Synthesis and antibacterial evaluation of some new 4-substituted-3-aryl-1- (2,6-dimethylpyrimidin-4-yl)pyrazoles

Article abstract of DOI:10.1002/jhet.701

Synthesis of a series of new 4-substituted-3-aryl-1-(2,6-dimethylpyrimidin- 4-yl)pyrazoles (2a-g, 3a-g, and 4a-g) is described. All the synthesized compounds were evaluated in vitro for their antibacterial activity against two gram-positive and two gram-n

Full text of DOI:10.1002/jhet.701

September 2011
Synthesis and Antibacterial Evaluation of Some New
4-Substituted-3-aryl-1-(2,6-dimethylpyrimidin-4-yl)pyrazoles
1211
Ravi Kumar,a,b* Reshmi R. Nair,a Saurabh Sudha Dhiman,c Jitender Sharma,d
and Om Prakashb*
aDepartment of Chemistry, Kurukshetra University, Kurukshetra-136119, Haryana, India
bDepartment of Chemistry, Dyal Singh College, Karnal-132001, Haryana, India
cBiotechnology Group, Thapar Centre for Industrial Research and Development (RCDP, TCIRD),
India
dDepartment of Biotechnology, Kurukshetra University, Kurukshetra-136119, Haryana, India
*E-mail: ravi.dhamija@rediffmail.com or dromprakash50@rediffmail.com
Received May 13, 2010
DOI 10.1002/jhet.701
Published online 9 June 2011 in Wiley Online Library (wileyonlinelibrary.com).
Synthesis of a series of new 4-substituted-3-aryl-1-(2,6-dimethylpyrimidin-4-yl)pyrazoles (2a–g, 3a–
g, and 4a–g) is described. All the synthesized compounds were evaluated in vitro for their antibacterial
activity against two gram-positive and two gram-negative bacteria, namely, Bacillus subtilis (MTCC
8509), Bacillus stearothermophilus (MTCC 8508), Escherichia coli (MTCC 51), and Pseudomonas
putida (MTCC 121), and their activity was compared with two commercial antibiotics, streptomycin
and chloramphenicol. Two compounds, namely, 3-(4-anisyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
carboxaldehyde (2b) and 3-(2-thienyl)-1-(2,6-dimethyl pyrimidin-4-yl)pyrazole-4-carboxaldehyde (2g)
were found to be equipotent to streptomycin and chloramphenicol against gram-negative bacteria,
E. coli having minimum inhibitory concentration (MIC) value ¼ 4 lg/mL. Compounds 4b and 4d also
displayed good activity against E. coli with MIC ¼ 8 lg/mL.
J. Heterocyclic Chem., 48, 1211 (2011).
INTRODUCTION
tive and two gram-negative bacteria. In this study, an
attempt has been made to explore the effect of various
substituents in the azole ring at C(4)-position.
Pyrazole ring is a prominent structural motif found in
numerous pharmaceutically active compounds. This is
mainly due to the easy preparation and important bio-
logical activity associated with pyrazoles. Pyrazole
framework plays an essential role in biologically active
compounds and, therefore, represents an interesting tem-
plate for combinatorial as well as medicinal chemistry.
Pyrazole derivatives have shown several biological
activities such as antibacterial [1,2], GABA receptor
antagonists and insecticidal [3], anxioyltic [4], anti-
inflammatory [5], potent PET ligand for CBI receptors
[6], and growth inhibition activity [7]. In addition to
theses observations, several reports have shown that py-
rimidine derivatives have diverse pharmacological prop-
erties, such as they act as antibacterial agents [8,9], anti-
inflammatory agents [10–13], antihypertensive agents
[14], anti-HIV agents [15], and H1-antihistamines [16].
In view of these observations, we have now synthe-
sized a series of 4-substituted-3-aryl-1-(2,6-dimethylpyr-
imidin-4-yl)pyrazoles (2a–g, 3a–g, and 4a–g) and eval-
uated their antibacterial activity against two gram-posi-
RESULTS AND DISCUSSION
Chemistry. Synthesis of 21 new 4-substituted-3-aryl-
1-(2,6-dimethylpyrimidin-4-yl)pyrazoles (2a–g, 3a–g,
and 4a–g) is outlined in Scheme 1.
A series of new 3-aryl-1-(2,6-dimethylpyrimidin-4-
yl)pyrazole-4-carboxaldehydes (2a–g) was synthesized
using Vilsmeier–Haack reaction. Thus, pyrimidinyl
hydrazones 1a–g were treated with a mixture of phos-
phorous oxychloride (POCl3) in DMF to give 3-aryl-1-
(2,6-dimethylpyrimidin-4-yl)pyrazole-4-carboxaldehydes
(2a–g). The structure of all the compounds 2a–g was
1
characterized by analyzing their spectral (IR, H NMR,
1
13C NMR, and mass) and elemental data. The H NMR
spectra of the compounds 2a–g displayed the carboxal-
dehyde proton as a sharp singlet between d 10.05–10.16
ppm, whereas in the 13C NMR spectra of these com-
pounds, peak in the region d 184.00–184.59 ppm further
C
V
2011 HeteroCorporation

1212
R. Kumar, R. R. Nair, S. S. Dhiman, J. Sharma, and O. Prakash
Vol 48
Scheme 1
confirmed the presence of CHO group. In the IR spectra,
the stretching frequency for aldehyde group (C¼¼O)
showed characteristic strong band between 1675–1694
complete characterization data of all the compounds is
summarized in experimental section.
Biological investigation. All the synthesized com-
pounds 2a–g, 3a–g, and 4a–g were evaluated for their
antibacterial activity against Bacillus subtilis (MTCC
8509), Bacillus stearothermophilus (MTCC 8508), Esch-
erichia coli (MTCC 51), and Pseudomonas putida
(MTCC 121), and their antibacterial activity was com-
pared with two well-known drugs ‘‘streptomycin’’ and
‘‘chlroamphenicol’’ (Table 1). Some of the test com-
pounds showed moderate to good antibacterial activity.
A careful investigation of minimum inhibitory concen-
tration (MIC) data showed that two compounds, in par-
ticular, 2b and 2g were found to be equipotent to strep-
tomycin and chlroamphenicol against gram-negative
bacteria, E. coli having MIC value ¼ 4 lg/mL. Com-
pounds 4b and 4d also displayed good activity against
E. coli with MIC¼ 8 lg/mL. Moreover, compounds 2b,
2g, and 4d were found active against P. putida, whereas
2g and 4a possess good antibacterial activity against B.
stearothermophilus with MIC value¼ 8 lg/mL. Oximes
3a–g were found to possess very modest to poor activity
against gram-positive and gram-negative bacteria (MIC
cmꢀ1
.
Furthermore, it has been reported in literature that
placement of a cyano moiety on the azole often generates
analogs with interesting antibacterial activities in vivo
and in vitro, in particular 3-cyano and 4-cyano pyrazoles
[17,18]. Keeping this in view, 3-aryl-1-(2,6-dimethylpyri-
midin-4-yl)pyrazole-4-carboxaldehydes (2) were trans-
formed to 3-aryl-1-(2,6-dimethylpyrimidin-4-yl)-4-cya-
nopyrazoles (4a–g) in good yields by making use of inex-
pensive and commercially available reagent, acetic anhy-
dride (Scheme 1). 3-Aryl-1-(2,6-dimethyl pyrimidin-4-
yl)-4-cyanopyrazoles (4a–g) were prepared by a two-step
procedure. 3-Aryl-1-(2,6-dimethylpyrimidin-4-yl)-4-for-
mylpyrazoles (2a–g) on treatment with NH2OH.HCl in
refluxing ethanol gave 3-aryl-1-(2,6-dimethylpyrimidin-
4-yl)pyrazole-4-aldoximes (3a–g) in excellent yields
which on further reaction with acetic anhydride afforded
4-cyanopyrazoles (4a–g) (Scheme 1). The structural
assignments of the compounds 3a–g and 4a–g were
based on their spectral as well as elemental analyses. The
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2011
Synthesis and Antibacterial Evaluation of Some New 4-Substituted-3-aryl-1-
(2,6-dimethylpyrimidin-4-yl)pyrazoles
1213
Table 1
MIC of Test Compounds (2a–h, 3a–h, and 4a–h) against four bacteria.
1H NMR (CDCl3, d, ppm): 2.735 (s, 6H, A2CH3), 7.463–
7.536 (m, 4H), 7.881–7.901 (m, 2H), 9.249 (s, 1H), 10.124 (s,
1H); 13C NMR (CDCl3, d, ppm): 184.74 (CHO), 166.65,
154.20, 122.84–134.83 (aromatic carbons), 26.21 (2CH3); ms:
m/z 278 (Mþ); Anal. Calcd. for C16H14N4O: C, 69.05; H, 5.07;
N, 20.13. Found: C, 68.98; H, 5.00; N, 20.10
B.
B.
P.
E.
Compounds
subtilis stearothermophilus putida coli
2a
2b
2c
2d
2e
2f
2g
3a
3b
3c
3d
3e
3f
3g
4a
4b
4c
4d
4e
4f
>64
32
>64
16
>64
>64
32
32 >64
3-(4-Anisyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-carbox-
aldehyde (2b). Mp 207–208ꢁC; Yield 77%; IR (mmax, KBr):
08
>64
04
32
>64
>64
>64
>64
16
>64
>64
>64
>64
32
>64
32
16
32
64
32
1
1693, 2884 cmꢀ1; H NMR (CDCl3, d): 2.526 (s, 3H, ACH3),
>64 >64
>64 >64
2.538 (s, 3H, ACH3), 3.869 (s, 3H, AOCH3), 6.940–6.968 (d,
2H, J ¼ 8.4 Hz), 7.287 (s, 1H), 7.750–7.778 (d, 2H, J ¼8.4 Hz),
9.20 (s, 1H), 10.07 (s, 1H); 13C NMR: 184.58 (CHO), 160.85,
155.01, 122.91–139.28 (rest aromatic carbons), 55.75 (OCH3),
26.21 (2CH3); ms: m/z 308 (Mþ); Anal. Calcd. for C17H16N4O2:
C, 66.22; H, 5.23; N, 18.71. Found: C, 66.18; H, 5.21; N, 18.67.
3-(4-Chlorophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
carboxaldehyde (2c). Mp 250ꢁC; Yield 78%; IR (mmax, KBr):
>64
08
>64
08
64
04
>64
>64
>64
>64
32
>64
32
08
16
>64 >64
>64 >64
>64 >64
32
16
>64
32
16
16
32
08
16
32
64
16
16
08
32
08
16
16
32
04
04
1
1692, 2853 cmꢀ1; H NMR (CDCl3, d): 2.791 (s, 3H, ACH3),
2.841 (s, 3H, ACH3), 7.312–7.548 (m, 3H), 7.923–7.952(d,
2H, J ¼ 8.7 Hz), 9.51 (s, 1H), 10.1 (s, 1H); 13C NMR: 184.69
(CHO), 166.63, 155.39, 152.62, 122.89-136.07 (aromatic car-
bons), 100.00, 26.21 (2CH3); ms: m/z 312 (Mþ), 314 (Mþþ2).
Anal. Calcd. for C16H13N4OCl: C, 61.44; H, 4.19; N, 17.91.
Found: C, 61.42; H, 4.15; N, 17.89.
64
64
16
16
32
16
16
16
4g
Streptomycin
Chloramphenicol
32
02
16
02
16
04
3-(4-Bromophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
carboxaldehyde (2d). Mp 177–179ꢁC; Yield 78%; IR (mmax
,
02
02
02
KBr): 1692, 2918 cmꢀ1 1H NMR (CDCl3, d): 2.730 (s, 3H,
;
ACH3), 2.773 (s, 3H, ACH3), 7.599–7.685 (m, 3H), 7.882–
7.7.910 (d, 2H, J ¼8.4 Hz), 9.256 (s, 1H), 10.093 (s, 1H); 13C
NMR: 184.46 (CHO), 166.62, 155.44, 152.84, 122.86–135.77
(aromatic carbons), 99.99, 26.12 (2CH3); ms: m/z 357 (Mþ);
Anal. Calcd. for C16H13N4OBr: C, 53.80; H, 3.67; N, 15.68.
Found: C, 53.78; H, 3.64; N, 15.66.
B. subtilis: Bacillus subtilis (MTCC 8509); B. stearothermophilus: Ba-
cillus stearothermophilus (MTCC 8508); P. putida: Pseudomonas
putida (MTCC 121); E. coli: Escherichia coli (MTCC 51).
value ranges from 16–64 lg/mL and higher). The results
of biological evaluation are given in Table 1.
3-(4-Fluorophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
carboxaldehyde (2e). Mp 194–195ꢁC; Yield 75%; IR (mmax
,
KBr): 1692, 2775 cmꢀ1 1H NMR (CDCl3, d): 2.622 (s, 6H,
;
ACH3), 7.173–7.231 (m, 3H), 7.958–7.986 (d, 2H, J ¼ 8.4
Hz), 9.251 (s, 1H), 10.088 (s, 1H); 13C NMR: 184.06 (CHO),
166.14, 154.95, 152.48, 122.26–135.11 (aromatic carbons),
115.16, 99.48, 25.66 (2CH3); ms: m/z 296 (Mþ); Anal. Calcd.
for C16H13N4OF: C, 64.86; H, 4.42; N, 18.91. Found: C,
64.82; H, 4.41; N, 18.89.
EXPERIMENTAL
Chemical synthesis. Melting points were taken in open
capillaries and are uncorrected. IR spectra were recorded on
Perkin-Elmer IR spectrophotometer. The 1H NMR spectra
were recorded on BRUKER 300 MHz instrument (in some
cases 400-MHz instrument was used). The chemical shifts are
expressed in ppm units downfield from an internal TMS stand-
ard. Elemental analyses were performed on Perkin-Elmer 2400
instrument, and mass spectra were recorded on Kratos MS-3
mass spectrometer.
3-(4-Nitrophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
carboxaldehyde (2f). Mp 196ꢁC; Yield 80%; IR (mmax, KBr):
1694, 110, 2763, 2859 cmꢀ1 1H NMR (CDCl3, d): 2.649 (s,
;
3H, ACH3), 2.732 (s, 3H, ACH3), 7.171 (s, 1H), 8.188–8.214
(d, 2H, J ¼ 7.8 Hz), 8.507–8.570 (d, 2H, J ¼7.8 Hz), 9.538
(s, 1H), 10.05 (s, 1H); 13C NMR: 184.16 (CHO), 166.14,
154.48, 123.68–137.79 (rest aromatic carbons), 25.66 (2 CH3);
ms: m/z 323 (Mþ); Anal. Calcd. for C16H13N5O3: C, 59.44; H,
4.05; N, 21.66. Found: C, 59.39; H, 4.03; N, 21.65.
General procedure for the preparation of 3-aryl-1-(2,6-
dimethylpyrimidin-4-yl)pyrazole-4-carboxaldehydes (2a–g). To
the Vilsmeier–Haack reagent prepared by dissolving POCl3
(0.03 mol) in 20-mL DMF, hydrazone (1, 0.01 mol) was
added, and the reaction mixture was stirred at 60–70ꢁC for 3
h. The reaction mixture was then poured over crushed ice. The
resulting solution was neutralized with sodium bicarbonate so-
lution. Solid, thus obtained, was filtered, washed with water,
and recrystallized from ethanol to afford pure 3-aryl-1-(2,6-di-
methyl-4-pyrimidinyl) pyrazole-4-carboxaldehydes (2a–g).
Characterization data of 3-aryl-1-(2,6-dimethylpyrimidin-4-
yl)pyrazole-4-carboxaldehydes (2a–g). 3-Phenyl-1-(2,6-dime-
thylpyrimidin-4-yl)pyrazole-4-carboxaldehyde (2a). Mp 116ꢁC;
3-(2-Thienyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-carbox-
aldehyde (2g). Mp 178ꢁC; Yield 74%; IR (mmax, KBr): 1689.5,
2924 cmꢀ1 1H NMR (CDCl3, d): 2.271 (s, 3H, ACH3), 2.28
;
(s, 3H, ACH3), 7.1509–7.1729 (m, 2H), 7.4398–7.4553 (dd,
1H, J ¼1.04 Hz, J0 ¼5.12 Hz), 8.0768–8.0886 (dd, 1H, J0 ¼
5.12 Hz, J" ¼ 3.68 Hz), 9.2169 (s, 1H), 10.1640 (s, 1H); 13C
NMR: 184 (CHO), 166.74, 155.27, 148.20, 122.21–136.05,
26.16 (2CH3); ms: m/z 284 (Mþ); Anal. Calcd. for
C14H12N4OS: C, 59.14; H, 4.25; N, 19.70. Found: C, 59.11; H,
4.23; N, 19.68.
Yield 75%; IR (mmax, KBr): 1677.6 (CO stretch), 2914.5 cmꢀ1
;
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1214
R. Kumar, R. R. Nair, S. S. Dhiman, J. Sharma, and O. Prakash
Vol 48
General procedure for the preparation of 3-aryl-1-(2,6-
3-(2-Thienyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-aldox-
ime (E/Z) (3g). Mp 170ꢁC; Yield 78%; IR (mmax, KBr): 1599,
dimethylpyrimidin-4-yl)pyrazole-4-aldoximes (3a–g). To the
solution of pyrazole-4-carboxaldehyde (2, 0.01 mol) in ethanol
were added hydroxylamine hydrochloride (0.02 mol) and so-
dium acetate (0.03 mol). The resulting mixture was refluxed
for 4 h and cooled. Solid, thus obtained, on cooling was fil-
tered and dried to get 3 (mixture of E/Z isomers was
obtained).
1
3432 cmꢀ1; H NMR (DMSO, 400 MHZ, d): 2.7230 (s, 3H),
2.7319 (s, 3H), 2.7426 (s, 3H), 7.4689–7.5305 (m, 3H),
7.5793–7.9745 (m, rest aromatic protons), 8.9012–8.9668 (m,
2H), 9.1847 (s,1H), 9.3188 (s, 1H), 9.5500–9.5946 (m, 2H),
10.9963 (s, 1H), 11.6802 (s, 1H); ms: m/z 299 (Mþ); Anal.
Calcd. for C14H13N5OS: C, 56.17; H, 4.38; N, 23.40. Found:
C, 56.14; H, 4.36; N, 23.39.
General procedure for the preparation of 3-aryl-1-(2,6-
dimethylpyrimidin-4-yl)-4-cyanopyrazoles (4a–g). A mixture
of aldoxime (3, 0.01 mol) in acetic anhydride (2 mL) was
refluxed for 30 min. The reaction was quenched by pouring
into crushed ice with stirring and neutralized with sodium bi-
carbonate. The solid, separated after standing overnight, was
filtered with water, dried, and recrystallized from methanol to
afford cyanopyrazoles 4.
Characterization data of 3-aryl-1-(2,6-dimethylpyrimidin-4-
yl)pyrazole-4-aldoximes (3). 3-Phenyl-1-(2,6-dimethylpyrimi-
din-4-yl)pyrazole-4-aldoxime (E/Z) (3a). Mp 190ꢁC; Yield
76%; IR (mmax, KBr): 1607, 3233 cmꢀ1 1H NMR (DMSO,
;
400 MHZ, d): 2.734 (s, 6H), 2.7628 (s, 3H), 7.2129–8.0368
(m, rest aromatic protons), 8.9428 (s, 1H), 9.00 (s,1H), 9.3867
(s, 1H), 9.4897 (s, 1H); 11.0 (s, 1H), 11.5010 (s, 1H); ms: 293
(Mþ); Anal. Calcd. for C16H15N5O: C 65.52, H 5.15, N 23.88.
Found: C 65.2, H 5.12, N 23.84.
3-(4-Anisyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-aldox-
ime (E/Z) (3b). Mp 149ꢁC; Yield 77%; IR (mmax, KBr): 1608,
Characterization data of 3-aryl-1-(2,6-dimethylpyrimidin-4-
yl)-4-cyanopyrazoles (4a–g).
midin-4-yl)-4-cyanopyrazole (4a). Mp 164ꢁC; Yield 67%; IR
(mmax, KBr): 2232 cmꢀ1 1H NMR (CDCl3, 400 MHZ, d):
3-Phenyl-1-(2,6-dimethylpyri-
1
3243 cmꢀ1; H NMR (DMSO, 400 MHZ, d): 2.5819 (s, 3H),
2.73 (s, 3H), 2.7623 (s, 3H), 3.7979 (s, 3H), 3.8314 (s, 3H),
6.8423–7.0296 (m, 4H), 7.1589 (s, 1H), 7.3291–7.4642
(m, 3H), 7.7514–8.1307 (m, 2H), 8.2081 (s, 1H), 8.2493
(s,1H), 8.4933 (s, 1H), 8.5333 (s, 1H); 9.9952 (s, 1H),
10.7006 (s, 1H); ms: m/z 323 (Mþ); Anal. Calcd. for
C17H17N5O2: C, 63.15; H, 5.30; N, 21.66. Found: C, 63.12; H,
5.26; N, 21.63.
;
2.723 (s, 3H, ACH3), 2.773 (s, 3H, ACH3), 7.430–7.634 (m,
3H), 7.961–8.085 (m, 2H), 9.155 (s, 1H); 13C NMR (CDCl3,
d, ppm): 114.32 (CN); ms: m/z 275 (Mþ); Anal. Calcd. for
C16H13N5 C, 69.80; H, 4.76; N, 25.44. Found: C, 69.78; H,
4.76; N, 25.43.
3-(4-Anisyl)-1-(2,6-dimethylpyrimidin-4-yl)-4-cyanopyrazole
(4b). Mp 153ꢁC; Yield 69%; IR (mmax, KBr): 2223 cmꢀ1 1H
;
3-(4-Chlorophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
aldoxime (E/Z) (3c). Mp 230ꢁC; Yield 78%; IR (mmax, KBr):
NMR (CDCl3, 400 MHZ, d): 2.6728 (s, 3H, ACH3), 2.68 (s,
3H, ACH3), 3.8528 (s, 3H, OCH3), 7.5034–7.5255 (d, 2H, J
¼8.84 Hz), 7.7980 (s, 1H), 8.0083–8.0253 (d, 2H, J ¼ 8.84
Hz), 9.15 (s,1H); 13C NMR (CDCl3, d, ppm): 114.59 (CN);
ms: m/z 305 (Mþ); Anal. Calcd. for C17H15N5O C, 66.86; H,
4.95; N, 22.94. Found (C, 66.83; H, 4.92; N, 22.91.
1
1604, 3239 cmꢀ1; H NMR (DMSO, 400 MHZ, d): 2.5819 (s,
3H), 2.7284 (s, 3H), 2.7523 (s, 3H), 7.4985–7.5294 (m, 4H),
7.6314–7.7400 (m, 2H), 7.6899–7.7252 (m, 2H), 7.8161 (s,
1H), 8.0594 (s,1H), 8.1456 (s, 1H), 9.4456 (s, 1H), 9.5362 (s,
1H), 11.0314 (s, 1H), 11.7091 (s, 1H); ms: m/z 328 (Mþ), 330
(Mþþ2); Anal. Calcd. for C16H14N5OCl: C, 58.63; H, 4.31; N,
21.37. Found: C, 58.61; H, 4.28; N, 21.35.
3-(4-Chlorophenyl)-1-(2,6-dimethylpyrimidin-4-yl)-4-cyanopyr-
azole (4c). Mp 178ꢁC; Yield 69 %; IR (mmax, KBr): 2214
1
cmꢀ1; H NMR (CDCl3, 400 MHZ, d): 2.7465 (s, 6H, ACH3),
3-(4-Bromophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
aldoxime (E/Z) (3d). Mp 244ꢁC; Yield 77%; IR (mmax, KBr):
7.5019–7.5228 (d, 2H, J ¼ 8.36 Hz), 7.6363 (s, 1H), 8.0682–
8.0891 (d, 2H, J ¼ 8.36 Hz), 9.2060 (s, 1H); 13C NMR
(CDCl3, d, ppm): 114.89 (CN); ms: m/z 310 (Mþ), 312
(Mþþ2); Anal. Calcd. for C16H12N5Cl C, 62.04; H, 3.90; N,
22.61. Found: C, 62.03; H, 3.88; N, 22.57.
1607, 3243 cmꢀ1 1H NMR (DMSO, 400 MHZ, d): 2.70 (s,
;
3H), 2.71 (s, 3H), 6.996 (s, 1H), 7.4963–7.9288 (m, 8H),
8.1902 (s,1H), 8.999 (s,1H), 8.9944 (s,1H), 9.1662 (s, 1H),
9.5573 (s, 1H); ms: m/z 372 (Mþ); Anal. Calcd. for
C16H14N5OBr: Found C, 51.63; H, 3.79; N, 18.82. Found: C,
51.60; H, 3.75; N, 18.81.
3-(4-Bromophenyl)-1-(2,6-dimethylpyrimidin-4-yl)-4-cyanopyr-
azole (4d). Mp 198ꢁC; Yield 71%; IR (mmax, KBr): 2232
1
cmꢀ1; H NMR (CDCl3, 400 MHZ, d): 2.7382 (s, 3H, ACH3),
3-(4-Fluorophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
aldoxime (E/Z) (3e). Mp 176ꢁC; Yield 79%; IR (mmax, KBr):
2. 7443 (s, 3H, ACH3), 7.6210–7.6985 (m, 3H), 8.0072–
8.0283 (d, 2H, J ¼ 8.44 Hz), 9.1470 (s, 1H); 13C NMR
(CDCl3, d, ppm): 116.52 (CN); ms: m/z 354; Anal. Calcd. for
C16H12N5Br C, 54.25; H, 3.41; N, 19.77. Found: C, 54.21; H,
3.38; N, 19.74.
1
1604, 3248 cmꢀ1; H NMR (DMSO, 400 MHZ, d): 2.5919 (s,
3H), 2.7484 (s, 3H), 2.7623 (s, 3H), 7.2013–7.2621 (m, 4H),
7.4291 (s, 1H), 7.6899–7.7252 (m, 3H), 8.0220–8.1383 (m,
2H), 8.9523 (s, 1H), 9.0012 (s,1H), 9.4072 (s, 1H), 9.5794 (s,
1H); 10.9965 (s, 1H), 11.7006 (s, 1H); ms: m/z 311 (Mþ);
Anal. Calcd. for C16H14N5OF: C, 61.73; H, 4.53; N, 22.3.
Found: C, 61.70; H, 4.4; N, 22.48.
3-(4-Fluorophenyl)-1-(2,6-dimethylpyrimidin-4-yl)-4-cyanopyr-
azole (4e). Mp 157ꢁC; Yield 68%; IR (mmax, KBr): 2230 cmꢀ1
;
1H NMR (CDCl3, 400 MHZ, d): 2.7456 (s, 3H, ACH3),
2.7672 (s, 3H, ACH3), 7.2003–7.2222 (d, 2H, J ¼ 8.76 Hz),
7.6346 (s, 1H), 8.0910–8.1129 (d, 2H, J ¼ 8.76 Hz), 9.2051
(s, 1H); 13C NMR (CDCl3, d, ppm): 116.54 (CN); ms: m/z 293
(Mþ); Anal. Calcd. for C16H12N5F C, 65.52; H, 4.12; N,
23.88. Found: C, 65.48; H, 4.09; N, 23.85.
3-(4-Nitrophenyl)-1-(2,6-dimethylpyrimidin-4-yl)pyrazole-4-
aldoxime (E/Z) (3f). Mp 216ꢁC; Yield 76%; IR (mmax, KBr):
1
1588, 3452 cmꢀ1; H NMR (DMSO, 400 MHZ, d): 2.5955 (s,
3H), 2.5996 (s, 3H), 7.8268–8.4053 (m, 11H), 8.9618 (s, 1H),
9.0069 (s, 1H), 9.2988–9.6585 (m, 2H), 10.9721 (s, 1H),
11.0294 (s,1H); ms: m/z 338 (Mþ); Anal. Calcd. for
C16H14N6O3: C, 56.80; H, 4.17; N, 24.84. Found: C, 56.79; H,
4.14; N, 24.81.
3-(4-Nitrophenyl)-1-(2,6-dimethylpyrimidin-4-yl)-4-cyanopyr-
azole (4f). Mp 195ꢁC; Yield 71%; IR (mmax, KBr): 2238 cmꢀ1
;
1H NMR (CDCl3, 400 MHZ, d): 2.7521 (s, 3H, ACH3), 2.90
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2011
Synthesis and Antibacterial Evaluation of Some New 4-Substituted-3-aryl-1-
(2,6-dimethylpyrimidin-4-yl)pyrazoles
1215
(s, 3H, ACH3), 7.6769 (s, 1H), 8.3201–8.3959 (m, 4H), 9.2091
(s, 1H); 13C NMR (CDCl3, d, ppm): 115.89 (CN); ms: m/z 320
(Mþ); Anal. Calcd. for C16H12N6O2. C, 60.00; H, 3.78; N,
26.24. Found: C, 59.98; H, 3.75; N, 26.22.
and 4d were found active against P. putida, whereas 2g
and 4a possess good antibacterial activity against B.
stearothermophilus with MIC value¼ 8 lg/mL.
3-(2-Thienyl)-1-(2,6-dimethylpyrimidin-4-yl)-4-cyanopyrazole
(4g). Mp 167ꢁC; Yield 67%; IR (mmax, KBr): 2218 cmꢀ1 1H
;
Acknowledgments. The authors are thankful to DST (grant no.
SR/FTP/CS-125/2006) for providing financial assistance to ac-
complish this work. The authors are also grateful to Krukshetra
University for the award of University Research Scholarship to
Reshmi R. Nair.
NMR (CDCl3, 400 MHZ, d): 2.7651 (s, 3H, ACH3), 2.7761 (s,
3H, ACH3), 7.1692–7.1936 (dd, 1H, J ¼3.6 Hz, J0 ¼ 5.12 Hz),
7.4850–7.5867 (m, 2H), 7.8874–7.9479 (dd, 1H, J ¼3.6 Hz, J"
¼1.04 Hz), 9.2125 (s, 1H); 13C NMR (CDCl3, d, ppm): 116.32
(CN); ms: m/z 281(Mþ); Anal. Calcd. for C14H11N5S. C, 59.77;
H, 3.94; N, 24.89. Found C, 59.75; H, 3.91; N, 24.85.
REFERENCES AND NOTES
Biological investigation. Minimum inhibitory concentra-
tion. MIC is the lowest concentration of the antimicrobial
agents that prevents the development of visible growth of
microorganism after overnight incubation. MIC of chemically
synthesized compounds against two Gram-positive and two
Gram-negative bacteria, namely, B. subtilis (MTCC 8509), B.
stearothermophilus (MTCC 8508), E. coli (MTCC 51), and P.
putida (MTCC 121) was determined by reported method [19].
Nutrient broth was adjusted to pH 7.0 used for the determi-
nation of MIC. The inoculum of the test microorganisms were
prepared by using 16-h-old cultures adjusted by reference to
the 0.5 McFarland standards (108 cells/mL) [20]. These cul-
tures were further diluted upto 10 folds with nutrient broth to
get the inoculum size of 1.2 ꢂ 107 CFU/mL. A positive con-
trol (containing inoculum but no compound) and a negative
control (containing compound but no inoculum) were also pre-
pared. A stock solution of 4 mg/mL of each compound was
prepared in DMSO and further appropriately diluted to get
final concentration ranging from 23 to 0.03 lg/mL [21]. Req-
uisite quantity of antifungal compound (cyclohexamide) was
added to the broth to get its desirable final concentration of
100 lg/mL. Separate flasks were taken for each test dilution.
To each flask was added the 100 lL of inoculum. Then appro-
priately diluted test sample was added to each flask having
broth and microbial inoculum. The contents of the flask were
mixed and incubated for 24–48 h at 37ꢁC. The test bacterial
culture were spotted in a predefined pattern by aseptically
transferring 5 lL of each bacterial culture on the surface of
solidified agar-agar plates and incubated at 37ꢁC for 24 h for
determining the MIC value.
[1] Aggarwal, R.; Kumar, V.; Tyagi, P.; Singh, S. P. Bioorg
Med Chem 2006, 14, 1785.
[2] Kane, J. L.; Hirth, B. H.; Laing, D.; Gourlie, B. B.; Nahill,
S.; Barosamim, G. Bioorg Med Chem Lett 2003, 13, 4463.
[3] Robert, E.; Sammelson, P. C.; Kathleen, A. D.; Durkin, A.;
John, E. C. Bioorg Med Chem 2004, 12, 3345.
[4] Athina, A.; Eugeni, B.; John, D.; Wim, D.; Dmitrii, F.; Irina
Galaeva, G.; Valentina, K.; Alexey, L.; Fliur, M.; Guenadiy, M. Bio-
org Med Chem 2004, 12, 6559.
[5] Adnan, A. B.; Tarek, A. A. Bioorg Med Chem 2004, 12, 1935.
[6] Dileep, J. S.; Jaya, P.; Victoria, A.; Ramin, V. P.; Mark, D.
U.; Norman, R. S.; Suham, A. K.; Vattoly, J. M.; Ronald, L.; Van
Heertum, H.; Mann, J. J. Bioorg Med Chem Lett 2004, 14, 2393.
[7] Pier, G. B.; Italo, B.; Paolo, C.; Nicoletta, B.; Gambari, G.
R.; Romeo, R. Bioorg Med Chem 2003, 11, 965.
[8] Reddick, J. J.; Saha, S.; Lee, J.; Melnick, J. S.; Perkins, J.;
Begley, T. P. Bioorg Med Chem Lett 2001, 11, 2245.
[9] Singh, P.; Kumar, R.; Sharma, B. K. J Enz Inhib Med
Chem 2003, 18, 395.
[10] Alagarsamy, V.; Shankar, D.; Solomon, V. R. ARKIVOC
2006, 16, 149.
[11] (a) Agarwal, S. K.; Tadiparthi, R.; Agarwal, P.; Shivakumar,
S. PCT Int Appl WO 2003084935, 2003; Chem Abstr 2003, 139,
323528.
[12] Bahekar, S. S.; Shinde, D. B. Bioorg Med Chem Lett 2004,
14, 1733.
[13] (a) Weingarten, G.; Bravi, G. PCT Int Appl WO
2004018452, 2004; Chem Abstr 2004, 140, 235741
[14] Pathak, P.; Kaur, R.; Kaur, B. ARKIVOC 2006, 16, 160.
[15] (a) Jiang, H.; Shen, X.; Zheng, Y.; Li, J.; Du, L.; Yang, L.;
Wang, R.; Chen, K.; Liu, H.; Wang, Y. PCT Int Appl WO
2007071199, 2007; Chem Abstr 2007, 147, 95708
CONCLUSIONS
[16] Alagarsamy, V.; Solomon, V. R.; Murugan, M. Bioorg Med
Chem 2007, 15, 4009.
All the chemically synthesized 21 compounds were
characterized using their spectral and elemental analy-
ses. These compounds were evaluated for their antibac-
terial activity against B. subtilis (MTCC 8509), B. stear-
othermophilus (MTCC 8508), E. coli (MTCC 51), and
P. putida (MTCC 121), and their activity was compared
with that of commercially known antibiotics, streptomy-
cin and chlroamphenicol. Two compounds, in particular,
2b and 2g were found to be equipotent to streptomycin
and chlroamphenicol against gram-negative bacteria, E.
coli, having MIC value ¼ 4 lg/mL. Compounds 4b and
4d also displayed good activity against E. coli (MTCC
51) with MIC¼ 8 lg/mL. Moreover, compounds 2b, 2g,
[17] Genin, M. J.; Allwine, D. A.; Anderson, D. J.; Barbachyn,
M. R.; Emmert, D. E.; Garmon, S. A.; Graber, D. R.; Grega, K. C.;
Hestor, J. B.; Hutchinson, D. K.; Morrism, J.; Reischerm, R. J.; Ford,
C. W.; Zurenko, G. E.; Hamel, J. C.; Schaadt, R. D.; Stapert, D.;
Yagi, B. H. J Med Chem 2000, 43, 953.
[18] Prakash, O.; Pundeer, R.; Ranjan, P.; Pannu, K.; Dhingra,
Y.; Aneja, K. R. Ind J Chem B 2009, 48, 563.
[19] Greenwood, D.; Slack, R.; Peutherer, J. Medical Microbiol-
ogy: A Guide to Microbial Infections: Pathogenesis, Immunity, Labo-
ratory Diagnosis and Control, 15th ed.; ELST Publishers: Edinburg,
1997.
[20] McFarland, J. J Am Med Assoc 1907, 14, 1176.
[21] NCCLS, Method for Dilution Antimicrobial Susceptibility
Test for Bacteria That Grow Aerobically, approved standard. 5th ed.,
NCCLS document M7–45, NCCLS: Villanova, PA, 2000.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet