4-Substitutedphthalazines and phthalazinones: Synthesis, characterization and β-adrenergic blocking activity

Article abstract of DOI:10.1007/s00044-012-0099-6

Novel 4-(4-bromophenyl)phthalazine and phthalazinone derivatives connected through 2-propanol spacer to N-substituted piperazine residue were synthesized. All the new compounds were screened for their effect on β-adrenergic blocking activity on the norepinephrine-induced precontracted aortic ring module. Most test compounds displayed appreciable β-adrenolytic activity compared to propranolol as a reference standard. The results have shown that compounds 3a, 3d, 3e and 7c displayed appreciable inhibition of norepinephrine-induced aortic ring contraction. Graphical Abstract: A novel 4-(4-bromophenyl)phthalazine and phthalazinone derivatives connected through 2-propanol spacer to N-substituted piperazine residue were synthesized. All new compounds were screened for their effect on β-adrenergic blocking activity on the norepinephrine-induced precontracted aortic ring module.[Figure not available: see fulltext.]

Full text of DOI:10.1007/s00044-012-0099-6

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:1057–1064
DOI 10.1007/s00044-012-0099-6
ORIGINAL RESEARCH
4-Substitutedphthalazines and phthalazinones: synthesis,
characterization and b-adrenergic blocking activity
•
Khaled A. M. Abouzid Nadia A. Khalil
•
Eman M. Ahmed
Received: 26 December 2011 / Accepted: 15 May 2012 / Published online: 31 May 2012
Ó Springer Science+Business Media, LLC 2012
Abstract Novel 4-(4-bromophenyl)phthalazine and phtha-
lazinone derivatives connected through 2-propanol spacer to
N-substituted piperazine residue were synthesized. All the new
compounds were screened for their effect on b-adrenergic
blocking activity on the norepinephrine-induced precontracted
aortic ring module. Most test compounds displayed appreciable
b-adrenolytic activity compared to propranolol as a reference
standard. The results have shown that compounds 3a, 3d, 3e
and 7c displayed appreciable inhibition of norepinephrine-
induced aortic ring contraction.
myocardial infarction and heart failure (Panjrath and
Messerli, 2006). Also, much attention is being paid to
b-blockers that possess vasodilator action produced
through different mechanisms, such as release of nitric
oxide (NO), antioxidant action, b2-agonistic action, Ca
entry blockade and a1-blockade (Toda, 2003).
In the last decade, a new generation of b-blockers with
additional a-adrenoceptor blocking activity was introduced
to therapy. The a/b-blockers (bucindolol, carvedilol and
labetalol) have vasodilating properties via relaxation of
arterial smooth muscle, with no reflex tachycardia, as a
result of b-adrenoceptor blockade (Matsuda et al., 2000;
Marona et al., 2008). They have also beneficial effects on
the regular circulation in contrast to classic b-blockers
(Toda, 2003; Carella et al., 2010).
Keywords Phthalazines Á Phthalazinones Á
Adrenergic b-blockers Á Arylpiperazine
Introduction
Pyridazinone and phthalazinone derivatives have been
reported to possess a variety of pharmacological effects on
the cardiovascular system (Demirayak et al., 2004a; Del
Olmo et al., 2006; Bansal et al., 2009). Within the drugs in
the market, hydralazine, one of the first antihypertensive
agents, is considered as a lead for developing new drugs,
due to its direct vasodilator effect (Del Olmo et al., 2006).
Structural modification of hydralazine led to the discovery
of new phthalazine candidates possessing antihypertensive
effect (Demirayak et al., 2004b). However, in the long-
term treatment of hypertension, the use of vasodilators
alone does not suffice and it is the concomitant use of
b-blockers which has proved to be useful for achieving
adequate control of blood pressure (Bisi et al., 2003).
b-Adrenergic blocking agents are very homogeneous in
their chemical structures, which generally include the
2-aminoethanol basic skeleton to which the other groups of
molecules are linked and which should be associated
principally with the ability of these compounds to bind
with the receptors (Saccomanni et al., 2003).
Despite the significant progress made in prevention and
treatment, cardiovascular diseases are still the main cause
of death worldwide (Lopez et al., 2006). The use of
b-adrenoceptor antagonists is well-established in the
treatment of various cardiovascular disorders. Since
development of this class of drugs in the late 1950s of
twentieth century, they are administered in the therapy
of hypertension, coronary artery disease, arrhythmia,
K. A. M. Abouzid
Department of Pharmaceutical Chemistry, Faculty of Pharmacy,
Ain Shams University, Cairo 11566, Egypt
e-mail: khaled.abouzid@pharm.asu.edu.eg
N. A. Khalil Á E. M. Ahmed (&)
Department of Pharmaceutical Organic Chemistry,
Faculty of Pharmacy, Cairo University, Cairo, Egypt
e-mail: dr_eman2001@hotmail.com
123

1058
Med Chem Res (2013) 22:1057–1064
O
On the other hand, the nature of aromatic nucleus gen-
O
erally determines the blocking or stimulant properties of
these compounds, (Macchia et al., 1985).
NH
N
1) a
2) b
N
b-Adrenergic antagonists containing phenylpiperazine
moiety comprise a class of compounds with ancillary
vasodilator properties and superior clinical efficacy com-
pared to classical b-blockers (Toda, 2003; Gonec et al.,
2008; Racanska et al., 2010).
