Chemistry of substituted quinolinones. Part 8. Synthesis and cyclization reactions of ethyl 5-amino-1-(1-methyl-2-oxoquinolin-4-YL)-3-methylsulfanylpyrazole-4-carboxylate

Article abstract of DOI:10.1080/10426500307880

The synthesis of the titled amino-ester 3 is described and its hydrolysis and chloroacetylation led to the acid 5 and acetamide 7, which were cyclized to the pyrazolopyridones 6 and 8, respectively. Condensation of 3 with 2,5-dimethoxytetrahydrofuran affo

Full text of DOI:10.1080/10426500307880

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Chemistry of Substituted Quinolinones. Part
8. Synthesis and Cyclization Reactions of Ethyl
5-Amino-1-(1-methyl-2-oxoquinolin-4-YL)-3-
methylsulfanylpyrazole-4-carboxylate
Mohamed Abass a
a Ain Shams University, Cairo, Egypt
Version of record first published: 27 Oct 2010.
To cite this article: Mohamed Abass (2003): Chemistry of Substituted Quinolinones. Part 8. Synthesis and Cyclization
Reactions of Ethyl 5-Amino-1-(1-methyl-2-oxoquinolin-4-YL)-3-methylsulfanylpyrazole-4-carboxylate, Phosphorus, Sulfur, and
Silicon and the Related Elements, 178:7, 1413-1432
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Phosphorus, Sulfur, and Silicon, 178:1413–1432, 2003
C
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print
DOI: 10.1080/10426500390212519
CHEMISTRY OF SUBSTITUTED QUINOLINONES.
PART 8. SYNTHESIS AND CYCLIZATION
REACTIONS OF ETHYL
5-AMINO-1-(1-METHYL-2-OXOQUINOLIN-4-YL)-3-
METHYLSULFANYLPYRAZOLE-4-CARBOXYLATE
Mohamed Abass
Ain Shams University, Cairo, Egypt
(Received October 14, 2002; accepted December 13, 2002)
The synthesis of the titled amino-ester 3 is described and its hydrolysis
and chloroacetylation led to the acid 5 and acetamide 7, which were
cyclized to the pyrazolopyridones 6 and 8, respectively. Condensation
of 3 with 2,5-dimethoxytetrahydrofuran afforded the pyrrolylpyrazole
9, which underwent cyclization by action of PPA to give pyrazolopy-
rrolizine 10. Treating 3 with thiophosgene gave the pyrazolyl isothio-
cyanate 11, which added aniline to yield the thiourea derivative 12, and
cyclized to give pyrazolopyrimidinethiones 13–15. Condensation of 3
with formamide furnished pyrazolopyrimidine 16, while with triethyl
orthoformate produced the ethoxymethyleneaminopyrazole 18, which
condensed with hydrazine to give the aminopyrazoloprimidine 19. Re-
action of 3 with Lawesson’s reagent resulted in the pyrazolothiaza-
phosphinine 21. Also the cyclization reaction of the compound 3 with
malononitrile and its mixtures with carbon disulfide, phenyl isothio-
cyanate, or benzaldehyde led to the formation of a variety of polyfunc-
tional substituted pyrazolopyrimidines 23 and 26, pyrazolothiazine 24
and pyrazolopyridine 28.
Keywords: Pyrazolopyridine; pyrazolopyrimidine; pyrazolopyrrolizine;
pyrazolothiazaphosphinine; pyrazolothiazine; pyrazolylquinolinone
Studies on the biochemical properties of the structures bearing the
pyrazole nucleus revealed their ability to uncouple oxidative phos-
phorylation, stabilize lysosomal membranes, inhibit biosynthesis of
various mucopolysaccharides, and perhaps most importantly, inhibit
The author is thankful to Dr. A. Khodairy for his useful and valuable facilities.
This work is dedicated to Prof. Dr. Ahmed M. Zahra.
Address correspondence to M. Abass, Department of Chemistry, Faculty of Education,
Ain Shams University, Roxy, Cairo 11711, Egypt. E-mail: mohamedabass@hotmail.com
1413

1414
M. Abass
prostaglandin biosynthesis, which accounts for their antiinflammatory
activities and analgesic effects.1 Also several substituted pyrazolo[3,4-
d]pyrimidines have shown diverse pharmacological activities, for ex-
ample Allopurinol acts as a potent Xanthine-Oxidase (XO) inhibitor,2
and has been used as an effective therapy of both the primary hyper-
uricemia of gout and that secondary to haematological disorders or as
antineoplastic therapy.3 Unfortunately, Allopurinol has some deleteri-
ous side effects so that efforts to find novel potent and safe XO-inhibitors
need to be continued.4–6 On the other hand, it is well known that
2(1H)quinolinone derivatives are associated with diverse pharmaceu-
tical activities. Many quinolinones showed antihyperplastic activity,7
anti-cancer effects,8 Alzheimer’s disease healing action,9 and also an-
tiulcer activity.10 Due to the above-mentioned medicinal importance, it
was planned to carry out a series of synthetic studies on novel hetero-
cyclic derivatives those combined both pyrazole and quinolinone in one
molecular frame.11
RESULTS AND DISCUSSION
Reactions of ketene dithioacetals with hydrazines are known to give the
corresponding multifunctional pyrazole derivatives.12 It is worthwhile
to mention that the heterocyclic products of these reactions not only are
interesting from the viewpoint of biological applications, but also they
have an important synthetic utility in the field of condensed heteropoly-
cyclic compounds. Thence, 4-hydarzino-1-methyl-2(1H)quinolinone
(1) was reacted with ethyl 2-cyano-3,3-bis(methylsulfanyl)acrylate
(2),13 in boiling DMF to afford ethyl 5-amino-1-(1-methyl-2-oxo-1,2-
dihydroquinolin-4-yl)-3-methylsulfanyl-1H-pyrazole-4-carboxylate (3).
1H NMR spectrum of the amino-ester 3 showed the presence of a set of
protons corresponding to an ethyl group as quartet and triplet peaks
(J = 7 Hz) at : 4.19 and 1.27 ppm respectively. No indication was found
for the formation of the other possible carbonitrile product 4. However,
this result is coincident with the reported results of the reaction of com-
pound 2 with hydrazines12,14 (Scheme 1).
Hydrolysis of the amino-ester 3 in an acid medium led to the forma-
tion of the corresponding amino-acid 5. De-esterification of compound
3 under either acidic or basic media was found to be not accompanied
by replacement of either methylsulfanyl or amino groups. Eventually,
acidic medium was selected for the higher yield. The preparation of the
pyrazolopyridone 6 was accomplished from cyclization of the amino-acid
5 by means of acetic anhydride and glacial acetic acid.15 Chloroacety-
lation of amino-ester 3 using chloroacetyl chloride furnished the

