Efficient microwave irradiation enhanced stereoselective synthesis and antitumor activity of indolylchalcones and their pyrazoline analogs

Article abstract of DOI:10.1007/s12039-010-0093-9

2-Aryl-1H-indole-3-carbaldehyde derivatives underwent Claisen-Schmidt condensation with acetophenone derivatives under microwave irradiation condition compared with the conventional heating to afford excellent yields of trans substituted indolylchalcones

Full text of DOI:10.1007/s12039-010-0093-9

J. Chem. Sci., Vol. 122, No. 4, July 2010, pp. 587–595. © Indian Academy of Sciences.
Efficient microwave irradiation enhanced stereoselective synthesis and
antitumor activity of indolylchalcones and their pyrazoline analogs
MAGDY A H ZAHRAN1,*, HANAN F SALAMA1, YASMIN G ABDIN1 and
AMIRA M GAMAL-ELDEEN2
1
Organic Chemistry Laboratory, Department of Chemistry, Faculty of Science, Menoufiya University,
Shebin Elkom 32511, Menoufiya, Egypt
2
Cancer Biology Laboratory, Center of Excellency for Advanced Sciences, National Research Center,
Dokki 12622, Cairo, Egypt
e-mail: magdyzahran@gmail.com
MS received 5 August 2009; revised 11 January 2010; accepted 7 May 2010
Abstract. 2-Aryl-1H-indole-3-carbaldehyde derivatives underwent Claisen–Schmidt condensation with
acetophenone derivatives under microwave irradiation condition compared with the conventional heating
to afford excellent yields of trans substituted indolylchalcones which subjected to condensation reaction with
phenylhydrazine to afford their indolylpyrazoline analogs. The antitumor activity of the synthesized
compounds was examined and evaluated against human hepatocellular carcinoma cell line (Hep-G2) as well
as the half maximal inhibitory concentration (IC50). Most of them showed high potent antitumor activity.
Keywords. Indolylchalcones; indolylpyrazolines; microwave irradiation; stereoselectivity; antitumor;
Hep-G2.
1. Introduction
On the other hand, microwave assisted organic
synthesis (MAOS) has become increasingly popular
in recent years to improve the yields and shorten
reaction times in a variety of reactions.19
Indole nucleus is an important structural component
in many drugs.1,2 In addition, several indole deriva-
tives have been reported to possess a wide variety of
biological and pharmacological properties.3–7
Chalcones, 1,3-diarylprop-1-en-2-ones, are a class
of compounds consisting of two aryl rings linked by
an α,β-unsaturated ketone moiety. Some chalcones
are natural products found in various plant species
around the world and in the last decade they have
been shown to display a wide range of medicinal
properties.8–11 The anticancer activity of certain
chalcones is believed to be a result of binding to
tubulin and preventing it from polymerising into
microtubules.12
Pyrazolines are important nitrogen-containing
five-membered heterocyclic compounds. Several
pyrazoline derivatives possess important pharma-
cological activities and therefore they are useful
materials in drug research.13 Moreover, pyrazoline
derivatives were found to possess antitumor,14 anti-
bacterial,15 anti-inflammatory,16 antidiabetic17 and
antidepressant activities.18
Prompted by the above-mentioned biological
properties of indoles, chalcones, pyrazolines and the
interest with design and synthesis of indole and
pyrazoline derivatives,20–22 as well as the utility of
microwave irradiation in organic synthesis,22,23
a
synthesis of novel series of substituted 3-(2-aryl-1H-
indol-3-yl)-prop-2-en-1-ones and their substituted
1-phenyl-3-aryl-5-(2-arylindolyl)-pyrazoline analogs
via both microwave irradiation and the conventional
method were presented. Subsequently, investigation
of their cytotoxic effect in vitro against human hepa-
tocellular carcinoma cell line (Hep-G2) has been
illustrated.
2. Experimental
2.1 Materials, method and instruments
All melting points were taken on a Stuart scientific
melting point apparatus (Stuart Scientific, Stone,
and Staffordshire, UK) and were uncorrected. The
1H-NMR spectra were recorded on a Varian Ger-
*For correspondence
587

588
Magdy A H Zahran et al
mini-2000 (300 MHz) spectrometer (Varian Inc., The precipitated solid was filtered off, washed with
Palo Alto, CA, USA), using TMS as the internal water, dried and recrystallized from ethanol to
standard and with DMSO-d6 as the solvent; the afford the pure product 3a–l.
chemical shifts are reported in ppm (δ) and coupling
constants (J) values are given in Hertz (Hz). Signal 2.2c (E)-3-(1-Allyl-2-phenyl-1H-indol-3-yl)-1-phenyl-
multiplicities are represented by: s (singlet), d (dou- prop-2-en-1-one (3a): Yellow solid; m.p. 66–
blet), t (triplet), q (quartet), dd (double doublet) and 68°C; IR νmax (KBr) 3054 (CH=CH), 1649 (C=O);
m (multiplet). IR spectra were obtained on a Nicollet 1H–NMR (DMSO–d6) δ (ppm): 4⋅71–4⋅73 (m, 1H,
IR 200 FT–IR spectrophotometer using KBr pellets. =CH2), 4⋅81 (d, 2H, NCH2), 5⋅10 (d, 1H, =CH2),
Elemental analyses (C, H, N) were conducted using 5⋅83–5⋅96 (m, 1H, CH=), 7⋅34–8⋅25 (m, 14H, ArH),
the Elemental Analyzer Yanaca CHN Corder MT-3, 7⋅51 (d, 1H, J = 15 Hz), 7⋅62 (d, 1H, J = 15 Hz); MS
their results were found to be in good agreement (EI), m/z 363 (M+, 44). Anal. Calcd. for C26H21NO:
( 0⋅3%) with the calculated values. MS spectra C, 85⋅92; H, 5⋅82; N, 3⋅85. Found: C, 85⋅99; H,
were established on GC MS-QP 1000 EX Mass 6⋅07; N, 3⋅94.
