One-pot PTC synthesis of polyfused pyrazoles

Article abstract of DOI:10.1002/hc.10129

Thienopyrazole 2, 3, 5, or 6 and thienopyrazolothiazepine 7, 9, and 11 derivatives were prepared via the reaction of the 3-aminopyrazoline-5-one 1 with CS₂ and different molar ratio of a variety of halo compounds having an active methylene under PTC conditions. Also, treatment of 1 with CS₂ and alcoholic KOH in 2:1:1 molar ratio afforded dipyrazolopyridine derivatives 12 and 14. On other hand, the pyrazolothiadiazineone derivative 13 was obtained by treating compound 1 with CS₂ and alcoholic KOH in 1:2:2 molar ratio. Under PTC conditions, compound 1, CS₂, and ethyl cyanoacetate or malononitrile to gave the pyrazolopyridine derivatives 16 and 17. Coupling of compound 1 with diazonium acetates afforded the hydrazone derivatives 18a,b, which were oxidized with bromine to give pyrazolotriazoles 19a,b or cyclized with aldehydes to give pyrazolotriazine derivatives 20a-e. Bromination of compound 1 afforded monobromopyrazole derivative 21, which could be condensed to a dipyrazolopyrazindione 23. Finally, the dibromopyrazole derivative 22 was cyclized with 2-mercaptoethanol or o-phenylenediamine to give the spiropyrazoles 24a,b.

Full text of DOI:10.1002/hc.10129

Heteroatom Chemistry
Volume 14, Number 3, 2003
One-Pot PTC Synthesis of Polyfused
Pyrazoles
Gamal A. El-Saraf, Ahmed M. El-Sayed,
and Ahmed M. M. El-Saghier
Department of Chemistry, Faculty of Science, South Valley University, Sohag, Egypt
Received 25 May 2002; revised 22 June 2002
INTRODUCTION
ABSTRACT: Thienopyrazole 2, 3, 5, or 6 and
thienopyrazolothiazepine 7, 9, and 11 derivatives were
prepared via the reaction of the 3-aminopyrazoline-5-
one 1 with CS2 and different molar ratio of a variety
of halo compounds having an active methylene un-
der PTC conditions. Also, treatment of 1 with CS2 and
alcoholic KOH in 2:1:1 molar ratio afforded dipyra-
zolopyridine derivatives 12 and 14. On other hand, the
pyrazolothiadiazineone derivative 13 was obtained by
treating compound 1 with CS2 and alcoholic KOH in
1:2:2 molar ratio. Under PTC conditions, compound
1, CS2, and ethyl cyanoacetate or malononitrile to
gave the pyrazolopyridine derivatives 16 and 17. Cou-
pling of compound 1 with diazonium acetates afforded
the hydrazone derivatives 18a,b, which were oxidized
with bromine to give pyrazolotriazoles 19a,b or cy-
clized with aldehydes to give pyrazolotriazine deriva-
tives 20a–e. Bromination of compound 1 afforded
monobromopyrazole derivative 21, which could be
condensed to a dipyrazolopyrazindione 23. Finally,
the dibromopyrazole derivative 22 was cyclized with
2-mercaptoethanol or o-phenylenediamine to give the
Pyrazoles and their derivatives are used as pharma-
ceuticals and agrochemicals, the earliest example,
antipyrine, dating from 1884 [1]. Also, fused pyra-
zoles have fungicidal [2,3], herbicidal [4,5], viruci-
dal [6], insecticidal [7,8] activity and used for the
treatment of rheumatoid arthritis [9–11]. The chem-
istry of pyrazoles has received much attention and
many methods for their synthesis have been devel-
oped [12]. Various heterocyclic systems containing a
pyrazole moiety have been prepared by 1,3-dipolar
cycloaddition of iminonitriles to activated olefins
[13–16]. This motivated us to synthesize some new
fused and spiropyrazoles under PTC conditions.
RESULTS AND DISCUSSION
In an extension of our recent studies [17–23] on the
application of PTC in heterocyclic synthesis, starting
with an active methylene compounds containing
ꢀ-keto or ꢀ-cyano group, herein we report the
synthesis of some new fused and spiro pyrazole
heterocycles starting with 3-amino-1-phenyl-2-
pyrazolin-5-one (1). Compound 1 was allowed to
react with CS2 and a variety of halo compounds
having an active methylene, including chloroace-
tonitrile, ethyl chloroacetate, or phenacyl bromide
in 1:1:1 molar ratio, under PTC conditions [K2CO3/
dioxane/tetrabutylammonium bromide (TBAB)],
where 3-amino-1-phenyl-4-thioxo-3a,4-dihydro-1H-
thieno[3,4-c]pyrazol-6-ylcarbonitrile (2), ethoxy(3-
amino-1-phenyl-4-thioxo-3a,4-dihydro-1H-thieno[3,
ꢀ
C
spiropyrazoles 24a,b.
2003 Wiley Periodicals, Inc.
Heteroatom Chem 14:211–217, 2003; Published online
in Wiley InterScience (www.interscience.wiley.com). DOI
10.1002/hc.10129
Correspondence to: Gamal A. El-Saraf; e-mail: saraf-g@lycos.
com.
c
ꢀ
2003 Wiley Periodicals, Inc.
211

