Synthesis, characterization and in vitro antitumor activity of novel Schiff bases containing pyrazole group

Article abstract of DOI:10.14233/ajchem.2014.16893

A series of novel Schiff base compounds containing pyrazole group were synthesized with pyrazole aldehyde and benzene hydrazine or pyrazole aldehyde and phenylhydrazine hydrochloride as the starting materials. As-synthesized Schiff base compounds were cha

Full text of DOI:10.14233/ajchem.2014.16893

Asian Journal of Chemistry; Vol. 26, No. 24 (2014), 8309-8313
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16893
Synthesis, Characterization and in vitro Antitumor Activity of
Novel Schiff Bases Containing Pyrazole Group
1
1
1
TIEGANG REN , JIE WANG , GUIHUI LI2,* andYONGZHE LI
1Fine Chemistry and Engineering Research Institute, College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, P.R. China
2Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004, P.R. China
*Corresponding author: Tel: +86 378 2866141; E-mail: rtg@henu.edu.cn
Received: 19 December 2013;
Accepted: 3 April 2014;
Published online: 1 December 2014;
AJC-16351
A series of novel Schiff base compounds containing pyrazole group were synthesized with pyrazole aldehyde and benzene hydrazine or
pyrazole aldehyde and phenylhydrazine hydrochloride as the starting materials.As-synthesized Schiff base compounds were characterized
by means of nuclear magnetic resonance spectroscopy, infrared spectrometry, mass spectrometry and elemental analysis. Moreover the in
vitro antitumor activity of compounds B2 and B4 against K562 (human leukemia cell line) was evaluated using MTT assay method.
Results show that the compounds can inhibit K562 tumor cell's growth and generation.
Keywords: Schiff base, Synthesis, Characterize, in vitro Antitumor activity, Heterocyclic compounds, Pyrazole group.
400 spectrometer in the presence of tetramethylsilane as an
internal standard. Elemental analysis was conducted with a
PE2400 elemental analysis apparatus.
INTRODUCTION
Schiff base is a kind of organic compounds with special
physical and chemical properties1. For the strong coordination
ability, Schiff base can form complexes with metal or rare
earth ions and is a good extractant and chelating agent2-4. At
the same time, with strong antibacterial and antiviral ability,
Schiff base has been widely used in biology, medicine, metal-
lurgy, dye and photoelectric functional materials fields5-8. On
the other hand, as a kind of efficient extractants and chelators
of metal ions9-13, pyrazole derivatives have aroused wide
concern in biology, medicine, pesticide, analytical applications.
Furthermore, the excellent photoelectric properties and carrier
transmission capacity of pyrazole derivatives add to their wide
use in photoelectric functional materials and organic light-
emitting diodes (OLED)14,15. Therefore, research of pyrazole
based on Schiff base compounds also appears more and more
important and valuable. In this article we report a simple
procedure for synthesizing Schiff base containing pyrazole
group.
The in vitro antitumor activity of compounds B2 and B4
was evaluated in K562 (human leukemia cell line) using MTT
(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide) assay method (amonafide as reference substance,
10 and 30 µmol/L). The inhibition rate was calculated from
plotted results using untreated cells as 100 %.
All chemicals and solvents are of commercial reagent grade
and used without further purification. Besides, 1-arylpyrazole-
4-carbaldehyde was prepared according to procedures avail-
able elsewhere. Known structures of as-synthesized products
were verified by comparing their data with those reported in
the literature16,17
.
Synthesis of Schiff base compounds: 5 mmol of 1-aryl-
pyrazole-4-carbaldehyde and 5 mmol of benzene hydrazine
or phenylhydrazine hydrochloride were completely dissolved
in 35 mL methanol, heated to 80 °C, refluxed for 2 h, cooled to
room temperature and placed overnight. After suction filtered
and dried, crude mixed products were obtained and purified
by recrystallizing in the mixed solvent of EtOH and CH2Cl2
EXPERIMENTAL
Mass spectra (MS) were determined with an Agilent
1100LC-MS mass spectrometer. Infrared (IR) spectra of as-
obtained products within 4000-400 cm-1 were recorded with a
Nicolet 170 SXFT-IR spectrometer (mixed with KBr and
pressed into pellets). Nuclear magnetic resonance (1H NMR)
spectra in (CD3)2C=O solvent were recorded with an INOVA-
(VEtOH:VCH Cl2 = 1:3).
3-Methyl-1-phenyl-4-[(2-(p-tolyl)hydrazono)methyl]-
2
1H-pyrazol-5(4H)-one (A1):Yellow solid 0.70 g, yield: 46 %.
