Synthesis, crystal structure and biological activity of 5-(4-fluorophenyl)-N,Ndimethyl- 7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide

Article abstract of DOI:10.3184/174751916X14532123759818

The title compound, 5-(4-fluorophenyl)-N,N-dimethyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide, has been synthesised by condensation of dimethylamine with 5-(4-fluorophenyl)-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxylic acid. T

Full text of DOI:10.3184/174751916X14532123759818

JOURNAL OF CHEMICAL RESEARCH 2016
VOL. 40 FEBRUARY, 107–109
RESEARCH PAPER 107
Synthesis, crystal structure and biological activity of 5-(4-fluorophenyl)-N,N-
dimethyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide
a
a
b
a
c
a
Ju Liu , Duan-Zheng Song , Yan-Qiu Tian , Xin-Wei Zhang , Yue-Fei Bai and Dan Wang *
a
College of Pharmacy of Liaoning University, Key Laboratory of New Drug Research and Development of Liaoning Province, Shenyang, 110036, Liaoning,
P.R. China
b
College of Life Science of Liaoning University, Shenyang, 110036, Liaoning, P.R. China
c
Northeast Pharmaceutical Group Co., Ltd, Shenyang, 110027, Liaoning, P.R. China
The title compound, 5-(4-fluorophenyl)-N,N-dimethyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide, has been synthesised
by condensation of dimethylamine with 5-(4-fluorophenyl)-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxylic acid. This
intermediate was prepared from ethyl 5-amino-1H-pyrazole-4-carboxylate by cyclisation with 4,4,4-trifluoro-1-(4-fluorophenyl)butane-
1
,3-dione and then saponification with sodium hydroxide. The crystal structure of the title compound was determined. The compound
possesses distinct effective inhibition on the proliferation of some cancer cell lines.
Keywords: synthesis, X-ray diffraction, biological activity, anticancer agents
Pyrazolopyrimidines have attracted the attention of organic
chemists due to their biological and chemotherapeutic
importance. Among them, pyrazolo[1,5-a]pyrimidines are of
was performed on aluminium sheets pre-coated with silica gel (Merck,
Kiesel gel 60 F-254). H NMR spectra were recorded on a Bruker
1
1
AV-600 (or 500) in DMSO-d using TMS as an internal standard
6
interest as potential bioactive molecules. They are known to
exhibit a wide range of biological activities as, for example,
(chemical shifts in ppm). IR spectra were recorded in KBr pellets on
a PerkinElmer Spectrum One FTIR spectrometer. Crystal data were
obtained on a Bruker P4 X-diffractometer. Elemental analysis was
carried out on a Carlo Erba 1108 analyser. All solvents and reagents
were obtained from commercial sources and were used without
purification. Ethyl 5-aminopyrazole-4-carboxylate 1 was purchased
from Aldrich and 4,4,4-trifluoro-1-(4-fluorophenyl)butane-1,3-dione
2
–4
5
anticancer agents,
antimicrobial agents, antiepileptic
6
7
8
agents, anxiolytics, antidepressants, agents for treatment of
9
10
sleep disorders and oncolytics.
Our interest in fused pyrimidine heterocycles is a result of
the known biological activity of these systems reported in the
literature. In order to find novel bioactive compounds, several
new kinds of pyrazolopyrimidines have been synthesised
13
was obtained as reported.
Synthesis of 5-(4-fluorophenyl)-7-(trifluoromethyl)pyrazolo[1,5-a]
pyrimidine-3-carboxylic acid (4)
11,12
in our laboratory.
pyrazolo[1,5-a]pyrimidine, 5-(4-fluorophenyl)-N,N-dimethyl-
-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide,
We now report the synthesis of a new
A solution of ethyl 5-amino-1H-pyrazole-4-carboxylate (1) (15.5 g,
7
0.1 mol) and 4,4,4-trifluoro-1-(4-fluorophenyl)butane-1,3-dione
by a three-step synthesis. In order to confirm its structure
and investigate its stereoconfiguration, a single crystal of
the title compound was obtained and the molecular structure
(
23.4 g, 0.1 mol) in acetic acid (50 mL) was heated at reflux for 6 h.