O
N
Br
In the past few decades, progress in understanding the
biochemical pharmacology of b-blockers has lead to a
more rational approach in designing new drug combina-
tions involving this 2-hydroxylpropyl spacer. In this regard,
keeping the basic 2-hydroxypropyl spacer for significant
b-adrenoreceptor antagonistic activity in combination with
the vasorelaxant-substituted phthalazine pharmacophore,
two series of 4-(4-bromophenyl)phthalazine derivatives
connected through 2-propanol spacer to N-substitutedpip-
erazine residue 3a–f and 7a–f were synthesized with the
aim to elicit their b-adrenolytic activity.
Br
1
2
c
O
N
N
N
N
R
OH
3 a : R= CH3
3 b : R = C6H5
Br
3 c : R = 4-ClC6H4
Results and discussion
3 d: R= 2-OC2H5C6H4
3 e : R= 2-OCH3C6H4
3 f : R= 4-OCH3C6H4
3a-f
Chemistry
Scheme 1 Reagents and conditions: a C2H5ONa/C2H5OH, b epi-
chlorohydrin, DMSO, 25 °C, c 4-(substituted) piperazines, CH3CN,
K2CO3
The synthetic route used to synthesize the N-substituted
derivatives 3a–f is outlined in Scheme 1. 4-(4-Bromophe-
nyl)-2(1H)-phthalazinone (1) was prepared by cyclization
of 2-(4-bromobenzoyl)benzoic acid with hydrazine hydrate
according to reported methods (Yamaguchi et al., 1993;
Colotta et al., 1994). Reacting the sodium salt of 1 with
epichlorohydrin in dimethylsulphoxide afforded the inter-
mediate 2. The product thus obtained was identified by its
1HNMR spectrum that showed two doublet of doublets at
d2.76 and 2.83 ppm corresponding to two non-equivalent
protons of N–CH2. The oxirane ring was identified by the
existence of the two doublet of doublets at d4.43 and
4.46 ppm of the CH2–O non-equivalent protons and a
multiplet at 3.41–3.46 ppm due to CH–O proton. The mass
spectrum revealed the M and M?2 fragments, in addition
to the base beak at m/z 57 indicating the C3H5OÁ?
fragment.
corresponding to O–H were observed in the range of
1
3,450–3,300 cm-1. The HNMR spectra revealed signals
arising due to typical secondary alcohol. The spectra dis-
played two doublet of doublets of the non-equivalent pro-
tons of N–CH2 in the range of d 2.59–2.64 ppm, and two
multiplets at d3.0–3.16 and d 4.27–4.45 ppm correspond-
ing to N–CH2 and CH–O protons, respectively. The two
multiplets of piperazine protons appeared at d2.63–2.70
and d2.74–2.86 ppm. The phthalazinone residue showed
the characteristic phthalazinone C8 protons resonated as
doublet at about 8.5 ppm. The mass spectra showed M ,
M?2 and in some cases M?4 fragments in addition to the
characteristic fragmentation pattern. All compounds dis-
played notable peaks at m/z 345 and 343 due to C16H12
BrN2OÁ2? together with the corresponding 1-methylenepi-
perazin-1-ium fragment.
The epoxy bridge of 2 was cleaved by reacting the crude
product with an appropriate N-substituted piperazine in
anhydrous acetonitrile and K2CO3 to give the target com-
pounds 3a–f. In this reaction, the epoxide opening takes
place in a regioselective manner preferentially by terminal
attack of the nucleophile to give the racemic compounds.
The structures of the new targets were established by IR,
1HNMR and mass spectral assignments. The IR spectra
displayed amide C=O stretching bands of phthalazinone
ring system, which are characteristic for all compounds at
1,651–1,654 cm-1. As expected, the stretching bands
The synthesis of S-substituted derivatives 7a–f is shown
in Scheme 2. Chlorination of 1 by phosphorus oxychloride
afforded the 1-chloro derivative 4 (Colotta et al., 1994).
The latter was reacted with thiourea to give the isothio-
uronium intermediate, which upon alkaline hydrolysis
yielded the corresponding thione 5 following procedure
reported for analogous compounds (Badran et al., 2003).
The sodium salt of 5 was stirred with epichlorohydrin in
dimethylsulphoxide to give the intermediate methyloxirane
123

Med Chem Res (2013) 22:1057–1064
1059
Scheme 2 Reagents and
conditions: a POCl3,
Cl
S
O
b H2NCSNH2, c C2H5ONa/
C2H5OH, d epichlorohydrin,
DMSO, 25 °C, e 4-(substituted)
piperazine, CH3CN, K2CO3
N
N
NH
N
N
a
b
N
Br
Br
Br
1
4
5
1) c
2) d
S
S
N
O
N
N
N
N
R
OH
N
e
7 a : R= CH3
Br
7 b : R = C6H5
Br
7 c : R = 4-ClC6H4
7 d: R= 2-OC2H5C6H4
7 e : R= 2-OCH3C6H4
7 f : R= 4-OCH3C6H4
6
7a-f
derivative 6. Subsequent ring opening with the relevant
N-substituted piperazine afforded the target compounds
7a–f.
preparation by 0.71 to 6.18 % of its pre-contracted tension.
Compounds 3b and 3c displayed potentially strong
b-blocking activity by decreasing the isoprenaline-induced
relaxation to 2.2 and 3.2 %, respectively, of pre-contracted
aortic tension compared to 19.75 % of control untreated
aortic ring preparation. However, compounds 7b, 7d and
7f exhibited mild to moderate b-blocking activity by
decreasing the isoprenaline-induced relaxation to 12.05–
15.43 % of pre-contracted aortic tension. On the other
hand, compounds 7a, 7e and 7f did not show tangible
blocking of isoprenaline-induced relaxation. It is worth to
mention that, the compound 3a also strongly inhibited the
NE-induced contraction of the aortic ring preparation to
9.52 % compared to 51.18 % of control untreated prepa-
ration. However, the test compounds 3c, 7d, 7e and 7f
showed similar but weaker inhibition effects to
NE-induced aortic ring contraction (Table 1).
