Synthesis and antitumor evaluation of some newly synthesized pyrazolopyrimidine and pyrazolotriazolopyrimidine derivatives

Article abstract of DOI:10.1080/10426500802713267

A series of novel pyrazolo[3,4-d]pyrimidine 2b, 3, 5b, pyrazolotetrazolopyrimidine 4, and pyrazolotriazolopyrimidine derivatives 6a,b-10a,b have been synthesized and characterized by elemental analysis and spectroscopic data. Furthermore, the cytotoxicity and in vivo antitumor evaluation of some prepared compounds have been assessed, and derivatives 1a and 6b revealed promising activity in comparison to that of Cisplatin. Supplemental materials are available for this article. Go to the publisher′s online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Full text of DOI:10.1080/10426500802713267

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Synthesis and Antitumor
Evaluation of Some Newly
Synthesized Pyrazolopyrimidine and
Pyrazolotriazolopyrimidine Derivatives
Aymn E. Rashad a , Mohamed I. Hegab a , Randa E. Abdel-Megeid a
Mamdouh M. Ali b & Farouk M. E. Abdel-Megeid a
,
a Photochemistry Department , National Research Centre , Dokki,
Cairo, Egypt
b Biochemistry Department , National Research Centre , Dokki,
Cairo, Egypt
Published online: 28 Dec 2009.
To cite this article: Aymn E. Rashad , Mohamed I. Hegab , Randa E. Abdel-Megeid , Mamdouh M. Ali
& Farouk M. E. Abdel-Megeid (2009) Synthesis and Antitumor Evaluation of Some Newly Synthesized
Pyrazolopyrimidine and Pyrazolotriazolopyrimidine Derivatives, Phosphorus, Sulfur, and Silicon and
the Related Elements, 185:1, 74-83
To link to this article: http://dx.doi.org/10.1080/10426500802713267
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Phosphorus, Sulfur, and Silicon, 185:74–83, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802713267
SYNTHESIS AND ANTITUMOR EVALUATION OF SOME
NEWLY SYNTHESIZED PYRAZOLOPYRIMIDINE AND
PYRAZOLOTRIAZOLOPYRIMIDINE DERIVATIVES
Aymn E. Rashad,1 Mohamed I. Hegab,1
Randa E. Abdel-Megeid,1 Mamdouh M. Ali,2
and Farouk M. E. Abdel-Megeid1
1Photochemistry Department, National Research Centre, Dokki, Cairo, Egypt
2Biochemistry Department, National Research Centre, Dokki, Cairo, Egypt
A series of novel pyrazolo[3,4-d]pyrimidine 2b, 3, 5b, pyrazolotetrazolopyrimidine 4, and
pyrazolotriazolopyrimidine derivatives 6a,b–10a,b have been synthesized and characterized
by elemental analysis and spectroscopic data. Furthermore, the cytotoxicity and in vivo
antitumor evaluation of some prepared compounds have been assessed, and derivatives 1a
and 6b revealed promising activity in comparison to that of Cisplatin.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental
file.
Keywords Antitumor activity; pyrazolo[3,4-d]pyrimidine; pyrazolotetrazolopyrimidine; pyra-
zolotriazolopyrimidine
INTRODUCTION
In the last few decades, the chemistry of pyrazolopyrimidines has received consid-
erable attention due to their synthetic and effective biological importance.1–3 Also, due to
the presence of pyrazolo[3,4-d]pyrimidine moiety in some important drugs, and because of
their structural resemblance to purines, interest in the construction of such molecules has
been aroused.4,5 Several substituted pyrazolo[3,4-d]pyrimidine derivatives demonstrated
significant antimicrobial,6 antimycobacterial,7 antitumor,8 and antiviral activity.9,10
As a continuation of our work on azoloazines,6,10–13 we aimed to incorporate a fused
pyrimidine moiety into the 1-position of the pyrazolo[3,4-d]pyrimidine ring system to
obtain a new heterocyclic system, which was used as a building block for many fused
heterocyclic pyrazolotriazolopyrimidines expected to possess notable chemical and phar-
macological activities.12–15 In addition, triazolopyrimidines often display increased toxicity
and improved antitumor properties when compared to those of purines.16,17
Received 31 October 2008; accepted 15 December 2008.