Synthesis and Cyclization Reactions of Ethyl
1415
SCHEME 1
corresponding chloroacetamide 7, in a good yield (86%). Compound 7
was subjected to a cyclization reaction using triethylamine, in boil-
ing DMSO, to give 5-chloro-4-hydroxy-3-methylsulfanylpyrazolo[3,4-
b]pyridine 8, which is the chloro derivative of compound 6. Obviously,
both compounds 6 and 8 sustain acidic character, as they are soluble
in dilute alkalis and precipitated upon the addition of acids. Also, both
compounds 6 and 8 gave deep violet coloration with ferric chloride neu-
tral solution due to the presence of phenolic hydroxyl group. Condensa-
tion reaction of the amino-ester 3 with 2,5-dimethoxytetrahydrofuran,
in glacial acetic acid, led to the formation of the expected structure,16
ethyl 5-pyrrolylpyrazole-4-carboxylate 9. The structure of the hetero-
tricyclic derivative 9 was inferred from its correct elemental analysis
1
as well as H NMR and IR spectra, which showed the disappearance
of the amino group at the same time as a pyrrolyl moiety specific pro-
tons come into sight (Table I). An interesting linear hetero-polycyclic
system bearing quinolinone was obtained, on carrying out catalyzed
intramolecular cyclization, by action of polyphosphoric acid (PPA) on
compound 9. The structure of the product was established on the basis
of its spectral data. 1H NMR spectrum clearly showed that ethyl ester
group disappeared and only seven aromatic protons were integrated
in the spectrum chart, : 7.83–7.25 ppm, beside the singlet peak at

1416
M. Abass
TABLE I IR and 1H NMR Spectral Data for the New Compounds
Compd.
no.
1
IR (KBr)/cm
1H NMR (DMSO-d6)/
3
3385, 3256 (NH), 1731
7.67–7.28 (m, 4H, Harom), 6.73 (s, 1H, C3-H),
(C Oester), 1677 (C Oquinolone), 6.58 (s, 2H, NH2), 4.19 (q, 2H, OCH2CH3),
1601 (C N), 1105 (C
O
C)
3.68 (s, 3H, NCH3), 2.32 (s, 3H, SCH3),
1.27 (t, 3H, OCH2CH3)
5
6
3387–2340 (H-bonded NH2,
CO2H), 1717 (C Oacid), 1657
(C Oquinolone), 1608 (C N)
3180–2720 (NH, OH), 1662
(C Opyridone), 1647
14.95 (b, 1H, OH), 7.75–7.20 (m, 4H, Harom),
6.74 (s, 1H, C3-H), 6.60 (s, 2H, NH2), 3.62
(s, 3H, NCH3), 2.30 (s, 3H, SCH3)
12.85 (b, 1H, OH), 11.03 (b, 1H, NH), 7.62–
7.26 (m, 4H, Harom), 6.90 (s, 1H, C5-
Hpyrazolopyrimidine), 6.65 (s, 1H, C3-Hquinolone),
3.58 (s, 3H, NCH3), 2.25 (s, 3H, SCH3)
9.40 (b, 1H, NHacetamide), 7.75–7.25 (m, 4H,
Harom), 6.86 (s, 1H, C3-H), 5.24 (s, 2H,
COCH2Cl), 4.15 (q, 2H, OCH2CH3), 3.55
(s, 3H, NCH3), 2.27 (s, 3H, SCH3), 1.22 (t,
3H, OCH2CH3)
(C Oquinolone), 1605 (C N)
7
3270 (NH), 1730 (C Oester),
1695 (C Oacetamide), 1671
(C Oquinolone), 1602 (C N),
1110 (C
O C)
8
9
3255–2800 (NH, OH), 1661
(C Opyridone), 1650
(C Oquinolone), 1612 (C N)
1708 (C Oester), 1663
13.58 (b, 1H, OH), 11.33 (b, 1H, NH), 7.75–
7.30 (m, 4H, Harom), 6.74 (s, 1H, C3-H),
3.61 (s, 3H, NCH3), 2.27 (s, 3H, SCH3)
7.75–6.80 (m, 8H, Harom), 6.05 (s, 1H, C3-H),
4.10 (q, 2H, OCH2CH3), 3.60 (s, 3H,
NCH3), 2.43 (s, 3H, SCH3), 1.08 (t, 3H,
OCH2CH3)
(C Oquinolone), 1586 (C N),
1491, 1456, 1115 (C
O C)
10
11
1682 (C Opyrrolone), 1648
(C Oquinolone), 1610 (C N),
1580, 1495, 1480, 1385
7.83–7.25 (m, 7H, Harom), 6.96 (s, 1H, C3-H),
3.66 (s, 3H, NCH3), 2.35 (s, 3H, SCH3)
2129 (N
C S), 1719 (C Oester), 7.76–7.23 (m, 4H, Harom), 6.70 (s, 1H, C3-H),
1634 (C Oquinolone), 1602
4.15 (q, 2H, OCH2CH3), 3.60 (s, 3H,
NCH3), 2.30 (s, 3H, SCH3), 1.25 (t, 3H,
OCH2CH3)
(C N), 1565, 1110 (C
3290–3160 (NH), 1712
O C)
12
13
14
15
8.48 (b, 1H, NHCS), 8.08–7.52 (m, 10H, Harom
(C Oester), 1651 (C Oquinolone), + PhNH), 6.56 (s, 1H, C3-H), 4.25 (q, 2H,
1605 (C N), 1539, 1318,
1245 (NHC S)
OCH2CH3), 3.80 (s, 3H, NCH3), 2.64 (s,
3H, SCH3), 1.32 (t, 3H, OCH2CH3)
11.24 (b, 1H, NH), 8.04–7.17 (m, 9H, Harom),
6.56 (s, 1H, C3-H), 3.68 (s, 3H, NCH3),
2.28 (s, 3H, SCH3)
3172 (NH), 1673
(C Opyrimidone), 1648
(C Oquinolone), 1585 (C N),
1542, 1328, 1225 (NHC S)
3200, 3132 (NH), 1680
(C Opyrimidone), 1643
(C Oquinolone), 1583 (C N),
1534, 1321, 1214 (NHC S)
3431, 3357 (NH2), 3146 (NH),
1657 (C Opyrimidone), 1641
(C Oquinolone), 1604 (C N),
1556, 1345, 1287 (NHC S)
12.45, 10.83 (b, 2H, 2 NHpyrimidone), 7.73–
7.35 (m, 4H, Harom), 6.76 (s, 1H, C3-H),
3.67 (s, 3H, NCH3), 2.30 (s, 3H, SCH3)
9.90 (b, 1H, NH), 7.72–7.21 (m, 4H, Harom),
6.74 (s, 1H, C3-H), 6.05 (s, 2H, NH2), 3.60
(s, 3H, NCH3), 2.40 (s, 3H, SCH3)
(Continued on next page)