The mass spectrum of 6 showed the characteristic M
1
and M?2 in 1:1 ratio. HNMR of compounds 7a–f dis-
played the characteristic aliphatic protons resonated in the
expected regions.
Pharmacology
Assessment of potential b-blockade
The pharmacological evaluation of the possible b-blocking
activity of the test compounds 3a–f and 7a–f has been
carried out on the norepinephrine (NE)-induced precon-
tracted aortic rings module. Blunting isoprenaline-induced
relaxation was quantified as described in methodology
section. Isoprenaline relaxed the NE-induced precontracted
aortic rings by 19.75 % of the contracted tension. The
reference drug, propranolol not only blunted the isopren-
aline-induced relaxation, but also induced further 1.16 %
contraction in the aortic ring preparation (negative sign
indicates further contraction). Compounds 3a, 3d, 3e and
7c showed the most potent b-blocking activity by complete
blunting and even further contracting the aortic ring
The pharmacological screening revealed that the
N-substituted derivatives 3a–f displayed more potent
b-adrenergic blocking activity than the S-substituted ana-
logues 7a–f. In the first series of compounds, it is obvious
that the compounds with methyl or o-substituted phenyl
groups on the piperazine nitrogen 3a, 3d, 3e showed the
highest b-blocking activity. Moreover, the unsubstituted
and p-chloro substituted analogues 3b, 3c were found to
123

1060
Med Chem Res (2013) 22:1057–1064
determined on Shimadzu IR 435 spectrophotometer (KBr,
1
Table 1 Change in aortic muscle tension after NE and isoprenaline
exposure
cm-1). H NMR spectra were carried out using a Varian
Gemini 200 MHz Spectrophotometer and Varian Mercury-
300 (300 MHz) Spectrophotometer using TMS as internal
standard. Chemical shift values are recorded in ppm on d
scale, Microanalytical Center, Cairo University, Egypt.
Mass spectra were recorded on a GCMP-QP1000 EX Mass
spectrometer, Microanalytical Center, Cairo University,
Egypt. Elemental analyses were carried out at the Micro-
analytical Center, Cairo University, Egypt. Progress of the
reactions was monitored using TLC sheets precoated with
UV fluorescent silica gel Merck 60F 254 using acetone/
benzene (1:9) and were visualized using UV lamp.
2-(4-Bromodbenzoyl)benzoic acids (Yamaguchi et al.,
1993), 4-(4-bromophenyl) phthalazin-1(2H)-ones (1) and
1-chloro-4-(4-bromophenyl)phthalazines (4) (Colotta et al.,
1994) were prepared as reported.
NE-induced change
in aortic muscle
tension (%)
Isoprenaline-induced
change in precontracted
aortic muscle (%)
Control
51.18
63.91
9.52
19.75
-1.16
-6.18
2.2
Propranolol
3a
3b
3c
3d
3e
3f
42.03
31.05
55.2
3.2
-3.87
-0.71
18.01
18.51
12.79
-1.83
12.05
17.4
54.57
47.36
46.6
7a
7b
7c
7d
7e
7f
45.32
42.35
31.55
19.37
18.9
All chemicals were obtained from Aldrich, Fluka, or
Merck chemicals.
15.43
Change in tension is expressed as average muscle tone over duration
of 1–2 min of recording
4-(4-Bromophenyl)-2-(oxiran-2-ylmethyl)phthalazin-
1(2H)-one (2)
possess appreciable b-blocking activity. In contrast, the
p-methoxyphenyl derivative 3f did not show promising
b-blocking effect.
Within the series of S-substituted compounds 7a–f, the
p-chloro-substituted derivative 7c was the only compound
that displayed potent b-adrenergic blockade. Other deriv-
atives showed from weak to moderate activities.
A solution of 1 (1 g, 0.0033 mol) in absolute ethanol
(10 ml)-containing metallic sodium (0.1 g, 0.043 mol) was
heated under reflux for 30 min, then the solvent was dis-
tilled off under reduced pressure. The resulting sodium salt
was dissolved in dimethylsulphoxide (10 ml), epichloro-
hydrin (1.0 g, 0.84 ml, 0.0117 mol) was added and the
mixture was stirred overnight at room temperature. The
precipitated solid was filtered, washed with water, dried
and crystallized from benzene–petrolium ether mixture
(60–80 °C).
Conclusion
Yield 85 %; mp 112–113 °C; IR (KBr) cm-1: 3059
(C–H aromatic), 2927, 2850 (C–H aliphatic), 1658 (C=O);
1HNMR (CDCl3) d ppm: 2.76 (dd, 1H, N–CH2), 2.83 (dd,
1H, N–CH2), 3.41–3.46 (m, 1H, CH-oxiranic), 4.43 (dd,
1H, CH2-oxiranic), 4.46 (dd, 1H, CH2-oxiranic), 7.45 (dd,
2H, Ar–H, J = 8.4 Hz), 7.64 (dd, 2H, Ar–H, J = 8.4 Hz),
7.67–7.80 (m, 3H, Ar–H), 8.50 (d, 1H, Ar–H5); MS (EI)
m/z (% rel. Int.): 358 (M?2, 33.73), 356 (M , 34.81), 315
(14.62), 313 (15.33), 301 (25.36), 299 (24.23), 57 (100).
