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A New Approach for the Synthesis of Some Pyrazolo
[5,1-c]triazines and Pyrazolo[1,5-a]pyrimidines Containing
Naphtofuran Moiety
Abdou O. Abdelhamid,
a
* Shokry A. Shokry,
b
and Sayed M. Tawfiek
b
a
Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt
b
Science & Technology Center of Excellence, Slam 2nd., P.O. Box 3066, Egypt
*E-mail: Abdelhamid45@gmail.com
Received June 4, 2010
DOI 10.1002/jhet.699
Published online 13 October 2011 in Wiley Online Library (wileyonlinelibrary.com).
Naphtho[2,1-b]furan-2-yl)(8-phenylpyrazolo[5,1-c][1,2,4]triazin-3-yl)methanone, ([1,2,4]triazolo[3,
4-c][1,2,4]triazin-6-yl)(naphtho[2,1-b]furan-2-yl)methanone, benzo[4,5]imidazo[2,1-c][1,2,4]triazin-3-yl-
naphtho[2,1-b]furan-2-yl-methanone, 5-(naphtho[2,1-b]furan-2-yl)pyrazolo[1,5-a]pyrimidine, 7-(naph-
tho[2,1-b]furan-2-yl)-[1,2,4]triazolo[4,3-a]pyrimidine, 2-naphtho[2,1-b]furan-2-yl-benzo[4,5]imidazo[1,
2-a]pyrimidine, pyridine, and pyrazole derivatives are synthesized from sodium salt of 5-hydroxy-1-
naphtho[2,1-b]furan-2-ylpropenone and various reagents. The newly synthesized compounds were eluci-
dated by elemental analysis, spectral data, chemical transformation, and alternative synthetic route
whenever possible.
J. Heterocyclic Chem., 49, 116 (2012).
INTRODUCTION
The considerable biological and medicinal activities
of pyrazolotriazines and triazolotriazines, as adenine
analogues, antagonists, antischistosomal, and antitumor
agents [1–3] have stimulated recent interest in the syn-
thesis of these ring systems. Pyrazolo[1,5-a] pyrimidines
are purine analogues and as such have useful properties
as antimetabolites in purine biochemical reactions. Com-
pounds of this class have attracted wide pharmaceutical
interest because their antitrypanisommal activity, [4]
antischistosomal activity [5], activity as HMG-CoA re-
ductase inhibitors [6], COX-2 selective inhibitors [7],
AMP phosphodiesterase inhibtors [8], KDR kinas inhibi-
tors [9], selective peripheral benzodiazepine receptor
ligands [10], and as antianxiety agents [11]. Recently
other pharmaceutical activity has been reported, for
example, as an agent for the treatment of sleep disorders
[12] and as an oncological agent [8,13]. The show
examples highlight the high level of interest in variously
substituted pyrazolo[1,5-a]pyrimidines and their modi-
fied analogues there is a wide range of methods avail-
able for the synthesis of pyrazolo[1,5-a]pyrimidines
[14]. In continuation of our interest in the synthesis of
heterocycles [15–19], we report herein, a convenient
method for the synthesis of pyrazolo[5,1-c]triazines, pyr-
azolo[1,5-a]pyrimidines, and pyridine containing naph-
thofuran moiety as antimicrobial agents.
RESULTS AND DISCUSSION
Treatment of the diazotized 3-amino-5-phenylpyrazole
(3a) with sodium salt of 5-hydroxy-1-naphtho[2,1-
b]furan-2-ylpropenone (2), which prepared from 1-naph-
tho[2,1-b]furan-2-ylethanone and ethyl formate in
V
C2011 HeteroCorporation
116 Vol 49
presence of sodium methoxide, in ethanolic sodium ace-
tate solution gave (naphtho[2,1-b]furan-2-yl)(7-phenyl-
pyrazolo[5,1-c][1,2,4]triazin-3-yl)methanone (6a)in
good yield (Scheme 1). Structure 6a was elucidated by
elemental analysis, spectral data and alternative syn-
thetic route. The formation of 6a accorded via coupling
diazonium chloride 3a to 2to form the intermediate 4
which converted to 5. The later afforded the final prod-
uct 6through elimination of one molecule of water.
Meanwhile, treatment of 3-dimethylamino-1-naph-
tho[2,1-b]furan-2-ylpropenone [20] (7) with 3a in etha-
nolic sodium acetate as buffer solution gave product
identical in all respects mp., mixed mp., and spectra
with 6a (Scheme 1). Analogously, treatment of the
appropriate diazonium salt 3b-e with 2in ethanolic so-
dium acetate afforded (naphtho[2,1-b]furan-2-yl)(8-phe-
nylpyrazolo[5,1-c][1,2,4]triazin-3-yl)methanone (6b), 3-
(naphtho[2,1-b]furan-2-carbonyl)-pyrazolo[5,1-c][1,2,4]
triazine-8-carbonitrile (6c), ([1,2,4]triazolo[3,4-c][1,2,4]
triazin-6-yl)(naphtho[2,1-b]furan-2-yl)methanone (6d),
and benzo[4,5]imidazo[2,1-c][1,2,4]triazin-3-yl-naphtho
[2,1-b]furan-2-yl-methanone (6e), respectively.
On the other hand, treatment of 2with 3-amino-5-phe-
nylpyrazole (10a) in piperidenium acetate yielded 7-naph-
tho[2,1-b]furan-2-yl-2-phenylpyrazolo[1,5-a]pyrimidine
(13a). The structure 13a was established by elemental anal-
ysis, spectral data, and alternative synthetic route. Thus,
treatment of 7with 3a in boiling acetic acid containing am-
monium acetate gave product identical in all aspects (mp.,
mixed mp., and spectra) with 13a (Scheme 2).
