Synthesis and characterization of new 1H-pyrazolo[3,4-b]pyridine phosphoramidate derivatives

Article abstract of DOI:10.3998/ark.5550190.p008.413

Twelve new 1H-pyrazolo[3,4-b]pyridine phosphoramidate derivatives were synthesized under mild conditions by nucleophilic aromatic substitution reaction of aminoalkylphosphoramidates over 4-Cl substituted pyrazolo[3,4-b]pyridine in good yields. The new com

Full text of DOI:10.3998/ark.5550190.p008.413

General Papers
ARKIVOC 2014 (iv) 38-50
Synthesis and characterization of new 1H-pyrazolo[3,4-b]pyridine
phosphoramidate derivatives
Leandro F. Pedrosa,a William P. de Macedo,a Antonia C. R. Furtado,a
Guilherme P. Guedes,a,b Julio C. Borges,a Jackson A. L. C. Resende,a Maria G. F. Vaz,a
Alice M. R. Bernardinoa and Marcos C. de Souzaa*
a Instituto de Química, Universidade Federal Fluminense, 24020-141, Niterói, RJ, Brazil
b Instituto de Ciências Exatas - Departamento de Química, Universidade Federal Rural
do Rio de Janeiro, 23070-200, Seropédica, RJ, Brazil
E-mail: gqomarc@vm.uff.br
DOI: http://dx.doi.org/10.3998/ark.5550190.p008.413
Abstract
Twelve new 1H-pyrazolo[3,4-b]pyridine phosphoramidate derivatives were synthesized under
mild conditions by nucleophilic aromatic substitution reaction of aminoalkylphosphoramidates
over 4-Cl substituted pyrazolo[3,4-b]pyridine in good yields. The new compounds were charac-
1
terized by IR, H, 13C and 31P NMR spectroscopy and HRMS. The crystal structure of one
compound was solved by X-ray diffraction and showed a network of intermolecular interactions
involving phosphoramidate groups.
Keywords: 1H-Pyrazolo[3,4-b]pyridine, crystal structure, phosphoramidate, pyrazolopyridines
Introduction
Fused heterocyclic containing pyrazolopyridine systems have been described associated with
several biological and medicinal activities.1-4 Substituted pyrazolo[3,4-b]pyridines represent a
very important building block in organic synthesis and numerous studies have been reported due
to their well-documented biological activity.5-8 Several 4-substituted pyrazolo[3,4-b]pyridines
have been obtained by our group through nucleophilic substitution of the 4-chloro precursor with
variable nucleophiles and showed antileishmanial,5 antiviral9 and antibacterial10,11 promise.
It is known that coupling molecules with well-established pharmacological activities might
be a good strategy to develop new significant products.12 In this context, heterocyclic linked to
other biologically active molecules, like, e.g., phosphoramidates, can give rise to new derivatives
with potential biological applications.13-18 Introduction of a phosphoramidate group essentially
changes the physical and chemical properties of the parent molecule, resulting in the
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improvement of both polarization and intermolecular bonding characteristics.19,20 Our particular
interest in the synthesis of substituted 1H-pyrazolo[3,4-b]pyridine phosphoramidates is use them
in chemotherapies for tropical diseases. In this work we report the first synthesis of
pyrazolopyridine phosphoramidate derivatives as well as a discussion based on the X-ray
diffraction of one representative derivative.
Results and Discussion
The syntheses of the new 1H-pyrazolo[3,4-b]pyridine phosphoramidates 8a-l were performed by
nucleophilic aromatic substitution of the chlorine atom in 4-substituted pyrazolo[3,4-b]pyridines
(4a-c) by aminoalkylphosphoramidates 7a-d (Scheme 1). The starting 4-chloro-1H-pyrazolo-
[3,4-b]pyridine derivatives 4a-c were available in our laboratory and could be easily prepared
from condensation of appropriate hydrazine (1a,b) and β-aminocrotononitrile or benzoyl-
acetonitrile, followed by condensation of the intermediate 5-aminopyrazoles (2a-c) with diethyl
ethoxymethylenemalonate and then by ‘chlorocyclization’ with POCl3. Finally 4a-c were
purified by recrystallization from ethanol.21-24
Scheme 1. Reagents and conditions: (i) β-aminocrotononitrile or benzoylacetonitrile (ii) diethyl
ethoxymethylenemalonate, ethanol, reflux, 2 h (iii) POCl3, 110 ºC, 5 h, (iv) CCl4, ethanol, T < 55
ºC, 10 min; (v) 7a-d, THF, reflux, 9-12 h.
