Synthesis, antitumor activity, and electrochemical behavior of some piperazinyl amidrazones

Article abstract of DOI:10.1007/s00706-009-0241-4

New piperazinyl amidrazones have been synthesized by direct interaction of the corresponding aryl hydrazones with the appropriate piperazine. On the basis of preliminary screening data for these new compounds, the antitumor activity of 1-(4-methylpiperazi

Full text of DOI:10.1007/s00706-009-0241-4

Monatsh Chem (2010) 141:251–258
DOI 10.1007/s00706-009-0241-4
ORIGINAL PAPER
Synthesis, antitumor activity, and electrochemical behavior
of some piperazinyl amidrazones
•
Raid Jamil Abdel-Jalil Ehab Q. El Momani Muawiah Hamad Wolfgang Voelter
•
•
•
•
•
Mohammad S. Mubarak Bianna H. Smith Dennis G. Peters
Received: 28 March 2009 / Accepted: 15 December 2009 / Published online: 27 January 2010
Ó Springer-Verlag 2010
Abstract New piperazinyl amidrazones have been synthe-
sized by direct interaction of the corresponding aryl
hydrazones with the appropriate piperazine. On the basis of
preliminary screening data for these new compounds, the
antitumor activity of 1-(4-methylpiperazin-1-yl)-1,2-propan-
dione 1-[2-(4-chlorophenyl)hydrazone] and 1-(4-ethylpipera-
zin-1-yl)-1,2-propandione 1-[2-(4-chlorophenyl)hydrazone]
was evaluated. Mean 50% growth inhibition (GI50), 50% cell
killing (LC50), and total growth inhibition (TGI) for both
compounds were calculated on the basis of data obtained from
55 test cell lines. Mean GI50 is significantly lower for the
methylpiperazine derivative (4.81 lM) compared with that of
the ethylpiperazine derivative (4.92 lM) (p[0.01); how-
ever, mean TGI is not measurably different (p[0.1) for both
compounds (4.52 and 4.52 lM, respectively). Both com-
pounds exhibit substantial antitumor activity against a number
of cell lines at 4 lM concentration. It was found that the
methylpiperazine derivative is more potent against leukemia
cell lines (mean GI50 = 4.73 lM and mean TGI = 4.36 lM),
whereas the ethylpiperazine derivative is more potent against
CNS cell lines (GI50 = 4.68 lM and mean TGI = 4.37 lM).
Cancers of the breast are least susceptible to methylpiperazine
derivative activity compared with all other cell lines (mean
GI50 = 4.91 lM). Melanomas and renal cancers are least
susceptible to the ethylpiperazine derivative activity as com-
pared with other cancer types (mean GI50 = 5.06 lM). Cyclic
voltammetry has been employed to probe the electrochemical
oxidation and reduction of the piperazinyl amidrazones at
glassy carbon electrodes in dimethylformamide containing
tetramethylammonium tetrafluoroborate.
R. J. Abdel-Jalil (&)
Department of Chemistry, College of Science,
Sultan Qaboos University, Masqat, Oman
e-mail: jalil@squ.edu.jo; jalil@hu.edu.jo
Keywords Piperazinyl amidrazones ꢀ Cancer drugs ꢀ
CNS cancers ꢀ Cyclic voltammetry
E. Q. El Momani
Department of Chemistry, Faculty of Science,
Hashemite University, Zarqa, Jordan
Introduction
M. Hamad
Department of Biological Sciences, Faculty of Science,
Hashemite University, Zarqa, Jordan
One cannot overlook the significance of synthesizing and
testing new compounds for potential therapeutic purposes,
especially given the fact that the majority of drugs in use
today came as a direct outcome of this endeavor [1].
Undoubtedly, cancer ranks high among human diseases
still in dire need of effective therapy [2]. Notwithstanding
the fact that the mechanisms of transformation, tumor
genesis, and metastasis are much better understood now,
advances in the area of anticancer therapy are occurring at
a much slower pace [3]. Lack of a wide array of anticancer
drugs able to capitalize on new discoveries regarding tumor
genesis, coupled with the unique growth patterns of the
W. Voelter
¨
Interfakultares Institut fur Biochemie der Universitat Tubingen,
Hoppe-Seyler-Straße 4, Tu¨bingen 72076, Germany
¨
¨
¨
M. S. Mubarak
Department of Chemistry, University of Jordan, Amman, Jordan
B. H. Smith ꢀ D. G. Peters (&)
Department of Chemistry, Indiana University,
Bloomington, IN 47405, USA
e-mail: peters@indiana.edu
123

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R. J. Abdel-Jalil et al.
diverse repertoires of cancer, makes all approaches
including the shotgun ones the more acceptable.
Different stoichiometric amounts of the piperazine
(ranging from 1 to 5 equivalents) were used; the highest
yields were obtained when a slight excess (1.25 equivalent)
of the piperazine was employed. In the 1H NMR spectra of
the amidrazones, exchangeable protons give signals at 9.0–
9.2 ppm, the a-methyl carbonyl protons resonate at 2.3–
2.5 ppm, and the piperazinyl protons are revealed by two
broad singlets at 2.5–3.5 ppm.