212 El-Saraf, El-Sayed, and El-Saghier
4-c]pyrazo-6-yl)-1-methanone (3) or 3-amino-1-
phenyl-4-thioxo-3a,4-dihydro-1H-thieno[3,4-c]pyra-
zol-6-ylphenyl-1-methanone (5), and 3-hydroxy-2-
phenyl-4-thioxo-2,4-dihydro-1H-thieno[3,4-c]-pyra-
zol-6-ylphenyl-1-methanone (6) were obtained.
The reaction is assumed to involve a nucleophilic
attack of the generated carbanion of the pyrazole
ring on CS2, followed by alkylation of the formed
dithiocarboxylate group with halo compounds and
cyclization. On refluxing compound 3 with mal-
ononitrile in presence of piperidine as catalyst, 3-
ethoxycarbonyl-6-amino-2-phenyl-2-hydro-4-thia-1,
2,7-triazacyclopenta[cd]-inden-5-ylcarbonitrile (4)
was obtained. Moreover, the reaction of compound 1
with CS2 and the same halo compounds but in 1:1:2
molar ratio under the same PTC conditions afforded
7-amino-2-phenyl-2,6-dihydro-4,5-dithia-1,2,8-tria-
zacyclopenta[cd]azulen-3-ylcarbonitrile (7), 3-ethox-
carbonyl-2-phenyl-2,6,7,8-tetrahydro-4,5-dithia- 1,2,
8-triazacyclopenta[cd]azulen-7-one (9), or 2,7-diphe-
nyl-2,6-dihydro-4,5-dithia-1,2,8-triazacyclopenta[cd]-
azulen-3-ylphenyl-1-methanone (11) along with
S-alkylated thienopyrazole derivative 8 or 10 as an
intermediate (Scheme 1).
[3,4-b:4,3-e]pyridin-3-one (12), which was treated
with ethyl chloroacetate under the proceeding
PTC conditions to give ethoxy(8-hydroxy-3,7-
diphenyl-5,7-dihydro-3H-1-thia-3,4,5,6,7-pentaaza-
cyclopenta[cd]-s-indacen-2-yl)-1-methanone (14).
On the other hand, 6-phenyl-2,4-dithioxo-2,6,7,8-
tetrahydropyrazolo[1,5-c][1,3,5]-thiadiazin-7-one
(13) was obtained by treating compound 1 with
CS2 and alcoholic KOH in 1:2:2 molar ratio, which
was reacted with hydrazine hydrate [16,17] in
refluxing ethanol, where H2S gas was evolved to
afford
3-amino-6-phenyl-2,4-dithioxo-2,3,4,6,7,8-
hexahydropyrazolo[1,5-a][1,3,5]triazin-7-one (15)
(Scheme 2). The structure of these compounds were
1
confirmed using IR, H-NMR, MS, and elemental
analysis (Table 1).
Treatment of compound 1 with CS2 under PTC
conditions afforded pyrazole dithioc acid, which was
allowed to react in situ with equimolar ratio of active
nitriles including ethyl cyanoacetate or malononi-
trile to give 6-amino-5-ethoxycarbonyl-2-phenyl-4-
thioxo-3,3a,4,7-tetrahydro-2H-pyrazolo-[3,4-b]pyri-
din-3-one (16) or 6-amino-3-oxo-4-mercapto-2-phe-
nyl-3,3a,4,7-tetrahydro-2H-pyrazolo[3,4-b]pyridin-5-
ylcarbonitrile (17), respectively (Scheme 3).
p-Chloro- and p-methylbenzenediazonium ace-
tate was coupled with 1 to afford 3-amino-4-aryl-
hydrazono-1-phenylpyrazol-5-one derivatives 18a
or 18b, respectively. The mass spectrum of com-
pound 18b showed m/z 293 (relative intensity 100).
Oxidation of compounds 18a,b with bromine in
acetic acid gave the 2,5-diphenyl-2,3,5,6-tetrahydro-
pyrazolo[3,4-d][1,2,3]triazol-6-ones (19a,b). Also,
treatment of 18a,b with benzaldehyde, p-anisa-
ldehyde, or p-nitrobenzaldehyde afforded the
2,3,6-tri-phenyl-3,4,6,7-tetrahydro-2H-pyrazolo[3,4-
e][1,2,4]-triazin-7-ones (20a–e). The mass spectrum
of 20a showed m/z 401.5 (relative intensity 0.9)
(Scheme 4).
The reaction of compound 1 with CS2 and al-
coholic KOH in 2:1:1 molar ratio gave 5-hydroxy-4-
mercapto-2,6-diphenyl-2,3,6,8-tetrahydrodipyrazolo-
SCHEME 1
SCHEME 2