Spectrometer (Shimadzu, Tokyo, Japan). The mi-
crowave-induced reactions were carried out in an 2.2d (E)-3-(1-Allyl-2-phenyl-1H-indol-3-yl)-1-(4-
open Pyrex-glass vessel under atmospheric pressure nitrophenyl)-prop-2-en-1-one (3b): Pale red crys-
in domestic Whirl Pool-TALENT oven. The synthe- tals; m.p. 188–190°C; IR νmax (KBr) 3052 (CH=CH),
1
sized products and each reaction were carried out 1648 (C=O); H–NMR (DMSO-d6) δ (ppm): 4⋅73–
under conventionally or microwave (MW) irradia- 4⋅74 (m, 1H, =CH2), 4⋅81 (d, 2H, NCH2), 5⋅11 (d,
tion conditions were monitored on Merck silica gel 1H, =CH2), 5⋅86–5⋅96 (m, 1H, CH=), 7⋅36–8⋅34 (m,
60 F254 plates (type E; Merck, Darmstadt, Ger- 13H, ArH), 8⋅25 (d, 1H, J = 15⋅3 Hz), 8⋅34 (d, 1H,
many) using UV light (254 and 360 nm) for detec- J = 15⋅3 Hz); MS (EI), m/z 408 (M+, 46). Anal.
tion. The required starting material, 1, was prepared Calcd. for C26H20N2O3: C, 76⋅45; H, 4⋅94; N, 6⋅86.
by adopting the earlier reported procedures.22b All Found: C, 76⋅50; H, 5⋅19; N, 6⋅97.
chemicals and solvents were purchased from E.
Merck (Darmstadt, Germany) and Sigma-Aldrich. 2.2e (E)-3-(1-Allyl-2-phenyl-1H-indol-3-yl)-1-bi-
All diagrams and calculations were performed using phenyl-4-yl-prop-2-en-1-one (3c): Yellow crystals;
maxus (Bruker Nonius, Delft & MacScience, Japan). m.p. 110–112°C; IR νmax (KBr) 3063 (CH=CH),
1
1644 (C=O); H–NMR (DMSO–d6) δ (ppm): 4⋅72–
4⋅74 (m, 1H, =CH2), 4⋅81 (d, 2H, NCH2), 5⋅11 (d,
2.2 General procedure for the synthesis of
1H, =CH2), 5⋅84–5⋅96 (m, 1H, CH=), 7⋅36–8⋅25 (m,
indolylchalcone derivatives 3a–l
18H, ArH), 7⋅83 (d, 1H, J = 15⋅3 Hz), 8⋅14 (d, 1H,
J = 15⋅3 Hz); MS (EI), m/z 439 (M+, 45). Anal.
2.2a Microwave irradiation procedure: A mix-
Calcd. for C32H25NO: C, 87⋅44; H, 5⋅73; N, 3⋅19.
ture of 2-aryl-1H-indole-3-carbaldehyde 1 (1 mmol),
Found: C, 87⋅51; H, 5⋅98; N, 3⋅30.
acetophenone 2 (1 mmol), ethylene glycol (1 mL)
and piperidine (0⋅5 mL) in a Pyrex-glass opened
vessel was subjected to a microwave irradiation at
750 W. Irradiation was carried out in successive of
30 s periods (table 1). After cooling to room tempe-
rature, water (10 mL) was added to the mixture. The
precipitated solid was filtered off, washed with wa-
ter, dried and recrystallized from ethanol to
2.2f (E)-3-(1-Allyl-2-p-tolyl-1H-indol-3-yl)-1-phenyl-
prop-2-en-1-one (3d): Yellow solid; m.p. 110–
112°C; IR νmax (KBr) 3029 (CH=CH), 1650 (C=O);
1H–NMR (DMSO–d6) δ (ppm): 2⋅41 (s, 3H, CH3),
4⋅72–4⋅73 (m, 1H, =CH2), 4⋅81 (d, 2H, NCH2), 5⋅10
(d, 1H, =CH2), 5⋅83–5⋅96 (m, 1H, CH=), 7⋅33–8⋅27
(m, 13H, ArH), 7⋅77 (d, 1H, J = 15⋅6 Hz), 7⋅83 (d,
afford the pure product 3a–l.
1H, J = 15⋅6 Hz); MS (EI), m/z 377 (M+, 48). Anal.
Calcd. for C27H23NO: C, 85⋅91; H, 6⋅14; N, 3⋅71.
Found: C, 85⋅98; H, 6⋅40; N, 3⋅60.
2.2b Conventional heating procedure: A mixture
of 2-aryl-1H-indole-3-carbaldehyde 1 (1 mmol),
acetophenone 2 (1 mmol), ethylene glycol (5 mL)
2.2g (E)-3-(1-Allyl-2-p-tolyl-1H-indol-3-yl)-1-(4-
nitrophenyl)-prop-2-en-1-one (3e): Yellow solid;
m.p. 130–132°C; IR νmax (KBr) 3029 (CH=CH),
and piperidine (1 mL) was heated under reflux at
160–180°C for the appropriate time (table 1). After
cooling, water (10–20 mL) was added to the flask.

Efficient microwave irradiation enhanced stereoselective synthesis and antitumor activity
589
1
1649 (C=O); 1H–NMR (DMSO–d6) δ (ppm): 2⋅41 (s, (C=O); H-NMR (DMSO-d6) δ (ppm): 2⋅41 (s, 3H,
3H, CH3), 4⋅72–4⋅73 (m, 1H, =CH2), 4⋅81 (d, 2H, CH3), 5⋅38 (s, 2H, CH2), 7⋅20–8⋅26 (m, 18H, ArH),
NCH2), 5⋅10 (d, 1H, =CH2), 5⋅83–5⋅96 (m, 1H, CH=), 7⋅66 (d, 1H, J = 15 Hz), 7⋅74 (d, 1H, J = 15 Hz); MS
7⋅25–8⋅27 (m, 12H, ArH), 7⋅70 (d, 1H, J = 15 Hz), (EI); m/z 427 (M+, 28). Anal. Calcd. for C31H25NO:
8⋅05 (d, 1H, J = 15 Hz); MS (EI), m/z 422 (M+, 46). C, 87⋅09; H, 5⋅89; N, 3⋅28. Found: C, 87⋅15; H,
Anal. Calcd. for C27H22N2O3: C, 76⋅76; H, 5⋅25; N, 6⋅15; N, 3⋅17.
6⋅63. Found: C, 76⋅83; H, 5⋅51; N, 6⋅52.
2.2m (E)-3-(1-Benzyl-2-p-tolyl-1H-indol-3-yl)-1-
(4-nitrophenyl)-prop-2-en-1-one (3k): Orange solid;
2.2h (E)-3-(1-Allyl-2-p-tolyl-1H-indol-3-yl)-1-bi-
phenyl-4-yl-prop-2-en-1-one (3f): Yellow solid; m.p. 132–134°C; IR νmax (KBr) 3055 (CH=CH),
m.p. 112–114°C; IR νmax (KBr) 3041 (CH=CH), 1649 (C=O); 1H-NMR (DMSO-d6) δ (ppm): 2⋅41 (s,
1643 (C=O); 1H-NMR (DMSO–d6) δ (ppm): 2⋅45 (s, 3H, CH3), 5⋅40 (s, 2H, NCH2), 7⋅33–8⋅35 (m, 17H,
3H, CH3), 4⋅72–4⋅74 (m, 1H, =CH2), 4⋅82 (d, 2H, ArH), 7⋅65 (d, 1H, J = 15⋅6 Hz), 7⋅77 (d, 1H,
NCH2), 5⋅10 (d, 1H, =CH2), 5⋅84–5⋅96 (m, 1H, CH=), J = 15⋅6 Hz); MS (EI), m/z 472 (M+, 46). Anal.
7⋅35–8⋅26 (m, 17H, ArH), 7⋅82 (d, 1H, J = 15 Hz), Calcd. for C31H24N2O3: C, 78⋅79; H, 5⋅12; N, 5⋅93.
8⋅15 (d, 1H, J = 15 Hz); MS (EI), m/z 453 (M+, 49). Found: C, 78⋅86; H, 5⋅38; N, 5⋅82.
Anal. Calcd. for C33H27NO: C, 87⋅38; H, 6⋅00; N,
3⋅09. Found: C, 87⋅45; H, 6⋅26; N, 2⋅98.
2.2n (E)-3-(1-Benzyl-2-p-tolyl-1H-indol-3-yl)-1-
biphenyl-4-yl-prop-2-en-1-one (3l): Pale yellow
2.2i (E)-3-(1-Benzyl-2-phenyl-1H-indol-3-yl)-1-
solid; m.p. 126–128°C; IR νmax (KBr) 3023 (CH=
1
phenyl-prop-2-en-1-one (3g): Pale orange solid; CH), 1649 (C=O); H-NMR (DMSO-d6) δ (ppm):
m.p. 156–158°C; IR νmax (KBr) 3081 (CH=CH), 2⋅41 (s, 3H, CH3), 5⋅39 (s, 2H, NCH2), 7⋅32–8⋅29
1653 (C=O); 1H-NMR (DMSO–d6) δ (ppm): 5⋅39 (s, (m, 22H, ArH), 7⋅82 (d, 1H, J = 15 Hz), 8⋅15 (d, 1H,
2H, NCH2), 6⋅90–8⋅25 (m, 19H, ArH), 7⋅71 (d, 1H, J = 15 Hz); MS (EI), m/z 503 (M+, 20). Anal. Calcd.
J = 15⋅3 Hz), 8⋅06 (d, 1H, J = 15⋅3 Hz); MS (EI), for C37H29NO: C, 88⋅24; H, 5⋅80; N, 2⋅78. Found: C,
m/z 413 (M+, 80). Anal. Calcd. for C30H23NO: C, 88⋅31; H, 6⋅06; N, 2⋅67.
87⋅14; H, 5⋅61; N, 3⋅39. Found: C, 87⋅21; H, 5⋅86;
N, 3⋅53.