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The aminoalkylphosphoramidates 7a-d were synthesized from diisopropylphosphonate 5
and aliphatic diamines 6a-d.25,26 In order to guarantee monophosphorylation of the diamines, at
least 2.5-fold excess of diamine in ethanol were used. Keeping alkaline pH and temperature
below 55 °C is required to avoid bis-phosphorylation.
Nucleophilic aromatic substitution of the chlorine atom in 4-substituted pyrazolo[3,4-b]-
pyridines by amines has been used as a versatile route to new pyrazolopyridine
derivatives.5,9,27-30 Thus, reaction of 4a-c with an excess (2 equiv.) of aminoalkyl-
phosphoramidates 7a-d in refluxing THF for 9 to 12 h afforded the 1H-pyrazolo[3,4-b]pyridine
phosphoramidates derivatives 8a-l in 52-98% yield (Table 1). The presence of an electron-
withdrawing group (-CO2Et) in 5-position of the substrate 4 and the excess of the nucleophilic
agent 7 facilitate the reaction. The products were fully characterized by infrared, 1H, 13C, and 31P
NMR spectroscopies and by high resolution mass spectrometry (HRMS).
Table 1. 1H-Pyrazolo[3,4-b]pyridine phosphoramidates 8a-l prepared
Entry Compd.
R1
Me
Me
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
R2
Me
Me
Me
Me
Me
Me
Me
Me
Ph
n
2
3
4
6
2
3
4
6
2
3
4
6
Mp (°C) Yielda (%)
1
2
3
4
5
125-126
118-120
42-44
Oil
80
60
81
65
80
75
98
82
54
69
53
52
8a
8b
8c
8d
8e
8f
140-142
94-95
83-84
60-63
Oil
6
7
8
9
8g
8h
8i
10
11
12
Ph
Ph
Ph
110-111
Oil
8j
8k
8l
Oil
a Yields of pure, isolated products.
1
The H NMR spectra of compounds 8a-l showed a singlet in the range of 8.85-9.00 ppm
attributable to the pyridine ring proton. The same spectra showed a quartet and triplet signals
related to the ethyl ester group in the ranges 4.27-4.38 ppm and 1.38-1.41 ppm, respectively. The
resonances of the isopropyl protons appeared as two doublets at 1.17-1.32 ppm and a doublet of
septets around 4.56 ppm with 3JHH ~ 6.2 Hz and 3JPH ~ 7.5 Hz. The NH signal was detected as a
3
broad triplet in the range 8.76-9.31 ppm with JHH ~ 5.1 Hz . On the other hand, NHP protons
showed coupling with phosphorus and the neighbor methylene group, giving rise to a doublet of
3
2
triplet around 2.80 ppm with JHH ~ 7.0 Hz and JPH ~ 9.0 Hz. In the aliphatic region, the
unequivocal assignment of the signals for methylene protons was based on COSY correlations.
The N-methyl protons signal of compounds 8a-d appeared as a singlet around 2.65-3.98 ppm and
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the methyl protons signal for compounds 8a-h showed as a singlet at 2.76 ppm. Compounds 8e-l
showed signals characteristic for aromatic protons of the phenyl groups around 7.27-8.21 ppm.
2
Typically, the methyne carbon signal in β position to phosphorus appears as a doublet with JPC
13
~5.2 Hz around 70.8 ppm in C NMR spectroscopy. In all cases phosphorus and carbon in the
aliphatic region showed coupling with 3JPC ~5.2 Hz, but no coupling 2JPC was observed. The 1H-
31
pyrazolo[3,4-b]pyridine phosphoramidates 8a-l showed in their decoupled P NMR spectra one
signal in the region between 7.01-7.60 ppm, typical for phosphoramidates.31-34 Furthermore,
infrared spectra exhibited strong absorptions for the P=O at 1269-1263 cm-1, P-O around 990-
978cm-1 and absorptions for the carbonyl group at 1680-1663 cm-1. In the 3435-3199 cm-1
region, NH bands were observed.
Figure 1. Ortep representation of the asymmetric unit of 8j. Ellipsoids at 50% of probability.