One-Pot PTC Synthesis of Polyfused Pyrazoles 213

214 El-Saraf, El-Sayed, and El-Saghier

One-Pot PTC Synthesis of Polyfused Pyrazoles 215
SCHEME 3
SCHEME 5
Bromination of compound 1 in 1:1 or 1:2 molar
ratio afforded 3-amino-4-bromo-1-phenyl-2-pyrazol-
5-one (21) or 3-amino-4,4-dibromo-1-phenyl-2-pyra-
zol-5-one (22), respectively. Refluxing of compound
21 in ethanol with triethylamine in 1:2 molar ratio
gave 2,6-diphenyl-2,3,3a,4,6,7,7a,8-octahydrodipyr-
azolo[3,4-b:3,4-e]pyrazin-3,7-dione (23). 3ꢁ-Amino-
1ꢁ-phenylspiro[perhydro[1,3]oxathiolane-2,4ꢁ-(1ꢁ ,5ꢁ -
dihydropyrazol)]-5ꢁ-one (24a) and 3ꢁ-amino-1ꢁ-
phenylspiro[1,3-dihydrobenzo[d]imidazole-2,4ꢁ-(1ꢁ,
5ꢁ-dihydropyrazole)]-5ꢁ-one (24b) were obtained by
treating compound 21 with mercaptoethanol or
o-phenylenediamine, respectively (Scheme 5).
Synthesis of Compounds 2, 3, 5–11
General Procedure. To a solution of compound 1
(0.01 mol) in dioxane (30 ml) was added anhydrous
potassium carbonate (3 g), TBAB (0.5 mmol), and
carbon disulfide (0.01 mol), and finally chloroace-
tonitrile, ethyl chloroacetate or phenacyl bromide
(0.01 or 0.02 mol). The reaction mixture was stirred
for 10–12 h, filtered, and the solid potassium car-
bonate layer was dissolved in water and filtered. The
filterate was acidified with acetic acid and the sepa-
rated solid was crystallized from the suitable solvent
to give compounds 2, 3, 6, 7, 9, or 11 as yellow nee-
dles. The organic layer was evaporated in vacuo and
the residue was treateds with water filtered, and crys-
tallized from the suitable solvent to give compounds
5, 8, or 10 as orange needles (Table 1).
EXPERIMENTAL
All melting points were determined on a Gallenkamp
apparatus and are uncorrected. IR spectra were
recorded on a Nicolet710 FT-IR spectrophotometer,
using the KBr wafer technique. 1H NMR spectra were
measured on a Varian EM 360L, 60 MHz NMR spec-
trometer in a suitable deuterated solvent, using TMS
as internal standard. Elemental analyses were per-
formed on a Perkin–Elmer 240 C microanalyzer.
13C NMR of 2, 5, 9, and 11 (dimethyl sulfoxide-
d6, δ ppm): 2: 38.86, 40.13, 100.10, 114.08, 118.10,
120.06, 123.33, 128.55, 180.95, 205.11. 5: 38.87,
93.12, 117.43, 118.86, 127.43, 127.92, 128.50,
128.75, 128.87, 129.66, 133.48, 135.33, 194.61,
203.09. 9: 31.79, 57.53, 61.33, 107.23, 118.23,
123.17, 128.47, 140.00, 149.00, 159.46, 166.00,
168.02, 183.92, 211.23. 11: 40.12, 103.47, 107.92,
117.69, 118.01, 118.76, 123.13, 124.37, 128.56,
128.90, 137.53, 139.88, 145.26, 157.34, 159.12,
160.31,168.02, 188.63, 191.76, 201.31.
MS of 6: m/e (relative intensity) 352 (2.50), 319
(1.40), 247 (1.10), 234 (2.73), 223 (9.55), 142 (48.36),
129 (2.90), 105 (100.00), 100 (33.55), 93 (20.00), 77
(82.93), 55 (10.20).
3-Ethoxycarbonyl-6-amino-2-phenyl-
2,7-dihydro-4-thia-1,2,7-triazacyclopenta[cd]-
inden-5-yl Carbonitrile (4)
A mixture of compound 3 (0.003 mol, 1.053 g) and
SCHEME 4
malononitrile (0.003 mol) in 30 ml of dioxane and a