2.3 General procedure for the synthesis of Indo-
lylpyrazoline derivatives 4a–l
2.2j (E)-3-(1-Benzyl-2-phenyl-1H-indol-3-yl)-1-(4-
nitrophenyl)-prop-2-en-1-one (3h): Orange crystals;
2.3a Microwave irradiation procedure: A mixture
m.p. 166–168°C; IR νmax (KBr) 3066 (CH=CH),
of substituted (E)-3-(2-aryl-1H-indol-3-yl)-prop-2-
en-1-one 3a–x (1 mmol), phenylhydrazine (1 mmol),
1654 (C=O); 1H–NMR (DMSO–d6) δ (ppm): 5⋅41 (s,
2H, NCH2), 7⋅34–8⋅35 (m, 18H, ArH), 7⋅66 (d, 1H,
ethyl alcohol (2 mL) and acetic acid (0⋅5 mL) in a
J = 15 Hz), 7⋅75 (d, 1H, J = 15 Hz); MS (EI), m/z 458
(M+, 17). Anal. Calcd. for C30H22N2O3: C, 78⋅59; H,
4⋅84; N, 6⋅11. Found: C, 78⋅66; H, 5⋅09; N, 6⋅22.
Pyrex-glass opened vessel was subjected to a mi-
crowave irradiation at 350W in a successive of 30 s
periods (table 2). After cooling to room temperature,
crystals that deposited were filtered off, washed with
ethanol and dried to afford the pure product 4a–l.
2.2k (E)-3-(1-Benzyl-2-phenyl-1H-indol-3-yl)-1-
biphenyl-4-yl-prop-2-en-1-one (3i): Yellow solid;
m.p. 140–142°C; IR νmax (KBr) 3055 (CH=CH),
1653 (C=O); 1H-NMR (DMSO-d6) δ (ppm): 5⋅40 (s,
2H, NCH2), 7⋅31–8⋅30 (m, 23H, ArH), 7⋅83 (d, 1H,
J = 15⋅3 Hz), 8⋅15 (d, 1H, J = 15⋅3 Hz); MS (EI),
m/z 489 (M+, 35). Anal. Calcd. for C36H27NO: C,
88⋅31; H, 5⋅56; N, 2⋅86. Found: C, 88⋅38; H, 5⋅81;
N, 2⋅94.
2.3b Conventional heating procedure: A mixture
of substituted (E)-3-(2-aryl-1H-indol-3-yl)-prop-2-
en-1-one 3a–l (1 mmol), phenylhydrazine (1 mmol)
in ethyl alcohol (10–15 mL) with acetic acid
(0⋅5 mL) was boiled under reflux (table 2). After
cooling to room temperature, crystals that deposited
were filtered off, washed with ethanol and dried to
afford the pure product 4a–l.
2.2l (E)-3-(1-Benzyl-2-p-tolyl-1H-indol-3-yl)-1-
phenyl-prop-2-en-1-one (3j): Yellow solid; m.p.
122–124°C; IR νmax (KBr) 3053 (CH=CH), 1655
2.3c 1-Allyl-3-(2,5-diphenyl-3,4-dihydro-2H-pyrazol-
3-yl)-2-phenyl-1H-indole (4a): Pale yellow crys-

590
Magdy A H Zahran et al
1
tals; m.p. 168–170°C; IR νmax (KBr) 2929 (CH), (CH), 1592 (C=N); H-NMR (DMSO-d6) δ (ppm):
1
1594 (C=N); H-NMR (DMSO-d6) δ (ppm): 3⋅40– 2⋅40 (s, 3H, CH3), 3⋅92–4⋅12 (m, 2H, CH2 pyra-
3⋅49 (m, 1H, CH2 pyrazoline), 3⋅96 (dd, 1H, CH2 zoline), 4⋅63–4⋅81 (m, 1H, CH = allyl; d, 2H,
pyrazoline, J = 12⋅9 Hz), 4⋅64–4⋅70 (m, 1H, CH = NCH2), 5⋅03 (d, 1H, =CH2 allyl), 5⋅43–5⋅58 (m, 1H,
allyl; d, 2H, NCH2), 5⋅10 (d, 1H, =CH2 allyl), 5⋅29 CH pyrazoline), 5⋅82–5⋅89 (m, 1H, CH = allyl),
(dd, 1H, CH pyrazoline, J = 8⋅1 Hz), 5⋅81–5⋅91 (m, 6⋅50–8⋅28 (m, 17H, ArH); MS (EI), m/z 512 (M+,
1H, CH = allyl), 6⋅59–7⋅80 (m, 19H, ArH); MS (EI), 45). Anal. Calcd. for C33H28N4O2: C, 77⋅32; H, 5⋅51;
m/z 453 (M+, 72). Anal. Calcd. for C32H27N3: C, N, 10⋅93. Found: C, 77⋅39; H, 5⋅77; N, 10⋅82.
84⋅74; H, 6⋅00; N, 9⋅26. Found: C, 84⋅82; H, 6⋅26;
N, 9⋅36.
2.3h 1-Allyl-3-(5-biphenyl-4-yl-2-phenyl-3,4-di-
hydro-2H-pyrazol-3-yl)-2-p-tolyl-1H-indole (4f): Pale
2.3d 1-Allyl-3-[5-(4-nitrophenyl)-2-phenyl-3,4-di-
hydro-2H-pyrazol-3-yl]-2-phenyl-1H-indole
yellow crystals; m.p. 170–172°C; IR νmax (KBr)
(4b): 2916 (CH), 1595 (C=N); H-NMR (DMSO-d6) δ
1
Dark red crystals; m.p. 200–202°C; IR νmax (KBr) (ppm): 2⋅41 (s, 3H, CH3), 3⋅42–3⋅51 (m, 1H, CH2
1
2918 (CH), 1592 (C=N); H-NMR (DMSO-d6) δ pyrazoline), 3⋅93–4⋅08 (m, 1H, CH2 pyrazoline),
(ppm): 4⋅00 (dd, 2H, CH2 pyrazoline, J = 13⋅4 Hz), 4⋅64–4⋅76 (m, 1H, CH = allyl; d, 2H, NCH2), 5⋅05
4⋅62–4⋅67 (m, 1H, CH = allyl; d, 2H, NCH2), 5⋅00 (d, 1H, =CH2 allyl), 5⋅30–5⋅42 (m, 1H, CH pyra-
(d, 1H, =CH2 allyl), 5⋅40–5⋅48 (m, 1H, CH pyra- zoline), 5⋅79–5⋅91 (m, 1H, CH = allyl), 6⋅57–7⋅89
zoline), 5⋅80–5⋅89 (m, 1H, CH = allyl), 6⋅65–8⋅28 (m, 22H, ArH); MS (EI), m/z 543 (M+, 100). Anal.
(m, 18H, ArH); MS (EI), m/z 498 (M+, 100). Anal. Calcd. for C39H33N3: C, 86⋅15; H, 6⋅12; N, 7⋅73.
Calcd. for C32H26N4O2: C, 77⋅09; H, 5⋅26; N, 11⋅24. Found: C, 86⋅22; H, 6⋅38; N, 7⋅62.
Found: C, 77⋅16; H, 5⋅51; N, 11⋅26.
2.3i 1-Benzyl-3-(2,5-diphenyl-3,4-dihydro-2H-pyra-
zol-3-yl)-2-phenyl-1H-indole (4g): Pale yellow
2.3e 1-Allyl-3-(5-biphenyl-4-yl-2-phenyl-3,4-
dihydro-2H-pyrazol-3-yl)-2-phenyl-1H-indole (4c): crystals; m.p. 162–164°C; IR νmax (KBr) 2920 (CH),
1
Yale yellow crystals; m.p. 192–194°C; IR νmax 1593 (C=N); H-NMR (DMSO-d6) δ (ppm): 4⋅03–
1
(KBr) 2976 (CH), 1595 (C=N); H-NMR (DMSO- 4⋅92 (m, 2H, CH2 pyrazoline), 5⋅31 (s, 2H, NCH2),
d6) δ (ppm): 4⋅10 (dd, 2H, CH2 pyrazoline, 5⋅34–5⋅35 (m, 1H, CH pyrazoline), 6⋅61–7⋅79 (m,
J = 13⋅1 Hz), 4⋅64–4⋅70 (m, 1H, CH = allyl; d, 2H, 24H, ArH); MS (EI), m/z 503 (M+, 65). Anal. Calcd.
NCH2), 5⋅10 (d, 1H, =CH2 allyl), 5⋅28–5⋅35 (m, 1H, for C36H29N3: C, 85⋅85; H, 5⋅80; N, 8⋅34. Found: C,
CH pyrazoline), 5⋅82–5⋅91 (m, 1H, CH = allyl), 85⋅92; H, 6⋅06; N, 8⋅43.
6⋅61–7⋅89 (m, 23H, ArH); MS (EI), m/z 529 (M+,
85). Anal. Calcd. for C38H31N3: C, 86⋅17; H, 5⋅90; N, 2.3j 1-Benzyl-3-[5-(4-nitrophenyl)-2-phenyl-3,4-
7⋅93. Found: C, 86⋅25; H, 6⋅10; N, 8⋅04.
dihydro-2H-pyrazol-3-yl]-2-phenyl-1H-indole (4h):
Dark red crystals; m.p. 184–186°C; IR νmax (KBr)
2923 (CH), 1592 (C=N); H-NMR (DMSO-d6) δ
1
2.3f 1-Allyl-3-(2,5-diphenyl-3,4-dihydro-2H-pyra-
zol-3-yl)-2-p-tolyl-1H-indole (4d): Pale yellow (ppm): 3⋅97–4⋅07 (m, 2H, CH2 pyrazoline), 5⋅30 (s,
crystals; m.p. 160–162°C; IR νmax (KBr) 2915 (CH), 2H, NCH2), 5⋅50–5⋅52 (m, 1H, CH pyrazoline),
1
1593 (C=N); H-NMR (DMSO-d6) δ (ppm): 2⋅40 (s, 6⋅63–8⋅28 (m, 23H, ArH); MS (EI), m/z 548 (M+,
3H, CH3), 3⋅41–3⋅52 (m, 1H, CH2 pyrazoline), 3⋅88– 38). Anal. Calcd. for C36H28N4O2: C, 78⋅81; H, 5⋅14;
4⋅07 (m, 1H, CH2 pyrazoline), 4⋅63–4⋅69 (m, 1H, N, 10⋅21. Found: C, 78⋅87; H, 5⋅39; N, 10⋅31.
