Synthesis and reactions of some new thiazolylpyrazole derivatives and related compounds

Article abstract of DOI:10.1080/10426500801963608

Thiazolylpyrazoles 2-7 were prepared from the reaction of 2-hydrazino-4-phenylthiazole (1) with yielidenenitriles; S,S- or N, S-acetals or ethoxymethylenemalononitrile. 5-Amino-1-(4-phenyl-thiazol-2-yl)-1H-pyrazole-4- carbonitrile (7) reacted with phenyl

Full text of DOI:10.1080/10426500801963608

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Phosphorus, Sulfur, and Silicon
and the Related Elements
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Synthesis and Reactions of
Some New Thiazolylpyrazole
Derivatives and Related
Compounds
Amer Anwar Amer a
a Department of Chemistry, Faculty of Science ,
Sohag University , Sohag, Egypt
Published online: 12 Aug 2008.
To cite this article: Amer Anwar Amer (2008) Synthesis and Reactions of Some New
Thiazolylpyrazole Derivatives and Related Compounds, Phosphorus, Sulfur, and Silicon
and the Related Elements, 183:9, 2330-2343, DOI: 10.1080/10426500801963608
To link to this article: http://dx.doi.org/10.1080/10426500801963608
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Phosphorus, Sulfur, and Silicon, 183:2330–2343, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500801963608
Synthesis and Reactions of Some New Thiazolylpyrazole
Derivatives and Related Compounds
Amer Anwar Amer
Department of Chemistry, Faculty of Science, Sohag University,
Sohag, Egypt
Thiazolylpyrazoles 2-7 were prepared from the reaction of 2-hydrazino-4-
phenylthiazole (1) with yielidenenitriles; S,S- or N, S-acetals or ethoxymethylene-
malononitrile. 5-Amino-1-(4-phenyl-thiazol-2-yl)-1H-pyrazole-4-carbonitrile (7) re-
acted with phenyl isothiocyanate, carbon disulphide, formic acid, and formamide
to furnish the pyrazolopyrimidines 8, 9, 16, and 17, respectively. Reaction of com-
pound 7 with malononitrile afforded pyrazolopyridine 10, while its reaction with
acetic anhydride, acetyl chloride, sulfuric acid, and triethylorthoformate gave thi-
azolylpyrazoles 12, 13, 15, and 18, respectively.
Keywords 2-hydrazino-4-phenylthiazole; pyrazolopyridine; pyrazolopyrimidines; thia-
zolylpyrazoles
INTRODUCTION
The thiazole ring has been identified as a central structure element
in a number of biological natural products1–4 and has broad applica-
tion in drug development for the treatment of allergies,5 hypertension,6
inflammation,7 bacterial infection,8 and HIV.9 In this work, we found a
good chance to introduce a pyrazole moiety in thiazole ring which has
wide applications in different industrial, biological, and medicinal fields
beside their application in synthetic organic chemistry.10–13 Moreover,
the biological activity of fused azoles has led to intensive research on
their synthesis.14–17
RESULTS AND DISCUSSION
We report here the synthesis of some new thiazolylpyrazoles, pyra-
zolopyridines and pyrazolopyrimidines. 2-Hydrazino-4-phenylthiazole
Received 24 October 2007; 2 accepted January 2008.
Address correspondence to Amer Anwar Amer, Department of Chemistry, Faculty of
Science, Sohag University, Sohag, Egypt. E-mail: amer chem@Yahoo.com.
2330

New Thiazolylpyrazole Derivatives and Compounds
2331
(1) was prepared via the reaction of phenacylbromide with thiosemi-
carbazide under reflux in dry ethanol.18 Compound 1 was allowed
to react with arylidenemalononitriles, namely; benzylidenemalonon-
itrile, p-hydroxy-, p-chloro- and p-nitro-benzylidenemalononitrile in
1:2 molar ratio in presence of a catalytic amount of triethylamine
to afford the corresponding 5-amino-3-aryl-1-(4-phenylthiazol-2-yl)-
1H-pyrazole-4-carbonitriles (2a-d), respectively. The reaction of com-
pound 1 with benzylidenecyanoacetamide, p-hydroxy-, p-chloro- and
p-nitrobenzylidenecyanoacetamide were carried out, where 5-amino-
3-phenyl-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-carboxamide
(2e),
5-amino-3-(p-hydroxyphenyl)-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-
carboxamide (2f), 5-amino-3-(p-chlorophenyl)-1-(4-phenylthiazol-2-yl)-
1H-pyrazole-4-carboxamide (2g) and 5-amino-3-(p-nitrophenyl)-1-(4-
phenylthiazol-2-yl)-1H-pyrazole-4-carb-oxamide (2h) were obtained,
respectively. By analogy, compound 1 was reacted with cyclohexylidene-
malononitrile in the presence of TEA as a basic catalyst to give 3-amino-
2-(4-phenylthiazol-2-yl)-1,2-diazaspiro[4.5]dec-3-ene-4-carbonitrile (3).
Also, treatment of compound 1 with ethyl benzyldenecyanoacetate,
ethyl p-hydroxy-, p-chloro- and p-nitrobenzyldenecyanoacetate where
5-hydroxy-3-aryl-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-carbonitriles
(4a-d) were obtained, respectively (c. f. Scheme 1).
The formation of compounds 2-4 was assumed to proceed via the
addition of the NH2 group of compound 1 to the activated double bond of
the ylidenenitriles to yield Michael adducts A-C, which in turn cyclized
through the addition of the NH group to the cyano group or at the
C O group with elimination of ethanol molecule. Aromatization was
gained by elimination of hydrogen molecule, which absorbed by another
molecule of the ylidenenitrile (c. f. Scheme 2).19–21 The acyclic adduct A
and the cyclic product D were ruled out based on elemental analysis and
1H NMR spectrum which revealed the absence of any protons attached
to SP3 carbons. Structures 2, 3, and 4 were confirmed by elemental as
well as spectroscopic data (c. f. Scheme 1, Table I).
Treatment of compound 1 with ethyl dimethylthiomethylene-
cyanoacetate in presence of TEA, yielded ethyl 5-hydroxy-3-methylthio-
1-(4-phenylthiazol-2-yl)-1H-pyrazole-4(2H)-carbonitrile (5). The for-
mation of compound 5 proceeded through the nucleophilic attack
of the NH2 group of compound 1 to the ethylenic bond with
the elimination of MeSH molecule, followed by a nucleophilic at-
tack of the NH group to the cyano group. While the reaction
of compound 1 with ethyl anilinomethylthiomethylenemalononitrile
yielded 3-anilino-3-methylthio-5-hydroxy-1-(4-phenylthiazol-2-yl)-1H-
pyrazole-4(1H)-carbonitrile (6). The reaction path way was proceed
via a nucleophilic attack of the NH2 group of compound 1 to the

2332
A. A. Amer
SCHEME 1
ethylenic bond without elimination of MeSH molecule, followed by a
nucleophilic attack of the NH group to the carbonyl group with elim-
ination of ethanol. It has been reported22,23 that some substituted
hydrazines react with ethoxymethylenemalononitrile giving the cor-
responding amino cyanopyrazoles, which are potential prune antago-
nists. In light of these results, it was of interest to use the hydrazino
compound 1 for the preparation of 5-amino-1-(4-phenylthiazol-2-yl)-1
H-pyrazole-4-carbonitrile (7), by the reaction of compound 1 with

New Thiazolylpyrazole Derivatives and Compounds
2333
SCHEME 2
ethoxymethylenemalononitrile in presence of TEA as a basic catalyst.
The chemical structures of compounds 5, 6, and 7 were confirmed by
elemental analysis as well as by spectroscopic methods (Scheme 2;
Table I).
The o-aminonitrile function in compound 7 was exploited to syn-
thesize some new pyrazolopyrimidines and pyrazolopyridine. The reac-
tion of compound 7 with phenylisothiocyanate and carbon disulphide
in ethanolic KOH solution provided 4-anilino-1-(4-phenylthiazol-2-yl)-
1H-pyrazolo[3,4-d]pyrimidine-6(1H)-thione (8) and 1-(4-phenylthiazol-
2 -yl)-1H-pyrazolo[3,4-d]pyrimidine-4,6(1H,3H)-dithione (9), respec-
tively. Compound 7 was allowed to react with malononitrile in glacial
acetic acid to yield 1:1 adduct. Such a product could be formulated as
the 4,6-diamino-1-(4-phenylthiazol-2-yl)-1H-pyrazolo[3,4-b]pyridine-5-
carbonit-rile (10) or 4-amino-1-(4-phenylthiazol-2-yl)-1H-pyrazolo-[3,4-
d]-pyrimidin-6-ylmethylcyanide (11). The structure 10 assigned for this
product on the basis of its 1H NMR spectrum revealed (beside the aro-
matic multiplet) two types of D2O-exchangeable protons and the ab-
sence of any protons attached to sp3 carbon.24 Treatment of compound 7
with acetic anhydride provided two products, which were identified as 5-
diacetylamino-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-carbonitrile (12)

2334

2335

2336

2337

2338
A. A. Amer
SCHEME 3
and 5-acetylamino-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-carbonitrile
(13), however the cyclized compound 14 was not obtained.13 Compound
13 was also prepared by an alternative route via the reaction of com-
pound 7 with acetyl chloride in the presence of TEA as a catalyst
(Scheme 3).
Hydrolysis of compound 7 with sulfuric acid gave 5-amino-1-(4-
phenylthiazol-2-yl)-1H-pyrazole-4-carboxamide (15), which was re-
acted with formamide to give 1-(4-phenylthiazol-2-yl)-4,5-dihydro-1H-
pyrazolo[3,4-d]pyrimidin-4-one (16). Compound 16 was also obtained by
an alternative route by refluxing compound 7 with an excess formic acid.
Treatment of compound 7 with an excess formamide afforded 4-amino-
1-(4-phenylthiazol-2-yl)-1H-pyrazolo[3,4-d]pyrimidine
(17).
The
condensation of compound 7 with triethyl orthoformate in boiling acetic
anhydride afforded the corresponding 5-(ethyoxymethyleneamino)-
1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-carbonitrile (18). The IR
spectrum of compound 18 showed bands at 2940 (CH aliph.) and 2215
(CN), the 1H NMR spectrum of (18 in DMSO-d6) revealed signals
at 8.6 (s, 1H, N CH ); 7.5–6.8 (m, 7H, arom. + 1H pyrazole + 1H
thiazole); 4.5–4.2 (q, J = 3; 3Hz; 2H, CH2); 1.4–1.1 (t; J = 4; 3 Hz,
3H, CH3). When compound 18 was treated with hydrazine hydrate in
benzene, the start compound 7 was recovered (m.p., m.m.p., and TLC)
instead of the expected pyrimidine 19. The formation of 7 from the
reaction of 18 with hydrazine hydrate was assumed to proceed via the

New Thiazolylpyrazole Derivatives and Compounds
2339
SCHEME 4
addition of hydrazine at the imino function group to form the inter-
mediate F, followed by the elimination of ethyl formate hydrazone25,26
(Scheme 4).
The structures of new compounds were confirmed based on elemental
analyses as well as spectral data (Table I).
CONCLUSION
This study illustrates that 2-Hydrazino-4-phenylthiazole (1) is a con-
venient starting material for the synthesis of thiazolylpyrazole, pyra-
zolopyrimidine and pyrazolopyridine derivatives. Due to the availabil-
ity of the starting materials, the simplicity of the procedures, and
the comparatively reasonable yields of the products, this synthetic ap-
proach might be valuable for the synthesis of such ring systems.
EXPERIMENTAL
All melting points were determined on a Koffler melting points appa-
ratus and are uncorrected. IR spectra were obtained on a Nicolet 710
1
FT-IR spectrometer. H NMR spectra were recorded on a Varian EM
360 at 60 MHz using TMS as an internal reference and DMSO-d6 as a

2340
A. A. Amer
solvent. Elemental analyses were performed on a Perkin-Elmer CHN-
2400C analyzer model.
Synthesis of 5-Amino-3-aryl-1-(4-phenylthiazol-2-yl)-1H-
pyrazole-4-carbonitriles (2a-d), 5-Amino-3-aryl-1-
(4-phenylthiazol-2-yl)-1H-pyrazole-4-carboxamide (2e-2h), and
5-Hydroxy-3-aryl-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-
carbonitriles (4a-d)—General Procedure
A mixture of compound 1 (0.01 mol, 1.91 g), the appropriate arylidene-
malononitril, arylidenecyanoacetamide or ethyl arylidenecyanoacetate
(0.02 mol), and few drops of TEA (0.02 mL) was refluxed in ethanol
(50 mL) for 4 h. The solid thus precipitated was collected and washed
several times with ethanol and recrystallized from an appropriate sol-
vent to give compounds 2a-h and 4a-d, respectively (Scheme 1, Table I).
Synthesis of 3-Amino-2-(4-phenylthiazol-2-yl)-1,2-diazaspiro
[4.5]dec-3-ene-4-carbonitrile (3), Ethyl 5-Hydroxy-3-
methylthio-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4(2H)-
carbonitrile (5), 3-Anilino-3-methylthio-5-hydroxy-1-
(4-phenylthiazol-2-yl)-1H-pyrazole-4(1H)-carbonitrile (6), and
5-Amino-1-(4-phenylthiazol-2-yl)-1H-pyrazole-4-carbonitrile
(7)—General Procedure
0.01 Mol of compound 1 (1.91 g), cyclohexylidenemalononitrile
(1.46 g), ethyl dimethylthiomethylenecyanoacetate (2.17 g), ethyl anili-
nomethylthiomethylenecyanoacetate (2.62 g), or ethoxymethylene-
malononitrile (1.22 g) and triethylamine (0.5 mL) was refluxed in
ethanol (30 mL) for 3 h. The solid thus precipitated on hot or after
cooling was collected and washed several times with ethanol and crys-
tallized from an appropriate solvent to give compounds 3, 5, 6, and 7,
respectively (Schemes 1 and 2, Table I).
Synthesis of 4-Anilino-1-(4-phenylthiazol-2-yl)-1H-pyrazolo
[3,4-d]pyrimidine-6(1H)-thione (8) and 1-(4-Phenylthiazol-2
-yl)-1H-pyrazolo[3,4-d]pyrimidine-4,6(1H,3H)-dithione (9)
A mixture of compound 7 (2.67 g, 0.01 mol), phenylisothiocyanate
(1.19 mL, 0.01 mol) or carbon disulphide (0.5 mL) and potassium hy-
droxide (1.12 g, 0.02 mol in 2 mL water) in ethanol (30 mL) was refluxed
for 14 h. On cooling, the reaction mixture was poured into ice-cold wa-
ter containing drops of HCl. The precipitated solid was filtered, dried

New Thiazolylpyrazole Derivatives and Compounds
2341
and recrystallized to give compounds 8 and 9, respectively (Scheme 3,
Table I).
Synthesis of 4,6-Diamino-1-(4-phenylthiazol-2-yl)-1H-
pyrazolo[3,4-b]pyridine-5-carbonit-rile (10)
To a solution of compound 7 (2.67 g, 0.01 mol) in glacial acetic acid
(20 mL), malononitrile (0.66 g, 0.01 mol) was added. The reaction mix-
ture was heated under reflux for 5 h, cooled to room temperature, and
poured onto an ice/H2O mixture. The solid product precipitated was fil-
tered off, washed several times with water, dried, and recrystallized to
give 10 (Scheme 3, Table I).
Synthesis of 5-Diacetylamino-1-(4-phenylthiazol-2-yl)-1H-
pyrazole-4-carbonitrile (12) and 5-Acetylamino-1-
(4-phenylthiazol-2-yl)-1H-pyrazole-4-carbonitrile (13)
Method A
Compound 7 (2.67 g, 0.01 mol) was refluxed in acetic anhydride
(9 mL) for three hours. The reaction mixture was cooled to room tem-
perature, poured into ice-cold water and the solid product precipitated
was filtered off, washed several times with water, dried, and recrys-
tallized from benzene to give 13. Benzene filtrate was evaporated and
the remaining residua was washed several times with petroleum ether
(40—60), then the solid obtained was filtered off, dried and recrystal-
lized to give 12 (Scheme 3, Table I).
Method B for the Preparation of Compound 13
A mixture of compound 7 (1.33 g, 0.005 mol), acetyl chloride (2.5 mL)
was refluxed in pyridine for 5 h. The reaction mixture was cooled to
room temperature and poured into ice-cold water. The solid product
precipitated was filtered off, washed several times with water, dried,
and recrystallized to give 13 (Scheme 3, Table I).
Synthesis of 5-Amino-1-(4-phenylthiazol-2-yl)-1 H-pyrazole-
4-carboxamide (15)
Concentrated sulfuric acid (30 mL) was cooled to 0◦C and compound 7
(2.67 g, 0.01 mol) was added and left at room temperature overnight.
The reaction mixture was poured onto ice/H2O mixture and the solid
product precipitated was filtered off, washed several times with water,
dried, and recrystallized to give 15 (Scheme 3, Table I)

2342
A. A. Amer
Synthesis of 1-(4-Phenylthiazol-2-yl)-4,5-dihydro-1H-
pyrazolo[3,4-d]pyrimidin-4-one (16)
Method A
A mixture of compound 15 (1.43 g, 0.005 mol) and formamide (10 mL)
was refluxed for 2 h. The reaction mixture was cooled to room temper-
ature and the precipitated product was filtered, washed several times
with water, dried, and crystallized to give 16 (Scheme 3, Table I).
Method B
Compound 7 (1.33 g, 0.005 mol) was heated under reflux with formic
acid (85%, 15 mL) for 15 h. The reaction mixture was cooling at room
temperature and the formed solid product was filtered off, washed sev-
eral times with water, dried, and crystallized to give 16 (Scheme 3,
Table I).
Synthesis of 4-Amino- 1-(4-phenylthiazol-2-yl)-1H-pyrazolo
[3,4-d]pyrimidine (17)
A mixture of compound 7 (1.33 g, 0.005 mol) and formamide (10 mL)
was refluxed for 3 h. The reaction mixture was concentrated and cooled
at room temperature, ethanol was added and the precipitated product
was filtered, washed several times with water, dried, and crystallized
to give 17 (Scheme 3, Table I).
Synthesis of 5-(Ethyoxymethyleneamino)-1-(4-phenylthiazol-
2-yl)-1H-pyrazole-4-carbonitrile (18)
A mixture of compound 7 (2.67g, 0.01 mol), triethyl orthoformate
(15 mL) and acetic anhydride (15 mL) was refluxed for 8 h. The reac-
tion mixture was concentrated to half volume, cooled and triturated
with cold ethanol. The separated product was filtered, washed with
petroleum ether (40–60◦C) and recrystallized to give 18 (Scheme 3,
Table I).
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