Synthesis and reactivity of 1-amino-4-methyl-3,4-dihydro-5H- pyrazolo[3′,4′:4,5]pyrimido[1,6-a]benzoimidazolo-5-one

Article abstract of DOI:10.1002/jhet.5570440330

(Chemical Equation Presented) Pyrimido[2″,1″:5′,6′] pyrazolo[3′,4′:4,5]-pyrimido[1,6-a]benzoimidazoloe-2,8(1H,7H) -diones, and [1,2,4]-triazino-[3″,4″:5′,6′] pyrazolo[3′,4′:4,5]pyrimido[1,6-a]benzimidazol-8(7H)-ones were synthesized in a good yields via 1

Full text of DOI:10.1002/jhet.5570440330

May-Jun 2007
701
Synthesis and Reactivity of 1-Amino-4-methyl-3,4-dihydro-5H-
pyrazolo[3',4':4,5]pyrimido[1,6-a]benzoimidazolo-5-one
Abdou O. Abdelhamid* and Ahmed A. Awad
Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt.
Abdou_abdelhamid@yahoo.com.
Received March 11, 2006
O
CH3
N
N
N
N
N
X
N
O
CH3
N
Y
N
NH
N
N
CH3
O
H2N
N
N
N
N
z
N
N
N
G
Pyrimido[2'',1'':5',6']pyrazolo[3',4':4,5]-pyrimido[1,6-a]benzoimidazoloe-2,8(1H,7H)-diones, and [1,2,4]-
triazino-[3'',4'':5',6']pyrazolo[3',4':4,5]pyrimido[1,6-a]benzimidazol-8(7H)-ones were synthesized in a good
yields via 1-amino-4-methyl-3,4-dihydro-5H-pyrazolo[3',4':4,5]pyrimido[1,6-a]benzoimidazolo-5-one and
the appropriate active methylene compounds. Structures of the newly synthesized compounds were
elucidated on the basis of elemental analyses, spectral data, and alternative synthesis methods whenever
possible.
J. Heterocyclic Chem., 44, 701 (2007).
benzimidazo-4-carbonitrile (2). Structure
2
was
INTRODUCTION
1
confirmed by elemental analysis, its H NMR spectrum
and chemical transformations. When compound 2 is
reacted with hydrazine hydrate in boiling ethanol under
reflux 1-amino-4-methyl-3,4-dihydro-5H-pyrazolo-
[3',4':4,5]pyrimido[1,6-a]benzoimidazolo-5-one (3) is
obtained (Scheme 1).
Benzimidazoles are one of the most extensively studied
classes of heterocyclic compounds owing partly to their
biological activities such as anticonvulsant [1], sedative
[1], immunosuppresant [1], antitumor [1], antihistaminic
[1] and antifugal [2]. There is considerable interest in
exploring new stereoselective synthesis [3] and biological
evaluation of new benzimidazole derivatives [4] despite
the existence of numerous synthetic methods of
benzimidazole derivatives [5]. As an extension of our
study [6,7] and as a part of our program aiming at the
synthesis of different fused benzimidazoles, we report
here the reactivity of 1-amino-4-methyl-3,4-dihydro-5H-
pyrazolo[3',4':4,5]pyrimido[1,6-a]benzoimidazolo-5-one.
1
Structure 3 was confirmed by elemental analysis, H
NMR and IR spectra and chemical transformations. The
IR spectrum of 3 revealed bands at 3340, 3312, 3280
1
(NH2, NH), 1706 (CO) and 1580 (C=C). Its H NMR
spectrum showed signals at ꢀ = 3.39 (s, 3H), 6.37 (s, br.,
2H), 7.23-7.38 (m, 2H), 7.60-7.64 (d, 1H), 8.22-8.26 (d,
1H) and 11.8 (s, br., 1H).
CH3
CH3
CH3
O
O
O
N
N
N
SH
CN
SCH3
CN
CH3I
N
N2H4.H2O
N
N
N
NH
N
N
N
H2N
1
2
3
Scheme 1
RESULTS AND DISCUSSION
Compound 3 reacted with 2,4-pentandione in boiling
acetic acid under reflux afforded 2,4,6-trimethylbenz-
imidazolo[1'',2'':1',6']pyrazolo[4',5':4,3]-pyrazolo[1,5-a]-
pyrimidin-7-one (4) (Scheme 2).