Synthesis and Cyclization Reactions of Ethyl
1417
TABLE I IR and 1H NMR Spectral Data for the New Compounds (Continued)
Compd.
no.
1
IR (KBr)/cm
3170 (NH), 1673
1H NMR (DMSO-d6)/
16
11.25 (b, 1H, NHpyrimidone), 8.58 (s, 1H, C6-
Hpyrazolopyrimidine), 7.66–7.29
(m, 4H, Harom), 6.38 (s, 1H,
C3-Hquinolone), 3.65 (s, 3H, NCH3),
2.31 (s, 3H, SCH3)
(C Opyrimidone), 1644
(C Oquinolone), 1611 (C N),
1592, 1546, 1448
18
1742 (C Oester), 1676
(C Oquinolone), 1600 (C N),
1576, 1445, 1120 (C
8.55 (s, 1H, Hazomethine), 7.70–7.29 (m, 4H,
Harom), 6.73 (s, 1H, C3-H), 4.25–4.08 (m,
4H, 2 OCH2CH3), 3.68 (s, 3H, NCH3),
2.32 (s, 3H, SCH3), 1.30–1.15 (m, 6H, 2
OCH2CH3)
O C)
19
21
23
24
25
3417, 3350 (NH2), 1665
(C Opyrimidone), 1635
(C Oquinolone), 1585 (C N),
1448, 1395
8.64 (s, 1H, C6-Hpyrazolopyrimidine), 7.85–6.89
(m, 6H, Harom + NH2), 6.40 (s, 1H, C3-
Hquinolone), 3.68 (s, 3H, NCH3), 2.72 (s, 3H,
SCH3)
9.15 (b, 1H, NH), 7.88–7.10 (m, 8H, Harom),
6.64 (s, 1H, C3-H), 4.05 (s, 3H, OCH3),
3.52 (s, 3H, NCH3), 2.27 (s, 3H, SCH3)
3240 (NH), 1676
(C Ophosphathiazinone), 1635
(C Oquinolone), 1600 (C N),
1506, 1252, 1163, 1044 (P S)
3227 (NH), 2203 (C N), 1667
(C Opyrimidone), 1631
(C Oquinolone), 1617 (C N),
1590, 1543, 1452
3200 (NH), 2206 (C N), 1680
(C Othiazinone), 1640
11.45 (b, 1H, NH), 7.60–7.12 (m, 4H, Harom),
6.16 (s, 1H, C3-H), 3.70 (s, 3H, NCH3),
3.23 (s, 2H, CH2CN), 2.24 (s, 3H, SCH3)
10.50 (b, 1H, NH), 7.76–7.23 (m, 4H, Harom),
6.72 (s, 1H, C3-H), 3.65 (s, 3H, NCH3),
2.30 (s, 3H, SCH3)
(C Oquinolone), 1589 (C N),
1571, 1421, 1347, 1051
3242, 3174 (NH), 2210 (C N), 9.42 (b, 1H, NHamidine), 8.93 (b, 1H,
1720 (C Oester), 1661
(C Oquinolone), 1600 (C N),
PhNHamidine), 7.96–7.05 (m, 9H, Harom),
6.06 (s, 1H, C3-H), 4.28 (q, 2H, OCH2CH3),
3.68 (s, 3H, NCH3), 2.40 (s, 3H, SCH3),
1.18 (t, 3H, OCH2CH3)
1562, 1483, 1100 (C
O C)
26
28
3185 (NH), 2218 (C N), 1668
(C Opyrimidone), 1649
(C Oquinolone), 1575 (C N),
1508, 1482
11.27 (b, 1H, NH), 7.98–7.20 (m, 9H, Harom),
6.62 (s, 1H, C3-H), 3.74 (s, 3H, NCH3),
2.25 (s, 3H, SCH3)
32580 (NH), 2200 (C N), 1660 9.92 (b, 1H, NH), 7.72–7.03 (m, 9H, Harom),
(C Opyridone), 1642
(C Oquinolone), 1590 (C N),
1541, 1483, 1445
6.05 (s, 1H, C3-H), 3.60 (s, 3H, NCH3),
2.40 (s, 3H, SCH3)
: 6.96 ppm due to the proton at position-3 of quinolinone and also
two singlets at : 3.66 and 2.35 ppm due to both N-methyl and S-
methyl protons respectively. Building on the above cited data and other
analyses, the structure of this product was deduced as 1-quinolinyl-3-
methylsulfanylpyrazolo[4,3-b]pyrrolizin-4-one 10 (Scheme 2).

1418
M. Abass
SCHEME 2
Isothiocyanates are distinguished as very useful intermediates for
the preparation of thioureas, thiosemicarbazides, thioxopyrimidines,
etc. Hence our attention was attracted to transform the amino group
in the compound 3 to an isothiocyanato one. To reach this purpose,
thiophosgene17 was used to obtain the targeted isothiocyanate 11 in a
moderate yield. IR spectrum of compound 11 reflected the existence of
the isothiocyanato group ( : 2129 cm 1). Addition of aniline to com-
pound 11, in the molar ratio (1:1), furnished the 1,3-disubstituted
thiourea 12 which underwent smooth base-catalyzed intramolecular
cyclo-condensation to give 5-phenyl-6-thioxopyrazolo[3,4-d]pyrimidine
13. As another route to obtain compound 13, the amino-ester 3

Synthesis and Cyclization Reactions of Ethyl
1419
itself was cyclized via an addition-condensation reaction with phenyl
isothiocyanate, in the presence of ethanolic potassium hydroxide. It is
thought that the formation of the pyrimidine 13 intermediately passes
by the formation of the thiourea 12. Similar behavior was observed
again when compound 3 was treated with benzoyl isothiocyanate un-
der the same conditions, giving the thioxopyrazolo[3,4-d]pyrimidinone
14. The spectral data of the product showed that debenzoylation took
place during the course of the cyclization reaction. However some re-
ports in the literature recorded similar deacylation during the cy-
clization of acyl isothiocyanate and/or isoselenocyanate.18,19 5-Amino-3-
methylsulfanyl-6-thioxopyrazolo[3,4-d]pyrimidinone 15 was obtained,
in a relatively moderate yield (48%), via a facile one-pot preparation
starting with amino-ester 3. Thus, compound 3 was reacted with car-
bon disulfide and potassium hydroxide, then the anion that formed was
S-methylated by means of methyl iodide and subsequently the process
was completed by in situ treatment with hydrazine hydrate. On the
other hand, compound 15 was obtained through an easier method but
in a lesser overall yield. This was achieved by cyclization reaction of the
isothiocyanate 11 with hydrazine hydrate in boiling DMF (Scheme 3).
Thermal condensation of the amino-ester 3 with formamide led to
smooth formation of pyrazolo[3,4-d]pyrimidinone 16. Compound 16 is
another derivative of the pyrazolopyrimidine series, which is struc-
turally related to Allopurinol.2 Condensation of compound 3 with tri-
ethyl orthoformate was carried out, in boiling acetic anhydride, to af-
ford the ethoxymethyleneamino-ester 18. Although, the position-3 of
2-quinolinone has good susceptibility to be attacked by electrophiles20
and it was expected in the latter reaction to undergo condensation
with ethoxymethyleneamino group, affording pyrazolopyrimidoquino-
line 17, under different reaction conditions, the obtained product was
only the compound 18. This may back to the geometry of the compound
that is mainly expected to possess trans-form. Herein, no more than
one product was isolated, which has a sharp melting point, checked
with TLC and its spectral data pointed to a single and pure product.
This was strongly supported by the cyclo-condensation of compound 18
with hydrazine hydrate in boiling dimethylformamide,21 the reaction
that led to the formation of 5-amino-3-methylsulfanylpyrazolo[3,4-
d]pyrimidin-4-one 19. The structural formula of compound 19 was
established upon spectral and analytical data. The reaction of the
amino-ester 3 with 2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphe-
tane-2,4-disulfide, Lawesson’s reagent, was carried out, in dry p-xylene,
giving the novel pyrazolo[3,4-d][1,3,2]thiazaphosphinine 21. The spec-
tral study of the product showed the disappearance of both the amino
and carboxylate functions. It is worthwhile to note that Lawesson’s

1420
M. Abass
SCHEME 3
reagent did not lead to the quinolinethione 20 as all features of the
product did not point to such replacement. In addition, such cycliza-
tion reactions involving Lawesson’s reagent were reported, leading to
various phospha-heterocycles22,23 (Scheme 4).
The chemical behavior of the amino-ester 3 toward malononitrile
was investigated. Thus, treating compound 3 with malononitrile, in
the presence of sodium ethoxide, was carried out at the purpose of pro-
duction of the pyrazolopyridine 22. The expected product 22, which
should include amino and cyano groups, was not afforded, while a
different compound was obtained and characterized as (pyrazolo[3,4-
d]pyrimidinyl)acetonitrile 23. Clearly, the inseparable intermediate;
N-pyrazolylcyanoacetamidine was formed at first and hence the amino

Synthesis and Cyclization Reactions of Ethyl
1421
SCHEME 4
group underwent an intramolecular cyclo-condensation reaction with
its neighboring carboxylate group. When the amino-ester 3 was reacted
with malononitrile and carbon disulfide under solid-liquid phase trans-
fer catalysis (PTC) conditions,24 (K2CO3/[Bu4N]Br/dioxane), we have
obtained the (pyrazolothiazinylidene)-malononitrile 24. The production
of the latter thiazine derivative might pass through the formation of a
dicyanoketene-N,S-acetal intermediate (not separated), which in a fol-
lowing step underwent catalyzed cyclo-condensation between sulfanyl
and carboxylate groups (Scheme 5).

1422
M. Abass
SCHEME 5
Utilizing the same PTC conditions for the reaction of malononitrile
and carbon disulfide with the starting compound, malononitrile and
phenyl isothiocyanate was reacted with compound 3. As a very good
support for the above hypothesis about formation of an intermediate
ketene-acetal in such reactions, the dicyanoketene-N,N-acetal 25 was
separated as the product of the latter reaction. The ketene-acetal 25 was
well characterized through its analytical and spectral data, which con-
firmed the existence of both (NH) and ethyl carboxylate groups. More-
over, the compound 25 underwent smooth thermal cyclization to give
the (pyrazolo[3,4-d]pyrimidinylidene)malononitrile 26. 1H NMR of the
compound 26 gave us useful information about the nature of protons
in this molecule, thus only one proton has the acidic character and ap-
peared at : 11.27 ppm due to (NH) of pyrimidinone, besides the other
S-methyl, N-methyl, and aromatic protons chemical shifts. The reac-
tion of compound 3 with malononitrile in the presence of a third partner

Synthesis and Cyclization Reactions of Ethyl
1423
reagent was once more performed with benzaldehyde under the same
PTC conditions previously described. The reaction is expected to pro-
ceed via addition of the amino group in the amino-ester compound,
to the so-formed in situ; benzylidenemalononitrile, and subsequently
an intramolecular nucleophilic cyclo-condensation, took place between
the dicyano-carbanion and the carboxylate group. The compound 27
is thought to be an intermediate in this transformation, even though
it was not isolated. The spectral data along with analytical results are
well matched with the anticipated structure of the product pyrazolo[3,4-
b]pyridine-5-carbonitrile 28. This indicated that during the course of
cyclization reaction one molecule of hydrogen cyanide should be ex-
pelled. As an evidence for the proposed structure for compound 28, we
carried out an independent synthesis of this compound by action of
benzoylacetonitrile on the same starting material 3, in the presence of
sodium ethoxide as the catalyst (Scheme 6). All of the newly obtained
compounds were characterized using analytical data (Table II) as well
as IR and 1H NMR spectroscopy (Table I).
SCHEME 6

1424
M. Abass
TABLE II Physical and Analytical Data for the New Compounds
Analysis calcd./found (%)
Compd.
no.
m.p.
( C)
Yield
(%)
Mol. formula
(mol. wt.)
C
H
N
3
5
216–217
280–281
>300
85
63
C17H18N4O3S
(358.42)
C15H14N4O3S
(330.37)
56.97
56.80
54.54
54.40
57.62
57.40
52.47
52.30
52.51
52.40
61.75
61.50
62.97
62.70
53.99
54.20
58.40
58.30
59.04
59.10
51.74
51.60
49.73
49.80
56.63
56.60
57.96
57.80
54.23
54.10
51.35
51.10
57.13
57.00
54.27
54.30
61.70
61.50
62.62
62.60
65.59
65.40
5.06
4.80
4.27
4.40
3.98
4.10
4.40
4.60
3.37
3.20
4.94
5.10
3.89
3.80
4.03
4.10
4.70
4.60
3.83
3.90
3.53
3.30
3.65
3.50
3.86
3.70
5.35
5.30
3.98
3.80
3.72
3.60
3.73
3.50
2.88
2.80
4.41
4.40
3.57
3.50
3.90
3.80
15.63
15.30
16.96
16.90
15.81
15.70
12.88
12.70
14.41
14.20
13.72
13.60
15.46
15.30
13.99
13.70
14.19
14.00
15.65
15.40
18.85
18.70
21.75
21.70
20.64
20.50
13.52
13.30
23.71
23.60
10.89
10.80
22.21
22.00
19.99
19.90
18.65
18.50
20.45
20.30
15.93
15.80
6
56
C
17H14N4O3S
(354.39)
7
181–182
287–288
198–199
172–174
112–114(d)
160–162
265–266
198–200
180–182
167–169
161–162
210–212
203–205
>300
86
C19H19CIN4O4S
(434.90)
C17H13CIN4O3S
(388.84)
8
74
9
79
C21H20N4O3S
(408.48)
C19H14N4O2S
(362.41)
C18H16N4O3S2
(400.48)
10
11
12
13
14
15
16
18
19
21
23
24
25
26
28
47
52
84
C24H23N5O3S2
(493.61)
C22H17N5O2S2
(447.54)
C16H13N5O2S2
(371.44)
C16H14N6O2S2
(386.46)
75a, 81b
65
48a, 66b
56
C16H13N5O2S
(339.38)
C20H22N4O4S
(414.49)
67
78
C
16H14N6O2S
(354.39)
56
C22H19N4O3PS3
(514.59)
77
C18H14N6O2S
(378.42)
C19H12N6O2S2
(420.47)
163–165
178–180
164–166
184–186
58
55
C27H23N7O3S
(525.59)
75
C
25H17N7O2S
(479.52)
63a, 68b
C24H17N5O2S
(439.50)
a,bYield of methods A and B respectively.