Due to their structural and therapeutic diversity, along
with their commercial availability, piperazine derivatives
have drawn considerable attention from organic and
medicinal chemists. Piperazine molecular templates have
been associated with a broad spectrum of biological activity;
piperazine-based compounds have been employed as anti-
bacterial [4], antidepressant [5], and antitumor [6] drugs, and
as a-adrenoceptor antagonists [7], CCR5 receptor antago-
nists [8], 5-HT7 receptor antagonists [9], and adenosine A2a
receptor antagonists [10]. Several piperazine derivatives
have reached the stage of clinical application; a pyrimidinyl
piperazinyl compound (buspirone, BuSparÒ) is used to
treat anxiety [11], and a 3-chlorophenyl piperazinyl drug
(trazodone, DesyrelÒ) is an antidepressant [12].
Biology
Evaluation of antitumor activity on a 55-human tumor cell
line panel was conducted by the Developmental Thera-
peutics Program (DTP) of the National Cancer Institute
(NCI), National Institutes of Health (NIH), Maryland, USA
(http://dtps7.ncicrf.gov).
Moreover, and equally pertinent to the present investi-
gation, aryl amidrazones [possessing the –C6H4–NH–
C(COCH3)=N–NH–C6H4– core] have recently been found
to be potent corticotrophin-releasing factor (CRF) receptor
antagonists [13]. Several publications have dealt with the
synthesis and evaluation of thrombin inhibitors that
incorporate an amidrazone functionality as a structural
motif [14–16], and there is a report pertaining to the
inactivation of lipoxygenase-1 from soybeans by open-
chain and cyclic amidrazones [17].
Preliminary screening of piperazinyl amidrazones
Preliminary screening data for the 12 different piperazinyl
amidrazones prepared according to the protocol shown
in Scheme 1 revealed that only two compounds, 1-(4-
methylpiperazin-1-yl)-1,2-propandione, 1-[2-(4-chlorophenyl)
hydrazone] (4a) and 1-(4-ethylpiperazin-1-yl)-1,2-pro-
pandione, 1-[2-(4-chlorophenyl)hydrazone] (4b), yielded
percent test cell growth compared with untreated control
cells (PTC) values of \32%, indicative of their reduced
mitogenic and/or increased antigrowth potential.
With the preceding information in mind, we have syn-
thesized a set of new piperazinyl amidrazones in a search
for possible therapeutic agents. In this report we describe
the chemical preparation and spectroscopic characteriza-
tion of these compounds, the evaluation of their antitumor
activity, and their electrochemical behavior at a vitreous
carbon electrode in dimethylformamide containing tetra-
methylammonium tetrafluoroborate (TMABF4). Although
the electrochemistry of hydrazones has been examined in
substantial detail [18–25], we are not aware of any previous
study of the electrochemical oxidation and reduction of
piperazinyl amidrazones.
Respective PTC values for the NCI-H460 (lung), MCF-
7 (breast), and SF-268 (CNS) cell lines were found to be 9,
7, and 53% for 4a and 6, 5, and 17% for 4b. Therefore,
both compounds were deemed suitable for additional
assessment of antitumor activity. All other compounds
(3a–3d, 4c, 4d, and 5a–5d) exhibited PTC values of[32%,
resulting in their exclusion from further testing.
Screening of 4a and 4b
Mean 50% growth inhibition (GI50), 50% cell killing
(LC50), and total growth inhibition (TGI) values for 4a and
4b were calculated on the basis of data obtained from
cultures on 55 and 54 cell lines, respectively (Table 1).
Mean GI50 was significantly lower for 4a (4.81 lM)
compared with that of 4b (4.92 lM) (t test = 2.183;
0.05 [ p [ 0.01). Mean LC50 values for both compounds
(4.17 and 4.19 lM, respectively) were statistically similar
(t test = 0.84; p \ 0.5). Additionally, the mean TGI for 4a
(4.47 lM) was not significantly different (t test = 1.418;
p [ 0.1) from that of 4b (4.52 lM). It is worth noting that
the range of activity for both compounds was narrow for all
three parameters (Table 1). Furthermore, both compounds
exhibited significant antitumor activity against a number of
cell lines at 4 lM concentration.
Results and discussion
Chemistry
Syntheses of piperazinyl amidrazones 3–5 were carried out
via the route shown in Scheme 1. Hydrazonyl chlorides
were prepared according to a procedure described by
Hussein and co-workers [26], which entails diazotization of
an appropriate p-substituted aniline (1a–1c) followed by
coupling with 3-chloro-2,4-pentanedione to afford 2a–2c.
Treatment of the hydrazonyl chloride with a N-substituted
piperazine in the presence of triethylamine gives the
desired piperazinyl amidrazone in good yield.
