7
10
8
10
11
8
10
9
10
11
8
9
10
8.5
15.5
9.5
13
11
14
12
9
13
14
8
11
12
12
16
10
14
6.0
7.5
7.0
8.5
12.5
9.0
10
15
9
26.0
22.5
25.5
30.5
28.0
26.0
20.5
22.0
25.0
24.0
23.5
28.5
30.0
26.5
–OCH3 (o)
–N (CH3)2 (p)
–COOH (o)
–NO2 (m)
–OH (o), OCH3 (p)
–OH (p)
–Cl (p)
–Cl (o)
–NO2 (o)
–OCH3 (p)
–H
16.5
13.5
13.0
10.5
13.5
14.0
22.5
21.5
5.5
5.0
8.0
15.0
20.5
10
11
13
11
10
7
10
12
11
8
10
10
12
14
8
15.0
13.0
14.5
19.5
16.0
15.0
14.5
12.0
17.0
16.5
14.5
10
12
14
15
14
12
10
14
12
8
5.5
18.5
26.0
16.5
17.5
10.5
12.5
15.5
21.0
18.5
5
8.5
5.5
7
8.5
4.5
2
6.5
16.5
10.0
9.5
8.0
2.5
8
16
17
14
10
8
Furan ring
–CH@CH–Ar
5.6
10
10
9
10.5
4.5
10
10
Sparfloxacin
Norfloxacin
30
20
0.26
1.3
33
28
4.6
1.8
34
22
0.04
0.12
38
32
12.0
22.0
34
24
0.50
20.2
36
28
0.25
1.5
38
30
15.0
2.6
Escherichia coli, Pseudomonas aeruginosa, Streptococcus pneumoniae, Streptococcus agalactiae, Salmonella typhi, Streptococcus aureus, and Streptococcus pyogenes.
mm = zone of inhibitions. MIC = minimum inhibitory concentration.
Scheme 1.

2690
K. Manna, Y. K. Agrawal / Bioorg. Med. Chem. Lett. 19 (2009) 2688–2692
Table 2
the above has been significant activity againstS. pneumoniae and S.
agalactiae. IPB-5, IPB-6, IPB-10, IPB-11 and IPB-12 were good en-
ough, MICs of the compounds were found at 12.5, 9.0, 9.5, 8.0 and
Microwave assisted synthesis compare with ordinary synthesis of all the final
compounds in Scheme 1
Compound
names
–R
Ordinary
synthesis
Microwave assisted
synthesis
2.5 lg/mL, respectively, against S. aureus. All the compounds were
found to possess good activity against S. pyogenes except, IPB-4
and IPB-13. Not a single compound was exhibited significant anti-
fungal activity against C. albicans.
Time of
Yieldb
(%)
Irradiationc
time (min)
Yieldb
(%)
synthesisa (h)
IPB-1
IPB-2
IPB-3
IPB-4
IPB-5
IPB-6
IPB-7
IPB-8
IPB-9
IPB-10
IPB-11
IPB-12
IPB-13
IPB-14
–OH (o)
8
9.5
9
8
9
9.5
9
8
8
8.5
9
28
37
56
62
72
60
36
57
62
68
62
58
47
52
25
20
25
25
25
30
30
28
28
25
28
30
26
25
88
90
92
96
98
90
86
91
92
94
95
88
84
92
Structure–activity relationships suggested that substituted phe-
nyl ring (IPB-1 to IBP-11) at 5-position in 4,5-dihydro pyrazole pro-
duced various antibacterial activity against gram positive and gram
negative bacteria listed in Table 1. The ortho substitution in phenyl
ring with –OH (IPB-1), –NO2 (IPB-10) and para substitution in phe-
nyl ring by –OCH3 (IPB-11) at 5-position pyrazole produced the
best antibacterial activity against gram negative bacteria. Unsub-
stituted phenyl ring (IPB-12) at 5-position pyrazole produced mod-
erate antibacterial activity. When phenyl ring was replaced by five
member ring (IPB-13) at 5-position of pyrazole ring caused reduc-
tion in antibacterial activity. The single C–C bond between pyra-
zole ring and 5-phenyl ring can be replaced by ethenyl bridge
(IPB-14) resulted in moderate antibacterial activity. Ortho substitu-
tion in phenyl ring with –OCH3 (IPB-2), –Cl (IPB-9) and para substi-
tution in phenyl ring by –OH (IPB-7), –Cl (IPB-8) at 5-position
pyrazole produced less or inactive antibacterial activity against
gram negative bacteria. The common structure of compounds did
not support any antifungal activity against C. albicans.