Synthesis and Cyclization Reactions of Ethyl
1425
EXPERIMENTAL
Melting points are uncorrected and were determined on a digital
Gallen-kamp MFB-595. IR spectra were taken on Perkin-Elmer FT-IR
1650 or Nicolet FT-IR 710 spectrophtometers ( , cm 1), using samples
1
in KBr disks. H NMR spectra were recorded on Varian Gemini 200
(200 MHz) or Varian EM-360L (60 MHz) spectrometers ( , ppm), using
DMSO-d6 as the solvent and TMS as an internal reference. Elemental
microanalyses were performed on a Perkin-Elmer CHN-2400 analyzer,
at the Cairo University Microanalytical Centre. The compounds 111 and
213 were prepared by the reported methods.
Ethyl 5-Amino-1-(1-methyl-2-oxo-1,2-dihydroquinolin-4-
yl)-3-methylsulfanyl-1H-pyrazole-4-carboxylate (3)
A mixture of equimolar amounts (0.1 mmol) of both hydrazinoquinolone
1 (18.92 g) and compound 2 (21.73 g) in DMF (250 ml) was heated under
reflux for 1 h. The reaction mixture was left to cool and poured onto
crushed ice; the precipitate so formed was filtered off and crystallized
from ethanol to give the amino-ester 3 (30.5 g).
5-Amino-1-(1-methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-1H-pyrazole-4-carboxylic acid (5)
Compound 3 (1 g, 2.8 mmol) was dissolved in hydrochloric acid (50 ml,
0.5 M) and then heated under reflux on a boiling water bath for 4 h.
The reaction mixture was cooled to room temperature and neutralized
using aqueous sodium bicarbonate solution (10%). The white precipi-
tate so obtained was filtered off and crystallized from ethanol to yield
the amino-acid 5 (0.58 g).
4-(4-Hydroxy-3-methylsulfanyl-6-oxo-6,7-dihydro-1 H-
pyrazolo[3,4-b]pyridin-1-yl)-1-methylquinolin-2(1 H)-one
(6)
A solution of the amino-acid 5 (0.5 g, 1.5 mmol) in glacial acetic acid
(5 ml) and acetic anhydride (5 ml) was heated under reflux for 4 h. Af-
terward, the excess solvent was evaporated in vacuum, then the residue
was treated with sodium hydroxide solution (25 ml, 15%), and left to
stand over night. The alkaline solution was filtered off and the clear fil-
trate was acidified using hydrochloric acid. The so-obtained precipitate
was filtered off, washed several times with water, and crystallized from
acetic acid to give the pyarzolopyridone 6 (0.3 g).

1426
M. Abass
Ethyl 5-(Acetylamino)-1-(1-methyl-2-oxo-1,2-
dihydroquinolin-4-yl)-3-methylsulfanyl-1 H-pyrazole-4-
carboxylate (7)
To a solution of compound 3 (0.9 g, 2.5 mmol) in dry dioxane (20 ml)
and few drops of pyridine, chloroacetyl chloride (0.2 ml, 2.5 mmol) in
dioxane (5 ml) were dropwise added with continuous stirring at room
temperature for 20 min. After that, the reaction mixture was heated
on a boiling water bath for additional 20 min, then left to stand for 1 h
and poured onto crushed ice. The precipitate that formed was collected
by filtration, washed with cold water, and crystallized from acetone to
give the acetamide 7 (0.94 g).
4-(5-Chloro-4-hydroxy-3-methylsulfanyl-6-oxo-6,7-
dihydro-1H-pyrazolo[3,4-b]pyridin-1-yl)-1-
methylquinolin-2(1H)-one (8)
A solution of the acetamide 7 (0.65 g, 1.5 mmol) in DMSO (10 ml),
containing triethylamine (0.2 ml) was heated under reflux for 3 h. The
reaction mixture was left to cool and poured onto crushed ice-cold water
(20 ml). The precipitate so obtained was filtered off and crystallized from
DMF to give the pyrazolopyridone 8 (0.43 g).
Ethyl 1-(1-Methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-5-(pyrrol-1-yl)-1 H-pyrazole-4-carboxylate
(9)
A mixture of the amino-ester 3 (1.79 g, 5 mmol) and 2,5-
dimethoxytetrahydrofuran (0.7 ml, 5.3 mmol), in glacial acetic acid
(20 ml) was heated under reflux for 1 h. Then the excess solvent was
evaporated to one-half of its initial volume and left to cool in an ice-bath.
The crystalline material so obtained was filtered off and recrystallized
from acetic acid to give the pyrrolyl-pyrazole 9 (1.62 g).
1-(1-Methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-1H-pyrazolo[3,4-b]pyrrolizin-4-one (10)
To a freshly prepared polyphosphoric acid (1.5 g), in a conical flask fit-
ted with a short air condenser, the compound 9 (1 g, 2.5 mmol) was
portion-wise added with continuous stirring for 20 min, at a tempera-
ture that did not exceed 160 C. After the addition was completed, the
temperature was raised gradually to 190–200 C for 1 h. Then the re-
action mixture was left to cool and triturated with saturated sodium
acetate aqueous solution. The solid deposits were collected by suction,

