Pyridazine derivatives and related compounds, Part 12: Synthesis of some pyridazino [4′,3′:4,5]thieno[3,2-d]-1,2,3-triazines

Article abstract of DOI:10.1080/104265090517398

The syntheses of pyridazino[4′,3′:4, 5]thieno[3, 2-d]-1,2,3-triazinones 2, 3, 6, derivatives of the ring system thieno[2,3-c]pyridazine, have been accomplished by a diazotization reaction. Reaction of triazine 3 with phosphorous oxychloride led to 4-chlor

Full text of DOI:10.1080/104265090517398

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Pyridazine Derivatives and
Related Compounds, Part 12:
Synthesis of Some Pyridazino
′
[4 ,3 ′ :4,5]thieno[3,2-
d]1,2,3-triazines
Ali Deeb a , Mahmoud Kotb a & Mohamed El-Abbasy a
a Department of Chemistry, Faculty of Science,
Zagazig University, Zagazig, AR Egypt
Published online: 21 Dec 2010.
To cite this article: Ali Deeb , Mahmoud Kotb & Mohamed El-Abbasy (2005) Pyridazine
′
Derivatives and Related Compounds, Part 12: Synthesis of Some Pyridazino [4 ,3
′ :4,5]thieno[3,2-d]1,2,3-triazines, Phosphorus, Sulfur, and Silicon and the Related
Elements, 180:2, 591-599, DOI: 10.1080/104265090517398
To link to this article: http://dx.doi.org/10.1080/104265090517398
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Phosphorus, Sulfur, and Silicon, 180:591–599, 2005
Copyright © Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/104265090517398
Pyridazine Derivatives and Related Compounds, Part 12:
Synthesis of Some Pyridazino [4ꢀ,3ꢀ:4,5]thieno[3,2-d]-
1,2,3-triazines
Ali Deeb
Mahmoud Kotb
Mohamed El-Abbasy
Department of Chemistry, Faculty of Science, Zagazig University,
Zagazig, AR Egypt
The syntheses of pyridazino[4ꢀ,3ꢀ:4, 5]thieno[3, 2-d]-1,2,3-triazinones 2, 3, 6, deriva-
tives of the ring system thieno[2,3-c]pyridazine, have been accomplished by a diazo-
tization reaction. Reaction of triazine 3 with phosphorous oxychloride led to 4-chloro
derivative 7 which, on further displacement reactions, gives 4-substituted deriva-
tives. All new compounds were characterized by elemental analyses and spectral
data.
Keywords Pyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]-1,2,3-triazines; synthesis; thieno[2,3-c]-
pyridazine
INTRODUCTION
Heterocyclic annulated pyridazines continue to attract considerable
attention, which mainly arises from the large variety of interest-
ing pharmacological activities observed with pyridazine derivatives.1
On the other hand 1,2,3-triazine systems condensed with carbocy-
cles or heterocycles are known2 and exhibit antiallergic activity.3 In
connection with these facts and in continuation of our efforts di-
rected toward the synthesis of tricyclic systems containing a pyridazine
subunit,4 we report on the utility of 5-amino-3,4-diphenylthieno[2,3-
c]pyridazine-6-carbohydrazide (1) as a synthon for the preparation of
pyridazino[4ꢀ,3ꢀ:4,5]thieno[3, 2-d]-1,2,3-triazines with potential biolog-
ical activity.
Our synthesis began with the preparation of 5-amino-3,4-
diphenylthieno-[2,3-c]pyridazine-6-carbohydrazide (1), which was ob-
tained in good yield from the reaction of ethyl 5-amino-3,4-diphenyl-
thieno[3,4-c]pyridazine-6-carboxylate5 with hydrazine hydrate. This
Received June 1, 2004.
Address correspondence to Ali Deeb, Department of Chemistry, Faculty of Science,
Zagazig University, Zagazig, AR Egypt. E-mail: dralideeb@hotmail.com
591