–OCH3 (o)
–N (CH3)2 (p)
–COOH (o)
–NO2 (m)
–OH (o), OCH3 (p)
–OH (p)
–Cl (p)
–Cl (o)
–NO2 (o)
–OCH3 (p)
–H
9.5
8
8
Furan ring
–CH@CH–Ar
a
Reflux in heating equipments.
Percentages of yield calculated from practical and theoretical yields.
40% irradiation energy used (320 W).
b
c
procedure was compared with ordinary synthetic route in Table 2.
The synthesized compounds were established by IR, 1H NMR, mass
and elemental analysis data using Shimadzu-IR 8300, Joel-GSX
400 m, Parkin-Elmer 2400 Series II analyzer and MSN-9629 instru-
ments, respectively.
It can be concluded that, the microwave-assisted synthesis in
having higher regioselective, and more time saving than ordinary
synthesis of pyrazoline containing benzofuran with indophenazine
ring. The potency and selective compounds make them valid leads
for synthesizing new compounds with better activity and exhibit-
ing lower MICs values.
The N–H, one proton in indophenazine ring was established
by sharp 1H NMR peak at 9.834 ppm (s, 1H) and 3402, 3169,
3130 cmÀ1 in IR. Oxazolidine ring was established by 1H NMR
peak at 8.42–7.65 ppm, by IR (cmÀ1): 3402, 3169
m
(NH), 1686
Acknowledgment
m(CH), 1617 m(C@N). 6-carbethoxymethyl indophenazine struc-
ture was characterized by sharp 1H NMR peak at 5.064–
1.25 ppm (s, N–CH2), where N–H peak was absent and additional
4.18 ppm (d, 2H, J = 7.12) O–CH2–CH3, 1.25 ppm (d, 3H, J = 9.32)
O–CH2–CH3 peaks were obtained. The IR peaks 1738 and
1748 cmÀ1 (C@O), 1678 (CH), 1614 (C@C) and (C@N) were sup-
ported for the establishment of the structure. Indophenazine-6-
acetic acid hydrazide structure was characterized by sharp 1H
NMR peak at 8.92 (s, 1H) NHNH2 and 5.78 (s, 2H) NHNH2. The
IR peaks 1614 cmÀ1 (C@C) and (C@N), 1546 cmÀ1 (NH), 1488,
1467 cmÀ1 (C@N) and (C@C) were reconfirmed the structure.
First final compound IPB-1 was elucidated by 1H NMR, IR, Mass
and elemental analysis data, where 1H NMR and IR peaks of
NHNH2 were not found, but sharp 1H NMR peak at 3.6 (s, 1H)
for one proton in position 5 and 2.3 (s, 2H) for two protons at
position 4 in pyrazoline ring, were established the structure of
pyrazoline. In Mass spectra, m/z: 537.75 (molecular ion peak)
was found same with actual molecular weight of the compound
and 100% base peak of the important fragment was also re-
corded at m/z: 145.20. The IR data, 3373 (O–H str.), 1345,
1169 (C–O str.) and the data of elemental analysis were reestab-
lished the structure of first final compound by 0.84% different in
calculated C, H, N, O values with founded values. Similar way we
interpreted and characterized all the final compounds.19 Antibac-
terial activity of the compounds was endowed with higher activ-
ity against 7 different multidrug resistant organisms in various
concentrations (Table 1). The MICs of the compounds were found
satisfactory and compared with standard fluoroquinolones drugs.
