Synthesis of New Heterocycles from Reactions of 1-Phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonyl Azides

Article abstract of DOI:10.1002/jhet.3511

Two individual examples of pyrazolo[3,4-b]pyridine-5-carbonyl azides and hydrazides were reacted with various nucleophilic reagents. Different unexpected behaviors was observed. NMR, IR, mass spectra together with elemental analyses and X-ray structure analyses, were used to prove the structure of the obtained products.

Full text of DOI:10.1002/jhet.3511

Month 2019
Ashraf A. Aly,
Synthesis of New Heterocycles from Reactions of 1-Phenyl-1H-
pyrazolo[3,4-b]pyridine-5-carbonyl Azides
a
Talaat I. El-Emary,b Aboul-Fetouh E. Mourad,a Zainab Khallaf Alyan,a Stefan Bräse,c and
Martin Niegerd
*
aDepartment of Chemistry, Faculty of Science, Minia University, El Minia, 61519, Egypt
bDepartment of Chemistry, Faculty of Science, Assiut University, Assiut, Egypt
cInstitute of Organic Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 6, Karlsruhe 76131, Germany
dDepartment of Chemistry, University of Helsinki, P.O. Box 55, Helsinki 00014, Finland
*E-mail: ashrafaly63@yahoo.com
Received October 9, 2018
DOI 10.1002/jhet.3511
Published online 00 Month 2019 in Wiley Online Library (wileyonlinelibrary.com).
Two individual examples of pyrazolo[3,4-b]pyridine-5-carbonyl azides and hydrazides were reacted with
various nucleophilic reagents. Different unexpected behaviors was observed. NMR, IR, mass spectra to-
gether with elemental analyses and X-ray structure analyses, were used to prove the structure of the obtained
products.
J. Heterocyclic Chem., 00, 00 (2019).
INTRODUCTION
pyrazolo[3,4-b]pyridines [16–21], we aim in this work
to synthesize fused heterocyclic systems containing
pyrazolo[3,4-b]pyridine.
Among the various heterocyclic systems developed
over the last centuries, nitrogen-containing heterocyclic
compounds play a crucial role in the context of both
chemistry and biology. Pyrazolo[3,4-b]pyridines belong to
this important class of heterocyclic due to their relevance
in medicinal chemistry [1,2] displayed by the diverse
range of biological and pharmaceutical activities such as
antitumor [3,4], antibacterial [5–7], anti-inflammatory [8],
inhibitors of protein kinase [9], cyclin-dependent kinase 1
[10], glycogen synthase kinase-3 [11], and human
immunodeficiency virus reverse transcriptase [12]. As an
example, a rapid and convenient, environmentally benign
synthesis of spiro-pyrazolo[3,4-b]pyridine derivatives was
developed using a three-component coupling of isatin,
cyclic-1,3-dione, and pyrazol-5-amine in aqueous ethanol
using aluminosilicate nanoparticles as catalyst [13].
Previously, we also prepared various fused pyridine
derivatives via the reaction of 2,4(1H,3H)-quinolinediones
with diethyl acetylenedicarboxylate. This reaction furnished
ethyl 5,6-dihydro-2,5-dioxo-2H-pyrano[3,2-c]quinoline-4-
carboxylates while 2,4(1H,3H)-quinolinediones afforded
dialkyl 2(4-oxo-1,4-dihydroquinolin-3-yl)fumarates in good
yields [14]. Quinoline-2,4-diones were reacted with 2-(2-
oxo-1,2-dihydroindol-3-ylidene)-malononitrile in pyridine
to yield 20-amino-2,50-dioxo-50,60-dihydrospiro (indoline-
3,40-pyrano[3,2-c]quinoline)-30-carbonitriles in good to
excellent yields [15]. In continuation of our work on
RESULTS AND DISCUSSION
The pyrazolo[3,4-b]pyridines 5 and 8 were prepared by the
following sequences: The available 5-aminopyrazole 1 was
formulated by the procedure described Häufel et al. [22] to
give compound 2 (Scheme 1). The spectral data of 2 were
reported earlier [23]. Synthesis of pyrazolo[3,4-b]pyridine-
5-carboxylate (3) [23] was also achieved by its reaction
with diethyl malonate in glacial acetic acid (Scheme 1).
