Pyridazine derivatives and related compounds. Part 13: Synthesis and antimicrobial activity of some pyridazino[3′,4′:3,4]pyrazolo[5,1-c]- 1,2,4-triazines

Article abstract of DOI:10.1016/j.bmcl.2004.06.102

Pyridazinopyrazolotriazine A general method for the preparation of substituted pyridazinopyrazolotriazines is reported. 3-Aminopyrazolo[3,4-d] pyridazine was diazotized and coupled with active methylene reagents to afford the tricyclic pyridazino[3′,4′:3,

Full text of DOI:10.1016/j.bmcl.2004.06.102

Bioorganic & Medicinal Chemistry Letters 14 (2004) 5013–5017
Pyridazine derivatives and related compounds. Part 13:
Synthesis and antimicrobial activity of some
pyridazino[30,40:3,4]pyrazolo[5,1-c]-1,2,4-triazinesq
b
b
Ali Deeb,a, Fatma El-Mariah and Mona Hosny
*
aDepartment of Chemistry, Faculty of Science, Zagazig University, Zagazig, Egypt
bDepartment of Chemistry, Faculty of Girls, Ain-Shams University, Cairo, Egypt
Received 17 March 2004; accepted 22 June 2004
Available online 18 August 2004
Abstract—A general method for the preparation of substituted pyridazinopyrazolotriazines is reported. 3-Aminopyrazolo[3,4-d]pyri-
dazine was diazotized and coupled with active methylene reagents to afford the tricyclic pyridazino[30,40:3,4]pyrazolo[5,1-c]-1,2,4-
triazines with substituents such as methyl, phenyl, ethoxycarbonyl, acetyl or benzoyl, depending on the methylene reagent used.
In addition several condensation reactions with hydrazines gave the corresponding acid hydrazide and/or hydrazones. Reactions
of 3 with aromatic aldehydes afforded hydrazones. The products were screened for their antimicrobial activity against five micro-
organisms.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
azolo[5,1-c]-1,2,4-triazines; the reaction of compound 1
with different b-bifunctional reagents seemed to be a
logical method for preparation of these compounds.
Thus when compound 1 treated with ethyl acetoacetate
a product 2 was obtained. Structure 2 was estab-
lished for this product based on its analytical and spec-
tral data. The mass spectrum showed the expected
molecular ion peak M+ at m/e 410 (100%), and a charac-
teristic fragmentation pattern, where the most abun-
dant peaks at m/e 381 (MꢀC2H5) and at m/e 337
(MꢀCOOC2H5).
Heterocyclic diazo compounds represent an interesting
class of reactive substrates2 and their stability depends
mainly on charge delocalization through the hetero-
cyclic ring. Recently we have described the reaction
between the stable 3-diazo-4,5-diphenylpyrazolo[3,4-
c]pyridazine 1 and reactive methylene compounds.3 We
now report similar reactions with further examples of
active methylene reagents and the confirmation of their
product structures. Moreover, several pyridazine ring
systems are associated with diverse biological activities4
as well as the biological activities of pyrazolopyridazine
and pyrazolotriazine ring systems are well docu-
mented.5,6 Therefore, it was thought of interest to com-
bine the above mentioned biolabile rings together in a
molecular framework to see the additive effect of these
rings toward the biocidal activities.
Addition of hydrazine hydrate to compound 2 gave
3-carboxylic acid hydrazide 3 in high yield. The assign-
ment of structure 3 was based on an analytical and spec-
tral data. The IR spectrum displaying bands at
3450–3275 (NH), 1660 (C@O) and 1592cmꢀ1 (C@N).
The carbohydrazide 3 was reacted with aromatic alde-
hydes in ethanol to give the corresponding carbohydr-
azones 4a–l. The structure of compound 4a–l was
elucidated on the basis of their analytical and IR data.
The IR absorption spectra showed the disappearance
of the broad band at 3450cmꢀ1 (NH2) and the existence
of small band at 3220cmꢀ1 (NH). Also the reaction of 2
with phenylhydrazine and semicarbazide was carried out
in refluxing ethanol to yield the corresponding carbo-
hydrazide derivatives 5, 6.
2. Chemistry
The required 3-diazo-4,5-diphenylpyrazolo[3,4-d]-pyrid-
azine 1 was prepared following the literature method.7
As a route for the synthesis of pyridazino-[30,40:3,4]pyr-
q See Ref. 1.
