One-pot synthesis of diphenyl pyrazolylmethylanilines via reductive amination using NaBH4/I2 and their antimicrobial screening

Article abstract of DOI:10.1007/s00706-011-0495-5

Direct reductive amination of 1,3-diphenyl-1H-pyrazole-4-carbaldehyde and 3-(4-methylphenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde with various substituted aromatic amines using NaBH₄ in the presence of I₂ as reducing agent is describe

Full text of DOI:10.1007/s00706-011-0495-5

Monatsh Chem (2011) 142:637–642
DOI 10.1007/s00706-011-0495-5
ORIGINAL PAPER
One-pot synthesis of diphenyl pyrazolylmethylanilines
via reductive amination using NaBH4/I2 and their
antimicrobial screening
•
Sandhya Bawa Fasih Ahmad Suresh Kumar
•
Received: 27 October 2010 / Accepted: 30 March 2011 / Published online: 22 April 2011
Ó Springer-Verlag 2011
Abstract Direct reductive amination of 1,3-diphenyl-1H-
pyrazole-4-carbaldehyde and 3-(4-methylphenyl)-1-phe-
nyl-1H-pyrazole-4-carbaldehyde with various substituted
aromatic amines using NaBH4 in the presence of I2 as
reducing agent is described. The reaction has been carried
out in anhydrous methanol under neutral conditions at
room temperature. The structure of newly synthesized
diphenyl pyrazolylmethylanilines was established on the
in numerous biologically active compounds [5, 6]. Further-
more, secondary amines can be utilized as important
scaffolds for structural manipulations. These amines have
been demonstrated to be extremely useful intermediates for
the synthesis of numerous natural products and bioactive
molecules [7–9].
Reductive amination of aldehydes and ketones is an
important direct transformation of carbonyl compounds into
amines. In this important carbon–nitrogen bond-forming pro-
cess, an aldehyde or ketone is reacted with ammonia, primary,
or secondary amines in the presence of reducing agents to
produce primary, secondary, and tertiary amines, respectively.
A variety of reducing agents, such as hydrogen in the presence
of metal catalyst, Zn–AcOH, NaBH4–magnesium perchlorate,
ZnBH4–ZnCl2, NaBH3CN, NaBH(OAc)3, borane–pyridine,
ZnCl2–NaBH4, silica gel–Zn(BH4)2, and NaBH4–wet clay/
microwave, have been used for these transformations [10–19].
As part of our research for potential biologically active het-
erocycles containing a pyrazole ring and amines [20, 21], we
report here an efficient method for the direct reductive amina-
tion of 1,3-diphenyl-1H-pyrazole-4-carbaldehyde (3) and 3-(4-
methylphenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde (4) with
various aromatic amines using NaBH4 and a catalytic amount
of iodine in absolute methanol in reasonably good yield. The
newly synthesized diphenyl pyrazolylmethylanilines were also
screened for possible antimicrobial activity against a panel of
fungal and bacterial strains.
1
basis of IR, H, 13C NMR, and mass spectral data. All
diphenyl pyrazolylmethylaniline derivatives were tested in
vitro for their antifungal and antibacterial activity against
different strains of fungi and bacteria. Most of the com-
pound exhibited considerable antifungal activity but poor
antibacterial activity against the test strains.
Keywords Reductive amination Á NaBH4/I2 Á
Diphenyl pyrazolylmethylaniline Á NMR spectroscopy Á
Antimicrobial screening
Introduction
Amines are important organic compounds and their syn-
thesis have been widely studied in organic chemistry.
Moreover, amines bearing heteroaryl rings are a large class
of organic compounds whose chemistry and biology have
been exploited considerably for drug discovery [1–4].
Because of their interesting physiological properties, sec-
ondary amines in particular are extremely important and are
consistently found in privileged structures (pharmacophores)
Results and discussion
Chemistry
S. Bawa Á F. Ahmad Á S. Kumar (&)
Department of Pharmaceutical Chemistry, Faculty of Pharmacy,
Jamia Hamdard, New Delhi 110062, India
e-mail: sureshkr.2006@gmail.com
The requisite key intermediates of pyrazolecarbaldehydes 3
and 4 were prepared by the reaction of the Vilsmeier–
123

638
S. Bawa et al.
Preliminary antimicrobial activity
Haack reagent (N,N-dimethylformamide (DMF)/POCl3)
and phenyl hydrazones 1 and 2 [22]. The various new
diphenyl pyrazolylmethylanilines 5a–5e and 6a–6h were
synthesized by direct reductive amination using NaBH4 in
the presence of I2 as reducing agent as outlined in
Scheme 1.
All the diphenyl pyrazolylmethylanilines were tested in
vitro for antifungal activity against Candida albicans
(ATCC 64550), Aspergillus niger (MTCC 281), A. flavus
(MTCC 277), and Penicillium citrinum (NCIM 768) using
the cup-plate agar diffusion method at concentrations of
6.25, 12.5, 25, 50, 100, and 200 lg/cm3 [23, 24]. Fluco-
nazole was used as a reference drug at a concentration of
6.25 lg/cm3.
As shown in Table 2 among the series 5a–5e and 6a–6h,
compounds 5a, 5c, 6b, 6c, and 6e exhibited a minimum
inhibitory concentration (MIC) in the range of 25–50 lg/cm3
against C. albicans, whereas compounds 5a, 5c, 5d, and
6a–6g showed antifungal activity against A. niger and
A. flavus with MIC values in the range of 25–50 lg/cm3. The
minimum concentration required to inhibit the growth of
P. citrinum was found to be in the range of 50–100 lg/cm3.
The lipophilicity of the compounds is well known to play an
important role in antifungal activity [25]. Our results dem-
onstrate that increasing the lipophilic character of the
compounds increased the antifungal activity of diphenyl
The reaction was carried out by simply stirring 1.0
equivalent of aldehyde and 1.2 equivalents of aromatic
amine in methanol in the presence of the NaBH4/I2
reagent. The iodine catalyzed the in situ formation of an
imine at room temperature that was ultimately reduced in
situ to the secondary amine by NaBH4. The functional
group transformation of –CHO in compounds 3 and 4
into –CH2NH– in compounds 5a–5e and 6a–6h was
1
established on the basis of IR, H, 13C NMR including
DEPT-135, and mass spectral data. In the 1H NMR
spectra of compound 3 and 4, the aldehyde proton res-
onated as
a singlet at d = 10.06 and 9.95 ppm,
respectively, which disappeared in spectra of compounds
5a–5e and 6a–6h, and a new signal was observed at high
upfield values at d = 4.11–4.21 ppm integrating for two
protons. The signal due to the NH proton was observed
at d = 5.51–6.32 ppm. The methylene group of
–CH2NH– appeared as a singlet, broad singlet (bs), and
in some compounds as a doublet (J = 3.8–5.1 Hz) due
to coupling with the NH proton whereas the NH signal
was observed as a broad singlet. Furthermore in the 13C
NMR spectra of the compounds 3 and 4, the signal due
to the carbonyl carbon was observed at d = 178.9 and
180.0 ppm, respectively. No carbonyl carbon signal was
found in the spectra of compounds 5a–5e and 6a–6h and
a new signal due to –CH2NH– appeared at 38.6–
40.2 ppm. This assignment was also confirmed by
DEPT-135 spectra of compounds 5a and 5b in which a
negative peak was observed for –CH2– at 39.6 and
40.2 ppm, respectively. The above spectral analy-
sis suggested the successful reductive amination of
pyrazolecarbaldehydes 3 and 4. This fact was further
supported by FAB-MS spectra of compounds 5a–5e and
6a–6h (Table 1).
pyrazolylmethylanilines
having
electron-withdrawing
groups but not electron-releasing groups.
All compounds were also screened for their in vitro
antibacterial activity against Escherichia coli (NCTC
10418), Staphylococcus aureus (NCTC 65710), and Pseu-
domonas aeruginosa (NCTC 10662). Ciprofloxacin was
used as a reference drug. None of the test compounds
showed good antibacterial activity, whereas compounds 5e
and 6h exhibited moderate antibacterial activity against
E. coli (NCTC 10418) and S. aureus (NCTC 65710). All
test compounds were poorly active against P. aeruginosa
(NCTC 10662).
Conclusion
On the basis of antifungal activity data, it can be concluded
that the newly synthesized diphenyl pyrazolylmethylaniline
Scheme 1
R
R
X
R
CHO
N
CH3
H
DMF / POCl3
50-60 °C
Ar-NH2 and NaBH4 / I2
MeOH, stirring
N
N
N
N
N
NH
1, 2
3, 4
5a-5e, 6a-6h
R = H, CH3
X = H, CH3, OCH3, Cl, F, NO2
123

One-pot synthesis of diphenyl pyrazolylmethylanilines
639
derivatives of the 5a–5e series. However the activity of the
tested compounds is less than that of the reference drugs
fluconazole and ciprofloxacin.
Table 1 Physicochemical data of diphenyl pyrazolylmethylaniline
derivatives 5a–5e and 6a–6h
Compd
R
X
Yielda M.p. ClogPb
Rf valuec
(%)
(°C)
5a
5b
5c
5d
5e
6a
6b
6c
6d
6e
6f
H
H
70
68
65
71
59
67
72
52
96
109
88
5.18 1.02
5.64 1.02
5.63 1.02
5.69 1.02
5.63 1.02
5.64 1.02
6.42 1.02
6.09 1.02
5.46 1.02
7.33 1.17
6.42 1.02
6.77 1.17
6.09 1.02
0.72
0.72
0.64
0.72
0.80
0.74
0.72
0.75
0.69
0.71
0.73
0.80
0.73
Experimental
H
3-CH3
4-F
H
All the chemicals were supplied by E. Merck (Germany)
and S. D. Fine chemicals (India). Melting points were
determined by the open tube capillary method. IR spectra
were recorded as KBr pellets on a Bio Rad FT-IR spec-
H
2-Cl
4-NO2
H
117
128
64
H
CH3
CH3 4-Cl
CH3 4-F
68
trophotometer. H and 13C NMR spectra were recorded on
1
75
a 300-MHz Bruker DPX spectrophotometer using DMSO-
d6 or CDCl3 as solvent. Mass spectra were recorded on a
JEOL SX102/DA-6000 mass spectrometer, elemental
analysis on a Vario EL III CHNOS-Elementar analyzer and
results agreed favorably with calculated values. Thin-layer
chromatography (TLC) was performed to monitor the
progress of the reaction and purity of the compounds, the
spots being visualized under iodine vapor or UV light.
Solvents were purified using standard procedures. Com-
pounds 3 and 4 were prepared according to a published
method [22].
CH3 4-OCH3 73
CH3 3-Cl-4-F 63
70
64
CH3 4-CH3
CH3 3-Cl
68
70
66
68
6g
6h
a
72
CH3 4-NO2
62
Recrystallization from ethanol/methanol/chloroform mixture
ACD lab software version 12.0 (freeware)
Benzene/acetone (9.5:0.5)
b
c
derivatives possess considerable antifungal activity. The
antifungal activity was higher in compounds substituted with
a chloro and fluoro group, whereas in the case of antibacterial
activity the compound substituted with a nitro derivative
exhibited slightly better activity compared to other
General procedure for synthesis of compounds
5a–5e and 6a–6h
To a solution of appropriate 1H-pyrazole-4-carbaldehyde 3
or 4 (1.0 mmol) in 10 cm3 of methanol, substituted aniline
Table 2 Antimicrobial activity data of diphenyl pyrazolylmethylaniline derivatives 5a–5e and 6a–6h
Compd
MIC (zone of inhibition)
Antifungal activity
Antibacterial activity
C. albicans
A. flavus
A. niger
P. citrinum
E. coli
S. aureus
P. aeruginosa
5a
50 (6.5)
100 (6.5)
50 (7.5)
100 (8.5)
100 (6.5)
100 (8.0)
50 (6.0)
25 (6.0)
100 (7.5)
25 (6.5)
100 (8.5)
100 (7.0)
100 (6.5)
6.25 (9.5)
NT
50 (5.5)
100 (8.0)
50 (7.0)
50 (6.0)
100 (7.5)
50 (5.5)
25 (5.0)
25 (6.5)
50 (5.0)
25 (6.5)
50 (6.5)
50 (8.5)
100 (6.0)
6.25 (9.0)
NT
50 (5.5)
100 (7.5)
50 (8.0)
50 (5.5)
100 (7.0)
50 (6.0)
25 (5.5)
25 (5.5)
50 (5.5)
25 (7.0)
50 (6.5)
50 (7.5)
–
100 (7.5)
100 (6.5)
100 (7.0)
100 (6.5)
–
200 (6.0)
200 (6.5)
200 (7.0)
200 (7.5)
100 (6.5)
100 (5.5)
100 (6.0)
100 (5.5)
200 (7.0)
100 (7.0)
200 (6.5)
200 (6.0)
200 (8.5)
NT
200 (6.5)
200 (7.0)
200 (7.0)
200 (7.0)
100 (7.5)
200 (8.0)
100 (7.0)
100 (6.0)
200 (7.0)
200 (5.5)
200 (7.0)
200 (6.5)
100 (6.5)
NT
–
5b
200 (5.5)
5c
–
5d
–
5e
200 (7.5)
6a
100 (8.5)
50 (6.5)
50 (7.0)
100 (7.5)
50 (7.5)
100 (6.5)
100 (7.5)
–
–
6b
200 (7.0)
6c
–
6d
–
6e
200 (6.0)
6f
–
6g
–
6h
200 (7.5)
NT
Fluconazole
Ciprofloxacin
6.25 (8.5)
NT
6.25 (10.0)
NT
6.25 (10.0)
6.25 (9.5)
6.25 (8.5)
MIC data are presented in lg/cm3; zone of inhibition data are in presented in mm
NT not tested; – absence of activity
123

640
S. Bawa et al.
7.30–7.53 (m, 6H, Ar–H), 7.78 (d, 2H, Ar–H, J = 7.8 Hz),
7.86 (d, 2H, Ar–H, J = 8.1 Hz), 8.57 (s, 1H, pyrazole-H-5)
ppm; 13C NMR (75 MHz, DMSO-d6): d = 39.4 (CH2),
112.7, 119.0, 120.2, 121.3, 126.4, 127.1, 127.8, 128.5,
130.3, 132.9, 136.1, 138.4, 141.8, 150.7 ppm.
(1.2 mmol) was added and then 50 mg iodine (0.4 mmol)
was added with stirring at room temperature. To the stirred
solution 55 mg of sodium borohydride (1.4 mmol) was
added slowly, stirring further for 3–6 h. A precipitate was
formed which was filtered, washed with water, dried,
and recrystallized from ethanol to give crystalline products
5a–5e and 6a–6h. The progress of the reaction and purity
of the compound were checked by TLC, using benzene/
acetone (9:1) as mobile phase. Physicochemical data of the
compounds are presented in Table 1.
N-(1,3-Diphenyl-1H-pyrazol-4-ylmethyl)-4-nitroaniline
(5e, C22H18N4O2)
IR (KBr): vꢀ = 3,218 (N–H), 1,603 (C=N), 1,497 (C=C),
;
1,067 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 4.20 (d, 2H, CH2, J = 5.1 Hz), 5.81 (bs, 1H, NH),
6.61 (d, 2H, Ar–H, J = 8.7 Hz), 7.02 (d, 2H, Ar–H,
J = 8.7 Hz), 7.24–7.48 (m, 6H, Ar–H), 7.71 (d, 2H, Ar–H,
J = 7.2 Hz), 7.77 (d, 2H, Ar–H, J = 7.8 Hz), 8.48 (s, 1H,
pyrazole-H-5) ppm; 13C NMR (75 MHz, DMSO-d6):
d = 39.8 (CH2), 39.4, 117.8, 119.5, 121.9, 123.1, 126.3,
127.1, 127.8, 128.6, 130.3, 133.1, 139.5, 141.2, 148.7,
152.6 ppm.
N-(1,3-Diphenyl-1H-pyrazol-4-ylmethyl)aniline
(5a, C22H19N3)
IR (KBr): vꢀ = 3,211 (N–H), 1,620 (C=N), 1,548 (C=C),
1,029 (C–N) cm-1
;
1H NMR (300 MHz, DMSO-d6):
d = 4.20 (bs, 2H, CH2), 5.91 (bs, 1H, NH), 6.52–6.66
(m, 3H, Ar–H), 7.04–7.09 (m, 2H, Ar–H), 7.22–7.30 (m,
3H, Ar–H), 7.46–7.51 (m, 2H, Ar–H), 7.67–7.69 (m, 2H,
Ar–H), 7.83–7.86 (m, 2H, Ar–H), 8.53 (s, 1H, pyrazole-H-
5) ppm; 13C NMR (75 MHz, DMSO-d6): d = 39.6 (CH2),
113.6, 117.0, 126.1, 127.4, 127.8, 128.6, 129.3, 131.3,
135.2, 139.9, 145.5, 151.6 ppm; FAB-MS: m/z = 325
(M?).
N-[3-(4-Methylphenyl)-1-phenyl-1H-pyrazol-4-
ylmethyl]aniline (6a, C23H21N3)
IR (KBr): vꢀ = 3,268 (N–H), 1,625 (C=N), 1,530 (C=C),
;
1,020 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 2.31 (s, 3H, CH3), 4.20 (bs, 2H, CH2), 5.91 (bs, 1H,
NH), 6.52–6.66 (m, 3H, Ar–H), 7.04–7.09 (m, 2H, Ar–H),
7.22–7.30 (m, 3H, Ar–H), 7.46–7.51 (m, 2H, Ar–H),
7.67–7.69 (m, 2H, Ar–H), 7.83–7.86 (m, 2H, Ar–H), 8.53
(s, 1H, pyrazole-H-5) ppm; 13C NMR (75 MHz, DMSO-
d6): d = 21.3 (CH3), 40.2 (CH2), 112.4, 115.9, 119.0,
126.8, 127.5, 127.9, 128.4, 129.7, 130.3, 133.8, 138.0,
140.1, 144.8, 151.1 ppm; FAB-MS: m/z = 339 (M?).
N-(1,3-Diphenyl-1H-pyrazol-4-ylmethyl)-3-methylaniline
(5b, C23H21N3)
IR (KBr): vꢀ = 3,264 (N–H), 1,599 (C=N), 1,515 (C=C),
;
1,067 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 2.13 (s, 3H, CH3), 4.20 (d, 2H, CH2, J = 4.6 Hz),
5.69 (bs, 1H, NH), 6.57 (d, 2H, Ar–H, J = 8.1 Hz), 6.89
(d, 2H, Ar–H, J = 8.1 Hz), 7.31–7.49 (m, 6H, Ar–H), 7.80
(d, 2H, Ar–H, J = 6.9 Hz), 7.85 (d, 2H, Ar–H,
J = 7.5 Hz), 8.54 (s, 1H, pyrazole-H-5) ppm; 13C NMR
(75 MHz, DMSO-d6): d = 20.6 (CH3), 40.1 (CH2), 113.2,
115.2, 118.3, 126.9, 127.3, 128.8, 129.6, 131.1, 136.2,
139.5, 145.1, 151.6 ppm; FAB-MS: m/z = 339 (M?).
4-Chloro-N-[3-(4-methylphenyl)-1-phenyl-1H-pyrazol-4-
ylmethyl]aniline (6b, C23H20ClN3)
IR (KBr): vꢀ = 3,274 (N–H), 1,684 (C=N), 1,515 (C=C),
;
1,011 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 2.31 (s, 3H, CH3), 4.19 (s, 2H, CH2), 6.16 (bs, 1H,
NH), 6.65 (d, 2H, Ar–H, J = 7.2 Hz), 7.09 (d, 2H, Ar–H,
J = 7.2 Hz), 7.25–7.50 (m, 5H, Ar–H), 7.66 (d, 2H, Ar–H,
J = 6.9 Hz), 7.85 (d, 2H, Ar–H, J = 6.9 Hz), 8.52 (s, 1H,
pyrazole-H-5) ppm; 13C NMR (75 MHz, DMSO-d6):
d = 21.5 (CH3), 39.9 (CH2), 113.2, 118.8, 119.8, 120.9,
126.5, 127.2, 127.9, 128.0, 129.7, 130.4, 133.5, 137.8,
141.3, 144.5, 152.0 ppm; FAB-MS: m/z = 374 (M?), 376
[(M ? 2)?].
N-(1,3-Diphenyl-1H-pyrazol-4-ylmethyl)-4-fluoroaniline
(5c, C22H18FN3)
IR (KBr): vꢀ = 3,309 (N–H), 1,599 (C=N), 1,506 (C=C),
;
1,025 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 4.21 (s, 2H, CH2), 5.83 (bs, 1H, NH), 6.62–6.67 (m,
2H, Ar–H), 6.88–6.94 (m, 2H, Ar–H), 7.30–7.52 (m, 6H,
ArH), 7.79 (d, 2H, Ar–H, J = 7.2 Hz), 7.85 (d, 2H, Ar–H,
J = 8.1 Hz), 8.53 (s, 1H, pyrazole-H-5) ppm; 13C NMR
(75 MHz, DMSO-d6): d = 39.8 (CH2), 112.9, 116.2,
119.3, 125.9, 127.3, 127.8, 128.4, 129.3, 131.3, 135.2,
139.9, 145.5, 151.6 ppm; FAB-MS: m/z = 343 (M?).
4-Fluoro-N-[3-(4-methylphenyl)-1-phenyl-1H-pyrazol-4-
ylmethyl]aniline (6c, C23H20FN3)
IR (KBr): vꢀ = 3,305 (N–H), 1,590 (C=N), 1,520 (C=C),
;
1,017 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
2-Chloro-N-(1,3-diphenyl-1H-pyrazol-4-ylmethyl)aniline
(5d, C22H18ClN3)
d = 2.32 (s, 3H, CH3), 4.17 (d, 2H, CH2, J = 5.1 Hz),
5.87 (bs, 1H, NH), 6.61–6.66 (m, 2H, Ar–H), 6.92 (t, 2H,
Ar–H, J = 9.0 Hz), 7.23–7.31 (m, 3H, Ar–H), 7.49 (t, 2H,
Ar–H, J = 7.9 Hz), 7.68 (d, 2H, Ar–H, J = 8.1 Hz), 7.85
(d, 2H, Ar–H, J = 8.4 Hz), 8.53 (s, 1H, pyrazole-H-5)
IR (KBr): vꢀ = 3,241 (N–H), 1,596 (C=N), 1,504 (C=C),
;
1,059 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 4.22 (d, 2H, CH2, J = 4.5 Hz), 6.32 (bs, 1H, NH),
6.54–6.67 (m, 3H, Ar–H), 7.07 (t, 1H, Ar–H, J = 7.8 Hz),
123

One-pot synthesis of diphenyl pyrazolylmethylanilines
641
ppm; 13C NMR (75 MHz, DMSO-d6): d = 21.4 (CH3),
39.8 (CH2), 112.6, 116.7, 118.3, 119.7, 126.8, 127.2, 128.1,
128.7, 129.9, 131.3, 135.8, 138.9, 140.5, 151.1, 156.5 ppm;
FAB-MS: m/z = 357 (M?).
Ar–H, J = 8.1 Hz), 7.23–7.31 (m, 3H, Ar–H), 7.49 (t, 2H,
Ar–H, J = 7.2 Hz), 7.66 (d, 2H, Ar–H, J = 7.8 Hz), 7.85
(d, 2H, Ar–H, J = 8.1 Hz), 8.54 (s, 1H, pyrazole-H-5)
ppm; 13C NMR (75 MHz, DMSO-d6): d = 20.9 (CH3),
38.6 (CH2), 119.0, 119.8, 121.3, 126.3, 127.2, 127.9, 128.7,
130.6, 131.9, 137.7, 139.4, 141.3, 148.7, 150.8 ppm;
FAB-MS: m/z = 374 (M?), 376 [(M ? 2)?].
4-Methoxy-N-[3-(4-methylphenyl)-1-phenyl-1H-pyrazol-4-
ylmethyl]aniline (6d, C24H23N3O)
IR (KBr): vꢀ = 3,228 (N–H), 1,600 (C=N), 1,510 (C=C),
1,030 (C–N) cm-1
;
1H NMR (300 MHz, DMSO-d6):
N-[3-(4-Methylphenyl)-1-phenyl-1H-pyrazol-4-ylmethyl]-
4-nitroaniline (6h, C23H20N4O2)
d = 2.31 (s, 3H, CH3), 3.61 (s, 3H, OCH3), 4.14 (d, 2H,
CH2, J = 5.1 Hz), 5.51 (bs, 1H, NH), 6.59–6.72 (m, 4H,
Ar–H), 7.22–7.28 (m, 3H, Ar–H), 7.48 (t, 2H, Ar–H,
J = 7.95 Hz), 7.68 (d, 2H, Ar–H, J = 8.1 Hz), 7.84 (d,
2H, Ar–H, J = 8.7 Hz), 8.51 (s, 1H, pyrazole-H-5) ppm;
13C NMR (75 MHz, DMSO-d6): d = 21.3 (CH3), 39.9
(CH2), 56.8 (OCH3), 112.9, 115.3, 117.7, 119.1, 126.2,
126.6, 128.7, 129.6, 129.9, 132.2, 135.5, 140.5, 149.6,
152.3 ppm; FAB-MS: m/z = 369 (M?).
IR (KBr): vꢀ = 3,307 (N–H), 1,593 (C=N), 1,573 (C=C),
;
1,028 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 2.32 (s, 3H, CH3), 4.16 (d, 2H, CH2, J = 5.1 Hz),
5.87 (bs, 1H, NH), 6.61–6.66 (m, 2H, Ar–H), 6.92 (t, 2H,
Ar–H, J = 9.0 Hz), 7.23–7.31 (m, 3H, Ar–H), 7.49 (t, 2H,
Ar–H, J = 7.9 Hz), 7.67 (d, 2H, Ar–H, J = 8.1 Hz), 7.84
(d, 2H, Ar–H, J = 8.4 Hz), 8.53 (s, 1H, pyrazole-H-5)
ppm; 13C NMR (75 MHz, DMSO-d6): d = 21.5 (CH3),
39.4 (CH2), 118.0, 119.6, 121.1, 122.9, 126.0, 126.8, 127.7,
129.5, 131.2, 133.6, 139.4, 141.7, 149.7, 151.2 ppm;
FAB-MS: m/z = 384 (M?).
3-Chloro-4-fluoro-N-[3-(4-methylphenyl)-1-phenyl-1H-
pyrazol-4-ylmethyl]aniline (6e, C23H19ClFN3)
IR (KBr): vꢀ = 3,291 (N–H), 1,603 (C=N), 1,503 (C=C),
;
1,058 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
Antimicrobial screening
d = 2.32 (s, 3H, CH3), 4.18 (d, 2H, CH2, J = 3.8 Hz),
6.17 (s, 1H, NH), 6.59–6.62 (m, 2H, N-phenyl-H),
6.74–6.77 (m, 1H, N-phenyl-H), 7.24–7.32 (m, 3H,
Ar–H), 7.67 (d, 2H, Ar–H, J = 7.8 Hz), 7.86 (d, 2H, Ar–H,
J = 8.1 Hz), 7.12 (t, 2H, Ar–H, J = 8.2 Hz), 7.50 (t, 1H,
Ar–H, J = 7.2 Hz), 8.55 (s, 1H, pyrazole-H-5) ppm; 13C
NMR (75 MHz, DMSO-d6): d = 21.3 (CH3), 38.9 (CH2),
115.6, 116.4, 118.1, 118.7, 119.6, 121.5, 127.2, 127.8,
128.1, 129.9, 130.6, 133.5, 138.9, 140.1, 148.8, 150.2,
156.3 ppm; FAB-MS: m/z = 392 (M?), 394 [(M ? 2)?].
Compounds 5a–5e and 6a–6h were tested against a panel
of bacterial strains such as E. coli (NCTC 10418), S. aureus
(NCTC 65710), P. aeruginosa (NCTC 10662) and fungal
strains, viz. A. niger (MTCC 281), A. flavus (MTCC 277),
Monascus purpureus (MTCC 369), and P. citrinum (NCIM
768), by the cup-plate method [23, 24]. Potato dextrose
agar (PDA) and nutrient agar were used as culture medium
for antifungal and antibacterial activity, respectively.
Normal saline with Tween 80 (0.01%) was used to make a
suspension of fungal and bacterial spores for lawning. PDA
medium (50 cm3) was poured into each petri dish (15 cm
diameter). Five cubic centimeter of the spore suspension
was spread over the solid agar medium and plates were
dried in an incubator at 37 °C for 1 h. An agar punch was
used to make wells on the seeded agar plates, and solutions
of test compounds in dimethyl sulfoxide (DMSO) in con-
centrations of 6.25, 12.5, 25.0, 50, 100, and 200 lg/cm3
were added into each well, labeled previously. A control
was also prepared using DMSO as solvent. The petri plates
were prepared in duplicate and incubated at 30 °C for 72 h
for fungi and 37 °C for 24 h for bacteria. Antifungal and
antibacterial activity was determined by measuring the
zone of inhibition and the minimum inhibitory concentra-
tion (MIC) was noted by seeing the lowest concentration of
the test drug at which there was no visible growth. Activity
of each compound 5a–5e and 6a–6h was compared with
the standards fluconazole and ciprofloxacin and results are
summarized as MIC (average zone of inhibition of two
readings in millimeter) in Table 1.
4-Methyl-N-[3-(4-methylphenyl)-1-phenyl-1H-pyrazol-4-
ylmethyl]aniline (6f, C24H23N3)
IR (KBr): vꢀ = 3,210 (N–H), 1,582 (C=N), 1,530 (C=C),
989 (C–N) cm-1
;
1H NMR (300 MHz, DMSO-d6):
d = 2.07 (s, 3H, CH3), 2.25 (s, 3H, CH3), 4.11 (d, 2H,
CH2, J = 4.2 Hz), 5.62 (bs, 1H, NH), 6.51 (d, 2H,
N-phenyl-H-2/6, J = 7.8 Hz), 6.83 (d, 2H, Ar–H,
J = 7.8 Hz), 7.02–7.24 (m, 3H, Ar–H), 7.42 (t, 2H,
Ar–H, J = 7.5 Hz), 7.62 (d, 2H, Ar–H, J = 7.8 Hz),
7.78 (d, 2H, Ar–H, J = 7.8 Hz), 8.44 (s, 1H, pyrazole-H-
5) ppm; 13C NMR (75 MHz, DMSO-d6): d = 20.5 (CH3),
21.6 (CH3), 39.1 (CH2), 113.8, 118.3, 119.1, 126.5, 127.2,
127.9, 128.5, 130.7, 132.8, 137.9, 141.2, 149.6, 151.2 ppm;
FAB-MS: m/z = 353 (M?).
3-Chloro-N-[3-(4-methylphenyl)-1-phenyl-1H-pyrazol-4-
ylmethyl]aniline (6g, C23H20ClN3)
IR (KBr): vꢀ = 3,254 (N–H), 1,664 (C=N), 1,520 (C=C),
;
1,020 (C–N) cm-1 1H NMR (300 MHz, DMSO-d6):
d = 2.32 (s, 3H, CH3), 4.20 (d, 2H, CH2, J = 3.9 Hz),
6.30 (bs, 1H, NH), 6.54–6.66 (m, 3H, Ar–H), 7.07 (t, 1H,
123

642
S. Bawa et al.
´ ´ ´ ´
11. Micovic IV, Ivanovic MD, Piatak DM, Bojic VD (1991) Syn-
Acknowledgments The authors are grateful to the AICTE, New
Delhi, India, for the award of a fellowship to FA. The authors also
thankful to Jamia Hamdard for providing the necessary facilities and
CDRI, Lucknow, India, for providing mass spectral data.
thesis 1043
12. Brussee JR, Van Benthem ATM, Kruse CG, Van der Gen A
(1990) Tetrahedron Asymmetry 1:163
13. Bhattacharyya S, Chatterjee A, Duttachowdhury SK (1994) J
Chem Soc Perkin Trans 1:1
14. Borch RF, Bernstein MD, Durst HD (1971) J Am Chem Soc
93:2897
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