Synthesis and antitumor activity of novel pyrazolylenaminone and bis(pyrazolyl)ketones via hydrazonoyl halides

Article abstract of DOI:10.1002/jhet.113

(Chemical Equation Presented) 3-Acetyl-4-benzoyl-1,5-diphenylpyrazole reacts with DMF-DMA to give the novel enaminone 2. The reaction of the latter with various hydrazonoyl halides afforded regioselectively the respective substituted (3-pyrazolyl)(4-pyraz

Full text of DOI:10.1002/jhet.113

548
Synthesis and Antitumor Activity of Novel Pyrazolylenaminone
and Bis(Pyrazolyl)ketones via Hydrazonoyl Halides
Vol 46
Ahmad S. Shawali,a* Sherif M. Sherif,a Mahmoud M. El-Merzabani,b
and Manal A. A. Darwisha
aDepartment of Chemistry, Faculty of Science, University of Cairo, Giza, Egypt
bDepartment of Experimental Oncology, National Cancer Institute, University of Cairo,
Giza, Egypt
*E-mail: as_shawali@mail.com
Received November 12, 2008
DOI 10.1002/jhet.113
Published online 7 May 2009 in Wiley InterScience (www.interscience.wiley.com).
3-Acetyl-4-benzoyl-1,5-diphenylpyrazole reacts with DMF-DMA to give the novel enaminone 2. The
reaction of the latter with various hydrazonoyl halides afforded regioselectively the respective substi-
tuted (3-pyrazolyl)(4-pyrazolyl)ketones 4 in good over all yield. The preliminary screening for the anti-
tumor activity of the synthesized compounds 2 and 4a-g against human breast cancer cell line (MCF-7)
revealed that both compounds 2 and 4b have high-antitumor activity. SAR is discussed.
J. Heterocyclic Chem., 46, 548 (2009).
INTRODUCTION
showed two bands at t 1692 and 1659 cmꢀ1 assignable
1
to two C¼¼O groups. Its H NMR (DMSO-d6) displayed
Within the past 10 years, we have been engaged on
the utility of hydrazonoyl halides for synthesis of vari-
ous heterocyclic systems [1–10]. Furthermore, literature
cites many reports on valuable biological activity of var-
ious pyrazole derivatives [11–21]. On the basis of these
facts, it was thought interesting to explore the utility of
hydrazonoyl halides for synthesis of the hitherto unre-
ported (3-pyrazolyl)(4-pyrazolyl) ketones and evaluate
their antitumor activity against human breast cell line
MCF-7. For this purpose, we investigated the reactions
of a series of hydrazonoyl halides 3 with the hitherto
unreported 3-pyrazolyl-enaminone 2 (Scheme 1). We
carried out such reactions to explore also their regio-
chemistry as they can lead to (3-pyrazolyl)(4-pyrazolyl)
ketones 4 and/or their isomers (3-pyrazolyl)(5-pyrazolyl)
ketones 5 (Scheme 1).
signals at d 3.34 (s, 3H, CH3), 7.15–7.80 (m, 15H,
ArH). Reaction of compound 1 with dimethylforma-
mide-dimethylacetal (DMF-DMA) in refluxing toluene
furnished the required new enaminone 2. The IR spec-
trum of the latter showed two carbonyl absorption bands
1
at 1678 and 1649 cmꢀ1. Its H NMR spectrum revealed,
in addition to the aromatic protons multiplet, two dou-
blet signals at d 5.84 and 7.62 with J ¼ 19 Hz assigna-
ble to the two olefinic protons and two methyl protons
singlet signals at d 2.86 and 3.09. This finding indicates
that this enaminone 2 exists in the indicated trans-con-
figuration (Scheme 1).
