Synthesis and antiinflammatory activity of certain benzothieno[3,2-d][1,2, 4]triazolo[4,3-b] pyridazine derivatives

Article abstract of DOI:10.1007/s00044-011-9847-2

6-Bromo-4-chloro-1-hydrazinobenzothieno[2,3-d] pyridazine (1) was selected as the starting material for the synthesis of some novel fused benzothienotriazolopyridazine derivatives 2-16. Thus, compound 1 was reacted with carbon disulfide, ethyl orthoformate, acetic anhydride, or 2-methoxybenzaldehyde followed by cyclization with bromine, to give the corresponding benzothienotriazolopyridazines 2-6. Nucleophilic substitution of the 6-chloro with piperidine, N-methyl piperazine, hydrazine hydrate, or potassium hydroxide afforded 6-substituted benzothieno[3,2-d][1,2,4]triazolo[4, 3-b] pyridazines 7-16. The structures of the synthesized compounds were elucidated by elemental analysis and spectral data. All the newly synthesized compounds were subjected to evaluation for their antiinflammatory activity against carrageenaninduced paw edema at a dose of 10 mg/kg using indomethacin as the reference standard. Compounds 11 and 13 (6-hydrazinyl derivatives) significantly reduced the edema to 52.8 and 78.7%, respectively, as compared with indomethacin (50.5%). Springer Science+Business Media, LLC 2011.

Full text of DOI:10.1007/s00044-011-9847-2

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:3146–3153
DOI 10.1007/s00044-011-9847-2
ORIGINAL RESEARCH
Synthesis and antiinflammatory activity of certain
benzothieno[3,2-d][1,2,4]triazolo[4,3-b] pyridazine derivatives
•
Ashraf F. A. Zaher Omneya M. Khalil
•
Hanan M. Refaat
Received: 19 May 2011 / Accepted: 25 October 2011 / Published online: 11 November 2011
Ó Springer Science+Business Media, LLC 2011
Abstract 6-Bromo-4-chloro-1-hydrazinobenzothieno[2,3-d]
pyridazine (1) was selected as the starting material for the
synthesis of some novel fused benzothienotriazolopyr-
idazine derivatives 2–16. Thus, compound 1 was reacted
with carbon disulfide, ethyl orthoformate, acetic anhydride,
or 2-methoxybenzaldehyde followed by cyclization with
bromine, to give the corresponding benzothieno-
triazolopyridazines 2–6. Nucleophilic substitution of the
6-chloro with piperidine, N-methyl piperazine, hydrazine
hydrate, or potassium hydroxide afforded 6-substituted
benzothieno[3,2-d][1,2,4]triazolo[4,3-b] pyridazines 7–16.
The structures of the synthesized compounds were eluci-
dated by elemental analysis and spectral data. All the
newly synthesized compounds were subjected to evaluation
for their antiinflammatory activity against carrageenan-
induced paw edema at a dose of 10 mg/kg using indo-
methacin as the reference standard. Compounds 11 and 13
(6-hydrazinyl derivatives) significantly reduced the edema
to 52.8 and 78.7%, respectively, as compared with indo-
methacin (50.5%).