The reaction of 3 with hydrazine hydrate produced the
new compound 4 (Scheme 1). The elemental analysis and
mass spectrum of 4 proved its molecular formula as
1
C14H13N5O2. The H NMR spectrum of 4 showed the
NH2, NH, and CH-pyridine protons at δ = 6.50, 9.40, and
8.10 ppm, respectively. In 13C NMR spectrum of 4, the
carbonyl-carbons appeared δ = 165.0 and 164.2 ppm,
respectively. Reaction of 4 with HNO2 produced the
corresponding 3-methyl-6-oxo-1-phenyl-6,7-dihydro-1H-
pyrazolo[3,4-b]pyridine-5-carbonyl azide (5) (Scheme 1).
Analogously, the new compound 8 was established via the
reaction of 2 with ethyl acetoacetate to give compound 6
[22] in 92% yield (Scheme 1). The elemental analysis and
mass spectrum of compound 6 corroborated its gross
molecular formula as C17H17N3O2. The ester protons of 6
© 2019 Wiley Periodicals, Inc.

A. A. Aly, T. I. El-Emary, A.-F. E. Mourad, Z. K. Alyan, S. Bräse, and M. Nieger
Vol 000
Scheme 1. Strategy of the synthesis of pyrazolo[3,4-b]pyridines 5 and 8.
appeared in the 1H NMR as a triplet (3H) and quartet (CH2)
at δ = 1.50 and 4.30 ppm, respectively. The carbonyl ester
group resonated in the 13C NMR of 6 at δ = 165.0,
whereas the three methyl carbon signals were resonated in
the 13C NMR of 6 at δ = 12.4, 14.3, and 20.1 ppm for the
methyl-ester, methyl-pyrazole, and methyl-pyridine
carbon signals, respectively.
On subjecting compound 6 to the reaction with
hydrazine hydrate, compound 7 was obtained in 80% yield
(Scheme 1). The mass spectrum and elemental analysis
of 7 indicated its molecular formula as C15H15N5O,
which is supported by the disappearance of ester carbon
signals, and the appearance of the NH and NH2 in the IR
and 1H NMR spectra was a further support of its structure.
When compound 7 was reacted with nitrous acid, the
target azide 8 was obtained in a good yield (Scheme 1). IR
spectra of both carbonyl azides of pyrazolo[3,4-b]
pyridines 5 and 8 showed resonances at ν = 2147 and
2140 cmꢀ1, respectively, which are characteristic for
CON3 groups. Besides, the disappearance of the bands
characteristic for NH and NH2 groups (see Experimental
section) was observed.
Elemental analysis and mass spectrum proved the
molecular formula of 9 as C14H10N4O2. The H NMR
1
spectrum of 9 showed two singlets: one for NH at
δ = 12.10 and the other for CH-4 at δ = 7.90. Figure 1
shows distinctive carbon atoms of compound 9. 13C
NMR reveals the carbonyl carbon signal (C-6) at
δ = 165.0, whereas CH-pyridine and methyl carbon
signal were absorbed at δ = 132.0 (CH-4) and 12.4 (C-a),
respectively (for detailed spectral data, see Experimental
section). The structure of 9 was confirmed by X-ray
structure analysis as shown in Figure 2. The mechanism
that describes the formation of 9 was based upon
elimination of N2 molecule to give intermediate 10,
which was followed by Curtius rearrangement to give the
isocyanate 11 (Scheme 2). Nucleophilic addition of the
oxygen lone pair of the carbonyl group would form
compound 9 (Scheme 2).
