Synthesis of heterocyclic monoazo dyes derived from 1H-benzo[g]pyrazolo[3, 4-Z>]quinoline-3-ylamine: Their antimicrobial activity and their dyeing performance on various fibers

Article abstract of DOI:10.1007/s11164-011-0426-4

Heterocyclic monoazobenzoquinoline-based azo dyes have been derived by diazotization of 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine with a variety of phenylpyrazolone-based coupling compounds. The synthesized dyes were characterized by determination of their percentage yield, by elemental analysis, and by UV-visible, IR, and ¹H NMR spectroscopy. Dyeing performance on silk, wool, nylon, and polyester fibers was assessed. The fastness properties of the dyes on each fiber were moderate to excellent. The antimicrobial activity of the dyes at different concentrations were also examined, by use of the Kirby-Bauer disk diffusion method. Springer Science+Business Media B.V. 2011.

Full text of DOI:10.1007/s11164-011-0426-4

Res Chem Intermed (2012) 38:885–901
DOI 10.1007/s11164-011-0426-4
Synthesis of heterocyclic monoazo dyes derived
from 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine:
their antimicrobial activity and their dyeing
performance on various fibers
•
Nikhil M. Parekh Kalpana C. Maheria
Received: 1 July 2011 / Accepted: 18 October 2011 / Published online: 1 November 2011
Ó Springer Science+Business Media B.V. 2011
Abstract Heterocyclic monoazobenzoquinoline-based azo dyes have been derived
by diazotization of 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine with a variety
of phenylpyrazolone-based coupling compounds. The synthesized dyes were char-
acterized by determination of their percentage yield, by elemental analysis, and by
1
UV–visible, IR, and H NMR spectroscopy. Dyeing performance on silk, wool,
nylon, and polyester fibers was assessed. The fastness properties of the dyes on each
fiber were moderate to excellent. The antimicrobial activity of the dyes at different
concentrations were also examined, by use of the Kirby–Bauer disk diffusion
method.
Keywords 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine ꢀ Phenyl pyrazolone ꢀ
Synthesis ꢀ Antimicrobial activity ꢀ Dyeing ꢀ Fastness properties
Introduction
The fastness of a variety of dyes based on heterocyclic ring systems is recognized as
being extremely strong. Several azo dyes have been prepared from amino
heterocycles by using selected quinoline, benzoquinoline, and quinazoline deriv-
atives as coupling components [1–7]. Hence, in continuation of our research work
on developing quinoline and benzoquinoline-containing heterocyclic azo com-
pounds, because of their significant biological and dyeing applications, it seemed
expedient to synthesize a series of heterocyclic monoazo compounds as possible
antimicrobial and dyeing agents. Quinoline and benzoquinoline rings combined
with five or six member rings in a linear arrangement are known to have good
N. M. Parekh ꢀ K. C. Maheria (&)
Department of Applied Chemistry, S. V. National Institute of Technology,
Surat 395007, Gujarat, India
e-mail: maheria@gmail.com
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N. M. Parekh, K. C. Maheria
pharmacological activity and are also used as intermediates in the dyestuffs industry
[8–22]. Therefore, it was thought of interest to synthesize a series of a heterocyclic
monoazo dyes derived from 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine which
not only have good dyeing properties but also have pharmacological (antibacterial
and antifungal) activity. This paper deals with the facile and convenient synthesis of
novel benzoquinoline-based heterocyclic monoazo dyes. Study of their dyeing
properties, fastness properties, and antimicrobial activity is also reported.
Experimental
Materials and methods
All chemicals were of analytical grade and used directly. All melting points were
determined by use of a PMP-DM scientific melting-point apparatus and are
uncorrected. The purity of all dyes was determined by thin-layer chromatography
(TLC) on aluminium foil plates coated with silica gel G (0.5 mm layer thickness,
Merck). Infrared spectra were recorded on a Shimadzu FT-IR 8400S model using
KBr pellets. 1H NMR spectra were acquired on a Varian 400 MHz model
spectrophotometer using DMSO as a solvent and TMS as internal reference
(chemical shifts in d, ppm). Elemental analysis of C, H, and N was performed on a
Carlo Erba 1108 instrument. Light fastness was assessed in accordance with BS:
1006-1978 (standard test method, 1978, 1994). The rubbing fastness test was carried
out with a Crock meter (Atlas) in accordance with AATCC-1961 (AATCC test
method, 1961) and the wash fastness test in accordance with IS: 765-1979 (Indian
standard ISO, 1979).
Kirby–Bauer disk diffusion method
The synthesized 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine derivatives 6a–j
were examined for antimicrobial activity against several bacteria (Staphylococcus
aureus MTCC 96, Bacillus subtilis MTCC 619, Escherichia coli MTCC 739,
Pseudomonas aeruginosa MTCC 741 and fungi Candida albicans MTCC 183,
Aspergillus niger MTCC 282) by use of the Kirby–Bauer disk diffusion method.
Mueller–Hinton agar medium was sterilized (autoclaved at 120 °C for 30 min),
poured at a uniform depth of 5 mm, and left to solidify. The microbial suspension
(105 CFU/mL) (0.5 McFarland nephelometry standards) was streaked over the
surface of the medium by use of a sterile cotton swab to ensure even growth of the
organisms. The tested compounds were dissolved in dimethylformamide to give
solutions of 20–500 lg/mL. Sterile filter paper disks measuring 6.25 mm in
diameter (Whatman No. 1 filter paper), previously soaked in a known concentration
of the respective test compounds in dimethylformamide, were placed on the
solidified nutrient agar medium that had been inoculated with the respective
microorganism and the plates were incubated for 24 h at 37 1 °C. A control disk
impregnated with an equivalent amount of dimethylformamide without any sample
was also used and did not cause any inhibition. Ciprofloxacin and flucanazole
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Synthesis of heterocyclic monoazo dyes
887
(100 lg/disk) were used as control drugs for antibacterial and antifungal activity,
respectively. Each assay was performed in triplicate.
General procedure for synthesis of N-naphthalen-2-yl-acetamide (1)
A mixture of 1-naphthylamine (1.0 mmol) and a catalytic amount of triethylamine
(1.2 mmol) in acetone was stirred at room temperature for an hour after which
acetyl chloride (1.2 mmol) was added dropwise and the mixture was further stirred
for another 1 h. The solution was then poured directly on to crushed ice. The
resulting white precipitate was isolated by filtration, washed with water, and dried in
air, and was pure enough for further use. A sample was recrystallized from ethanol
to give compound 1 as white needles, mp 159–160 °C, IR (KBr disk) 3270 (NH),
1656 (CO), 1548, 1398 cm-1
7.46–8.42 (7H, m Ar–H).
,
1H NMR (d6-DMSO) 2.17 (3H, s, COCH3),
General procedure for synthesis of 2-chlorobenzo[h]quinoline-3-carbaldehyde (2)
To a solution of N-naphthalen-2-yl-acetamide (5.4 mmol) in dry DMF (14 mmol)
was added POCl3 (102 mmol), and the mixture was stirred at 75 °C for 6 h. The
mixture was poured on to crushed ice and the resulting solid was isolated by
filtration, washed with water, and dried in an oven. A sample was recrystallized
from ethyl acetate–petroleum ether 60–80 °C to give the compound 2 as yellow
needles, mp 210–212 °C, IR (KBr disk) 1685 (CO), 1579, 1365 cm-1 (C–N, C=N),
1H NMR (CDCl3) 7.47–8.48 (7H, m, Ar–H), 10.58 (1H, s, CHO).
General procedure for synthesis of 2-chlorobenzo[g]quinoline-3-carbaldehyde
oxime (3)
To a solution of 2-chlorobenzo[g]quinoline-3-carbaldehyde (1.0 mmol) in ethanol,
hydroxylamine hydrochloride (1.2 mmol) and sodium acetate (1.2 mmol) were
added at room temperature and the mixture was stirred for 1 h. During stirring a
white precipitate formed. The reaction mixture was poured into ice-cold water and
the solid was isolated by filtration, dried, and used for further reaction, mp
172–176 °C, IR (KBr disk) 1668 (CHO), 1548, 1398 (C–N, C=N), 758 cm-1
1
(C–Cl), H NMR (d6-DMSO) 2.55(1H, s, OH), 7.48–8.54 (7H, m Ar–H).
General procedure for synthesis of 2-chlorobenzo[g]quinoline-3-carbonitrile (4)
Thionyl chloride (3.0 mmol) was added dropwise over a 30 min period to a stirred
solution of 2-chlorobenzo[g]quinoline-3-carbaldehyde oxime (1.0 mmol) in ben-
zene which was then heated under reflux for 1 h. The solvent was removed by
vacuum distillation. Brown–yellow needle crystals formed which were used for
further reaction, mp 184–189 °C, IR (KBr disk) 2221 (CN), 1548, 1398 (C–N,
1
C=N), 754 cm-1 (C–Cl), H NMR (d6-DMSO) 7.48–8.41 (7H, m Ar–H).
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N. M. Parekh, K. C. Maheria
General procedure for synthesis of 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-
ylamine (5)
To a stirred suspension of 2-chlorobenzo[g]quinoline-3-carbonitrile (1.0 mmol) in
ethanol was added hydrazine hydrate (1.2 mmol). The mixture was stirred under
reflux for 24 h. The reaction mixture was poured into ice cold water, and the
resulting yellow precipitate was isolated by filtration and dried, mp 286–290 °C, IR
(KBr disk) 3200–3289 (–NH), 1548, 1398 (C–N, C=N), 758 cm-1 (C–Cl), 1H NMR
(d6-DMSO) 7.48–8.79 (7H, m Ar–H), 12.56 (1H, s, NH).
Diazotization and coupling (6)
Concentrated HCl was added to a well stirred suspension of 1H-benzo[g]pyrazolo
[3,4-b]quinoline-3-ylamine (0.0048 mol) in water and the mixture was heated to
70 °C and maintained at that temperature until a clear solution was obtained. After
cooling of the solution to 0–5 °C in an ice-bath, an aqueous solution of sodium
nitrite (0.66 g) was added dropwise over a period of 30 min with continuous
stirring. The reaction was stirred at a temperature below 5 °C for approximately 1 h.
Starch–iodide paper was used to test for the presence of excess nitrous acid, which
was removed by adding the required amount of sulfamic acid solution (10%). The
clear diazonium salt solution thus obtained was used immediately in the coupling
reaction.
Coupling component (6a–j) was dissolved in sodium hydroxide solution. The
solution was cooled to 0–5 °C in an ice-bath. To this well-stirred solution, the above
diazonium solution was added dropwise keeping the temperature below 5 °C. The
reaction mass was further stirred for 2 h at 0–5 °C maintaining the pH at 8.0 by
adding the required amount of 10% sodium carbonate solution. The reaction mass
was then heated to 60 °C and diluted with water. The dye was isolated by filtration,
washed with hot water until the washings were neutral, dried, and powdered. The
product was purified by dissolution in DMF and pouring into water. Similar
coupling procedure and conditions were followed for all the dyes (Fig. 1 and
Chart 1).
Dye 6a (4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo)-5-methyl-2-p-tolyl-
2,4-dihydropyrazol-3-one): Yield: 78%; mp [ 300 °C; IR (KBr) m cm-1: 3250
(NH), 1552 (N=N), 1330 and 1564 (C–N and C=N), 2900–3100 (–CH stretching),
1
1478 (CH bending); H NMR (400 MHz, DMSO-d6) d ppm: 2.10 (s, 3H, –CH3 of
pyrazolone ring, 2.42 (s, 3H, CH3 of benzene ring), 7.68–9.07 (m, 11H, Ar–H),
12.08 (s, 1H, –NH, benzoquinoline ring); 13C NMR (400 MHz, DMSO-d6) d ppm:
13.42 (C-32, CH3 group of pyrazolone ring), 21.15 (C-31,CH3 group of benzene
ring), 118–152.12 (21C, Ar–C), 152.61 (C-17, of pyrazole ring carbon atoms), 158,
160 (C-28, 30 of pyrazolone ring carbon atoms); C25H19N7O (433.67): Calc. C,
69.27; H, 4.42; N, 22.62, found: C, 69.24; H, 4.38; N, 22.57.
Dye 6b (4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo)-2-(2,5-dichlorophenyl)-5-
:
methyl-2,4-dihydropyrazol-3-one): Yield: 78%; mp [ 300 °C; IR (KBr) m cm-1
3252 (NH), 1548 (N=N), 1333 and 1558 (C–N and C=N), 2982–3100 (CH
stretching), 1475 (CH bending), 752–754 (Ar–Cl); 1H NMR (400 MHz, DMSO-d6)
123

Synthesis of heterocyclic monoazo dyes
889
CHO
NH2OH.HCl
CH3COCl
DMF/POCl3
TEA
NH2
CH3COONa
NHCOCH3
N
Cl
1
2
N -OH
C
NH2
CN
NH2NH2.H2O
Ethanol
SOCl2
H
N
Benzene
N
H
N
N
Cl
N
Cl
5
4
3
N
N
N
NaNO2/HCl
R
N
H
N
6
Fig. 1 Schematic diagram of the synthesis of the heterocyclic monoazo compounds
R= various phenyl pyrazolone derivatives as coupling components
OH
OH
S
O
O
OH
S
HO
OH
O
S
O
O
O
S
O
O
S
Cl
O
O
O
Cl
Cl
H3C
N
N
O
O
N
N
N
N
N
O
O
N
N
N
H3C
H3C
H3C
H3C
H3C
Cl
CH3
Cl
Cl
Cl
N
N
N
O
O
O
N
N
N
N
N
O
O
N
N
H3C
H3C
H3C
H3C
H3C
Chart 1 Phenylpyrazolones used as coupling reagents (R)
d ppm: 2.04 (s, 3H, CH3 of pyrazolone ring, 7.44–8.97 (m, 10H, Ar–H), 12.10 (s,
1H, –NH, benzoquinoline ring); 13C NMR (400 MHz, DMSO-d6) d ppm: 13.46 (C-
31, CH3 group of pyrazolone ring), 111.24–150.12 (19C, Ar–C), 152.58 (C-17, of
pyrazole ring carbon atoms), 158.14, 160.12, (C-30, C-28, of pyrazolone ring
carbon atoms; C24H15Cl2N7O (487.07): Calc. C, 59.03; H, 3.10; N, 20.08; found: C,
59.00; H, 3.12; N, 20.12.
Dye 6c (4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo)-2-(3-chlorophenyl)-
5-methyl-2,4-dihydropyrazol-3-one): Yield: 82%; mp [ 300 °C; IR (KBr) m cm-1
:
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N. M. Parekh, K. C. Maheria
3242 (NH), 1556 (N=N), 1328 and 1545 (C–N and C=N), 2900–3100 (CH
1
stretching), 1478 (CH3 bending), 758 (Ar–Cl); H NMR (400 MHz, DMSO-d6) d
ppm: 2.00 (s, 3H, CH3 of pyrazolone ring, 12.10 (s, 1H, NH, benzoquinoline ring),
7.29–8.95 (m, 11H, Ar–H); 13C NMR (400 MHz, DMSO-d6) d ppm: 13.40 (C-31,
–CH3 group of pyrazolone ring), 112.24–150.12 (22C, Ar–C), 152.58 (C-17, of
pyrazole ring carbon atoms), 157.14, 162.14, (C-30, C-28 of pyrazolone ring carbon
atoms); C24H16ClN7O (453.11): Calc. C, 63.51; H, 3.55; N, 21.60; found: C, 63.55;
H, 3.52; N, 21.64.
Dye 6d (4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo)-2-(2-chlorophenyl)-5-
:
methyl-2,4-dihydropyrazol-3-one): Yield: 76%; mp [ 300 °C; IR (KBr) m cm-1
3252 (NH), 1560 (N=N), 1330 and 1548 (C–N and C=N), 2900–3100 (CH
1
stretching), 1490 (CH bending), 760 (Ar–Cl); H NMR (400 MHz, DMSO-d6) d
ppm: 2.06 (s, 3H, CH3 of pyrazolone ring, 7.40–8.95 (m, 11H, Ar–H), 12.02 (s, 1H,
NH, benzoquinoline ring); 13C NMR (400 MHz, DMSO-d6) d ppm: 13.38 (C-31,
–CH3 group of pyrazolone ring), 111.24–152.12 (22C, Ar–C), 152.60 (C-17, of
pyrazole ring carbon atoms), 156.11, 160.16 (C-30, C-28 of pyrazolone ring carbon
atoms); C24H16ClN7O (453.11): Calc. C, 63.51; H, 3.55; N, 21.60; found: C, 63.52;
H, 3.52; N, 21.65.
Dye 6e (4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo)-2-(3,4-dichlorophenyl)-
:
5-methyl-2,4-dihydropyrazol-3-one): Yield: 84%; mp [ 300 °C. IR (KBr) m cm-1
3242 (NH), 1556 (N=N), 1329 and 1552 (C–N and C=N), 2900–3100 (CH
stretching), 1474 (CH bending), 760–774 (Ar–Cl); 1H NMR (400 MHz, DMSO-d6)
d ppm: 2.04 (s, 3H, CH3 of pyrazolone ring, 7.32–8.97 (m, 10H, Ar–H), 12.04 (s,
1H, NH, benzoquinoline ring); 13C NMR (400 MHz, DMSO-d6) d ppm: 13.32
(C-31, CH3 group of pyrazolone ring), 110.16–150.10 (20C, Ar–C), 152.42 (C-17,
of pyrazole ring carbon atoms), 158.11, 164.76, (C-30, C-28 of pyrazolone ring
carbon atoms); C24H15Cl2N7O (487.07): Calc. C, 59.03; H, 3.10; N, 20.08; found:
C, 59.12; H, 3.16; N, 20.12.
Dye 6f (4-[4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo-3-methyl-5-oxo-
4,5-dihydropyrazol-1-yl]-3-methylbenzenesulfonic acid): Yield: 80%. mp [ 300
°C (DMF). IR (KBr) cm-1: 3252 (NH), 1560 (N=N), 1328 and 1558 (C–N and
C=N), 2900–3100 (CH stretching), 1476 (CH bending). 1H NMR (400 MHz,
DMSO-d6): d = 1.92 (s, 3H, CH3 of pyrazolone ring, 2.20 (s, 3H, CH3 of benzene
ring), 7.64–8.65 (m, 10H, Ar–H), 13.28 (s, 1H, NH, benzoquinoline ring),13C NMR
(100 MHz, DMSO-d6): d = 13.42 (C-32, –CH3 group of pyrazolone ring), 18.11
(C-31, CH3 group of benzene ring), 111.20–150.25 (20C, Ar–C), 152.42 (C-17, of
pyrazole heteroatom ring carbon atoms), 159.25, 160.73, (C-30, C-28 of pyrazolone
heteroatom ring carbon atoms), Anal. Calcd. for C25H18N7NaO4S: C, 56.07; H,3.39;
N, 18.31. Found: C, 56.12; H, 3.34; N, 18.36.
Dye 6g (4-[4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo-3-methyl-5-oxo-
4,5-dihydropyrazol-1-yl]benzenesulfonic acid): Yield: 76%. mp [ 300 °C (DMF).
IR (KBr) cm-1: 3258 (NH), 1554 (N=N), 1332 and 1560 (C–N and C=N),
1
2900–3100 (CH stretching), 1498 (CH bending). H NMR (400 MHz, DMSO-d6):
d = 1.98 (s, 3H, CH3 of pyrazolone ring; 7.69–8.65 (m, 11H, Ar–H), 13.20 (s, 1H,
–NH, benzoquinoline ring), 13C NMR (100 MHz, DMSO-d6): d = 13.40 (C-32,
CH3 group of pyrazolone ring), 110.20–150.25 (23C, Ar–C), 152.65 (C-17, of
123

Synthesis of heterocyclic monoazo dyes
891
pyrazole heteroatom ring carbon atoms), 157.25, 160.12 (C-28, C-30 of pyrazolone
heteroatom ring carbon atoms), Anal. Calcd. for C24H16N7NaO4S: C, 55.28; H,3.09;
N, 18.80. Found: C, 55.36; H, 3.10; N, 18.82.
Dye 6h (4-[4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo-3-methyl-5-oxo-
4,5-dihydropyrazol-1-yl]-2,5-dichlorobenzenesulfonic acid): Yield: 82%. mp [
300 °C (DMF). IR (KBr) cm-1: 3256 (NH), 1562 (N=N), 1330 and 1552 (C–N
1
and C=N), 2900–3100 (CH stretching), 1478 (CH bending), 752–754 (Ar–Cl). H
NMR (400 MHz, DMSO-d6): d = 1.94 (s, 3H, -CH3 of pyrazolone ring, 7.69–8.65
(m, 9H, Ar–H), 13.22 (s, 1H, NH, benzoquinoline ring), 13C NMR (100 MHz,
DMSO-d6): d = 13.42 (C-31, –CH3 group of pyrazolone ring), 110.20–152.25
(23C, Ar–C), 152.65 (C-17, of pyrazole heteroatom ring carbon atoms), 158.25,
162.12, (C-30, C-28 of pyrazolone heteroatom ring carbon atoms), Anal. Calcd. for
C24H14Cl2N7NaO4S: C, 48.83; H,2.39; N, 16.61. Found: C, 48.88; H, 2.42; N,
16.64.
Dye 6i (3-[4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo-3-methyl-5-oxo-4,5-
dihydropyrazol-1-yl]benzenesulfonic acid): Yield: 74%. mp [ 300 °C (DMF). IR
(KBr) cm-1: 3248 (NH), 1560 (N=N), 1328 and 1554 (C–N and C=N), 2900–3100
(CH stretching), 1474 (CH bending). 1H NMR (400 MHz, DMSO-d6): d = 1.92 (s,
3H, CH3 of pyrazolone ring, 7.69–8.65 (m, 9H, Ar–H), 13.22 (s, 1H, NH,
benzoquinoline ring), 13C NMR (100 MHz, DMSO-d6): d = 13.42 (C-31, CH3
group of pyrazolone ring), 111.20–154.25 (23C, Ar–C), 152.65 (C-17, of pyrazole
heteroatom ring carbon atoms), 157.30, 162.16 (C-30, C-28 of pyrazolone
heteroatom ring carbon atoms), Anal. Calcd. for C24H16N7NaO4S: C, 55.28; H,
3.09; N, 18.80. Found: C, 55.34; H, 3.14; N, 18.86.
Dye 6j (4-[4-(1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylazo-3-methyl-5-oxo-4,5-
dihydropyrazol-1-yl]-3-chlorobenzenesulfonic acid): Yield: 86%. mp [ 300 °C
(DMF). IR (KBr) cm-1: 3254 (NH), 1568 (N=N), 1332 and 1552 (C–N and C=N),
2900–3100 (CH stretching), 1480 (CH bending), 752–754 (Ar–Cl). 1H NMR
(400 MHz, DMSO-d6): d = 1.94 (s, 3H, CH3 of pyrazolone ring, 7.69–8.65 (m, 10H,
Ar–H), 13.26 (s, 1H, NH, benzoquinoline ring), 13C NMR (100 MHz, DMSO-d6):
d = 13.44 (C-31, CH3 group of pyrazolone ring), 111.38–150.25 (22C, Ar–C),
152.48 (C-17, of pyrazole heteroatom ring carbon atoms), 156.34, 164.16 (C-30,
C-28 of pyrazolone heteroatom ring carbon atoms), Anal. Calcd. for
C24H16N7NaO4S: C, 55.28; H, 3.09; N, 18.80. Found: C, 55.32; H, 3.14; N, 18.78.
Results and discussion
Chemistry
A variety of routes have been developed for functionalized quinolines and
benzoquinolines; the Vilsmeier [23] approach is among the most efficient for
achieving useful transformations and heteroannulations. Thus, in this communica-
tion we report the synthesis of 2-chlorobenzo[h]quinoline-3-carbaldehyde 2 by
reaction of N-naphthalen-2-yl-acetamide with Vilsmeier reagent and transformation
of the 2-chloro and 3-carbaldehyde groups into different functionality. The required
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N. M. Parekh, K. C. Maheria
N-naphthalen-2-yl-acetamide 1 intermediate was obtained in very good yield by
reaction of 1-naphthylamine with acetyl chloride in the presence of a catalytic
amount of TEA at room temperature, as was confirmed by the disappearance of
–NH2 group and the appearance of –NH and –C=O groups in the IR spectrum,
which contained bands at 3,345 and 1,710 cm-1. Vilsmeier cyclization of
acetanilide 1 was achieved by adding POCl3 to the substrate in DMF at 0–5 °C
followed by heating to 90 °C to afford 2-chlorobenzo[h]quinoline-3-carbaldehyde 2
in good to moderate yield. The IR spectrum of compound 2 contained a sharp and
strong stretching absorption band in the region 1,680–1,700 cm-1 for the aldehyde
group and absorption at approximately 2,720 and 2,830 cm-1 for the aldehyde
proton. Reaction was also confirmed by the presence of –C–N and –C=N of the
benzoquinoline ring, as stretching bands at 1,342 and 1,562 cm-1, respectively. The
carbaldehyde group in quinolines 2 was also transformed into other functionality to
afford new quinolines which are equally important reagents for synthesis of fused
quinoline systems. Compound 2 condensed with hydroxylamine hydrochloride in
the presence of sodium acetate at room temperature to give 2-chlorobenzo[g]quin-
oline-3-carbaldehyde oxime 3, as confirmed by the appearance of a broad –OH
stretching band at 3,400–3,500 cm-1 in the IR spectrum. Compound 3 heated under
reflux with SOCl2 gave 2-chlorobenzo[g]quinoline-3-carbonitrile 4 in good yield,
confirmed by the presence of the –CN group which had a characteristic stretching
band at 2,221 cm-1. Compound 4 on further cyclization with hydrazine hydrate
gave 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine 5; two characteristic bands in
the region 3,200–3,400 cm-1 confirmed the presence of the –NH2 group.
Compound 5 on diazotization then coupling with different phenylpyrazolones
yielded benzoquinoline-based azo compounds 6a–j in high yield. The1H NMR
spectra of 6a–j contained signals at 1.94 ppm, because of the –CH3 group of the
pyrazolone ring, and a singlet at 2.32 because of the –CH3 of the benzene ring. The
spectra of compounds 6a–j contained a singlet at 13.23 ppm, because of the
presence of –NH in the benzoquinoline ring, and the remaining aromatic protons
resonated at 7.28–8.67 ppm as a multiplet. The 13C NMR spectra contained signals
in the range between 13.22 and 13.70, because of the –CH3 group of the pyrazolone
ring, in the range 18.00–21.15, because of the presence of the –CH3 group of
benzene ring, at 160 and 158 ppm, attributed to the carbon atoms of the pyrazolone
heteroatom ring, and at 152.61, attributed to the carbon atoms of the pyrazole
heteroatom ring; all remaining aromatic carbons resonated in the range 118–152.12.
The principle benefit of using the benzoquinoline-based moiety is high percentage
yield and a simple workup procedure which facilitates easy preparation of the
starting material.
Spectral properties of the dyes
The visible absorption spectroscopic properties of the dyes were recorded in water
and DMF and are listed in Table 1. From these results it is clear that the value of
kmax depends on the nature and position of the coupling component used. The color
change observed for each dye is because of alternation of electrons and the presence
of additional substituents.
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Synthesis of heterocyclic monoazo dyes
893
Table 1 Characterization of heterocyclic monoazo dyes 6a–6j
Dye no.
Shade of dyed fiber
kmax (nm)
Coupling component
6a
6b
6c
6d
6e
6f
Yellow
422
440
420
428
430
432
420
430
432
440
p-Toluenephenylmethylpyrazolone
2,5-Dichlorophenylmethylpyrazolone
m-Chlorophenylmethylpyrazolone
o-Chlorophenylmethylpyrazolone
3,4-Dichlorophenylmethylpyrazolone
Dark yellow
Yellow
Yellow
Dark yellow
Yellow
o-Toluenesulfophenylmethylpyrazolone
o-Chlorosulfophenylmethylpyrazolone
2,5-Dichlorosulfophenylmethylpyrazolone
1,3-Sulfophenylmethylpyrazolone
6g
6h
6i
Yellow
Yellow
Yellow
6j
Yellow
1,4-Sulfophenylmethylpyrazolone
Dyeing of fibers
All the dyes 6a–j were applied to silk, wool, nylon, and polyester fibers in 2% (owf)
shade in accordance with the procedures described below. The variation in the
hues of the dyed fibers resulted from changing the coupling components used.
A remarkable degree of levelness after washing indicated good penetration and
excellent affinity of these dyes for the silk, wool, nylon, and polyester fibers.
Dyeing of silk
The dye (0.2 g) was made into a paste with a drop of cold water and then
approximately 80 mL cold water was added and the mixture was stirred well to give
a clear solution. Dye solution (20 mL), acetic acid (2 mL of 10% v/v), and water
18 mL were then diluted to 100 mL. The dye bath temperature was maintained at
30 °C, the silk fabric (2 g) was immersed, and the temperature was increased to
40 °C over 20 min. At this temperature formic acid (1.5 mL of 40% v/v) was added
to the dye bath to achieve good exhaustion. The dyeing was continued for 40 min
more and then the dyed material was washed with cold water and soap solution, and
dried.
Dyeing of wool
Dye (0.2 g) was made into a paste with a few drops of cold water and then
approximately 80 mL cold water was added and the mixture was stirred. Dye
solution (20 mL), acetic acid (1.5 mL of 10% v/v), Glauber’s salt solution (4 mL of
10% w/v), and water (14.4 mL) were then diluted to 100 mL. Wool fabric (2 g) was
immersed in the dye bath at 30 °C and the temperature was increased to 40 °C over
20 min. Sulfuric acid (0.4 mL of 10% v/v) was then added and the dyeing was
continued for 40 min more at the same temperature. The material was then
removed, rinsed with cold water and soap solution, and dried.
123

894
N. M. Parekh, K. C. Maheria
Dyeing of nylon
Dye (0.2 g) was made into a paste with a few drops of cold water and then
approximately 80 mL cold water was added and the mixture was stirred. Dye
solution (20 mL), Glauber’s salt solution (4 mL of 10% w/v), and water (14.4 mL)
were then diluted to 100 mL. Nylon fabric (2 g) was immersed in the dye bath at
30 °C and the temperature was increased to 40 °C over 20 min. Soda ash (Na2CO3)
solution (0.4 mL of 10% v/v) was then added to achieve fixation and the dyeing was
continued for 40 min more at the same temperature. The material was then
removed, rinsed with cold water and soap solution, and dried.
Dyeing of polyester
Dye (0.2 g) was made into a paste with few drops of cold water and then
approximately 40 mL cold water was added and the mixture was stirred, The dye
solution and dispersing agent were then diluted to 100 mL. Polyester fabric (2 g)
was then immersed in the dye bath at 30 °C and the temperature increased to 130 °C
over 20 min. Soda ash (Na2CO3) solution (0.4 mL of 10% v/v) was then added to
achieve fixation and the dyeing was continued for 40 min more at the same
temperature. The material was then removed, rinsed with cold water and soap
solution, and dried.
Wash-off process
The dyed fabrics (silk, wool, nylon, and polyester) were rinsed in warm water,
scoured with 2 g/L Lissapol detergent at 90 °C for 5 min, and rinsed again in warm
water. The dyed fabrics afforded color in the first warm water rinse, less color in the
scouring bath, and almost no color in the second water rinse. This indicated that the
unfixed dyes were easily removed from the fiber surface. Hydrolyzed dye of low
substantivity was released easily from the substrate after two or three washes.
Exhaustion and fixation study
The percentage dye bath exhaustion and percentage dye bath fixation of the dyed
fabric were determined in accordance with a reported method [24]; the results are
summarized in Table 2. It is observed that the percentage exhaustion of 2% dye
ranges from 71 to 75% for silk, from 70 to 75% for wool, from 62 to 69% for nylon,
and from 62 to 69% for polyester. The percentage fixation of 2% dye varied from 85
to 90% for wool, from 83 to 87% for silk, from 85 to 87% for nylon, and from 85 to
87% for polyester.
The data summarized in Table 2 show that the exhaustion and fixation values are
very good. This is because diffusion of the dye molecule within the fabric is rapid,
so the rate of diffusion is high. The lower exhaustion is because of the lower
substantivity, as a result of lower hydrophobicity.
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895
123

896
N. M. Parekh, K. C. Maheria
Fastness properties
The light, wash, and rubbing fastness properties were assessed in accordance with
the standard method [25]. As shown in Table 2, the light fastness rating of all the
dyes was 3–5 for all the fabrics, which shows light fastness is moderate to good. The
wash fastness rating of all the dyes was 3–5 for all the fabrics, which shows wash
fastness is good to excellent. The rubbing (dry and wet) fastness rating of all the
dyes was 3–5 for all the fabrics, which shows rubbing fastness is good to excellent.
Color measurement
The color of the dyes was measured for silk, wool, and nylon fibers and expressed as
CIELAB values. The CIELAB coordinates measured were lightness (L*), chroma
(C*), and hue angle from 0 to 3608 (H); the a* value represents the degree of
redness (positive) and greenness (negative) and the b* value represents the degree of
yellowness (positive) and blueness (negative). A reflectance spectrophotometer was
used for the colorimetric measurements on the dyed samples. K/S values given by
the reflectance spectrophotometer are calculated at kmax and are directly correlated
with the dye concentration on the substrate, in accordance with the Kubelka–Munk
equation [26]:
2
K=S ¼ ð1 ꢁ RÞ =2R;
where K is the absorbance coefficient, S the scattering coefficient, and R the
reflectance ratio.
The results obtained are listed in Table 3.
The color coordinates Table 3 indicate that the dyes have high affinity for silk,
wool, and nylon fibres. The results summarized in Table 3 show that for silk fabric
the dyeing achieved by use of dye 6c was greener (as evidenced by the lower a*
value), duller (as shown by the lower C* value), and lighter (as shown by the higher
L* value) than that achieved with dye 6b. Results are similar when dye 6c is
compared with dye 6b. The dyeing achieved by use of dye 6g was greener, duller,
and darker than that achieved by use of dye 6d. The color strength (K/S) values of
dyes 6a–e for silk fabric followed the order:
6a [ 6b [ 6c [ 6d ꢂ 6e
Dye 6a had the maximum value of color strength (K/S) whereas dye 6e had the
minimum value of color strength. The results summarized in Table 3 show that for
wool fabric the dyeing achieved by use of dye 6c was greener, duller, and darker
than that achieved by use of dye 6b, whereas dye 6d was redder, duller, and darker
than dye 6b. The K/S value of dyes 6a–e for wool fabric followed the order:
6a [ 6b [ 6d [ 6c [ 6e
Antimicrobial activity
The antimicrobial bioassay results presented in Table 4 indicate that all the
compounds tested tended to be more active against Gram-positive bacteria than
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Synthesis of heterocyclic monoazo dyes
897
123

898
N. M. Parekh, K. C. Maheria
against Gram-negative bacteria. Benzoquinoline derivative 6b had excellent activity
(MIC 20 lg/mL, 22 mm zone of inhibition) against the Gram-positive organism S.
aureus. Compounds 6c, 6d, and 6a were half as active (MIC 50 lg/mL) against S.
aureus as compound 6b. Benzoquinolines 6b and 6e had strong inhibitory action
(MIC 20 lg/mL); the zone of inhibition against Gram-positive B. subtilis was
24 mm. The MIC of compound 6e against S. aureus (20 lg/mL) was similar to
those of 6b and 6c but the zone of inhibition was 4 mm less (20 mm). Compound 6d
was half as active (MIC 50 lg/mL) against B. subtilis as the most active analogues
6b and 6e. Compound 6e was found to have promising activity (MIC 50 lg/mL,
20 mm zone of inhibition) against the Gram-negative organism E. coli. Compound
6b had a similar MIC of 50 lg/mL against E. coli with a zone of inhibition (19 mm)
1 mm less than that of 6e. Compound 6h was half as active (MIC 100 lg/mL)
against E. coli as the most active analogue 6e. Compound 6e had remarkable
activity against Gram-negative P. aeruginosa (MIC 50 lg/mL) whereas compounds
6h and 6j had half this activity (MIC 100 lg/mL) against the same bacteria. All the
remaining benzoquinoline derivatives had good to moderate activity, with MIC
values ranging from 20 to 100 lg/mL; some derivatives were found to have weak
activity at higher concentrations (200–500 lg/mL). Figure 2 shows the zones of
inhibition of compounds 6a–j. These results show that compounds 6b and 6e were
the best compounds of the series, with good antibacterial activity against both
Gram-positive and Gram-negative bacteria.
The antifungal bioassay results summarized in Table 4 reveal that benzoquin-
oline derivatives 6b and 6e had antigrowth activity (MIC, 50 lg/mL) against A.
niger. Compounds 6a, 6h, and 6g had activity against the same fungi with similar
growth inhibition diameter (14–19 mm) and half the MIC (100 lg/mL). Compound
Table 4 Antimicrobial activity of heterocyclic azo compounds
Compd
R
Gram negative
Gram positive
Fungal species
E. Coli
P. aeruginosa S. aureus B. subtilis A. niger C. albicans
6a
6b
6c
6d
6e
6f
PTPMP
12 (100)
19 (50)
16 (50)
17 (50)
20 (50)
12 (100)
14 (100)
18 (50)
16 (50)
15 (50)
21 (50)
11 (100)
14 (50)
22 (20)
16 (50)
16 (50)
20 (20)
16 (50)
24 (20)
16 (50)
18 (50)
24 (20)
12 (100) 11 (100)
2:5 DCPMP
MCPMP
14 (50)
12 (50)
16 (50)
22 (50)
24 (50)
14 (50)
19 (50)
23 (50)
OCPMP
3:4 DCMPMP
OTSPMP
1:4 SPMP
2:5 DCSPMP
1:3 SPMP
OCSPMP
12 (100) 11 (100)
14 (100) 12 (100)
16 (100) 14 (100)
12 (100) 12 (100)
6g
6h
6i
\10 (100) \10 (100)
16 (100) 15 (100)
\10 (100) \10 (100)
18 (50)
20 (50)
12 (50)
18 (100)
11 (100) 12 (100)
11 (100) 14 (100)
18 (100) 19 (100)
6j
18 (100)
14 (100)
18 (50)
14 (50)
Ciprofloxacin (100 lg/
disk)
30 (B1)
31 (B1)
32 (B1)
33 (B1)
–
–
Flucanazole (100 lg/
disk)
–
–
–
–
–
–
–
–
30 (B3) 33 (B1)
DMF
–
–
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Synthesis of heterocyclic monoazo dyes
899
Fig. 2 Zones of inhibition of 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine derivatives 6a–j against
Gram-positive and Gram-negative bacteria
Fig. 3 Zones of inhibition of 1H-benzo[g]pyrazolo[3,4-b]quinoline-3-ylamine derivatives 6a–j against
fungi
6b seemed to inhibit C. albicans at 50 lg/mL. Against C. albicans, compounds 6a,
6g, 6h, and 6j had half the activity (100 lg/mL) of the most active analogues tested.
Figure 3 shows the zones of inhibition of compounds 6a–j as antifungal agents. All
the other benzoquinoline derivatives had good to moderate activity with minimum
inhibitory concentrations ranging from 20 to 100 lg/mL. Some of the derivatives
had weak activity at higher concentrations (200–500 lg/mL).
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N. M. Parekh, K. C. Maheria
Conclusion
A series of heterocyclic azo dyes containing the benzoquinoline moiety have been
synthesized by a conventional method and their different properties examined in
solution and applied to silk, wool, nylon and polyester fabrics. The dyes gave
yellow and light yellow shades with very good fastness properties. This type of dye
synthesis is generally convenient and economical. Variations in the hues of the dyed
fabrics result from the both the nature and position of the substituent present on the
coupler ring. The exhaustion and fixation of these dyes are very good; this indicates
the dyes have good affinity for and solubility in the fabric. The remarkable
uniformity of color before and after washing indicates the good penetration of these
dyes and their affinity for the fabric. We have developed efficient and potent
benzoquinoline-based heterocyclic azo compounds which among the active
constituents present in many standard drugs, and are known to increase the
pharmacological activity of molecules. The azo linkage in the compounds increases
the activity of the compounds. The results of screening clearly indicated the
compounds have good antibacterial and antifungal activity similar to that of
standard drugs. Moreover, phenylpyrazolone as coupling component in all
compounds increased antimicrobial activity. Our results indicated that chlorine-
containing benzoquinoline compounds are more efficacious antimicrobial agents
than compounds with sulfonic acid groups in the phenylpyrazolone ring. Hence,
there is enough scope for further study in developing such compounds with good
lead activity. Most of the compounds had moderate to promising activity compared
with standard drugs against all the representative bacterial and fungal strains. In
conclusion, compounds with pyrazolones as coupling components could be useful
for derivatization to develop more effective microbial agents.
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