Treatment of 1 with iodomethane [8] gave 2-methyl-
3-(methylsulfanyl)-1-oxo-1,2-dihydropyrimido[1,6-a]-

702
A.O. Abdelhamid and A.A. Awad
Vol 44
CH3
O
CH3
O
N
N
N
N
N
N
N
CH3
N
NH
N
HN
HN
COCH2COCH3
6
O
5
CH3
CH3
O
O
N
N
N
N
N
N
3
Ph
N
CH3
N
N
N
HN
N
O
CH3
7
4
Scheme 2
Also, when 3 is reacted with ethyl 3-oxobutanoate in
boiling acetic acid the product formulated as 4,6-
dimethyl-1,6,4a,7a-tetrahyderobenzimidazolo[1'',2'':1',6']-
pyrimidino [4',5':4,3]pyrazolo[1,5-a]pyrimidine-2,7-dione
(6) was obtained. Also, when 3 is reacted with
acetacetanilide the product obtained is identical in all
respects (mp., mixed mp. and spectra) with 6. This
reaction seemed to proceed through the elimination of
ethanol (or aniline) to give intermediate 5, which
underwent cyclization via elimination of a water molecule
to afford the final product 6.
imidazolo-[1'',2'':1',6']pyrimido[4',5':4,3]pyrazolo[1,5-a]-
pyrimidine-2,7-dione (7), as shown by elemental analysis
and spectral data.
However, treatment of 3 with ꢀ-cyanocinnamonitrile in
boiling ethanol, containing catalytically amount of
piperidine, under reflux gave 4-amino-7-methyl-8-oxo-2-
phenyl-7,8-dihydropyrimido[2'',1'':5',6']pyrazolo[3',4':4,5]-
pyrimido[1,6-a]benzimidazole-3-carbonitrile (9) (Scheme
3). Structure 9 was elucidated by elemental analysis,
1
spectral data and alternative synthesis. Thus, H NMR
spectrum showed signals at ꢁ = 3.55 (s, 3H), 6.52 (s, br.,
2H), 7.35-7.42 (m, 7H), 7.71-7.74 (d, 1H) and 8.26-8.31
(d, 1H). Its IR spectrum revealed bands at 3305, 3244
(NH2), 2187 (CN), 1721 (CO) and 1612 C=N). Also,
Similarly, when 3 is reacted with each of ethyl 3-oxo-3-
phenylpropanoate and 2-benzoylacetanilide the product
obtained is 6-methyl-4-phenyl-1,6,4a,7a-tetrahydrobenz-
CH3
O
CH3
O
N
N
N
N
N
N
N
N
NH
CN
N
NH2
CN
N
HN
N
9
8
Ph
Ph
ii
i
CH3
O
N
i = PhCH =C(CN)2
ii = CH2(CN)2
N
N
v
NH
iii = PhCH =C(CN)CO2C2H5
iv = NCCH2CO2C2H5
v = PhCHO
3
N
N
Ph
iii
10
iv
iii
CH3
O
CH3
O
N
N
N
N
N
N
O
N
NH2
N
N
N
N
N
CN
CO2C2H5
Ph
Ph
12
Scheme 3
11

May-Jun 2007
Synthesis and reactivity of pyrazolo[3',4':4,5]pyrimido[1,6-a]benzoimidazolo-5-one
703
treatment of 5-(1-aza-2-phenylvinyl)-2-methyl-2,10b-
dihydrobenzimidazolo[1,2-e]pyrazolo[3,4-d]pyrimid-in-1-
one (10), which was prepared via reaction of 3 with
benzaldehyde, with malononitrile in boiling ethanol in the
presence of a catalytical amount of piperidine gave
product identical in all respects (mp., mixed mp. and
spectra) with 9. The reaction seemed to be proceeding
through Michael addition of active methylene to
(-N=CHPh) to give the intermediate 8, which underwent
cyclization and autoxidation to give 9 (Scheme 3).
[1,2,4]triazino[4'',3'':1',5']pyrazolo[3,4-d]pyrimidin-7-one
(14).
Also, treatment of 13 with ethyl 3-oxobutanoate gave,
one isolable product according to tlc, which seemed to
correspond to 15 or isomeric 16. Its IR spectrum revealed
bands at 1720, 1663 (CO’s) and 1604 (C=C); mass
spectrum of the product showed peaks at m/z = 379
(3.3%, M+2), 378 (23.3%, M+1), 377 (100%, M), 348
(4%, M-C2H5), 332 (9.7%, M-OC2H5), 304 (11.9%, M-
C2H5CO2), 248 (15.7%), 182 (10.4%), 90 (43.2%) and 67
(18.4%). Based on this data the product was formulated
as: ethyl 4,6-dimethyl-7-oxo-6,7a-dihydrobenzimidazolo-
[1,2-e]-[1,2,4]triazino[4',3':1,5]-pyrazolo[3,4-d]pyrimidine-
3-carboxylate (15) while isomeric structure 16 was ruled
out (Scheme 4).