1
H NMR spectrum of 13a revealed multiple band at
d¼7.35–8.55 (m, aromatic protons). The formation of
Scheme 1
January 2012 117A New Approach for the Synthesis of Some Pyrazolo[5,1-c]Triazines and
Pyrazolo[1,5-a]pyrimidines Containing Naphtofuran Moiety
Journal of Heterocyclic Chemistry DOI 10.1002/jhet
compounds 13 assumed to take place via an initial Mi-
chael addition of the exocyclic amino group in com-
pound 7(or 2) to the activated double bond in 7to give
the acyclic non-isolable intermediate 14, which undergo
cyclization and aromatization via loss of both dimethyl-
amine and water molecules producing the final isolable
products 13a-e. Although the endocyclic imino group in
compounds 10a–eis the most nucleophilic center,
nevertheless, it is the most sterically hindered site [21]
as shown in Scheme 2. Structure 13a was further con-
firmed via an independent synthesis by reacting equimo-
lar amounts of 16 [22] with 1in ethanol under reflux to
provide a product identical in all respects (m.p., thin-
layer chromatography, and spectra) with those of the
proposed structure 13a. Analogously, compound 2was
reacted with the appropriate of 3-amino-4-phenylpyra-
zole (10b), 3-amino-4-cyanopyrazole (10c), 3-aminotria-
zole or 2-aminbenzimidazole (10d) to give 7-naph-
tho[2,1-b]furan-2-yl-2-phenylpyrazolo[1,5-a]pyrimidine
(13b), 7-naphtho[2,1-b]furan-2-yl-pyrazolo[1,5-a]pyrimi-
dine-3-carbonitrile (13c), 7-naphtho[2,1-b]furan-2-yl-
[1,2,4]triazolo[4,3-a]pyrimidine (13d), and 4-naph-
tho[2,1-b]furan-2-yl-benzo[4,5]imidazo[1,2-a]pyrimidine
(13e), respectively (Scheme 2).
Next, treatment of 3-dimethylamino-1-naphtho[2,1-
b]furan-2-ylpropenone (7) with each of acetylacetone,
Scheme 2
118 Vol 49A. O. Abdelhamid, S. A. Shokry, and S. M. Tawfiek
Journal of Heterocyclic Chemistry DOI 10.1002/jhet
ethyl acetoactate, or benzoylacetonitrile in boiling acetic
acid containing ammonium acetate under reflux gave 1-
(2-methyl-6-(naphtho[1,2-b]furan-2-yl)pyridin-3-yl)etha-
none (19), ethyl 2-methyl-6-(naphtho[1,2-b]furan-2-yl)
pyridine-3-carboxylate (20), and (2-amino-6-(naphtho
[1,2-b]furan-2-yl)pyridin-3-yl)(phenyl)methanone (22),
respectively (Scheme 3). Compound 20 was reacted
with hydrazine hydrate to afford 2-methyl-6-(naph-
tho[1,2-b]furan-2-yl)pyridine-3-carbohydrazide (23). The
structure of 23 was elucidated by elemental analysis,
spectra and chemical transformations. Thus, compound
23 was reacted with each of nitrous acid, acetylacetone,
and ethyl acetoacetate to give azido(2-methyl-6-(naph-
tho[2,1-b]furan-2-yl)pyridin-3-yl)methanone (24), (3,5-
dimethyl-1H-pyrazol-1-yl)(2-methyl-6-(naphtho[2,1-b]
furan-2-yl)pyridin-3-yl)methanone (25) and (5-methyl-2-
(2-methyl-6-naphtho[2,1-b]furan-2-yl-pyridine-3-carbonyl)-
2,4-dihydro-pyrazol-3-one (26), respectively. Treatment
the compound 26 with 4-methylbenzenediazonium chlo-
ride gave the corresponding 27.
Finally, treatment of 2or 7with the benzenediazo-
nium chloride in ethanol containing sodium acetate as a
buffer solution yielded 2-(2-phenylhydrazono)-3-(naph-
tho[2,1-b]furan-2-yl)-3-oxopropanal (28a). Structure
28a was confirmed by elemental analysis, spectral data,
and chemical transformation.
1
HNMRspectrumof28a
showed signal at d¼7.26–7.93 (m, 7 H, ArH’s), 9.98
(s, 1H, ACHO) and 14.39 (s, br., 1H, NH). Thus, 28a
was reacted with hydrazine hydrate in boiling ethanol
under reflux to give 1-(3-(naphtho[2,1-b]furan-2-yl)-1H-
pyrazol-4-yl)-2-phenyldiazene (29a) (Scheme 4). Also,
7reacted with hydrazine hydrate to give 3-(naph-
tho[2,1-b]furan-2-yl)-1H-pyrazole (30a). Compound
30a was reacted with benzenediazonium chloride in
ethanolic sodium acetate solution to afford product
identical in all respect mp., mixed mp., and spectra
with 29a.
EXPERIMENTAL
All melting points were determined on an electrothermal ap-
paratus and are uncorrected. IR spectra were recorded (KBr
discs) on a Shimadzu FT-IR 8201 PC spectrophotometer.
1
H
NMR and spectra were recorded in CDCl
3
and (CD
3
)
2
SO solu-
tions on a Varian Gemini 300 MHz spectrometer and chemical
shifts are expressed in dunits using tetramethylsilane as an in-
ternal reference. Mass spectra were recorded on a GC-MS
QP1000 EX Shimadzu. Elemental analyses were carried out at
the Microanalytical Center of the Cairo University.
Sodium salt of 5-hydroxy-1-naphtho[2,1-b]furan-2-ylpro-
penone (2). In three-necked flask (250 mL) take of sodium
methoxide (0.054 g, 10 mmoles) and ether (20 mL) and pour
over it through separating funnel the 1-(naphtho[2,1-b]furan-2-
yl)ethanone (1) (2.1g, 10 mmoles) with ethyl formate (0.74 g,
10 mmoles) with efficient stirring. The solid product was col-
lected and used directly in the reactions.
