Ultrasound assisted diazotization and diazo coupling reactions using trichlorotriazine

Article abstract of DOI:10.1134/S1070363214080313

A high rate and efficient procedure for the synthesis of azo dyes has been developed. This concluded the sequential diazotization-diazo condensation of aromatic amines such as 4,4'-sulfonyldianiline with NaNO₂, or trichlorotriazine with couplin

Full text of DOI:10.1134/S1070363214080313

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 8, pp. 1629–1633. © Pleiades Publishing, Ltd., 2014.
Ultrasound Assisted Diazotization and Diazo Coupling Reactions
Using Trichlorotriazine1
Leila Zare Fekria and Mohammad Nikpassandb
a Department of Chemistry, Payame Noor University, PO Box 19395-3697 Tehran, Iran
e-mail: chem_zare@pnu.ac.ir; chem_zare@yahoo.com
b Department of Chemistry, Rasht Branch, Islamic Azad University, Rasht, Iran
Received June 19, 2014
Abstract—A high rate and efficient procedure for the synthesis of azo dyes has been developed. This
concluded the sequential diazotization-diazo condensation of aromatic amines such as 4,4'-sulfonyldianiline
with NaNO2, or trichlorotriazine with coupling agents under ultrasound irradiation at room temperature. This
method applied to several types of coupling agents led to corresponding azo dyes in high yield within short
reaction time. The mild reaction conditions and inexpensive procedure are clear advantages of this method.
DOI: 10.1134/S1070363214080313
INTRODUCTION
hance the reaction of economical and ecological ef-
ficiency [9, 10].
Azo dyes are compounds that contain azo groups
linked to the methane or aromatic sp2-hybridized
carbon atom. Azo dyes make a well-known class of
organic photoactive materials due to their excellent
optical switching properties and high chemical stability
[1, 2]. These materials are widely used in heat transfer
printing and textile industries [3, 4], optical data
storage [5], and photo-refractive polymers [6].
As a part of novel selective and environmentally
friendly method for the heterocyclic and pharma-
ceutical compounds [11–13], herein, we report an
efficient and environmentally friendly reaction of
diazotization and diazo coupling using TCT under
ultrasound irradiation at room temperature.
RESULTS AND DISCUSSION
The diazotization and diazo coupling reactions
usually include protonation of nitrous acid under
strong acidic conditions and azo coupling carried out at
low temperature and involve a nucleophilic coupling
component [7, 8].
Diazonium salts are versatile compounds in organic
chemistry. However, their low thermal stability limits
application of these reagents. According to the novel
method 4,4'- sulfonyldianiline was rapidly converted to
the corresponding azo dyes under ultrasound irradia-
tion with high yield using TCT at room temperature
(Scheme 1).
The conventional acid-base catalyzed synthesis of
azo compounds is not environmentally friendly. The
diazotization and diazo coupling reactions are
complicated usually by side reactions. For example,
reaction temperatures above 10°C generally can
promote phenol formation in aqueous media and
subsequent coupling of phenol with undecomposed
diazonium salts producing azo phenols.
Equimolar amounts of 4,4'-sulfonyldianiline, sodium
nitrite, and TCT in 10 mL of H2O were stirred at 0–
5ºC for 15 min to produce a homogeneous solution of
diazonium salt. This was followed by addition of
equimolar amount of a coupling agent upon stirring.
Progress of the reaction was monitored by TLC. Upon
completion of the reaction (30–45 min), the crude
product was filtered off and recrystallized from EtOH/
H2O.
On the other hand, green chemistry has become a
major driving force for organic chemists to develop
environmentally benign methods for organic com-
pounds. For example, ultrasound irradiation can en-
Influence of TCT amount and nature of solvents
upon reaction time and yield was studied. The cor-
responding data are listed in Table 1.
1 The text was submitted by the authors in English.
1629

1630
LEILA ZARE FEKRI, MOHAMMAD NIKPASSAND
Scheme 1. Ultrasound assisted synthesis of azo dyes.
O O
S
O
O
O
O
Ar−H
S
S
NaNO2, TCT
U.S.
U.S.
N
N
N
N
N2
N2
H2N
NH2
Ar
Ar
I
II
III
OH
OH
OH
OH
CHO
OH
,
,
,
Ar =
,
, etc.
CHO
Scheme 2. Estimated mechanism of azo dyes synthesis.
+ H2O
Cl
OH
OH
N
N
N
N
HO
N
OH
+ HCl
OH
Cl
Cl
N
+
N N
N2
NH2
R
R
R
According to the above data (Table 1), 3 mmol of
TCT and water media was the most efficient for the
synthesis of the azo dye IIIa. An estimated mechanism
of the aqueous TCT catalyzed process is presented in
Scheme 2.
In the course of ongoing research we studied the
catalytic efficiency of K10, KSF, and HY-Zeolite
compared to TCT of azo dye IIIa in water media at
room temperature. The resulting data are presented in
Table 3. TCT as a Bronsted acid promoter proved to be
a better choice than K10, KSF and HY-Zeolite as
Lewis acids in this process.
The optimized conditions were applied to synthesis
of compounds IIIa–IIIi. It is noteworthy that the side
processes were not observed (Table 2).
EXPERIMENTAL
Materials and measurements. All reagents were
purchased from Merck and Fluka. Melting points were
measured by an Electrothermal 9100 apparatus. Ultra-
sound apparatus Astra 3D (9.5 L, 45 kHz frequency
and the transducers from TECNO-GAZ were used. IR
spectra were recorded with a Shimadzu IR-470 spec-
trometer. 1H NMR spectra were measured by a
500 MHz Bruker DRX-500 in CDCl3 or DMSO-d6
solvents with TMS internal standard. Element analysis
was carried out with a Carlo-Erba EA1110CN-NO-S
analyzer and in good agreement with the calculated
values.
Table 1. Effect of solvents and a catalyst amount on the
synthesis of IIIa
Catalyst amount
(mmol) per
Solvent
Time, min
Yield, %
1 mmol substrate
1
3
5
3
3
3
H2O
60
30
30
–
74
86
82
–
H2O
H2O
CH3CN
CHCl3
EtOH
Typical ultrasound assisted synthesis of 4,4'-[4,4'-
sulfonylbis(4,1-phenylene)bis(diazene-2,1-diyl)]diphenol
using TCT.
–
–
60
89
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ULTRASOUND ASSISTED DIAZOTIZATION AND DIAZO COUPLING REACTIONS
Table 2. Ultrasound assisted synthesis of azo dyes IIIa–IIIi
1631
Comp. no.
Structure
Time, min
13
Yield, %
86
IIIa
O O
S
N
N
N
N
HO
HO
OH
IIIb
IIIc
15
11
83
97
O O
S
OH
N
N
N
N
CHO
CHO
O O
S
N
N
N
N
OH
HO
CHO
CHO
IIId
IIIe
11
15
87
85
O O
S
N
N
N
N
OH
HO
O O
S
OH
OH
N
N
MeO
OMe
N
N
CHO
N
CHO
IIIf
12
95
O O
S
N
N
N
HO
OH
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 8 2014