1
APCI-MS (m/z) calcd. (M–) 306.3, found: 304.9. H NMR
spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.19 (3H, s,
CH3), 2.47 (3H, s, CH3), 6.89 (2H, d, J = 8.4,Ar-H), 7.02 (2H,

8310 Ren et al.
Asian J. Chem.
d, J = 8.2,Ar-H), 7.46 (1H, s, N = C-H), 7.51-7.62 (5H, m,Ar-
H), 7.79 (1H, s, N-H), 10.22 (1H, s, O-H). IR spectrum (thin
layer), ν, cm-1: 3236 (N-H), 1588 (C=N), 1501, 1476 (C=C),
1275 (C-N). Anal. calcd.: C, 69.85; H, 5.52; N, 19.17. Found:
C, 69.74; H, 5.61; N, 19.13 %.
g, yield: 70 %. APCI-MS (m/z) calcd. (M+) 345.2, found: 346.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.48
(3H, s, CH3), 6.74 (1H, dd, J = 7.5,1.6, Ar-H), 6.89 (1H, d, J =
7.4, Ar-H), 6.98 (1H, t, J = 2.0, Ar-H), 7.22 (1H, t, J = 8.1, Ar-
H), 7.48 (1H, s, N=C-H), 7.53-7.60 (5H, m, Ar-H), 7.85 (1H, s,
N-H). IR spectrum (thin layer), ν, cm-1: 3234(N-H), 1598 (C=N),
1501, 1474 (C=C), 1246 (C-N). Anal. calcd.: C, 59.14; H, 4.09;
N, 16.23. Found: C, 59.10; H, 4.14; N, 16.20 %.
4-[{2-(4-Fluorophenyl)hydrazono}methyl]-3-methyl-1-
phenyl-1H-pyrazol-5(4H)-one (A2): Yellow solid 0.85 g,
yield: 55 %. APCI-MS (m/z) calcd. (M–) 310.3, found: 308.8.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.48 (3H, s, CH3), 6.93-7.01 (2H, m, Ar-H), 7.04-7.09 (2H,
m,Ar-H), 7.48 (1H, s, N=C-H), 7.52-7.66 (5H, m,Ar-H), 7.82
(1H, s, N-H), 10.30 (1H, s, O-H). IR spectrum (thin layer), ν,
cm-1: 3244 (N-H), 1587 (C=N), 1503, 1477(C=C), 1273 (C-N).
Anal. calcd.: C, 65.80; H, 4.87; N, 18.05. Found: C, 65.87; H,
4.95; N, 18.00 %.
4-[{2-(4-Bromophenyl)hydrazono}methyl]-5-chloro-3-
methyl-1-phenyl-1H-pyrazole (B3): Deep yellow solid 1.10
g, yield: 56 %. APCI-MS (m/z) calcd. (M + Na)+ 389.6, found:
1
412.1. H NMR spectrum (400 MHz, DMSO-d6), δ, ppm
(J, Hz): 2.60 (3H, s, CH3), 6.94 (2H, d, J = 7.5, Ar-H), 7.36
(2H, d, J = 8.7, Ar-H), 7.41(1H, s, N=C-H), 7.47-7.52 (3H, m,
Ar-H), 7.54-7.57 (2H, m,Ar-H), 7.70 (1H, s, N-H). IR spectrum
(thin layer), ν, cm-1: 3236 (N-H), 1596 (C=N), 1500, 1470
(C=C), 1253 (C-N). Anal. calcd.: C, 52.40; H, 3.62; N, 14.38.
Found: C, 52.31; H, 3.71; N, 14.37 %.
4-[{2-(3-Chlorophenyl)hydrazono}methyl]-3-methyl-
1-phenyl-1H-pyrazol-5(4H)-one (A3): Yellow solid 0.80 g,
yield: 49 %. APCI-MS (m/z) calcd. (M–) 326.7, found: 324.9.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.49 (s, 3H, CH3), 6.75 (1H, dd, J = 7.8, 1.2, Ar-H), 6.90 (1H,
d, J = 8.2, Ar-H), 6.99 (1H, t, J = 1.9, Ar-H), 7.23 (1H, t, J =
8.0, Ar-H), 7.49 (1H, s, N=C-H), 7.53-7.63 (5H, m, Ar-H),
7.86 (1H, s, N-H), 10.53(1H, s, O-H). IR spectrum (thin layer),
ν, cm-1: 3234 (N-H), 1603 (C=N), 1502, 1479 (C=C), 1271
(C-N). Anal. calcd.: C, 62.84; H, 4.63; N, 17.15. Found: C,
62.79; H, 4.71; N, 17.08 %.