216 El-Saraf, El-Sayed, and El-Saghier
few drops of piperidine was refluxed until H2S gas
ceased (7 h). The solvent was evaporated and the
residue was diluted with water and acidified with hy-
drochloric acid. The precipitate was collected by fil-
teration and crystallized from ethanol/water to give
compound 4 as dark brown needles.
cyanoacetate or malononitrile (0.01 mol) was stirred
for 4 or 2 h at 60◦C, and then filtered. The solid potas-
sium carbonate was dissolved in water and filtered.
The filtrate was acidified with acetic acid. The pre-
cipitate was crystallized from a suitable solvent to
give compound 16 as yellow needles or 17 as orange
needles (Table 1).
13C NMR of compounds 16 and 17 (dimethyl
sulfoxide-d6,δ ppm): 16: 38.87, 47.49, 47.91, 108.06,
117.98, 123.03, 128.56, 140.06, 143.81, 159.26,
188.83, 191.44, 213.80. 17: 119.26, 127.90, 127.95,
128.08, 128.50, 128.60, 128.74, 133.11, 145.62,
174.92, 203.72.
Synthesis of Compounds 12 or 13
General Procedure. To a solution of 1 (0.01 mol)
in 40 ml alcoholic potassium hydroxide (0.005 mol
or 0.02 mol), carbon disulfide (0.005 mol or 0.02 mol)
was added. The reaction mixture was refluxed for 10–
12 h (until H2S ceased), concentrated, diluted with
water, and filtered. The filtrate was acidified with di-
lute hydrochloric acid, and the separating solid was
collected by filtration and crystallized from ethyl al-
cohol to give compounds 12 or 13 as orange needles
(Table 1).
3-Amino-4-arylhydrazono-1-phenyl-2-pyrazolin-
5-ones (18a,b)
A solution of the diazonium salt synthesized from
p-chloroaniline or p-toluidine, sodium nitrite, and
sodium acetate/acetic acid (0.01 mol) was added to
a solution of 1 (1.75 g, 0.01 mol) in acetic acid (20
ml) at 0–4◦C with stirring. The reaction mixture was
kept at room temperature for 24 h and the obtained
solid was filtered and crystallized from ethanol/water
to give compound 18a as red needles or compound
18b as violet needles.
Ethoxy(8-hydroxy-3,7-diphenyl-5,7-dihydro-
3H-1-thia-3,4,5,6,7-pentaazacyclopenta[cd]-s-
indacen-2-yl)-1-methanone (14)
A mixture of compound 12 (0.01 mol), anhydrous
potassium carbonate (3 g), and a catalytic amount of
TBAB (0.5 mmol) in dioxane (20 ml) was stirred for
45 min at 40◦C, then ethyl chloroacetate (0.01 mol)
was added. The reaction mixture was stirred for 8 h
at 60◦C, and filtered. The organic layer was dried over
anhydrous sodium sulphate and evaporated in vacuo
and the residual solid was crystallized from ethanol
to give compound 14 as pale yellow needles (Table 1).
13C NMR of (18b) (dimethyl sulfoxide-d6, δ ppm):
20.52, 115.63, 117.07, 122.21, 123.68, 128.83, 129.89,
134.24, 138.56, 139.48, 150.72, 155.45.
MS of 18b: m/z (relative intensity) 293 (100), 202
(7.2), 187 (1.0), 174 (1.9), 132 (1.5), 106 (15.7).
2,5-Diphenyl-2,3,5,6-tetrahydropyrazolo[3,4-d]-
[1,2,3]triazol-6-ones (19a,b)
3-Amino-6-phenyl-2,4-dithioxo-2,3,4,6,7,
8-hexahydro-pyrazolo[1,5-a][1,3,5]triazin-
7-one (15)
To a solution of 18a or 18b (0.004 mol) in 20 ml of
acetic acid was added bromine (0.21 ml; 0.004 mol)
in 5 ml acetic acid dropwise (10 min). The reaction
mixture was stirred for 24 h at room temperature,
then poured into water, filtered, and the product crys-
tallized from ethanol to give compound 19a or 19b
as orange needles.
To a solution of compound 13 (0.003 mol) in water
(30 ml), hydrazine hydrate (0.006 mol) was added.
The reaction mixture was refluxed for 4 h and filtered
hot. The filterate was cooled and acidified with dilute
hydrochloric acid. The precipitate was collected by
filtration and crystallized from ethyl alcohol to give
compound 15 as yellow needles.
2,3,6-Triphenyl-3,4,6,7-tetrahydro-2H-
pyrazolo[3,4-e][1,2,4]triazin-7-ones (20a–e)
5-Ethoxycarbonyl-6-amino-2-phenyl-4-thioxo-3,
3a,4,5-tetrahydro-2H-prazolo[3,4-b]pyridin-3-
one(16) and 6-Amino-3-oxo-2-phenyl-4-thioxo-
3,3a,4,5-tetrahydro-2H-prazolo[3,4-b]pyridin-5-
yl Carbonitrile (17)
Benzaldehyde, anisaldehyde, or p-nitrobenzalde-
hyde (0.005 mol) was added to compound 18a or
18b (0.005 mol) in absolute ethanol (20 ml) in pres-
ence of two drops of piperidine. The reaction mixture
was refluxed for 3 h, filtered hot, concentrated, and
cooled. The precipitate were collected by filteration
and crystallized from a suitable solvent to give 20a–e
as yellow needles.
A mixture of 1 (0.01 mol), anhydrous potassium
carbonate (3 g), a catalytic amount of TBAB, diox-
ane (40 ml), carbon disulfide (0.01 mol) and ethyl

One-Pot PTC Synthesis of Polyfused Pyrazoles 217
13C NMR of 20e (dimethyl sulfoxide-d6, δ ppm):
23.08, 57.55, 97.65, 98.78, 116.30, 116.77, 120.73,
121.95, 123.17, 128.18, 128.39, 140.24, 141.46,
143.90, 151.22, 153.65, 163.41, 178.04.
MS of 20a: m/z (relative intensity) 401.5 (0.9),
311.5 (0.9), 278 (1.2), 202 (7.5).
(9.1), 91 (24.3), 77 (22.4), 76 (15.9), 44 (38.8), 28
(30.0).
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refluxed for 3 h, evaporated in vacuo, and the solid
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yellow needles.
3ꢁ-Amino-1ꢁ-phenyl-spiro[perhydro[1,3]-
oxathiolane-2,4ꢁ-(1ꢁ,5ꢁ-dihydropyrazole)]-5ꢁ-one
(24a) and 3ꢁ-Amino-1ꢁ-phenylspiro[1,3-dihydro-
benzo-[d]-imidazol-2,4ꢁ-(1ꢁ,5ꢁ-dihydropyrazol)]-
5ꢁ-one (24b)
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(0.324 g, 0.003 mol) was refluxed in the pres-
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was washed with water, and crystallized from ben-
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MS of 24a: m/z (relative intensity) 249 (4.2), 173
(15.6), 172 (21.7), 171 (100), 156 (8.7), 145 (7.5), 119