By comparing the compounds IPB-1, IPB-5, IPB-10, IPB-11 and IPB-
12 were found better active against E. coli, P. aeruginosa, S. typhi
and S. aureus but rests of other pathogens were not found signified
activity. IPB-1, IPB-5, IPB-10, IPB-11 and IPB-12 were having inhib-
ited capacity than others against E. coli. The MICs of the compounds
The authors would like to thank to Department of Microbiology,
Kasturba Medical College, Manipal, India for providing laboratory
facilities to carryover the antibacterial and antifungal activities.
We gratefully acknowledge to IISc, Bangalore, IIT, Chennai and SPIC
Foundation, Chennai for providing 1H NMR spectra, Mass spectra
and other analytical support.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2009.03.161.
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J = 8.52 Hz), 7.92 (s, 1H), 7.58 (d, 1H, J = 1.55, 8.5 Hz), 7.48 (d, 6H, J = 7.64 Hz),
6.9 (d, 4H, J = 8.74 Hz), 5.85 (d, 1H, J = 8.36)CH, 3.9 (s, 6H), 2.4 (s, 3H); MS (FAB)
m/z: 565.12 (m+), 145.20 (100%); C34H28N6O2 (564.64): Calcd: C, 74.45; H, 5.01;
N, 14.88; O, 5.68. Found: C, 74.96; H, 5.18; N, 14.51. IPB-4: White solid was
recrystallized from 95% of ethanol; yield: 96%, mp: 198–200 °C, Rf = 0.54
15. Indophenazine (5,8-dihydro quinoxalino[2,3-b]indole)
3
was prepared by
(benzene:ethyl acetate, 3:1); kmax: 298.2 nm; IR (KBr) m
max (cmÀ1): 3402 (O–H
stirring 0.05 mol of isatin with equivalent amount of ortho-phenylene
1
str.), 1711, 1697 (C@O str.), 1173–1074 (C–O str.); 1H NMR (CDCl3, 300 MHz) d
(ppm): 11.13 (s, 1H) COOH, 8.21 (dd, 2H, J = 3.6, 6.32 Hz), 8.10 (d, 1H,
J = 8.51 Hz), 7.80 (dd, 2H, J = 3.41, 6.22 Hz), 7.57 (s, 4H), 7.29 (s, 6H), 3.55 (s,
6H), 2.13 (s, 2H); MS (FAB) m/z: 565.87 (m+), 145.20 (100%); C34H23N5O4
(565.58): Calcd: C, 72.21; H, 4.01; N, 12.38; O, 11.32. Found: C, 72.90; H, 4.28;
N, 12.56. IPB-5: White solid was recrystallized from methanol; yield: 98%, mp:
97–99 °C, Rf = 0.63 (benzene:ethyl acetate, 3:1); kmax: 265.4 nm; IR (KBr) mmax
(cmÀ1): 1527 (asy) (NO2 str.), 1346 (sym) (NO2 str.), 883 (C–N str.). 877; 1H
NMR (CDCl3, 300 MHz) d (ppm): 9.2 (d, 1H, J = 2.38 Hz), 8.53 (dd, 1H, J = 2.38,
9.10 Hz), 8.39 (d, 1H, J = 9.10 Hz), 7.6 (s, 4H), 7.42 (s, 6H).; MS (FAB) m/z:
566.35(m+), 145.14 (100%); C33H22N6O4 (566.57): Calcd: C, 69.96; H, 3.91; N,
14.83; O, 11.30. Found: C, 70.10; H, 3.78; N, 14.36. IPB-6: Light yellow solid
was recrystallized from methanol; yield: 90%, mp: 223–225 °C, Rf = 0.54
(benzene:ethyl acetate, 3:1); kmax: 267.6 nm; IR (KBr) mmax (cmÀ1): 3240 (O–
H str.), 1383 (O–H ben.), 1170–1080 (C–O str.), 1020 (C–O–C str.), 2927 (CH3
str.), 1450 (CH3 def.); 1H NMR (CDCl3, 300 MHz) d (ppm): 8.25 (dd, 2H, J = 3.34,
6.34 Hz), 7.81 (dd, 2H, J = 3.47, 6.36 Hz), 7.35 (d, 4H, J = 8.41 Hz), 7.42 (s, 6H),
7.31 (d, 1H, J = 4.23) Ph–OH, 6.82 (d, 4H, J = 8.73 Hz), 3.20 (s, 3H) Ph-OCH3, 2.4
(s, 2H); MS (FAB) m/z: 567.62 (m+), 145.22 (100%); C34H25N5O4 (566.57): Calcd:
C, 71.95; H, 4.44; N, 12.34; O, 11.28. Found: C, 71.23; H, 4.18; N, 12.56. IPB-7:
White solid was recrystallized from methanol; yield: 86%, mp: 154–156 °C,
Rf = 0.78 (benzene:ethyl acetate, 3:1); kmax: 220.3 nm; IR (KBr) mmax (cmÀ1):
3367 (O-H str.), 1367–1252 (O–H ben.), 1172–1012 (C–O str.); 1H NMR (CDCl3,
300 MHz) d (ppm): 8.32 (dd, 2H, J = 3.45, 6.32 Hz), 7.81 (dd, 2H, J = 3.54,
6.41 Hz), 7.24 (s, 4H), 7.42 (s, 6H), 6.27 (s, 1H) OH, 3.56 (s, 6H), 2.3 (s, 2H); MS
(FAB) m/z: 537.55 (m+), 145.30 (100%); C33H23N5O3 (537.57): Calcd: C, 73.73;
H, 4.31; N, 13.03; O, 8.93. Found: C, 73.14; H, 4.48; N, 13.36. IPB-8: White solid
was recrystallized from 95% of ethanol; yield: 91%, mp: 213–215 °C, Rf = 0.95
diamines 2 at room temperature in presence of 2-Iodoxybenzoic acid (IBX)
according to previously published procedures.16 Yield 70% and mp 262 °C.
The microwave assisted synthesis of indophenazine was established; using
equivalent amount of isatin (0.05 mol) and ortho-phenylene diamine in 8 mL of
glacial acetic acid into a 50 mL conical flask (borosilicate), which covered with
small funnel. The flask was placed in a microwave oven for 6 min at 20%
(160 W) energy level. The progress of the reaction was monitored by TLC
(Benzene:Methanol, 3:1). The solution was poured in 100 mL ice-cold water
and neutralized with 5% NaHCO3 solution. The organic layer was extracted
with diethyl ether (2 Â 5 mL) and washed with brine (2 Â 5 mL), and dried over
MgSO4. The solvent was evaporated by rotary evaporator and pure compound
was obtained by recrystallization with hot ethyl acetate. Yield 97% and mp:
264 °C; IR (KBr) mmax (cmÀ1): 3402, 3169, 3130
(C@C), (C@N), 1555 d(NH), 1490, 1465 (C@N),
888 (C@C), 1166, 789, 747 d(CH), 689 (CH), 663 d(CH), 626
(C@C).; 1H NMR (300 MHz, CDCl3) d (ppm): 10.40 (s, 1H) NH, 7.45–7.58 (d,
m
m
(NH), 1686
(C@C), 1300 d(CH), 1242,
(NH), 549
m(CH), 1617
m
m
m
p
m
p
p
1H, J = 7.2 Hz) CH, 7.22–7.42 (m, 4H, J = 8.4 Hz) CH, 6.92–7.22 (m, 3H,
J = 8.1 Hz) isatin ring.