*
Corresponding author. E-mail: dralideeb@hotmail.com
0960-894X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.06.102

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A. Deeb et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5013–5017
The hydrolysis of 2 was possible by heating under reflux
with ethanolic potassium hydroxide. The identification
of the resulting product as 3-carboxylic acid derivative
7 was based on spectral data and its subsequent reaction
product. The IR spectrum exhibited absorption band at
3424 (OH), and at 1703cmꢀ1 (C@O). Compound 7
underwent ready decarboxylation to give 8 on heating
above its melting point. By analogy with ethyl acetoac-
etate, acetylacetone, benzoylacetone and ethyl benzoyl-
acetate react readily with compound 1 to give the
corresponding substituted pyridazino[30,40:3,4]-pyrazolo-
[5,1-c]-1,2,4-triazine derivatives 9, 13 and 17, respec-
tively. The structure of compound 9 was elucidated on
the basis of their analytical and spectral data. The mass
spectrum showed the expected molecular ion peak M+ at
m/e 380 (73.6%), and a characteristic fragmentation pat-
tern where the most abundant peaks at m/e 337
singlet at 3.2 due to 3H (CH3) and chemical evidence.
The reaction of 9 with hydrazine hydrate, phenyl hydra-
zine and semicarbazide yielded the expected hydrazones
10–12. The structures of products 10–12 follow their
method of preparation and their physical data (see
Experimental section). The oxidation of acetyl group
in compound 9 using hypobromite yielded the corre-
sponding carboxylic acid derivative which underwent
ready decarboxylation on heating above its melting
point. Structure of these compounds were assigned by
comparison with authentic samples 8 and 9, respectively.
The structure of compound 13 instead of the anticipated
product 13a was elucidated on the basis of their analyt-
ical and spectral data. The mass spectrum showed the
expected molecular ion peak M+ at m/e 442, and a char-
acteristic fragmentation pattern where the most abun-
dant peaks at m/e 337 (MꢀCOPh) shows the presence
of benzoyl group and not acetyl group. The hydrazino-
lysis of 13 with hydrazine hydrate, phenyl hydrazine and
semicarbazide give the hydrazones 14–16, the structures
were established based on their analytical and spectral
data.
1
(MꢀCOCH3) (100%). The H NMR spectrum revealed
presence of multiplet at d 7.9–7.2 due to 10H (phenyl
protons), singlet at d 3.8 due to 3H (–COCH3) and
Ph
N
Ph
N2
Ph
N
Ph
Structural elucidation of compound 17 was accom-
plished from analytical, spectral data, and chemical evi-
dence. The mass spectrum showed the expected
molecular ion peak M+ at m/e 472 (100%). The reaction
of the ester 17 with hydrazine hydrate, phenylhydrazine
and semicarbazide yielded the expected hydrazides 18–
20. The ester 17 was saponified with potassium hydrox-
ide to give the expected acid 21, which underwent ready
decarboxylation on heating above its melting point and
yielded 22. The most salient features of IR and 1H NMR
are given under Experimental.
N
N
N
N
N
N
R
N
N
Me
R = COOEt
1
2,
R = CONHNH
3,
2
R = CONHN=CHAr
4a-l,
Ar = Ph
Ar =
Ar =
Ar =
OMe
4a,
4c,
4b,
4d,
Cl
NO2
Ar =
Ar =
Ar =
Ar =
4e,
4g,
4f,
3. Antimicrobial activity
4h,
N
H
N
The in vitro antimicrobial activities for some of the syn-
thesized compounds at different applied concentrations,
(1000, 5000, and 10,000ppm) against Escherichia coli,
Pseudomonas aeruginosa, and Staphylococcus aureus
and also antifungal activity against Candida albicans
were determined.
Me
Ar =
Ar =
Ar =
Ar =
4i,
4j,
4l,
O
S
O
S
Me
Me
4k,
R = -CONHNHPh
R = -COOH
R = -COMe
R = -CONHNHCONH
R = -H
5,
7,
9,
6,
8,
10,
2
The bacteria under investigation were cultivated on
nutrient agar medium, whereas yeast were cultivated
on malt extract agar.