1632
LEILA ZARE FEKRI, MOHAMMAD NIKPASSAND
Table 2. (Contd.)
Comp. no.
Structure
Time, min
11
Yield, %
97
IIIg
O O
S
OH
OH
N
N
N
N
N
N
OH
OH
HO
IIIh
IIIi
14
13
89
86
O O
S
OH
N
N
O
O
O
O
O O
S
NH2
Cl
NH2
N
N
N
N
Cl
4,4'-Sulfonyldianiline (4 mmol, 1.12 g), sodium
nitrite (8 mmol, 0.55 g), 0.05g TCT and 10 mL of H2O
were charged into an open pyrex glass vessel and ultra
sound irradiated in a water bath at room temperature
for 3 minutes to produce a homogeneous diazonium
salt solution. Phenol (8 mmol, 0.75 g) was added to the
diazonium salt and the mixture stirred for 10 minutes.
Upon completion of the diazo coupling reaction, the
crude product was filtered off and washed with water
and recrystallized from EtOH/H2O. 4,4'-[4,4'-Sul-
fonylbis(4,1-phenylene)bis(diazene-2,1-diyl)]diphenol
was accumulated in 13 min, yield 86%.
4,4'-[4,4'-Sulfonylbis(4,1-phenylene)bis(diazene-
2,1-diyl)diphenol] (IIIa). mp 263ºC decomp., IR
(KBr), ν, cm–1: 3254, 2993, 1618, 1600, 1558, 1103.
1H NMR spectrum (500 MHz, DMSO-d6), δH, ppm:
6.9 d (2H, J = 8.7 Hz), 7.8 d (2H, J = 8.7 Hz), 7.9 d
(2H, J = 8.5 Hz), 8.1 d (2H, J = 8.5 Hz), 10.6 s (1H).
Calculated, %: C 62.87; H 3.96; N 12.22. C24H18N4O4S.
Found, %: C 62.77; H 3.69; N 12.06.
3,3'-[4,4'-Sulfonylbis(4,1-phenylene)bis(diazene-
2,1-diyl)]bis(4-hydroxylbenzaldehyde) (IIIb). mp
272ºC decomp., IR (KBr), ν, cm–1: 3363, 2968, 1658,
1600, 1571, 1166. 1H NMR 500 MHz, DMSO-d6), δH,
ppm: 6.1 br.s (1H), 6.93 d (1H, J = 7.2 Hz), 6.95 d
(2H, J = 7.9 Hz), 7.6 d (2H, J = 7.2 Hz), 7.7 d (2H, J =
7.9 Hz, 9.7 s 1H. Calculated, %: C 60.69; H 3.53; N
10.89. C26H18N4O6S. Found, %: C 60.56; H 3.86; N
10.93.
Table 3. Comparative study of synthesis of 3a using K10,
KSF and HY-Zeolite
Amount, mmol
of substrate
Time,
min
Yield,
%
Catalyst
K10
0.1g
0.1g
90
75
70
74
65
86
5,5'-[4,4'-Sulfonylbis(4,1-phenylene)bis(diazene-
2,1-diyl)]bis(2-hydroxybenzaldehyde) (IIIc). mp
268ºC decomp., IR (KBr), ν, cm–1: 3390, 3062, 2856,
1658, 1616, 1581, 1151. 1H NMR spectrum (500 MHz,
DMSO-d6), δH, ppm: 7.2 d (2H, J = 8.9 Hz), 8.02 d
KSF
HY-Zeolite
TCT
0.1g
120
30
3 mmol
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ULTRASOUND ASSISTED DIAZOTIZATION AND DIAZO COUPLING REACTIONS
1633
(4H, J = 8.5 Hz), 8.09 d.d (2H, J = 2.05, J = 8.9 Hz),
8.1 d (4H, J = 8.7 Hz), 8.2 d (2H, J = 2.6 Hz), 10.3 s
(2H), 11.7 br.s (2H). Calculated, %: C 60.69; H 3.53;
N 10.89. C26H18N4O6S. Found, %: C 60.59; H 3.57; N
10.71.
(1H). Calculated, %: C 58.53; H 3.86; N 9.75.
C28H22N4O8S. Found, %: C 58.64; H 3.54; N 9.80.
CONCLUSIONS
An efficient, simple, and environmentally friendly
synthesis of azo dyes under the action of ultrasound
irradiation was developed. The method has some
advantages such as mild reaction conditions, short
reaction time, high yield, and simple procedure.
1,1'-[4,4'-Sulfonylbis(4,1-phenylene)bis(diazene-
2,1-diyl)]dinaphthalen-2-ol (IIId). mp 280ºC
decomp., IR (KBr), ν, cm–1: 3396, 3068, 2927, 1685,
1579, 1500, 1492, 1143. 1H NMR spectrum (500 MHz,
DMSO-d6), δ, ppm: 7.4 t (1H, J = 7.3 Hz), 7.6 t (1H,
J = 7.1 Hz), 7.7 d (1H, J = 7.4 Hz), 7.92 d (1H, J =
9.6 Hz), 7.97 d (2H, J = 8.8 Hz), 8.07 d (2H, J =
10.8 Hz), 8.4 d(1H, J = 8.0 Hz), 15.7 s (1H).
Calculated, %: C 68.80; H 3.97; N 10.03. C32H22N4O4S.
Found, %: C 68.57; H 3.66; N 10.35.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 8 2014