5-Chloro-3-methyl-4-[{2-(4-nitrophenyl)hydrazono}-
methyl]-1-phenyl-1H-pyrazole (B4): Brick red solid 1.35 g,
yield: 76 %. APCI-MS (m/z) calcd. (M+) 355.7, found: 356.2.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.50 (3H, s, CH3), 7.08 (2H, d, J = 7.3, Ar-H), 7.50 (1H, s,
N=C-H), 7.54-7.61 (5H, m, Ar-H), 8.04 (1H, s, N-H), 8.13
(2H, d, J = 8.8, Ar-H). IR spectrum (thin layer), ν, cm-1: 3237
(N-H), 1601 (C=N), 1554, 1382 (NO2), 1501, 1476 (C=C),
1241 (C-N). Anal. calcd.: C, 57.39; H,3.97; N, 19.68. Found:
C, 57.30; H, 4.01; N, 19.65 %.
4-[{2-(4-Bromophenyl)hydrazono}methyl]-3-methyl-
1-phenyl-1H-pyrazol-5(4H)-one (A4): Yellow solid 0.90 g,
yield: 48 %. APCI-MS (m/z) calcd. (M–) 371.2, found: 369.8.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.48 (3H, s, CH3), 6.91-6.99 (2H, m, Ar-H), 7.33-7.39 (2H,
m,Ar-H), 7.48 (1H, s, N=C-H), 7.53-7.61 (5H, m,Ar-H), 7.84
(1H, s, N-H), 10.46 (1H, s, O-H). IR spectrum (thin layer), ν,
cm-1: 3230 (N-H), 1591 (C=N), 1492, 1471 (C=C), 1278 (C-N).
Anal. calcd.: C, 55.00; H, 4.07; N, 15.09. Found: C, 54.89; H,
4.13; N, 15.05 %.
3,5-Dimethyl-1-phenyl-4-[(2-phenylhydrazono)methyl]-
1H-pyrazole (C1): Deep yellow solid 0.50 g, yield: 34 %.
1
APCI-MS (m/z) calcd. (M+) 290.3, found: 291.2. H NMR
spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.38 (3H, s,
CH3), 2.43 (3H, s, CH3), 6.68 (1H, t, J = 7.3, Ar-H), 6.96 (2H,
d, J = 7.7, Ar-H), 7.18 (2H, t, J = 7.8, Ar-H), 7.41 (1H, s, N=C-
H), 7.51-7.54 (5H, m, Ar-H), 7.90 (1H, s, N-H). IR spectrum
(thin layer), ν, cm-1: 3236 (N-H), 1600 (C=N), 1504, 1428
(C=C), 1263 (C-N). Anal. calcd.: C, 74.45; H, 6.25; N, 19.30.
Found: C, 74.39; H, 6.18; N, 19.27 %.
3-Methyl-4-[{2-(4-nitrophenyl)hydrazono}methyl]-1-
phenyl-1H-pyrazol-5(4H)-one (A5): Deep red solid 0.75 g,
yield: 44 %. APCI-MS (m/z) calcd. (M–) 337.3, found: 335.9.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.37 (3H, s, CH3), 6.98 (2H, d, J = 8.7, Ar-H), 7.17-7.26 (1H,
m, Ar-H), 7.42 (2H, d, J = 8.2, Ar-H), 7.45 (1H, s, N=C-H),
7.80 (2H, d, J = 7.8, Ar-H), 8.09 (2H, s, Ar-H), 8.11 (1H, s,
N-H), 10.93 (1H, s, O-H). IR spectrum (thin layer), ν, cm-1:
3236 (N-H), 1596 (C=N), 1552, 1372 (NO2), 1499, 1478
(C=C), 1277 (C-N). Anal. calcd.: C, 60.53; H, 4.48; N, 20.76.
Found: C, 60.45; H, 4.52; N, 20.71 %.
4-[{2-(4-Fluorophenyl)hydrazono}methyl]-3,5-
dimethyl-1-phenyl-1H-pyrazole (C2): Deep yellow solid
0.75 g, yield: 49 %. APCI-MS (m/z) calcd. (M+) 308.3, found:
1
309.1. H NMR spectrum (400 MHz, DMSO-d6), δ, ppm
(J, Hz): 2.37 (3H, s, CH3), 2.42 (3H, s, CH3), 6.93 (2H, dd, J =
9, 4.8, Ar-H), 7.03 (2H, t, J = 8.9, Ar-H), 7.40 (1H, s, N=C-
H), 7.46-7.56 (5H, m, Ar-H), 7.89 (1H, s, N-H). IR spectrum
(thin layer), ν, cm-1: 3222 (N-H), 1596 (C=N), 1502, 1425
(C=C), 1272 (C-N). Anal. calcd.: C, 70.11; H, 5.56; N, 18.17.
Found: C, 70.05; H, 5.63; N, 18.01 %.
5-Chloro-4-[{2-(4-fluorophenyl)hydrazono}methyl]-3-
methyl-1-phenyl-1H-pyrazole (B1): Deep yellow solid 0.55 g,
yield: 33 %.APCI-MS (m/z) calcd. (M+) 328.7, found: 329.1. 1H
NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.60
(3H, s, CH3), 6.99 (4H, d, J = 6.7, Ar-H), 7.41 (1H, s, N=C-H),
7.46-7.53 (3H, m, Ar-H), 7.54-7.57 (2H, m, Ar-H), 7.70 (1H, s,
N-H). IR spectrum (thin layer), ν, cm-1: 3230 (N-H), 1597 (C=N),
1502, 1478 (C=C), 1246 (C-N). Anal. calcd.: C, 62.10; H, 4.29;
N, 17.04. Found: C, 62.01; H, 4.37; N, 17.00 %.
4-[{2-(3-Chlorophenyl)hydrazono}methyl]-3,5-
dimethyl-1-phenyl-1H-pyrazole (C3): Deep yellow solid
0.55 g, yield: 34 %. APCI-MS (m/z) calcd. (M+) 324.8, found:
325.1. 1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J,
Hz): 2.37 (3H, s, CH3), 2.43 (3H, s, CH3), 6.69 (1H, s, Ar-H),
6.86 (1H, s, Ar-H), 6.95 (1H, s, Ar-H), 7.19 (1H, s, Ar-H),
7.42 (1H, s, N=C-H), 7.48-7.52 (5H, m, Ar-H), 7.91 (1H, s,
N-H). IR spectrum (thin layer), ν, cm-1: 3224 (N-H), 1597
(C=N), 1504, 1430 (C=C), 1265 (C-N). Anal. calcd.: C, 66.56;
H, 5.28; N, 17.25. Found: C, 66.50; H, 5.29; N, 17.21 %.
5-Chloro-4-[{2-(3-chlorophenyl)hydrazono}methyl]-3-
methyl-1-phenyl-1H-pyrazole (B2): Deep yellow solid 1.20

Vol. 26, No. 24 (2014)
Synthesis and Antitumor Activity of Novel Schiff Bases Containing Pyrazole Group 8311
4-[{2-(4-Bromophenyl)hydrazono}methyl]-3,5-
dimethyl-1-phenyl-1H-pyrazole (C4): Deep yellow solid 1.05
g, yield: 57 %.APCI-MS (m/z) calcd. (M+) 369.2, found: 370.1.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.37 (3H, s, CH3), 2.42 (3H, s, CH3), 6.90 (2H, t, J = 5.9, Ar-
H), 7.32 (2H, t, J = 5.9, Ar-H), 7.41 (1H, s, N=C-H), 7.48-
7.54 (5H, m,Ar-H), 7.90 (1H, s, N-H). IR spectrum (thin layer),
ν, cm-1: 3236 (N-H), 1596 (C=N), 1500, 1427 (C=C), 1266
(C-N). Anal. calcd.: C, 58.55; H, 4.64; N, 15.17. Found:
C, 58.50; H,4.71; N, 15.12 %.
(C=N), 1496, 1426 (C=C), 1252 (C-N). Anal. calcd.: C, 48.24;
H, 3.60; N, 12.50. Found: C, 48.20; H, 3.69; N, 12.47 %.
1-(4-Bromophenyl)-3,5-dimethyl-4-[{2-(4-nitrophenyl)-
hydrazono}methyl]-1H-pyrazole (D5): Brick red solid 1.90
g, yield: 92 %. APCI-MS (m/z) calcd. (M + Na)+ 437.3, found:
437.1. 1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J,
Hz): 2.49 (3H, s, CH3), 2.51 (3H, s, CH3), 7.01 (2H, t, J = 7.2,
Ar-H), 7.31-7.35 (2H, m, Ar-H), 7.60-7.64 (2H, m, Ar-H),
7.84 (1H, s, N=C-H), 7.91 (1H, s, N-H), 8.81 (2H, d, J = 9.3,
Ar-H). IR spectrum (thin layer), ν, cm-1: 3231 (N-H), 1606
(C=N), 1553, 1378 (NO2), 1499, 1427 (C=C), 1254 (C-N).
Anal. calcd.: C, 52.19; H, 3.89; N, 16.91. Found: C, 52.11; H,
3.99; N, 16.84 %.
3,5-Dimethyl-4-[{2-(4-nitrophenyl)hydrazono}methyl]-
1-phenyl-1H-pyrazole (C5): Brick red solid 1.40 g, yield:
1
83 %. APCI-MS (m/z) calcd. (M+) 335.3, found: 336.1. H
NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.40
(3H, s, CH3), 2.45 (3H, s, CH3), 7.04 (2H, s, Ar-H), 7.42 (1H,
s, C=N-H), 7.48-7.59 (5H, m, Ar-H), 8.10 (2H, s, Ar-H), 8.12
(1H, s, N-H). IR spectrum (thin layer), ν, cm-1: 3231 (N-H),
1595 (C=N), 1553, 1378 (NO2), 1503, 1432 (C=C), 1262
(C-N). Anal. calcd.: C, 64.47; H, 5.11; N, 20.88. Found: C,
64.45; H, 5.10; N, 20.78 %.
3,5-Dimethyl-1-(4-nitrophenyl)-4-[(2-phenyl hydra-
zono)methyl]-1H-pyrazole (E1): Deep red solid 1.10 g, yield:
1
66 %. APCI-MS (m/z) calcd. (M+) 335.4, found: 336.7. H
NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.42
(3H, s, CH3), 2.55 (3H, s, CH3), 6.69 (1H, t, J = 7.3, Ar-H),
6.96 (2H, d, J = 7.6, Ar-H), 7.12-7.29 (2H, m, Ar-H), 7.83-
7.87 (2H, m, Ar-H), 7.89 (1H, s, N=C-H), 8.30-8.41 (2H, m,
Ar-H), 10.11 (1H, s, N-H). IR spectrum (thin layer), ν, cm-1:
3235 (N-H), 1600 (C=N), 1551, 1376 (NO2), 1503, 1427
(C=C), 1262 (C-N). Anal. calcd.: C, 64.47; H, 5.11; N, 20.88.
Found: C, 64.38; H, 5.18; N, 20.82 %.
1-(4-Bromophenyl)-3,5-dimethyl-4-[(2-phenyl hydra-
zono)methyl]-1H-pyrazole (D1): Yellow solid 1.55 g, yield:
1
84 %. APCI-MS (m/z) calcd. (M+) 369.3, found: 370.1. H
NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.48
(3H, s, CH3), 2.49 (3H, s, CH3), 6.85 (1H, s, Ar-H), 7.04 (3H,
s, Ar-H), 7.31-7.35 (3H, m, Ar-H), 7.58-7.60 (2H, m, Ar-H),
7.61 (1H, s, N=C-H), 7.75 (1H, s, N-H). IR spectrum (thin
layer), ν, cm-1: 3231 (N-H), 1600 (C=N), 1496, 1425 (C=C),
1255 (C-N). Anal. calcd.: C, 58.55; H, 4.64; N, 15.17. Found:
C, 58.51; H, 4.69; N, 15.07 %.
3,5-Dimethyl-1-(4-nitrophenyl)-4-[{2-(p-tolyl)hydra-
zono}methyl]-1H-pyrazole (E2): Deep red solid 1.30 g, yield:
1
74 %. APCI-MS (m/z) calcd. (M+) 349.4, found: 350.2. H
NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz): 2.19
(3H, s, CH3), 2.40 (3H, s, CH3), 2.55 (3H, s, CH3), 6.87 (2H,
d, J = 8.4, Ar-H), 7.00 (2H, d, J = 8.2, Ar-H), 7.83 (1H, s,
N=C-H), 7.85-7.89 (2H, m, Ar-H), 8.31-8.39 (2H, m, Ar-H),
9.98 (1H, s, N-H). IR spectrum (thin layer), ν, cm-1: 3236
(N-H), 1595 (C=N), 1550, 1380 (NO2), 1506, 1428 (C=C),
1260 (C-N). Anal. calcd.: C, 65.32; H, 5.48; N, 20.04. Found:
C, 65.25; H, 5.51; N, 20.07 %.
1-(4-Bromophenyl)-3,5-dimethyl-4-[{2-(p-tolyl)
hydrazono}methyl]-1H-pyrazole (D2): Yellow solid 1.45 g,
yield: 76 %. APCI-MS (m/z) calcd. (M+) 383.3, found: 384.0.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.18 (3H, s, CH3), 2.36 (3H, s, CH3), 2.43 (3H, s, CH3), 6.85
(2H, d, J = 8.4, Ar-H), 6.98 (2H, t, J = 9.1, Ar-H), 7.47-7.50
(2H, m, Ar-H), 7.69 (1H, s, N=C-H), 7.70-7.77 (2H, m, Ar-
H), 7.84 (1H, s, N-H). IR spectrum (thin layer), ν, cm-1: 3235
(N-H), 1607 (C=N), 1498, 1426 (C=C), 1254 (C-N). Anal.
calcd.: C, 49.54; H, 5; N, 14.62. Found: C, 49.46; H, 5.07; N,
14.67 %.
4-[{2-(4-Fluorophenyl)hydrazono}methyl]-3,5-
dimethyl-1-(4-nitrophenyl)-1H-pyrazole (E3): Deep red
solid 1.35 g, yield: 76 %. APCI-MS (m/z) calcd. (M+) 353.4,
1
found: 354.2. H NMR spectrum (400 MHz, DMSO-d6), δ,
ppm (J, Hz): 2.40 (3H, s, CH3), 2.54 (3H, s, CH3), 6.92-6.97
(2H, m, Ar-H,), 7.00-7.09 (2H, m, Ar-H), 7.81-7.86 (2H, m,
Ar-H), 7.87 (1H, s, N=C-H), 8.30-8.40 (2H, m, Ar-H), 10.09
(1H, s, N-H). IR spectrum (thin layer), ν, cm-1: 3235 (N-H),
1594 (C=N), 1553, 1370 (NO2), 1504, 1430 (C=C), 1267 (C-
N).Anal. calcd.: C, 61.18; H, 4.56; N, 19.82. Found: C, 61.11;
H, 4.59; N, 19.77 %.
1-(4-Bromophenyl)-4-[{2-(4-fluorophenyl)hydrazono}-
methyl]-3,5-dimethyl-1H-pyrazole (D3): Yellow solid 1.30
g, yield: 67 %.APCI-MS (m/z) calcd. (M+) 387.3, found: 388.1.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.36 (3H, s, CH3), 2.43 (3H, s, CH3), 6.88-6.98 (2H, m,Ar-H),
7.02 (2H, m, Ar-H), 7.48 (2H, t, J = 7.9, Ar-H), 7.69 (1H, s,
N=C-H), 7.70-7.77 (2H, m, Ar-H), 7.88 (1H, s, N-H). IR
spectrum (thin layer), ν, cm-1: 3233 (N-H), 1606 (C=N), 1500,
1426 (C=C), 1253 (C-N). Anal. calcd.: C, 55.83; H, 4.16; N,
14.47. Found: C, 55.79; H, 4.19; N, 14.39 %.
4-[{2-(3-Chlorophenyl)hydrazono}methyl]-3,5-dimethyl-
1-(4-nitrophenyl)-1H-pyrazole (E4): Deep red solid 1.25 g,
yield: 68 %. APCI-MS (m/z) calcd. (M+) 369.8, found: 370.1.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.40 (3H, s, CH3), 2.54 (3H, s, CH3), 6.88-6.98 (2H, m,Ar-H),
7.00-7.10 (2H, m, Ar-H), 7.81-7.86 (2H, m, Ar-H), 7.87 (1H,
s, N=C-H), 8.30-8.39 (2H, m, Ar-H), 10.09 (1H, s, N-H). IR
spectrum (thin layer), ν, cm-1: 3234 (N-H), 1594 (C=N), 1556,
1386 (NO2), 1506, 1429 (C=C), 1268 (C-N). Anal. calcd.: C,
58.46; H, 4.36; N, 18.94. Found: C, 58.45; H, 4.39; N, 18.91 %.
4-[{2-(4-Bromophenyl)hydrazono}methyl]-3,5-dimethyl-
1-(4-nitrophenyl)-1H-pyrazole (E5): Deep red solid 1.25 g,
yield: 60 %. APCI-MS (m/z) calcd. (M+) 414.5, found: 415.3.
1-(4-Bromophenyl)-4-[{2-(4-bromophenyl)hydrazono}-
methyl]-3,5-dimethyl-1H-pyrazole (D4): Yellow solid 1.50
g, yield: 67 %. APCI-MS (m/z) calcd. (M + Na)+ 448.2, found:
471.8. 1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J,
Hz): 2.36 (3H, s, CH3), 2.42 (3H, s, CH3), 6.84-6.98 (2H, m,
Ar-H), 7.26-7.41 (2H, m, Ar-H), 7.45-7.57 (2H, m, Ar-H),
7.69 (1H, s, N=C-H), 7.71-7.75 (2H, m, Ar-H), 7.88 (1H, s,
N-H). IR spectrum (thin layer), ν, cm-1: 3236 (N-H), 1594

8312 Ren et al.
Asian J. Chem.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.50 (3H, s, CH3), 2.60 (3H, s, CH3), 6.93-7.00 (2H, m,Ar-H),
7.35-7.37 (2H, m, Ar-H), 7.67-7.70 (2H, m, Ar-H), 7.73 (1H,
s, N=C-H), 8.35-8.38 (2H, m, Ar-H),10.05 (1H, s, N-H). IR
spectrum (thin layer), ν, cm-1: 3231 (N-H), 1601 (C=N), 1553,
1378 (NO2), 1503,1427 (C=C), 1263 (C-N). Anal. calcd.: C,
52.19; H, 3.89; N, 16.91. Found: C, 52.13; H, 3.97; N, 16.88 %.
3,5-Dimethyl-1-(4-nitrophenyl)-4-[{2-(4-nitrophenyl)-
hydrazono}methyl]-1H-pyrazole (E6): Brick red solid 1.40
g, yield: 74 %.APCI-MS (m/z) calcd. (M+) 380.4, found: 381.5.
1H NMR spectrum (400 MHz, DMSO-d6), δ, ppm (J, Hz):
2.44 (3H, s, CH3), 2.57 (3H, s, CH3), 7.05 (2H, d, J = 8, Ar-H),
7.82-7.93 (2H, m, Ar-H), 8.10-8.11 (2H, m, Ar-H), 8.13 (1H,
s, N=C-H), 8.30-8.45 (2H, m, Ar-H), 11.26 (1H, s, N-H). IR
spectrum (thin layer), ν, cm-1: 3236 (N-H), 1596 (C=N), 1556,
1387 (NO2), 1502, 1427 (C=C), 1266 (C-N). Anal. calcd.: C,
56.84; H, 4.24; N, 22.10. Found: C, 56.80; H, 4.29; N, 22.02 %.
The existence of electron-withdrawing substituent on the
pyrazole ring is beneficial to the reaction and the experimental
results show that the reaction is easier and the yield of the
target compounds is higher when R1 = Cl and R3 = F, Cl, Br
and -NO2 as compared with the electron-donating substituent
on the pyrazole ring. For R2 the existence of electron-donating
substituent is disadvantageous to the reaction, but it's easier for
product to separate out from the reaction system when R2 = -NO2.
Structural characterization: The structure of target
1
compounds have been characterized by means of H NMR,
FT-IR, MS and elemental analysis. In the 1H NMR spectrum,
it was found that the N=C-H chemical shift was at 7.40-8.13
(7.45-7.49 for A-series; 7.40-7.50 for B-series; 7.40-7.42 for
C-series; 7.61-7.84 for D-series; 7.73-8.13 for E-series), is a
singlet; it can be seen that the data clearly are divided into two
groups and have small difference for it, the results illustrate
that R3 has certain influence to the chemical shift of N=C-H
but these influence is very less. ForA-series the chemical shift
of O-H is located in the scope of 10.22 to 10.93 with a strong
singlet. The N-H appeared in the range of 7.69 to 8.12 (7.79-
8.11 for A- series; 7.69-8.04 for B-series; 7.87-8.12 for C-
series; 7.75-7.91 for D-series) and 9.98-11.26 for E-series.
The abnormal of E-series can be interpreted as the influence
of the intermolecular hydrogen bond. In the IR spectrum, the
absorption of N-H peak was within the scope of 3237-3222
cm-1; The stretching vibration absorption of C=N appeared in
the range of 1607-1587 cm-1; 1506-1425 cm-1 was the scope
of absorption peaks of aromatic ring skeleton; 1278-1241 cm-1
belonged to the vibration absorption peak of C-N. And it
appeared two obviously characteristic absorption peaks, in
1556-1550 and 1382-1370 cm-1, respectively for the comp-
ounds that containing the substituent of -NO2.
RESULTS AND DISCUSSION
These Schiff base compounds were synthesized by conden-
sation reaction with 1-arylpyrazol-4-carbaldehyde and benzene
hydrazine or phenylhydrazine hydrochloride as the starting
materials (Fig.1). The phenylhydrazine hydrochloride can
dissociate by weak base (e.g., CH3COONa), but it was found
that the post processing of the reaction would become very
complex after adding CH3COONa and the products were
difficult to separate out from the reaction system. Generally,
weak acid can be used as a catalyst in this reaction, however,
it was found that it is disadvantageous to the separation of
products as adding acid and phenylhydrazine hydrochloride
as the substrate maybe enhance the acidity of reaction system,
so there is no other acid has been added as catalyst. In the
meantime, the results showed that we can get good yields and
pure products in the presence of methanol as the solvent and
refluxing 2 h under 80 °C. It is relatively complex to the
purification of Schiff base compounds, for the Schiff base can
decompose in the silica gel column and these compounds can't
be separated by column layer chromatography. At last, the
crystallization method has been used to separate these Schiff
in vitroAntitumor activity:We predict that the as-synthesis
Schiff base compounds containing pyrazole group has biolo-
gical activity for the Schiff base and pyrazole derivatives have
been widely used in biomedical fields. For this reason, we
choose compounds B2 and B4 as examples to explore their
in vitro antitumor activity. Their antiproliferative activity against
K562 (human leukemia cell line) was evaluated by in vitro
MTT assays. Amonafide was tested as a reference compound.
The biological results were shown in Table-1. It can be seen
base compounds while EtOH and CH2Cl2 (VEtOH:VCH Cl2 = 1:3)
as solvent.
2
R1
R1
H
N
NHNH2HCl
O
N
reflux
N
+
N
R3
N
CH3OH
R3
N
R2
R2
R1=OH; R3=H; R2=
R1=Cl; R3=H; R2=
R1=CH3; R3=H; R2=H(C1);
p
-CH3(A1);
p
-F(A2);
m
-Cl(A3);
-Br(B3); -NO2(B4
-Cl(C3); -Br(C4); p-NO2(C5)
p-Br(A4); p-NO2(A5)
p-F(B1);
m
-Cl(B2);
p
p
)
p
-F(C2);
-CH3(D2);
m
p
R1=CH3; R3=
p
-Br; R2=H(D1);
p
p
-F(D3);
p-Br(D4);
p-NO2(D5
)
R1=CH3; R3=
p
-NO2; R2=H(E1);
p
-CH3(E2);
p-F(E3);
m
-Cl(E4);
p-Br(E5); p-NO2(E6)
Fig. 1. Synthesis of Schiff base compounds

Vol. 26, No. 24 (2014)
Synthesis and Antitumor Activity of Novel Schiff Bases Containing Pyrazole Group 8313
3. R.N. Jadeja, J.R. Shah, E. Suresh and P. Paul, Polyhedron, 23, 2465
(2004).
from Table-1 that the compounds B2 and B4 have showed anti-
proliferative activity against K562 and can inhibit the growth
of K562 cells.
4. M.B.R. Bastos, J.C. Moreira and P.A.M. Farias, Anal. Chim. Acta, 408,
83 (2000).
5. S. Sadeghi, F. Fathi, A.A. Esmaeili and H. Naeimi, Sens. Actuators B,
114, 928 (2006).
TABLE-1
INHIBITIONRATES OF COMPOUNDS
B2 AND B4 TO K562 CELL LINES
6. S.B. Desai, P.B. Desai and K.R. Desai, Heterocycl. Commun., 7, 83 (2001).
7. S. Banthia and A. Samanta, Phys. Chem. B, 110, 6437 (2006).
8. S.J. Toal, K.A. Jones, D. Magde and W.C. Trogler, J. Am. Chem. Soc.,
127, 11661 (2005).
K562 (%)
Compound
10 µmol L-1
18.5
30 µmol L-1
39.0
9. R.I. Kureshy, N.H. Khan, S.H.R. Abdi, S.T. Patel and R.V. Jasra, Tetra-
hedron Lett., 42, 2915 (2001).
Amonafide
10.6
11.8
B2
B4
10. C.A. Sureshan and P.K. Bhattacharya, J. Mol. Catal. Chem., 136, 285
(1998).
0.31
9.1
11. A. Tong, Y. Akama and S. Tanaka, J. Chromatogr. A, 478, 408 (1989).
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Conclusion
We have synthesized 5 series novel Schiff bases containing
pyrazole group and characterized by means of 1H NMR, FT-
IR, MS and elemental analysis. The test shows that the com-
pounds B2 and B4 have showed antiproliferative activity against
K562 and can inhibit the growth of K562 cells.
14. F.R. Pérez, J. Belmar,Y. Moreno, R. Baggio and O. Peña, New J. Chem.,
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16. J. Guo, T.G. Ren, J.L. Zhang, G.H. Li, W.J. Li and L.R. Yang,
Spectrochim. Acta A, 95, 135 (2012).
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