Address correspondence to Aymn E. Rashad, Photochemistry Department, National Research Centre, Dokki,
Cairo 12622, Egypt. E-mail: aymnelzeny@yahoo.com
74

PYRAZOLOPYRIMIDINE AND PYRAZOLOTRIAZOLOPYRIMIDINE DERIVATIVES
75
DISCUSSION
Chemistry
Compounds 1a18 and 1b18 were converted into their corresponding 4-chloro deriva-
tives 2a10 and 2b, respectively, when heated with phosphorus oxychloride at reflux temper-
ature. The mass spectra of compounds 2a10 and 2b gave fragments showing the isotopic
pattern due to the presence of a chlorine atom (see the Experimental section and ref.10).
When derivatives 2a10 and 2b were treated with sodium azide in glacial acetic acid
at 70◦C, they afforded compounds 3 and 4, respectively. Analytical and spectral data of
the latter compounds are in agreement with the proposed structures. In particular, the IR
spectrum of compound 3 showed an absorption frequency at 2188 cm−1 indicative for the
azido group, while IR spectrum of compound 4 did not. This data indicates that compound 3
has the azido structure, without excluding the tetrazolo structure in tautomeric equilibrium;
while compound 4 has only the tetrazolo structure (Scheme 1).
Scheme 1
The absence of the azido group and the formation of the tetrazolo structure in com-
pound 4 may be due to the electron-donating effect of the CH3 group, which stabilizes the
tetrazolo structure.
Meanwhile, when compounds 2a10 and 2b were treated with hydrazine hydrate
at reflux temperature, they afforded the corresponding hydrazino derivatives 5a18 and
1
5b, respectively. The IR and H NMR spectra of the latter compounds revealed signals
characteristic for NH2 and NH, and their MS gave the molecular ion peaks as base peaks
(see the Experimental section).

76
A. E. RASHAD ET AL.
On the other hand, the synthesis of [1,2,4]triazolo[4,3-c]pyrimidines and
[1,2,4]triazolo[1,5-c]pyrimidines fused to nitrogen-rich heterocyclic moieties have
attracted the attention of many investigators,19–21 and many derivatives have been
described and proved to have pronounced biological activities.16,17,22–25 Actually, previous
observations revealed that [1,2,4]triazolo[4,3-c]pyrimidines can isomerize by a Dimroth
rearrangement under different reaction conditions (acid, base, or heat) to the more
thermodynamically stable [1,2,4]triazolo[1,5-c]pyrimidine.13,23,24
Thus, heating compounds 5a18 or 5b with formic acid or triethyl orthoformate at
reflux temperature gave compounds 6a and 6b or 7a and 7b, respectively (Scheme 2).
Likewise, heating of compounds 5a18 or 5b with acetic acid/acetic anhydride at reflux
temperature or triethyl orthoacetate at room temperature gave compounds 8a and 8b or
1
9a and 9b, respectively (Scheme 2). The H NMR spectra of triazolo[4,3-c]pyrimidine
derivatives 7a,b or 9a,b revealed that the substituents at C-3 and C-5 showed signals
more downfield than those in their isomeric triazolo[1,5-c]pyrimidine derivatives 6a,b
or 8a,b at C-2 and C-5. This confirmed that the products obtained from the reaction
of the hydrazino derivatives 5a18 and 5b with orthoesters differ than those obtained
from the reaction with acids. The spectral data revealed not only this observation, but
also the physical data, where the melting points (mp) and rates of flow (Rf values) of
triazolo[4,3-c]pyrimidine derivatives were higher than those of triazolo[1,5-c]pyrimidine
derivatives.
It was noticed that when triazolo[4,3-c]pyrimidine derivatives 7a,b and 9a,b were
heated in acid medium, they isomerized to the thermodynamically more stable triazolo[1,5-
c]pyrimidine derivatives 6a,b and 8a,b, respectively. These results and isomerizations were
in agreement with those reported in some recent reports.12,13,23–25
In contrast, when compounds 5a18 and 5b were heated at reflux temperature with
triethyl orthoacetate, two products were isolated and were separated on a silica gel column;
one of them was the expected triazolo[4,3-c]pyrimidine derivative 9a,b and the other was
the triazolo[1,5-c]pyrimidine derivatives 8a,b (Scheme 2). The formation of compound
8a,b in this reaction can be accounted by the partial isomerization via a Dimroth reaction
of product 9a,b under the effect of heat.