CH = allyl; d, 2H, NCH2), 5⋅04 (d, 1H, =CH2 allyl),
5⋅24–5⋅39 (m, 1H, CH pyrazoline), 5⋅81–5⋅90 (m, 2.3k 1-Benzyl-3-(5-biphenyl-4-yl-2-phenyl-3,4-di-
1H, CH = allyl), 6⋅58–7⋅80 (m, 18H, ArH); MS (EI), hydro-2H-pyrazol-3-yl)-2-phenyl-1H-indole (4i): Pale
m/z 467 (M+, 23). Anal. Calcd. for C33H29N3: C, yellow solid; m.p. 168–170°C; IR νmax (KBr) 2916
1
84⋅76; H, 6⋅25; N, 8⋅99. Found: C, 84⋅83; H, 6⋅51; (CH), 1595 (C=N); H-NMR (DMSO-d6) δ (ppm):
N, 8⋅88.
4⋅07–4⋅96 (m, 2H, CH2 pyrazoline), 5⋅32 (s, 2H,
NCH2), 5⋅38–5⋅39 (m, 1H, CH pyrazoline), 6⋅63–
7⋅87 (m, 28H, ArH); MS (EI), m/z 579 (M+, 43).
2.3g 1-Allyl-3-[5-(4-nitrophenyl)-2-phenyl-3,4-di-
hydro-2H-pyrazol-3-yl]-2-p-tolyl-1H-indole
(4e): Anal. Calcd. for C42H33N3: C, 87⋅01; H, 5⋅74; N,
Red crystals; m.p. 198–200°C; IR νmax (KBr) 2916 7⋅25. Found: C, 87⋅10; H, 5⋅80; N, 7⋅36.

Efficient microwave irradiation enhanced stereoselective synthesis and antitumor activity
591
2.3l 1-Benzyl-3-(2,5-diphenyl-3,4-dihydro-2H-pyra- drops of piperidine under microwave irradiation
zol-3-yl)-2-p-tolyl-1H-indole (4j): Pale yellow (scheme 1). The reaction proceeded within few min-
crystals; m.p. 160–162°C; IR νmax (KBr) 2918 (CH), utes (3–10 min) with successive period of 30 sec. at
1
1594 (C=N); H-NMR (DMSO-d6) δ (ppm): 2⋅38 (s, 750 W to avoid overheating of the solvent to afford
3H, CH3), 3⋅46–3⋅59 (m, 1H, CH2 pyrazoline), 3⋅97 substituted (E)-3-(2-aryl-1H-indol-3-yl)-prop-2-en-
(dd, 1H, CH2 pyrazoline, J = 12⋅9 Hz), 5⋅31 (s, 2H, 1-one derivatives 3a–l in moderate to good yields
NCH2), 5⋅36–5⋅44 (m, 1H, CH pyrazoline), 6⋅62– compared with the conventional method under the
7⋅79 (m, 23H, ArH); MS (EI), m/z 517 (M+, 22). same reaction condition (table 1).
Anal. Calcd. for C37H31N3: C, 85⋅85; H, 6⋅04; N,
8⋅12. Found: C, 85⋅92; H, 6⋅30; N, 8⋅01.
1H-NMR spectra revealed that the indolylchalcone
fragments 3a–l were existed in trans configuration
due to appearance of the CH=CH group as an AB
system as two doublets at δ = 7⋅51 and 8⋅34 ppm
2.3m 1-Benzyl-3-[5-(4-nitrophenyl)-2-phenyl-3,4-
dihydro-2H-pyrazol-3-yl]-2-p-tolyl-1H-indole (4k) with the coupling constant J = 15⋅3 Hz25 and the
Orange crystals; m.p. 184–186°C; IR νmax (KBr) aromatic protons appeared as complex multiplets at
1
2917 (CH), 1594 (C=N); H-NMR (DMSO-d6) δ δ 6⋅90–8⋅52 ppm. IR spectra of compounds 3a–l
(ppm): 2⋅37 (s, 3H, CH3), 3⋅50–3⋅59 (m, 1H, CH2 showed the appearance of absorption bands at the
pyrazoline), 4⋅01 (dd, 1H, CH2 pyrazoline, region 1655–1643 cm–1 corresponding to conjugated
J = 13⋅2 Hz), 5⋅33–5⋅51 (m, 1H, CH pyrazoline), (C=O) and absorption bands at the region 3081–
5⋅39 (s, 2H, NCH2), 6⋅67–8⋅29 (m, 22H, ArH); MS 3023 cm–1 corresponding to (CH=CH). All the obtai-
(EI), m/z 562 (M+, 100). Anal. Calcd. for ned products 3a–l both under microwave irradiation
C37H30N4O2: C, 78⋅98; H, 5⋅37; N, 9⋅96. Found: C, and conventional heating were existed in trans
79⋅05; H, 5⋅63; N, 9⋅85.
configuration which showed a clear evidence for the
stereoselective of the indolylchalcones under the
given condition. Moreover, the X-ray crystallo-
2.3n 1-Benzyl-3-(5-biphenyl-4-yl-2-phenyl-3,4-di-
hydro-2H-pyrazol-3-yl)-2-p-tolyl-1H-indole
(4l): graphic analysis26 of the selected indolylchalcone 3f
Pale yellow crystals; m.p. 182–184°C; IR νmax (KBr) confirmed the trans configuration (figure 1) as well
1
2943 (CH), 1593 (C=N); H-NMR (DMSO-d6) δ as it’s 1H-NMR spectral data.