Similarly, 13 reacted with malononitrile in ethanolic
sodium acetate at 0°C afford 4-amino-6-methyl-7-oxo-
6,7a-dihydrobenzimidazolo[1,2-e][1,2,4]triazino-[4',3':1,5]-
pyrazolo[3,4-d]pyrimidine-3-carbonitrile (17). Structure
17 was elucidated by elemental analysis and spectral data.
Thus, the IR spectrum revealed bands at 3343, 3260
(NH2), 2213 (CN), 1718 (CO’s), 1641 (C=N) and 1605
(C=C). Its mass spectrum showed a peak at m/z 331
(100%, M).
Similarly, ethyl 2-cyano-3-phenylacrylate reacted
with 3 in boiling ethanol under reflux to give a product
that seemed to correspond to structure 11 or isomeric
structure 12. The IR spectrum reveals bands at, 3313,
3177 (NH2), 1704 (CO), 1622 (C=N), 1612 (C=C) and
no absorption band in the region 2100-2300 cm-1 is
1
observed thus verifying the absence of CN group. H
NMR spectrum showed signals at ꢀ = 1.31 (t, J= 7.2
Hz, 3H), 3.62 (s, 3H), 4.22 (q, J = 7.2 Hz, 2H), 6.52 (s,
br., 2H), 7.31-7.72 (m, 7H), 7.76-7.82 (d, 1H) and
6.21-8.26 (d, 1H). Foregoing data the product was
formulated as: ethyl 4-amino-7-methyl-8-oxo-2-phenyl-
6,4a,7a-trihydropyrimido-[1'',2'':1',6']pyrimidino[4',5':4,3]-
pyrazolo[1,5-a]pyrimid-ine-3-carboxylate (12).
CH3
O
N
N
N
CH3
O
CH3
N
N
N
N
N
N
N
N
CH3
N
CO2C2H5
15
N
N
COCH3
CH3
O
14
N
N
N
CH3
O
O
N
N
N
N
N
N
N
COCH3
NH
3
16
N
-
+
Cl N2
CH3
13
O
N
N
N
N
NH2
CN
CH3
CH3
N
O
O
N
N
N
N
N
N
N
N
N
N
17
NH2
O
N
N
N
N
N
N
CO2C2H5
CN
19
18
Scheme 4
Next, treatment of diazonium chloride 13, which was
prepared by reaction of 3 with nitrous acid, with 2,4-
pentandione in ethanolic sodium acetate solution gave 3-
acetyl-4,6-dimethyl-6,7a-benzimidazolo[1,2-e]dihydro-
Finally, treatment of 13 with ethyl cyanoacetate in
ethanolic sodium acetate solution gave a product
formulated as ethyl 4-amino-6-methyl-87-oxo-6,7a-di-
hydrobenz-imidazolo[1,2-e][1,2,4]triazino[4',3':1,5]py-

704
A.O. Abdelhamid and A.A. Awad
Vol 44
Table 1
Characterization data of the newly synthesized compounds.
Compound
Mp
(°C)
ColourYield
%
Molecular
Formula
Analysis %
Calcd./Found
C
H
N
S
2
222-25
DMF
>300
AcOH
>300
DMF
>300
DMF
>300
AcOH
>300
AcOH
>300
DMF
>300
AcOH
>300
AcOH
>300
AcOH
>300
AcOH
>300
AcOH
Yellow
65
Colorless
73
Pale Yellow
45
Colorless
52
Pale Yellow
60
Yellow
55
Yellow
62
Pale Yellow
49
Yellow
72
Yellow
82
Yellow
67
Pale Yellow
78
C13H10N4OS
C12H10N6O
C17H14N6O
C16H12N6O2
C21H14N6O2
C22H14N8O
C19H14N6O
C24H19N7O3
C17H13N7O2
C18H15N7O3
C15H9N9O
57.76
57.62
56.69
56.90
64.14
64.20
60.00
60.12
65.96
65.82
65.02
65.12
66.66
66.46
63.57
63.92
58.79
58.90
57.29
57.00
54.38
54.36
53.97
54.12
3.73
3.54
3.96
3.68
4.43
4.30
3.78
3.97
3.69
3.65
3.47
3.51
4.12
4.00
4.22
4.24
3.77
3.60
4.01
3.90
2.74
2.79
3.73
3.80
20.73 11.86
20.75 11.55
3
33.05
32.90
26.40
26.30
26.24
26.40
21.98
21.80
27.57
27.70
24.55
24.34
21.62
21.90
28.23
28.10
25.98
25.91
38.05
37.85
29.62
29.70
-
-
-
-
-
-
-
-
-
-
-
4
6
7
9
10
12
14
15
17
19
C17H14N8O3
Table 2
Spectra of the newly synthesized compounds.
Compound Spectral data
2
3
1HNMR (CDCl3): ꢀ = 2.77 (s, 3H), 3.76 (s, 3H), 7.42-7.57 (m, 2H), 7.80-7.84 (d, 1H) and 8.22-8.26 (d, 1H).
IR: 2218 (CN) and 1711 (CO).
1H NMR (CDCl3): ꢀ = 3.39 (s, 3H), 6.37 (s, br., 2H), 7.23-7.38 (m, 2H), 7.60-7.64 (d, 1H), 8.22-8.26 (d, 1H) and 11.8 (s, br., 1H).
IR: 3340, 3312, 3280 (NH2, NH), 1706 (CO) and 1580 (C=C).
4
1H NMR (CDCl3): ꢀ = 2.71 (s, 6H), 3.75 (s, 3H), 6.71 (s, 1H), 7.27-7.42 (m, 2H), 7.82-7.87 (dd, 1H) and 8.34-8.39 (dd, 1H).
IR: 3236 (NH), 1713, 1659 (CO’s) and 1605 (C=C).
6
1H NMR (CDCl3): ꢀ = 2.72 (s, 3H), 3.55 (s, 3H), 6.75 (s, 1H), 7.35-7.42 (m, 2H), 7.72-7.76 (d, 1H), 8.29-8.34 (d, 1H) and 13.37 (s, br., 1H).
IR: 3252 (NH), 1709, 1657 (CO’s), 1611 (C=N) and 1578 (C=C).
7
1H NMR (CD3)2SO: ꢀ = 3.55 (s, 3H), 6.52 (s, br., 1H), 7.35-7.42 (m, 7H), 7.71-7.74 (d, 1H), 8.26-8.31 (d, 1H) and 13.31 (s, br., 1H).
IR: 3433, 3305, 3244 (NH, NH2), 2187 (CN), 1721 (CO) and 1612 C=N).
1H NMR (CD3)2SO: ꢀ = 3.62 (s, 3H), 6.52 (s, br., 2H), 7.31-7.72 (m, 7H), 7.76-7.82 (d, 1H) and 6.21-8.26 (d, 1H).
IR: 3406, 3313, 3177 (NH, NH2), 1704 (CO), 1622 (C=N) and 1612 (C=C).
IR: 1712, 1697, (CO’s), 1660 (C=N) and 1602 (C=C).
MS: 344 (18.6 %, M+2), 343 (100%, M+1), 342 (87%, M), 320 (10.7%), 304 (4.92), 254 (8.5%), 181 (10.1%), 90 (28%) and 67 (15%).
1H NMR (CDCl3): 1.31(t, J = 7.2 Hz, , 3H), 3.62 (s, 3H), 4.22 (q, J = 7.2 Hz, 2H), 6.52 (s, br., 2H), 7.31-7.72 (m, 7H), 7.76-7.82 (d,
1H) and 8.21-8.26 (d, 1H).
9
10
12
IR: 1720, 1663 (CO’s) and 1604 (C=C).
MS: 453 (100%, M+), 424 (4%, M-C2H5), 408 (9.7%, M-OC2H5), 380 (11.9%, M- C2H5CO2), 248 (15.7%), 182 (10.4%), 90 (43.2%) and
67 (18.4%).
14
15
17
19
1H NMR: (insoluble)
IR: 3443, 3260 (NH2), 1718 (CO’s), 1641 (C=N) and 1605 (C=C).
MS: 347 (100%, M+).
1H NMR: (insoluble)
IR: 3343, 3260 (NH2), 1712, 1618 (CO’s), 1641 (C=N) and 1605 (C=C).
MS: 379 (3.3%, M+2), 380 (23.3%, M+1), 377 (100%, M), 380 (3.3%), 306 (17%), 254 (39.2%), 182 (17.5%) and 90 (16.8%).
1HNMR (CD3)2SO: ꢀ = 3.76 (s, 3H), 6.23 (s, br., 2H), 7.42-7.57 (m, 2H), 7.80-7.84 (d, 1H) and 8.22-8.26 (d, 1H).
IR: 3343, 3260 (NH2), 2213 (CN), 1718 (CO), 1641 (C=N) and 1605 (C = C).
MS: 331 (100%, M).
1H NMR (CD3)2SO: ꢀ = 1.30 (t, J = 7.2, 3H), 3.62 (s, 3H), 4.22 (q, J = 7.2 Hz), 6.52 (s, br., 2H), 7.23-7.38 (m, 2H), 7.60-7.64 (d, 1H),
8.22-8.26 (d, 1H).
IR: 3340, 3312, 3280 (NH2, NH), 1706 (CO) and 1580 (C=C).
MS: 380 (3.3%, M+2), 379 (23.3%, M+1), 378 (100%, M), 306 (17%), 254 (39.2%), 192 (17.5%), and 90 (16.8%)

May-Jun 2007
Synthesis and reactivity of pyrazolo[3',4':4,5]pyrimido[1,6-a]benzoimidazolo-5-one
705
of piperidine (3 drops) was boiled under relux for 2 hrs. The
resulting solid was collected and recrystallized from N,N-
dimethylformamide to give 10 (Tables 1 and 2).
razolo[3,4-d]-pyrimidine-3-carboxylate (19). Its
mass spectrum showed peaks m/z at = 380 (3.3%,
M+2), 379 (23.3%, M+1), 378 (100%, M), 306
(17%), 254 (39.2%), 182 (17.5%) and 90 (16.8%).
Synthesis of Benzimidazolo[1'',2'':1',6']pyrimidino[4',5':
4,3]-pyrazolo[1,5-a]pyrimidine derivatives 14, 15, 17and 19.
Diazonium chloride 13 (which was prepared via addition sodium
nitrite solution (0.35g, (5 mmol), 10 mL water) to a mixture of 3
(2.15 g, 5 mmol), acetic acid (1 mL) and hydrochloric acid (3 mL,
6 M)) at 0°C) was added dropwise to a cold solution of each of
2,4-pentandione, ethyl 3-oxobutanoate, malononitrile or ethyl
cyanoacetate (5 mmol each), sodium acetate (1 g) in ethanol (50
mL) while stirring at 0-5°C. The reaction mixture was stirred 3 hrs
the resulting solid was collected and recrystallized from acetic
acid to give 14, 15, 17 and 19, respectively (Tables 1 and 2).
EXPERIMENTAL
All melting points were determined on an electrothermal
apparatus and are uncorrected. IR spectra were recorded (KBr
1
discs) on a Shimadzu FT-IR 8201 PC spectrophotometer. H
NMR spectra were recorded in CDCl3 or (CD3)2SO solutions on
a Varian Gemini 300 MHz spectrometer and chemical shifts are
expressed in ꢀ units using TMS as an internal reference. Mass
spectra were recorded on a GC-MS QP1000 EX Shimadzu.
Elemental analyses were carried out at the Microanalytical
Center of the Cairo University
REFERENCES AND NOTES
Synthesis of 2-methyl-3-(methylsulfanyl)-1-oxo-1,2-
dihydroyrimido[1,6-a]benzimidazo-4-carbonitrile (2). A
mixture of 2-(1-ethoxycarbonoyl)benzimidazolylacetonitrile,
methyl isothiocyanate, potassium hydroxide (5 mmol each) in
N,N-dimethylformamide (15 mL) was stirred for 6 hrs.
Iodomethane (0.72 g, 5 mmol) was added while stirring and the
reaction mixture was stirred for 2 hrs. The resulting solid was
collected and recrystallized from N,N-dimethylformamide to
give 2 (Tables 1 and 2).
Synthesis of 1-amino-4-methyl-3,4-dihydro-5H-pyrazolo-
[3',4':4,5]pyrimido[1,6-a]benzoimidazolo-5-one (3). A mixture
of 2 (2.18 g, 5 mmol) and hydrazine hydrate (1 mL, 99%) in
ethanol (20 mL) was boiled under reflux for 4 hrs. The resulting
solid was collected and recrystallized from acetic acid to give 3
(Tables 1, 2).