In addition, benzoylation of compounds 5a18 and 5b with benzoyl chloride, in
phosphorus oxychloride, yielded substituted triazolo[1,5-c]pyrimidine derivatives 10a and
10b, respectively (Scheme 2). The spectral data and elemental analyses of compounds
6a,b–10a,b confirmed their structures.
Antitumor Activity
As shown in the Supplementary Materials (available online; Table I, Figures 1 and
2), in the ascites tumor model, the administration of prepared compounds significantly
increased (P < 0.05) the life span of the animals as compared with the control group
(animals in the EAC injected alone) except compound 5a, which revealed an insignificant
change. There is a gradual increase in life span using the prepared compounds from
compound 5a, 8a, 6a, and 6b to compound 1a. The increase in life span was 9%, 32%,
45%, 64%, and 73%, respectively. The standard reference drug (Cisplatin 2 mg/kg body
weight [b. w.]) exhibited an 86% (P < 0.05) increase in life span of the animals. All the
animals in the EAC-injected alone group were dead after 22 days.

PYRAZOLOPYRIMIDINE AND PYRAZOLOTRIAZOLOPYRIMIDINE DERIVATIVES
77
Scheme 2
EXPERIMENTAL
Chemistry
All melting points are uncorrected and were measured using an Electro-thermal IA
9100 apparatus (Shimadzu, Japan). IR spectra were recorded as potassium bromide pellets

78
A. E. RASHAD ET AL.
1
on a Perkin-Elmer 1650 Spectrophotometer, National Research Centre, Cairo, Egypt. H
NMR and 13C NMR spectra were determined on a Jeol-Ex-300 NMR spectrometer, and
chemical shifts were expressed as part per million; ppm (δ values) against TMS as internal
reference (Faculty of Science, Cairo University, Cairo, Egypt). Mass spectra were recorded
on EI + Q1 MSLMR UPLR, National Research Centre, Cairo, Egypt. Microanalyses were
operated using Mario Elmentar apparatus, Organic Microanalysis Unit, National Research
Centre, Cairo, Egypt, and the results were within the accepted range of the calculated
values. Column chromatography was performed on (Merck) Silica gel 60 (particle size
0.06–0.20 mm).
Compounds 1a,18 1b,18 2a,10 and 5a18 were prepared as reported in the literature.
4-Chloro-6-methyl-1-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno
[2,3-d]pyrimidin-11-yl)-1H-pyrazolo[3,4-d]pyrimidine (2b)
Compound 1b,18 (0.01 mol) was refluxed in phosphorus oxychloride (20 mL) for 2
h. The solution was cooled and poured with stirring onto ice, and the solid that formed
was filtered off, washed several times with water, dried, and purified on silica gel column
using petroleum ether: ethyl acetate (3:1) as an eluent to give compound 2b. Yield 80%,
mp 190–192◦C; IR νmax 1534 cm−1 of the C N, and absence of the C O and NH groups;
1H NMR (DMSO-d6): δ 2.56 (s, 3H, C6 CH3), 2.90–3.00 (m, 4H, C5 CH2+C6 CH2),
ꢁ
ꢁ
ꢁ
7.20–7.30 (m, 4H, 3Ar H+C3 H), 8.00 (s, 1H, C9 H), 8.35 (d, 1H, Ar H, J = 7.5 Hz);
EIMS, m/z (%): 406 (M+, 37Cl, 39.98), 404 (M+, 35Cl, 100); Anal. calcd. for C20H13ClN6S
(404.06): C, 59.33; H, 3.24; N, 20.76; S, 7.92. Found: C, 59.45; H, 3.56; N, 20.87; S,
7.61.
Synthesis of 3 and 4
A mixture of compound 2a10 or 2b (0.01 mol) was added to glacial acetic acid (20
mL) containing sodium azide (0.01 mol) with stirring at 70◦C for 1 h. Then the reaction
mixture was cooled, filtered, washed with a small amount of water then cold ethanol, dried,
and recrystallized from ethanol to give compound 3 or 4, respectively.
4-Azido-1-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-1H
-pyrazolo[3,4-d]pyrimidine (3). Yield 60%, mp 216–218◦C; IR νmax 2188 cm−1 of
1
ꢁ
ꢁ
the azide group; H NMR (DMSO-d6): δ 2.80–3.00 ppm (m, 4H, C5 -CH2+C6 -CH2),
ꢁ
7.20–7.30 (m, 4H, 3Ar H+C3 H), 8.10 (s, 1H, C9 H), 8.35 (d, 1H, Ar H, J = 7.50
Hz), 8.90 (s, 1H, C6 H); Anal. calcd. for C19H11N9S (397.42): C, 57.42; H, 2.79; N,
31.72; S, 8.07. Found: C, 57.52; H, 2.54; N, 31.91; S, 8.23.
5-Methyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-
7H-pyrazolo[4,3-e][1,2,4]tetrazolo[1,5-c]pyrimidine (4). Yield 54%, mp 235–
237◦C; IR νmax absence of the azide group; H NMR (DMSO-d6): δ 2.60 ppm (s, 3H,
1
ꢁ
ꢁ
C5 CH3), 2.90–3. 00 (m, 4H, C5 CH2+C6 CH2), 7.20–7.30 (m, 4H, 3Ar H+C3 H),
8.00 (s, 1H, C9 H), 8.35 (d, 1H, Ar H, J = 7.50 Hz); 13C NMR (DMSO-d6): δ 22.10
ꢁ
(C5 CH3), 24.40 (C-5ꢁ), 29.68 (C-6ꢁ), 111.25, 115.20, 118.10, 124.64, 125.80, 126.5,
126.9, 127.6, 128.0, 131.4, 135.5, 136.9, 148.4, 154.60 (15 sp2 carbon atoms), 156.40
(C-5), 167.80 (C-9ꢁ); Anal. calcd. for C20H13N9S (397.42): C, 58.38; H, 3.18; N, 30.64; S,
7.79. Found: C, 58.23; H, 3.33; N, 30.25; S, 7.55.

PYRAZOLOPYRIMIDINE AND PYRAZOLOTRIAZOLOPYRIMIDINE DERIVATIVES
79
Synthesis of 5a and 5b
A mixture of compound 2a10 or 2b (0.01 mol) and hydrazine hydrate (2 mL, 99%)
was refluxed in dry ethanol (20 mL) for 3 or 5 h. The reaction mixture was evaporated
under reduced pressure, and the residue was recrystallized from ethanol to give compounds
5a and 5b, respectively.
[1-(5,6-Dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-1H-pyra
zolo[3,4-d]pyrimidin-4-yl]hydrazine (5a). Compound 5a obtained here is identical
in all respects to that reported previously.18 Yield 78% (literature 86%), mp 205–207◦C
(literature mp 205–207◦C).
6-Methy-l-[1-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d] pyrimidin-11-yl)
-1H-pyrazolo[3,4-d]pyrimidin-4-yl]hydrazine (5b). Yield 84%, mp 214–216◦C; IR
νmax 3318, 3290, and 3150 cm−1 of the NH2/ NH groups; 1H NMR (DMSO-d6): δ 2.54 ppm
ꢁ
ꢁ
(s, 3H, C6 CH3), 2.80–3.00 (m, 4H, C5 CH2+C6 CH2), 4.10–4.30 (br.s, 2H, NH2, D2O
exchangeable), 6.50 (s, 1H, NH, D2O exchangeable), 7.20–7.40 (m, 4H, 3Ar H+C3 H),
7.50 (d, 1H, Ar H, J = 7.50 Hz), 8.60 (s, 1H, C9 H); 13C NMR (DMSO-d6): δ 21.00
ꢁ
(C6 CH3), 24.00 (C-5ꢁ), 29.40 (C-6ꢁ), 111.2–149.3 (15 sp2 carbon atoms), 152.7 (C-6),
157.90 (C-9ꢁ); EIMS, m/z (%): 400 (M+, 42), 364 (100); Anal. calcd. for C20H16N8S
(400.46): C, 59.98; H, 4.03; N, 27.98; S, 8.01. Found: C, 59.62; H, 4.41; N, 27.64; S, 8.21.
Synthesis of 6a and 6b
Compound 5a or 5b (0.01 mol) was refluxed in formic acid (20 mL, 85%) for 6 or 8h.
The reaction mixture was cooled and poured into water. The solid that formed was filtered
off, dried, and recrystallized from dioxane to afford compound 6a or 6b, respectively.
7-(5,6-Dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-7H-pyra
zolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine (6a). Yield 65%, mp 170–172◦C; IR
1
νmax absence of the NH2, NH groups; H NMR (DMSO-d6): δ 2.9–3.1 ppm (m, 4H,
ꢁ
ꢁ
ꢁ
C5 CH2+C6 CH2), 7.1–7.4 (m, 5H, 4Ar H+C9 H), 8.1 (s, 1H, C9 H), 8.7 (s,
1H, C2 H), 9.7 (s, 1H, C5 H); 13C NMR (DMSO-d6): δ 24.40 (C-5ꢁ), 29.68 (C-6ꢁ),
111.25–146.32 (15 sp2 carbon atoms), 151.10 (C-2), 156.40 (C-5), 167.00 (C-9ꢁ); Anal.
calcd. for C20H12N8S (396.43): C, 60.59; H, 3.05; N, 28.27; S, 8.09. Found: C, 60.77; H,
3.31; N, 28.01; S, 8.32.
5-Methyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-
7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine
(6b). Yield
58%,
mp
1
186–188◦C; IR νmax absence of the NH2, NH groups; H NMR (DMSO-d6): δ 2.4
ꢁ
ꢁ
ppm (s, 3H, C5 CH3), 2.9–3.0 (m, 4H, C5 CH2+C6 CH2), 7.2–7.3 (m, 4H, 3Ar H+
C9 H), 8.4 (s, 1H, C9 H), 9.1 (d, 1H, Ar H, J = 7 Hz), 9.2 (s, 1H, C2 H); 13C
ꢁ
NMR (DMSO-d6): δ 22.10 (C5 CH3), 24.40 (C-5ꢁ), 29.60 (C-6ꢁ), 111.25–146.32 (15 sp2
carbon atoms), 151.10 (C-2), 156.80 (C-5) and 167.00 (C-9ꢁ); Anal. calcd. for C21H14N8S
(410.46): C, 61.45; H, 3.44; N, 27.30; S, 7.81. Found: C, 61.24; H, 3.79; N, 27.01; S, 7.54.
General Procedure for the Synthesis of 7a and 7b
Compound 5a or 5b (0.01mol) was refluxed in triethyl orthoformate (20 mL) for 6
or 8 h. The reaction mixture was evaporated under reduced pressure, and the residue was
recrystallized from dioxane/methanol (1:1) to give compound 7a or 7b, respectively.

80
A. E. RASHAD ET AL.
7-(5,6-Dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-7H-
pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidine (7a). Yield 73%, mp 225–227◦C;
1
IR νmax absence of the NH2, NH groups; H NMR (DMSO-d6): δ 3.1–3.2 ppm (m, 4H,
ꢁ
ꢁ
C5 CH2+C6 CH2), 7.2–7.5 (m, 5H, 4Ar H+C9 H), 8.5 (s, 1H, C3 H), 9.3 (s,
1H, C9 H), 9.4 (s, 1H, C5 H); 13C NMR (DMSO-d6): δ 24.40 (C-5ꢁ), 29.68 (C-6ꢁ),
ꢁ
111.50–146.64 (15 sp2 carbon atoms), 153.00 (C-3), 160.10 (C-5), 168.90 (C-9ꢁ); Anal.
calcd. for C20H12N8S (396.43): C, 60.59; H, 3.05; N, 28.27; S, 8.09. Found: C, 60.32; H,
3.22; N, 28.11; S, 8.12.
5-Methyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-
7H-pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidine
(7b). Yield
70%,
mp
210–212◦C; IR νmax absence of the NH2, NH groups; 1H NMR (DMSO-d6): δ
ꢁ
ꢁ
2.80 (s, 3H, C5 CH3), 2.98–3.3 (m, 4H, C5 CH2+C6 CH2), 7.3–7.9 (m, 5H,
4Ar H+C9 H), 9.1(s, 1H, C9 H); 9.80 (s, 1H, C3 H); 13C NMR (DMSO-d6): δ 22.65
ꢁ
(C5 CH3), 24.40 (C-5ꢁ), 29.60 (C-6ꢁ), 112.14–146.90 (15 sp2 carbon atoms), 153.10
(C-3), 160.80 (C-5), 169.00 (C-9ꢁ); Anal. calcd. for C21H14N8S (410.46): C, 61.45; H,
3.44; N, 27.30; S, 7.81. Found: C, 61.34; H, 3.65; N, 27.21; S, 7.92.
General Procedure for the Synthesis of 8a and 8b
Compound 5a or 5b (0.01 mol) was refluxed in a mixture of acetic acid/acetic
anhydride (1:1, 20 mL) for 6 or 8 h. The formed precipitates were filtered off, dried, and
recrystallized from dioxane to give compound 8a or 8b, respectively.
2-Methyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-
7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine
(8a). Yield
67%,
mp
194–196◦C; IR νmax absence of the NH2, NH groups; 1H NMR (DMSO-d6): 2.4
ꢁ
ꢁ
ppm (s, 3H, C2 CH3), 2.8–3.0 (m, 4H, C5 CH2+C6 CH2), 7.0–7.4 (m, 5H,
4Ar H+C9 H), 8.1 (s, 1H, C9 H), 8.4 (s, 1H, C5 H); 13C NMR (DMSO-d6): δ 22.65
ꢁ
(C2 CH3), 24.40 (C-5ꢁ), 29.68 (C-6ꢁ), 111.50–146.64 (15 sp2 carbon atoms), 153.00
(C-2), 160.10 (C-5), 168.90 (C-9ꢁ); Anal. calcd. for C21H14N8S (410.46): C, 61.45; H,
3.44; N, 27.30; S, 7.81. Found: C, 61.56; H, 3.62; N, 27.01; S, 7.86.
2,5-Dimethyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-
yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine (8b). Yield 64%, mp
206–208◦C; IR νmax absence of the NH2, NH groups; H NMR (DMSO-d6): δ 2.4 ppm
1
ꢁ
ꢁ
(s, 3H, C2 CH3), 2.65 ppm (s, 3H, C5 CH3), 2.9 ppm (m, 4H, C5 CH2+C6 CH2),
7.2–7.3 (m, 5H, 4Ar H+C9 H), 8.6 (s, 1H, C9 H); 13C NMR (DMSO-d6): δ 22.10
ꢁ
(C2 CH3), 22.65 (C5 CH3), 24.40 (C-5ꢁ), 29.68 (C-6ꢁ), 111.50–146.64 (15 sp2 carbon
atoms), 153.00 (C-2), 160.10 (C-5), 168.90 (C-9ꢁ); Anal. calcd. for C22H16N8S (424.48):
C, 62.25; H, 3.80; N, 26.40; S, 7.55. Found: C, 61.96; H, 3.62; N, 26.01; S, 7.86.
General Procedure for the Synthesis of 9a and 9b
Compound 5a or 5b (0.01 mol) was stirred at room temperature in triethyl orthoacetate
(20 mL) for 5 h, the solid product that formed was collected by filtration, dried, and
recrystallized from dioxane to give compound 9a or 9b, respectively.
3-Methyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-yl)-
7H-pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidine
(9a). Yield
72%,
mp
212–214◦C; IR νmax absence of the NH2, NH groups; 1H NMR (DMSO-d6): 2.8
ꢁ
ꢁ
ppm (s, 3H, C3 CH3), 2.8–3.0 (m, 4H, C5 CH2+C6 CH2), 7.0–7.4 (m, 5H,

PYRAZOLOPYRIMIDINE AND PYRAZOLOTRIAZOLOPYRIMIDINE DERIVATIVES
81
4Ar H+C9 H), 8.1 (s,1H, C9 H), 8.9 (s, 1H, C5 H); 13C NMR (DMSO-d6): δ 23.15
(C3 CH3), 24.40 (C-5ꢁ), 29.68 (C-6ꢁ), 111.50–146.64 (15 sp2 carbon atoms), 152.60
(C-3), 161.18 (C-5), 168.90 (C-9ꢁ); Anal. calcd. for C21H14N8S (410.46): C, 61.45; H,
3.44; N, 27.30; S, 7.81. Found: C, 61.51; H, 3.56; N, 27.12; S, 7.64.
ꢁ
3,5-Dimethyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-
yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidine (9b). Yield 64%, mp
1
236–238◦C; IR νmax absence of the NH2, NH groups; H NMR (DMSO-d6): 2.9 ppm
ꢁ
ꢁ
(s, 3H, C3 CH3), 2.96–3.10 (m, 7H, C5 CH3, C5 CH2+C6 CH2), 7.0–7.4 (m, 5H,
4Ar H+C9 H), 8.1 (s, 1H, C9 H); 13C NMR (DMSO-d6): δ 23.18 (C3 CH3), 23.60
ꢁ
(C5 CH3), 24.40 (C-5ꢁ), 29.68 (C-6ꢁ), 111.50–146.64 (15 sp2 carbon atoms), 153.00
(C-3), 160.10 (C-5), 168.90 (C-9ꢁ); Anal. calcd. for C22H16N8S (424.48): C, 62.25; H,
3.80; N, 26.40; S, 7.55. Found: C, 61.96; H, 3.62; N, 26.01; S, 7.86.
Reaction of 5a or 5b with Triethyl Orthoacetate at Reflux
Compound 5a or 5b (0.01 mol) was refluxed in triethyl orthoacetate (20 mL) for 10
h, the solid product was formed collected by filtration on heat, dried, and purified on silica
gel column using petroleum ether 40–60◦C:ethyl acetate (7:3) as an eluent to give products
8a (25%) or 8b (22%) and 9a (64%) or 9b (58%), respectively.
Isomerization of 7a,b and 9a,b to 6a,b and 8a,b
Compounds 7a,b and 9a,b (0.01 mol) were refluxed in dry ethanol (20 mL) containing
a few drops of formic acid (for 7a,b) or acetic acid (for 9a,b) for 6 and 9 h, respectively.
The reaction mixtures were evaporated under reduced pressure, and the residues were
recrystallized from dioxane to give compounds 6a (90%), 6b (93%), 8a (89%), and 8b
(92%), respectively. Products obtained from these isomerizations are identical in all respects
(mp, TLC, physical, and spectral data) with those prepared previously.
General Procedure for the Synthesis of 10a and 10b
Compound 5a or 5b (0.01mol) and benzoyl chloride (2 mL) were refluxed in phos-
phorus oxychloride (20 mL) for 5 h. The reaction mixtures were cooled and poured into ice.
The solids that formed were filtered off, dried, and recrystallized from dioxane to afford
compounds 10a and 10b, respectively.
2-Phenyl-7-(5,6-dihydronaphtho[1ꢀ,2ꢀ:4,5]thieno[2,3-d]pyrimidin-11-
yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine (10a). Yield 65%, mp
235–237◦C; IR νmax absence of the NH2, NH groups; 1H NMR (DMSO-d6): 3.2–3.6 ppm
ꢁ
ꢁ
ꢁ
(m, 4H, C5 CH2+C6 CH2), 7.2–8.5 (m, 10H, 9Ar H+C9 H), 9.0 (s, 1H, C9 H), 9.5
(s, 1H, C5 H); 13C NMR (DMSO-d6): δ 24.40 (C-5ꢁ), 29.68 (C-6ꢁ), 117.50–156.64 (21
sp2 carbon atoms), 156.00 (C-2), 167.10 (C-5), 168.90 (C-9ꢁ); Anal. calcd. for C26H16N8S
(472.53): C, 66.09; H, 3.41; N, 23.71; S, 6.79. Found: C, 66.36; H, 3.51; N, 23.88; S, 6.74.
5-Methyl-2-phenyl-7-(5,6-dihydronaphtho[1’,2’:4,5]thieno[2,3-d
]pyrimidin-11-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine
(10b).
1
Yield 58%, mp 259–261◦C; IR νmax absence of the NH2, NH groups; H NMR (DMSO-
ꢁ
ꢁ
d6): 2.82 ppm (s, 3H, C5 CH3), 2.96–3.10 (m, 4H, C5 CH2+C6 CH2), 7.3–7.8 (m,
10H, 9Ar H+C9 H), 8.6 (s, 1H, C9 H); 13C NMR (DMSO-d6): δ 22.65 (C5 CH3),
ꢁ
24.40 (C-5ꢁ), 29.68 (C-6ꢁ), 117.50–155.40 (21 sp2 carbon atoms), 156.00 (C-2), 168.00

82
A. E. RASHAD ET AL.
(C-5), 169.10 (C-9ꢁ); Anal. calcd. for C27H18N8S (486.56): C, 66.65; H, 3.73; N, 23.03; S,
6.59. Found: C, 66.36; H, 3.51; N, 23.28; S, 6.74.
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