C
NNH2
R =
R =
R =
R =
Me
C
C
NNHPh
NNHPh
NNHCONH2
NNH2
R =
11,
12,
14,
16,
Me
Me
C
The antimicrobial activity of the studied compounds
were assayed by measuring the inhibition zone of micro-
bial growth caused by known volume of water soluble
compounds, the method was essentially as follows.
R = -COPh
13,
15,
Ph
C
C
NNHCONH2
R =
Ph
Ph
Ph
N
Ph
N
Hold glass microfiber discs (0.6cm) with saturated
known volume (0.2mL) of different concentrations of
aqueous solution of the compounds synthesized were
put on the surface of the specific agar medium seeded
with the test organisms. Then the plates were incubated
at 37°C for 48h for bacteria and at 28°C for 96h for
yeast, and the diameter of inhibition zone in millimeters
were measured.
N
N
N
N
R
Ph
13a, R = COMe
18, R = CONHNH2
20, R = CONHNHCONH2 21, R = COOH
22, R = H
17, R = COOEt
19, R = CONHNHPh

A. Deeb et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5013–5017
5015
4.1.1. Ethyl 4-methyl-9,10-diphenylpyridazino[30,40:3,4]-
pyrazolo[5,1-c]-1,2,4-triazine-3-carboxylate 2. Prepared
from ethyl acetoacetate, yellow crystals in 92.6% yield,
mp 248–250°C (ethanol); MS: m/e 410 (M+, 100%),
381 (4.4%), 337 (56.3%), 310 (40.5%), IR: 1728 (C@O),
Table 1.
Compoundb
Organisma
A
B
C
D
4b
4d
4g
4i
3
––
5
––
––
––
––
––
––
––
2
––
––
––
––
––
2
1
––
––
––
2
1620 (C@N) and 1540 (C@C); H NMR (DMSO-d6):
2
7.8–7.2 (m, 10H, 2Ph), 4.4 (q, 2H, CH2CH3), 3.6 (s,
3H, CH3) and 1.4 (t, 3H, CH2CH3). Anal. Calcd for
C23H18N6O2: C, 67.30; H, 4.42; N, 20.48. Found: C,
67.10; H, 4.20; N, 20.20.
2
4k
4l
2
––
4
––
––
3
9
16
3
––
4
4.1.2. 3-Acetyl-4-methyl-9,10-diphenylpyridazino[30,40:
3,4]pyrazolo[5,1-c]-1,2,4-triazine 9. Prepared from acetyl
acetone, yellow crystals in 90.2% yield, mp 268–270°C
(ethanol); MS: m/e 380 (M+, 73.7%), 337 (M+–COCH3,
100%), 310 (26.4%), 271 (35.3); IR: 1695 (C@O), 1625
a A, S. aureus; B, E. coli; C, P. aeruginosa; D, C. albicans; (––) = no
inhibition zones.
b No significant inhibition caused by compounds: 2, 4a, 4c, 4f, 4h, 4j,
5–8, 12, 14, 15, 17–22.
1
(C@N), 1540 (C@C); H NMR (CF3COOH): 7.9–7.2
(m, 10H, 2Ph), 3.8 (s, 3H, COCH3), and 3.2 (s, 3H,
CH3). Anal. Calcd for C22H16N6O: C, 69.46; H, 4.24;
N, 22.10. Found: C, 69.20; H, 4.00; N, 22.00.
The in vitro antimicrobial activity of the 27 compounds
screened is summarized in Table 1. The only significant
inhibition caused on the growth of all tested microor-
ganisms by the water soluble pure compounds at the
highest concentration (10,000ppm). Among the vari-
ously substituted derivatives of the pyridazino-pyrazolo-
triazines studied, eight had antimicrobial activity. The
acetyl derivative 9 had activity against the yeast C. alb-
icans and inhibited S. aureus. This activity was lost on
hydrazinolysis. The antibacterial activity of these hydr-
azides again increased by the condensation with aro-
matic aldehydes compounds 4b, 4d, 4g, 4i, 4k, and 4l
had activity against S. aureus and E. coli. Finally, com-
pound 16 had anti S. aureus, E. coli, and P. aeruginosa
activity. It is of interest to mention the antifungal activ-
ity of the products with regard to the agricultural impor-
tance of the fungi used.
4.1.3. 3-Benzoyl-4-methyl-9,10-diphenylpyridazino[30,40:
3,4]pyrazolo[5,1-c]-1,2,4-triazine 13. Prepared from ben-
zoylacetone, orange crystals in 81% yield, mp 277–
279°C (ethanol); MS: m/e 442 (M+, 10%), 337
(MꢀCOPh, 0.12%), 214 (17–5%), 105 (90%), 77
(100%); IR: 1700 (C@O), 1610 (C@N), 1540 (C@C).
Anal. Calcd for C27H18N6O: C, 73.29; H, 4.10; N,
19.00. Found: C, 73.0; H, 3.90; N, 19.10.
4.1.4. Ethyl 4-phenyl-9,10-diphenylpyridazino[30,40:3,4]-
pyrazolo[5,1-c]-1,2,4-triazine-3-carboxylate 17. Prepared
from ethyl benzoylacetate, orange crystals in 97% yield,
mp 225–227°C (ethanol); MS: m/e 472 (M+, 100%), 400
(65.5%), 373 (46%); IR: 1735 (C@O), 1625 (C@N), 1580
(C@C). Anal. Calcd for C28H20N6O2: C, 71.17; H, 4.27;
N, 17.79. Found: C, 70.90; H, 4.00; N, 17.80.
4. Experimental
4.1.5. 4-Methyl-9,10-diphenyl and 4,9,10-triphenylpyr-
idazino[30,40:3,4]pyrazolo[5,1-c]-1,2,4-triazine-3-carbohydr-
azide 3 and 18. A solution of ethyl carboxylate deriva-
tives 2 and/or 17 (1.0mmol) in ethanol (30mL) was
treated with hydrazine hydrate 85% (3mL). The reaction
mixture was refluxed for 3h, then it was concentrated
under reduced pressure and left to cool. The precipitate
was filtered and recrystallized from ethanol.
Melting points were determined in open glass capillaries
and are uncorrected. The IR spectra of the compounds
were recorded on a Perkin–Elmer spectrophotometer
model 1430 as potassium bromide pellets and frequen-
1
cies are reported in cmꢀ1. The H NMR spectra were
observed on a Perkin–Elmer R12B spectrometer and
chemical shifts (d) are in ppm relative to internal
TMS, and mass spectra were recorded on a Mass
Spectrometer HP model MS 5988 El 70ev. Reactions
were routinely followed by thin layer chromato-
graphy (TLC) on silica gel F254 aluminum sheets
(Merck). The spots were detected by UV irradiation at
254–365nm.
Compound 3. Yellow crystals, mp 252–253°C, yield
97%; IR: 3441, 3161, 1674, 1425. Anal. Calcd for
C21H16N8O: C, 63.63; H, 4.07; N, 28.27. Found: C,
63.40; H, 3.90; N, 28.0.
Compound 18. Red crystals, mp 240–241°C, yield 95%;
IR: 3420, 1667, 1585, 1118, 698. Anal. Calcd for
C26H18N8O: C, 68.11; H, 3.96; N, 24.44. Found: C,
67.90; H, 3.80; N, 24.10.
4.1. General procedure for the preparation of coupling
products from 3-diazo-4,5-diphenylpyrazolo[3,4-c]pyrid-
azine 1 and active methylene compounds
A solution of compound 1 (0.6g, 2mmol) in ethanol
(20mL) was treated with the corresponding active methyl-
ene compounds (2mmol). The reaction mixture was
refluxed for 30min. The separated product was filtered
off and crystallized. In this manner the following com-
pounds were prepared.
4.2. Reaction of 3 with aromatic aldehydes. Formation of
4a–l. General procedure
A mixture of the hydrazine derivative 3 (0.4g, 1.0mmol)
and aromatic aldehyde (1.0mmol) in ethanol (20mL)
was refluxed for 5h and then allowed to cool. The solid

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A. Deeb et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5013–5017
Table 2. 4-Methyl-9,10-diphenylpyridazino[30,40:3,4]pyrazolo[5,1-c]-1,2,4-triazin-3-yl)carbohydrazones (4a–l)
Compd No.