Indophenazine (5,8-dihydro quinoxalino[2,3-b]indole)
3 was prepared by
stirring 0.05 mol of isatin with equivalent amount of ortho-phenylene
1
diamines 2 at room temperature in presence of 2-Iodoxybenzoic acid (IBX)
according to previously published procedures.16 Yield 70% and mp 262 °C.
16. Mao, L.; Sakurai, H.; Hirao, T. Synthesis 2004, 2535.
17. 6-Carbethoxymethyl indophenazine (ethyl 5,8-dihydro quinoxalino[2,3-
b]indol-5-yl acetate) 4 was prepared by microwave irradiation (160 W) from
indophenazine (0.01 mol) 3 and ethyl chloro acetate (0.015 mol) into a 50 mL
conical flask (borosilicate). To that added 2 mL of dry acetone and 0.2 mol of
anhydrous potassium carbonate portion wise. Then covered the flask with
small funnel and irradiated for 2 h. The solvent was evaporated under reduced
pressure and poured in to 100 mL ice-cold water with stirring. Solid was
separated by filtration and recrystallized from hot 95% ethanol. Yield 88% and
mp: 188 °C; IR (KBr) mmax (cmÀ1): 1738 and 1748 (C@O), 1678 (CH), 1614
(C@C) and (C@N), 1488 and 1467 (C@N), (C@C), 1320 (CH), 1225 (C–O), 1240,
880 (C@C), 1158, 781, 750 (CH), 692 (CH), 671 (CH), 551 (C@C); 1H NMR
(300 MHz, CDCl3) d (ppm): 7.36–7.48 (d, 1H, J = 6.9 Hz) CH, 7.26–7.40 (m, 4H,
J = 8.0 Hz) CH, 7.10–7.25 (m, 3H, J = 8.3 Hz) isatin ring, 5.12 (s, 2H) CH2, 4.18 (d,
2H, J = 7.11 Hz) CH2CH3.
(benzene:ethyl acetate, 3:1); kmax: 197.6 nm; IR (KBr) m
max (cmÀ1): 3240 (C–Cl
str.), 1035 (C–O–C str.), 2930 (CH3 str.), 1447 (CH3 def.), 1599, 786, 746 (C–Cl
str.); 1H NMR (CDCl3, 300 MHz) d (ppm): 8.5 (dd, 2H, J = 3.42, 7.23 Hz), 7.82
(dd, 2H, J = 3.40, 8.40 Hz), 7.52 (dd, 4H, J = 1.42, 8.64 Hz), 7.15 (dd, 4H, J = 2.63,
8.64 Hz), 5.75 (s, H), 4.96 (s, 2H), 3.56 (s, 2H); MS (FAB) m/z: 556.84 (m+),
144.97 (100%); C33H22N5O2Cl (556.04): Calcd: C, 71.29; H, 3.99; N, 12.60; O,
5.71; Cl, 6.38. Found: C, 71.72; H, 4.14; N, 12.36. IPB-9: White solid was
recrystallized from 95% of ethanol; yield: 92%, mp: 195–197 °C, Rf = 0.87
(benzene:ethyl acetate, 3:1); kmax: 216.4 nm; IR (KBr) m
max (cmÀ1): 3255 (C–Cl
str.), 1042 (C–O–C str.), 2912 (CH3 str.), 1433 (CH3 def.), 1601, 790, 748 (C–Cl
str.);; 1H NMR (CDCl3, 300 MHz) d (ppm): 8.31 (dd, 2H, J = 3.44, 6.22 Hz), 7.82
(dd, 2H, J = 3.44, 6.40 Hz), 7.22 (s, 4H), 7.40 (s, 6H), 3.55 (s, 6H), 2.3 (s, 2H); MS
(FAB) m/z: 556.34 (m+), 145.40 (100%); C33H22N5O2Cl (556.04): Calcd: C, 71.29;
H, 3.99; N, 12.60; O, 5.71; Cl, 6.38. Found: C, 71.12; H, 3.62; N, 12.16. IPB-10:
Light yellow solid was recrystallized from methanol; yield: 94%, mp: 105–