Synthesis and Cyclization Reactions of Ethyl
1427
washed several times with water, and crystallized from DMF to give
the pyrrolizinone 10 (0.42 g).
Ethyl 5-Isothiocyanato-1-(1-methyl-2-oxo-1,2-
dihydroquinolin-4-yl)-3-methylsulfanyl-1 H-pyrazole-4-
carboxylate (11)
A solution of the amino-ester 3 (1.79 g, 5 mmol) in chloroform (50 ml)
was added to a mixture of thiophosgene (0.4 ml, 5.3 mmol), sodium bi-
carbonate (0.6 g, 7.14 mmol), water (5 ml), and chloroform (50 ml) with
continuous stirring at 20 C over a period of 30 min. The mixture then
was stirred for additional 2 h at 30–35 C. The organic layer was sepa-
rated, washed twice with water, dried over anhydrous sodium sulfate,
and evaporated under reduced pressure. The solid residue collected and
crystallized from petroleum ether (60–80 C) to give the isothiocyanate
11 (1.04 g).
Ethyl 1-(1-Methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-5-(3-phenylthioureido)-1 H-pyrazole-4-
carboxylate (12)
A solution of the isothiocyanate 11 (0.5 g, 1.25 mmol) in THF (10 ml)
was added dropwise with continuous stirring to a solution of aniline
(0.12 ml, 1.3 mmol) in THF (10 ml). The suspension so obtained was
stirred at room temperature for 1 h, and then the solid deposit so formed
was filtered off, washed with diethyl ether (25 ml), and crystallized from
ethanol to give the thiourea 12 (0.52 g).
1-Methyl-4-(3-methylsulfanyl-4-oxo-5-phenyl-6-thioxo-
4,5,6,7-tetrahydro-1H-pyrazolo[3,4-d]pyrimidin-1-
yl)quinolin-2(1H)-one (13)
A: To a solution of potassium hydroxide (0.1 g, 1.8 mmol) in ethanol
(10 ml, 95%), the thiourea derivative 12 (0.5 g, 1 mmol) was added and
the mixture was heated under reflux for 1 h. The suspension that formed
was filtered while hot and the solid residue was dissolved in hot water
(5 ml) and filtered off. The clear filtrate was acidified using hydrochloric
acid to give a precipitate, which was collected by filtration and crystal-
lized from DMF to furnish the pyrazolopyrimidine 13 (0.34 g).
B: A mixture of the amino-ester 3 (1.07 g, 3 mmol), phenyl isothio-
cyanate (0.4 ml, 3.3 mmol), and potassium hydroxide (0.18 g, 3.2 mmol)
in ethanol (25 ml) was heated under reflux for 2 h. Then the reaction
mixture was filtered while hot and the solid residue was dissolved in

1428
M. Abass
hot water (5 ml) and filtered off. The clear filtrate was acidified using
hydrochloric acid to give a precipitate, which was collected by filtra-
tion and crystallized from DMF to furnish the pyrazolopyrimidine 13
(1.08 g) (m.p., m.m.p. and spectra).
1-Methyl-4-(3-methylsulfanyl-4-oxo-6-thioxo-4,5,6,7-
tetrahydro-1H-pyrazolo[3,4-d]pyrimidin-1-yl)quinolin-
2(1H)-one (14)
Using the same method (B) for compound 13, a mixture of the amino-
ester 3 (1.07 g, 3 mmol), benzoyl isothiocyanate (0.5 ml, 3.6 mmol), and
potassium hydroxide (0.18 g, 3.2 mmol) in ethanol (25 ml) was reacted
to give a precipitate, which was crystallized from DMF leading to the
pyrazolopyrimidine 14 (0.72 g).
4-(5-Amino-3-methylsulfanyl-4-oxo-6-thioxo-4,5,6,7-
tetrahydro-1H-pyrazolo[3,4-d]pyrimidin-1-yl)-1-
methylquinolin-2(1H)-one (15)
A: To a cooled (0 C) stirred solution of the amino-ester 3 (1.79 g,
5 mmol) in DMSO (20 ml) and potassium hydroxide aqueous solution
(3 ml, 3 M), carbon disulfide (0.3 g, 5 mmol) was dropwise added during a
period of 20 min. Then the mixture was stirred at room temperature for
an additional 1 h. Methyl iodide (0.32 ml, 5.1 mmol) in dioxane (10 ml)
was dropwise added to the above mixture with continuous stirring dur-
ing a period of 30 min. Afterward, the mixture was dropwise treated
with hydrazine hydrate (0.25 ml, 5 mmol) and heated under reflux on
a boiling water-bath for 2 h. The reaction mixture was left to cool and
diluted with cold water to give a precipitate, which was collected by fil-
tration and crystallized from dioxane to furnish the pyrazolopyrimidine
15 (0.93 g).
B: To a solution of the isothiocyanate 11 (0.8 g, 2 mmol), in DMF
(5 ml), hydrazine hydrate (0.1 ml, 2 mmol) was added and the mix-
ture was heated under reflux 3 h. On cooling and addition of cold water
(10 ml) a precipitate was obtained, which was filtered off and crystal-
lized from dioxane to afford the pyrazolopyrimidine 15 (0.51 g) (m.p.,
m.m.p. and spectra).
1-Methyl-4-(3-methylsulfanyl-4-oxo-4,5-dihydro-1 H-
pyrazolo[3,4-d]pyrimidin-1-yl)quinolin-2(1H)-one (16)
A mixture of the amino-ester 3 (0.72 g, 2 mmol) and formamide (5 ml)
was heated in an oil bath at 180 C for 2 h. After that the mixture was

Synthesis and Cyclization Reactions of Ethyl
1429
diluted with water (5 ml) and left to stand in an ice-bath for 2 h to give
crystalline material, which was recrystallized from ethanol affording
the pyrazolopyrimidine 16 (0.38 g).
Ethyl 5-(Ethoxymethyleneamino)-1-(1-methyl-2-oxo-1,2-
dihydroquinolin-4-yl)-3-methylsulfanyl-1 H-pyrazole-4-
carboxylate (18)
A mixture of the amino-ester 3 (1.79 g, 5 mmol), triethyl orthoformate
(0.85 ml, 5 mmol), and acetic anhydride (15 ml) was heated under reflux
for 5 h. Then the excess solvent was removed under reduced pressure
and the oily material so obtained was triturated with cold water (15 ml)
to give solid deposits, which were filtered and crystallized from ethanol
to give compound 18 (1.39 g).
4-(5-Amino-3-methylsulfanyl-4-oxo-4,5-dihydro-1 H-
pyrazolo[3,4-d]pyrimidin-1-yl)-1-methylquinolin-2(1 H)-
one (19)
To a solution of the compound 18 (1 g, 2.4 mmol), in DMF (10 ml),
hydrazine hydrate (0.15 ml, 3 mmol) in DMF (5 ml) was dropwise added
and the mixture was heated under reflux for 2 h. On cooling and addition
of cold water (10 ml) a solid precipitate was afforded. The precipitate
was filtered and crystallized from ethanol to give the aminopyrimidone
19 (0.67 g).
1 Methyl-4-[2-(4-methoxyphenyl)-5-methylsulfanyl-4-
oxo-2-thioxo-2H,7H-1,4-dihydropyrazolo[3,4-
d][1,3,2]thiazaphosphinin-7-yl]quinolin-2(1 H)-one (21)
A mixture of the amino-ester 3 (1.79 g, 5 mmol) and Lawesson’s reagent
(2.1 g, 5 mmol), in dry p-xylene (20 ml) was heated under reflux for
6 h. Afterward, the solvent was removed under reduced pressure and
the obtained residue was triturated with cold methanol (20 ml). The
precipitate was collected by suction and crystallized from dioxane to
afford the compound 21 (1.44 g).
[1-(1-Methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-4-oxo-4,5-dihydro-1 H-pyrazolo[3,4-
d]pyrimidin-6-yl]acetonitrile (23)
To a mixture of the amino-ester 3 (1.07 g, 3 mmol) and malononitrile
(0.2 g, 3 mmol) in absolute ethanol (10 ml), sodium ethoxide (0.3 g,

1430
M. Abass
4.3 mmol) in absolute ethanol (10 ml) was dropwise added with contin-
uous stirring over a period of 30 min. Then the reaction mixture was
heated under reflux for 2 h and then poured onto crushed ice and fil-
tered off. The clear filtrate was neutralized using dilute acetic acid to
give a yellow precipitate, which was collected by filtration and crystal-
lized from ethanol to afford the acetonitrile 23 (0.87 g).
[1-(1-Methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-4-oxo-4,7-dihydro-1 H-pyrazolo[3,4-
d][1,3]thiazin-6-ylidene]malononitrile (24)
To a mixture of malononitrile (0.2 g, 3 mmol), carbon disulfide (0.2 ml,
3.3 mmol) and anhydrous potassium carbonate (0.42 g, 3 mmol) in diox-
ane (20 ml), tetrabutylammonium bromide (0.1 g, 0.3 mmol) was added
and the mixture was stirred at 60 C for 30 min. The amino-ester 3
(1.07 g, 3 mmol), in dioxane (25 ml), was dropwise added to the above
mixture with continuous stirring over a period of 30 min. After that, the
stirring was continued for additional 3 h and the reaction mixture fil-
tered off. The organic solvent was removed in reduced pressure to give
a solid residue, which was washed with water and crystallized from
dioxane to afford the pyrazolothiazine 24 (0.73 g).
Ethyl 5-[1-Anilino-2,2-dicyano(vinylamino)]-1-(1-methyl-
2-oxo-1,2-dihydroquinolin-4-yl)-3-methylsulfanyl-1 H-
pyrazole-4-carboxylate (25)
Following the above method described for compound 24, a mixture of
malononitrile (0.2 g, 3 mmol), phenyl isothiocyanate (0.4 ml, 3.3 mmol),
anhydrous potassium carbonate (0.42 g, 3 mmol), tetrabutylammonium
bromide (0.1 g, 0.3 mmol), and the amino-ester 3 (1.07 g, 3 mmol) in
dioxane (45 ml) was reacted to yield a yellow precipitate that was crys-
tallized from dioxane to give the compound 25 (0.86 g).
[1-(1-Methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-4-oxo-5-phenyl-1,4,5,7-tetrahydro-6 H-
pyrazolo[3,4-d]pyrimidin-6-ylidene]malononitrile (26)
The compound 25 (0.53 g, 1 mmol) was dissolved in ethylene glycol
(10 ml) and heated under short air condenser at 110–120 C for 30 min.
After that the temperature was raised gradually to 170–190 C for an
additional 30 min. The mixture was left to cool and the white precipitate
so formed on addition of cold water (20 ml) was filtered off and crystal-
lized from dioxane to furnish the pyrazolopyrimidine 26 (0.36 g).

Synthesis and Cyclization Reactions of Ethyl
1431
1-(1-Methyl-2-oxo-1,2-dihydroquinolin-4-yl)-3-
methylsulfanyl-4-oxo-6-phenyl-4,7-tetrahydro-1 H-
pyrazolo[3,4-b]pyridine-5-carbonitrile (28)
A: Equimolar amounts (3 mmol) of malononitrile (0.2 g), benzaldehyde
(0.3 ml), and potassium carbonate (0.42 g) in dioxane (20 ml) were
treated with tetrabutylammonium bromide (0.1 g, 0.3 mmol). The mix-
ture was stirred at 60 C for 1 h, and then the aminoester 3 (1.07 g,
3 mmol) in dioxane (25 ml) was added. The reaction mixture was heated
under reflux on boiling water-bath for 2 h and then filtered while hot.
The filtrate was concentrated to half of its initial volume and left over
night to give a precipitate, which was collected by filtration and crys-
tallized from DMF to furnish the pyrazolopyridine 28 (0.83 g).
B: To a mixture of the amino-ester 3 (0.72 g, 2 mmol) and benzoy-
lacetonitrile (0.3 g, 2 mmol) in ethanol (15 ml), sodium ethoxide (0.27 g,
4 mmol) in ethanol (10 ml) was added and the reaction mixture was
heated under reflux on a boiling water bath for 6 h. Then the reaction
mixture was left to cool, diluted with water (50 ml), and filtered off. The
clear filtrate was acidified using hydrochloric acid to give a precipitate,
which was collected by filtration and crystallized from DMF to furnish
the pyrazolopyridine 28 (0.6 g) (m.p., m.m.p. and spectra).
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