123

Synthesis, antitumor activity, and electrochemical behavior of some piperazinyl amidrazones
253
Scheme 1
NH2
X
O
(i) NaNO2, HCl
N
H3C
N
H
(ii) HCCl(COCH3)2,
C5H5N / H2O
Cl
2a-2c
X
1a
: X = H
1b
: X = Cl
1c
: X = Br
(iii) R-substituted piperazine,
triethylamine, ethanol
(reflux)
X
O
N
H3C
N
H
N
N
R
5a
: X = Br, R = CH3
3a
: X = H, R = CH3
4a
4b
: X = Cl, R = CH3
: X = Cl, R = C2H5
5b
5c
5d
3b
: X = Br, R = C2H5
: X = Br, R = C6H5
: X = H, R = C2H5
3c
4c
4d
: X = H, R = C6H5
: X = Cl, R = C6H5
3d
: X = Br, R = p-F-C6H4
: X = H, R = p-F-C6H4
: X = Cl, R = p-F-C6H4
were melanomas, renal cancers, and non-small lung cancers;
mean GI50 concentrations were 5.06, 5.06, and 4.97 lM,
respectively.
Table 1 Mean antitumor activity of 4a and 4b as tested on 55 and 54
different cell lines, respectively
Dose response parameter
Compound
On the basis of the TGI dose-response parameter,
4a was more potent against leukemia cell lines (mean
TGI = 4.36 lM) and non-small cell lung cancers (mean
TGI = 4.19 lM), whereas 4b was most potent against
CNS cell lines with a mean TGI of 4.37 lM. The least
susceptible cell lines against 4a antitumor activity were
cancers of the kidney, ovary, and breast, in addition to
melanomas; mean TGI concentrations were 4.53, 4.53,
4.52, and 4.52 lM, respectively. Least susceptible cell
lines against 4b antitumor activity were melanomas, renal
cancer, and non-small cell lung cancers; mean TGI con-
centrations were 4.64, 4.62, and 4.57 lM, respectively.
Once again, the range for antitumor activity considering
all three dose-response parameters was narrow. Both com-
pounds exhibited antitumor activity against some tumor cell
lines at 4.0 lM concentration. Most notable was the activity
of 4b against the breast cancer MCF7 cell line where
4.0 lM was the concentration of GI50, LC50, and TGI.
From the results of this study, it is clear that both 4a and
4b bear significant antitumor activity against a number of
human tumor cell lines, especially leukemia, non-small cell
lung cancer, and CNS cancers. Given the finding that the
4a (lM)
4b (lM)
GI50 (mean standard deviation)
GI50 (range)
4.81 0.181
4.49–5.50
4.92 0.326
4.00–5.72
LC50 (mean standard deviation)
LC50 (range)
4.17 0.097
4.00–4.42
4.19 0.147
4.00–4.80
TGI (mean standard deviation)
TGI (range)
4.47 0.125
4.00–9.93
4.52 0.229
4.00–5.27
A detailed analysis of GI50, LC50, and TGI per cancer-
type subpanel is provided in Table 2, and a number of
interesting points are revealed. On the basis of the GI50
parameter, 4a was more potent against leukemia cell lines
(mean GI50 = 4.73 lM), non-small cell lung cancers (mean
GI50 = 4.76 lM), colon cancer (mean GI50 = 4.76 lM),
and CNS cancers (mean GI50 = 4.77 lM). On the other
hand, 4b was more potent against CNS cell lines with a mean
GI50 of 4.68 lM. The least susceptible cell lines against 4a
activity were cancers of the breast, prostate, and ovaries;
mean GI50 concentrations were 4.91, 4.88, and 4.87 lM,
respectively. Least susceptible cell lines against 4b activity
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R. J. Abdel-Jalil et al.
Table 2 Mean antitumor activity of 4a and 4b against various tumor-cell-line subpanels as defined by type of cancer
Cell-line subpanel (no. of cell lines)
Compound 4a
Mean GI50 (range) (lM)
Mean LC50 (range) (lM)
Mean TGI (range) (lM)
Leukemia (5)
4.73 0.77 (4.62–4.82)
4.76 0.115 (4.49–4.93)
4.76 0.045 (4.71–4.81)
4.77 0.079 (4.69–4.86)
4.80 0.193 (4.68–4.88)
4.87 0.051 (4.73–5.29)
4.84 0.082 (4.74–4.99)
4.88 0.021 (4.75–4.85)
4.91 0.452 (4.75–5.50)
4.07 0.076 (4.00–4.18)
4.13 0.091 (4.00–4.25)
4.16 0.099 (4.00–4.27)
4.15 0.089 (4.00–4.24)
4.21 0.065 (4.11–4.27)
4.23 0.059 (4.19–4.32)
4.22 0.044 (4.16–4.30)
4.07 0.099 (4.00–4.14)
4.16 0.148 (4.00–4.42)
4.36 0.134 (4.14–4.50)
4.19 0.166 (4.00–4.57)
4.46 0.072 (4.34–4.54)
4.45 0.088 (4.33–4.55)
4.51 0.070 (4.40–4.57)
4.53 0.104 (4.47–4.71)
4.53 0.057 (4.48–4.64)
4.42 0.099 (4.35–4.49)
4.52 0.185 (4.36–4.93)
Non-small cell lung cancer (9)
Colon cancer (7)
CNS cancer (5)
Melanoma (7)
Ovarian cancer (5)
Renal cancer (8)
Prostate cancer (2)
Breast cancer (7)
Cell-line subpanel (no. of cell lines)