Ar
Ph
Mp (C°)
Yield (%)
Molecular formula
C28H20N8O
Analysis calcd/found (%)
C
H
N
69.41
69.20
4.16
3.90
23.13
22.80
4a
4b
4c
4d
286–288
240–241
292–294
308–310
95
91
90
90
67.69
67.40
4.31
4.00
21.78
21.50
C29H22N8O2
C28H19ClN8O
C28H19N9O3
OMe
Cl
64.80
64.50
3.69
3.40
21.59
21.30
63.51
63.30
3.62
3.40
23.81
23.60
NO2
71.89
71.70
4.15
4.00
20.96
20.80
4e
4f
C32H22N8O
C32H22N8O
C26H19N9O
302–304
286–288
253–254
85
91
86
71.89
71.60
4.15
3.90
20.96
20.70
65.95
65.80
4.04
3.90
26.63
26.40
4g
N
H
66.52
66.40
4.34
4.10
25.86
25.70
4h
C27H21N9O
244–246
80
N
Me
65.81
65.60
3.82
3.60
23.62
23.40
4i
4j
C
26H18N8O2
27H20N8O2
260–261
254–255
85
88
O
66.38
66.10
4.13
4.00
22.94
22.70
C
O
S
Me
63.66
63.40
3.70
3.50
22.84
22.70
4k
4l
C
26H18N8OS
27H20N8OS
284–285
289–290
90
91
64.27
64.00
3.99
3.70
22.21
22.00
C
S
Me
product was collected and recrystallized from ethanol.
The results are summarized in Table 2.
for C32H22N8O: C, 71.89; H, 4.15; N, 20.96. Found:
C, 71.60; H, 4.00; N, 20.80.
4.3. Reaction of ethyl carboxylate derivatives 2 and 17
with phenylhydrazine and with semicarbazide. General
procedure
Compound 20. Red crystals in 95% yield; mp 332–
333°C; IR: 3430, 3366, 3310, 1687, 1587; Anal. Calcd
for C27H19N9O2: C, 64.66; H, 3.82; N, 25.14. Found:
C, 64.40; H, 3.60; N, 25.00.
A mixture of ethyl carboxylate derivatives 2 and/or 17
(1.0mmol) and phenyl hydrazine and/or semicarbazide
hydrochloride (1.0mmol) in ethanol (20mL) was
refluxed for 3h, and then it was concentrated under
reduced pressure and left to cool. The precipitate was
filtered and recrystallized from ethanol.
4.4. Reaction of 3-acetyl(benzoyl) derivatives 9 and 13
with hydrazines. General procedure
A mixture of compound 9 and/or 13 (1.0mmol) and hy-
drazines namely hydrazine hydrate 85%, phenylhydr-
azine, and/or semicarbazide hydrochloride (1.0mmol)
in ethanol (20mL) was refluxed for 3h, and then it was
concentrated under reduced pressure and left to cool.
The precipitate was filtered and recrystallized from etha-
nol.
Compound 5. Orange crystals in 65% yield; mp 316–
317°C; IR: 3446, 3144, 1672, 1555, 1333, 1113, 659.
Anal. Calcd for C27H20N8O: C, 68.63; H, 4.27; N,
23.72. Found: C, 68.40; H, 4.00; N, 23.40.
Compound 6. Orange crystals in 70% yield; mp 314–
315°C; IR: 3414, 3342, 3194, 1713, 1680, 1554, 1231.
Anal. Calcd for C22H17N9O2: C, 60.13; H, 3.90; N,
28.69. Found: C, 60.00; H, 3.80; N, 28.40.
Compound 10. Brown crystals in 65% yield; mp 238–
239°C; IR: 3445, 3325, 3155, 1612, 1567, 703; Anal. Cal-
cd for C22H18N8: C, 66.99; H, 4.60; N, 28.41. Found: C,
66.70; H, 4.40; N, 28.10.
Compound 19. Brown crystals in 85% yield; mp 219–
220°C; IR: 3379, 1632, 1598, 1495, 696. Anal. Calcd
Compound 11. Brown crystals in 85% yield, mp 188–
190°C; IR: 3202, 3057, 1595, 1559, 696; Anal. Calcd

A. Deeb et al. / Bioorg. Med. Chem. Lett. 14 (2004) 5013–5017
5017
for C28H22N8: C, 71.47; H, 4.71; N, 23.82. Found: C,
71.20; H, 4.50; N, 23.60.
4.6. Decarboxylation of carboxylic acids 7 and 21
The carboxylic acid 7 and/or 21 (1g) was heated above
their melting points in an oil-bath until the evolution
of carbon dioxide subsided (about 5min). The product
which solidified on cooling was treated with aqueous so-
dium bicarbonate, filtered and recrystallized from etha-
nol.
Compound 12. Brown crystals in 95% yield, mp 273–
274°C; IR: 3399, 3184, 3099, 1686, 1572, 699; Anal. Cal-
cd for C23H19N9O: C, 63.15; H, 4.38; N, 28.82. Found:
C, 62.90; H, 4.10; N, 28.70.
Compound 14. Yellow crystals in 70% yield, mp 253–
254°C; IR: 3445, 3390, 3324, 1612, 1423, 705. Anal. Cal-
cd for C27H20N8: C, 71.04; H, 4.42; N, 24.55. Found: C,
70.80; H, 4.20; N, 24.20.
Compound 8. Brown crystals in 85% yield mp 340–
341°C; IR: 3361, 3164, 1599, 1561, 697. Anal. Calcd
for C20H14N6: C, 70.99; H, 4.17; N, 24.84. Found: C,
70.70; H, 4.00; N, 24.60.
Compound 15. Brown crystals in 80% yield, mp 182–
183°C; IR: 3181, 3057, 1598, 1499, 761; Anal. Calcd
for C33H24N8: C, 74.42; H, 4.54; N, 21.04. Found: C,
74.10; H, 4.20; N, 20.90.
Compound 22. Brown crystals in 70% yield, mp 344–
345°C; IR: 3055, 1536, 1476, 1375, 693. Anal. Calcd
for C25H16N6: C, 74.98; H, 4.03; N, 20.99. Found: C,
74.80; H, 3.90; N, 20.80.
Compound 16. Orange crystals in 95% yield, mp 264–
265°C; IR: 3398, 3183, 3105, 1669, 1571, 698. Anal. Cal-
cd for C28H21N9O: C, 67.32; H, 4.24; N, 25.24. Found:
C, 67.10; H, 4.00; N, 25.10.
Acknowledgements
The author acknowledges the help of Prof. Dr. Y. El-
Zawahry, Department of Microbiology for carrying
out the antimicrobial activity.
4.5. Hydrolysis of ethyl carboxylates 2 and 17
To a stirred solution of compounds 2 and/or 17
(1.0mmol) in ethanol (50mL) a 1N potassium hydrox-
ide solution (30mL) was added. The mixture was ref-
luxed for 1h and the solvent evaporated. The residue
was dissolved in water (20mL) and acidified with hydro-
chloric acid. The solid thus formed was filtered, washed
with water, dried and recrystallized from ethanol.
References and notes
1. For part 12: Deeb, A.; Kotb, M.; El Abbasy, M. Phospho-
rus Sulfur Silicon, in press.
2. Butter, R. N. Chem. Rev. 1975, 75, 241.
3. Deeb, A.; Kotb, M. Heterocycles 2004, 63, 1143.
4. Heinisch, G.; Kopelent, H. In Progress in Medicinal
Chemistry: Pharmacologically Active Pyridazine Deriva-
tives. Part 2; Ellis, G. P., West, G. B., Eds.; Elsevier:
Amsterdam, 1992; Vol. 29, pp 141–183.
Compound 7. Brown crystals in 65% yield, mp 242–
243°C; IR: 3424, 2922, 1703, 1631, 1599, 699. Anal. Cal-
cd for C21H14N6 O2: C, 65.96; H, 3.69; N, 21.98. Found:
C, 65.70; H, 3.40; N, 21.70.
5. Lespagnol, A.; Lespagnol, C.; Willecomme, B. Eur. J. Med.
Chem. 1974, 9, 51.
Compound 21. Yellow crystals in 55% yield, mp 264–
265°C; IR: 3420, 3160, 1624, 1541, 698. Anal. Calcd
for C26H16N6O2: C, 70.26; H, 3.63; N, 18.91. Found:
C, 70.00; H, 3.40; N, 18.70.
6. Pesske, K. German Patent 1972, 92, 457; Chem. Abstr.
1973, 78, 111676.
7. Deeb, A.; Bayoumy, B.; Hataba, A.; Fikry, R. Heterocycles
1991, 32, 901.