privileged structure in medicinal chemistry encompassing a
diverse range of biological activities including potent and
selective phosphodiesterase IV inhibitor (Dal Piaz et al.,
1997), immunosuppressants (Bantick et al., 1999), anti-
asthmatic (Yamaguchi et al., 1995), antiinflammatory
(Pieretti et al., 2006), antibacterial, antifungal (Singh et al.,
2005), anticonvulsant (Fischer et al., 1987), antispasmodic
(Robev et al., 1984), and antitumour activities (Dumas
et al., 2001, Wu, 2009). Previously, a number of pre-
parative methods for benzothieno[3,2-d]pyridazines syn-
theses were elaborated, however, their pharmacolological
properties were not investigated (Bezdrik et al., 1908;
Charles and Frederick 1945; Dore et al., 1972a, b, c, 1973a,
b; Guha and Mitra, 1966; Huntress and Hearon 1941;
Kamal El-Dean et al., 2004; Linstead et al., 1937). We
have recently developed a synthesis of the new building
block 6-Bromo-4-chloro-1-hydrazinobenzothieno[2,3-d]
pyridazine 1 through a series of steps and studied its
application for the preparation of some fused tetrazolo- and
triazinobenzothienopyridazine derivatives (Fig. 1) (Zaher
et al., 2009). Here, we communicate our new results on the
application of 1 for the preparation of fused triazolo-
benzothienopyridazines bearing chloro moiety located at
the 6-position. This electrophilic center made these syn-
thons versatile building blocks for the further preparation
of certain 6-substituted triazolobenzothienopyridazines of
anticipated antiinflammatory activity.
Keywords Benzothieno[3,2-d][1,2,4]triazolo
[4,3-b]pyridazines Á Antiinflammatory activity
Introduction
Thienopyridazine derivatives have been reported to be
physiologically and pharmacologically active and they
gained much attention as important pharmacophore and
Results and discussion
Chemistry
A. F. A. Zaher Á O. M. Khalil Á H. M. Refaat (&)
Organic Chemistry Department, Faculty of Pharmacy,
Cairo University, Kasr El-Eini Street, Cairo 11562, Egypt
e-mail: hanan-refaat@hotmail.com
Our interest in developing synthetic approaches with a
view to synthesize new 8-bromobenzothieno[3,2-d][1,2,4]
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3147
Fig. 1 Synthesis of
6-Bromo-4-chloro-1-
hydrazinobenzothieno[2,3-d]
pyridazine (1)
O
N
O
CH3
CH3
ON
N
Me
Me
S
N
S
Br
Br
II
I
15% HCl
COCOOH
O
i) NaOH
ii) ClCH2COOH, NaOH
SCH2COOH
S
O
+
iii) H
Br
Br
III
IV
i) 50% NaOH
+
ii) H
O
i) 43% N2H4
ii) H2SO4 /
COOH
(Ac)2O
O
S
S
COOH
O
Br
Br
V
Cl
Cl
OH
N
N
POCl3
N
N
VII
S
S
N
Br
Br
OH
N2H4 / EtOH
VI
NHNH2
N
N
S
Br
Cl
1
triazolo[4,3-b]pyridazine derivatives 2–16, the 4-chloro-1-
hydrazinobenzothieno[2,3-d] pyridazine 1 (Zaher et al.,
2009), was thus investigated as a good starting material for
this purpose. 7-Bromo-2-(4-dimethylaminophenylimino)
benzothiophen-3-one II (Zaher et al., 2009) was produced
through the condensation of 6-Bromobenzothiophene-3-
one I (Guha and Mitra, 1966; Charles and Frederick 1945)
with p-nitroso-N,N-dimethylaniline (Bezdrik et al., 1908),
acid hydrolysis of II gave 6-bromobenzothiophene 2,3-di-
ones III (Zaher et al., 2009). Reaction of compound III
with chloroacetic acid in sodium hydroxide solution
afforded S-(6-bromo-2-oxalophenyl)thioglycolic acid IV
(Zaher et al., 2009), and subsequent cyclization of IV with
50% aqueous sodium hydroxide provided 7-bromobenzo-
thiophene-2,3-dicarboxylic acid V (Zaher et al., 2009). The
latter was refluxed with acetic anhydride to give the acid
anhydride intermediate which was then warmed with
hydrazine hydrate, then acidified with sulfuric acid to
produce the target 6-bromo-1,2,3,4-tetrahydrobenzothie-
no[2,3-d] pyridazine 1,4-dione VI (Zaher et al., 2009).
Chlorination of the 1,4-dione VI with phosphorus oxy-
chloride in pyridine afforded the 1,4-dichloro derivative
VII (Zaher et al., 2009). Hydrazinolysis of compound VII
produced the 1-hydrazino derivative 1 (Zaher et al., 2009).