592
A. Deeb et al.
hydrazide, and compounds derived from it, underwent the
transformation illustrated in Scheme 1. Diazonium ion condensa-
tion with an adjacent function to form a five- or six-membered rings
has proved useful for synthesizing various nitrogen heterocycles
including a number of 1,2,3-triazines6 that are formed via intramolec-
ular attack of an electrophilic nitrogen function. Thus, the reaction
of 1 with one equivalent of sodium nitrite in acetic acid at 5◦C
resulted in the formation of a compound which was assigned the struc-
ture 3-amino-8,9-diphenylpyridazino[4ꢀ,3ꢀ:4,5]-thieno[3,2-d]-1,2,3-tri-
azin-4(3H)-one (2), rather than either an amino-carbonylazide or a
tetrazepin, on the basis of spectral data. Their spectrum did not show
any characteristic band for the azido group at about 2000–2200 cm−1
.
In the 1H-NMR was observed a peak at 6.7 which was assigned
to the exocyclic amino group at position three and would not have
been observed if a seven membered ring had been formed in the
diazotization reaction. When 5-amino-6-carbohydrazide derivative 1
was treated with an excess of sodium nitrite, there was observed a
smooth conversion of 1 to 8,9-diphenylpyridazino-[4ꢀ,3ꢀ:4,5]thieno[3,2-
d]-1,2,3-triazin-4(3H)-one (3). This reaction presumably proceeds via
2 with the excess sodium nitrite, then removing the exocyclic amino
group. However, a new and facile preparation of 3 by diazotization
of 5-amino-3,4-diphenylthieno[2,3-c]pyridazine-6-carboxamide (4)7
with sodium nitrite in acetic acid at 5◦C was accomplished in the
present investigation for comparison with the product obtained from
1. The 3-aminotriazinone 2 was also obtained following another
procedure, by converting the carbohydrazide 1 into the corresponding
6-benzylidenecarbohydrazide derivative 5 followed by treatment with
nitrous acid. The 3-benzylideneaminopyridazinothienotriazinone 6
was readily hydrolysed in presence of ethanolic hydrazine hydrate
boiling solution to 2.
The final part of this study was an examination of the reac-
tion of parent pyridazinothienotriazinone 3 with phosphoryl chlo-
ride which yielded 4-chloro-8,9-diphenylpyridazino[4ꢀ,3:4,5]thieno[3,2-
d]-1,2,3-triazine 7 (42%). The chlorine atom of 7 showed the expected
reactivity towards nucleophilic reagents. Treatment of 4-chloro deriva-
tive 7 with thiourea provided the 4-mercapto system 8. Their spectrum
of 8 indicated bands at 2550 cm−1 and 1470 cm−1, suggesting that it
existed as a tautomeric mixture of 8 and the corresponding thioamide.
The chlorine atom was also displaced by a thioglycolate and gave the
corresponding thioacetate 9, while with sodium azide 7 gave the tetra-
zole 10. Their spectrum of 10 showed no bands near 2100 cm−1 which
excludes the azidotriazine structure in the solid state. When compound
7 was treated with hydrazine hydrate, 4-hydrazino 11 was obtained.

Synthesis of Pyridazino Thieno-Triazines
593
SCHEME 1

594
A. Deeb et al.
Compound 11 in turn could be transformed to other heterocyclic sys-
tems. When reacted with phthalic anhydride, the N-phthalimide 12
was obtained. The reaction of 11 with phenyl isothiocyanate afforded
N-phenylthio(carbamoyl)hydrazine 13, while the condensation with p-
nitrobenzaldehyde afforded the corresponding hydrazone 14. The tetra-
zole 10 was also obtained from 11 via the diazonium process involving
sodium nitrite in acetic acid. Finally the interaction of 11 with acety-
lacetone afforded a compound whose ir spectrum lacked both C O and
NH bands, indicating that both the two carbonyl groups of acetylace-
tone were condensed with the hydrazine group of 11 giving compound
15. The most salient features of ir and 1H-NMR spectra are given under
experimental.
In view of the wide range of pharmacological properties reported for
various thienopyridazines and several other related compounds, the
various pyridazino-thienotriazines prepared now should be screened
for their biological activity. The results will be published elsewhere.
EXPERIMENTAL
Melting points were determined in open-glass capillaries and were un-
corrected. Their spectra of the compounds were recorded on a Perkin-
Elmer spectrophotometer, model 1310, as potassium bromide pellets,
1
and frequencies are reported in cm−1. The H-NMR spectra were ob-
served on a Perkin-Elmer R12 B spectrometer, and chemical shifts (δ)
are in ppm relative to internal TMS. Microanalyses for C, H, and N were
performed on a Perkin-Elmer 240 elemental analyzer. Reactions were
routinely followed by thin layer chromatography (tlc) on silica gel F254
aluminium sheets (Merck). The spots were detected by uv irradiation
at 254–365 nm.
5-Amino-3,4-diphenylthieno[2,3-c] pyridazine-
6-carbohydrazide (1)
A solution of ethyl 5-amino-3,4-diphenylthieno[2,3-c]pyridazine-6-carb-
oxylate (0.75 g, 2 mmol) and hydrazine hydrate (0.7 mL, 85%) in ethanol
(20 mL) was boiled under reflux for 2 hours. The crystals that separated
on cooling were filtered off and dried to give the hydrazide derivative
1 (0.89 g, 92%), m.p. 245–246◦C (ethanol); ir: 3450, 3320, 3260 (NH
groups), 1640 (C O), 1600 (C N), 1530 (C C) cm−1; 1H-NMR (DMSO-
d6): 9.4 (s, 1H, NH), 7.80 (s, 2H, NH2), 7.4–7.0 (s, 10H, 2Ph), 4.2 (s, 2H,
5-NH2).

Synthesis of Pyridazino Thieno-Triazines
595
Anal. Calcd for C19H15N5OS: C, 63.14; H, 4.18; N, 19.38. Found: C,
63.00; H, 4.10; N, 19.20.
3-Amino-8,9-diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]-1,2,3-
triazin-4(3H)-one (2)
Carbohydrazide 1 (11.7 g, 32.3 mmol) was dissolved in water (45 mL)
containing 10 ml of acetic acid with rapid stirring. This solution was
cooled to 5◦C, and then sodium nitrite (2.3 g, 33.3 mmol) dissolved in
water (10 mL) was added dropwise over a period of 15 minutes to the
rapidly stirred solution while maintaining the temperature at 5–10◦C.
After the addition was complete, the solution was stirred an additional
15 minutes, and the temperature was then allowed to rise to 15◦C. The
solution was maintained at this temperature for 30 minutes at which
time a solid began to separate. The reaction mixture was allowed to
stand at 5◦C for 16 hours. The solid was removed by filtration, washed
with ether, and dried at room temperature to yield 7.6 g 63.4% of 2, m.p.
196–197◦C (ethanol); ir: 3500, 3310, 3180 (NH groups), 1670 (C O),
1
1640 (C N), 1530 (C C) cm−1; H-NMR (DMSO-d6): 7.6–7.4 (m, 10H,
2Ph), 6.7 (s, 2H, NH2).
Anal. Calcd. for C19H12N6OS: C, 61.27; H, 3.25; N, 22.57. Found: C,
61.00; H, 3.00; N, 22.10.
8,9-Diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]-1,2,3-triazin-4
(3H)-one (3)
Method A
Carbohydrazide 1 (3.5 g, 9.69 mmol) was dissolved in water (25 mL)
and acetic acid (5 mL). Sodium nitrite (3.4 g, 50 mmol) was dissolved
in water (10 mL) and added in the same manner as for compound 2.
The solid that formed was collected by filtration and dried at room tem-
perature to yield 2.97 g, (86%) of 3, m.p. 260–261◦C (ethanol); ir: 3210
(NH), 1650 (C O), 1640 (C N), 1520 (C C) cm−1; 1H-NMR (DMSO-d6):
7.6–7.4 (m, 10H, 2Ph), 3.35 (br, s, 1H, NH).
Anal. Calcd. for C19H11N5OS: C, 63.85; H, 3.10; N, 19.59. Found: C,
63.60; H, 3.00; N, 19.30.
Method B
3,4-Diphenyl-5-aminothieno[2, 3-c]pyridazine-6-carboxamide
(4)
(2.48 g, 7.15 mmol) was dissolved in a mixture of water (15 mL) and
acetic acid (3 mL). Sodium nitrite (1.5 g, 21.7 mmol) was dissolved in
water (3 mL) and then added in the same manner as that described for
the preparation and isolation of compound 2. The solid that formed was