Scheme 3
January 2012 119A New Approach for the Synthesis of Some Pyrazolo[5,1-c]Triazines and
Pyrazolo[1,5-a]pyrimidines Containing Naphtofuran Moiety
Journal of Heterocyclic Chemistry DOI 10.1002/jhet
(Naphtho[2,1-b]furan-2-yl)(7-phenylpyrazolo[5,1-c][1,2,4]
triazin-3-yl)methanone (6a), (naphtho[2,1-b]furan-2-yl)(8-
phenylpyrazolo[5,1-c][1,2,4]triazin-3-yl)methanone (6b), 3-
(naphtho[2,1-b]furan-2-carbonyl)-pyrazolo[5,1-c][1,2,4]tria-
zine-8-carbonitrile (6c), ([1,2,4]triazolo[3,4-c][1,2,4]triazin-
6-yl)(naphtho[2,1-b]furan-2-yl)methanone (6d), and ben-
zo[4,5]imidazo[2,1-c][1,2,4]triazin-3-yl-naphtho[2,1-b]furan-2-
yl-methanone (6e). Method A. A solution of the appropriate
diazonium salt of heterocyclic amines (3-amino-5-phenylpyra-
zole (3a), 3-amino-4-phenylpyrazole (3b), 3-amino-4-cyano-
pyrazole (3c), 3-amino-1,2,4-triazole (3d), 2-amino-benzimida-
zole (3e) (5 mmole) was added to a mixture of sodium salt of
5-hydroxy-1-naphtho[2,1-b]furan-2-ylpropenone (2) (5 mmole),
sodium acetate (0.65 g, 5 mmole) in ethanol (30 mL) at 0–5C
while stirring. The resulting solid which formed after 3 h was
collected, washed with water, and recrystallized to give 6a-d.
Method B. A solution of the appropriate diazonium salt of
heterocyclic amines (3-amino-5-phenylpyrazole (3a), 3-amino-
4-phenylpyrazole (3b), 3-amino-4-cyanopyrazole (3c), 3-
amino-1,2,4-triazole (3d), 2-amino-benzimidazole (3e)3a–e
(5 mmole) was added to a mixture of 3-dimethylamino-1-naph-
tho[2,1-b]furan-2-ylpropenone (7) (1.32 g, 5 mmole), sodium
acetate (0.65 g, 5 mmole) in ethanol (30 mL) at 0–5C while
stirring. The resulting solid which formed after 3 h was col-
lected, washed with water, and recrystallized from acetic acid
to give products identical in all aspects mp., mixed mp., and
spectra with the corresponding obtained in method A.
(Naphtho[2,1-b]furan-2-yl)(7-phenylpyrazolo[5,1-c][1,2,4]tri
azin-3-yl)methanone (6a). Yellow crystals from AcOH, yield
(68%), mp: 272–74C; IR (KBr): 3059 (CH, aromatic), 1638
(C¼¼O conjugated), 1618 (C¼¼N), and 1586 (C¼¼C);
1
H NMR
(CDCl
3
): d¼7.53–8.35 (m, 12H, ArH’s), 9.0 (d, 1H, ArH)
and 9.43 (s, 1H, ArH); MS: m/z ¼390 (Mþ, 77.1%), 206
(36.2%), 139 (100%), 77 (77.1%); Anal. Calcd. for
C24H14N4O
2
(390.11) C, 73.84; H, 3.61; N, 14.35. Found: C,
73.67; H, 3.81; N, 14.51%.
(Naphtho[2,1-b]furan-2-yl)(8-phenylpyrazolo[5,1-c][1,2,4]tri
azin-3-yl)methanone (6b). Yellow crystals from AcOH, yield
(76%), mp: 280–82C; IR (KBr): 3031 (CH, aromatic), 1638
(C¼¼O conjugated), and 1580 (C¼¼C);
1
H NMR (CDCl
3
): d¼
7.44–8.28 (m, 12H, ArH’s), 8.74 (s, 1H, ArH) and 9.40 (s, 1H,
ArH); MS: m/z ¼390 (M
þ
, 43%), 195 (20%), 139 (100%),
and 115 (27%); Anal. Calcd. for C
24
H
14
N
4
O
2
(390.11) C,
73.84; H, 3.61; N, 14.35. Found: C, 73.62; H, 3.37; N,
14.28%.
3-(Naphtho[2,1-b]furan-2-carbonyl)-pyrazolo[5,1-c][1,2,4]tri
azine-8-carbonitrile (6c). Yellow crystals from AcOH, yield
(68%), mp: 224–62C; IR (KBr): 3089 (CH, aromatic), 2228
(CBN) and 1636 (C¼¼O conjugated);
1
H NMR (CDCl
3
): d¼
7.54–8.44 (m, 7H, ArH’s), 8.59 (s, 1H, pyrazole H-3) and 8.72
(s, H, ArH); MS: m/z ¼315 (M
þ
, 91%), 205 (56%), 139
(100%) and 63 (28%); Anal. Calcd. for C
19
H
9
N
5
O
2
(399.31);
C, 67.26; H, 2.67; N, 20.64. Found: C, 64.82; H, 2.49; N,
20.48%.
([1,2,4]Triazolo[3,4-c][1,2,4]triazin-6-yl)(naphtho[2,1-b]furan-
2-yl)methanone (6d). Buff crystals from EtOH, yield (74%),
mp: 219–21C; IR (KBr): 3055 (CH, aromatic) and 1639
(C¼¼O conjugated);
1
H NMR (CDCl
3
): d¼6.85 (s, 1H, furan
H-3), 7.55–8.05 (m, 6H, ArH’s), 8.19 (s, 1H, ArH) and 8.55
(s,1H, 1,2,4-triazine); MS: m/z ¼315 (Mþ, 91.7%), 205
Scheme 4
120 Vol 49A. O. Abdelhamid, S. A. Shokry, and S. M. Tawfiek
Journal of Heterocyclic Chemistry DOI 10.1002/jhet
(56%), 139 (100%), 63 (28.2%); Anal. Calcd. for C
17
H
9
N
5
O
2
(315.29), C, 64.76; H, 2.88; N, 22.21. Found: C, 64.82; H,
3.00; N, 22.12.
Benzo[4,5]imidazo[2,1-c][1,2,4]triazin-3-yl-naphtho[2,1-b]
furan-2-yl-methanone (6e). Brown crystals from AcOH, yield
(68%), mp: 254–56C; IR (KBr): 3128 (CH, aromatic), 1662
(C¼¼O), 1633 (C¼¼N) and 1585 (C¼¼C); MS: m/z ¼363
(Mþ1, 35%), 328 (23%), 195 (58%), 139 (100%) and 92
(29%); Anal. Calcd. for C
22
H
12
N
4
O
2
(364.36) C, 72.52; H,
3.32; N, 15.38. Found: C, 72.33; H, 3.25; N, 15.53%.
7-(Naphtho[1,2-b]furan-2-yl)-2-phenylpyrazolo[1,5-a]pyrim-
idine (13a), 7-(naphtho[1,2-b]furan-2-yl)-3-phenylpyrazolo
[1,5-a]pyrimidine (13b), 7-(naphtho[1,2-b]furan-2-yl)pyrazolo
[1,5-a]pyrimidine-3-carbonitrile (13c), 5-(naphtho[1,2-b]furan-
2-yl)-[1,2,4]triazolo[4,3-a]pyrimidine (13d), Naphtho[1,2-b]furan-
2-yl-benzo[4,5]imidazo[1,2-a]pyrimidine (13e). Method A. A
solution of (0.01 mol) sodium salt of 5-hydroxy-1-naphtho[2,
1-b]furan-2-ylpropenone (2) (1.3 g, 0.01 mol), the appropriate
of amino pyrazoles, aminotriazole or 2-aminobenzimidazole
(0.01 mol), and piperidine acetate (1 mL) in H
2
O (3 mL) was
refluxed for 15 min. Acetic acid (1.5 mL) was added to the
hot solution. The solid product was filtered off and recrystal-
lized from the proper solvent.
Method B. A mixture of the appropriate 10a–e(5 mmole),
3-dimethylamino-1-naphtho[2,1-b]furan-2-ylpropenone (7)(1.32
g, 5 mmole), ammonium acetate (0.37 g, 5 mmole) in acetic
acid (30 mL) was reflux for 4 h. The resulting solid which
formed was collected and recrystallized from acetic acid to give
products identical in all aspects mp., mixed mp. And spectra
with the corresponding obtained in method A.
7-(Naphtho[2,1-b]furan-2-yl)-2-phenylpyrazolo[1,5-a]pyrimi-
dine (13a). Yellow crystals from AcOH, yield (78%), mp:
252–53C; IR (KBr): 3043 (CH, aromatic), 1613 (C¼¼N) and
1586 (C¼¼C);
1
H NMR (CDCl
3
): d¼7.09–8.52 (m, 14H,
ArH’s) and 9.11 (s, 1H, ArH); MS: m/z ¼361 (M
þ
, 84%),
181 (10%), 163 (14%), 77 (100%) and 51 (81%); Anal. Calcd.
for C
24
H
15
N
3
O (361.4) C, 79.76; H, 4.18; N, 11.63. Found: C,
79.72; H, 4.22; N, 11.65%.
7-(Naphtho[2,1-b]furan-2-yl)-3-phenylpyrazolo[1,5-a]pyrimi-
dine (13b). Orange crystals from Dioxan, yield (66%), mp:
252–54C; IR (KBr): 3055 (CH, aromatic), 1614 (C¼¼N) and
1585 (C¼¼C);
1
H NMR (dimethyl sulfoxide [DMSO]-d
6
): d¼
7.50–8.27 (m, 14H, ArH’s) and 9.17 (s, 1H, ArH); MS: m/z ¼
361 (M
þ
, 84.5%), 332 (5.2%), 181 (10.2%), 163 (14.5%), 77
(100%), 51 (81.4.2%); Anal. Calcd. for C
24
H
15
N
3
O (361.4) C,
79.76; H, 4.18; N, 11.63. Found: C, 79.61; H, 4.11; N, 11.39%.
7-(Naphtho[2,1-b]furan-2-yl)pyrazolo[1,5-a]pyrimidine-3-car
bonitrile (13c). Orange crystals from Dioxan, yield (54%), mp:
264–66C; IR (KBr): 3049 (CH, aromatic), 2233 (CN), 1612
(C¼¼N);
1
H NMR (CDCl
3
): d¼6.95 (s, 1H, Pyrazole H-5),
7.35 (s, 1H, furan H-3), 7.58–8.05 (m, 7H, ArH’s, pyrimidine
H-5), 9.48 (d, 1H, J¼8 Hz, pyrimidine H-4), 9.04 (s, 1H,
pyrazole H-5); MS: m/z ¼310 (Mþ, 100.5%), 155 (37.5%),
141 (56.3%), 74 (50%), 63 (62.5%); Anal. Calcd. for
C
19
H
10
N
4
O (310.31) C, 73.54; H, 3.25; N, 18.06. Found: C,
73.27; H, 3.34; N, 18.24%.
7-(Naphtho[2,l-b]furan-2-yl)-[l,2,4]triazolo[4,3-a]pyrimidine
(13d). Yellow crystals from AcOH, yield (75%), mp: 255–
57C; IR (KBr): 055 (CH, aromatic), 1614 (C¼¼N), and 1584
(C¼¼C);
1
H NMR (CDCl
3
): d¼7.56–8.27 (m, 7H, ArH’s),
8.67 ( s, 1H, triazole H-2), 8.58 (d, 1H, pyrimidine H-4) and
9.00 (d, 1H, pyrimidine H-5); MS: m/z ¼286 (M
þ
, 100%),
163 (25%), 129 (26%), 88 (36%) and 53 (67%); Anal. Calcd.
for C
17
H
10
N
4
O (286.29) C, 71.32; H, 3.52; N, 19.75. Found:
C, 70.90; H, 3.71; N, 19.92%.
4-Naphtho[2,1-b]furan-2-yl-benzo[4,5]imidazo[1,2-a]pyrimi-
dine (13e). Yellow crystals from dioxan, yield (79%), mp:
239–41C; IR (KBr): 3051 (CH, aromatic), 1634 (C¼¼N), and
1586 (C¼¼C);
1
H NMR (CDCl
3
): d¼7.52–8.58 (m, 12H,
ArH’s) and 951 (d, 1H, pyrimidine H-4); Anal. Calcd. for
C
22
H
13
N
3
O (335.36) C, 78;79 H, 3.91; N, 12.53. Found: C,
78.59; H, 4.20; N, 12.34%.
1-(2-Methyl-6-(naphtho[2,1-b]furan-2-yl)pyridin-3-yl)etha-
none (19), ethyl 2-methyl-6-(naphtho[2,1-b]furan-2-yl)pyri-
dine-3-carboxylate (20) and 6-(2-amino-6-(naphtho[1,
2-b]furan-2-yl)pyridin-3-yl)(phenyl)methanone (22). A mix-
ture of the appropriate of acetylacetone, ethyl acetoacetate, or
benzoylacetonitrile (5 mmole), 3-dimethylamino-1-naph-
tho[2,1-b]furan-2-ylpropenone (7) (1.32 g, 5 mmole), ammo-
nium acetate (0.37 g, 5 mmole) in acetic acid (30 mL) was
reflux for 4 h. The resulting solid which formed was collected
and recrystallized from ethanol to give 19,20, and 22.
1-(2-Methyl-6-(naphtho[2,1-b]furan-2-yl)pyridin-3-yl)ethanone
(19). Brown crystals from diluted AcOH, yield (54%), mp:
177–78C; IR (KBr): 3051 (CH, aromatic), 1682 (C¼¼O conju-
gated), 1636 (C¼¼N), and 1594 (C¼¼C);
1
H NMR (CDCl
3
): d
¼2.64 (s, 3H, CH
3
), 2.89 (s, 3H, CH
3
), and 7.27–8.26 (m,
9H, ArH’s); MS: m/z ¼301 (M
þ
, 100%), 286 (53%), 258
(16%), 240 (19%), 202 (22%), 163 (16%); Anal. Calcd. for
C
20
H
15
NO
2
(301.34) C, 79.72; H, 5.02; N, 4.65. Found: C,
79.63; H, 4.91; N, 4.41%.
Ethyl 2-methyl-5-(naphtho[1,2-b]furan-2-yl)pyridine-3-car-
boxylate (20). Brown crystals from diluted AcOH, yield
(68%), mp: 141–42C; IR (KBr): 3051 (CH, aromatic), 1716
(C¼¼O), 1640 (C¼¼N) and 1580 (C¼¼C);
1
H NMR (CDCl
3
): d
¼1.42 (t, 3H, ACH
2
CH
3
), 2.97 (s, 3H, pyridine CH
3
), 4.39
(q, 2H, ACH
2
CH
3
) and 7.27–8.34 (m, 9H, ArH’s); MS: m/z ¼
331 (M
þ
, 100%), 303 (68%), 139 (20%), 88 (22%) and 63
(20%); Anal. Calcd. for C
21
H
17
NO
3
(331.36) C, 76.12; H,
5.17; N, 4.23. Found: C, 76.27; H, 5.24; N, 4.18%.
(2-Amino-6-(naphtho[1,2-b]furan-2-yl)pyridin-3-yl)(phenyl)
methanone (22). Yellow crystals (diluted acetic acid), mp:
234–36C;
1
H NMR (CDCl
3
): d¼7.29–8.25 (m, 15H, ArH’s)
and 9.49 (s, 1H, pyridine H-6); IR (KBr), (cm
1
)¼3483 and
3342 (NH
2
), 3051 (CH, aromatic), 1664 (C¼¼O amide), and
1585 (C¼¼C); MS, m/z (%) ¼364 (M
þ
, 57%), 205 (16%), 139
(13%), and 77 (100%); Anal. Calcd. For C
24
H
16
N
2
O
2
requires
(364.4): C, 79.11; H, 4.43; N, 7.69. Found: C, 79.33; H, 4.21;
N, 7.75%.
2-Methyl-6-(naphtho[2,1-b]furan-2-yl)pyridine-3-carbohydra-
zide (23). Equimolar amounts of ethyl 2-methyl-6-naphtho[1,2-
b]furan-2-ylpyridine-3-carboxylate (20) and hydrazine hydrate
(5 mmol for each) in ethanol (10 mL) were refluxed for 5 h.
The resulting solid, was cooled and recrystallized to give 23,
as pale yellow crystals (diluted acetic acid), mp: 258–60C; IR
(KBr), (cm
1
)¼3289 and 3215 (NH
2
amide), 1679 (C¼¼O
amide), 1637 (C¼¼N), and 1596 (C¼¼C); MS, m/z (%) ¼317
(M
þ
, 36%), 286 (100%), 258 (14.6%), 101 (5.8%); Anal.
Calcd. For C
19
H
15
N
3
O
2
requires (317.34): C, 71.91; H, 4.76;
N, 13.24. Found: C, 72.07; H, 4.80; N, 13.83%.
Azido(2-methyl-6-(naphtho[2,1-b]furan-2-yl)pyridin-3-yl)me-
thanone (24). To a stirred solution of 2-methyl-5-(naphtho[l,
January 2012 121A New Approach for the Synthesis of Some Pyrazolo[5,1-c]Triazines and
Pyrazolo[1,5-a]pyrimidines Containing Naphtofuran Moiety
Journal of Heterocyclic Chemistry DOI 10.1002/jhet
2-b]furan-2-yl)pyridine-3-carbohydrazide (21)(5 mmole) in
acetic acid (15 mL) at 0–5C, sodium nitrite was added por-
tion-wise tell effervescence ended. The reaction mixture stirred
for 1 h. The resulting solid, was collected, filtered, washed
with water, and recrystallized from acetic acid to give the cor-
responding 22, as buff crystals, mp: 137–38 C;
1
H NMR
(CDCl
3
): d¼2.97 (s, 3H, pyridine CH
3
) and 7.56–8.26 (m,
9H, ArH’s); IR (KBr), (cm
1
)¼2136 (azide), 1689 (C¼¼O),
1636 (C¼¼N), and 1595 (C¼¼C); MS, m/z (%) ¼314 (0.1%),
300 (100%), 150 (12.5%), and 88 (16.7%); Anal. Calcd. For
C
19
H
12
N
4
O
2
requires (328.32): C, 69.51; H, 3.68; N, 17.06.
Found: C, 69.57; H, 3.96; N, 17.22%.
(3,5-Dimethyl-1H-pyrazol-1-yl)(2-methyl-6-(naphtho[2,1-b]
furan-2-yl)pyridin-3-yl)methanone (25) and (3-methyl-lH-
pyrazol-5-one-1-yl)(2-methyl-5-(naphtho[1,2-b]furan-2-yl)pyr-
idin-3-yl)methanone (26). General procedure. Equimolar
amounts of 2-methyl-5-(naphtho[l,2-b]furan-2-yl)pyridine-3-
carbohydrazide (23) and acetyl acetone or ethyl acetoacetate
(4 mmol for each) in ethanol (10 mL) with two drops of acetic
acid were refluxed for 4 h. The resulting solid, so formed, was
cooled and recrystallized from diluted acetic acid to give the
corresponding 25 and 26, respectively.