Treatment of compound 1 with carbon disulfide, ethyl
orthoformate, or acetic anhydride gave the 3-sulphanyl
triazolo 2, triazolo 3, and 3-methyl triazolo 4 derivatives,
respectively (Scheme 1). The IR spectra of compound 2
showed the characteristic C=S stretching absorption at d
1,220 and 1,410 cm-1, while the 1H-NMR spectrum of
compound 3 displayed the appearance of C3H absorption at
d 9.79 ppm. Whereas the 1H-NMR spectrum of compound
4 displayed a singlet signal at d 1.22 ppm corresponding to
CH3. On the other hand, reaction of compound 1 with an
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Med Chem Res (2012) 21:3146–3153
equimolar amount of 2-methoxybenzaldehyde in 0.1 N
hydrochloric acid at 60°C afforded the derivative 5,
which was cyclized by bromine in acetic acid to give
3-(2-methoxyphenyl)8-bromo-6-chloro benzothieno[3,2-
d][1,2,4]triazolo[4,3-b] pyridazine 6. The 1H-NMR spectra
of compound 6 displayed the disappearance of N=CH
absorption of the precursor 5. The mass spectrum of
compound 6 showed molecular ion at m/z 444 and M ? 1
for 13C at m/z 445. An intense peak at m/z 446 indicated the
isotope peak for 37Cl, 81Br, or 34S in addition to the pres-
ence of M ? 2 ? 1 for 13C at m/z 447 and M ? 4 indi-
cating the isotopes 37Cl, 81Br, and/or 34S. The molecular
ions M ? 4, M ? 2, M? and the respective M ? 3 and
M ? 1 lost 35Cl and/or 37Cl to give the corresponding
peaks at 412, 411 (base beak), 410, and 409. The latter
molecular ions lost N2 to give peaks at m/z 384, 383, 482,
and 381, respectively.
activity for further structural modification to enhance anti-
inflammatory activity.
Experimental
Chemistry
Melting points were obtained on a Griffin apparatus and are
uncorrected. Microanalyses for C, H, and N were carried
out at the Microanalytical Center, Cairo University. IR
spectra were recorded on a Shimadzu 435 spectrometer,
1
using KBr disks. H-NMR spectra were performed on a
Joel NMR FXQ-200 MHz spectrometer, using TMS as the
internal standard and DMSO-d6 as solvent.
Mass spectra were recorded on a GCMP-QP1000 EX
Mass spectrometer. Progress of the reactions were moni-
tored by TLC using precoated aluminum sheet silica gel
MERCK 60F 254 and were visualized by UV lamp.
Attention was next turned to the nucleophilic substitution
of the 6-chloro with piperidine, N-methyl piperazine,
hydrazine hydrate, and potassium hydroxide to produce
6-substituted benzo thieno [3,2-d] [1,2,4] triazolo [4,3-b]
pyridazines 7–16 (Scheme 2). The 1H-NMR spectra of
compounds 7–16 were consistent with the proposed struc-
tures. The mass spectrum of compound 8 showed molecular
ion at m/z 402 and M ? 1 for 13C at m/z 403. Also, a peak at
m/z 404 indicated the isotope peak for 81Br or 34S in addi-
tion to the presence of M ? 2 ? 1 for 13C at m/z 405 and
M ? 4 at m/z 406 indicating the isotopes 81Br and 34S. The
molecular ions M ? 4, M ? 2, M? and the respective
M ? 3 and M ? 1 lost methylpiperazine, then either lost
N2 followed by the loss of HCN or the reverse, to give the
corresponding peaks at 252, 251, 250, 249, and 248
(C10H3BrN3S). In a similar way, the mass spectrum of
compound 9 showed molecular ion peaks and the sub-
sequent loss of piperidine (base peak), CH3CN, and then N2.