596
A. Deeb et al.
collected by filtration and dried at room temperature to yield 2.13 g,
(83.5%) of 3 which was identical in all respects with the compound
from Method A.
5-Amino-3,4-diphenylthieno[2,3-c]pyridazine-6-
benzylidene carbohydrazide (5)
A solution of the benzaldehyde (0.5 g, 4.7 mmol) and compound 1 (1.5 g,
4.15 mmol) in ethanol (30 mL) containing a few drops of glacial acetic
acid was boiled under reflux for 2 hours. The precipitated product was
collected by filtration upon cooling and was recrystallized for analysis,
m.p. 155–156◦C (ethanol), 1.6, (87%); ir: 3500, 3370, 3176 (NH groups),
1671 (C C), 1605 (C N), 1542 (C C) cm−1; 1H-NMR (DMSO-d6): 8.40
(s, 1H, NH), 7.90 (s, 1H, CH), 7.8 (s, 2H, NH2), 7.60–7.40 (m, 15H, 3Ph).
Anal. Calcd. for C26H19N5OS: C, 69.46; H, 4.26; N, 15.58. Found: C,
69.20; H, 4.00; N, 15.30.
3-Benzylideneamino-8,9-diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno
[3,2-d]-1,2,3-triazin-4(3H)-one (6)
A suspension of finely ground compound 5 (1 g) in 2M hydrochloric
acid (20 mL) was diazotized in the usual way with sodium nitrite (0.3
g) in water (4 mL), the temperature being kept below 5◦C throughout.
The bright yellow suspension was stirred at room temperature for 1.5
hours after the addition had been completed. The solid was then col-
lected by filtration, washed with cold water, and dried to give the title
6 (0.9 g, 94%), m.p. 280–281◦C (ethanol); ir: 1705 (C O), 1620 (C N),
1540 (C C) cm−1,1H-NMR (DMSO-d6): 8.10 (s, 1H, CH), 7.70–7.40 (m,
15 H, 3Ph).
Anal. Calcd. for C26H16N6OS: C, 67.80; H, 3.50; N, 18.25. Found: C,
67.60; H, 3.30; N, 18.00.
Hydrolysis of 6
Compound 6 (0.7 g, 1.52 mmol) was suspended in ethanol (25 mL), 95%
hydrazine hydrate (3 mL) was added, and the reaction mixture was
refluxed for 5 hours. When it cooled to room teperature, a solid precip-
itated, which was washed with water and dried to give 2, 0.38 g, 68%,
m.p. 196–197◦C, that was not depressed when mixed with an authentic
sample of 2.
4-Chloro-8,9-diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]-1,2,3-
triazine (7)
A mixture of compound 3 (5 g, 13.95 mmol) and phosphorous oxychloride
(15 mL) was heated at reflux temperature for 3 hours. The reaction

Synthesis of Pyridazino Thieno-Triazines
597
mixture was cooled in an ice bath and then hydrolyzed by addition of
crushed ice. The precipitate was filtered and wash with water and dried,
(2.18 g,, 42%), m.p. 116–117◦C; ir: 1660 (C N), 1540 (C C) cm−1
.
Anal. Calcd. for C19H10ClN5S: C, 60.72; H, 2.68; N, 18.64. Found: C,
60.60; H, 2.60; N, 18.60.
4-Mercapto-8,9-diphenylpyridazino[4ꢀ,3:4,5]thieno[3,2-d]-
1,2,3-triazine (8)
A solution of 7 (3.38 g, 9.0 mmol) and thiourea (1 g, 13.0 mmol) in
ethanol (60 mL) was refluxed for 1 hour. The solvent was evaporated
in vacuo, and the residue was refluxed in sodium hydroxide solution
(50 mL, 2.5 N) for 30 minutes and then filtered on hot. The filtrate was
cooled and acidified with hydrochloric acid (pH 2). The yellow crystals
obtained were filtered, washed with water, and dried to give 8 (3 g, 90%),
m.p. 245–246◦C (ethanol); ir: 2550 (SH), 1635 (C N), 1570 (C C) cm−1
;
1H-NMR (DMSO-d6): 13.5 (s, 1H, NH), 7.9–7.6 (m, 10H, 2Ph).
Anal. Calcd. for C19H11N5S2: C, 61.10; H, 2.97; N, 18.75. Found: C,
61.00; H, 2.90; N, 18.60.
Ethyl 9,10-Diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]-1,2,3-
triazin-4-ylthio-acetate (9)
To a solution of 7 (0.76 g, 2 mmol) in acetone (30 mL) containing an-
hydrous potassium carbonate (0.5 g) and ethyl mercaptoacetate (0.72
g, 6 mmol) was added. The reaction mixture was refluxed for 4 hours
and the insoluble solid was removed by filtration and washed with ace-
tone. The filtrate and the washings were combined and evaporated. The
residue was recrystallized to give 9 (0.74 g, 79%), m.p. 166–167◦C (pet.
1
ether 40/60); ir: 1738 (C O), 1650 (C N) and 1530 (C C) cm−1; H-
NMR (CDCl3): 7.6–7.2 (m, 10H, 2Ph), 5.6 (br, s, 2H, SCH2), 4.6-4.2 (q,
2H J = 6.5 Hz, CH2CH3), 1.4 (t, 3HJ = 6.5 Hz, CH2CH3).
Anal. Calcd. for C23H17N5S2O2: C, 60.11; H, 3.73; N, 15.24. Found:
C, 60.00; H, 3.60; N, 15.10.
7,8-Diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]tetrazolo[1,5-f]-
1,2,3-triazine (10)
Method A
A solution of 7 (0.78 g, 2 mmol) and sodium azide (0.26 g, 4 mmol) in
ethanol (25 mL) was refluxed for 2 hours. The solvent was evaporated
in vacuo and the residue was washed with water, filtered, and dried to

598
A. Deeb et al.
give 10 (076 g, 96%), m.p. 187–188◦C (ethanol); ir: 1650 (C N), 1540
(C C) cm−1
.
Anal. Calcd. for C19H10N8S: C, 59.67; H, 2.64; N, 29.30. Found: C,
59.60; H, 2.50; N, 29.20.
Method B
To a suspension of 11 (0.74 g, 2 mmol) in acetic acid (1N, 25 mL) at
45◦ was added sodium nitrite 0.3 g (4.0 mmol). Effervescence occurred
immediately. After 1.5 hours, the solution was cooled, and the product
was filtered to give 10 (0.3 g, 40%) which, upon recrystallization, was
identical to that described in method A.
4-Hydrazino-8,9-diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]-
1,2,3-triazine (11)
A solution consisting of 7 (0.76 g, 2 mmol) and hydrazine hydrate (1 mL,
85%) in ethanol (30 mL) was refluxed for 2 hours, and upon cooling, the
product precipitated was filtered and recrystallized to give 11 (0.73 g,
97%; m.p. 232-233◦C (ethanol); ir: 3427, 3325 (NH2), 1610 (C N), 1535
1
(C C) cm−1; H-NMR (DMSO-d6): 8.81 (br s, 1H, NH), 7.90-7.40 (m,
10H, 2Ph), 4.40 (s, 2H, NH2).
Anal. Calcd. for C19H13N7S: C, 61.44; H, 3.53; N, 26.40. Found: C,
61.30; H, 3.40; N, 26.30.
N-(4-Amino-8,9-diphenylpyridazino[4ꢀ,3ꢀ:4,5]thieno[3,2-d]-
1,2,3-triazine)-phthalimide (12)
A mixture of 11 (0.38 g, 1 mmol) and phthalic anhydride (0.15 g, 1 mmol)
in absolute ethanol (30 mL) was refluxed for 3 hours. The pale yellow
crystals separated upon cooling and were filtered and dried to give 12
(0.4 g, 77%), m.p. 299-300◦C (ethanol); ir: 3310 (NH), 1720 (C O), 1640
1
(C N), 1520 (C C) cm−1; H-NMR (DMSO-d6): 7.6-7.2 (m, 14H, aro-
matic phenyl protons), 3.0 (br, s, 1H, NH).
Anal. Calcd. for C27H15N7O2S: C, 64.66; H, 3.01; N, 19.55. Found: C,
64.60; H, 2.90; N, 19.40.
N-(8,9-Diphenylpyridazino[4ꢀ,3:4,5]thieno[3,2-d]-1,2,3-
triazin-4-yl)-Nꢀ-[phenylthio(carbamoyl)]hydrazine (13)
A solution of 11 (0.38 g, 1 mmol) and phenyl isothiocyanate (0.14 g,
1 mmol) in absolute ethanol (30 mL) was refluxed for 1.5 hours. Upon
cooling the product precipitated was filtered and dried to give 13 (0.34 g,
65%), m.p. 270–271◦C (ethanol); ir: 3460, 3300, 3100 (NH groups), 1620

Synthesis of Pyridazino Thieno-Triazines
599
1
(C N), 1550 (C C) cm−1; H-NMR (DMSO-d6): 13.10 (br s, 1H, NH),
11.35 (br s, 1H, NH), 9.5 (br s, 1H, NH), 7.8-7.5 (m, 15H, 3Ph).
Anal. Calcd. for C26H18N8S2: C, 61.64; H, 3.58; N, 22.12. Found: C,
61.50; H, 3.50; N, 22.00.
4-(p-Nitrobenzaldehydehydrazone)-8,9-diphenylpyridazino
[4ꢀ,3:4,5]thieno-[3,2-d]-1,2,3-triazine (14)
A mixture of 11 (0.38 g, 1 mmol) and p-nitrobenzaldehyde (0.16 g,
1 mmol) in ethanol (30 mL) was refluxed for 2 hours. Pale yellow crys-
tals deposited during the refluxing time. The separated product was
filtered and dried to give 14 (0.31 g, 61%); m.p. 275–276◦C; ir: 3500,
3300 (NH), 1640 (C N), 1550 (C O) 1510, 1475 (NO2) cm−1; 1H-NMR
(DMSO-d6): 8.95 (s, 1H, CH N ), 8.2–8.0 (m, 5H, aromatic protons
and NH), 7.8–7.2 (d, 10H, 2Ph).
Anal. Calcd. for C26H16N8O2S: C, 61.89; H, 3.20; N, 22.21. Found: C,
61.80; H, 3.00; N, 22.10.
8,9-Diphenyl-4-(3,5-dimethyl-1-pyrazolyl)pyridazino[4ꢀ,3ꢀ:4,5]
thieno[3,2-d]-1,2,3-triazine (15)
To a solution of 11 (0.38 g, 1 mmol) in absolute ethanol (30 mL) was
added acetylacetone (0.1 g, 1 mmol). The reaction mixture was refluxed
for 6 hours. Upon cooling, the precipitated product was filtered and dried
to give 15 (0.38 g, 85%); m.p. 245–246◦C (ethanol); ir: 1620 (C N), 1530
1
(C C) cm−1; H-NMR (DMSO-d6): 7.65 (s, 1H, 4ꢀ-H), 7.6-7.2 (m, 10H,
2Ph), 2.95 (s, 3H, CH3), 2.45 (s, 3H, CH3).
Anal. Calcd. for C24H17N7S: C, 66.19; H, 3.93; N, 22.51. Found: C,
66.00; H, 3.80; N, 22.40.
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