107 °C, Rf = 0.82 (benzene:ethyl acetate, 3:1); kmax: 280.6 nm; IR (KBr) mmax
(cmÀ1): 3089, 1599, 1552 (asy) (NO2 str.), 1344 (sym) (NO2 str.), 815 (C–N str.);
1H NMR (CDCl3, 300 MHz) d (ppm): 9.1 (d, 1H, J = 2.41 Hz), 8.56 (dd, 1H,
J = 2.32, 9.20 Hz), 8.30 (d, 1H, J = 9.17 Hz), 7.6 (s, 4H), 7.22 (s, 6H); MS (FAB) m/
z: 566.95(m+), 145.14 (100%); C33H22N6O4 (566.57): Calcd: C, 69.96; H, 3.91; N,
14.83; O, 11.30. Found: C, 70.13; H, 3.48; N, 14.86. IPB-11: Light brown solid
was recrystallized from methanol; yield: 95%, mp: 164–166 °C, Rf = 0.64
(benzene:ethyl acetate, 3:1); kmax: 240.2 nm; IR (KBr) mmax (cmÀ1): 3010,
1602, 1170–1026 (C–O–C str.), 2837 (CH3 str.), 1446 (CH3 def.); 1H NMR
(CDCl3, 300 MHz) d (ppm): 8.12 (dd, 2H, J = 3.42, 6.30 Hz), 7.69 (dd, 2H, J = 3.39,
6.30 Hz), 7.57 (d, 4H, J = 8.72 Hz), 7.41 (s, 6H), 6.90 (d, 4H, J = 8.63 Hz), 3.60 (s,
6H), 2.35 (s, 2H); MS (FAB) m/z: 552.00 (m+), 145.20 (100%); C34H25N5O3
(551.60): Calcd: C, 74.03; H, 4.57; N, 12.71; O, 8.70. Found: C, 74.17; H, 4.78; N,
12.96. IPB-12: Light yellowish solid was recrystallized from methanol; yield:
88%, mp: 215–217 °C, Rf = 0.86 (benzene:ethyl acetate, 3:1); kmax: 203.2 nm; IR
(KBr) mmax (cmÀ1): 3063, 1660, 1592; 1H NMR (CDCl3, 300 MHz) d (ppm): 8.10
(d, 1H, J = 8.52 Hz), 7.91 (s, 1H), 7.63 (dd, 1H, J = 1.72, 8.52 Hz), 7.22 (s, 4H),
7.40 (s, 6H), 3.55 (s, 6H); MS (FAB) m/z: 519.00 (m+), 145.00 (100%);
C33H23N5O2 (537.57): Calcd: C, 75.99; H, 4.44; N, 13.43; O, 6.13. Found: C,
76.12; H, 4.68; N, 13.59. IPB-13: Yellowish white solid was recrystallized from
methanol; yield: 84%, mp: 185–187 °C, Rf = 0.95 (benzene:ethyl acetate, 3:1);
kmax: 358.0 nm; IR (KBr) mmax (cmÀ1): 3134 (C-H str.), 1550 (furan), 742 (C–H
ban.); 1H NMR (CDCl3, 300 MHz) d (ppm): 8.14 (d, 1H, J = 8.53 Hz), 7.89 (s, 1H),
7.62 (dd, 1H, J = 1.70, 8.56 Hz), 7.24 (s, 4H), 7.42 (s, 6H), 5.73 (s, 1H), 5.82 (d,
2H, J = 5.23), 3.58 (s, 4H); MS (FAB) m/z: 509.81(m+), 145.00 (100%);
C32H23N5O2 (509.57): Calcd: C, 75.43; H, 4.55; N, 13.75; O, 6.28. Found: C,
75.40; H, 4.18; N, 13.86. IPB-14: Light brown solid was recrystallized from
methanol; yield: 92%, mp: 173–175 °C, Rf = 0.89 (benzene:ethyl acetate, 4:1);
kmax: 348.7 nm; IR (KBr) mmax (cmÀ1): 2933, 1610, 978 (R–CH = CHR); 1H NMR
(CDCl3, 300 MHz) d (ppm): 8.44 (d, 1H, J = 8.60 Hz), 7.78 (s, 1H), 7.55 (dd, 1H,
J = 2.70, 8.20 Hz), 7.32 (s, 4H), 7.60 (s, 6H), 3.52 (s, 4H); MS (FAB) m/z:
549.17(m+), 145.10 (100%); C35H27N5O2 (549.63): Calcd: C, 76.49; H, 4.95; N,
12.74; O, 5.82. Found: C, 76.90; H, 4.13; N, 12.56.
18. Indophenazine-6-acetic acid hydrazide (2-(5,8-dihydro quinoxalino[2,3-
b]indol-5-yl) acetohydrazide) 5 was synthesized from 6-carbethoxymethyl
indophenazine (0.1 mol) 4 and hydrazine hydrate (99%, 0.4 mol) into 30 mL of
absolute ethanol in a 50 mL conical flask (borosilicate). The flask was covered
by small funnel and placed in a microwave oven for 140 s at 40% (320 W)
energy level. Excess of ethanol was removed under reduced pressure, and then
resulting solution was poured in ice-cold water. Solid was obtained by
filtration and recrystallized from hot dioxan. Yield 94% and mp: 216 °C; IR
(KBr) m
max (cmÀ1): 1738, 1748 (C@O), 1678 (CH), 1614 (C@C) and (C@N), 1546
(NH), 1488, 1467 (C@N) and (C@C), 1320 (CH), 1225 (C–O), 1240 and 880
(C@C), 1158, 781 and 750 (CH), 692 (CH), 671 (CH), 632 (NH), 551 (C@C); 1H
NMR (300 MHz, CDCl3)
d (ppm): 8.92 (s, 1H) NHNH2, 7.36–7.48 (d, 1H,
J = 6.9 Hz) CH, 7.26–7.40 (m, 4H, J = 8.0 Hz) CH, 7.10–7.25 (m, 3H, J = 8.3 Hz)
isatin ring, 5.78 (s, 2H) NHNH2, 4.95 (d, 2H, J = 7.23) NCH2.
19. 1. General procedure for the synthesis of 2-[1-(5,8-dihydro quinoxalino[2,3-
b]indoloacetyl)-3-(1-benzofuran-2-yl)-4,5-dihydro-1H-pyrazol-5-yl] phenyl
derivatives 7 from benzofuran chalcones (0.01 mol) 6 and indophenazine-6-
acetic acid hydrazide (0.02 mol) 5 were dissolved in 20 mL of glacial acetic acid
in a 50 mL conical flask made up of borosil. The flask was then covered with
small funnel (borosilicate) and irradiated by a microwave oven at 40% (320 W)
energy level; the reaction times are mention in Table 2. Reaction was
monitored by TLC using silica gel-G. The excess of solvent was evaporated
under reduced pressure and resulting solution was poured in ice-cold water
with stirring. The solid was separated by filtration and recrystallized from
suitable solvent. IPB-1: White solid was recrystallized from 95% of ethanol;
yield: 88%, mp: 155–157 °C, Rf = 0.88 (benzene:ethyl acetate, 3:1); kmax:
236.2 nm; IR (KBr) mmax (cmÀ1): 3373 (O–H str.), 1454 (aromatic), 1345, 1169
(C–O str.); 1H NMR (CDCl3, 300 MHz) d (ppm): 9.86 (s, 1H) OH, 7.79 (dd, 2H,
J = 3.41, 6.2 Hz) CH, 7.55 (s, 4H), 7.39 (s, 6H), 3.6 (s, 1H), 2.3 (s, 2H); MS (FAB)
m/z: 537.75 (m+), 145.20 (100%); C33H23N5O3 (537.57): Calcd: C, 73.73; H, 4.31;
N, 13.03; O, 8.93. Found: C, 73.90; H, 4.18; N, 13.56. IPB-2: Yellowish white
solid was recrystallized from methanol; yield: 90%, mp: 71–73 °C, Rf = 0.79
(benzene:ethyl acetate, 2:1); kmax: 306.6 nm; IR (KBr) m
max (cmÀ1): 1169–1026
(C-O-C str.), 2839 (CH3 str.), 1456 (CH3 def.); 1H NMR (CDCl3, 300 MHz) d
(ppm): 8.15 (dd, 2H, J = 3.44, 6.32 Hz), 7.7 (dd, 2H J = 3.44, 6.32 Hz), 7.55 (d, 4H,
J = 8.7 Hz), 7.39 (s, 6H), 6.89 (d, 4H, J = 8.73 Hz), 4.97 (s, 2H) NCH2, 4.01(s, 3H)
OCH3, 3.61 (s, 6H), 2.4 (s, 2H); MS (FAB) m/z: 551.90 (m+), 145.13 (100%);
C34H25N5O3 (551.60): Calcd: C, 74.034; H, 4.57; N, 12.71; O, 8.70. Found: C,
73.97; H, 4.18; N, 12.16. IPB-3: White solid was recrystallized from methanol;
yield: 92%, mp: 103–105 °C, Rf = 0.94 (benzene:ethyl acetate, 2:1); kmax:
296.4 nm; IR (KBr) mmax (cmÀ1): 2925, 2804 (Ar–N–CH3 str.), 1446 (CH3 ban.),
20. General procedure for the synthesis of (2E)-1-(1-benzofuran-2-yl)-4-
phenylbut-2-en-1-ones (benzofuran chalcones)21–23
6
from 2-acetyl
benzofuran (0.05 mol) and different aromatic aldehydes (0.05 mol) were
taken in 20 mL of ethanol (98%) in 50 mL conical flask made up of borosil. To
1365, 1317 (C–N str.); 1H NMR (CDCl3, 300 MHz)
d (ppm): 8.05 (d, 1H,

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K. Manna, Y. K. Agrawal / Bioorg. Med. Chem. Lett. 19 (2009) 2688–2692
that added 20% KOH/NaOH solution (8 mL), and covered the flask with small
funnel (borosilicate). The flask was placed in a microwave oven at 30% (240 W)
23. Babu, V. H.; Manna, K.; Sneha, J.; Srinivasan, K. K.; Bhat, V. Indian J. Heterocycl.
Chem 2004, 13, 253.
energy level for 8 min. The resulted solution was poured in 100 mL ice-cold
water, and acidified with concd HCl. Excess of solvent was removed under
reduced pressure and solid was obtained by filtration.
24. Reinert, R. R.; Lutticken, R.; Bryskier, A.; Lahham, A. Antimicrob. Agents
Chemother. 2003, 47, 489.
25. Karginova, C.; Sahm, D. F. Antimicrob. Agents Chemother. 2002, 46, 2651.
26. Ding, D.; Li, X.; Wang, X.; Du, Y.; Shen, J. Tetrahedron Lett. 2006, 47, 6997.
27. Tan, W.; Zhao, B. X.; Sha, L.; Jiao, P. F.; Wan, M. S.; Su, L. D.; Shin, S. Synth.
Commun. 2006, 36, 1353.
21. Manna, K.; Agrawal, Y. K. Indian J. Heterocycl. Chem. 2008, 17, 87.
22. Agrawal, Y. K.; Manna, K.; Babu, V. H.; Srinivasan, K. K.; Bhatt, H.; Gogoi, P. J.
Indian J. Heterocycl. Chem. 2007, 16, 263.