In a different manner, reaction of 8 with CH3OH gave
pyrazolo[3,4-b]pyridine-5-yl carbamate (12) in 80% yield
(Scheme 3). The structure of 12 was confirmed by
elemental and spectral data. The IR spectrum showed
absorption band at v = 1684 cmꢀ1 for the carbonyl-ester.
Elemental analysis and mass spectrum proved the
molecular formula of 12 as C16H16N4O2. The methyl
Surprisingly, refluxing 5 with methanol for 2 h, a
new compound, namely, 9, was obtained (Scheme 2).
1
protons of ester group appeared in the H NMR of 12 as
a singlet at δ = 3.40 ppm, whereas the carbonyl of the
ester group appeared in the 13C NMR spectrum at
δ = 162.0 ppm. On reacting compound 8 with hydrazine
hydrate in refluxing xylene, the reaction produced
compound 13 (Scheme 3). The same compound 13 was
Scheme 2. Suggested mechanism describes the formation of 9. [Color
figure can be viewed at wileyonlinelibrary.com]
Figure 1. Distinctive carbon atoms of compound 9.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2019
Synthesis of New Heterocycles from Reactions of 1-Phenyl-1H-pyrazolo[3,4-b]
pyridine-5-carbonyl Azides
Figure 2. Molecular structure of one of the independent molecules of 3-methyl-1-phenyl-1,5-dihydro-6H-oxazolo[5,4-b]pyrazolo[4,3-e]pyridin-6-one
(9). Displacement parameters are drawn at 50% probability level).
Scheme 3. Reactions of pyrazolo[3,4-b]pyridine 8 with various reagents.
obtained during reaction of 12 with hydrazine hydrate. The
1H NMR spectrum of 13 revealed the two NH protons at
δ = 9.10 and 8.20 ppm. The NH2-hydrazine protons
appeared together with the aromatic protons at δ = 7.24–
7.18 ppm. The two methyl protons appeared at δ = 2.75
and 2.50 ppm. Reaction of 8 with acetylacetone yielded
2-acetyl-N-(3,6-dimethyl-1-phenyl-1H-pyrazolo[3,4-b]
pyridin-5-yl)-3-oxobutanamide (14). The elemental
analysis and mass spectrum of 14 indicated a molecular
of amide carbon appeared at δ = 163.0 ppm. Besides, the
aliphatic-CH carbon resonates at δ = 96.0 ppm. On the
other site, reaction of carboazide 8 with pyrazolone in
boiling xylene gave the pyrazole-4-carboxamide 15
(Scheme 3). Compound 15 was verified by its IR, MS,
1H NMR, 13C NMR spectra, and elemental analysis.
Thus, the IR spectrum showed absorption bands at
δ = 3282 cmꢀ1 for NH, 2919 cmꢀ1 CH aliphatic, and
1685–1680 cmꢀ1 for CO groups, respectively. The 1H
NMR spectrum showed three signals at δ = 2.20, 2.60,
and 3.40 ppm characteristic for CH3 pyrazole (A), CH3
pyrazolone (B), and CH3 pyridine (C). The (CH3)C═N
carbon signal resonated in the 13C NMR spectrum of 15
at δ = 155.2, whereas the carbonyl carbon signal of
1
formula as C20H20N4O3. The H NMR of compound 14
revealed the CH-proton at δ = 4.40 ppm, whereas the two
acetyl protons appeared as one singlet for 6H at
δ = 2.25 ppm. In 13C NMR spectrum, the carbonyl of the
acetyl group appeared at δ = 209.0, whereas the carbonyl
Journal of Heterocyclic Chemistry
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A. A. Aly, T. I. El-Emary, A.-F. E. Mourad, Z. K. Alyan, S. Bräse, and M. Nieger
Vol 000
Figure 3. Distinctive protons and carbons of tautomerism forms of 15 and 150.
pyrazolone at δ = 164.0 ppm (see Experimental section).