After cooling to room temperature, the formed precipitate 3 was
filtered off, washed with water and dried: m.p. 167–169 °C; IR (KBr,
1
was determined by elemental analysis, IR spectroscopy, H
–1
cm ): 2965, 1697, 1634, 1594, 1570, 1466, 1397, 1327, 1198, 1171,
NMR spectroscopy and X-ray diffraction. The biological tests
suggested the compound displayed distinct effective inhibition
on the proliferation of cancer cell lines. The synthetic procedure
for the title compound is shown in Scheme 1.
1
1
027, 848, 778; H NMR (600 MHz, DMSO-d ): δ 8.75(s, 1H, ArH),
6
8.48 (m, 2H, ArH), 8.37 (s, 1H, ArH), 7.45 (m, 2H, ArH), 4.34 (q,
J = 7.2 Hz, 2H, CH ), 1.36 (t, J = 7.2 Hz, 3H, CH ).
2
3
The resulting ethyl carboxylate 3 was added to a mixture of NaOH
(
5.6 g, 0.14 mol) in EtOH/water (1:3) (120 mL) and the reaction
Experimental
Melting points (°C) were measured with a Koffler melting point
apparatus and are uncorrected. Thin-layer chromatography (TLC)
mixture was kept at 65 °C for 5 h. The mixture was cooled to room
temperature and acidified with concentrated HCl until pH 1 was
reached. The formed precipitate was filtered off, washed with water,
CF3
N
NH
NH2
O
O
N
N
AcOH, reflux
+
CF3
N
EtO
EtO
O
F
O
F
F
2
3
1
CF3
CF3
N
(CH ) NH HCl
N
1
) NaOH/ H O/ EtOH, 65°C
N
3 2
2
N
N
EDCI, DMAP, HOBT
DMF, RT
N
5
2) HCl
HO
N
O
F
O
4
Scheme 1 Synthetic route of the title compound.
*
Correspondent. E-mail: daxia1481@sina.com

108 JOURNAL OF CHEMICAL RESEARCH 2016
a
and recrystallised from MeCN to give: 20.6 g pure 5-(4-fluorophenyl)-
Table 1 Crystal data for the title compound 5
7
6
2
-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxylic acid (4) in
3.4% yield (two steps); m.p. 252–253 °C; IR (KBr, cm ): 3446, 2928,
Crystal size
Formula
fw
T/K
Crystal system
Space group
0.20 × 0.18 × 0.10 mm
C H F N O
352.30
293(2)
Triclinic
P –1
–1
16 12 4 4
856, 1672, 1655, 1601, 1564, 1457, 1406, 1337, 1235, 1200, 1161, 841,
1
5
58; H NMR (500 MHz, DMSO-d ): δ 8.52 (s, 1H, ArH), 8.50 (m, 2H,
6
ArH), 8.20 (s, 1H, ArH), 7.25 (d, J = 8.2 Hz, 2H, ArH), 2.35–2.55 (s,
1H, COOH); LC/MS m/z: 326 (M + 1). Anal. calcd for C H F N O : C
14 7 4 3 2
51.70, H 2.17, N 12.92; found C 51.61, H 2.21, N 12.83%.
a/Å
b/Å
c/Å
α/°
β/°
γ/°
V/Å
Z
Dc/g cm
8.1533(16)
9.775(2)
10.112(2)
95.02(3)
91.66(3)
93.43(3)
800.9(3)
2
Synthesis of 5-(4-fluorophenyl)-N,N-dimethyl-7-(trifluoromethyl)
pyrazolo[1,5-a]pyrimidine-3-carboxamide (5)
Under an N2 atmosphere,
trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxylic acid (4)
1.63 g, 5.00 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide
hydrochloride (EDCl) (1.16 g, 6.00 mmol)，1-hydroxybenzotriazole
a mixture of 5-(4-fluorophenyl)-7-
(
(
3
(
(
(
HOBT) (0.68 g, 5.00 mmol) and 4-dimethylaminopyridine (DMAP)
0.61 g, 5.00 mmol) in 50 mL dried N,N-dimethylformamide
DMF) was stirred at room temperature for 0.5 h and a solution of
–3
1.461
dimethylamine hydrochloride (0.49 g, 6.00 mmol) in 20 mL of dried
DMF was added. After the mixture was stirred for 10 h at room
temperature, it was was diluted with water (100 mL), extracted by
ethyl acetate three times (80 mL × 3), and dried over anhydrous
sodium sulfate. It was then filtered off and concentrated in vacuo to
give crude product, which was purified by column chromatography to
give 1.22 g of the title compound as: Yellow powder, yield: 69.1%; m.p.
F(000)
GOF on F
360
1.050
6565/2808
0.0609, 0.1101
0.1394, 0.1335
2
Reflection/unique
R ,wR [I > 2 (I)]
1
2
R ,wR (all data)
1
2
a
2
2
2
2 2 1/2
R = ∑(||F | – |F ||) / ∑|F | and wR = [∑w(F – F ) /∑w(F ) ] .
1
o
c
o
2
o
c
o
–1
170–173 °C; IR (KBr, cm ): 3055, 2933, 1632, 1618, 1569, 1533, 1514,
1
6
413, 1396, 1339, 1325, 1258, 1233, 1199, 1173, 1119, 838, 773, 760,
Table 2 Hydrogen bond lengths (Å) and bond angles (°)
1
85; H NMR (600 MHz, DMSO-d ): 8.54 (s, 1H, ArH), 8.41 (m, 2H,
6
D–H...A
d(D–H)
d(H...A)
d(D...A)
∠DHA
102.25
165.86
ArH)，8.26 (s, 1H, ArH), 7.42 (m, 2H, ArH), 3.14 (s, 3H, CH ), 3.06 (s,
3
C(14)-F(4)…F(4) 1.378
C(13)-H(13)…O(1) 0.930
2.919
2.405
3.482
3.314
3H, CH ). Anal. calcd for C H F N O: C 54.55, H 3.43, N 15.90; found
3 16 12 4 4
C 54.46, H 3.45, N 15.83%
Crystal data structure determination
a
The white powder of the title 5 compound was dissolved in ethanol/
acetone mixed solvents = 1:1 (v/v). After slowly evaporating the
solvents for several days, some single crystals suitable for X-ray
Table 3 In vitro anticancer activity test of 5-(4-fluorophenyl)-N,N-dimethyl-
7
-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamide (5) on BGC-
823 and HepG-2 cell lines
–1
%
inhibition at 40 mg mL in
analysis were obtained.
A yellow crystal (C H F N O) with
16 12 4 4
Compound
dimensions of 0.20 × 0.18 × 0.10 mm was selected for data collection
which was performed on a Bruker P4 diffractometer equipped with
a graphite-monochromatic Cu Kα radiation (λ = 0.71073 Å) by
using an ω scan mode at 298(2) K. A total of 6565 reflections were
collected in the range of 2.5 < θ < 25.0° (index ranges: –9 < h <9,
BGC-823
HepG-2
5-(4-Fluorophenyl)-N,N-dimethyl-7-
(
trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-
74.9
38.5
carboxamide
Sorafenib tosylate
81.4
61.9
a
Test MTT colourimetric assay in BGC-823 and HepG-2 human cancer cell lines.
–11 < k < 11, –11 < l < 12) and 2808 were independent (Rint = 0.090),
of which 864 observed reflections with I > 2σ (I) were used in
the structure determination and refinements. The structure was
14
solved by direct methods with the SHELXS-97 program and
expanded by the Fourier technique. The non-hydrogen atoms were
refined anisotropically. The hydrogen atoms bound to carbon were
determined with theoretical calculations and those attached to nitrogen
and oxygen were determined with successive difference Fourier
syntheses. The structure was refined by the full-matrix least-squares
compound exhibited significant inhibitory activity in the BGC-823 cell
line and HepG-2 cell lines. The title compound was slightly less potent
than sorafenib tosylate in the BGC-823 cell line but obviously less
potent than sorafenib tosylate in the HepG-2 cell line. The percentage
inhibition determined is reported in Table 3. Further structure
optimisation may result in more active anticancer compounds.
2
14
techniques on F with SHELXL-97. The final refinement gave the
2
2
2
Results and discussion
final R = 0.053 and wR = 0.134 (w = 1/ [σ (Fo ) + (0.020P) ]) where
2
2
P = (Fo + 2Fc )/3), S = 1.05, (Δ/σ) max = 0.002, (Δρ) max = 0.24
The named compound 5 was prepared according to Scheme 1.
–3
1
and (Δρ) min = –0.28e/Å . All calculations were performed using
the Crystal Structure crystallographic software package except for
the refinement. Crystallographic data and experimental details of
structural analyses for compound 5 are summarised in Table 1. The
hydrogen bond data of title compound is listed in Table 2. CCDC1433227
contains the supplementary crystallographic data for this paper. The data
can be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif
The elemental analyses, IR (Fig. S1), H NMR (Fig. S2) and
X-ray diffraction data for the product are in good agreement
with the structure of the title compound. A perspective view of
the crystal structure and packing diagram are shown in Figs 1
and 2. The F(4)–C(14), N(2)–N(3) and N(4)–C(10) bonds are
1.379(4), 1.376(4) and 1.334(4) Å respectively. The bond
length of O(1)–C(3) is 1.247(4)Å which is typical for a C=O
double bond. The dihedral angle between the benzene ring and
pyrazolopyrimidine is 9.98°. Weak intermolecular hydrogen
bonds C(14)–F(4)…F(4) and C(13)–H(13)…O(1) are also
present as shown in Table 2. These interactions are responsible
for maintaining the three-dimensional crystal structure.
In vitro anticancer activity test of the title compound on BGC-823 and
HepG-2 cell lines
The named compound 5 was evaluated for its in vitro cytotoxic activity
against two cancer cell lines (BGC-823 and HepG-2) by the MTT-
based assay using sorafenib tosylate as a positive control (Table 3).
Biological activity determination results indicated that the title
In addition, a preliminary bioassay indicated that the title
compound possessed some anticancer activity and the activity

JOURNAL OF CHEMICAL RESEARCH 2016 109
Fig. 1 The structure of C H F N O (5) with all non-H atoms labelled and
16
12
4
4
ellipsoids drawn at the 30% probability level.
data are still waiting for further analysis. Further studies
on structural optimisation and biological activities of these
derivatives are underway in our laboratory and will be reported
in the future.
Electronic Supplementary Information
Fig. 2 Packing diagram of C H F N O (5).
16
12
4
4
1
The ESI (IR and H NMR spectra) is available through:
stl.publisher.ingentaconnect.com/content/stl/jcr/supp-data
4
5
6
7
8
9
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The authors are grateful for the financial support of Shenyang
Science & Technology project (project no. F13-316-1-63),
General project of Liaoning Provincial Department of
Education (project no. L2015201) and Natural Science
Funds for Young Scholar of Liaoning University (project no.
LDQN201436).
P.B. O’Donnell and W.J. Thiele, US Patent 6,384,221, 2002; Chem. Abstr.,
Received 26 October 2015; accepted 29 December 2015
Paper 1503675 doi: 10.3184/174751916X14532123759818
Published online: 29 January 2016
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