8-Bromo-6-chloro-3-sulphanyl benzothieno[3,2-
d][1,2,4]triazolo[4,3-b] pyridazine (2)
To a suspension of 4-chloro-1-hydrazinobenzothieno[2,3-
d]pyridazine 1 (0.46 g, 0.0014 mol) in absolute methanol
(20 ml), potassium hydroxide (0.168 g, 0.003 mol) and
carbon disulfide (2.28 g, 0.03 mol) were added. The reac-
tion mixture was heated under reflux for 5 h, and then the
solvent was distilled off under reduced pressure. The res-
idue was dissolved in 10% aqueous potassium hydroxide
(100 ml) and filtered. The filtrate was neutralized to litmus
with 10% hydrochloric acid and the separated solid washed
with water, dried, and crystallized from isopropanol.
Yield: 45.0%; mp: [300°C; IR (cm-1): 3200–2500
1
(NH/SH), 1610 (C=N) and 1220, 1410 (C=S); H-NMR: d
7.62 (t, 1H, J = 7.6 Hz, C10H), 7.92 (d, 1H, J = 7.6 Hz,
C9H), 8.63 (d, 1H, J = 7.6 Hz, C11H), 14.70 (br s, 1H, NH,
D2O exchangeable). Anal. Calcd. for C11H4BrClN4S2
(371.65): C, 35.54; H, 1.08; N, 15.07. Found: C, 35.61; H,
1.11; N, 15.20.
Antiinflammatory activity
All the newly synthesized compounds were subjected to
preliminary testing for their antiinflammatory activity in
comparison with the reference drug, indomethacin. The
percentage reduction in the inflammation (i.e., reduction in
the right hand paw volume of the animal) 3 h after
administration of carrageenan was recorded. Only com-
pounds 10, 11, 13, and 14 produced a reduction in edema
volume compared with the control, compounds 11 and 13
(6-hydrazinyl derivatives) significantly reduced the edema
to 52.8 and 78.7%, respectively. The percentage inhibition
of edema produced by indomethacin was 50.5% (Fig. 2).
These results suggested that the incorporation of a triazole
ring in the benzothienopyridazine system together with
proper substitution, for example, 6-hydrazinyl provides a
new promising scaffold with moderate antiinflammatory
8-Bromo-6-chlorobenzothieno[3,2-d][1,2,4]
triazolo[4,3-b]pyridazine (3)
Compound 1 (0.46 g, 0.0014 mol) was heated under reflux
with triethyl orthoformate (5 ml) for 3 h then cooled. The
separated solid was filtered, washed with methanol, dried,
and crystallized from isopropanol. Yield: 55.0%; mp: 240–
1
242°C; IR (cm-1): 1640 (C=N); H-NMR: d 7.55 (t, 1H,
J = 7.8 Hz, C10H), 7.86 (d, 1H, J = 7.8 Hz, C9H), 8.60 (d,
1H, J = 7.8 Hz, C11H), 9.79 (s, 1H, C3H). Anal. Calcd. for
C11H4BrClN4S (339.59): C, 38.90; H, 1.18; N, 16.49.
Found: C, 39.20; H, 1.10; N, 16.60.
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Med Chem Res (2012) 21:3146–3153
3149
N
N
CS2
N
N
SH
S
Br
Cl
N
2
N
(C2H5O)3CH
N
N
S
Br
Cl
NHNH2
3
N
N
S
Br
Cl
N
N
1
(CH3CO)2O
N
CH3
N
S
Br
Cl
4
H3CO
CH
HN-N=
OCH3
CHO
N
N
S
Br
Cl
5
OCH3
N
N
N
N
S
Br
Cl
6
Scheme 1 Synthesis of compounds 2–6
8-Bromo-6-chloro-3-methylbenzothieno[3,2-d]
[1,2,4]triazolo[4,3-b] pyridazine (4)
the residue was crystallized from isopropanol. Yield: 50.0%;
mp: 234–236 °C; IR (cm-1): 2900 (aliph H) and 1640
(C=N); 1H-NMR: d 1.19 (s, 3H, CH3), 7.63 (m, 1H, C10H),
7.92 (d, 1H, J = 7.7 Hz, C9H), 8.67 (d, 1H, J = 8.1 Hz,
C11H). Anal. Calcd. for C12H6BrClN4S (353.62): C, 40.75;
H, 1.71; N, 15.84. Found: C, 41.10; H, 1.65; N, 16.00.
A mixture of compound 1 (0.46 g, 0.0014 mol) and acetic
anhydride (2 ml) was heated under reflux for 3 h. The excess
acetic anhydride was distilled under diminished pressure and
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Med Chem Res (2012) 21:3146–3153
N
N
Z
HN
N
N
R
S
Br
N
Z
7-10
N
N
N
N
R
N
N
S
NH2NH2
N
R
Br
Cl
N
S
Br
NHNH2
3,4,6
11-13
N
N
KOH
N
N
R
S
Br
OH
14-16
7
8
9
R = H, Z = CH2
R = H, Z = N-CH3
R = CH3, Z = CH2
3,11,14 R = H
4,12,15 R = CH3
6,13,16 R = 2-OCH3-C6H4
10 R = 2-OCH3-C6H4, Z = CH2
Scheme 2 Synthesis of compounds 7–16
8-Bromo-4-chloro-1-(2-methoxyphenyl
aqueous sodium hydroxide solution and the precipitate was
filtered, washed with water, and then crystallized from
isopropanol.
hydrazino)benzothieno[2,3-d] pyridazine (5)
Yield: 90.0%; mp: 205–207°C; IR (cm-1): 3400 (NH),
To a solution of compound 1 (0.46 g, 0.0014 mol) in 0.1 N
hydrochloric acid (10 ml), 2-methoxybenzaldehyde
(0.136 g, 0.001 mol) was added portionwise and the mix-
ture was kept at 60°C with stirring for 10 min. The cold
reaction mixture was neutralized to litmus with 10%
1
2900 (aliph H) and 1640 (C=N); H-NMR: d 3.72 (s, 3H,
OCH3), 7.01–7.17 (m, 3H, 2ArH ? NH), 7.51 (t, 1H,
C10H), 7.69–7.79 (m, 2H, ArH), 7.81 (d, 1H, J = 7.6 Hz,
C9H), 7.98 (d, 1H, J = 7.6 Hz, C11H), 8.94 (s, 1H,
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3151
Fig. 2 Anti-inflammatory
activity of compounds 10, 11,
13, and 14 expressed as %
Inhibition of edema
N = CH). Anal. Calcd. for C18H12BrClN4OS (447.73): C,
48.28; H, 2.70; N,12.51. Found: C, 48.40; H, 2.50; N,
12.60.
filtered, washed with ethanol, and crystallized from the
suitable solvent.
8-Bromo-6-piperidin-1-ylbenzothieno[3,2-
d][1,2,4]triazolo[4,3-b] pyridazine (7)
8-Bromo-3-(2-methoxyphenyl)-6-
chlorobenzothieno[3,2-d][1,2,4]triazolo[4,3-b]
pyridazine (6)
Yield: 72.0%; mp: 218–220°C; IR (cm-1): 2,900 (aliph H)
and 1,590 (C=N); 1H-NMR: d 1.14–1.21 (m, 4H, piperidine
H3,5), 1.41–1.44 (m, 2H, piperidine H4), 4.37–4.38 (m, 4H,
To a mixture of 5 (0.44 g, 0.001 mol), sodium acetate
(0.25 g, 0.003 mol) and acetic acid (9 ml), bromine
(0.16 g, 0.001 mol) in acetic acid (0.6 ml) was added
dropwise while stirring at room temperature over a period
of 1 h. The reaction mixture was then poured into cold
water (50 ml), and the separated solid was filtered, washed
with 10% aqueous sodium bisulfite solution (2 9 2 ml),
then with water (20 ml), dried, and crystallized from iso-
propanol. Yield: 80.0%; mp: 250–252°C; IR (cm-1): 1620
(C=N); 1H-NMR: d 3.84 (s, 3H, OCH3), 7.01–7.21 (m, 2H,
ArH), 7.79 (m, 1H, C10H), 8.14 (m, 2H, ArH), 8.28 (m, 1H,
C9H), 8.88 (m, 1H, C11H); MS m/z: 448 (M ? 4, 17.55%),
447 (M ? 3, 15.81%), 446 (M ? 2, 44.22%), 445 (M ? 1,
21.31%), 444 (M?, 30.92%), 412 (M ? 3-35Cl, 23.23%),
411 (M ? 4-37Cl and M ? 2-35Cl, 100%), 410
(M ? 3-37Cl and M ? 1-35Cl, 22.04%), 409 (M ? 2-37Cl
and M?-35Cl, 98.11%), 384, 383, 382, 381 (C18H10
BrN2OS, 29.94, 11.80, 35.20, 28.17%). Anal. Calcd. for
C18H10BrClN4OS (445.71): C, 48.50; H, 2.26; N, 12.57.
Found: C, 48.71; H, 2.30; N, 12.80.
piperidine H2,6), 7.60–7.65 (m, 1H, C10H), 7.92 (d, 1H,
C9H), 8.70 (d, 1H, C11H), 8.81 (s, 1H, C3H). Anal. Calcd.
for C16H14BrN5S (388.28): C, 49.49; H, 3.63; N, 18.03.
Found: C, 49.60; H, 3.60; N, 18.00.
8-Bromo-6-(4-methylpiperazin-1-yl)benzothieno[3,2-
d][1,2,4]triazolo[4,3-b] pyridazine (8)
Yield: 79.0%; mp: 295–297°C; IR (cm-1): 2,900 (aliph H)
and 1,590 (C=N); MS m/z: 406 (M ? 4, 0.48%), 405
(M ? 3, 1.53%), 404 (M ? 2, 6.66%), 403 (M ? 1,
3.08%), 402 (M?, 6.66%), 307, 306, 305, 304, 303
(C11H4BrN4S = M ? 4, M ? 3, M ? 2, M ? 1 and
M?-C5H11N2, 0.42, 1.55, 1.83, 1.72, 1.37%), 280, 279,
278, 277, 276, 275 (C11H4BrN2S and/or C10H3
BrN3S=C11H4BrN4S–N2 or –HCN, 0.39, 0.78, 1.23, 1.41,
1.25, 0.97%), 252, 251, 250, 249, 248 (C10H3BrNS=C11
H4BrN2S–HCN and/or C10H3BrN3S–N2, 0.97,1.41, 1.18,
2.33. 0.80%), 70 (C2NS, 100%). Anal. Calcd. for
C16H15BrN6S (403.29): C, 47.65; H, 3.74; N, 20.83. Found:
C, 47.50; H, 3.72; N, 21.00.
General procedure for the preparation of compound
7–12
8-Bromo-6-piperidin-1-yl-3-methylbenzothieno[3,2-d]
[1,2,4]triazolo[4,3-b] pyridazine (9)
To a suspension of the appropriate 8-bromo-4-chlor-
obenzothieno[3,2-d] [1,2,4]triazolo[4,3-b]pyridazine 3, 4,
or 6, (0.001 mol) in n-butanol (10 ml), the appropriate
secondary amine (0.001 mol), and triethyl amine (2-3
drops) were added. The reaction mixture was heated under
reflux for 4 h. After cooling the separated solid was
Yield: 82.0%; mp: 234–236°C; IR (cm-1): 2,900 (aliph H)
and 1,600 (C=N); 1H-NMR: d 1.23 (s, 1H, CH3), 1.55–1.73
(m, 6H, piperidine H3,4,5), 3.55–3.56 (m, 4H, piperidine
H
2,6), 7.69 (t, 1H, J = 7.8 Hz, C10H), 7.97 (d, 1H,
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Med Chem Res (2012) 21:3146–3153
J = 7.8 Hz, C9H), 8.80 (d, 1H, J = 7.8 Hz, C11H); MS m/
z: 405 (M ? 4, 3.59%), 404 (M ? 3, 12.15%), 403
(M ? 2, 55.95%), 402 (M ? 1, 18.74%), 401 (M?,
53.97%), 321, 320, 319, 318, 316 (C12H6BrN4S = M ? 4,
M ? 3, M ? 2, M ? 1 and M?-C5H11N or –C5H10N,
28.45, 45.54, 27.18, 41.77, 3.62%), 280, 279, 278, 277, 276
(C10H3BrN3S=C12H6BrN4S–CH3CN, 3.33 4.01, 3.97, 4.49,
3.69%), 252, 251, 250, 250, 249, 248 (C10H3BrNS=C10
H3BrN3S–N2, 4.27, 6.41, 6.16, 5.43, 2.55%), 85 (C5H11N,
12.98%) and 84 (C5H10N, 100%). Anal. Calcd. for
C17H16BrN5S (402.30): C, 50.75; H, 4.00; N, 17.40. Found:
C, 50.60; H, 4.10; N, 17.35.
(m, 1H, C9H), 8.86 (m, 1H, C11H). Anal. Calcd. for
C18H13BrN6OS (441.30): C, 48.98; H, 2.96; N, 19.04.
Found: C, 49.20; H, 2.93; N, 18.90.
8-Bromo-6-hydroxybenzothieno[3,2-d][1,2,4]triazolo
[4,3-b]pyridazine (14)
Yield: 72.0%; mp: [300°C; IR (cm-1): 3257–3361 (OH),
1
2850 (aliph H) and 1590 (C=N); H-NMR: d 7.59 (t, 1H,
J = 7.8 Hz, C10H), 7.82 (d, 1H, J = 7.8 Hz, C9H), 8.62 (d,
1H, J = 7.8 Hz, C11H), 8.73 (s, 1H, C3H), 9.15 (s, 1H, OH,
D2O exchangeable). Anal. Calcd. for C11H5BrN4OS
(321.14): C, 41.13; H, 1.56; N, 17.44. Found: C, 40.90; H,
1.56; N, 17.50.
8-Bromo-3-(2-methoxyphenyl)-6-piperidin-1-yl
benzothieno[3,2-d][1,2,4]triazolo[4,3-b] pyridazine (10)
8-Bromo-6-hydroxy-3-methylbenzothieno
[3,2-d][1,2,4]triazolo[4,3-b] pyridazine (15)
Yield: 65.0%; mp: 238–240°C; IR (cm-1): 2900 (aliph H)
and 1610 (C=N); H-NMR: d 1.22 (br s, 4H, piperidine
1
H
3,5), 1.89 (br s, 2H, piperidine H4), 3.82 (br s, 4H,
Yield: 69.0%; mp: \300°C; IR (cm-1): 3290-3400 (OH),
1
piperidine H2,6), 3.87 (s, 3H, OCH3), 7.04–7.21 (m, 2H,
ArH), 7.62–7.76 (m, 2H, ArH), 7.79 (m, 1H, C10H), 8.26
(d, 1H, J = 8.7 Hz, C9H), 8.88 (m, 1H, C11H). Anal.
Calcd. for C23H20BrN5OS (494.40): C, 55.87; H, 4.07; N,
14.16. Found: C, 55.90; H, 4.00; N, 14.00.
2950 (aliph H) and 1600 (C=N); H-NMR: d 1.18 (s, 3H,
CH3), 7.60 (m, 1H, C10H), 7.89 (m, 1H, C9H), 8.64 (m, 1H,
C11H), 12.19 (s, 1H, OH, D2O exchangeable). Anal. Calcd.
for C12H7BrN4OS(335.17): C, 43.00; H, 2.10; N, 16.71
Found: C, 43.20; H, 2.20; N, 16.50.
8-Bromo-6-hydrazinobenzothieno[3,2-d]
[1,2,4]triazolo[4,3-b] pyridazine (11)
8-Bromo-3-(2-methoxyphenyl)-6-hydroxybenzothieno
[3,2-d][1,2,4]triazolo[4,3-b] pyridazine (16)
Yield: 82.0%; mp: 300°C; IR (cm-1): 3400 (NH/NH2) and
1610 (C=N); H-NMR: d 5.46 (br s, 3H, NH-NH2, D2O
Yield: 70.0%; mp \300°C; IR (cm-1): 3373–3404 (OH),
2927 (aliph H) and 1608 (C=N); H-NMR: d 3.84 (s, 3H,
1
1
exchangeable), 7.55 (m, 1H, C10H), 7.84 (m, 1H, C9H),
8.65–8.72 (m, 2H, C11H and C3H). Anal. Calcd. for
C11H7BrN6S (335.17): C, 39.41; H, 2.10; N, 25.07. Found:
C, 39.47; H, 2.30; N, 25.10.
OCH3), 4.68 (s, 1H, OH, D2O exchangeable), 7.06–7.62
(m, 4H, ArH), 7.76 (m, 1H, C10H), 8.38 (m, 1H, C9H), 8.86
(m, 1H, C11H). Anal. Calcd. for C18H11BrN4OS (411.27):
C, 52.56; H, 2.69; N,13.70. Found: C, 52.49; H, 2.73; N,
13.70.
8-Bromo-6-hydrazino-3-methylbenzothieno[3,2-d]
[1,2,4]triazolo[4,3-b] pyridazine (12)
Antiinflammatory activity screening
Yield: 69.0%; mp: 300°C; IR (cm-1): 3400 (NH/NH2),
2900 (aliph H), 1640 (C=N); 1H-NMR: d 1.75 (s, 3H,
CH3), 5.33 (br s, 3H, NH-NH2, D2O exchangeable), 7.56
(m, 1H, C10H), 7.84 (m, 1H, C9H), 8.69 (m, 1H, C11H).
Anal. Calcd. for C12H9BrN6S (349.20): C, 41.27; H, 2.59;
N, 24.06. Found: C, 41.10; H, 2.60; N, 23.90.
The preliminary screening was performed applying the
procedure of Winter et al. (1962) using groups of albino rats
weighing 100–120 g each, 6 rats per group. The first group
was injected with 0.05 ml of 1% carrageenan in the subpl-
antar tissue of the right hind paw and served as untreated
control. The positive control group was given 10 mg/kg
indomethacin 1 h before carrageenan injection. The test
compounds were suspended in 0.5% carboxymethylcellu-
lose (CMC) and given to the rats orally at a dose of 10 mg/kg
1 h prior to carrageenan injection. In all groups, both hind
limbs were dissected 4 h after carrageenan injection and
weighed, and the difference in weight was calculated. The
effect of the test compounds were compared with control and
standard by ordinary one-way ANOVA (Table 1).
8-Bromo-3-(2-methoxyphenyl)-6-hydrazino
benzothieno[3,2-d][1,2,4]triazolo[4,3-b] pyridazine (13)
Yield: 77.0%; mp: 240–242°C; IR (cm-1): 3450 (NH/NH2)
and 1590 (C=N); 1H-NMR: d 3.67 (br s, 3H, NH-NH2, D2O
exchangeable), 3.88 (s, 3H, OCH3), 7.14–7.26 (m, 2H,
ArH), 7.63–7.67 (m, 2H, ArH),7.96 (m, 1H, C10H), 8.48
123

Med Chem Res (2012) 21:3146–3153
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Table 1 Antiinflammatory activity of the tested compounds using
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Comp. no.
Increase in paw weight
(mean SEM)
% Inhibition
of edema
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7
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8
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10
1.01 0.008
0.52 0.83*
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