The tautomerism of compound 15 (Fig. 3) was confirmed
by the appearance C-4″ by two values at δ = 84.0 in 150
and at δ = 121.0 in 15 (Fig. 3). The carbon signal
assigned to carbonyl amide in 15 appeared at δ = 161.0.
using Varian Elementary device in National Research Cen-
ter, Giza, Egypt.
Starting materials.
Compound 1 was bought from
Aldrich. Compounds 2 and 3 were prepared according to
literature procedures [22,23].
1
In H NMR spectrum, the tautomerism with the NH and
Compound 2 was obtained as pale yellow crystals in
70%; mp 98°C (lit. [23] 97.5°C); IR (KBr): νmax 3350
(NH2), 3090 (Ar─CH), 1660 (CO), 1615 (C═N),
1590 cmꢀ1 (C═C); 1H NMR (400 MHz, DMSO-d6):
δ = 9.60 (s, 1H, CHO), 7.60–7.50 (m, 5H, Ph─H), 5.80
(bs, 2H, NH2), 2.30 (s, 3H, CH3).
OH protons were appeared at δ = 8.90 and 11.00 (Fig. 3).
The three methyl carbon signals appeared at 17.8, 15.4,
and 14.0 assigned to (CH3-C), (CH3-B), and CH3-A),
respectively.
On applying the same procedure mentioned in the
literature [23], compound 3 was obtained in 75% yield;
mp 286–288°C (lit. [23] 285°C); IR (KBr): νmax 3320
(NH2), 3080 (Ar─CH), 1660 (CO2Et), 1615 (C═N),
1590 cmꢀ1 (C═C); 1H NMR (400 MHz, DMSO-d6):
δ = 12.20 (s, 1H, NH), 8.20 (s, 1H, pyridine─H),
8.00–7.90 (t, 2H, J = 7 Hz, Ph─H), 7.42–7.30 (m, 3H,
Ph─H), 4.40 (q, 2H, CH2), 2.60 (s, 3H, CH3), 1.40 (t,
CONCLUSION
That work reported the reactions of pyrazolo[3,4-b]
pyridine-5-carbonyl azides and hydrazides with some
nucleophilic reagents. It was observed that of carbonyl
azide derivative of pyrazolo[3,4-b]pyridine-5-carbonyl
azide undergo different reaction pathways—a Curtius
rearrangement [24,25]—compared with related compounds.
Different substituents could be prepared via functional
groups manipulation.
3H, J = 7.0 Hz, CH3).
6,7-Dihydro-3-methyl-6-oxo-1-phenyl-1H-pyrazolo[3,4-b]
pyridine-5-carbohydrazide (4). A mixture of compound 3
(0.5 g, 1.68 mmol) in hydrazine hydrate (5 mL) was
heated under reflux for 5 h. The solution was cooled,
poured onto ice-cold water containing a few drops of
acetic acid, filtered, washed with water, dried, and
recrystallized from ethanol to give 4 as a yellow powder
(0.40 g, 84%); mp 210–212°C; IR (KBr): νmax 3340–
3315 (NHNH2), 3070 (Ar─CH), 2970 (Aliph─CH),
EXPERIMENTAL
General.