Reaction of 2 with each of the hydrazonoyl halides
3a-g in dioxane in the presence of triethylamine gave,
in each case, one isolable product as evidenced by TLC
analysis. Both mass spectra and elemental analysis data
of the isolated products were consistent with either one
of the two isomeric structures 4 or 5 (Scheme 1). On
RESULTS AND DISCUSSION
1
the basis of their H NMR spectra, the isolated products
were assigned structure 4 and the isomeric structure 5
was discarded. This is because their 1H NMR spectra
revealed, in each case, a singlet signal for the pyrazole
ring proton in the region d 9.20–9.33 assignable to pyr-
azole-5H. Literature reports [22,23] indicate that the H
NMR spectra of 5- and 4-unsubstituted pyrazoles exhibit
the characteristic singlet signals of 5-CH and 4-CH
The hitherto unreported 3-acetyl-4-benzoyl-1,5-diphe-
nylpyrazole 1 was prepared via reaction of N-phenyl 2-
oxopropanehydrazonoyl chloride 3a with dibenzoylme-
thane in ethanol in the presence of sodium ethoxide. Its
structure was confirmed by its spectra (IR, MS, 1H
NMR and 13C NMR) and its elemental analysis (see
Experimental section). For example, its IR spectrum
1
C
V
2009 HeteroCorporation

May 2009
Synthesis and Antitumor Activity of Novel Pyrazolylenaminone and
Bis(pyrazolyl)ketones via Hydrazonoyl Halides
549
Scheme 1
dipolar cycloaddition of the nitrilimine intermediate A,
generated in situ by base-catalyzed dehydrohalogena-
tion of the hydrazonoyl halide 3, to the carbon–carbon
double bond of the enaminone 2 to afford the nonisol-
able cycloadduct intrermediate B. The latter then under-
goes in situ elimination of dimethylamine to yield the
corresponding pyrazole derivative 4 as end product
(Scheme 1).
Antitumor screening. The cytotoxic effects of the
new enaminone 2 and bis(pyrazolyl) ketones 4a-g
against human breast cell line MCF-7 were evaluated at
the National Institute of Cancer, Cairo, Egypt. Doxoru-
bicin was used as a reference to evaluate the potency of
the tested compounds. Five different concentrations of
each compound and the reference were used in such
screening tests and determination of IC50 values. The
results are given in Table 1. As shown in Table 1, com-
pound 2 has unpredictable antitumor activity against
MCF-7 cell line as its IC50 value is 0.87 lg/mL which
is close to that of the reference doxotrubicin (IC50
¼
0.70). Compounds 4a-g showed, however, less activity
than that of compound 2. This finding indicates that sub-
stitution of N,N-dimethylaminovinyl group in 2 by the
1,3-disubstituted pyrazol-4-yl moiety in 4 decreased the
activity. Such a decrease might be due to the fact that
the pyrazolyl group is more complex than N,N-dimethy-
laminovinyl group. This complexity limits penetration of
compounds 4 into the cell or interferes with their metab-
olism or both and as a result, the antitumor activity
decreases. Furthermore, a comparison of the IC50 values
of compounds 4a-g indicates further that their activity
depends on the nature of the R group. The order of ac-
tivity is: EtOCO > C6H5 > CH3CO > C6H5NHCO >
C6H5CO ¼ 2-thenoyl > 2-naphthoyl.
protons at d 8.35 and 7.30, respectively. Furthermore,
spectral simulation by ACD/H NMR Predictor (v.6.12)
for 5- and 4-unsubstituted pyrazoles showed the 5-H and
4-H signals at d 8.30 and 7.63, respectively. On the basis
of such data, it is not unreasonable to conclude that the
studied reactions are completely regioselective and the
structure of the isolated products is 4 and not 5. This con-
clusion is consistent with literature reports that indicate
that reactions of hydrazonoyl halides with various enami-
nones are regioselective and lead to the formation of the
respective 5-unsubtituted pyrazole derivatives [8].
In conclusion, a facile synthesis of each of both the
novel enaminone 2 and bis(pyrazolyl)ketones 4a-g is
demonstrated. Evaluation of the antitumor activity of
these new compounds revealed that compounds 2 (IC50
¼ 0.87 lg/mL) and 4b (IC50 ¼ 1.81 lg/mL) showed
good inhibitory activity of human breast cancer cell
(MCF-7).
