48
SYNTHESIS AND ANTIBACTERIAL ACTIVITY OF NOVEL
PYRAZOLO[3,4-b]QUINOLINE BASED HETEROCYCLIC AZO
COMPOUNDS AND THEIR DYEING PERFORMANCE
Sanjay F. Thakor, Dinesh M. Patel, Manish P. Patel and Ranjan G. Patel
‫ وددد تدم تر دير مركآدا زو‬.‫[ كينولون بكمية انتاج جيدد‬b-4،3] ‫بيرازولو‬-H1-‫ ميثيل‬-6- ‫ أمينو‬-3 ‫تم تشييد مركب‬
‫ الرلةدة وددد تدم د اسدة جميدع‬.‫أحادية باستخدام هذا المركب الوسيط كمكون ديازو مع مكونا مختلفة متزاوجة عديدد‬
‫ وفيدأل اة دوة ادون الآنفسديية وفيدأل‬،‫ وترليدل عناردرها‬،‫ ود جدة انهدها ها‬،‫مركآا زو من حيث نسآة إنتاجها‬
‫اة وة ترت الرمراء ود جة رآغها على ألياف نايلون وبولي إستر ونشافها الم اد لليدراييم ددد الآكتيريدا موجآدة‬
‫اليرام والآكتيريا سالآة اليرام‬
3-Amino-6-methyl-1H-pyrazolo[3,4-b]quinoline was synthesized in good yield. Monoazo compounds were prepared using this intermediate as diazo component with various heterocyclic
coupling components. All the azo compounds were characterized by their percentage yield,
melting point, elemental analysis, UV-visible spectra, IR-spectra and dyeing performance on
nylon and polyester fibres and by their antibacterial activity against gram positive and gram
negative bacteria.
Key Words: 3-amino-6-methyl-1H-pyrazolo[3,4-b]quinoline, azo compounds, synthesis, dyeing,
fastness properties, antibacterial activity.
Introduction
The chemistry of quinoline has gained increasing
attention due to its various diverse pharmacological
activities (1-3). Quinoline ring fused with five or six
membered ring in linear fashion is found in natural
products as well as in synthetic compounds of biological interest. Dictemine and skimmianine are the
examples of two naturally occurring compounds
which are associated with smooth muscle contracting properties.
Biological importance of azo compounds is well
known for their use as antineoplastics (4), antidiabetics (5), antiseptics (6) and other useful chemotherapeutic agents. It has been found that the activity
of azo linkage increases on the incorporation of
suitable heterocyclic moiety. Pyrazole derivatives
are also considered as potent biologically active
compounds (7,8). With this background it has been
thought worth to synthesize linearly fused 3-amino6-methyl-1H-pyrazolo[3,4-b]quinoline and use as a
diazo component to prepare some new azo compounds as possible antibacterial agents. All the azo
compounds were also applied on nylon and polyester
fibres as disperse dyes and their dyeing performance
have assessed. The general structure of azo
compounds is shown in Figure 1.
N
H3C
N
*
Department of Chemistry, Sardar Patel University, Vallabh
Vidyanagar-388 120, Gujarat, INDIA.
N
H
N
N
6a-i
*
To whom correspondence should be addressed.
E-mail: drsanjaythakor@yahoo.com
Saudi Pharmaceutical Journal, Vol. 15, No. 1, January 2007
R
Figure 1. General structure
AZO-QUINOLINES AS ANTIBACTERIALS
Experimental
All melting points are uncorrected and determined by an electrothermal melting point apparatus
and expressed in oC. All the coupling components
used were synthesized in laboratory except 8hydroxy quinoline which was purchased from Spectrochem Co. The IR spectra were recorded on a
Nicolet Impact-400D FT-IR spectrophotometer using KBr pellets technique. The 1H-NMR spectra
were recorded on a Hitachi R-1500, 60MHz
instrument using TMS as the internal standard.
Chemical shifts are given in  (ppm). The mass spectrum was carried out on a Jeol D-300 model. The
absorption spectra (max) of all the azo compound
solutions in DMF were recorded on a Shimadzu UV240 spectrophotometer.
Preparation of 2-chloro-6-methyl-3-quinoline-carboxaldehyde (1):
The title compound was synthesized following a
sequence of reactions according to a procedure described in the literature (9,10). Yield 69%; m.p. 123125oC.
Preparation of 2-chloro-6-methyl-3-quinoline-carboxaldehyde oxime (2):
The title compound was synthesized following a
reaction according to a procedure described in the
literature (11). Yield 75%; m.p.193-195oC.
Preparation
of
2-chloro-6-methyl-3-quinolinecarbo-nitrile (3):
The title compound was synthesized following a
reaction according to a procedure described in the
literature (12). Yield 70%; m.p.181-183oC.
Preparation of 3-amino-6-methyl-1H-pyrazolo[3,4b]quinoline (4):
The title compound was synthesized following a
reaction according to a procedure described in the
literature (12). Yield 65%; m.p.331oC.
Preparation details of pyrazolo[3,4-b]quinoline
based azo compounds (6a-i)
Diazotization of 3-amino-6-methyl-1H-pyrazolo
[3,4-b]quinoline (Scheme 1) was carried out with
hydrochloric acid as follows:
Diazotization:
Concentrated hydrochloric acid (2 ml, 0.016
mol) was added to a well stirred suspension of 3amino -6- methyl -1 H- pyrazolo [3,4-b] quinoline 4
Saudi Pharmaceutical Journal, Vol. 15, No. 1, January 2007
49
(0.534 g 0.0027 mol) in water (20 ml) and the
mixture was heated up to 70oC and maintained at
that temperature till a clear solution obtained. After
cooling the solution to 0-5oC in an ice bath, a solution of sodium nitrite (0.75 g, 0.0054 mol) in water
(20 ml) was added drop wise over a period of 10
minutes with stirring. The reaction was stirred at a
temperature below 5oC for an hour. The excess of
nitrous acid (tested for using starch iodide paper)
was removed by adding required amount of
sulphamic acid solution (10%). The clear diazonium
salt solution 5 thus obtained was used immediately
in the coupling reaction (Scheme 1).
3-methyl-4-((6-methyl-1H-pyrazolo[3,4-b]quinolin3-yl)diazenyl)-1-phenyl-1H-pyrazol-5-ol (6a):
General coupling procedure:
3-methyl - 1- phenyl – 5 -pyrazolone (0.469 g,
0.0027 mol) was dissolved in sodium hydroxide
solution (7 ml, 10% W/V). The solution was cooled
to 0-5 oC in an ice-bath. To this well stirred solution,
the above diazonium solution 5 was added dropwise
keeping temperature below 5 oC. The reaction mass
was further stirred for 2 hrs at 0-5 oC maintaining the
pH 8.0 by adding required amount of 10% sodium
carbonate solution. The reaction mass was then
heated up to 60 oC and diluted with water (80 ml).
The dye was filtered off, washed with hot water until
the washings were neutral, dried and powered. The
product was purified by dissolving in DMF and
pouring in water. 1H-NMR(DMSO-d6):  2.48 (s,
3H, CH3 quinoline), 2.33 (s, 3H, CH3 pyrazole), 8.60
(s, 1H, NH), 7.41-7.97 (m, 9H, ArH), 11.34 (s, 1H,
OH). m/z 383 (M+), 384(M+1), 406(Na adduct),
276.9, 183, 142.
The following compounds were prepared in similar manner.
1 - (3 - chlorophenyl ) -3- methy l -4- ((6-methyl-1Hpyrazolo [3,4-b]quinolin-3-yl)diazenyl)-1H-pyrazol5-ol (6b). 1H-NMR (DMSO-d6):  2.50 (s, 3H, CH3
quinoline), 2.46 (s, 3H, CH3 pyrazole), 8.66 (s, 1H,
NH), 7.47-7.99 (m, 8H, ArH), 11.20 (s, 1H, OH).
3-amino-4-((6-methyl-1H-pyrazolo[3,4-b]quinolin3-yl)diazenyl)-1-phenyl-1H-pyrazol-5-ol (6c):
1
H-NMR (DMSO-d6):  2.55 (s, 3H, CH3
quinoline), 6.50 (s, 2H, NH2), 8.59 (s, 1H, NH),
7.40-7.95 (m, 9H, ArH), 11.33 (s, 1H, OH).
50
2-amino-5-((6-methyl-1H-pyrazolo[3,4-b]quinolin3-yl)diazenyl)benzo[d]thiazol-6-ol (6d):
1
H-NMR (DMSO-d6):  2.50 (s, 3H, CH3 quinoline), 7.10 (s, 2H, NH2), 8.65 (s, 1H, NH), 7.33-7.98
(m, 6H, ArH), 10.12 (s, 1H, OH).
7-((6-methyl - 1H-pyrazolo [3,4-b] quinolin -3- yl)
diazenyl) quinolin-8-ol(6e):
1
H-NMR (DMSO-d6):  2.42 (s, 3H, CH3 quinoline),
8.68 (s, 1H, NH), 7.10-8.85 (m, 9H, ArH), 10.26 (s,
1H, OH).
2-mercapto-6-methyl-5-((6-methyl-1H-pyrazolo[3,4b]quinolin-3-yl)diazenyl)pyrimidin-4-ol (6f):
1
H-NMR (DMSO-d6):  2.42 (s, 3H, CH3
quinoline), 8.60 (s, 1H, NH), 2.58 (s, 3H, CH3
pyrimidine), 7.34-7.95 (m, 4H, ArH), 10.23 (s, 1H,
OH), 12.35 (s, 1H, SH).
7-hydroxy-4-methyl-8-((6-methyl-1H-pyrazolo[3,4b]quinolin-3-yl)diazenyl)-2H-chromen-2-one. (6g):.
1
H-NMR (DMSO-d6):  2.33 (s, 3H, CH3
quinoline), 8.66 (s, 1H, NH), 2.55 (s, 3H, CH3
coumarin), 7.50-7.98 (m, 7H, ArH), 9.90(s, 1H,
OH).
THAKOR ET AL
AATCC/88/1988 and the wash fastness test in
accordance with IS: 765-1979. By observing the
alternation of dyed pattern light fastness rating was
given by grey-scale (1 to 8). Where, 1-very poor, 2poor, 3-fair, 4-fairly good, 5-good, 6-very good, 7excellent, 8-outstanding. Rating for sublimation,
perspiration and wash fastness is given by grey-scale
(1 to 5). Where, 1-poor, 2-fair, 3-good, 4-very good
and 5-excellent. Data of fastness properties are given
in Table 3.
Antibacterial activity:
Antibacterial activities of synthesized compounds were examined in vitro by known agar diffusion
cup method (14-17). All the compounds were tested
for activity against gram-positive bacteria like Bacillus cereus ATCC 10987, Staphylococcus aureus
ATCC 6538 and Bacillus subtilis ATCC 6633 and
gram-negative bacteria Escherichia coli ATCC
10536. The culture medium was nutrient agar. All
the compounds were dissolved in DMF (500ppm
concentration) and DMF used as control. Norfloxacin was employed as the standard drug. The results
are summarized in Table 4.
Results and Discussion
5-hydroxy-1,4-dimethyl-6-((6-methyl-1H-pyrazolo
[3,4-b]quinolin-3-yl)diazenyl)Pyrimidin-2 (1H)-one.
(6h):
1
H-NMR (DMSO-d6):  2.40 (s, 3H, CH3
quinoline), 8.60 (s, 1H, NH), 1.2 (s, 3H, CH3), 2.79
(s, 3H, CH3-N),7.45-7.96 (m, 4H, ArH), 11.45(s, 1H,
OH).
3-(4-hydroxyphenyl)-1-(4-methoxyphenyl)-2-thioxo3- ( ( 6- methyl - 1H - pyrazolo [3,4-b] quinolin-3-yl)
diazenyl)dihydropyrimidin-4,6(1H,5H)-dione.(6i):
1
H-NMR (DMSO-d6):  2.48 (s, 3H, CH3
quinoline), 8.55 (s, 1H, NH), 3.80 (s, 3H, OCH3),
3.20 (s, 2H, CH2), 6.97-7.98 (m, 10H, ArH), 10.08(s,
1H, OH).
Dyeing method:
Dyeing of nylon and polyester has been carried
out for 2% shade following standard procedures (13).
Fastness properties:
The fastness to light, sublimation and perspireation were assessed in accordance with AATCC
/15/1985. The rubbing fastness test was carried out
with a crockmeter (Atlas) in accordance with
Saudi Pharmaceutical Journal, Vol. 15, No. 1, January 2007
The fused pyrazole intermediate, 3-amino-6methyl-1H-pyrazolo[3,4-b]quinoline 4 was prepared
by dehydration of 2-chloro-6-methyl-3-quinolinecarboxaldehyde oxime with thionyl chloride followed by cyclization with hydrazine hydrate in ethanol.
(Scheme 1). The fused pyrazole inter-mediate 4 was
diazotized satisfactorily at 0-5oC by usual procedure
using hydrochloric acid and sodium nitrite. The
diazonium salt was used immediately since it decomposed on standing, even when cold. Subsequent
coupling reactions took place readily on adding the
diazonium salt continuously to the solution of coupling component in alkaline medium at 0-5oC maintaining the pH 8.0 by adding required amount of
10% sodium carbonate solution.
Spectral properties of the azo compounds:
The absorption maxima (max) and logarithm of
the molar extinction coefficient (log) of the dyes
6a-i are given Table 1. The absorption maxima of
6a-i were recorded in DMF solution. The absorption
maxima were in the range of 383 nm to 523 nm. The
value of logarithm of molar extinction coefficient
(log) of the dyes 6a-i were in the range 4.15-4.68.
AZO-QUINOLINES AS ANTIBACTERIALS
H3C
51
H3C
Ac2O/AcOH
NH2
O
NH
CHO
H3C
CH3 DMF/POCl
3
Reflux
Cl
N
1
EtOH
NH2OH
NH2
H3C
N
N
H
N
4
CN
H3C
NH2NH2
EtOH
CH NOH
H3C
SOCl2
Cl
N
Cl
N
2
3
HCl /NaNO2 0-5oC
+
N2Cl
H3C
N
H
N
5
N
Coupling with R H3C
N
N
H
N
N
R
N
6
Wherein, R= various heterocyclic coupling components with their coupling position.
CH3
a.
O
N
NH2
CH3
N
b.
O
N
N
c.
N
O
.
N
HO
S
d
NH2
N
Cl
e.
N
OH
N
f.
H3C
N
CH3
CH3
OH
O
HO
O
S
OMe
i. HO
N
O
Scheme 1: Synthetic route of azo compounds 6a-i.
Saudi Pharmaceutical Journal, Vol. 15, No. 1, January 2007
N
h.
g.
SH
HO
N
O
N
CH3
O
52
THAKOR ET AL
Table 1: Absorption maxima, logarithm of molar
extinction coefficient and dyebath exhaustion of azo
compounds 6a-i on nylon and polyester.
Comp.
no.
Absorption in
DMF
max
log
% Exhaustion
Nylon
Polyester
6a
485
4.26
74
70
6b
481
4.15
72
68
6c
468
4.45
73
72
6d
383
4.68
64
62
6e
523
4.34
73
68
6f
394
4.17
71
70
6g
400
4.28
66
65
6h
477
4.56
70
68
6i
441
4.48
68
63
Infrared spectra of azo compounds:
All the azo compounds showed a characteristic
band at 1575-1594 cm-1 for the azo (-N=N-) group.
The band at 2873-2920 cm-1 is due to C-H stretching
of methyl groups. The band at 1312-1318 cm-1 can
be attributed to bending of aromatic methyl group.
The characteristic band at 3120-3178 cm-1 is due to
N-H stretching of secondary amine group. The band
appears at 3032-3057 cm-1 corresponding to C-H
stretching of aromatic rings. The band at 742 cm-1 is
due to a C-Cl stretching.
Dyeing properties of azo compounds
The azo compounds 6a-i were applied at 2%
depth on polyester and nylon as disperse dyes. The
properties are given in Table 1. These dyes mostly
gave various brown, orange, reddish orange and yellow shades with good depth on the fibres. The variation of the shades of the dyed fibres results from
the different coupling components.
Table 2: Physicochemical properties of azo compounds 6a-i.
Comp.
no.
Molecular
formula
Molecular
Weight
g/mol.
Melting Yield
Point (oC) (%)
C%
H%
N%
(d)
Calcd.
Found
Calcd.
Found
Calcd.
Found
6a
C21H17N7O
383
240-245
70
65.98
65.75
4.58
4.43
25.34
25.58
6b
C21H16N7OCl
417
290-296
77
60.14
60.23
3.76
3.83
23.88
23.60
6c
C20H16N8O
384
276-280
73
62.78
62.88
4.56
4.37
29.45
29.26
6d
C18H13N7SO
375
234-237
71
57.87
57.60
4.16
4.36
26.45
26.23
6e
C20H14N6O
354
225-228
75
67.34
67.59
3.58
3.44
20.14
20.33
6f
C16H13N7SO
351
193-195
67
54.55
54.70
3.95
3.70
27.67
27.92
6g
C21H15N5O3
385
201-204
74
65.22
65.45
3.60
3.85
18.56
18.38
6h
C17H15N7O2
349
248-255
69
58.21
58.42
4.67
4.49
28.34
28.18
6i
C28H21N7SO4
551
259-264
70
60.77
60.98
3.69
3.81
17.92
17.78
(d) Decomposition temperature
Saudi Pharmaceutical Journal, Vol. 15, No. 1, January 2007
AZO-QUINOLINES AS ANTIBACTERIALS
53
Table 3: Fastness properties of azo compounds 6a-i.
Comp.
no.
Light
Fastness
Wash
Fastness
Rubbing
Fastness
6a
N
4
P
4
N
4-5
P
5
N
4
P
5
N
5
P
4-5
6b
4
4-5
5
5
4
5
4
4
5
5
5
6c
4
4-5
5
4-5
4
4
4
4
5
5
6d
3-4
4
5
5
4
4-5
5
4
4-5
6e
4
3-4
5
5
5
4
4
4-5
6f
3-4
4
5
4-5
5
4
4
6g
3-4
3
5
5
4
4
6h
4
4-5
5
5
4
6i
3
3-4
4-5
4-5
4
Dry
Wet
Perspiration
Fastness
Acidic
Alkaline
N
P
N
P
5
5
5
5
Sublimation
Fastness
N
5
P
5
5
5
5
5
5
5
5
4
4
4-5
5
5
5
4-5
5
4-5
4-5
5
4
5
5
5
5
5
5
4
4-5
4-5
4
5
4-5
5
4-5
4
4
4
5
5
5
5
5
5
4-5
4
4
4
4-5
4
4
4-5
4
N-nylon and P-polyester
Table 4: Antibacterial activity data of compounds
6a-i.
Zone of inhibition (mm)
Compd.
E. coli B. subtilis B. cereus
S. aureus
6a
13
--
10
--
6b
15
12
8
10
6c
18
15
8
9
6d
9
--
--
--
6e
10
8
12
9
6f
20
17
13
11
6g
8
--
--
--
6h
10
8
6
5
6i
13
10
7
9
Norfloxacin
40
30
25
37
DMF
--
--
--
--
Saudi Pharmaceutical Journal, Vol. 15, No. 1, January 2007
The light fastness of all the disperse dyes on both
the fibres is found fair to fairly good to good. The
obtained results of washing fastness of the dyes for
both the fibres showed that they are very good to
excellent. Fastness to rubbing of dyed patterns was
very good to excellent for all the dyes on both the
fibres. This is attributed to good penetration and
affinity of dyes to the fibres. The perspiration and
sublimation fastness are very good to excellent.
Antibacterial Assay:
The antibacterial assay indicated that none of the
tested compounds showed significant activity
towards selected gram positive and gram negative
bacteria. The compound 6f exhibited higher activity
than other against all selected microorganisms. It is
observed that azo compounds 6a, 6b and 6c showed
moderate activity against E.coli and B.subtilis. The
remaining compounds displayed weak activity
against all microbes under investigation. A close
examination of the structure of the active compound
revealed that the best activity was confined with the
54
THAKOR ET AL
compound having pyrimidine as coupling component. Moreover pyrazolone as coupling component
in compounds 6a, 6b and 6c showed moderate
activity. In conclusion, the compounds having
pyrimidine and pyrazolone as coupling components
could be useful for derivatization to develop more
selective anti-ba-cterial agents.
5.
6.
7.
Acknowledgement
8.
The authors are thankful to Dr. K C Patel and
Mr. Kishor H Chauhan, Department of Biosciences,
Sardar Patel University for the antibacterial screening of the compounds. We are also thankful to CDRI, Lucknow for recording the mass spectral data.
References
1.
2.
3.
4.
Suresh T, Nandha Kumar R, Magesh S, Mohan PS.
Synthesis, characterization and antimicrobial activities of 4phenyl - 3 - thiopyrimido [4,5-b] quinolines. Indian Journal of
Chemistry, 2003, 42B: 2133-2135.
Rajendran SP, Karvembu R. Synthesis and antifungal activities of Schiff bases derived from 3-amino-2H-pyrano[2,3b]quinolin-2-ones. Indian Journal of Chemistry, 2002, 41B:
222-224.
Kalluraya B, Gururaja R, Rai G. One pot reaction: Synthesis,
characterization and biological activity of 3-alkyl/aryl-9substituted 1,2,4-triazolo[3,4-b][1,3,4] quinolino thiadiazepines.2003, 42B: 211-214.
Child RG, Wilkinson RG, Tomcu-Fucik A. Effect of Sub-
Saudi Pharmaceutical Journal, Vol. 15, No. 1, January 2007
9.
10.
11.
12.
13.
14.
15.
16.
17.
strate orientation of the adhesion of polymer joints. Chem.
Abstr., 1977, 87: 6031.
Garg HG, Praksh C. Preparation of 4-arylazo-3,5disubstituted-(2H)-1,2,6-thiadiazine-1,1-dioxides.
J.Med.
Chem, 1972, 15(4): 435-436.
Browing CH, Cohen JB, Ellingworth S, Gulbransen R. The
antiseptic properties of the aminoderivatives of styryl and anil
quinoline. Journal Storage, 1926, 100: 293-325.
Abadi AH, Eissa AA, Hassan GS. Synthesis of novel 1,3,4trisubstituted pyrazole derivatives and their evaluation as
antitumor and anti-angiogenic agents. Chem. Pharm. Bull,
2003, 51(7), 838-844.
Jain R, Dixit A, Pandey P. Synthesis of some New 1carbamoyl-3-aminophenyl- and 1-carbamoyl-3-amino-(2chlorophenyl)-5-methyl-4-arylpyrazoles as possible potential
antidiabetics. J. Indian Chem. Soc., 1989, 66: 486-489.
Horming EC. Organic synthesis, ed. John Wiley & Sons,
Inc., New York, 1955, 3: 661-663.
Cohn OM, Narine B and others. A versatile new synthesis of
quinolines and related fused pyridines, part-5. J. Chem.Soc.
Perkin Trans I, 1981, 1520-1526.
Nandeeshaiah SK, Ambekar SY. Synthesis of 2-aryl-1,2,3,4tetrahydropyrido [2’,3’,4,5] thieno [2,3-b] quinoline - 4- ones.
Indian Journal of Chemistry, 1994, 33B: 375-379.
Malcom BR, Ackerman JH, Pyrazolo[3,4-b]quinolines and
their use as antiviral agents. U.S. Patent, 1990, 4 920 128.
Desai JA, Patel MH, Patel RG, Patel VS. Azodisperse Dyes
with 4-Quinazolinone ring for dyeing polyester and nylon
fibres. Indian J. of Textile Research, 1985, 10: 75-79.
Chauhan KH, Trivedi UB. Studies on contamination
management in plant tissue culture, Dissertation Report,
Sardar Patel University, V.V.Nagar, India 2001.
Atlas RM. Principle of Microbiology, 1997, 10: 356-357.
Perry JJ, Staley JT. Microbiology Dynamics and Diversity,
Forth Wroth: Saunders College Pub., 1997, 7: 165-168.
Stainer RY. The Microbial World 5th ed., 1986, 12: 16-20.