(3,5-Dimethyl-1H-pyrazol-l-yl)(2-methyl-5-(naphtho[l,2-b]
furan-2-yl)pyridin-3-yl)methanone (25). This compound was
obtained as pale yellow crystals (diluted acetic acid), mp:
213–15 C;
1
H NMR (CDCl
3
): d¼0.88 (s, 3H, pyrazole
CH
3
), 1.83 (s, 3H, pyrazole CH
3
), 2.29 (s, 3H, pyridine CH
3
),
5.71 (s,1H, pyrazole H-4), 6.88 (s, 1H, furan H-3), and 7.40–
8.17 (m, 8H, ArH’s); IR (KBr), (cm
1
)¼3051 (CH, aro-
matic), 1698 (C¼¼O), 1630 (C¼¼N), and 1595 (C¼¼C); MS, m/z
(%) ¼381 (M
þ
, 73%), 286 (100%), 258 (17%), and 139
(7%); Anal. Calcd. For C
24
H
19
N
3
O
2
requires (381,43): C,
75.57; H, 5.02; N, 11.02. Found: C, 75.60; H, 5.15; N,
10.96%.
(3-Methyl-lH-pyrazol-5-one-1-yl)(2-methyl-5-(naphtho[1,2-b]
furan-2-yl)pyridin-3-yl)methanone (26). This compound was
obtained as yellow crystals (diluted acetic acid), mp: 143–45
C;
1
H NMR (CDCl
3
): d¼0.90 (s, 3H, pyrazolin Me), 1.68
(s, 2H, methylene), 2.31 (s, 3H, pyridine Me), 6.89 (s, 1H,
furan H-3), and 7.42–8.54 (m, 8H, ArH’s); IR (KBr), (cm
1
)
¼3054 (CH, aromatic), 1722 (C¼¼O), 1663 (CO, pyrazol-3-
one), and 1581 (C¼¼C); Anal. Calcd. For C
23
H
17
N
3
O
3
requires
(383.4): C, 72.05; H, 4.47; N, 10.96. Found: C, 71.96; H,
4.31; N, 11.17%.
3-Methyl-1-[(2-methyl-6-naphtho[1,2-d]furan-2-yl(3-pyridyl))
carbonyl]-4-{[(4-methylphenyl)amino]azamethylene}-1,2-diaz-
olin-5-one (27). Method A. p-tolyldiazonium chloride (5
mmole), which is prepared via reaction of p-toluidine (0.5 gm,
5 mmole), hydrochloric acid (3 mL, 6 M), and sodium nitrite
(0.37 gm, 5 mmole) at 0–5C, was added to a mixture of 25
(2.51 gm, 5 mmole) and sodium acetate (0.41 gm, 5 mmole)
in ethanol (30 mL) at 0–5C, while stirring. The reaction mix-
ture was stirred for 3 h. The resulting solid, was collected,
washed with water and recrystallized from acetic acid to give
27.
Method B. A mixture of 23 and ethyl 2-p-tolylazo-3-oxo-4-
butanoate (5 mmol for each) in ethanol (20 mL) and catalytic
amount of acetic acid (2 drops) was refluxed for 3 h. The
resulting solid, so formed, was collected and recrystallized
from acetic acid to give product identical in all aspects with
27.
This compound was obtained as brown crystals (acetic
acid), mp: 134–36C;
1
H NMR (CDCl
3
): d¼0.88 (s, 3H, pyr-
azoline CH
3
), 1.99 (s, 3H, p-CH
3
), 2.37 (s, 3H, pyridine Me),
6.87 (s, 1H, furan H-3), 7.15–7.86 (m, 12H, ArH’s) and 12.89
(s, 1H, NH); IR (KBr): 3039 (CH, aromatic), 1729 (C¼¼O),
1663 (C¼¼O), 1635 (C¼¼N) and 1581 (C¼¼C); MS, m/z (%) ¼
501 (M
þ
, 25.5%), 286 (100%), 258 (11.8%), and 106 (6%);
Anal. Calcd. For C
30
H
23
N
5
O
3
requires (501.54): C, 71.84; H,
4.62; N, 13.96. Found: C, 71.43; H, 4.43; N, 13.46%.
2-(2-Phenylhydrazono)-3-(naphtho[l,2-b]furan-2-yl)-3-oxo-
propanal (28a), 3-(naphtho[2,1-b]furan-2-yl)-3-oxo-2-(2-p-
tolylhydrazono)propanal (28b) and 3-(naphtho[2,1-b]furan-
2-yl)-2-(2-(4-nitrophenyl)hydrazono)-3-oxopropanal (28c). A
solution of the appropriate arendiazonium chloride (5 mmole)
was added to a mixture of 3-dimethylamino-1-naphtho[2,1-
b]furan-2-ylpropenone (7) (1.32 g, 5 mmole), sodium acetate
(0.65 g, 5 mmole) in ethanol (30 mL) at 0–5C while stirring.
The resulting solid which formed after 3 h was collected,
washed with water and recrystallized to give 28a-c.
3-(Naphtho[2,1-b]furan-2-yl)-3-oxo-2-(2-phenylhydrazono)-
propanal (28a). This compound was obtained as brown crys-
tals (acetic acid), yield (81%), mp: 134–36C; IR (KBr): 3089
(CH, aromatic), 1645 (C¼¼O conjugated), 1622 (C¼¼N), and
1583 (C¼¼C);
1
H NMR (CDCl
3
): d¼7.28–7.93 (m, 12H,
ArH’s), 9.98 (s, 1H, ACHO) and 14.39 (s, br., 1H, NH); MS,
m/z (%) ¼342 (M
þ
, 16%), 258 (35%), 222 (80%), 139
(100%), and 77 (55%); Anal. Calcd. For C
21
H
14
N
2
O
3
requires
(342.35): C, 73.68; H, 4.12; N, 8.18. Found: C, 73.49; H,
3.99; N, 7.92%.
3-(Naphtho[2,1-b]furan-2-yl)-3-oxo-2-(2-p-tolylhydrazono)-
propanal (28b). This compound was obtained as yellow crys-
tals (ethanol), yield (83%), mp: 190–91C; IR (KBr): 3056
(CH, aromatic), 1640 (C¼¼O conjugated), 1616 (C¼¼N), and
1586 (C¼¼C);
1
H NMR (CDCl
3
): d¼2.42 (s, 3H, CH
3
), 7.28–
7.89 (m, 11H, ArH’s), 8.29 (s, 1H, ACHO) and 10.19 (s, 1H,
NH); MS, m/z (%) ¼356 (M
þ
,15%), 272 (19%), 222 (50%),
139 (100%), and 77 (56%); Anal. Calcd. For C
22
H
16
N
2
O
3
requires (356.37): C, 74.15; H, 4.53; N, 7.86. Found C, 74.53;
H, 4.85; N, 7.79%.
3-(Naphtho[2,1-b]furan-2-yl)-2-(2-(4-nitrophenyl)hydrazono)-
3-oxopropanal (28c). This compound was obtained as red crys-
tals (acetic acid), yield (78%), mp: 250–52C; IR (KBr): 3113
(CH, aromatic), 1650 (C¼¼O conjugated), 1618 (C¼¼N), and
1596 (C¼¼C);
1
H NMR (DMSO-d
6
): d¼7.67–8.75 (m, 11H,
ArH’s), 9.77 ( s, 1H, ACHO), and 10.07 (s, 1H, NH); MS, m/z
(%) ¼387 (M
þ
, 10%), 303 (21%), 222 (90%), 139 (100%),
and 107 (16%) Anal. Calcd. For C
21
H
13
N
3
O
5
requires
(387.35): C, 65.12; H, 3.38; N, 10.85. Found C, 64.81; H,
3.11; N, 11.12%.
1-(3-(Naphtho[2,1-b]furan-2-yl)-1H-pyrazol-4-yl)-2-phenyl-
diazene 29a–i. A mixture of the appropriate 28a–c(5 mmole)
and the appropriate the appropriate of hydrazine, p-nitrophe-
nylhydrazine or 2,4-dinitrophenylhydrazine (5 mmole) (5
mmole) in ethanol (15 mL) was refluxed for 2 h. The resulting
solid was collected and recrystallized to give 29a–i.
Alternative method. A solution of the appropriate arendia-
zonium chloride (5 mmole) was added to a mixture of the
appropriate 30a,b (5 mmole), sodium acetate (0.65 g, 5
mmole) in ethanol (30 mL) at 0–5C while stirring. The result-
ing solid which formed after 3 h was collected, washed with
water and recrystallized from acetic acid to give identical in
122 Vol 49A. O. Abdelhamid, S. A. Shokry, and S. M. Tawfiek
Journal of Heterocyclic Chemistry DOI 10.1002/jhet
all aspects mp: mixed mp., and spectra with the corresponding
obtained 29a–i.
3-(Naphtho[2,1-b]furan-2-yl)-4-phenyazo-1H-pyrazole (29a).
This compound was obtained as brown crystals (acetic acid),
yield (76%), mp: 309–10C; IR (KBr): 3210 (NH ), 3045 (CH,
aromatic), 1613 (C¼¼N), and 1594 (C¼¼C);
1
H NMR CDCl
3
):
d¼7.41–8.43 (m, 13H, ArH’s) and 13.44 (s, 1H, NH); IR
(KBr), (cm
1
)¼3210 (NH); MS: m/z ¼338 (Mþ, 10.5%),
206 (23.7%), 139 (0.9%), 77 (100%); Anal. Calcd. for
C
21
H
14
N
4
O (338.36) C, 74.54; H, 4.17; N, 16.56. Found: C,
74.42; H, 4.21; N, 16.42.
3-(Naphtho[2,1-b]furan-2-yl)-1-(4-nitrophenyl)-4-(phenyldia-
zenyl)-1H-pyrazole (29b). This compound was obtained as red
crystals (acetic acid) mp: 246–48C; yield (93%),
1
H NMR
(DMSO-d
6
): d¼7.32–9.05 (m, 17H, ArH’s); IR (KBr): 3085
(CH, aromatic), 1614 (C¼¼N), 1589 (C¼¼C) and 1538 & 1319
(NO
2
); Anal. Calcd. For C
27
H
17
N
5
O
3
requires (459.46): C,
70.58; H, 3.73; N, 15.24. Found: C, 70.78; H, 3.58; N,
15.40%.
1-(2,4-Dinitrophenyl)-3-(naphtho[2,1-b]furan-2-yl)-4-(phenyl-
diazenyl)-1H-pyrazole (29c). This compound was obtained as
red crystals (acetic acid), yield (75%), mp: 246–47C; IR
(KBr): 3092 (CH, aromatic), 1625 (C¼¼N), 1602 (C¼¼C), and
1545 & 1322 (NO
2
); MS, m/z (%) ¼506 (Mþ2, 3.7%), 339
(53.5%), 195 (51.5%), 139 (99.5%) and 77 (100%); Anal.
Calcd. For C
27
H
16
N
6
O
5
requires (504.45): C, 64.29; H, 3.20;
N, 16.66. Found: C, 64.00; H, 3.30; N, 16.42%.
3-(Naphtho[2,1-b]furan-2-yl)-4-(4-methylphenyl)azo-1H-pyr-
azole (29d). Red crystals from AcOH, yield (75%), mp: 246–
48C; IR (KBr): 3045 (CH, aromatic), 1627 (C¼¼N), 1514,
1319 (NO
2
);
1
H NMR CDCl
3
): d¼6.98 (s, 1H, furan H-3),
7.39–8.06 (m, 13H, ArH’s, and pyrazole H-5), 8.89 (d, 2H, J¼
12Hz, ArH’s); MS: m/z ¼459 (Mþ, 10.5%), 206 (23.7%), 139
(0.9%), 77 (100%); Anal. Calcd. for C
27
H
16
NO (352.39) C,
74.98; H, 4.58; N, 15.90. Found: C, 75.12; H, 4.71; N, 15.84.
3-(Naphtho[2,1-b]furan-2-yl)-1-(4-nitrophenyl)-4-(p-tolyldia-
zenyl)-1H-pyrazole (29e). This compound was obtained as red
crystals (acetic acid), yield (75%), mp: 212–14C; IR (KBr):
3089 (CH, aromatic), 1614 (C¼¼N), 1596 (C¼¼C), and 1537 &
1332 (NO
2
); MS, m/z (%) ¼473 (M
þ
, 0.7%), 353 (62.8%),
195 (72.5%), 139 (100%), and 91 (90.8%); Anal. Calcd. For
C
28
H
19
N
5
O
3
requires (473.48): C, 71.03; H, 4.04; N, 14.79.
Found: C, 70.81; H, 4.01; N, 14.63%.
1-(2,4-Dinitrophenyl)-3-(naphtho[2,1-b]furan-2-yl)-4-(p-tolyl-
diazenyl)-1H-pyrazole (29f). This compound was obtained as
red crystals (acetic acid), yield (75%), mp: 298–301C; IR
(KBr): 3103 (CH, aromatic), 1617 (C¼¼N), 1594 (C¼¼C) and
1540, 1321 (NO
2
); MS, m/z (%) ¼550 (Mþ1, 5.6%), 384
(68.9%), 303(13.3%), 195 (45.9%), 139 (100%), 107 (28.6%),
and 63 (87.2%); Anal. Calcd. For C
28
H
18
N
6
O
5
requires
(518.48): C, 64.86; H, 3.50; N, 16.21. Found: C, 64.93; H,
3.70; N, 16.44%.
1-(3-(Naphtho[2,1-b]furan-2-yl)-1H-pyrazol-4-yl)-2-(4-nitro-
phenyl)diazene (29g). This compound was obtained as red
crystals (acetic acid), yield (75%), mp: 352–55C; IR (KBr):
3087 (CH, aromatic), 1628 (C¼¼N) and 1599 (C¼¼C);
1
H NMR
(DMSO-d
6
): d¼7.46–8.53 (m, 12H, ArH’s) and 13.85 (s, 1H,
NH); MS, m/z (%) ¼383 (M
þ
, 73.6%), 261 (22.9%), 206
(100%), 139 (34.7%) and 88 (22.6%); Anal. Calcd. For
C
27
H
13
N
3
O
3
requires (383.36): C, 70.98; H, 3.69; N, 11.83.
Found: C, 71.22; H, 3.32; N, 11.79%.
3-(Naphtho[2,1-b]furan-2-yl)-4-(2-(4-nitrophenyl)hydrazono)-
4H-pyrazole (29h). This compound was obtained as red crys-
tals (acetic acid), yield (75%), mp: 274–76C; IR (KBr): 3087
(CH, aromatic), 1618 (C¼¼N), 1595 (C¼¼C), and 1541, 1339
(NO
2
);
1
H NMR (DMSO-d
6
): d¼7.60–8.98 (m, ArH’s);
Anal. Calcd. For C
27
H
16
N
6
O
5
requires (504.45): C, 64.29; H,
3.20; N, 16.66. Found: C, 63.97; H, 3.35; N, 16.99%.
1-(2,4-Dinitrophenyl)-3-(naphtho[2,1-b]furan-2-yl)-4-((4-nitro-
phenyl)diazenyl)-1H-pyrazole (29i). This compound was
obtained as red crystals (acetic acid), yield (75%), mp: 298–
301C; IR (KBr): 3098 (CH, aromatic), 1617 (C¼¼N), 1594
(C¼¼C), and 1540, 1321 (NO
2
); MS, m/z (%) ¼550 (M
þ1
,
5.6%), 384 (68.9%), 303(13.3%), 195 (45.9%), 139 (100%),
107 (28.6%), and 63 (87.2%); Anal. Calcd. For C
27
H
15
N
7
O
7
requires (549.45): C, 59.02; H, 2.75; N, 17.84. Found: C,
58.93; H, 2.70; N, 17.64%.
3-(Naphtho[l,2-b]furan-2-yl)-1H-pyrazole (30a) and 3-(naph-
tho[2,1-b]furan-2-yl)-1-(4-nitrophenyl)-1H-pyrazole (30b). A
mixture of 3-dimethylamino-1-naphtho[2,1-b]furan-2-ylprope-
none (7) (1.32 g, 5 mmole) and the appropriate of hydrazine
or p-nitrophenylhydrazine (5 mmole) in ethanol (15 mL) was
refluxed for 2 h. The resulting solid was collected and recrys-
tallized from ethanol to give 30a,b.
3-(Naphtho[l,2-b]furan-2-yl)-1H-pyrazole (30a). This com-
pound was obtained as buff crystals (ethanol) mp: 183–84C;
yield (81%), IR (KBr): 3123 (NH), 3050 (CH, aromatic), 1627
(C¼¼N) and 1583 (C¼¼C);
1
H NMR (CDCl
3
): d¼6.81 (d, 1H,
pyrazole H-4), 7.46–8.17 (m, 8H, ArH’s), and 10.38 (s, 1H,
NH); Anal. Calcd. For C
15
H
10
N
2
O requires (234,25): C, 76.91;
H, 4.30; N, 11.96. Found: C, 77.15; H, 4.47; N, 11.68%.
3-(Naphtho[2,1-b]furan-2-yl)-1-(4-nitrophenyl)-1H-pyrazole
(30b). This compound was obtained as yellow crystals (etha-
nol), yield (76%), mp:190–91C; IR (KBr): 3089 (CH, aro-
matic), 1615 (C¼¼N), 1587 (C¼¼C), and 1539 & 1332 (NO
2
);
1
H NMR (CDCl
3
): d¼5.95 (d, 1H, pyrazole H-4) and 7.48–
8.19 (m, 12H, ArH’s, furan H-3 and pyrazole H-5); Anal.
Calcd. For C
21
H
13
N
3
O
3
requires (355.35): C, 70.98; H, 3.69;
N, 11.83. Found: C, 70.63; H, 3.85; N, 11.79%.
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January 2012 123A New Approach for the Synthesis of Some Pyrazolo[5,1-c]Triazines and
Pyrazolo[1,5-a]pyrimidines Containing Naphtofuran Moiety
Journal of Heterocyclic Chemistry DOI 10.1002/jhet
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