Preparation and characterization of diazenyl quinolin-8-ol with trifluoromethyl substituents

Article abstract of DOI:10.1070/MC2006v016n03ABEH002331

The synthesis and properties of new monoazo dyes derived from the diazonium salts of 2-trifluoromethyl phenylamine and 4-chloro-3-trifluoromethyl phenylamine are considered.

Full text of DOI:10.1070/MC2006v016n03ABEH002331

Mendeleev
Communications
Mendeleev Commun., 2006, 16(3), 192–194
Preparation and characterization of diazenyl quinolin-8-ol with trifluoromethyl
substituents
Mohammad R. Yazdanbakhsh, Nosrat O. Mahmoodi* and Shahram Dabiry
Department of Chemistry, University of Guilan, 41335-1914 Rasht, Iran. E-mail: Mahmoodi@guilan.ac.ir
DOI: 10.1070/MC2006v016n03ABEH002331
The synthesis and properties of new monoazo dyes derived from the diazonium salts of 2-trifluoromethyl phenylamine and
4-chloro-3-trifluoromethyl phenylamine are considered.
Azo compounds are the oldest and the most numerous class of
commercial organic dyes. Textile industry is the largest consu-
mer of dye-stuffs. Some azo dyes have been reported to be toxic
but five of the nine synthetic colorants permitted in food in the
United States are monoazo dyes.1,2 Dozens of monoazo dyes are
permitted in drugs and cosmetics.1 Furthermore, azo compounds
have been utilized as analytical reagents3 and they can also be
used as materials for non-linear optics and the storage of optical
information in laser disks.4 As a part of a study on photo-
chromism dyes, which exhibit superior light and gas fastness,5,6
192 Mendeleev Commun. 2006

Mendeleev Commun., 2006, 16(3), 192–194
has not been reported and this type of dyes is relatively rare.
Cl
CF3
CF3
The monoazo chromophore group carrying CF3 derivatives were
synthesised and their properties were investigated.7,8
NO2
NO2
NH2
i
ii
The aggregation behaviour of monoazo sulfonic dyes containing
a trifluoromethyl group at various positions to the azo linkage
in aqueous solutions and the corresponding dyes containing a
methyl group have been investigated by 19F NMR and visible
absorption spectroscopy.14,15 Here, we report the synthesis of
quinolin-8-ol derivatives 1–5. Quinolin-8-ol 11, 5-chloroquinolin-
8-ol 10a and 8-hydroxyquinoline-5-sulfonic acid 10b were
coupled with highly reactive 2-trifluoromethylbenzenediazonium
ion 9 and 4-chloro-3-trifluoromethylbenzene diazonium ion 15
in aqueous solutions at pH 8.5 or 9.5 (Schemes 1 and 2, respec-
tively). At pH 8.4, coupling occurred at the 5-position of 11 and
at the 7-positions of 10a and 10b to give quinolin-8-ol azo dyes
1, 2 and 3, respectively (Scheme 1).†
+ TeCl2
6
7
8
iii
N
CF3
OH
N
N2 Cl
N
11
N
OH
iv
CF3
1
9
R
The 1H NMR spectrum of compound 3 consisted of a virtually
pure mixture of isomers 3a and 3b. Thus, the ratio of the com-
bined integrals for the peaks at d 9.39 (d), 9.04 (d), 8.36 (s),
7.95 (s), 7.93 (d), 7.86 (t), 7.73 (t) for 3b to the corresponding
peaks of 3a (Scheme 1) was 10.6 to 1.8 (ca. 83:17) in equilibrium.
At pH 9.5, coupling occurred at the 5-position of 11 and at the
7-position of 10a (Scheme 2)‡ to give hydroxyl azo dyes 4 and
5, respectively. It was found that the proper choice of diazonium
and coupling constituents is necessary to obtain light-fast dyes.
The influence of fluorine on the fastness properties and colour
v
N
OH
10a R = Cl
10b R = SO3H
...
H
O
N
R
HO
N
N
R
N
N
N
CF3
CF3
2b R = Cl
3b R = SO3H
2a R = Cl
3a R = SO3H
†
Products were characterised by comparison with authentic samples
(IR and NMR spectroscopy, TLC and mp). Melting points are uncorrected
and determined with a Metller Fp5 melting point apparatus. IR spectra
were obtained on a Shimadzu IR-470 instrument. All NMR data were
recorded in CDCl3 on a Bruker Avance 500-MHz spectrometer.