Melting points were determined using an
APP Digital ST 15 melting point apparatus. Thin-layer
chromatography analyses were performed on analytical
Merck 9385 silica aluminum sheets (Kieselgel 60) with
PF254 indicator. The IR spectra were recorded as KBr
disks on Shimadzu-408 infrared spectrophotometer,
Faculty of Science, Minia University. The NMR spectra
were measured using a Bruker AV-400 spectrometer at
the Karlsruhe Institut für Technologie, Institute of
Organic Chemistry, Karlsruhe, Germany. Chemical shifts
were expressed as δ (ppm) with tetramethylsilane as inter-
nal reference. The samples were dissolved in DMSO-d6,
s = singlet, d = doublet, dd = doublet of doublet, and
t = triplet. Mass spectrometry were recorded on a Varian
MAT 312 instrument in EI mode (70 eV) at the Karlsruhe
Institut für Technologie, Institute of Organic Chemistry,
Karlsruhe, Germany. Elemental analyses were carried out
1
1680, 1650 (2CO), 1605 (CvN), 1580 cmꢀ1 (C═C); H
NMR (400 MHz, DMSO-d6): δ = 11:15 (s, 1H,
NH─pyridine), 9.40 (s, 1H, NH), 8.10 (s, 1H,
pyridine─H), 7.05–6.96 (m, 5H, Ph─H), 6.50 ppm (s,
2H, NH2), 2.48 (s, 3H, CH3); 13C NMR (100 MHz,
DMSO-d6): δ = 165.0, 164.2 (C═O), 160.3 (C═N),
139.6, 137.0 (Ar─C), 133.0 (pyridine─CH), 129.8, 126.0
(Ar─C), 127.9, 126.9 (Ar─2CH), 124.0 (Ar─H), 14.4
(CH3) ppm. MS (70 eV, %): m/z 283 (M+, 100), 161
(55), 77 (66). Anal. Calcd for C14H13N5O2 (283.29): C,
59.36; H, 4.63; N, 24.72. Found: C, 59.40; H, 4.60; N,
24.90%.
5-(Azidocarbonyl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]
pyridin-6(7H)-one (5). A cold solution (0–5°C) of sodium
Journal of Heterocyclic Chemistry
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Synthesis of New Heterocycles from Reactions of 1-Phenyl-1H-pyrazolo[3,4-b]
pyridine-5-carbonyl Azides
nitrite (0.319 g, 45 mmol) in 15 mL water was added to a
suspension of 4 (0.952 g, 4 mmol) in 1M HCl (2 mL) in
an ice bath (0–5°C) over a period of 30 min. The reaction
mixture was left to stir for 1 h at the same temperature
and then poured into excess water. The yellow precipitate
was filtered off and washed thoroughly with water then
dried and left without crystallization to give yellow
powder 5 (0.90 g, 80%); mp 110–111°C; IR (KBr): νmax
3100 (Ar─CH), 2950 (Aliph─CH), 2147 (CON3), and
the same temperature and then poured into excess water.
The yellow product was filtered off, washed with water,
dried, and left without recrystallization to give 8 (0.95 g,
84%); mp 110–111°C; IR (KBr): ν = 2140 (CON3) and
1699 cmꢀ1 (CO).
3-Methyl-1-phenyl-1,5-dihydro-6H-oxazolo[5,4-b]
pyrazolo[4,3-e]pyridin-6-one (9). A mixture of 5 (0.5 g,
1.7 mmol) and methanol (15 mL) was heated under
gentle reflux for 2 h. The solution cooled, poured onto
ice cold water, filtered, washed with water (100 mL),
dried, and recrystallized from ethanol to give 9 (0.33 g,
75%) as yellow crystals; mp 270–272°C; IR (KBr): νmax
3184 (NH), 3184 (Ar─CH), 2990 (Aliph─CH), 1680
1632 (C═N) cmꢀ1
.
Ethyl 3,6-dimethyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-
carboxylate (6). A mixture of 2 (0.5 g, 2.48 mmol) and
ethyl acetoacetate (0.32 g, 2.48 mmol) in acetic acid
(20 mL) was heated under reflux for 24 h. The solution
was cooled, poured onto ice-cold water, filtered, washed
with water, dried, and recrystallized from ethanol to
give white powder 6 (0.67 g, 92%); mp 100–101°C (lit.