To account for the formation of products 4, it is sug-
gested that the reaction starts with a regioselective 1,3-
Table I
In vitro cytotoxic activity of the new compounds 2 and 4a-g.
Surviving fraction ꢁ 103, conc. (lg/mL)
Surviving fraction ꢁ 103, conc. (lg/mL)
No.
0.0
1.0
2.5
5.0
10.0
IC50
No.
0.0
1.0
2.5
5.0
10.0
IC50
2
1000
1000
1000
1000
1000
444
904
674
828
832
168
418
471
566
501
760
234
197
292
218
700
233
223
222
294
0.87
2.21
1.81
2.68
2.42
4e
4f
4g
Doxa
1000
1000
1000
1000
836
900
716
417
554
671
523
260
240
232
240
261
245
2.68
2.89
2.08
0.70
4a
4b
4c
4d
255
232
267
a Doxotrobicin, an antitumor reference.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

550
A. S. Shawali, S. M. Sherif, M. M. El-Merzabani, and M. A. A. Darwish
Vol 46
EXPERIMENTAL
yellow crystals (yield 75%), mp 150–152ꢂC; IR (KBr) m 1693,
1655, 1620 (3C¼¼O) cmꢀ1
;
1H NMR (DMSO-d6) d 2.57 (s,
All melting points are uncorrected. IR spectra were recorded
in KBr using Pye Unicam SP-1000 Spectrophotometer. 1H
NMR spectra were recorded in DCCl3 and DMSO-d6 using a
Varian Em-200 MHz Spectrometer, and TMS as internal refer-
ence. Mass spectra were recorded on AEI MS 30 mass spec-
trometer operating at 70 eV. Elemental analyses were carried
out at the Microanalytical Centre of Cairo University. The
hydrazonoyl halides 3 were prepared following literature pro-
cedures [24].
3-Acetyl-4-benzoyl-1,5-diphenyl-1H-pyrazole (1). To an
ethanolic sodium ethoxide solution, prepared by dissolving
sodium metal (0.12 g, 0.005 g-atom) and absolute ethanol
(20 mL), was added dibenzoylmethane (1.12 g, 5 mmol). To
the resulting solution N-phenyl 2-oxopropanehydrazonoyl chlo-
ride 3a (5 mmol) was added to the solution portionwise while
stirring the reaction mixture at room temperature. After com-
plete addition, the reaction mixture was stirred for further 3 h
during which the hydrazonoyl chloride dissolved and a new
solid precipitated. The latter was filtered off, washed and crys-
tallized from ethanol to give 3-acetyl-4-benzoyl-1,5-diphenyl-
1H-pyrazole (1) as yellow crystals (yield 80%), mp 170–
171ꢂC. IR (KBr) m 1692, 1659 (2C¼¼O); 1H NMR (DMSO-
d6): d 3.34 (s, 3H, CH3), 7.15–7.80 (m, 15H, ArH); 13C NMR
(DMSO-d6): d 26.3, 120.8, 125.8, 127.5, 128.4, 128.6, 128.9,
129.1, 129.3, 129.5, 133.3, 137.3, 138.5, 143.2, 148.5, 177.8,
190.9, 192.2; ms: m/z (%): 367 (Mþ þ 1, 25), 366 (Mþ, 54),
323 (20), 289 (100), 247 (20), 180 (13), 77 (64). Anal. Calcd.
for C24H18N2O2 (366.42): C, 78.67; H, 4.95; N, 7.65%. Found:
C, 78.37; H, 5.06; N, 7.66%.
3H, CH3), 7.24–7.93 (m, 20H, ArAH), 9.15 (s, 1H, pyrazole);
ms: m/z (%) 537 (Mþ þ 1, 25), 536 (Mþ, 38), 493 (23), 417
(29), 180 (17), 105 (100). Anal. Calcd. for C34H24N4O3
(536.58): C, 76.11; H, 4.51; N, 10.44%. Found: C, 76.41; H,
4.85; N, 10.77%.
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1-phenyl-3-ethoxy-
carbonyl-pyrazol-4-yl)ketone (4b). This compound was
obtained as pale orange crystals (yield 68%), mp 105–107ꢂC;
IR (KBr) m 1725, 1663, 1615 (3C¼¼O) cmꢀ1
;
1H NMR
(DMSO-d6) d 1.18 (t, 3H, J ¼ 7.5 Hz, CH3), 4.14 (q, 2H, J ¼
7.5 Hz, CH2), 7.21–7.90 (m, 20H, ArAH), 9.2 (s, 1H, pyraz-
ole); ms: m/z (%) 567 (Mþ þ 1, 32), 566 (Mþ, 74), 493 (82),
417 (74), 316 (42), 260 (42), 215 (22), 180 (25), 77 (100).
Anal. Calcd. for C35H26N4O4 (566.61): C, 74.19; H, 4.63; N,
9.89%. Found: C, 73.98; H, 4.78; N, 10.11%.
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1-phenyl-3-benzoyl-
pyrazol-4-yl)ketone (4c). This compound was obtained as pale
brown crystals (yield 70%), mp 110–112ꢂC; IR (KBr) m 1690,
1663, 1620 (3C¼¼O) cmꢀ1
;
1H NMR (DMSO-d6) d 7.1–7.97
(m, 25H, ArAH), 9.33 (s, 1H, pyrazole); ms: m/z (%) 599
(Mþ þ 1, 21), 598 (Mþ, 34), 493 (62), 404 (74), 351 (24),
316 (72), 105 (100). Anal. Calcd. for C39H26N4O3 (598.65): C,
78.25; H, 4.38; N, 9.36%. Found: C, 78.46; H, 4.20; N,
9.55%.
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1-phenyl-3-phenyl-
aminocarbonyl-pyrazol-4-yl)ketone (4d). This compound was
obtained as yellow crystals (yield 66%), mp 120–122ꢂC; IR
(KBr) m 3236 (NH), 1699, 1664, 1618 (3C¼¼O) cmꢀ1
;
1H
NMR (DMSO-d6) d 7.19–8.00 (m, 25H, ArAH), 9.25 (s, 1H,
pyrazole), 10.8 (s, 1H, NH, D2O-exchangeable); ms: m/z (%)
614 (Mþ þ 1, 10), 613 (Mþ, 37), 521 (46), 260 (8), 222 (9),
180 (10), 105 (100). Anal. Calcd. for C39H27N5O3 (613.66): C,
76.33; H, 4.43; N, 11.41%. Found: C, 76.16; H, 4.58; N,
11.27%.
3-[3-(N,N-Dimethylamino)acryloyl]-4-benzoyl-1,5-diphenyl-
1H-pyrazole (2). A mixture of 3-acetyl-4-benzoyl-1,5-di-
phenyl-1H-pyrazole (1) (3.66 g, 10 mmol) and dimethylforma-
mide-dimethylacetal (DMF-DMA) (2.4 g, 20 mmol) was
refluxed for 5 h then left to cool. To the cold mixture was
added ether. The resulting yellow solid was filtered, washed
with ether, dried and finally crystallized from ethanol to afford
the enaminone 2. This compound was obtained as yellow crys-
tals (yield 70 %), mp 190–192ꢂC; IR (KBr) m 1678, 1649
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1-phenyl-3-thenoyl-
pyrazol-4-yl)ketone (4e). This compound was obtained as
white buff solid (yield 65%), mp 118–120ꢂC; IR (KBr) m
1694, 1658, 1615 (3C¼¼O) cmꢀ1
;
1H NMR (DMSO-d6) d,
(2C¼¼O) cmꢀ1
;
1H NMR (DMSO-d6): d 2.86 (s, 3H, CH3),
7.15–8.14 (m, 23H, ArAH, Het-H), 9.29 (s, 1H, pyrazole); ms:
m/z (%) 605 (Mþ þ 1, 15), 604 (Mþ, 32), 499 (54), 281 (13),
111 (100), 77 (12.5). Anal. Calcd. for C37H24N4O3S (604.68):
C, 73.49; H, 4.00; N, 9.27; S, 5.30%. Found: C, 73.67; H,
3.86; N, 9.10; S, 5.18%.
3.09 (s, 3H, CH3), 5.84 (d, 1H, J ¼ 19 Hz, ACOACH¼¼),
7.15–7.55 (m, 15H ArAH), 7.62 (d, 1H, J ¼ 19 Hz,
¼¼CHANA); ms: m/z (%): 422 (Mþ þ 1, 11), 421 (Mþ, 12),
404 (50), 316 (80), 180 (23), 98 (78), 77 (100). Anal. Calcd.
for C27H23N3O2 (421.49): C, 76.94; H, 5.50; N, 9.97%. Found:
C, 76.70; H, 5.32; N, 10.14%.
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1-phenyl-3-substi-
tuted-pyrazol-4-yl)ketones (4a-g): General procedure. To a
stirred solution of the appropriate hydrazonoyl halide
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1-phenyl-3-(2-naph-
thoyl)-pyrazol-4-yl)ketone (4f). This compound was obtained
as white buff crystals (yield 68%), mp 100–102ꢂC; IR (KBr) m
1688, 1662, 1616 (3C¼¼O) cmꢀ1
;
1H NMR (DMSO-d6) d
3
7.01–8.18 (m, 27H, ArAH), 9.30 (s, 1H, pyrazole); ms: m/z
(%) 649 (Mþ þ 1, 71), 648 (Mþ, 81), 544 (71), 494 (31), 127
(100). Anal. Calcd. for C43H28N4O3 (648.71): C, 79.61; H,
4.35; N, 8.64%. Found: C, 79.47; H, 4.50; N, 8.40%.
(1 mmol) and the enaminone 2 (0.42 g, 1 mmol) in dry diox-
ane (50 mL), was added triethylamine (0.5 mL) and the mix-
ture was refluxed for 12 h. The precipitated triethylamine
hydrochloride was filtered off, and the filtrate was evaporated
under reduced pressure. The residue was triturated with etha-
nol. The solid product so formed was filtrated, washed with
water, and dried. Crystallization from ethanol afforded the cor-
responding pyrazole derivatives 4. The physical constants of
the products 4a-g are listed in the subsequent sections.
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1,3-diphenyl-py-razol-
4-yl)ketone (4g). This compound was obtained as pale yellow
crystals (yield 72%), mp 130–132ꢂC; IR (KBr) m 1668, 1647
(2C¼¼O) cmꢀ1
;
1H NMR (DMSO-d6) d 7.16–7.74 (m, 25H,
ArAH), 9.23 (s, 1H, pyrazole); ms: m/z (%) 571 (Mþ þ 1,
49), 570 (Mþ, 100), 405 (93), 317 (51), 247 (42), 84 (38).
Anal. Calcd. for C38H26N4O2 (570.64): C, 79.98; H, 4.59; N,
9.82%. Found: C, 80.14; H, 4.79; N, 9.68%.
(4-Benzoyl-1,5-diphenyl-pyrazol-3-yl)-(1-phenyl-3-acetyl-
pyrazol-4-yl)ketone (4a). This compound was obtained as pale
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

May 2009
Synthesis and Antitumor Activity of Novel Pyrazolylenaminone and
Bis(pyrazolyl)ketones via Hydrazonoyl Halides
551
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Pharmacology. Cytotoxic activity against human breast
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mine-B stain (SRB). Cells were plated in 96-multiwill plate
(104 cells/well) for 24 h before treatment with the test com-
pound to allow attachment of cell to the wall of the plate, dif-
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and 10 lg/mL) were added to the cell monolayer in triplicate
wells individual dose, monolayer cells were incubated with the
compounds for 48 h at 37ꢂC and in atmosphere of 5% CO2.
After 48 h, cells were fixed, washed and stained with SRB
stain, excess stain was washed with acetic acid and attached
stain was recovered with tris-EDTA buffer, color intensity was
measured in an ELISA reader, the relation between surviving
fraction and drug concentration is plotted to get the survival
curve of tumor cell line and the IC50 was calculated. The
results are summarized in Table 1.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet