One-pot synthesis of disperse dyes under microwave irradiation: Dyebath reuse in dyeing of polyester fabrics

Article abstract of DOI:10.3390/molecules17044266

A series of 4-hydroxyphenylazopyrazolopyrimidine disperse dyes were prepared via one-pot reactions of p-hydroxyphenylhydrazone, hydrazine hydrate, and acetylacetone or enaminones using microwave irradiation as an energy source. Structural assignments of t

Full text of DOI:10.3390/molecules17044266

Molecules 2012, 17, 4266-4280; doi:10.3390/molecules17044266
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molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
One-Pot Synthesis of Disperse Dyes Under Microwave
Irradiation: Dyebath Reuse in Dyeing of Polyester Fabrics
Alya M. Al-Etaibi 1,*, Morsy A. El-Apasery 2,3, Huda M. Mahmoud 4 and Nouria A. Al-Awadi 2
1
Natural Science Department, College of Health Science, Public Authority for Applied Education
and Training, P.O. Box 14281, Fayha 72853, Kuwait
2
Chemistry Department, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060,
Kuwait
3
Dyeing, Printing and Textile Auxiliaries Department, Textile Research Division,
National Research Centre, Dokki, Giza 12622, Egypt
4
Department of Biological Sciences, Faculty of Science, Kuwait University, P.O. Box 5969,
Safat 13060, Kuwait
* Author to whom correspondence should be addressed; E-Mail: alya.aletaibi@yahoo.com.
Received: 22 March 2012; in revised form: 28 March 2012 / Accepted: 29 March 2012 /
Published: 10 April 2012
Abstract: A series of 4-hydroxyphenylazopyrazolopyrimidine disperse dyes were prepared
via one-pot reactions of p-hydroxyphenylhydrazone, hydrazine hydrate, and acetylacetone
or enaminones using microwave irradiation as an energy source. Structural assignments
of the dyes were confirmed by X-ray crystallographic structure determination. Instead of
discharging the dyebath after each dyeing cycle, the residual dyebath was spectrophotometrically
analyzed and then pH readjusted for a repeat dyeing with longer time. Fastness of the dyed
samples was measured after each recycle. Most of the dyed fabrics tested displayed good
light fastness and excellent fastness to washing and perspiration. Finally, the biological
activity of the synthesized dyes against Gram positive bacteria, Gram negative bacteria and
yeast were evaluated.
Keywords: dyebath reuse; polyester fiber; disperse dyes; enaminones; microwave; X-ray
crystallographic analysis

Molecules 2012, 17
4267
1. Introduction
The use of disperse dyes has been continuously increased in the textile industry since the discovery
of synthetic fibers. These dyes can be applied to most synthetic fibres using simple exhaustion
techniques. Disperse azo dyes, in particular, cause environmental concern due to their widespread use [1].
Reuse of water in textile processes has been a subject of research and development work in recent
years [2–5]. The incentives for reuse of water are great, since there is a potential for reduction of both
water requirements and wastewater treatment costs. The idea of dyebath renovation and reuse has
started in the middle 1970s when energy costs became a critical factor in overall manufacturing costs.
Dyebath renovation and reuse has been shown to be an effective method of cost reduction. One of the
approaches to reuse the dye bath is to reconstitute the dye bath by adding the required amount of dyes
and chemicals after analyzing the dye liquor. This method is applicable only if the dyeing process does
not change the characters of the residual dye in the bath such as disperse dyes [6]. Dyebath reuse has
long been recognized as a stratagem in pollution prevention and reduction of water, energy, and
chemicals. The principle work on dyebath reuse has included the pilot and laboratory scales dyeing of
polyester with disperse, in pilot scale experiments, dyebaths have been reused over 30 times [7–11]. In
the present study, after the original dyeing process, polyester fibres was dyed with disperse dyes in a
dyebath reuse system using microwave irradiation [12–15]. The objective of the study was to save
water and chemicals and to reduce the quantities of effluent discharged during the dyeing of polyester
fibers. Instead of discharging the dyebath after each dyeing cycle, the residual dyebath was
spectrophotometrically analyzed and then pH readjusted for a repeated dyeing with longer time. Also,
the present study was undertaken to investigate the biological activity of the synthesized dyes against
Escherichia coli and Serratia sp. (Gram negative bacteria), Bacillus subtilus and Staphylococcus
auerus (Gram positive bacteria) and Candida albicans and Saccharomyces cerevisiae (Yeast).
2. Results and Discussion
2.1. Synthesis
Recently we have reported the synthesis of new disperse dyes [16] which showed significant results
in dyeing of polyester fibres. Herein, in an attempt to improve and facilitate the synthesis of these dyes,
we report a new strategy for the preparation of these disperse dyes by using one-step reaction of
p-hydroxyphenylhydrazone 4, hydrazine hydrate, and acetylacetone or enaminones 8a,b.
p-Hydroxyphenylhydrazone 4 was formed by addition under mild conditions of ethyl cyanoacetate
(1) to 4-hydroxybenzenediazonium chloride (2), in ethanolic sodium acetate solution, that readily
affords the corresponding p-hydroxyphenylhydrazone 4. The existence of this hydrazone in the
isomeric form 3 was ruled out based on X-ray crystallographic structure determination. (cf. Scheme 1
and Figure 1) [17]. p-Hydroxyphenylhydrazone 4 undergoes a smooth reaction with hydrazine hydrate
by heating in a focused microwave oven at 120 °C for 5 min to yield 5-amino-4-[(4-hydroxyphenyl)-
hydrazono]-2,4-dihydropyrazol-3-one (5).

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Scheme 1. Preparation of 5-Amino-4-[(4-hydroxyphenyl)hydrazono]-2,4-dihydropyrazol-3-one (5).
O
_
N Cl
+
N
CN
NC
HN
HO
OEt
+
H2C
N
CO2Et
1
2
OH
3
OEt
NC
O
H
N N
N
H
N
HO
NH2
H2N NH2. H2O
N
O
5
N
H
OH
4
Figure 1. Ortep plot of the X-ray crystallographic structure of 4.
We have previously reported that 5 reacts with acetylacetone to yield the pyrazolo[1,5-a]pyrimidine
7 [16]. We now report one-pot synthesis of 7 in better yield from p-hydroxyphenylhydrazone 4,
hydrazine hydrate, and acetylacetone. Compound 7 has the potential of existing in tautomeric form 6.

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4269
The existence of this disperse dye in the tautomeric form 6 was ruled out based on X-ray
crystallographic structure determination. (cf. Scheme 2 and Figure 2) [17].
Scheme 2. Synthesis of 3-(4-Hydroxyphenylazo)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-2-one (7).
H
O
N
N
N
CH3
O
O
N
O
N
H
MW
H2N NH2. H2O
H3C
CH3
CH3
N
4
+
+
6
HO
N
N
CH3
N
7
O
N
H
CH3
Figure 2. Ortep plot of the X-ray crystallographic structure of 7.
We have also previously reported that 5 reacts with enaminones 8a–d to yield the pyrazolo[1,5-
a]pyrimidine derivatives 10a–d [16]. We now report that 10a–d could be directly formed by one-pot
reactions of hydrazone 4, hydrazine hydrate, and enaminones 8a–d in a focused microwave oven at
130 °C for 5 min. The possible formation of regioisomers 9 in the reactions of hydrazone 4, hydrazine
hydrate with enaminones 8a–d is ruled out based on X-ray crystallographic structure determination
(Figure 3). Although these disperse dyes are believed to exist mainly in the keto-form 10a–d, the
predominance of 11a–d (as indicated by the X-ray crystallographic structure determination) is
attributed to stabilization of the products by hydrogen bonding. The fact that compound 7 prefers the
keto-form, while compounds 11a–d prefer the enol-form may be due to the replacement of a methyl
group in compound 7 by aromatic and heteroaromatic substituents with extended conjugation in the
enol-form (cf. Scheme 3) [17].

Molecules 2012, 17
Scheme 3. Synthesis of pyrazolo[1,5-a]pyrimidin-2-ol derivatives (11a–d).
4270
HO
N
N
O
N
Ar
N
O
N
MW
4
H2N NH2. H2O
+
+
H
Ar
NMe2
9a-d
8a-d
8, 11 a, Ar = C6H5
b, Ar = C6H4Cl(p)
HO
N
N
O
N
c, Ar = Fur-2-yl
d, Ar = Thien-2-yl
N
N
H
Ar
10a-d
HO
N
O
N
N
H
N
N
Ar
11a-d
Figure 3. Ortep plot of the X-ray crystallographic structure of 11c.
2.2. Dyeing
The functionalized disperse dyes 5, 7 and 11a–d were applied to polyester fabrics at 1–6% shade by
a high-temperature pressure technique at 130 °C by employing focused microwave irradiation as an
energy source, and a range of color shades was obtained, varying from yellowish-orange to dark
orange. The dyeing on the polyester fabrics were evaluated in terms of their fastness properties
(e.g., fastnesses to washing, perspiration, and light). The physical data for the dyed fibers, given in
Tables 1–3, reflect the efficiency of the microwave irradiation, leading to a large increase in dye uptake

Molecules 2012, 17
4271
and dyeing rate along with a performance of dye leveling and color homogeneity as compared to
conventional methods.
Table 1. Color strengths of azo disperse dyes on polyester fabrics of first dyeing.
Dye
No
5
Color strength (K/S) % Dye o.m.f.
Color shade on
polyester
1
2
3
4
5
6
Yellowish-orange
Pale orange
Dark orange
Dark orange
Orange
1.17
2.19
5.66
5.43
4.40
4.08
2.12
3.79
5.95
5.81
4.64
4.73
2.47
4.09
7.12
7.91
4.85
6.02
2.49
6.71
8.31
8.48
6.01
7.06
4.25
6.91
10.30
10.04
6.25
7.47
4.66
6.96
10.57
12.89
6.56
8.85
7
11a
11b
11c
11d
Orange
Table 2. Color strengths of azo disperse dyes on polyester fabrics of reused dyebaths.
Dye
No
5
Color strength (K/S) % Dye o.m.f.
Color shade on
polyester
1
2
3
4
5
6
Yellowish-orange
Pale orange
Dark orange
Dark orange
Orange
1.02
2.12
4.76
3.06
3.45
2.59
1.67
3.56
5.47
3.99
3.54
3.95
2.42
4.08
5.56
4.30
3.48
4.17
2.09
5.70
6.20
4.76
4.35
5.63
3.28
5.77
6.89
6.66
4.55
6.44
3.99
6.79
8.78
8.59
5.41
8.28
7
11a
11b
11c
11d
Orange
Table 3. Fastness properties of monoazo disperse dyes on polyester fabrics.
Dye Perspiration fastness
Alkaline Acidic
Wash fastness
Light
fastness
Dye o.m.f.
%
Alt
SC
5
SW
Alt
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
SC
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
SW
5
Alt
5
SC
5
SW
5
5
7
5
5
5
5
3–4
2
3
2–3
2–3
2–3
4
2
2–3
3
2–3
2–3
3–4
2–3
2–3
3
5
5
5
5
5
1%
2%
3%
11a
11b
11c
11d
5
5
5
5
5
4
5
5
4–5
4–5
5
5
5
5
5
5
4–5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
4
5
5
4
5
5
5
5
5
5
5
5
4–5
5
5
5
5
5
5
5
4–5
4–5 4–5
5
5
5
5
4–5
4–5 4–5
5
5
5
5
5
5
4
7
11a
11b
11c
11d
5
4–5
4–5
5
4–5 4–5
5
5
5
5
5
5
5
5
5
5
4–5
5
5
5
5
7
5
11a
11b
11c
11d
4–5 4–5
4–5
4–5 4–5
4–5
4–5
4–5
4–5
4–5
5
2–3
2–3
4
5

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4272
Table 3. Cont.
Perspiration fastness
Dye
Dye o.m.f.
Wash fastness
Light
fastness
Alkaline
Acidic
%
Alt
SC
5
4
5
5
4–5
4–5
5
5
4–5
5
SW
5
4
5
5
4–5
4–5
5
5
4–5
5
Alt
5
SC
5
SW
5
Alt
5
SC
5
SW
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
7
5
5
5
5
5
5
5
5
5
5
4
5
5
5
5
5
2–3
2–3
3–4
2–3
2
4–5
2–3
3
4%
5%
6%
11a
11b
11c
11d
5
5
5
5
5
5
5
5
5
5
5
5
4–5
5
5
5
4–5 4–5
5
4–5 4–5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
4–5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
4–5
5
7
11a
11b
11c
11d
5
2–3
2–3
3
4–5 4–5
4–5
4
5
5
5
5
4
5
5
4
7
5
2–3
2–3
3–4
3
11a
11b
11c
11d
4–5 4–5
4–5 4–5
4–5 4–5
4–5
4–5
4–5
4–5
4–5
4–5
5
5
5
4–5
5
5
5
5
4–5
4
5
3
Alt = alteration; SC = staining on cotton; SW = staining on wool.
2.2.1. Color Strength
Most of the auxiliary chemicals used in dyeing of polyester are generally non-reactive and are not
absorbed by the substrate being dyed, so they are not consumed or removed during the dyeing
cycle [18–21]. Reuse of dyebaths generally depends on addition of the amount of dye lost each time. In
this study we planned to reuse the dyebath without any addition of the used dye by increasing the time
of dyeing. The data in Table 1 showed K/S of first dyeing for 60 min at 130 °C in a focused
microwave oven, while that in Table 2 showed K/S of reused dyebath for 90 min at 130 °C in a
focused microwave oven. The physical data and the overall color strength of dyed fabrics between the
first and reused dyeing are shown in Tables 1–3. After reuse of the dyebath, color consistency of
dyeings remained acceptable, which are hard to distinguish with human eyes. In particular, Tables 1
and 2 clearly show that the magnitude of color strength obtained using dye 11d is much larger than
that for 11c.
2.2.2. Color Fastness
Fastness data, obtained by measuring color intensity changes in the dyed polyester fabrics of reused
dyebath, are given in Table 3. It shows the results of color fastness to washing, light, and perspiration,
the rating for color fastness to light and washing were good to excellent, compared to that of the first
dyeing of our previous published work [16]. The rating for color fastness to perspiration was excellent.

Molecules 2012, 17
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These results clearly show that no deterioration of the color fastness occurs over the series of reused
dyebaths. In addition the results obtained showed that dyed fabrics have good fastness properties may
be due to: (a) the absence of solubilizing groups, which affects solubility, and wash ability of the
dye-out of the fabrics; (b) the size of the dye molecule is considered relatively big; (c) the good
intra-fiber diffusion of the dye molecules inside the fabrics.
2.3. Antimicrobial Activities
The antimicrobial activities of the synthesized dyes were screened against selected bacteria and
fungi by the agar well diffusion method and their inhibition zones diameters, given in Table 4, reveal
that all of the tested dyes showed positive antimicrobial activities against at least one of the tested
microorganisms. Two of the compounds, 4 and dye 5, showed strong activities, with significant
inhibition zones >10 mm, against Gram positive bacteria, while others showed moderate to weak
activities against the tested microorganisms. It worth noting that all tested compounds inhibited the
growth of the Candidia albicans.
Table 4. Diameter of the zones of inhibition of the tested compounds that showed weak to
strong antimicrobial against microorganisms.
Inhibition zone diameter (Nearest mm)
prokaryotic organisms
B. subtilus S. aureus E. coli
Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
eukaryotic organisms
Serratia sp. C. albicans S. cerevisiae
Compound
number
Strong antimicrobial
4
5
11(0.1)
11(0.2)
13(0.3)
12(0.1)
NI
NI
4 (0.1)
NI
8(0.3)
1(0.2)
1(0.3)
NI
Moderate antimicrobial
11a
7(0.2)
7(0.2)
NI
NI
1(0.1)
NI
Weak antimicrobial
7
11b
11c
4(0.2)
NI
NI
NI
3(0.1)
30
NI
NI
NI
NI
15
NI
NI
2(0.1)
NI
4(0.1)
2(0.1)
3(0.2)
3(0.2)
NI
NI
NI
2(0)
2(0)
2(0)
7
11d
1(0.1)
Ampicillin *
Cyloheximide **
26
NI
30
(NI) no inhibition, * Ampicillin: Antibacterial (100 mg·mL−1); ** Cycloheximide: Antifungal
(100 mg·mL−1), SD = Standard Deviation.
In addition, Figure 4 shows that Candida albicans re-grew in the formed zone surrounding the wells
contain the compound 4. This may reflect a cytostatic effect of the chemicals rather than cytolytic
effects. The same effect was also noted for the other tested microbes, for instance in Figure 5 the zone
surrounding the wells of the plates inoculated with Staphylococcus aureus showed also cytostatic

Molecules 2012, 17
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effect for the starting chemical. Note that the plate color changed with the increase in the incubation
time, indicating a complete diffusion of the chemical used in the agar as the incubation period increased.
Figure 4. Candida albicans treated with 10 mg·mL−1 of compound 4 after one day “A”,
three day “B” and six days “C” of incubation.
Figure 5. Staphylococcus aureus treated with 10 mg·mL−1 of compound 4 after one day
“A”, three day “B” and six days “C” of incubation.
The cytolytic effects of dyes number 5, 7, and 11a on Candida albicans, where after one, three and
six days of incubation, the inhibition zone did not change is worth noting, while the cytostatic effect of
the same dyes is clear on the plates inoculated with Bacillus subtilus. The growth of B. subtilus
resumed in the inhibited area after six days of incubation which may indicate that as the
concentration/toxicity of dyes number 5, 7, and 11a was reduced due to possible evaporation of these
dyes or diffusion in the media, the effect of these dyes on B. subtilus decreased and the organisms
started growing again. The results obtained for the synthesized compounds in this study support the
findings of the other researchers who showed that pyrazole and pyrazolo[1,5-a]pyrimidine cores have
various biological activities. Pyrazolo[1,5-a]pyrimidines were proved by many researchers to possess
biological effects, including antimicrobial activities (herbicidal and fungicidal activities) [22].
Therefore, the new synthesized classes showed promising results for possessing the potentials to be
utilized for medicinal purposes. Currently, we are inspecting the biological activity of the dyed

Molecules 2012, 17
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polyester with pyrazolopyrimidines disperse dyes against Gram positive bacteria, Gram negative
bacteria and yeast.
3. Experimental
3.1. General
All melting points were recorded on a Gallenkamp apparatus and are uncorrected. IR spectra were
1
13
recorded in KBr disks on a Perkin Elmer System 2000 FT-IR spectrophotometer. H- and C-NMR
spectra were recorded on a Bruker DPX 400 MHz super-conducting NMR spectrometer. Mass spectra
were measured on a VG Auto-spec-Q instrument (high resolution, high performance, tri-sector
GC/MS/MS) and by LC-MS using an Agilent 1100 series LC/MSD with API-ES/APCI ionization
mode. Microanalyses were performed on a LECO CH NS-932 Elemental Analyzer. The microwave
oven used is a single mode cavity Explorer Microwave (CEM Corporation, Matthews, NC, USA) and
irradiate in heavy-walled Pyrex tube (capacity 10 mL and 80 mL for dyeing). The color strengths (K/S)
of the dyed polyester fabrics and the color fastness to light were evaluated at the Dyeing, Printing and
Textile Auxiliaries Department, Textile Research Division, National Research Centre, Giza, Egypt.
X-ray crystals were measured by single crystal X-ray crystallography-Rigaku Rapid II). Copies of
original data can be provided by the authors upon request.
3.2. General Procedure for the Synthesis of Azo Disperse Dyes
Cyano-[(4-hydroxyphenyl)hydrazono]-acetic acid ethyl ester (4). A cold solution of the diazonium salt
[10 mmol; prepared by adding a cold solution of sodium nitrite (0.7 g) in water (5 mL) to a solution of
the p-aminophenol (1.09 g, 10 mmol) in conc. HCl (5 mL)] was added to a cold solution of ethyl
cyanoacetate (1.0 g, 10 mmol) in EtOH (10 mL) containing NaOAc (3 g). The mixture was stirred at
room temperature for 1 h, and the solid precipitate that formed was collected by filtration and
crystallized from EtOH to give brown crystals, yield (87%), m.p. 274 °C; MS: m/z = 233 (M+, 100%),
207 (5%), 159 (40%), 121 (12%), 108 (100%),.81 (25%), 65 (14%); IR: 3420 (OH), 3314 (NH), 2234
1
(CN), 1684 (CO) cm–1; H-NMR (CDCl3) δ = 1.40 (t, 3H, J = 7.2 Hz, CH3). 4.36 (q, 2H, J = 7.2 Hz,
CH2), 5.02 (s, 1H, OH), 6.87–6.91 (m, 2H, arom-H), 7.24–7.28 (m, 2H, arom-H), 13.22 (s, 1H, NH).
5-Amino-4-[(4-hydroxyphenyl)hydrazono]-2,4-dihydropyrazol-3-one (5). A mixture of 3 (2.33 g,
10 mmol) and hydrazine hydrate (1.5 mL) in ethanol (2 mol) was irradiated in a microwave oven at 120 °C
for 5 min. The solid formed was collected and crystallized from ethanol to give reddish-brown crystals,
yield (74%), m.p. 263 °C (lit.[16] m.p. 263 °C).
General procedure for the synthesis of pyrazolo[1,5-a]pyrimidines 7 and 11a–d. A mixture of 4 (2.33 g,
10 mmol), hydrazine hydrate (1.5 mL) and ethanol (2 mL) were irradiated in a microwave oven at 130 °C
for 3 min. Acetylacetone, or enaminones 8a–d (1 mmol) were then added and the heating continued at
130 °C for additional 2 min. The mixture was then poured into ice water. The solid formed was
collected and crystallized from the appropriate solvent (see below).

Molecules 2012, 17
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3-(4-Hydroxyphenylazo)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-2-one (7). Red crystals from DMF,
yield (88%), m.p. 277–278 °C (lit.[16] m.p. 277–278 °C).
3-(4-Hydroxyphenylazo)-7-phenylpyrazolo[1,5-a]pyrimidin-2-ol (11a). Red crystals from DMF, yield
(76%); m.p. 273–274 °C; MS: m/z = 331 (M+, 100%), 238 (50%), 182 (20%); IR: 3432 (OH) cm–1;
1H-NMR (DMSO-d6) δ = 3.36 ppm (br, 1H, OH, D2O exchangeable), 6.90 (d, 2H, J = 7.2), 7.38 (d,
1H, J = 4.2 Hz), 7.64 (m, 3H), 7.71 (d, 2H, J = 7.2 Hz), 8.07 (d, 2H, J = 7.2 Hz), 8.70 (d, 1H, J = 4.2 Hz),
10.02 (s, 1H, OH, D2O exchangeable).
7-(4-Chlorophenyl)-3-(4-hydroxyphenylazo)pyrazolo[1,5-a]pyrimidin-2-ol (11b). Red crystals from
DMF, yield (85%); m.p. 285–286 °C; MS: m/z = 365 (M+, 100%), 336 (6%), 272 (48%), 244 (12%),
1
216 (22%), 180 (7%), 149 (22%), 93 (8%); IR: 3423 (OH) cm–1; H-NMR (DMSO-d6) δ = 3.38 ppm
(br, 1H, OH, D2O exchangeable), 6.88 (d, 2H, J = 8.0 Hz), 7.40 (d, 1H, J = 3.3 Hz), 7.70 (d, 4H,
J = 8.0 Hz), 8.13 (d, 2H, J = 8.4 Hz), 8.69 (d, 1H, J = 3.2 Hz), 10.03 (s, 1H, OH, D2O exchangeable);
13C-NMR (DMSO-d6) δ = 161.2, 158.8, 151.4, 145.0, 144.5, 143.4, 136.0, 131.5, 128.8, 128.6, 122.4,
115.8, 114.2, 110.4.
7-Furan-2-yl-3-(4-hydroxyphenylazo)pyrazolo[1,5-a]pyrimidin-2-ol (11c). Red crystals from DMF,
yield (83%); m.p. 291–292 °C; MS: m/z = 321 (M+, 100%), 228 (36%), 200 (12%), 172 (13%), 116
(6%), 93 (7%); IR: 3435 (OH) cm–1;1H NMR (DMSO-d6) δ = 3.84 (br, 1H, OH, D2O exchangeable),
6.89 (d, 2H, J = 8.4 Hz), 6.95 (s, 1H), 7.59 (d, 1H, J = 4.4 Hz), 7.68 (d, 2H, J = 8.4 Hz), 8.14 (d, 1H,
13
J = 3.2 Hz), 8.22 (s, 1H), 8.63 (d, 1H, J = 4.8 Hz), 10.00 (s, 1H, OH, D2O exchangeable); C-NMR
(DMSO-d6) δ =162.0, 159.0, 150.7, 148.3, 145.5, 143.4, 141.8, 134.7, 122.4, 121.2, 116.3, 115.2,
114.7, 114.0, 105.9.
3-(4-Hydroxyphenylazo)-7-thiophen-2-yl-pyrazolo[1,5-a]pyrimidin-2-ol (11d). Red crystals from
DMF, yield (76%); m.p. 284–285 °C; MS: m/z = 337 (M+, 100%), 308 (5%), 244 (40%), 218 (14%),
1
187 (14%), 121 (13%), 65 (5); IR: 3444 (OH) cm–1; H-NMR (DMSO-d6) δ = 3.49 ppm (s, 1H, OH,
D2O exchangeable), 6.89 (d, 2H, J = 8.8 Hz), 7.40 (t, 1H, J = 4.0 Hz), 7.66 (d, 2H, J = 8.4 Hz), 7.96 (d,
1H, J = 4.8 Hz), 8.19 (d, 1H, J = 4.4 Hz), 8.55 (d, 1H, J = 2.8 Hz), 8.61 (d, 1H, J = 4.8 Hz), 9.99 (s,
13
1H, OH, D2O exchangeable); C-NMR (DMSO-d6) 162.6, 158.7, 150.4, 146.0, 140.4, 136.7, 133.6,
133.5, 129.9, 128.3, 121.7, 116.4, 116.2, 108.3; Anal. Calcd. for C16H11N5O2S (337.4): C 56.96; H
3.29, N 20.76; S 9.50. Found: C 56.88; H 3.30; N 20.71; S 9.46.
3.3. High Temperature Dyeing Method (HT)
3.3.1. Materials
Scoured and bleached polyester 100% (150 130 g/m2, 70/2 denier) was obtained from El-Shourbagy
Co., Egypt. The fabric was treated before dyeing with a solution containing non-ionic detergent
(Hostapal CV, Clariant-Egypt, 5 g/L) and sodium carbonate (2 g/L) in a ratio of 50:1 at 60 °C for 30 min,
then thoroughly washed with water and air dried at room temperature.

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3.3.2. Dyeing
Dyeing of polyester fabrics was carried out at 130 °C for 60 min, under pressure in a focused
microwave oven in a 20:1 liquor ratio and pH 5.5 in the presence of a 1:1 ratio of the dispersing agent
sodium lignin sulphonate and the with a 1–6% shade. After dyeing, the fabrics were thoroughly
washed and then subjected to a surface reduction cleaning [(3 g NaOH + 2 g sodium hydrosulphite)/L].
The samples were heated in this solution for 10 min. at 60 °C and then thoroughly washed and
air-dried. Dyebath exhaustion (%) was determined using a UV/Visible-spectrophotometer.
3.3.3. Dyebath Reuse Procedure
After dyeing, the dyebath was analyzed and reconstituted with the necessary amount of fresh water
to maintain a constant liquor ratio of the original volume. Residual dyebath pH was measured in order
to keep pH at 5.5. Second The dyeing was being carried out by raising the dye bath temperature from
20 to 130 °C at a rate of 30 °C/min and holding at this temperature for 90 min (in order to increase the
dye uptake) before rapidly cooled to 50 at 10 °C/min. The dyed fabrics was then rinsed with cold
water, reduction-cleared using sodium hydroxide (3 g/L) and sodium hydrosulphite (2 g/L) and soaped
with 2% nonionic detergent (pH 8) at 50°C for 15 minutes to improve washing fastness.
3.4. Color Measurements and Analyses
3.4.1. Color Measurements of the Dyed Fabrics
The color yields of the dyed samples were determined by using the light reflectance technique
performed on a Perkin-Elmer (Lambda 3B) UV/VIS Spectrophotometer. The color strengths,
expressed as K/S values, were determined by applying the Kubelka-Mink equation as follows:
K/S = [(1 − R)2 / 2R] − [(1 − Ro)2 / 2Ro]
where R = decimal fraction of the reflectance of the dyed fabric; Ro = decimal fraction of the
reflectance of the undyed fabric; K = absorption coefficient; S = scattering coefficient.
3.4.2. Fastness Testing
The dyed fabrics were tested, employing ISO standard methods [23]. Wash fastness tests were
carried out in accordance with ISO 105-C04 (1989), in which 5 g/L soap and 2 g/L soda ash solution
were used at 95 °C for 30 min in the presence of 10 steel balls (liquor ratio 50:1) and color fastness to
light (carbon arc), ISO 105-B02 (1988).
3.5. Antimicrobial Activities Test
The antimicrobial activities of seven different compounds were tested against six different
microbial cultures using the agar-well diffusion technique [24]. Pure cultures of Escherichia coli and
Serratia sp. (Gram negative bacteria), Bacillus subtilus and Staphylococcus auerus (Gram positive
bacteria) and Candida albicans and Saccharomyces cerevisiae (Yeast) were employed in the test. An
aliquot of each bacterial strain (0.1 mL) was inoculated and spread on nutrient agar (NA) while the

Molecules 2012, 17
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yeast (0.1 mL) was spread on potato dextrose agar (PDA). The inoculated plates were supplied with
100 µL of each of the tested chemicals with a total final concentration of 10 mg·mL−1. The compounds
were placed in 4 mm wells produced by sterile cork borer. The NA plates were incubated at 37 C for
24 h while PDA plates were incubated at 25 C for 24–48 h. The zones of inhibition around the wells
were determined and the averages based on three replicas were recorded. Cycloheximide and
ampicillin both used as references in the experiment, where cycloheximide known to inhibit eukaryotic
organisms while ampicillin inhibits prokaryotes.
All plates were kept for six days after inoculation and the changes in the inhibition zone was
monitored and documented by photography in order to determine on the cytolytic and cytostatic effect
of the tested chemicals.
4. Conclusions
In summary, a series of 4-hydroxyphenylazopyrazolopyrimidine disperse dyes were synthesized via
one-pot synthesis of p-hydroxyphenylhydrazone, hydrazine hydrate, and acetylacetone or enaminones
under microwave irradiation, thus saving synthesis cost and time. Dyebath reuse in the dyeing of
polyester fabrics represents a feasible and economic route to save water and chemical consumption
without sacrificing the quality of the finished goods. The dyed polyester fabrics, which display
yellowish-orange to dark orange hues, were found to have good fastness to light and excellent fastness
to washing and perspiration. Finally, the biological activity of the synthesized dyes against Gram
positive bacteria, Gram negative bacteria and yeast were discussed.
Acknowledgments
The support of the Public Authority for Applied Education and Training, for financing through
project (HS-08-02) and the facilities of AnaLab (SAF) at Kuwait University are gratefully acknowledged.
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Sample Availability: Samples of compounds 4, 5, 7 and 11a–d are available from the authors.
© 2012 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
(http://creativecommons.org/licenses/by/3.0/).