Compound 4b
Mean GI50 (range) (lM)
Mean LC50 (range) (lM)
Mean TGI (range) (lM)
Leukemia (5)
4.93 0.085 (4.84–5.04)
4.97 0.467 (4.21–5.72)
4.88 0.157 (4.71–5.13)
4.68 0.168 (4.39–4.82)
5.06 0.288 (4.74–5.63)
4.93 0.301 (4.74–5.33)
5.06 0.280 (4.84–5.38)
4.88 0.156 (4.77–4.99)
4.85 0.517 (4.00–5.61)
4.17 0.056 (4.09–4.21)
4.21 0.163 (4.00–4.59)
4.15 0.137 (4.00–4.30)
4.14 0.100 (4.00–4.27)
4.23 0.254 (4.00–4.80)
4.15 0.085 (4.00–4.21)
4.27 0.044 (4.18–4.33)
4.22 0.014 (4.21–4.23)
4.11 0.160 (4.00–4.44)
4.55 0.049 (4.49–4.60)
4.57 0.320 (4.00–5.22)
4.45 0.234 (4.00–4.66)
4.37 0.215 (4.00–4.55)
4.64 0.308 (4.34–5.27)
4.48 0.075 (4.33–4.60)
4.62 0.080 (4.51–4.76)
4.55 0.085 (4.49–4.61)
4.43 0.263 (4.00–4.90)
Non-small cell lung cancer (9)
Colon cancer (7)
CNS cancer (5)
Melanoma (7)
Ovarian cancer (5)
Renal cancer (8)
Prostate cancer (2)
Breast cancer (7)
range of antitumor activity of both agents against the var-
ious tumor cell lines was very narrow, it can be stated that
both compounds possess generalized antitumor activity.
Yet to be elucidated is the exact mechanism by which
either compound suppresses cancer growth. This issue is
under intensive study, and results will be published in due
course.
that the main anodic peak is seen only after a preceding
negative-going scan. Moreover, associated with the main
anodic peak is another small anodic peak at ?0.06 V as
well as a small cathodic peak at -0.60 V. In general, those
compounds (3a–3d) without an aryl chlorine or bromine
substituent exhibit three main cathodic peaks and one main
anodic peak, whereas the halogenated species (4a–4d and
5a–5d) show four main cathodic peaks (the last of which is
not always well defined) along with one main anodic peak.
To aid further interpretation of the cyclic voltammograms
for the piperazinyl amidrazones, we carried out separate
cyclic voltammetry studies of the oxidation and reduction of
2.0 mM solutions of 1,4-dimethylpiperazine (6), 4-chloro-
N-methylaniline (7), and pyruvaldehyde 1-phenylhydrazone
(1-(2-phenylhydrazono)propan-2-one, 8) at a glassy carbon
electrode in DMF containing 0.050 M TMABF4. No elec-
troactivity for 6 was observed within the range of potentials
from ?0.26 to -3.05 V versus SCE, which reveals that a
tertiary amine (N-alkylated piperazine) undergoes neither
oxidation nor reduction under the conditions of our experi-
ments. When the electrochemistry of 7 was examined, only a
single cathodic peak was observed at -2.85 V versus SCE,
which can be attributed to two-electron reductive cleavage
Cyclic voltammetric behavior of piperazinyl
amidrazones
Cyclic voltammograms were acquired for the reduction and
oxidation of each of the piperazinyl amidrazones at a
glassy carbon electrode in DMF containing 0.050 M
TMABF4. Table 3 provides a compilation of the cathodic
and anodic peak potentials for these compounds. A repre-
sentative cyclic voltammogram recorded at a scan rate of
100 mV s-1 for a 2.0 mM solution of 4a in DMF-0.050 M
TMABF4 is shown in Fig. 1. Four cathodic peaks are
observed with peak potentials of -1.89, -2.56, -2.75, and
-2.91 V versus SCE, and a single oxidation peak appears
at -0.35 V versus SCE. Note that the third cathodic peak is
a shoulder on the side of the fourth peak. It is significant
123

Synthesis, antitumor activity, and electrochemical behavior of some piperazinyl amidrazones
255
Table 3 Cathodic and anodic
peak potentials for piperazinyl
amidrazones
Compound
Cathodic peak
potentials (V vs. SCE)
Anodic peak potential
(V vs. SCE)
3a
3b
3c
3d
4a
4b
4c
4d
5a
5b
5c
5d
-1.95
-1.94
-1.93
-1.92
-1.89
-1.88
-1.86
-1.86
-1.90
-1.89
-1.88
-1.89
-2.62
-2.58
-2.58
-2.57
-2.56
-2.55
-2.51
-2.49
-2.40
-2.39
-2.38
-2.37
-2.78
-2.77
-2.76
-2.73
-2.75
-2.74
-2.73
-2.73
-2.59
-2.60
-2.54
-2.57
-0.43
-0.44
-0.40
-0.39
-0.35
-0.36
-0.33
-0.33
-0.36
-0.34
-0.32
-0.32
-2.91
-2.88
-2.89
-2.86
-2.81
-2.78
-2.75
-2.78
A separate and more thorough investigation of the
electrochemistry of these compounds is planned for the
future, so that details of the redox reactions can be delin-
eated, and intermediates and products arising from these
electron-transfer processes can be identified.
Experimental
Instrumentation and chemicals
Melting points (°C) were measured with a SMP2 Stuart
apparatus. All new compounds were analyzed for C, H, and
N, and the observed results agreed with the calculated per-
centages to within 0.4%. We obtained H and 13C NMR
1
Fig. 1 Cyclic voltammogram recorded with a glassy carbon elec-
trode (area = 0.071 cm2) at a scan rate of 100 mV s-1 for a 2.0 mM
solution of 1-(4-methylpiperazin-1-yl)-1,2-propandione, 1-[2-(4-chlo-
rophenyl)hydrazone] (4a) in DMF containing 0.050 M TMABF4.
Potential was scanned from -0.76 to -3.05 to ?0.26 to -0.76 V
versus SCE
spectra with a Bruker DPX-300 spectrometer; chemical
shifts are reported in ppm relative to TMS as internal stan-
dard. Infrared (IR) spectra were recorded as KBr discs on a
Nicolet-MAGNA-IR-560 spectrometer. Solid-probe high-
resolution mass spectral data were acquired with the aid of a
Thermo Electron Corporation MAT 95XP-Trap instrument,
operated in the positive chemical-ionization (CI) mode with
methane as the reagent gas.
of the aryl carbon–chlorine bond; thus, we believe that the
fourth cathodic peak listed in Table 3 for compounds 4a–4d
arises from reduction of the aromatic carbon-chlorine bond.
A cyclic voltammogram for 8 showed a well-resolved
cathodic peak at –1.69 V versus SCE, two partially over-
lapping cathodic peaks at –2.38 and -2.46 V versus SCE,
and an anodic peak at ?0.04 V versus SCE. Thus, the
electrochemical behavior of compounds 3a and 8 is quali-
tatively similar, which leads us to conclude that the observed
electroactivity of 3a resides in its H3C–CO–C=N–NH–C6H5
moiety; apparently, the presence of the methyl piperazinyl
substituent of 3a shifts the cathodic and anodic peak
potentials significantly toward more negative values in
comparison with compound 8.
We purchased and used as received from commercial
sources 3-chloro-2,4-pentanedione and the N-substituted
piperazines. Dimethylformamide (DMF, ACS spectropho-
tometric grade, 99.8%) was employed, without further
purification, as the solvent for electrochemical experiments.
Tetramethylammonium tetrafluoroborate (TMABF4), used
as the supporting electrolyte, was recrystallized from water-
methanol and thoroughly dried by continuous storage in
a vacuum oven at 80 °C. Deaeration of solutions for
cyclic voltammetry was accomplished with zero-grade
argon. To aid in the interpretation of cyclic voltammograms
for the various piperazinyl amidrazones, commercially
available 1,4-dimethylpiperazine, 4-chloro-N-methylaniline,
123

256
R. J. Abdel-Jalil et al.
(C=N), 114.22, 116.42, 120.14, 122.30, 129.24, 129.56,
142.53, 143.22 (Ar), 50.22, 48.12 (piperazine), 25.81
(COCH3); IR (KBr): v ¼ 3;420; 1,678, 1,537 cm-1; HRMS
(CI): m/z = 323.1881 ([M ? H]?, calcd for C19H23N4O
323.1872) ppm.
and pyruvaldehyde 1-phenylhydrazone -1-(2-phenylhyd-
razono)propan-2-one were used as model compounds.
Synthesis of hydrazonyl chlorides 2a–2c
These compounds were prepared via the Japp-Klingemann
reaction involving coupling of arenediazonium salts to
1-[4-(4-Fluorophenyl)piperazin-1-yl]-1,2-propandione,
1-(2-phenylhydrazone) (3d, C19H21FN4O)
1
3-chloro-2,4-pentanedione [26]. H NMR and 13C NMR
Yield 2.59 g (76%); m.p.: 160–164 °C; Rf = 0.55; 1H
NMR (CDCl3): d = 9.19 (s, 1H, NH), 6.89–7.50 (m, 9H,
Ar), 3.20, 3.19 (each bs, each 4H, piperazine), 2.43 (s, 3H,
COCH3); 13C NMR (CDCl3): d = 195.09 (C=O), 158.96
(C=N), 114.20, 115.48, 115.77, 118.13, 118.24, 122.31,
129.54, 142.48, 143.12, 148.12, 148.15 (Ar), 51.18, 48.08
(piperazine), 25.75 (COCH3); IR (KBr): v ¼ 3;420; 1,678,
1,537 cm-1; HRMS (CI): m/z = 341.1780 ([M ? H]?,
calcd for C19H22FN4O 341.1778) ppm.
spectra were identical with those described in Ref. [26].
General procedure for the synthesis of piperazinyl
amidrazones 3–5
To a stirred solution of the appropriate hydrazonyl chloride
2 (0.10 mol) and triethylamine (0.11 mol) in 40 cm3 eth-
anol, the appropriate piperazine (0.125 mol) was added
dropwise over 10 min at room temperature. Then the
reaction mixture was refluxed for 3 h. Finally, the solvent
was removed in vacuo, and the residue was purified by
means of flash column chromatography with dichloro-
methane–ethyl acetate (4:1 v/v) to give the desired
piperazinyl amidrazone.
1-(4-Methylpiperazin-1-yl)-1,2-propandione,
1-[2-(4-chlorophenyl)hydrazone] (4a, C14H18ClN4O)
Yield 2.63 g (85%); m.p.: 110–112 °C; Rf = 0.67; 1H NMR
(CDCl3): d = 9.03 (s, 1H, NH), 7.25 (d, J = 8.8 Hz, 2H,
C6H4Cl), 7.10 (d, J = 8.9 Hz, 2H, C6H4Cl), 3.06, 2.50 (each
bs, each 4H, piperazine), 2.38 (s, 3H, NCH3), 2.34 (s, 3H,
COCH3); 13C NMR (CDCl3): d = 194.92 (C=O), 143.75
(C=N), 115.28, 129.41, 141.28, 126.77 (C6H4Cl), 55.77,
47.69 (piperazine), 46.38 (CH3), 25.76 (COCH3); IR (KBr):
1-(4-Methylpiperazin-1-yl)-1,2-propandione,
1-(2-phenylhydrazone) (3a, C14H20N4O)
1
Yield 1.96 g (75%); m.p.: 79–80 °C; Rf = 0.63; H NMR
(CDCl3): d = 9.08 (s, 1H, NH), 6.91–7.30 (m, 5H, C6H5),
3.03, 2.46 (each bs, each 4H, piperazine), 2.36 (s, 3H,
NCH3), 2.30 (s, 3H, COCH3); 13C NMR (CDCl3):
d = 194.90 (C=O), 143.39 (C=N), 114.12, 122.08,
129.44, 142.59 (C6H5), 55.88, 47.79 (piperazine), 46.47
(CH3), 25.71 (COCH3); IR (KBr): v ¼ 3;420; 1,678,
1,537 cm-1; HRMS (CI): m/z = 261.1709 ([M ? H]?,
calcd for C14H21N4O 261.1715) ppm.
v ¼ 3;420; 1,678, 1,537 cm-1; HRMS (CI): m/z = 295.1339
35
([M ? H]?, calcd for C14H ClN4O 295.1326), 297.1322
19
([M ? H]?, calcd for C14H ClN4O 297.1296) ppm.
37
19
1-(4-Ethylpiperazin-1-yl)-1,2-propandione,
1-[2-(4-chlorophenyl)hydrazone] (4b, C15H21ClN4O)
Yield 2.22 g (72%); m.p.: 100–102 °C; Rf = 0.72; 1H NMR
(CDCl3): d = 9.05 (s, 1H, NH), 7.23 (d, J = 8.9 Hz, 2H,
C6H4Cl), 7.09 (d, J = 8.9 Hz, 2H, C6H4Cl), 3.06, 2.51 (each
bs, each 4H, piperazine), 2.44 (q, J = 7.2 Hz, 2H,
CH2CH3), 2.37 (s, 3H, COCH3), 1.09 (t, J = 7.2 Hz, 3H,
CH2CH3); 13C NMR (CDCl3): d = 194.88 (C=O), 143.84
(C=N), 115.26, 129.39, 141.32, 126.69 (C6H4Cl), 53.57,
47.83 (piperazine), 52.59 (CH2CH3), 25.76 (COCH3), 12.03
1-(4-Ethylpiperazin-1-yl)-1,2-propandione,
1-(2-phenylhydrazone) (3b, C15H22N4O)
1
Yield 2.15 g (78%); m.p.: 50–54 °C; Rf = 0.67; H NMR
(CDCl3): d = 9.10 (s, 1H, NH), 6.94–7.31 (m, 5H, C6H5),
3.06, 2.51 (each bs, each 4H, piperazine), 2.44 (q,
J = 7.2 Hz, 2H, CH2CH3), 2.37 (s, 3H, COCH3), 1.09 (t,
J = 7.2 Hz, 3H, CH2CH3); 13C NMR (CDCl3): d = 194.94
(C=O), 143.47 (C=N), 114.11, 122.06, 129.45, 142.60
(C6H5), 53.64, 47.86 (piperazine), 52.61 (CH2CH3), 25.72
(COCH3), 12.07 (NCH2CH3); IR (KBr): v ¼ 3;420; 1,678,
1,537 cm-1; HRMS (CI): m/z = 275.1862 ([M ? H]?,
calcd for C15H23N4O 275.1872) ppm.
(NCH2CH3); IR (KBr): v ¼ 3;420; 1,678, 1,537 cm-1
;
HRMS (CI): m/z = 309.1475 ([M ? H]?, calcd for
35
22
C15H ClN4O 309.1482), 311.1469 ([M ? H]?, calcd for
37
C15H ClN4O 311.1453) ppm.
22
1-(4-Phenylpiperazin-1-yl)-1,2-propandione,
1-[2-(4-chlorophenyl)hydrazone] (4c, C19H21ClN4O)
Yield 3.03 g (85%); m.p.: 145–150 °C; Rf = 0.60; 1H
NMR (CDCl3): d = 9.16 (s, 1H, NH), 6.92–7.32 (m, 5H,
C6H5), 7.27 (d, J = 8.8 Hz, 2H, C6H4Cl), 7.13 (d,
J = 8.8 Hz, 2H, C6H4Cl), 3.27, 3.25 (each bs, each 4H,
piperazine), 2.43 (s, 3H, COCH3); 13C NMR (CDCl3):
d = 150.96 (C=O), 143.46 (C=N), 114.82, 115.40, 116.71,
116.94, 117.35, 120.65, 126.94, 127.62, 129.08, 129.31,
1-(4-Phenylpiperazin-1-yl)-1,2-propandione,
1-(2-phenylhydrazone) (3c, C19H22N4O)
Yield 2.40 g (74%); m.p.: 158–162 °C; Rf = 0.42; 1H
NMR (CDCl3): d = 9.22 (s, 1H, NH), 6.90–7.37 (m, 10H,
Ar), 3.26, 3.25 (each bs, each 4H, piperazine), 2.46 (s, 3H,
COCH3); 13C NMR (CDCl3): d = 195.10 (C=O), 151.50
123

Synthesis, antitumor activity, and electrochemical behavior of some piperazinyl amidrazones
257
129.47, 141.23, 141.39 (Ar), 50.42, 47.90 (piperazine),
25.85 (COCH3); IR (KBr): v ¼ 3;420; 1,678, 1,537 cm-1
143.50 (C=N), 114.36, 115.24, 115.79, 116.82, 116.96,
129.33, 136.16, 132.36, 141.65 (Ar), 50.51, 47.77 (piper-
azine), 25.84 (COCH3); IR (KBr): v ¼ 3;420; 1,678,
1,537 cm-1; HRMS (CI): m/z = 401.0997 ([M ? H]?,
;
HRMS (CI): m/z = 357.1480 ([M ? H]?, calcd for
35
22
C19H ClN4O 357.1482), 359.1490 ([M ? H]?, calcd for
37
calcd for C19H BrN4O 401.0977), 403.0986 ([M ? H]?,
79
C19H ClN4O 359.1453) ppm.
22
22
81
calcd for C19H BrN4O 403.0957) ppm.
22
1-[4-(4-Fluorophenyl)piperazin-1-yl]-1,2-propandione,
1-[2-(4-chlorophenyl)hydrazone] (4d, C19H20ClFN4O)
Yield 3.08 g (82%); m.p.: 150–154 °C; Rf = 0.59; 1H NMR
(CDCl3): d = 9.13 (s, 1H, NH), 6.87–6.99 (m, 4H, C6H4F),
7.26 (d, J = 8.8 Hz, 2H, C6H4Cl), 7.11 (d, J = 8.8 Hz, 2H,
C6H4Cl), 3.18 (bs, 8H, piperazine), 2.41 (s, 3H, COCH3);
13C NMR (CDCl3): d = 195.00 (C=O), 159.01 (C=N),
114.36, 115.50, 115.79, 118.18, 118.28, 126.94, 129.46,
141.19, 143.49, 148.02, 155.83 (Ar), 51.15, 48.04 (pipera-
zine), 25.81 (COCH3); IR (KBr): v ¼ 3;420; 1,678,
1,537 cm-1; HRMS (CI): m/z = 375.1405 ([M ? H]?,
1-[4-(4-Fluorophenyl)piperazin-1-yl]-1,2-propandione,
1-[2-(4-bromophenyl)hydrazone] (5d, C19H20BrFN4O)
Yield 3.15 g (75%); m.p.: 152–154 °C; Rf = 0.38; 1H
NMR (CDCl3): d = 9.12 (s, 1H, NH), 6.87–6.99 (m, 4H,
C6H4F), 7.40 (d, J = 8.5 Hz, 2H, C6H4Br), 7.06 (d,
J = 8.5 Hz, 2H, C6H4Br), 3.18 (bs, 8H, piperazine), 2.41 (s,
3H, COCH3); 13C NMR (CDCl3): d = 195.00 (C=O), 159.02
(C=N), 114.32, 115.50, 115.76, 115.79, 118.16, 118.26,
132.36, 141.63, 143.56, 148.04, 148.07, 155.82 (Ar), 51.16,
48.06 (piperazine), 25.83 (COCH3); IR (KBr): v ¼ 3;420;
calcd for C19H ClFN4O 375.1388), 377.1415 ([M ? H]?,
1,678, 1,537 cm-1
;
HRMS (CI): m/z = 419.0898
35
21
37
79
21
calcd for C19H ClFN4O 377.1358) ppm.
([M ? H]?, calcd for C19H BrFN4O 419.0883), 421.089
21
([M ? H]?, calcd for C19H BrFN4O 421.0862) ppm.
81
21
1-(4-Methylpiperazin-1-yl)-1,2-propandione,
1-[2-(4-bromophenyl)hydrazone] (5a, C14H19BrN4O)
Yield 2.68 g (79%); m.p.: 106–108 °C; Rf = 0.66; 1H NMR
(CDCl3): d = 6.03 (s, 1H, NH), 7.37 (d, J = 8.8 Hz, 2H,
C6H4Br), 7.04 (d, J = 8.8 Hz, 2H, C6H4Br), 3.04, 2.47 (each
bs, each 4H, piperazine), 2.36 (s, 3H, NCH3), 2.31 (s, 3H,
COCH3); 13C NMR (CDCl3): d = 194.91 (C=O), 143.86
(C=N), 115.70, 132.29, 141.74, 114.09 (C6H4Br), 55.84,
47.79 (piperazine), 46.46 (NCH3), 25.78 (COCH3); IR (KBr):
v ¼ 3;420; 1,678, 1,537 cm-1; HRMS (CI): m/z = 339.0805
Cyclic voltammetry
For cyclic voltammetry, we used a Faraday MP scanning
potentiostat, model F02A (Obbligato Objectives, Inc.), and
experiments were carried out with the aid of a companion
computer program installed on a personal computer. We
constructed a planar, circular working electrode with a
geometric area of 0.071 cm2 by press-fitting a short length
of 3-mm-diameter glassy carbon rod (Grade GC-20, Tokai
Electrode Manufacturing Co., Tokyo, Japan) into a Teflon
shroud. Before each cyclic voltammogram was recorded,
the working electrode was cleaned on a Master-Tex
(Buehler) polishing pad with an aqueous suspension of
0.05 lm alumina, after which the electrode was rinsed
ultrasonically in DMF and wiped dry before being inserted
into the electrochemical cell. A reference electrode con-
sisting of a cadmium-saturated mercury amalgam in
contact with DMF saturated with both cadmium chloride
and sodium chloride was employed. This reference elec-
trode has a potential of -0.76 V versus the aqueous
saturated calomel electrode (SCE) at 25 °C [27–29];
however, all potentials reported in this publication are
given with respect to the SCE. A description of the cell
used for cyclic voltammetry can be found in an earlier
paper [30]. This single-compartment, three-electrode cell
incorporates a platinum wire auxiliary (counter) electrode,
along with the aforementioned working and reference
electrodes.
([M ? H]?, calcd for C14H BrN4O 339.0820), 341.0790
79
20
81
20
([M ? H]?, calcd for C14H BrN4O 341.0800) ppm.
1-(4-Ethylpiperazin-1-yl)-1,2-propandione,
1-[2-(4-bromophenyl)hydrazone] (5b, C15H21BrN4O)
Yield 2.65 g (75%); m.p.: 115–120 °C; Rf = 0.71; 1H NMR
(CDCl3): d = 9.04 (s, 1H, NH), 7.38 (d, J = 8.8 Hz, 2H,
C6H4Br), 7.04 (d, J = 8.8 Hz, 2H, C6H4Br), 3.51, 3.06
(each bs, each 4H, piperazine), 2.44 (q, J = 7.3 Hz, 2H,
CH2CH3), 2.37 (s, 3H, COCH3), 1.09 (t, J = 7.2 Hz, 3H,
CH2CH3); 13C NMR (CDCl3): d = 194.91 (C=O), 143.93
(C=N), 115.69, 132.29, 141.78, 114.06 (C6H4Br), 53.58,
47.86 (piperazine), 52.60 (CH2CH3), 25.78 (COCH3), 12.04
(NCH2CH3); IR (KBr): v ¼ 3;420; 1,678, 1,537 cm-1
;
HRMS (CI): m/z = 353.0954 ([M ? H]?, calcd for
C15H BrN4O 353.0977), 355.0945 ([M ? H]?, calcd for
79
22
81
C15H BrN4O 355.0957) ppm.
22
1-(4-Phenylpiperazin-1-yl)-1,2-propandione,
1-[2-(4-bromophenyl)hydrazone] (5c, C19H21BrN4O)
Yield 3.00 g (75%); m.p.: 148–150 °C; Rf = 0.44; 1H
NMR (CDCl3): d = 9.12 (s, 1H, NH), 6.93–7.32 (m, 5H,
C6H5), 7.40 (d, J = 8.7 Hz, 2H, C6H4Br), 7.07 (d,
J = 8.7 Hz, 2H, C6H4Br), 3.28 (bs, 8H, piperazine), 2.42
(s, 3H, COCH3); 13C NMR (CDCl3): d = 195.12 (C=O),
Acknowledgments Financial support provided by Hashemite Uni-
versity is gratefully acknowledged. R. J. A.-J. thanks Deutsche
Forschungsgemeinschaft (DFG) for a research fellowship for visiting
faculty. High-resolution mass analyses were performed in the Indiana
123

258
R. J. Abdel-Jalil et al.
University Mass Spectrometry Facility; the HRMS system was pur-
chased with funds provided by the National Institutes of Health grant
no. 1S10RR016657-01.
14. Oh YS, Yun M, Hwang SY, Hong S, Shin Y, Lee K, Yoon KH,
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6:869
16. Lee K, Jung W-H, Park CW, Park HD, Lee SH, Kwon OH (2002)
Bioorg Med Chem Lett 12:1017
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