Synthesis of 4, 6 and 7. Equimolar amounts aminopyrazole 3
and the appropriate 2,4-pentandione, ethyl acetoacetate (or aceto-
acetanilide) or ethyl benzoylacetate (or benzoylacetanilide) (5
mmol) in acetic acid (20 mL) were heated under reflux for 3 hrs.
The resulting solid was collected and recrystallized from N,N-
dimethylformamide to give 4, 6 and 7, respectively (Tables 1 and 2).
Synthesis of 9 and 12. Equimolar amounts of aminopyrazole 3
and the appropriate ꢁ-substituted cinnamonitrile (5 mmol each) in
ethanol (20 mL) containing catalytical amount of piperidine (3
drops) was boiled under reflux for 2 hrs. The resulting solid was
collected and recrystallized from N,N-dimethylformamide to give
9 and 12, respectively (Tables 1 and 2).
[1a] Jassen, f; Torremans, J.; Jassen, M.; Stokbroekx, R. A.;
Luyckx, M.; Janssen, P. A. J. J. Med. Chem., 1985, 28, 1934; [b]
Bonsignore, L.; Loy, G.; Secci, D. J. Heterocycl. Chem.,, 1992, 29,
1033.
[2a] Ogata, M.; Matsumoto, H.; Takahashi, K.; Shimizu, S.; Kida,
S.; Murabayashi, A.; Shiro, M.; Tawara, K. J. Med. Chem., 1987, 30,
1054; [b] Moreno-Manas, M; Teixido, M. J. Heterocycl. Chem, 1988,
25, 439.
[3a] Lꢀpez-Rodriguez, M. L.; Benhamꢁu, B.; Viso, A.;. Morcillo,
M. J.; Murcia, M.; Orensanz, L.; Alfaro, M. J.; Martin,, M. I. Bioorg.
Med. Chem Lett., 1999, 7, 2271; [b] Hamaguchi, T.;Takahashi, A.;
Kagamizono, T.; Manaka, A.; Sato, M.; Osada, H. Bioorg. Med.
Chem.,Lett., 2000, 10, 2657; [c] Nakano, H.; Inoue, T.; Kawasaki, N.;
Miyataka, H.; Matsumoto, H.; Taguchi, T.; Inagaki, N.; Nagai, , H.;
Satoh, T. Bioorg. Med.Chem. Lett., 2000, 8, 373.
[4a] Pernak, J; Rogoza, J.; Mirska, I. Eur. J. Med. Chem., 2001,
36, 313; [b] Xiao, G.; Kumar, A.; Li, K; T.Rigl, C. T.; Bajic, M.; Davis,
T. M.; Boykin, D. W.; Wilson, W. D. Bioorg. Med. Chem., 2001, 9,
1097; [c] Phoon, C. W.; Ng, P. Y.; Ting, A. E.; Yeo, S. L.; Sim, M. M.
Bioorg & Med. Chem., 2001, 11, 1647; [d] Lukevics,E.; Arsenyan, P.;
Shestakova, I.; Domracheva, I.; Nesterova, A.; Pudova, O. Eur. J. Med.
Chem.,2001, 36, 507.
[5a] Grimmett, M. R. In Comprehensive Heterocyclic Chemistry
II, Ed, by A. R. Katritzky, C. W. Rees, and E. F. V. Scriven, Pergamon
Press, New York, 1996, Vol. 3, pp. 79 – 220; [b] Grimmett, M. R. In
Comprehensive Heterocyclic Chemistry, Ed. by A. R. Katritzky and C.
W. Rees, Pergamon Press, Oxford, 1984, Vol. 5, pp. 345- 498.
[6] Abdelhamid, A. O.; Zohdi, H. F.; Ziada, M. M. Indian J.
Chem., Sect. B, 2000, 9B, 202.
[7] Abdelhamid, A. O.; Zohdi, H. F.; Ziada, M. M. Indian J.
Chem., Sect. B, 2000, 40B, 284.
[8] Abdelhamid, A. O.; Elghandour, A. H.; Rateb, N. M.;. Awad,
A. M. Phosphorous, Sulfur, Silicon and Related Elements, 2006, 181,
1637.
5-(1-Aza-2-phenylvinyl)-2-methyl-2,10b-dihydrobenzimi-
dazolo[1,2-e]pyrazolo[4,3-d]pyridine-1-one (10). Equimolar
amounts of aminopyrazole 3 and the appropriate benzaldehyde
(5 mmol each) in ethanol (20 mL) containing catalytical amount