Chemical shifts are reported in ppm (d) using TMS as an internal
standard. The UV-VIS and diffuse reflectance spectra (DRS) were
recorded on a Shimadzu UV-2100 instrument equipped with an integrated
sphere assembly.
Preparation of 1-(trifluoromethyl)-2-nitrobenzene 7. 1-Chloro-2-nitro-
benzene 6 (4 g, 0.025 mol) and 15 ml of freshly distilled pyridine were
placed in a 250 ml round-bottom flask equipped with a reflux condenser
and a magnetic stirrer; then, (CF3)2Te (3.35 g, 0.0126 mol) was added.
The resulting mixture was refluxed at 110–115 °C for 24 h. After
cooling, the reaction mixture was added to a solution of 5 ml conc. HCl
in 50 ml of cooled water. Then, diethyl ether (65 ml) was added, the
organic layer was separated and dried over MgSO4, and the solvent was
evaporated. The crude product was twice recrystallised from 96% EtOH
to give 2.1 g (0.11 mol, 44% yield) of 1-(trifluoromethyl)-2-nitro-
benzene 7; mp 31 °C (lit.,17 32.5 °C); peal yellow crystals. IR (KBr,
n/cm–1): 1550, 1360 (s), 1320, 1150 (s), 1030, 750 (s).
Scheme 1 Reagents and conditions: i, (CF3)2Te, pyridine, 110–115 °C;
ii, 6NaSH, H2O; iii, NaNO2, HCl, 0–5 °C; iv, pH 8.5; v, pH 9.5.
azo dyes 1–5 containing the trifluoromethyl group have been
prepared. Many of these dyes exhibit greater stability to light
than their unfluorinated homologues.7,8 We found that the proper
choice of diazonium and coupling constituents is necessary to
obtain light-fast dyes. In general, however, the gas fastness of
fluorinated azo dyes was found to be excellent. Many of these
dyes exhibit greater stability to light than their unfluorinated
homologues.7
Although many kinds of azo dyes have been synthesised,9–13
quinolin-8-ol derivatives in the presence of the CF3 chromophor
CF3
CF3
CF3
CF3
Cl
Cl
Cl
NO2 H2N
Cl
i
ii
+
O2N
Preparation of 2-(trifluoromethyl)benzenamine 8. 4.56 g (0.019 mol)
of NaSH·9H2O was dissolved in 13 ml of water. To this solution 1.6 g
(0.19 mol) of NaHCO3 was added gradually with stirring. Then, MeOH
(13 ml) was added, and the mixture was well stirred at 15 °C. The
precipitated NaHCO3 was filtered off. To the filtered solution 1.91 g
(0.01 mol) of 1-(trifluoromethyl)-2-nitrobenzene 7 and 13 ml of hot
MeOH were added. The resulting mixture was refluxed in a 250 ml
round-bottom flask equipped with a reflux condenser and a magnetic
stirrer for 30 min. After cooling, the excess precipitated NaHCO3 was
removed and 50 ml of H2O and 10 ml of Et2O were added. The organic
layer was separated and evaporated to give 1.5 g of syrup. To this crude
syrup 15 ml of 20% HCl and 10 ml of Et2O were added, and the acidified
solution was transferred into a separatory funnel and shaken with caution
with a 20% NaOH solution. The neutralised solution was extracted with
20 ml of Et2O, the solvent was removed to leave 1 g (6.7 mmol) of
2-(trifluoromethyl)benzenamine 8 in 68% yield; bp 106–107 °C (lit.,18
105 °C). IR (KBr, n/cm–1): 3500, 3400 (s), 1640 (s), 1580 (w), 1320, 133 (s).
A typical procedure for the preparation of 7-(2-trifluoromethylphenyl-
azo)-5-chloroquinolin-8-ol 2. 500 mg (3 mmol) of 2-(trifluoromethyl)
benzenamine 8 was dissolved in 0.41 ml (7.5 mmol) of 98% H2SO4 in a
100 ml round-bottom flask equipped with a magnetic stirrer, then 3 ml
of H2O was added gradually with stirring. After gentle warming together
with stirring for 10 min to dissolve the entire amine crystalline compound,
a homogeneous solution resulted. The mixture was cooled to 1–2 °C in
an ice-water bath and an aqueous solution of 230 mg (3.25 mmol) of
NaNO2 dissolved in 2 ml of water and cooled to 3 °C was added dropwise
for 20 min. The resulting solution was stirred at 6 °C for 50 min. The
progress of diazotization was monitored by TLC. Finally, the excess of
HNO2 was destroyed by adding solid urea (0.2 g).
18
12
13
14
iii
N
CF3
OH
N
11
Cl
Cl
Cl
N
N
Cl
iv
OH
N
N
F3C
4
15
Cl
...
H
N
O
N
v
N
N
F3C
OH
10a
Cl
5b
HO
N
Cl
N
N
F3C
Cl
5a
Scheme 2 Reagents and conditions: i, HNO3, H2SO4, 50–60 °C; ii, 6NaSH,
H2O; iii, NaNO2, HCl, 0–5 °C; iv, pH 9.5; v, pH 8.5.
Mendeleev Commun. 2006 193

Mendeleev Commun., 2006, 16(3), 192–194
of the dyes are considered on the basis of the dye constituents:
HO
fluorinated couplers and substituted diazonium compounds.
The testing of the dyed fabric for light fastness5 and gas fastness6
was conducted by the standard procedures of the American
Association of Textile Chemists and Colorists. 1-(2-Trifluoro-
methylphenylazo)-2-naphtol 17 prepared from diazotized com-
pound 9 containing trifluoromethyl and 2-naphtol 16 have a
copperish red colour (Scheme 3).§
CF3
N
pH 9.5
9 +
N
OH
17a
16
O
Prepared solution was gradually added to a solution of (appropriate
hydroxyl aryl compound) 540 mg (3 mmol) of 5-chloroquinolin-8-ol
10a in 12 ml of H2O, 7 ml of 96% EtOH and 2 ml of propanol for 15 min.
The aqueous solution was basified to pH ~8.8 by adding an appropriate
amount of an aqueous 20% NaOH solution at 4–5 °C with vigorous
stirring. After stirring for 1 h, the progress of dye preparation was
monitored by TLC (EtOAC–ligroin, 1:3). The precipitated dye was isolated
by filtration and washed with cooled water (200 ml). Purification was
achieved by recrystallization; the solvent system used was EtOH–H2O,
the solution was filtered, reduced in a vacuum and exposed to a high
vacuum to afford 0.91 g (2.66 mmol) of a product 2 as maroon needles
H
N
CF3
N
17b
Scheme 3
The effect of the trifluoromethyl group in the nucleus of azodye
17 is more pronounced than that in the nucleus of quinolin-8-ol
11 couplers. Thus, when quinolin-8-ol 11 is replaced by 2-naphtol,
the colour of the dye is shifted toward the red region.§ As
the distance from trifluoromethyl to –N=N– is increased (for
example, dye 5 with CF3 at the meta position compared to dye
2 with CF3 at the ortho position), the colour of the dye is shifted
toward the red region,§ the colour shifts from maroon to velvety red.
Examination of the MM2 model of dyes 1–5 and 17 indicated the
length of –N=N– to increase in the order: 1 > 17 > 5 > 4 > 2 = 3,
1
(yield 86%), mp 159–160 °C. H NMR, d: 9.00 (d, 1H, H2qu, J 2.9 Hz),
8.49 (d, 1H, H4qu, J 8.2 Hz), 8.08 (d ,1H, H6qu, J 8.2 Hz), 7.80 (d, 1H, H6ph
,
J 7.55 Hz), 7.69 (t, 2H, H4ph, H5ph, J 7.71 Hz), 7.55 (t, 1H, H3qu, J 7.50 Hz),
7.50 (t, 1H, H3ph, J 7.50 Hz), 14.25 (br., 1H).
For 3: 1H NMR, d: 9.76 (d, 1H, H2qu, J 8.53 Hz), 9.06 (d, 1H, H4qu
,
J 4.5 Hz), 8.12 (s, 1H, H6qu), 8.12 (d, 1H, H3ph, J 3.33 Hz), 8.08 (t, 2H,
H4ph, H5ph, J 8.17 Hz), 7.32 (t, 2H, H3qu, H6ph, J 8.17 Hz), 3.90 (s, 1H,
SO3H), 12.20 (br., 1H, OH).
while MINDO/3 examination gives the order 1 > 17 = 5 > 2 > 4 > .
3 16
‡
Preparation of 4-chloro-3-(trifluoromethyl)benzenamine 14. 10 ml
(0.18 mol) of conc. H2SO4 was added dropwise to 10 ml (0.17 mol) of
conc. HNO3 in 250 ml flask. The resulting mixture was cooled to 20 °C
on ice bath. Then, 9 g (0.05 mol) of 1-chloro-2-(trifluoromethyl) benzene
18 was added (in small portions) at 30–35 °C. When the addition of 18
was completed and the mixture temperature became equal to room tem-
perature, the reaction mixture was stirred and heated to 50–60 °C for
30 min until no more brownish gas was evolved. After cooling to 20 °C,
200 ml of cooled water was added. 1-Chloro-2-(trifluoromethyl)-4-nitro-
benzene 12 and 2-chloro-1-(trifluoromethyl)-3-nitrobenzene 13 were
precipitated. The crude material was recrystallised from 100 ml of EtOH
to give pure compound 13 as a precipitate, and compound 12 was
recovered and purified from filtrate. The crude material was washed with
cooled water and dried to give 6.8 g (0.03 mol; 60% yield); mp 65 °C.
The same procedure as used for the preparation of 8 was applied, 6.8 g
(0.03 mol) of 12, 13.5 g (0.057 mol) of NaSH·9H2O, 4.8 g (0.057 mol)
of NaHCO3 and 39 ml of MeOH were refluxed for 60 min (see the
procedure for 8) to give 3.9 g (0.02 mol; 65% yield) of 14; mp 38 °C. IR
(KBr, n/cm–1): 3400, 3300 (br.), 1620 (s), 1480, 1440 (s), 1320–1100 (s),
1020 (s), 820 (s).
This study was supported in part by the Research Committee
of Guilan University.
References
1
D. M. Marmion, Handbook of US Colorants, 3rd edn., Wiley, New York,
1991, p. 23.
2
R. K. Johnson and F. J. Lichlenberger, in Developments in Food Colours,
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4
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7
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8
9
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2, pp. 492, 972.
1
For 5: H NMR, d: 9.05 (d, 1H, H2qu, J 3.5 Hz), 8.61 (d, 1H, H4qu, J
8.10 Hz), 8.12 (s, 1H, H6qu), 8.08 (s, 1H, H2qu), 7.87 (d, 1H, H6ph, J 7.82 Hz),
7.69–7.50 (m, 2H, H4ph, H5ph, H3qu), 14.45 (br., 1H, OH).
§
For 1: yield, 92%; mp 180–181 °C; colour, red; light fastness, very
good. UV, lmax/nm: 475. IR (KBr, n/cm–1): 3400–3200 (st), 1500 (st),
1560 (m), 1050 (st), 1220 (m), 1120 (st), 1300 (st), 760 (st).
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For 2: yield, 86%; mp 159–160°C; colour, maroon; light fastness, very
good. UV (lmax/nm): 485. IR (KBr, n/cm–1): 3500–3000 (br.), 1500 (m),
1600 (m), 1540 (w), 1520 (w), 1360 (w), 1300 (st), 1100 (st), 760 (st).
For 3: yield, 87%; mp 250 °C; colour, orange; light fastness, very good.
UV (lmax/nm): 330 (strong), 475 (weak). IR (KBr, n/cm–1): 3500–3200
(st), 3100 (w), 1620 (st), 1550 (st), 1500 (st), 1300 (m), 1220 (m), 1180
(m), 1120 (st), 1040 (w), 750 (st).
For 4: yield, 83%; mp 157 °C; colour, light red; light fastness, very
good. UV (lmax/nm): 480. IR (KBr, n/cm–1): 3500–3000 (br.), 1600 (m),
1500 (m), 1300 (st), 1240 (m), 900 (wm), 800 (w).
For 5: yield, 90%; mp 196–198 °C; colour, velvety red; light fastness,
excellent. UV (lmax/nm): 500. IR (KBr, n/cm–1): 3500–3100 (br.), 1560 (m),
1500 (w), 1400 (m), 1300 (m), 1240 (m), 1100 (w), 900 (m), 820 (st).
For 17: yield, 90%; mp 157 °C; colour, copperish red; light fastness,
very good. UV (lmax/nm): 490. IR (KBr, n/cm–1): 3400–3000 (br.), 1600 (s),
1540 (w), 1500–1450 (m), 1030 (w), 1250 (m), 1100–1300 (s), 820(s).
Received: 14th February 2006; Com. 06/2673
The English language edited by Valentin V. Makhlyarchuk, Moscow
Typeset by Sergei I. Ososkov, Moscow
Printed in the UK by Cambrian Printers, Aberystwyth
194 Mendeleev Commun. 2006