Anal. Calcd for C17H13BrN2O2, Mwt. (357.20): C, 57.16;
H, 3.67; N, 7.84; Found: C, 57.00; H, 3.35; N, 8.05.
In summary, certain 4-(4-bromophenyl)phthalazine and
phthalazinone derivatives connected through 2-propanol
spacer to N-substituted piperazine residue were synthesized
and screened for their b-adrenergic blocking activity on the
norepinephrine-induced precontracted aortic ring module.
All compounds were obtained and tested as racemates. The
results revealed that N-substituted derivatives 3a–f gener-
ally displayed more potent b-adrenergic blocking activity
than the S-substituted analogues 7a–f. The test compounds
3a, 3d, 3e and 7c showed the most potent b-blocking
activity by complete blunting and even further contracting
the aortic ring preparation by 0.71 to 6.18 % of its pre-
contracted tension.
(R/S)4-(4-Bromophenyl)-2-[2-hydroxy-3-(4-
substitutedpiperazin-1-yl)propyl]- phthalazin-1(2H)-
ones (3a–f)
Experimental
A mixture of 2 (0.0016 mol), anhydrous K2CO3 (0.276 g,
0.002 mol) and few specs of KI in anhydrous acetonitrile
(20 ml) was heated under reflux for 30 min. An appropriate
Melting points were determined on Griffin apparatus
and the values given are uncorrected. IR spectra were
substituted piperazine, (0.002 mol),
commercially
123

Med Chem Res (2013) 22:1057–1064
1061
available, was added to the hot reaction mixture was heated
under reflux for 10 h. After dilution with ice-cold water
(15 ml), the mixture was extracted with dichloromethane
(3 9 10 ml), then the solvent was removed in vacuo to
give the final targets 3a–f. The compounds were purified by
trituration with petroleum ether (60–80 °C), then crystal-
lized from benzene–petroleum ether mixture (60–80 °C).
7.03), 552 (M , 5.57), 345 (10.18), 343 (11.08), 209 (100),
166 (16.15). Anal. Calcd for C27H26BrClN4O2, Mwt.
(553.88): C, 58.55; H, 4.73; N, 10.12; Found: C, 58.26; H,
4.65; N, 10.44.
(R/S)4-(4-Bromophenyl)-2-{2-hydroxy-3-[4-(2-
ethoxyphenyl)piperazin-1-yl]propyl}- phthalazin-
1(2H)-one (3d)
(R/S)4-(4-Bromophenyl)-2-[2-hydroxy-3-(4-
methylpiperazin-1-yl)propyl]-phthalazin-1
(2H)-one (3a)
Yield 50 %; mp 135–136 °C; IR (KBr) cm-1: 3422 (O–H),
3051 (C–H aromatic), 2950, 2816 (C–H aliphatic), 1651
1
(C=O); HNMR (CDCl3) d ppm: 1.44 (t, 3H, CH2CH3),
Yield 60 %; mp 101–102 °C; IR (KBr) cm-1: 3421 (O–H),
3082 (C–H aromatic), 2951, 2823 (C–H aliphatic), 1651
1.60–1.70 (br, 1H, OH, D2O exchangeable), 2.60 (dd, 1H,
N–CH2), 2.64 (dd, 1H, N–CH2), 2.66–2.68 (br, 4H,
piperazine), 2.82–2.86 (br, 4H, piperazine), 3.06–3.11 (m,
2H, CH2N), 4.05 (q, 2H, CH2CH3), 4.32–4.41 (m, 1H, CH–
O), 6.83–7.82 (m, 11H, Ar–H), 8.55 (d, 1H, Ar–H); MS
(EI) m/z (% rel. Int.): 564 (M?2, 12.95), 562 (M , 13.97),
345 (18.63), 343 (18.89). Anal. Calcd for C29H31BrN4O3,
Mwt. (563.49): C, 61.81; H, 5.55; N, 9.94; Found: C,
61.58; H, 5.78; N, 10.24.
1
(C=O); HNMR (DMSO-d6) d ppm: 1.90–2.05 (br, 1H,
OH, D2O exchangeable), 2.44 (s, 3H, CH3), 2.60 (dd, 1H,
N–CH2), 2.64 (dd, 1H, N–CH2), 2.66–2.70 (br, 4H,
piperazine), 2.74–2.80 (br, 4H, piperazine), 3.13–3.16
(m, 2H, CH2N), 4.27–4.34 (m, 1H, CH–O), 7.50–7.90 (m,
7H, Ar–H), 8.36 (d, 1H, Ar–H); MS (EI) m/z (% rel. Int.):
458 (M?2, 0.23), 456 (M , 0.31), 440 (3.83), 438 (3.09),
345 (2.18), 343 (1.86), 113 (100). Anal. Calcd for
C22H25BrN4O2, Mwt. (457.36): C, 57.77; H, 5.51; N,
12.25; Found: C, 57.56; H, 5.62; N, 12.32.
(R/S)4-(4-Bromophenyl)-2-{2-hydroxy-3-[4-(2-
methoxyphenyl)piperazin-1-yl]propyl}- phthalazin-
1(2H)-one (3e)
(R/S)4-(4-Bromophenyl)-2-[2-hydroxy-3-(4-
phenylpiperazin-1-yl)propyl]-phthalazin-1
(2H)-one (3b)
Yield 80 %; mp 160–161 °C; IR (KBr) cm-1: 3433 (O–H),
3059 (C–H aromatic), 2935, 2819 (C–H aliphatic), 1654
(C=O); 1HNMR (CDCl3) d ppm: 1.73–1.82 (br, 1H, OH, D2O
exchangeable), 2.60 (dd, 1H, N–CH2), 2.64 (dd, 1H, N–CH2),
2.66–2.69(br, 4H, piperazine), 2.82–2.86(br, 4H, piperazine),
3.00–3.08 (m, 2H, CH2N), 3.85 (s, 3H, OCH3), 4.32–4.45 (m,
1H, CH–O), 6.84–7.83 (m, 11H, Ar–H), 8.53 (d, 1H, Ar–H);
MS (EI) m/z (% rel. Int.): 550 (M?2, 1.58), 548 (M , 1.75),
345 (1.58), 343 (1.73), 315 (1.14), 313 (1.08), 205 (100). Anal.
Calcd for C28H29BrN4O3, Mwt. (549.46): C, 61.21; H, 5.32;
N, 10.20; Found: C, 61.46; H, 5.25; N, 10.34.
Yield 52 %; mp 95–96 °C; IR (KBr) cm-1: 3421 (O–H),
3066 (C–H aromatic), 2927, 2850 (C–H aliphatic), 1654
(C=O); 1HNMR (DMSO-d6) d ppm: 1.62–1.80 (br, 1H, OH,
D2O exchangeable), 2.61 (dd, 1H, N–CH2), 2.63 (dd, 1H, N–
CH2), 2.66–2.70 (br, 4H, piperazine), 2.75–2.79 (br, 4H,
piperazine), 3.08–3.11 (m, 2H, CH2N), 4.28–4.35 (m, 1H,
CH–O), 7.23–7.80 (m, 12H, Ar–H), 8.51 (d, 1H, Ar–H); MS
(EI) m/z (% rel. Int.): 520 (M?2, 1.72), 518 (M , 1.62), 345
(8.47), 343 (8.29), 315 (1.89), 313 (1.77), 175 (100). Anal.
Calcd for C27H27BrN4O2, Mwt. (519.43): C, 62.43; H, 5.24;
N, 10.79; Found: C, 62.66; H, 5.05; N, 10.45.
(R/S)4-(4-Bromophenyl)-2-{2-hydroxy-3-[4-(4-
methoxyphenyl)piperazin-1-yl]propyl}- phthalazin-
1(2H)-one (3f)
(R/S)4-(4-Bromophenyl)-2-{2-hydroxy-3-[4-(4-
chlorophenyl)piperazin-1-yl]propyl}- phthalazin-
1(2H)-one (3c)
Yield 65 %; mp 122–123 °C; IR (KBr) cm-1: 3426 (O–H),
3100 (C–H aromatic), 2929, 2823 (C–H aliphatic), 1651
1
(C=O); HNMR (CDCl3) d ppm: 1.70–1.85 (br, 1H, OH,
Yield 55 %; mp 175–176 °C; IR (KBr) cm-1: 3429 (O–H),
3082 (C–H aromatic), 2951, 2823 (C–H aliphatic), 1651
D2O exchangeable), 2.59 (dd, 1H, N–CH2), 2.64 (dd, 1H,
N–CH2), 2.66–2.70 (br, 4H, piperazine), 2.77–2.83 (br, 4H,
piperazine), 3.07–3.09 (m, 2H, CH2N), 3.77 (s, 3H, OCH3),
4.34–4.42 (m, 1H, CH–O), 6.82–7.82 (m, 11H, Ar–H), 8.56
(d, 1H, Ar–H); MS (EI) m/z (% rel. Int.): 550 (M?2, 7.29),
548 (M , 6.95), 345 (2.25), 343 (2.49), 205 (100). Anal.
Calcd for C28H29BrN4O3, Mwt. (549.46): C, 61.21; H,
5.32; N, 10.20; Found: C, 61.55; H, 5.65; N, 10.48.
1
(C=O); HNMR (CDCl3) d ppm: 1.62–1.80 (br, 1H, OH,
D2O exchangeable), 2.59 (dd, 1H, N–CH2), 2.61 (dd, 1H,
N–CH2), 2.63–2.66 (br, 4H, piperazine), 2.76–2.80 (br, 4H,
piperazine), 3.13–3.16 (m, 2H, CH2–N), 4.32–4.42 (m, 1H,
CH–O), 6.80–7.82 (m, 11H, Ar–H), 8.53 (d, 1H, Ar–H);
MS (EI) m/z (% rel. Int.): 556 (M?4, 1.93), 554 (M?2,
123

1062
Med Chem Res (2013) 22:1057–1064
4-(4-Bromophenyl)phthalazine-1(2H)-thione (5)
(M-18, 16.01), 342 (22.08), 316 (74.22). Anal. Calcd for
C22H25BrN4OS, Mwt. (473.43): C, 55.81; H, 5.32; N,
11.83; Found: C, 55.65; H, 5.18; N, 11.48.
A mixture of 4 (0.63 g, 0.002 mol) and thiourea (0.23 g,
0.003 mol) was heated under reflux in absolute ethanol
(20 ml) for 3 h. The reaction mixture was allowed to cool
to room temperature and the excess solvent was removed
under diminished pressure. The crude isothiouronium salt
was combined with sodium hydroxide solution (10 %,
20 ml) and the mixture was heated under reflux for 2 h,
cooled to room temperature then acidified with glacial
acetic acid. The resulting orange precipitate was filtered,
washed with water and crystallized from ethanol.
(R/S)1-[4-(4-Bromophenyl)phthalazin-1-ylthio]-3-
(4-phenylpiperazin-1-yl) propan-2-ol (7b)
Yield 75 %; mp 140–141 °C; IR (KBr) cm-1: 3421 (O–H),
3080 (C–H aromatic), 2924, 2845 (C–H aliphatic);
1HNMR (DMSO-d6) d ppm: 1.55–1.60 (br, 1H, OH, D2O
exchangeable), 2.62–2.67 (br, 4H, piperazine), 2.78 (dd,
1H, CH2), 2.82 (dd, 1H, CH2), 3.20–3.25 (br, 4H, pipera-
zine), 3.58 (dd, 1H, CH2), 3.77 (dd, 1H, CH2), 3.85–4.00
(m, 1H, CH–O), 7.59–7.99 (m, 12H, Ar–H), 8.26 (d, 1H,
Ar–H); MS (EI) m/z (% rel. Int.): 534 (M , 7.37), 342
(72.13), 174 (13.64). Anal. Calcd for C27H27BrN4OS, Mwt.
(535.50): C, 60.56; H, 5.08; N, 10.46; Found: C, 60.25; H,
5.35; N, 10.78.
Yield 97 %, mp 229–230 °C; IR (KBr) cm-1: 3100 (C–
1
H aromatic); HNMR (DMSO-d6) d ppm: 7.12–7.88 (m,
8H, Ar–H); MS (EI) m/z (% rel. Int.): 318 (M?2, 100), 316
(M , 98.78). Anal. Calcd for C14H9BrN2S, Mwt. (317.20):
C, 53.01; H, 2.86; N, 8.83; Found: C, 53 05; H, 3.00; N,
8.75.
1-(4-Bromophenyl)-4-(oxiran-2-
(R/S)1-[4-(4-Bromophenyl)phthalazin-1-ylthio]-3-
ylmethylthio)phthalazine (6)
[4-(4-chlorophenyl)piperazin-1-yl]propan-2-ol (7c)
Yield 73 %; mp 158–159 °C; IR (KBr) cm-1: 3425 (O–H),
3062 (C–H aromatic), 2939, 2823 (C–H aliphatic);
1HNMR (CDCl3) d ppm: 1.60–1.70 (br, 1H, OH, D2O
exchangeable), 2.53–2.60 (m, 2H, CH2), 2.65–2.68 (br, 4H,
piperazine), 3.05–3.08 (br, 4H, piperazine), 3.24–3.29 (m,
2H, CH2), 3.98–4.06 (m, 1H, CH–O), 7.10–7.71 (m, 11H,
Ar–H), 8.45 (d, 1H, Ar–H); MS (EI) m/z (% rel. Int.): 566
(M-2, 0.17), 342 (9.51), 340 (11.17), 209 (12.56). Anal.
Calcd for C27H26BrClN4OS, Mwt. (569.94): C, 56.90; H,
4.60; N, 9.83; Found: C, 56.75; H, 4.67; N, 10.12.
The title compound was prepared from 5 and epichloro-
hydrin following the procedure described for the compound
2.
Yield 88 %; mp 101–102 °C; IR (KBr) cm-1: 3062 (C–
H aromatic), 2920, 2850 (C–H aliphatic); 1HNMR (CDCl3)
d ppm: 2.47 (dd, 1H, N–CH2), 2.72 (dd, 1H, N–CH2), 3.26-
3.29 (m, 1H, CH-oxiranic), 3.62 (dd, 1H, CH2-oxiranic),
3.72 (dd, 1H, CH2-oxiranic), 7.19-7.73 (m, 7H, Ar–H);
8.45 (d, 1H, Ar–H); MS (EI) m/z (% rel. Int.): 374 (M?2,
7.19), 372 (M , 7.42), 313 (6.92). Anal. Calcd for
C17H13BrN2OS, Mwt. (373.27): C, 54.70; H, 3.51; N, 7.50;
Found: C, 54.55; H, 3.63; N, 7.88.
(R/S)1-[4-(4-Bromophenyl)phthalazin-1-ylthio]-3-
[4-(2-ethoxyphenyl)piperazin-1-yl]propan-2-ol (7d)
(R/S)1-[4-(4-Bromophenyl)phthalazin-1-ylthio]-3-
Yield 68 %; mp 130–131 °C; IR (KBr) cm-1: 3444 (O–H),
3062 (C–H aromatic), 2931, 2812 (C–H aliphatic);
1HNMR (CDCl3) d ppm: 1.17 (t, 3H, CH2CH3), 1.50–1.57
(br, 1H, OH D2O exchangeable), 2.64 (dd, 1H, CH2), 2.67
(dd, 1H, N–CH2), 2.69–2.72 (br, 4H, piperazine),
2.84–2.88 (br, 4H, piperazine), 3.10–3.17 (m, 2H, CH2N),
4.15 (q, 2H, CH2CH3), 4.23–4.28 (m, 1H, CH–O),
6.98–7.89 (m, 11H, Ar–H), 8.35 (d, 1H, Ar–H); MS (EI) m/z
(% rel. Int.): 578 (M , 11.53), 342 (8.78), 219 (7.40). Anal.
Calcd for C29H31BrN4O2S, Mwt. (579.55): C, 60.10; H,
5.39; N, 9.67; Found: C, 60.34; H, 5.58; N, 9.48.
(4-substitutedpiperazin-1-yl) propan-2-ols (7a–f)
The title compounds were prepared from 6 and an appro-
priate 4-substituted piperazines following the procedure
described for the compounds 3a–f.
(R/S)1-[4-(4-Bromophenyl)phthalazin-1-ylthio]-3-
(4-methylpiperazin-1-yl) propan-2-ol (7a)
Yield 70 %; mp 125–126 °C; IR (KBr) cm-1: 3414 (O–H),
3100 (C–H aromatic), 2924, 2850 (C–H aliphatic);
1HNMR (CDCl3) d ppm: 1.67–1.85 (br, 1H, OH, D2O
exchangeable), 2.41 (s, 3H, CH3), 2.55 (dd, 1H, CH2), 2.58
(dd, 1H, CH2), 2.68–2.73 (br, 4H, piperazine), 2.80–2.84
(br, 4H, piperazine), 3.34–3.42 (m, 2H, CH2), 4.18–4.35
(m, 1H, CH–O), 7.19–7.67 (m, 7H, Ar–H), 8.23 (d, 1H,
Ar–H); MS (EI) m/z (% rel. Int.): 474 (M?2, 14.48), 456
(R/S)1-[4-(4-Bromophenyl)phthalazin-1-ylthio]-3-[4-
(2-methoxyphenyl) piperazin-1-yl]propan-2-ol (7e)
Yield 72 %; mp 125–126 °C; IR (KBr) cm-1: 3440 (O–H),
3062 (C–H aromatic), 2931, 2816 (C–H aliphatic);
123

Med Chem Res (2013) 22:1057–1064
1063
1HNMR (CDCl3) d ppm: 1.50–1.61 (br, 1H, OH, D2O
exchangeable), 2.62–2.66 (m, 2H, CH2), 2.70–2.74 (br, 4H,
piperazine), 2.81–2.85 (br, 4H, piperazine), 3.10–3.16
(m, 2H, CH2N), 3.77 (s, 3H, OCH3), 4.33–4.42 (m, 1H,
CH–O), 7.16–7.80 (m, 11H, Ar–H), 8.55 (d, 1H, Ar–H); MS
(EI) m/z (% rel. Int.): 566 (M?2, 19.75), 564 (M , 16.02).
Anal. Calcd for C28H29BrN4O2S, Mwt. (564.12): C, 59.47;
H, 5.17; N, 9.91; Found: C, 59.35; H, 5.05; N, 10.26.
The isolated aortic ring was mounted in 10 ml water
jacketed automatic multi-chamber organ bath system
(Model no. ML870B6/C, Panlab, Spain). The organ bath
contained Krebs’ solution of the following composition
(g/l): NaCl 6.9, KCl 0.35, KH2PO4 0.16, MgSO4Á7H2O 0.3,
CaCl2Á2H2O 0.37, NaHCO3 2.1 and glucose 1.05. The organ
bath solution was continuously aerated with carbogen
(a mixture of 95 % O2 and 5 % CO2) and its temperature was
kept at 37 °C. The preparation was allowed to equilibrate for
about 120 min under a resting tension of 2 g. During that
time any change in the resting tension was readjusted. The
aortic ring was contracted by norepinephrine (10 M-6) then
relaxed by exposure to b-agonist, isoprenaline (10 M-6).
Pre-exposure of the aortic ring to b-blocker is supposed to
suppress isoprenaline- induced aortic relaxation. Percent
change in aortic tension after isoprenaline treatment was
calculated for compounds under investigation (10 M-6) and
compared to standard b-blocker, propranolol (10 M-6).
Change in aortic tension was recorded and calculated over a
period of one minute and average tension was used for
calculation (Girgis et al., 2010).
(R/S)1-[4-(4-Bromophenyl)phthalazin-1-ylthio]-3-
[4-(4-methoxyphenyl) piperazin-1-yl]propan-2-ol (7f)
Yield 80 %; mp 150–151 °C; IR (KBr) cm-1: 3421 (O–H),
3062 (C–H aromatic), 2985, 2866 (C–H aliphatic);
1HNMR (CDCl3) d ppm: 1.58–1.65 (br, 1H, OH, D2O
exchangeable), 2.35–2.40 (m, 2H, CH2), 2.55–2.62 (br, 4H,
piperazine), 2.85–2.95 (br, 4H, piperazine), 3.35–3.42 (m,
2H, CH2), 3.64 (s, 3H, OCH3), 4.12–4.30 (m, 1H, CH–O),
6.85–7.80 (m, 11H, Ar–H), 8.25 (d, 1H, Ar–H); MS (EI)
m/z (% rel. Int.): 566 (M?2, 10.36), 360 (6.72), 343 (55.39),
205 (11.48), 193 (22.04). Anal. Calcd for C28H29BrN4O2S,
Mwt. (564.12): C, 59.47; H, 5.17; N, 9.91; Found: C, 59.58;
H, 5.26; N, 9.65.
Acknowledgments The authors are grateful to Dr. Wafaa El-Eraky,
Associate Professor of Pharmacology and Toxicology Department,
National Research Center, Cairo, Egypt for carrying out the biological
studies.
Assessment of potential b-blocking activity
Drugs and chemicals Norepinephrine hydrochloride (NE)
and isoprenaline were purchased from Sigma-Aldrich
(St Louis, MO, USA). All other chemicals were of the
highest commercially available grade.
References
Badran MM, Abouzid KAM, Hussein MH (2003) Synthesis of certain
substituted quinoxalines as antimicrobial agents (Part II). Arch
Pharm Res 26:107–113
Laboratory animals Adult male albino rats, weighing
180–250 g, were used in all the experiments of this study.
They were obtained from the Animal House Colony of the
National Research Center (Dokki, Giza, Egypt), and were
housed under conventional laboratory conditions through-
out the period of experimentation. The animals were fed a
standard rat pellet diet and allowed free access to water. All
the experimental techniques were approved by the ethical
committee of the National Research Center.
Bansal R, Kumar D, Rosalia Carron R, De la Calle C (2009) Synthesis
and vasodilatory activity of some amide derivatives of 6-(4-
carboxymethyloxphenyl)-4,5-dihydro-3(2H)-pyridazinone. Eur J
Med Chem 44:4441–4447
Bisi A, Rampa A, Budriesi R, Gobbi S, Belluti F, Ioan P, Valoti E,
Chiarini A, Valenti P (2003) Cardiovascular hybrid drugs: new
benzazepinone derivatives as bradycardiac agents endowed with
selective b1-non competitive antagonism. Bioorg Med Chem
11:1353–1361
Carella AM, Antonucci G, Conte M, Di-:Pumpo M, Giancola A,
Antonucci E (2010) Antihypertensive treatment with beta-
blockers in the metabolic syndrome: a review. Curr Diabetes
Rev 6:215–221
Isolation and suspension of rat aortic rings Rats were
euthanized by cervical dislocation and the thoracic aorta
was carefully exposed and isolated. The isolated aorta was
cut into rings (3–5 mm width) and each ring was then
vertically mounted between two stainless steel hooks pas-
sed through its lumen. The lower hook was fixed between
two plates, while the upper one was attached to a force
displacement transducer (Model no. MLT0201, Panlab,
Spain) connected to an amplifier (Power Lab, AdInstru-
ments Pty. Ltd.) which is connected to a computer. The
chart for windows (v 3.4) software was used to record and
elaborate data.
Colotta V, Cecchi L, Catarzi D, Filacchioni G, Galli A, Mori F (1994)
Synthesis and structure-activity relationships of 1-aminophtha-
lazinium salts as GABA 318 A receptor antagonists. Eur J Med
Chem 29:95–105
Del Olmo E, Barboza B, Ybarra M, Lopez-Perez JL, Carron R,
Sevilla A, Boselli C, San Feliciano A (2006) Vasorelaxant
activity of phthalazinones and related compounds. Bioorg Med
Chem Lett 16:2786–2790
Demirayak S, Karaburun AC, Kayagil I, Erol K, Sirmagul B (2004a)
Some pyridazinone and phthalazinone derivatives and their
vasodilator activities. Arch Pharm Res 27:13–18
Demirayak S, Karaburun AC, Beis
R (2004b) Some pyrrole
substituted aryl pyridazinone and phthalazinone derivatives and
their antihypertensive activities. Eur J Med Chem 39:1089–1095
123

1064
Med Chem Res (2013) 22:1057–1064
Girgis AS et al (2010) Regioselective synthesis and molecular
modeling study of vasorelaxant active 7,9-dioxa-1,2-diaza-
spiro[4.5]dec-2-ene-6,10-diones. Eur J Med Chem 45:4229–
4238
Matsuda Y, Akita H, Terashima M, Shiga N, Kanazawa K,
Yokohama M (2000) Carvediol improves endothelium-depen-
dent dilatation in patients with coronary artery disease. Am Heart
J 140:753–759
Gonec T, Racanska E, Csollei J (2008) Synthesis of 2-{3-[4-(4-
fluorophenyl)-1-piperazinyl]-2-hydroxy-propoxy}phenylcarba-
mic acid alkylesters and in vitro evaluation of their b-adrenergic
and vasodilatative activities. Ces Slov Farm 57:115–118
Lopez AD, Mathers CD, Ezzati M, Jamison DT, Murray CJL (2006)
Global and regional burden of disease and risk factors, 2001:
systematic analysis of population health data. Lancet 367:1747–
1757
Macchia B, Balsamo A, Lapucci A, Martinelli A, Macchia F, Breschi
MC, Fantoni B, Martinotti E (1985) An interdisciplinary
approach to the design of new structures active at the
b-adrenergic receptor. Aliphatic oxime ether derivatives.
J Med Chem 28:153–160
Panjrath GS, Messerli FH (2006) Beta-blockers for primary preven-
tion in hypertension: era bygone? Prog Cardiovasc Dis 49:76–87
Racanska E, Maruniak M, Tumova I, Sedlarova E (2010) In vitro
pharmacological evaluation of new phenylpiperazine derivatives
of phenylcarbamic acid on their basic cardiovascular functions.
Acta Fac Pharm Univ Com LVII:1–9
Saccomanni G, Badawneh M, Adinolfi B, Calderone V, Cavallini T,
Ferrarini PL, Greco R, Manera C, Testai L (2003) Synthesis and
b-blocking activity of (R,S)-(E)-oximeethers of 2,3-dihydro-1,8-
naphthyridine and 2,3-dihydrothiopyrano[2,3-b]pyridine: identi-
fication of b3-antagonists. Bioorg Med Chem 11:4921–4931
Toda N (2003) Vasodilating beta-adrenoceptor blockers as cardio-
vascular therapeutics. Pharmacol Ther 100:215–234
Marona H, Szkaradek N, Kubacka M, Bednarski M, Filipek B, Cegla
M, Szneler E (2008) Synthesis and evaluation of some xanthone
derivatives for anti-arrhythmic, hypotensive properties and their
affinity for adrenergic receptors. Arch Pharm (Weinheim) 341:
90–98
Yamaguchi M, Kamei K, Koga T, Akima M, Kuroki T, Ohi N (1993)
Novel antiasthmatic agents with dual activities of thromboxane
A2 synthetase inhibition and bronchodilation. 2-[2-(1-Imidazo-
lyl)alkyl]-1(2H)-phthalazinones. J Med Chem 36:4052–4060
123