Single crystals of compound 8j suitable for X-ray diffraction were obtained by slow solvent
evaporation at room temperature. The crystal data and structure refinement parameters for this
compound are provided (See Supplementary Material, Table S1). The ORTEP representation of
the asymmetric unit is shown in Figure 1. In this structure, the phosphoramidate group nitrogen
atom is bonded to an aliphatic chain containing three carbon atoms, namely C1, C2 and C3. The
bond lengths and angles are typical of phosphoramidate groups (Table S2). The 5-
(ethoxycarbonyl)-1,3-diphenyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino moiety is linked to the
alkyl skeleton through C3 atom. The torsion angle between the pyrazolo[3,4-b]pyridine plane
and the phenyl group linked to N2A atom is 38.1º, while the torsion angle of the other phenyl
groups linked to C9A atom is 30.5º. As consequence of the spatial arrangement of the phenyl
groups, weak intermolecular interaction C-H···O, C-H···π e π···π stacking involving the 5-
(ethoxycarbonyl)-1,3-diphenyl-1H-pyrazolo[3,4-b]pyridine moiety contributed to stabilize the
crystal packing. Intramolecular hydrogen bonding between ester O4 oxygen and N2 amine atoms
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was also observed. Furthermore, dimers of molecules raised due to the intermolecular hydrogen
bonding involving the phosphoramidate O1 and N1 atoms (Figure 2), as previously reported for
this compound class34 (Table 2).
Figure 2. Hydrogen-bonding in compound 8j.
Table 2. Hydrogen-bond geometry for 8j (Å, °)
D—H···A
D—H
H···A
D···A
D—H···A
N2—H2···O4
0.86
2.27
2.715 (3)
112
N1—H1···O1i
0.86
2.19
2.933 (3)
145
Symmetry code: (i) −x+2, −y+1, −z.
Conclusions
The methodology for nucleophilic aromatic substitution of the chlorine atom in 4-substituted
pyrazolo[3,4-b]pyridine was successfully applied to aminoalkylphosphoramidates as the
nucleophile. In this context, twelve new reported 1H-pyrazolo[3,4-b]pyridine phosphoramidates
were synthesized and characterized. The crystal data for a representative compound pointed out
the formation of dimer due to the intermolecular hydrogen bonding involving the
phosphoramidate O and N atoms.
Experimental Section
General. Analytical grade reagents and solvents were purchased from commercial sources and
used without further purification. Melting points were obtained with a Fisher-Johns apparatus.
13
31
1H, C and P NMR spectra were recorded on a Varian UP-300 spectrometer at 299.95, 75.42
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and 121.42 MHz, respectively, with TMS as internal standard or 85% H3PO4 as external
standard. The chemical shifts (δ) are reported in ppm and the coupling constants (J) in hertz.
TLC was carried out using silica gel F-254 Glass Plate (20 × 20 cm). Infrared spectra were
recorded on a Perkin-Elmer Spectrum One FT-IR spectrometer. High resolution mass spectra
(EI-70eV) were performed on a Varian MAT CH7 8500 direct inlet instrument. The Cl-
substituted pyrazolo[3,4-b]pyridine (4a-c)21-24 and aminoalkylphosphoramidates (7a-d)25,26
compounds were prepared as previously reported.
Typical procedure for preparation of 1H-pyrazolo[3,4-b]pyridine phosphoramidates
derivatives (8a-l). Cl-substituted pyrazolo[3,4-b]pyridine (4a-c) (2.2 mmol) and the
aminoalkylphosphoramidate (7a-d) (4.4 mmol) were dissolved in THF (10 mL) and the reaction
mixture was heated at reflux until the disappearance of the starting 4 (9-12 h, monitored by
TLC). The mixture was poured into ice and the resulting solid (except 8d,i,k,l) was filtered off,
washed with distilled water and dried. Solids were recrystallized from ethanol/water (1:3).
Compounds 8d,i,k,l were diluted with chloroform and washed with water (3 × 10 mL). The
organic layer was dried with anhydrous sodium sulfate and filtered, and the solvent was
evaporated under reduced pressure giving an oily product.
Diisopropyl
2-[5-(ethoxycarbonyl)-1,3-dimethyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
ethylphosphoramidate (8a). Pale brown solid; yield 80%; mp 125-126 °C; IR (KBr, νmax, cm-1):
3222 (m, νN-H), 2978 (m), 2933 (m), 1671(s, νC=O), 1586 (s), 1538 (m), 1434 (m), 1372 (w),
1
1339 (m), 1269 (m, νP=O), 1188 (m), 1108 (m), 978 (s, νP-O), 899 (w), 795 (w), 665 (w); H
3
3
NMR (CDCl3): δH 1.25 and 1.28 (2d, 12H, J(HH) 6.4), 1.40 (t, 3H, J(HH) 6.9), 2.66 (s, 3H), 2.85
(dt, 1H, 3J(HH) 5.4 and 3.6), 3.28 (m, 2H), 3.74 (dt, 2H, J(HH) 6.0 and 5.4), 3.98 (s, 3H), 4.34 (q,
3
2H, J(HH) 6.9), 4.57 (dsep, 2H, J(HH) 6.3 and 3J(PH) 7.5), 8.86 (s, 1H), 9.24 (br t, 1H, J(HH) 5.0);
3
3
3
13C NMR (CDCl3): δC 14.16, 18.44, 23.61 (d, J(PC) 5.1), 33.55, 41.83, 49.69 (d, J(PC) 5.9),
3
2
60.41, 70.94 (d, J(PC) 5.9), 100.61, 103.08, 140.19, 152.33, 154.13, 154.93, 169.24; 31P NMR
2
(CDCl3): δP 7.18 (s); HRMS (EI): m/z [M+H] calcd. for C19H32N5O5P: 441.21411. Found:
441.21400.
Diisopropyl
3-[5-(ethoxycarbonyl)-1,3-dimethyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
propylphosphoramidate (8b). Pale brown solid; yield 60%; mp 118-120 °C; IR (KBr, νmax, cm-
1): 3213 (m, νN-H), 2976 (m), 2933 (m), 1663(s, νC=O), 1583 (s), 1536 (m), 1457 (m), 1372
(w), 1337 (m), 1264 (m, νP=O), 1228 (m), 1185 (m), 1115 (m), 978 (s, νP-O), 897 (w), 800 (w),
1
3
3
658 (w); H NMR (CDCl3): δH 1.27 and 1.29 (2d, 12H, J(HH) 6.0), 1.38 (t, 3H, J(HH) 7.2), 1.94
3
3
(quin, 2H, J(HH) 6.6), 2.54 (dt, 1H, J(HH) 8.7 and 7.2), 2.67 (s, 3H), 3.06 (m, 2H), 3.69 (dt, 2H,
3J(HH) 6.6 and 5.0), 3.97 (s, 3H), 4.33 (q, 2H, 3J(HH) 7.2), 4.56 (dsep, 2H, 3J(HH) 6.0 and 3J(PH) 7.2),
8.86 (s, 1H), 9.31 (br t, 1H, J(HH) 3.9); 13C NMR (CDCl3): δC 14.15, 18.70, 23.63 (d, J(PC) 5.0),
3
3
3
2
32.32 (d, J(PC) 5.3), 33.44, 38.58, 45.32, 60.20, 70.63 (d, J(PC) 5.3), 99.93, 102.60, 140.21,
152.28, 154.13, 154.52, 169.24; P NMR (CDCl3): δP 7.40 (s); HRMS (EI): m/z [M+H] calcd.
31
for C20H34N5O5P: 455.22976. Found: 455.22991.
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Diisopropyl
4-[5-(ethoxycarbonyl)-1,3-dimethyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
butylphosphoramidate (8c). Beige solid; yield 81%; mp 42-44 °C; IR (KBr, νmax, cm-1): 3234
(m, νN-H), 2978 (m), 2934 (m), 1669 (s, νC=O), 1579 (s), 1536 (m), 1436 (m), 1373 (w), 1336
(m), 1263 (m, νP=O), 1187 (m), 1124 (m), 987 (s, νP-O), 896 (w), 799 (w), 753 (w), 665 (w); 1H
3
3
NMR (CDCl3): δH 1.29 and 1.31 (2d, 12H, J(HH) 6.0 and 4.7), 1.39 (t, 3H, J(HH) 7.2), 1.71 (m,
7H), 2.49 (dt, 1H, 3J(HH) 7.8 and 7.5), 2.70 (s, 3H), 2.97 (m, 2H), 3.63 (dt, 2H, 3J(HH) 6.6 and 4.7),
3
3
3.97 (s, 3H), 4.33 (q, 2H, J(HH) 7.2), 4.59 (dsep, 2H, J(HH) 6.3 and 3J(PH) 7.8), 8.86 (s, 1H), 9.33
3
13
3
(br t, 1H, J(HH) 3.9); C NMR (CDCl3): δC 14.19, 18.68, 23.70 (d, J(PC) 6.1), 27.64, 28.87 (d,
3J(PC) 6.4), 33.50, 40.94, 47.95, 60.31, 70.62 (d, J(PC) 5.6), 99.94, 102.65, 140.23, 152.39,
2
154.19, 154.59, 169.29; 31P NMR (CDCl3): δP 7.40 (s); HRMS (EI): m/z [M+H] calcd. for
C21H36N5O5P: 469.24541. Found: 469.24540.
Diisopropyl
6-[5-(ethoxycarbonyl)-1,3-dimethyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
hexylphosphoramidate (8d). Oil; yield 65%; IR (KBr, νmax, cm-1): 3233 (m, νN-H), 2977 (m),
2934 (m), 1670(s, νC=O), 1580 (s), 1536 (m), 1437 (m), 1373 (w), 1337 (m), 1263 (m, νP=O),
1
1181 (m), 1124 (m), 985 (s, νP-O), 896 (w), 799 (w), 665 (w); H NMR (CDCl3): δH 1.30 and
1.32 (2d, 12H, 3J(HH) 6.3), 1.47 (m, 11H), 1.70 (quin, 2H, 3J(HH) 6.1), 2.64 (m, 6H), 2.86 (m, 2H),
3
3
3
3.60 (dt, 2H, J(HH) 6.6 and 5.1), 3.95 (s, 3H), 4.37 (q, 2H, J(HH) 7.1), 4.60 (dsep, 2H, J(HH) 6.0
and 3J(PH) 7.5), 8.85 (s, 1H), 9.31 (br t, 1H, 3J(HH) 4.0); 13C NMR (CDCl3): δC 13.97, 18.49, 23.46
3
3
(d, J(PC) 4.5), 25.99, 26.13, 30.15, 31.19 (d, J(PC) 6.6), 33.21, 40.96, 47.94, 60.01, 70.15 (d,
2J(PC) 5.5), 99.53, 102.27, 139.97, 152.08, 153.87, 154.25, 168.99; 31P NMR (CDCl3): δP 7.47 (s);
HRMS (EI): m/z [M+H] calcd. for C23H40N5O5P: 497.27671. Found: 497.27680.
Diisopropyl
2-[5-(ethoxycarbonyl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl-
amino]ethylphosphoramidate (8e). Pale brown solid; yield 80%; mp 140-142 °C; IR (KBr,
νmax, cm-1): 3202 (m, νN-H), 2979 (m), 2931 (m), 1675(s, νC=O), 1599 (s), 1508 (m), 1438 (m),
1373 (w), 1345 (m), 1268 (m, νP=O), 1235 (s), 1129 (m), 1108 (m), 989 (s, νP-O), 897 (w), 797
1
3
3
(w), 665 (w); H NMR (CDCl3): δH 1.25 and 1.28 (2d, 12H, J(HH) 6.3), 1.40 (t, 3H, J(HH) 6.9),
2.75 (s, 3H), 2.87 (dt, 1H, 3J(HH) 9.0 and 6.8), 3.26 (m, 2H), 3.75 (dt, 2H, 3J(HH) 9.0 and 6.3), 4.32
(q, 2H, 3J(HH) 6.9), 4.58 (dsep, 2H, 3J(HH) 6.3 and 3J(PH) 9.0), 7.30 (t, 1H, 3J(HH) 6.3), 7.49 (m, 2H),
8.09 (d, 2H, J(HH) 8.6), 8.87 (s, 1H), 9.10 (br t, 1H, J(HH) 4.8); 13C NMR (CDCl3): δC 14.10,
3
3
3
2
2
18.33, 23.59 (d, J(PC) 4.9), 41.95, 50.19 (d, J(PC) 4.4), 60.52, 70.90 (d, J(PC) 5.7), 102.06,
104.92, 122.10, 126.13, 128.80, 138.70, 141.97, 152.63, 153.94, 154.98, 168.95; 31P NMR
(CDCl3): δP 7.23 (s); HRMS (EI): m/z [M+H] calcd. for C24H34N5O5P: 503.22976. Found:
503.22930.
Diisopropyl
3-[5-(ethoxycarbonyl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl-
amino]propylphosphoramidate (8f). Beige solid; yield 75%; mp 94-95 °C; IR (KBr, νmax, cm-
1): 3199 (m, νN-H), 2978 (m), 2930 (m), 1679 (s, νC=O), 1583 (s), 1526 (m), 1444 (m), 1371
(w), 1273 (m), 1228 (m, νP=O), 1153 (m), 1109 (m), 979 (s, νP-O), 897 (w), 799 (w), 690 (w);
1H NMR (CDCl3): δH 1.27 and 1.29 (2d, 12H, 3J(HH) 6.0), 1.39 (t, 3H, 3J(HH) 7.2), 1.95 (quin, 2H,
3
3
3J(HH) 6.6), 2.58 (dt, 1H, J(HH) 8.9 and 6.0), 2.76 (s, 3H), 3.07 (m, 2H), 3.72 (dt, 2H, J(HH) 6.9
and 4.8), 4.35 (q, 2H, 3J(HH) 7.2), 4.57 (dsep, 2H, 3J(HH) 6.0 and 3J(PH) 7.5), 7.31 (t, 1H, 3J(HH) 7.5),
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7.50 (t, 2H, 3J(HH) 7.5), 8.06 (d, 2H, 3J(HH) 8.6), 8.93 (s, 1H), 9.24 (br t, 1H, 3J(HH) 5.4); 13C NMR
3
2
(CDCl3): δC 14.14, 18.71, 23.62 (d, J(PC) 4.4), 23,71, 32.56 (d, J(PC) 5.2), 38.67, 45.89, 60.47,
2
70.78 (d, J(PC) 5.6), 101.44, 104.44, 122.26, 126.19, 128.83, 138.73, 142.05, 152.67, 154.05,
154.64, 169.05; 31P NMR (CDCl3): δP 7.36 (s); HRMS (EI): m/z [M+H] calcd. for C25H36N5O5P:
517.24541. Found: 517.24540.
Diisopropyl
4-[5-(ethoxycarbonyl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl-
amino]butylphosphoramidate (8g). Pale beige solid; yield 98%; mp 83-84 °C; IR (KBr, νmax
,
cm-1): 3202 (m, νN-H), 2980 (m), 2931 (m), 1675(s, νC=O), 1599 (s), 1508 (m), 1438 (m), 1373
(w), 1268 (m, νP=O), 1339 (m), 1235 (m), 1129 (m), 989 (s, νP-O), 761 (w); 1H NMR (CDCl3):
3
3
δH 1.29 and 1.31 (2d, 12H, J(HH) 6.3), 1.39 (t, 3H, J(HH) 7.2), 1.68 (m, 2H), 1.79 (m, 2H), 1.92
3
3
(br s, 1H), 2.52 (dt, 1H, J(HH) 8.9 and 6.3), 2.73 (s, 3H), 2.98 (m, 2H), 3.65 (dt, 2H, J(HH) 6.9
and 4.8), 4.34 (q, 2H, 3J(HH) 7.2), 4.58 (dsep, 2H, 3J(HH) 6.3 and 3J(PH) 7.5), 7.32 (t, 1H, 3J(HH) 7.3),
7.49 (t, 2H, 3J(HH) 7.5), 8.08 (d, 2H, 3J(HH) 8.5), 8.90 (s, 1H), 9.25 (br t, 1H, 3J(HH) 4.5); 13C NMR
(CDCl3): δC 14.13, 18.66, 23.63 (d, J(PC) 4.9), 23.70 (d, J(PC) 4.3), 27.81, 28.80 (d, J(PC) 6.0),
40.92, 48.42, 60.43, 70.60 (d, 2J(PC) 5.8), 101.32, 104.38, 122.21, 126.14, 128.80, 138.73, 142.00,
3
3
2
31
152.68, 154.04, 154.60, 169.02; P NMR (CDCl3): δP 7.47 (s); HRMS (EI): m/z [M+H] calcd.
for C26H38N5O5P: 531.26106. Found: 531.26110.
Diisopropyl
6-[5-(ethoxycarbonyl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-4-yl-
amino]hexylphosphoramidate (8h). Beige solid; yield 82%; mp 60-63 °C; IR (KBr, νmax, cm-1):
3228 (m, νN-H), 2979 (m), 2933 (m), 1677 (s, νC=O), 1596 (s), 1508 (m), 1433 (m), 1374 (w),
1340 (m), 1264 (m, νP=O), 1229 (s), 1130 (m), 1109 (m), 981 (s, νP-O), 895 (w), 796 (w), 750
1
3
(w); H NMR (CDCl3): δH 1.30 and 1.32 (2d, 12H, J(HH) 6.3), 1.45 (m, 9H), 1.76 (m, 2H), 2.47
(m, 1H), 2.75 (s, 3H), 2.81 (m, 2H), 3.62 (dt, 2H, 3J(HH) 6.6 and 5.0), 4.32 (q, 2H, 3J(HH) 7.2), 4.58
3
3
3
3
(dsep, 2H, J(HH) 6.1 and J(PH) 7.5), 7.30 (t, 1H, J(HH) 7.2), 7.49 (t, 2H, J(HH) 7.2), 8.05 (d, 2H,
3J(HH) 8.0), 8.93 (s, 1H), 9.24 (br s, 1H); 13C NMR (CDCl3): δC 14.18, 18.76, 23.73 (d, 3J(PC) 5.0),
26.24, 26.40, 31.44 (d, J(PC) 6.5), 41.23, 48.73, 60.52, 70.53 (d, J(PC) 5.0), 101.33, 104.41,
2
2
31
122.36, 126.32, 128.90, 138.65, 142.18, 154.73, 168.99; P NMR (CDCl3): δP 7.60 (s); HRMS
(EI): m/z [M+H] calcd. for C28H42N5O5P: 559.29236. Found: 559.29230.
Diisopropyl
2-[5-(ethoxycarbonyl)-1,3-diphenyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
ethylphosphoramidate (8i). Oil; yield 54%; IR (KBr, νmax, cm-1): 3202 (m, νN-H), 2980 (m),
2931 (m), 1675 (s, νC=O), 1599 (s), 1508 (m), 1438 (m), 1373 (w), 1345 (w), 1269 (m, νP=O),
1
1235 (s), 1129 (m), 1108 (m), 989 (s, νP-O), 897 (w), 797 (w), 761 (w); H NMR (CDCl3): δH
3
1.17 and 1.23 (2d, 12H, J(HH) 6.4), 1.42 (t, 3H, 3J(HH) 7.2), 2.50 (dt, 1H, 3J(HH) 9.0 and 6.2), 2.78
3
3
3
(m, 2H), 2.90 (dt, 2H, J(HH) 8.9 and 6.0), 4.45 (q, 2H, J(HH) 7.2), 4.49 (dsep, 2H, J(HH) 6.3 and
3
3
3J(PH) 7.8), 7.33 (t, 1H, J(HH) 7.5), 7.51 (m, 5H), 7.69 (d, 2H, J(HH) 8.1), 8.17 (d, 2H, 3J(HH) 8.5),
8.85 (br t, 1H, 3J(HH) 5.7), 9.00 (s, 1H); C NMR (CDCl3): δC 14.01, 23.43 (d, J(PC) 4.9), 41.70,
13
3
50.34 (d, 2J(PC) 5.2), 60.49, 70.58 (d, J(PC) 5.8), 103.15, 103.72, 122.16, 126.31, 128.35, 128.51,
2
31
128.65, 128.71, 134.37, 138.62, 146.62, 152.77, 153.94, 155.26, 168.51; P NMR (CDCl3): δP
7.08 (s); HRMS (EI): m/z [M+H] calcd. for C29H36N5O5P: 565.24541. Found: 565.5400.
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Diisopropyl
3-[5-(ethoxycarbonyl)-1,3-diphenyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
propylphosphoramidate (8j). Pale beige solid; yield 69%; mp 110-111 °C; IR (KBr, νmax, cm-
1): 3230 (m, νN-H), 2978 (m), 2935 (m), 1679 (s, νC=O), 1568 (s), 1504 (m), 1457 (m), 1372
(w), 1338 (m), 1265 (m, νP=O), 1231 (s), 1168 (m), 1100 (m), 985 (s, νP-O), 896 (w), 756 (w),
1
3
3
708 (w); H NMR (CDCl3): δH 1.22 and 1.26 (2d, 12H, J(HH) 6.2), 1.41 (t, 3H, J(HH) 7.2), 1.49
(quin, 2H, 3J(HH) 6.0), 2.10 (dt, 1H, 3J(HH) 8.7 and 6.6), 2.79 (m, 2H), 4.37 (q, 2H, 3J(HH) 7.1), 4.48
(dsep, 2H, 3J(HH) 6.0 and 3J(PH) 7.5), 7.31 (t, 1H, 3J(HH) 7.3), 7.49 (m, 5H), 7.67 (d, 2H, 3J(HH) 8.0),
8.20 (d, 2H, J(HH) 8.6), 8.86 (br t, 1H, J(HH) 5.1), 8.99 (s, 1H); 13C NMR (CDCl3): δC 14.15,
3
3
3
2
2
23.61 (d, J(PC) 4.1), 32.41 (d, J(PC) 5.8), 46.43, 60.53, 70.57 (d, J(PC) 6.0), 102.73, 103.73,
122.38, 126.46, 128.44, 128.64, 128.84, 128.98, 134.97, 138.75, 146.84, 152.95, 154.04, 155.15,
168.71; 31P NMR (CDCl3): δP 7.12 (s); HRMS (EI): m/z [M+H] calcd. for C30H38N5O5P:
579.26106. Found: 579.26120.
Diisopropyl
4-[5-(ethoxycarbonyl)-1,3-diphenyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
butylphosphoramidate (8k). Oil; yield 53%; IR (KBr, νmax, cm-1): 3240 (m, νN-H), 2977 (m),
2932 (m), 1674 (s, νC=O), 1573 (s), 1501 (m), 1462 (m), 1373 (w), 1337 (m), 1262 (m, νP=O),
1
1175 (m), 1106 (m), 989 (s, νP-O), 895 (w), 776 (w), 699 (w); H NMR (CDCl3): δH 1.25 (m,
16H), 1.41 (t, 3H, 3J(HH) 7.2), 2.65 (m, 6H), 2.85 (m, 2H), 4.36 (q, 2H, 3J(HH) 7.1), 4.54 (dsep, 2H,
3
3
3
3J(HH) 6.3 and J(PH) 7.5), 7.30 (t, 1H, J(HH) 7.0), 7.52 (m, 5H), 7.70 (d, 2H, J(HH) 8.0), 8.21 (d,
3
3
13
2H, J(HH) 8.6), 8.79 (br t, 1H, J(HH) 5.4), 8.98 (s, 1H); C NMR (CDCl3): δC 14.05, 23.56 (d,
3J(PC) 4.1), 27.68, 28.45 (d, J(PC) 4.1), 40.56, 40.84, 48.81, 60.38, 70.38 (d, J(PC) 5.5), 102.46,
2
2
103.55, 122.23, 126.29, 128.27, 128.45, 128.72, 128.81, 134.84, 138.69, 146.85, 152.84, 153.94,
31
155.04, 168.59; P NMR (CDCl3): δP 7.51 (s); HRMS (EI): m/z [M+H] calcd. for C31H40N5O5P:
593.65356. Found: 593.65438.
Diisopropyl
6-[5-(ethoxycarbonyl)-1,3-diphenyl-1H-pyrazolo[3,4-b]pyridin-4-ylamino]-
hexylphosphoramidate (8l). Oil; yield 52%; IR (KBr, νmax, cm-1): 3243 (m, νN-H), 2977 (m),
2930 (m), 1680 (s, νC=O), 1573 (s), 1502 (m), 1453 (m), 1373 (m), 1267 (m, νP=O), 1177 (m),
1
1107 (m), 990 (s, νP-O), 896 (w), 776 (w), 699 (w); H NMR (CDCl3): δH 1.19 and 1.25 (2d,
12H, 3J(HH) 6.0), 1.27 (m, 2H), 1.39 (t, 3H, 3J(HH) 7.1), 2.47 (dt, 1H, 3J(HH) 9.0 and 7.8), 2.79 (m,
2H), 2.88 (dt, 2H, 3J(HH) 8.6 and 5.6), 4.37 (q, 2H, 3J(HH) 6.9), 4.48 (dsep, 2H, 3J(HH) 6.0 and 3J(PH)
3
3
3
7.5), 7.31 (t, 1H, J(HH) 7.5), 7.49 (m, 5H), 7.75 (d, 2H, J(HH) 8.0), 8.20 (d, 2H, J(HH) 8.6), 8.90
(br t, 1H, J(HH) 5.6), 9.00 (s, 1H); 13C NMR (CDCl3): δC 14.16, 23.59 (d, J(PC) 4.4), 29.57,
41.87, 50.49, 50.55, 60.68, 70.77 (d, J(PC) 5.3), 103.30, 103.88, 122.40, 126.54, 128.52, 128.69,
3
3
2
31
128.82, 128.89, 134.52, 138.73, 146.80, 152.92, 155.45, 168.71; P NMR (CDCl3): δP 7.01 (s);
HRMS (EI): m/z [M+H] calcd. for C33H44N5O5P: 621.30801. Found: 621.30754.
Acknowledgements
We thank FAPERJ, CNPq and CAPES for financial support and the LDRX-UFF for data
collection of compound 8j.
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