(ppm): 2⋅38 (s, 3H, CH3), 3⋅47–3⋅55 (m, 1H, CH2
Attempts to synthesize substituted 3-(2-aryl-1H-
pyrazoline), 3⋅99 (dd, 1H, CH2 pyrazoline, indol-3-yl)-prop-2-en-1-one derivatives 3a–l in ethyl
J = 12⋅9 Hz), 5⋅31 (s, 2H, NCH2), 5⋅31–5⋅36 (m, 1H, alcohol with few drops of piperidine and in aqueous
CH pyrazoline), 6⋅60–7⋅89 (m, 27H, ArH); MS (EI), ethanolic potassium hydroxide either under micro-
m/z 593 (M+, 56). Anal. Calcd. for C43H35N3: C, wave irradiation or conventional heating revealed
86⋅98; H, 5⋅94; N, 7⋅08. Found: C, 87⋅05; H, 6⋅20; that the reactions took longer time and afforded poor
N, 6⋅97.
yield.
In comparison with the reported methods,27–30 the
synthesis of the indolylchalcones in ethylene glycol
and piperidine turned out to be an efficient media in
terms of reaction times, manipulation and yields
under microwave irradiation condition.
3. Results and discussion
3.1 Synthesis and characterization
Several pyrazoline derivatives possess important
pharmacological activities and some indolylpyrazo-
lines showed moderate to good activity as cycloxy-
genese-2 (COX-2) and lipoxygenase (LOX)
inhibitors.31 Therefore, as a part of our effort to
explore a new anticancer agent, new series of indo-
lylpyrazolines was synthesized and evaluated for
their antitumor activity.
Thus, reacting (E)-3-(2-aryl-1H-indol-3-yl)-prop-
2-en-1-one derivatives 3a–l with phenylhydrazine in
absolute ethanol and few drops of glacial acetic acid
under microwave irradiation at 350 W with success-
Indolylchalcones were reported as antitumor agents,
immunosuppressant and therapeutic agents for auto-
immune diseases.24 We have previously reported the
synthesis of a series of indolylchalcones with prom-
ising in vitro antitumor activity.22b Thus, in the pre-
sent study, an extension of research on the design,
synthesis and investigation of the cytotoxic effect of
a new series of indolylchalcone derivatives against
human Hep-G2 was considered.
2-Aryl-1H-indole-3-carbaldehyde derivatives 1
underwent Claisen–Schmidt condensation with dif-
ferent acetophenones 2 in ethylene glycol and few

592
Magdy A H Zahran et al
1a–d
1a
Ar
R
2a–c
Ar'
C6H5
Allyl
2a
2b
2c
C6H5
1b
4-MeC6H4
C6H5
Allyl
3-NO2C6H4
4-PhC6H4
1c
Benzyl
Benzyl
1d
4-MeC6H4
Scheme 1. Synthesis of indolylchalcones 3a–l and indolylpyrazolines 4a–l.
All the indolylpyrazolines 4a–l have a chiral cen-
ter at 5th position, usually the hydrogen on the
chiral carbon atom interacted with the hydrogens ad-
jacent to the chiral center. If the carbon adjacent to
the chiral center has one hydrogen atom, then the re-
sulting two enantiomers will have these two hydro-
gen atoms in cis or trans position and can easily be
1
distinguished by H-NMR spectral analysis. But in
this case, the carbon atom next to the chiral center
has two hydrogens and would not be distinguished
as cis or trans forms and could not be distinguished
by 1H-NMR spectral data.31
1H-NMR spectra of 4a–l fragments showed disap-
pearance of the doublet of doublet at the average
value 7⋅51 and 8⋅34 ppm and the appearance of the
pyrazoline methine proton at 5⋅45 ppm as well as the
methylene protons at 3⋅82 ppm as doublet of doublet
and/or as multiplet.
IR spectra of indolylpyrazolines 4a–l showed no
absorption in the region of 1655–1643 cm–1 indicat-
ing the disappearance of the conjugated keto group
(C=O), the appearance of stretching vibration in the
region of 1595–1592 cm–1 due to (C=N) and at
2978–2907 cm–1 corresponding to the methine (CH)
and the methylene (CH2) of pyrazoline ring. The
values of the elemental analyses of compounds 3a–l
and 4a–l were found to be in good agreement
( 0⋅3%) with the calculated values.
Figure 1. X-ray crystal structure of indolylchalcone
(3f).
sive period of 30 s, the corresponding indolylpyra-
zoline analogs 4a–l were obtained (scheme 1). The
yields of the indolylpyrazolins 4a–l under micro-
wave irradiation condition were high and quantita-
tive, moreover, the reaction time was also shortened
compared with the conventional heating (table 2).
Trials to synthesis indolylpyrazolines 4a–l under
reflux in glacial acetic acid revealed that there are
many by-products were formed and a poor yield of
the indolylpyrazoline derivatives was isolated.
All the indolylchalcones 3a–l and their pyrazoline
analogs 4a–l were obtained both by the microwave

Efficient microwave irradiation enhanced stereoselective synthesis and antitumor activity
593
Table 1. Comparative study for the synthesis of indolylchalcones 3a–l.
b
Thermal
Microwave
a
Time (min) Yield (%) Time (min) Yield (%)
a
Compound Aldehyde Acetophenone
3a
3b
3c
3d
3e
3f
3g
3h
3i
1a
1a
1a
1b
1b
1b
1c
1c
1c
1d
1d
1d
2a
2b
2c
2a
2b
2c
2a
2b
2c
2a
2b
2c
25
15
30
25
25
30
25
15
20
30
25
30
79
84
85
80
82
81
82
82
76
78
81
82
10
4
88
95
93
89
92
91
90
93
87
90
91
90
6
8
3
6
8
3
8
3j
3k
3l
10
4
8
a
b
Isolated yield. Irradiation power was 750 W.
Table 2. Comparative study for the synthesis of indolylpyrazolines 4a–l.
b
Thermal
Microwave
a
Yield (%)
a
Yield (%)
Compound
Time (h)
Time (min)
4a
4b
4c
4d
4e
4f
4g
4h
4i
3
71
76
75
79
78
78
77
85
75
77
79
78
10
5
88
89
89
89
91
92
91
92
89
90
85
90
4
2.5
2.5
2.5
2.5
2.5
3
8
8
5
10
10
4
4
8
4j
4k
4l
2
8
3
4
2
10
a
b
Isolated yield. All the compounds were irradiated at 350 W.
irradiation and conventional heating; irrespective of lylpyrazoline 4e exhibited the highest cytotoxic
these reaction conditions the IR spectra of each effect with the lowest IC50 value of 5⋅09 μM, while
product are identical.
the compounds 4h, 4b, and 4k, demonstrated a
moderately high inhibition in the cell viability as
concluded from the IC50 values of 32⋅75, 20⋅51 and
26⋅58 μM respectively, which revealed a moderate
3.2 Biological activity
The cytotoxicity of all the synthesized compounds anti-tumor activity against hepatic carcinoma as
3a–l and 4a–l was screened for their biological ac- shown in table 3. On the other hand, the rest of the
tivities in vitro against Human hepatocellular carci- compounds exhibited no cytotoxic effect due to their
noma cell line (Hep-G2) using the MTT Cell high IC50 values (> 50 μM).
viability assay.32 Data were expressed as the per-
centage of relative viability compared with the
untreated cells, the vehicle control and the cytotox-
icity indicated by <100% relative viability. The rela-
tive inhibitory ratios (%) against Human Hep-G2
were listed in table 3.
4. Conclusions
In search of potentially active molecules containing
indole moiety and their pyrazoline analogs, a series
of new derivatives was synthesized with an efficient
microwave irradiation protocol and their antitumor
activity analysed. This protocol offers several
From the reported results in table 3 it was clear
that, the treatment of Hep-G2 cells with the indo-

594
Magdy A H Zahran et al
Table 3. In vitro cytotoxic activity of indolylchalcones 3a–l and indolylpyrazolines 4a–l
against Hep-G2 by MTT assay.
Concentration (μM) % of cell viability (Hep-G2 cells)
Compound
12⋅5 μM
25 μM
50 μM
100 μM
IC50
3a
3b
3c
3d
3e
3f
3g
3h
3i
107⋅48
70⋅15
96⋅5
97⋅73
61⋅22
82⋅54
99⋅41
60⋅43
68⋅83
88⋅762
83⋅42
93⋅4
100⋅1
64⋅87
72⋅76
82⋅36
42⋅2
91⋅11
74⋅43
32⋅43
74⋅19
102⋅33
42⋅55
81⋅68
76⋅998
49⋅34
87⋅71
78⋅78
47⋅23
72⋅34
87⋅77
53⋅22
56⋅02
78⋅23
77⋅91
88⋅44
93⋅25
51⋅89
59⋅32
74⋅43
29⋅435
78⋅78
61⋅41
19⋅18
62⋅94
91⋅05
31⋅72
73⋅34
69⋅68
36⋅8
63⋅44
36⋅66
58⋅34
81⋅35
40⋅45
51⋅32
63⋅6
61⋅84
78⋅76
86⋅87
46⋅66
43⋅22
66⋅121
14⋅76
61⋅344
56⋅56
11⋅09
54⋅32
85⋅76
19⋅1
121⋅59
57⋅23
115⋅45
226⋅48
65⋅98
101⋅34
69⋅85
79⋅41
93⋅33
98⋅451
100⋅07
109⋅3
71⋅1
93⋅67
138⋅03
128⋅16
223⋅32
251⋅69
78⋅60
80⋅25
139⋅94
20⋅51
123⋅46
111⋅94
5⋅09
105⋅82
273⋅56
32⋅75
3j
3k
3l
80⋅8
4a
4b
4c
4d
4e
4f
4g
4h
4i
99⋅525
62⋅29
99⋅9
83⋅98
59⋅26
84⋅63
101⋅77
76⋅1
100⋅81
92⋅8
58⋅99
96⋅5
50⋅11
56⋅54
21⋅1
95⋅22
4j
4k
4l
112⋅15
26⋅58
183⋅22
81⋅675
72⋅32
Kontoyianni M, Petrey M E, Sabatakos G, Roesgen
J T, Richardson E and Demuth T P 2006 Bioorg.
Med. Chem. Lett. 16 5659
advantages such as mild reaction conditions, short
reaction times, easy isolation and good yields. The
indolylchalcones and their pyrazoline analogs
showed high cytotoxic effect with the lowest IC50
for indolylpyrazoline 4e while the compounds 4h,
4b and 4k, showed a moderately high inhibition
against human hepatocellular carcinoma cell line
(Hep-G2).
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