[22] 101–103°C); IR (KBr): νmax 2921 (Aliph─CH),
(CO) cmꢀ1
;
1H NMR: (400 MHz, DMSO-d6):
δ = 12.10 (s, 1H, NH), 8.10 (dd, 2H, J = 7.2, 1.0 Hz,
H-c), 7.90 (s, 1H, H-4), 7.30–7.28 (m, 2H, H-b), 7.20
(m, 1H, H-d), 2.50 (s, 3H, CH3─pyrazole); 13C NMR
(100 MHz, DMSO-d6): δ = 165.0 (CO), 164.1 (C-70),
150.2 (C-80), 143.0 (C-40), 141.0 (C-e), 138.2 (C-3),
132.0 (C-4), 127.8 (2CH-c), 123.4 (CH-d), 122.0 (2CH-
b), 115.0 (C-30), 12.4 (CH3-a). MS (70 eV, %): m/z 266
(100%). Anal. Calcd for C14H10N4O2 (266.26): C,
63.15; H, 3.79; N, 21.04. Found: C, 63.00; H, 3.70;
1
1712 cmꢀ1 (CO-ester); H NMR (400 MHz, DMSO-d6):
δ = 8.30 (s, 1H, pyridine─H), 7.15–6.95 (m, 5H, Ph─H),
4.30 (q, 2H, J = 7.0 Hz, CH2), 2.60 (s, 3H, CH3), 2.48
(s, 3H, CH3), 1.50 (t, 3H, J = 7.0, CH3); 13C NMR
(100 MHz, DMSO-d6): δ = 165.0 (C═O), 163.3, 161.0
(C═N), 139.0, 138.4 (Ar─C), 133.0 (pyridine─CH),
129.8, 126.0 (Ar─C), 127.9, 126.9 (Ar─2CH), 124.0
(Ar─CH), 62.0 (CH2-ester), 20.1, 14.3, 12.4 (CH3) ppm.
MS (70 eV, %): m/z 295 (M+, 100), 161 (55), 77 (66).
Anal. Calcd for C17H17N3O2 (295.34): C, 69.14; H, 5.80;
N, 14.23. Found: C, 69.30; H, 5.65; N, 14.10%.
N, 21.20%.
Crystal structure determination of 9. The single-crystal
X-ray diffraction study was carried out on a Bruker D8
Venture diffractometer with Photon100 detector at 123(2)
K using Cu–Kα radiation (λ = 1.54178 Å). Dual space
methods (SHELXT) [26] were used for structure solution,
and refinement was carried out using SHELXL-2014
(full-matrix least-squares on F2) [27]. Hydrogen atoms
were refined using a riding model (H(N). A semi-
empirical absorption correction was applied. Refinement
with the listed atoms shows residual electron density due
to a heavily disordered ethanol solvent that could not be
refined with split atom model. In addition, there are
traces of water. Therefore, the option “SQUEEZE” of the
program package PLATON [28] was used to create an
hkl file taking into account the residual electron density
in the void areas.
3,6-Dimethyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-
carbohydrazide (7).
A mixture of the ester 6 (5.90 g,
20 mmol) and hydrazine hydrate (15 mL) was heated
under reflux for 7 h. The product that formed was then
poured into cold water, filtered, washed with water, dried,
and crystallized from ethanol to give buff crystals of 7
(6.09 g, 80%); mp: 170–2°C; IR (KBr): νmax 3428, 3288
(NH2), 2970 (Aliph─CH), 1680 (CO); 1H NMR
(400 MHz, DMSO-d6): δ = 60 (bs, 1H, NH─hydrazine),
8.30 (s, 1H, pyridine─H), 7.40–7.30 (m, 5H, Ph─H),
5.90 (bs, 2H, NH2─hydrazine), 2.56 (s, 3H, CH3), 2.10
(s, 3H, CH3); 13C NMR (100 MHz, DMSO-d6):
δ = 165.3 (C═O), 160.6, 160.0 (C═N), 138.4, 138.0
(Ar─C), 132.6 (pyridine─CH), 129.4, 126.4 (Ar─C),
128.0, 126.7 (Ar─2CH), 124.2 (Ar─CH), 20.4, 16.1
(CH3) ppm. MS (70 eV, %): m/z 281 (M+, 100), 160
(45), 77 (60). Anal. Calcd for C15H15N5O (281.32): C,
64.04; H, 5.37; N, 24.90. Found: C, 63.90; H, 5.45; N,
25.00%.
9: Colorless crystals, C14H10N2O4 · 1/3(C2H6O),
Mr = 281.61, crystal size 0.20 × 0.18 × 0.08 mm,
triclinic, space group P-1 (No. 2), a = 10.6979(3) Å,
b = 14.3577(4) Å, c = 14.5395(4) Å, α = 68.818(1)°,
β = 84.428(1)°, γ = 72.303(1)°, V = 1983.60(10) Å3,
Z = 6, ρ = 1.414 Mg/mꢀ3, μ (Cu–Kα) = 0.825 mmꢀ1
,
F(000) = 880, 2θmax = 144.6°, 30117 reflections, of
which 7760 were independent (Rint = 0.032), 553
parameters, 3 restraints, R1 = 0.041 (for 6663 I > 2σ(I)),
Azido (3,6-dimethyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-5-
yl)methanone (8).
A cold solution (0–5°C) of sodium
wR2 = 0.108 (all data), S = 1.03, largest diff.
nitrite (0.32 g, 45 mmol) in 15 mL water was added to a
suspension of carbohydrazide 7 (1.1 g, 4 mmol) in 1M
HCl (2 mL) in an ice bath (0–5°C) over a period of
30 min. The reaction mixture was left to stir for 1 h at
peak/hole = 0.384/ꢀ0.218 e Åꢀ3
.
CCDC 1840903 (9) contains the supplementary
crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge
Journal of Heterocyclic Chemistry
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A. A. Aly, T. I. El-Emary, A.-F. E. Mourad, Z. K. Alyan, S. Bräse, and M. Nieger
Vol 000
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Methyl 3,6-dimethyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-5-
yl-carbamate (12). A mixture of 8 (0.29 g, 1 mmol) in
CH3); 13C NMR (100 MHz, DMSO-d6): δ = 209.0
(2CO), 163.0 (CO), 153.0, 152.0 (C═N), 142.0, 138.0
(Ar─C), 129.7 (Ar─2CH), 128.4 (CH-4), 127.0, 126.0
(Ar─C), 119.0 (Ar─2CH), 115.4 (Ar─CH-p), 96.0
(CH), 22.4 (2CH3), 13.2, 12.2 ppm (CH3). MS (70 eV,
%): m/z = 364 (100), 263 (65), 237 (80). Anal. Calcd
for C20H20N4O3 (364.40): C, 65.92; H, 5.53; N, 15.38.
methanol (50 mL) was heated under reflux for 10 h. The
solution was cooled, poured onto ice-cold water, filtered,
washed with water, dried, and recrystallized from
ethanol/water (1:1) to give brown crystals of 12 (0.23 g,
80%); mp 180–181°C; IR (KBr): νmax 3251 (NH), 3050
(Ar─CH), 2917 (Aliph─CH), 1684 (CO) cmꢀ1; IR
(KBr): 3180 (NH), 3180 (Ar─CH), 2890 (Aliph─CH),
Found: C, 65.90; H, 5.50; N, 15.43%.
N-(3,6-Dimethyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-5-yl)-3-
methyl-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazole-4-
carboxamide (15).
A mixture of carboazide 8 (0.25 g,
1684 (CO) cmꢀ1 1H NMR: (400 MHz, DMSO-d6):
;
0.85 mmol) and 1-phenyl-3-methyl-5-pyrazolone (0.15 g,
0.86 mmol) was heated in xylene under reflux for 5 h.
The reaction mixture was then poured onto petroleum
ether, filtered, and recrystallized from dioxane to give
buff powder 15 (0.28 g, 78%); mp 330–332°C; IR (KBr):
νmax 3450 (OH), 3282 (NH), 3030 (Ar─CH), 2919
δ = 9.10 (s, 1H, NH), 7.92 (s, 1H, H-4), 7.30–7.19 (m,
5H, Ar─H), 3.40 (s, 3H, CH3-ester), 2.60 (s, 3H, CH3),
2.30 (s, 3H, CH3); 13C NMR (100 MHz, DMSO-d6):
δ = 162.0 (CO), 152.1, 151.20 (C═N), 138.0, 135.0,
133.1, 131.0, 130.0 (Ar─C), 128.2, 127.2 (Ar─2CH),
123.0 (Ar─CH-p), 25.4, 20.4, 15.9 ppm (CH3). MS
(70 eV, %): m/z 296 (100). Anal. Calcd for C16H16N4O2
(296.33): C, 64.85; H, 5.44; N, 18.91. Found: C, 64.80;
H, 5.40; N, 19.00%.
(Aliph─CH), 1680 (CO) cmꢀ1 1H NMR: (400 MHz,
;
DMSO-d6): δ = 11.0 (s, 1H, OH (NH)), 8.90 (s, 1H, NH
(OH)), 8.10 (s, 1H, H-4), 7.50–7.30 (m, 6H, Ar─H),
7.40–7.25
(m,
4H,
Ar─H),
3.40
(s,
3H,
CH3─pyrazolone), 2.60 (s, 3H, CH3─pyrazole), 2.20 (s,
3H, CH3─pyridine); 13C NMR (100 MHz, DMSO-d6):
δ = 164.0 (CO─pyrazolone), 161.0 (CO─amide), 153.4,
151.2, 150.0 (C═N), 137.7, 135.0, 133.2 (Ar─C), 132.8
(CH-4), 130.6, 130.0 (Ar─C), 128.6, 128.0, 127.6, 126.7
(Ar─2CH), 122.4, 122.2 (Ar─CH-p), 121.0 (C-4″), 80.0
(C-40-pyrazolone), 17.8 (CH3-C), 15.4 (CH3-B), 14.0
(CH3-A) ppm (CH3). MS (70 eV, %): m/z 438 (100), 397
(43), 345 (75), 306 (80), 288 (40). Anal. Calcd for
C25H22N6O2 (438.49): C, 68.48; H, 5.06; N, 19.17.
Found: C, 68.60; H, 5.16; N, 19.30%.
N-(3,6-Dimethyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-yl)
hydrazinecarboxamide (13).
A mixture of methyl
carboazide 8 (0.5 g, 1.7 mmol) and hydrazine hydrate
(0.85 mL, 1.7 mmol) in xylene (50 mL) was heated
under reflux for 11 h. The reaction mixture was poured
onto petroleum ether, filtered, and washed with petroleum
ether, recrystallized from DMF : water (4:1) to give buff
crystals of 13 (0.50 g, 81%); mp 310–312°C; IR (KBr):
νmax 3230–2150 (NHNH2), 3020 (Ar─CH), 2860
(Aliph─CH), 1680 (CO) cmꢀ1 1H NMR: (400 MHz,
;
DMSO-d6): δ = 9.10 (s, 1H, NH─hydrazine), 8.20 (s,
1H, NH), 8.00 (s, 1H, H-4), 7.48–7.44 (m, 2H, Ar─H),
7.24–7.18 (m, 5H, Ar─H, NH2─hydrazine), 2.75 (s, 3H,
CH3), 2.60 (s, 3H, CH3); 13C NMR (100 MHz,
DMSO-d6): δ = 161.0 (CO), 152.4, 151.5 (C═N), 143.0,
140.0 (Ar─C), 133.0 (CH-4), 130.0 (Ar─2CH), 128.8
(Ar─C), 124.0 (Ar─CH), 122.0 (Ar─2CH), 115.4
(Ar─CH-p), 25.0, 14.0 ppm (CH3). MS (70 eV, %): 296
(100). Anal. Calcd for C15H16N6O (296.33): C, 60.80; H,
5.44; N, 28.36. Found: C, 60.70; H, 5.40; N, 28.40%.
Acknowledgment. The authors thank 2-MET society for
financial support for the accommodation of Prof. Ashraf A. Aly
at the Institute of Organic Chemistry, Karlsruhe, Germany.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet