Application of 7-amino coumarins for the synthesis of novel and thermally stable water-insoluble azo-coumarin dyes

Article abstract of DOI:10.1007/s13738-015-0718-5

In this work, a series of novel azo-coumarin dyes were successfully synthesized by the diazotization of 7-amino coumarins followed by coupling with phenol derivatives. The diazotization and subsequent azo-coupling generated the related azo dyes at 0-5 °C in short reaction times with a simple experimental procedure. The spectral analysis of the resulted compounds was confirmed the proposed structures. By this development, the scope of heterocyclic compounds was increased.

Full text of DOI:10.1007/s13738-015-0718-5

J IRAN CHEM SOC
DOI 10.1007/s13738-015-0718-5
ORIGINAL PAPER
Application of 7‑amino coumarins for the synthesis of novel
and thermally stable water‑insoluble azo‑coumarin dyes
Bahador Karami1 · Mahtab Kiani1
Received: 29 April 2015 / Accepted: 8 August 2015
© Iranian Chemical Society 2015
Abstract In this work, a series of novel azo-coumarin
dyes were successfully synthesized by the diazotization
of 7-amino coumarins followed by coupling with phenol
derivatives. The diazotization and subsequent azo-coupling
generated the related azo dyes at 0–5 °C in short reaction
times with a simple experimental procedure. The spectral
analysis of the resulted compounds was confirmed the pro-
posed structures. By this development, the scope of hetero-
cyclic compounds was increased.
Aromatic azo compounds are known to be involved in
various fields such as dyeing of textile fibers, coloring of
different materials like wood, wool, leather, metal foil and
plastic, biological and medical investigations and even the
organic synthesis [6–8]. The use of heterocyclic intermedi-
ates in the synthesis of azo dyes is well established and the
resultant dyes exhibit good tinctorial strength [9]. It is well
known that coumarin compounds and its derivatives play
an important role in organic chemistry [10–13]. They are
the structural unit of several natural products [14]. Their
applications range from pharmaceuticals [15], to optical
brighteners [16] and laser dyes [17]. Also coumarins and
functionalized coumarins have shown activity such as anti-
microbials and chemotherapeutics [18]. While coumarin is
a colorless compound, some of its derivatives exhibit color
and intense fluorescence [19].
Keywords Novel azo-coumarin · Diazotization ·
7-Amino coumarins · Phenol derivatives · Simple
experimental procedure
Introduction
The coumarin compounds have absorption and a lumi-
nous maximum in visible region and have satisfactory
thermo-stability. They have various usages as light absorb-
ing agents or luminous agents in the fields of photochemi-
cal polymerization, solar cells, optical filters, dying, dye
lasers, analysis, etc., [20].
In continuation of our programmatic interest on the het-
erocyclic synthesis [21–25], herein we wish to report a very
simple procedure for synthesis of novel azo-coumarin dyes
obtained by the diazotization of 7-amino coumarins 3 fol-
lowed by coupling with phenol derivatives 5.
Azo dyes represent the single largest chemical class of
industrial colorants. They are synthesized from hetero-
cyclic compounds and have attracted much attention for
their bright and strong color shades ranging from yellow to
greenish blue on synthetic and natural fabrics [1–4].
About 3000 azo dyes are known and are currently in use
worldwide. Most of these compounds are monoazo com-
pounds, which have the common structure unit of –N=N–,
linking two aromatic systems. Despite the toxicity of some
azo dyes, dozens of additional mono azo dyes are applied
in drugs and cosmetics [5].
Experimental
General
* Bahador Karami
karami@mail.yu.ac.ir
1
The chemicals were purchased from Merck and Aldrich
chemical companies. The reactions were monitored by
Department of Chemistry, Yasouj University, P.O. Box 353,
Yasouj 75918-74831, Iran
1 3

J IRAN CHEM SOC
TLC (silica–gel 60 F 254, hexane: EtOAc). Fourier trans-
form infrared (FT-IR) spectroscopy spectra were recorded
on a Shimadzu-470 spectrometer, using KBr pellets and
the melting points were determined on a KRUSS model
[C10H7O2]+, 143 [C10H7O]+, 115 [C9H7]+, 103, 91, 77, 51.
Anal. Calcd. for C20H14N2O3: C, 72.72; H, 4.24; N, 8.48.
Found: C, 72.58; H, 4.13; N, 8.31.
1
instrument. H NMR and 13CNMR spectra were recorded
7‑((2‑Hydroxynaphthalen‑1‑yl)
on a FT-NMR Bruker Avance Ultra Shield Spectrometer
at 400.13 and 100.62 MHz, in which DMSO-d6 was used
as solvent and TMS as the internal standard. UV–visible
spectra were obtained by JASCO V-570 spectrometer. Ele-
mental analyses (C, H, N) were performed with a Heraeus
CHN–O-Rapid analyzer. The results agreed favorably with
the calculated values.
diazenyl)‑4‑methyl‑2H‑chromen‑2‑one (7b)
IR (KBr) (νmax, cm−1): 3432, 1731, 1614, 1498, 1384,
1246, 1127, 1064, 835, 750. UV (CH3OH) (λmax nm)
1
491. HNMR(400 MHZ, DMSO): δH 15.7 (b, 1H, OH),
8.50 (b, 1H, aromatic CH), 7.4–8.00 (m, 7H, aromatic
CH), 6.75 (d, 1H, aromatic CH), 6.35 (s, 1H, CH), 2.45
(s, 3H, CH3). 13CNMR(100 MHZ, DMSO): δC 160.67,
154.95, 152.01, 146.29, 142.60, 133.21, 133.62, 131.28,
129.62, 128.99, 128.40, 127.02, 125.90, 122.26, 117.85,
117.59, 113.98, 113.87, 104.57, 18.71. MS (m/z): 330
[C20H14N2O3]+, 171 [C10H7N2O]+, 159 [C10H7O2]+, 143
[C10H7O]+, 115 [C9H7]+, 103, 89, 77, 51. Anal. Calcd. for
C20H14N2O3: C, 72.72; H, 4.24; N, 8.48. Found: C, 72.45;
H, 4.33; N, 8.22.
General procedure for the synthesis
of 7‑amino‑4‑substituted coumarins 3
β-Ketoester 2 (1 mmol) was added to a mixture of m-amino
phenol 1 (1 mmol) and ZrOCl2·8H2O/SiO2 (0.27 g,
10 mol %) in a screw-cap vial. The mixture was stirred in
a preheated oil bath (90 °C). After completion of the reac-
tion, the resulting solid product was suspended in H2O
(20 ml), filtered and recrystallized from hot EtOH to give
the pure product 3.
3‑((1‑Hydroxynaphthalen‑2‑yl)diazenyl)‑7,8,9,10‑tetrahydr
obenzo[c]chromen‑6‑one (7c)
General procedure for the synthesis of azo‑coumarin
dyes 7a‑h
IR (KBr) (νmax, cm−1): 3413, 2933, 1709, 1521, 1383,
1268, 1097, 1033, 760. UV (CH3OH) (λmax nm) 488.
1HNMR (400 MHZ, DMSO): δH 10.09 (s, 1H, OH),
7.34 (d, J = 8.4 Hz, 2H, aromatic CH), 6.39–7.35 (m,
6H, aromatic CH), 5.92 (s, 1H, aromatic CH), 2.68 (t,
J = 4.4 Hz, 4H, 2CH2), 1.7 (m, J = 2.8 Hz, 4H, 2CH2).
13CNMR (100 MHZ, DMSO): δC 168.25, 159.91, 159.77,
157.96, 154.28, 153.36, 147.41, 142.90, 133.43, 132.74,
130.87, 128.33, 127.06, 111.35, 109.33, 103.15, 101.56,
98.17, 98.06, 30.46, 29.75, 24.02, 21.86. MS (m/z): 370
[C23H18N2O3]+, 199 [C13H11O2]+, 171 [C10H7 N2O]+,
143 [C10H7O]+, 115 [C9H7]+, 97, 71, 57. Anal. Calcd. for
C23H18N2O3: C, 74.59; H, 4.86; N, 7.56. Found: C, 74.34;
H, 4.53; N, 7.75.
The 7-amino coumarins 3 (1 mmol) were dissolved in
concentrated HCl (1 ml) and water (2 ml). The solution
was then cooled to 0–5 °C in ice-bath and maintained at
this temperature. Within 10 min sodium nitrite solution
(0.38 g, 20 ml water) was dropped into mixture with stir-
ring. Coupling component solution prepared by dissolving
5 or 6 (1 mmol) and adding NaOH solution (2 ml, 10 %).
This solution was added portion-wise to the diazonium
solution and was stirred for 2 h. The obtained precipitate
was isolated by filtration and washed with water and cold
ethanol. The crude dye was purified using recrystallization
method.
3‑((2‑Hydroxynaphthalen‑1‑yl)diazenyl)‑7,8,9,10‑tetrahydr
Representative spectral data
obenzo[c]chromen‑6‑one (7d)
7‑((1‑Hydroxynaphthalen‑2‑yl)diazenyl)‑4‑methyl‑2H‑chro
IR (KBr) (νmax, cm−1): 3374, 1706, 1612, 1566, 1509,
men‑2‑one (7a)
1446, 1393, 1255, 1098, 1031, 837, 753. UV (CH3OH)
(λmax nm) 491. HNMR(400 MHZ, DMSO): δH 11.58 (s,
1
IR (KBr) (νmax, cm−1): 3447, 1725, 1613, 1528, 1389, 1271,
1212, 1067, 750. UV (CH3OH) (λmax nm) 474. HNMR
1H, OH), 8.57 (d, J = 8 Hz, 1H, aromatic CH), 8.09 (s,
1H, aromatic CH), 7.7 (m, 3H, aromatic CH), 7.4 (m, 2H,
aromatic CH), 7.1 (d, J = 8 Hz, 1H, aromatic CH), 6.82
(d, J = 9.6 Hz, 1H, aromatic CH), 2.68 (t, J = 8 Hz, 2H,
CH2), 2.3 (t, J = 8 Hz, 2H, CH2), 1.7 (m, 4H, 2CH2). Anal.
Calcd. for C23H18N2O3: C, 74.59; H, 4.86; N, 7.56. Found:
C, 74.47; H, 4.79; N, 7.32.
1
(400 MHZ, DMSO): δH 11.37 (b, 1H, OH), 7.51 (d, 3H,
aromatic CH), 6.64–6.7 (m, 6H, aromatic CH), 6.13 (s, 1H,
CH), 2.34 (s, 3H, CH3). 13CNMR (100 MHZ, DMSO): δC
162.06, 159.40, 159.23, 147.95, 140.46, 140.33, 126.16,
116.94, 112.78, 111.27, 111.16, 99.99, 99.92, 18.473.
MS (m/z): 330 [C20H14N2O3]+, 171 [C10H7N2O]+, 159
1 3

J IRAN CHEM SOC
7‑((2,4‑Dihydroxyphenyl)diazenyl)‑4‑methyl‑2H‑
3‑((2,4‑Dihydroxyphenyl)diazenyl)‑7,8,9,10‑tetrahydro‑
chromen‑2‑one (7e)
6H‑benzo[c]chromen‑6‑one (7g)
IR (KBr) (νmax, cm−1): 3433, 1718, 1611, 1498, 1387,
1243, 1127, 1064, 668, 450. UV (CH3OH) (λmax nm)
430. HNMR(400 MHZ, DMSO): δH 11.94 (b, 1H, OH),
IR (KBr) (νmax, cm−1): 3227, 2934, 1674, 1602, 1425,
1319, 1235, 1160, 1035, 811, 749. UV (CH3OH) (λmax
nm) 418. HNMR (400 MHZ, DMSO): δH 11.99 (s, 1H,
1
1
10.75 (b, 1H, OH), 7.86 (d, 3H, aromatic CH), 7.68 (d, 2H,
aromatic CH), 6.48 (m, 2H, aromatic CH), 1.29 (s, 3H,
CH3). 13CNMR(100 MHZ, DMSO): δC 161.31, 159.29,
154.28, 134.36, 133.14, 130.24, 130.03, 127.84, 126.49,
121.98, 119.91, 116.26, 111.27, 109.97, 104.59, 24.83.
MS (m/z):296 [C16H12N2O4]+, 159 [C10H7O2]+, 137
[C6H5N2O2]+, 109 [C6H5O2]+, 113, 71, 57. Anal. Calcd.
for C16H12N2O4: C, 64.86; H, 4.05; N, 9.46. Found: C,
64.63; H, 4.13; N, 9.33.
OH), 10.71 (s, 1H, OH), 7.65–7.80 (m, 3H, aromatic CH),
6.37–6.51 (m, 3H, aromatic CH), 2.8 (t, 4H, 2CH2), 1.76
(m, J = 7.2 Hz, 4H, 2CH2). 13CNMR (400 MHZ, DMSO):
δC 160.48, 156.92, 151.99, 151.88, 146.87, 132.59,
128.15, 127.99, 124.73, 123.42, 120.56, 118.37, 109.45,
108.24, 102.82, 24.63, 23.83, 20.93, 20.69. MS (m/z): 336
[C19H16N2O4]+, 199 [C13H11O2]+, 137 [C6H5N2O2]+, 109
[C6H5O2]+, 81, 53. Anal. Calcd. for C19H16N2O4: C, 67.85;
H, 4.76; N, 8.33. Found: C, 67.49; H, 4.43; N, 8.14.
7‑((4‑Hydroxybiphenyl‑3‑yl)diazenyl)‑4‑methyl‑2H‑
chromen‑2‑one (7f)
3‑((4‑Hydroxy‑[1,1′‑biphenyl]‑3‑yl)diazenyl)‑7,8,9,10‑
tetrahydro‑6H‑benzo[c]chromen‑6‑one (7h)
IR (KBr) (νmax, cm−1): 3446, 1743, 1621, 1480, 1425,
1383, 1255, 1193, 1148, 885, 756. UV (CH3OH) (λmax
nm) 495. HNMR(400 MHZ, DMSO): δH 10.99 (s, 1H,
IR (KBr) (νmax, cm−1): 3421, 2926, 1714, 1611, 1428,
1262, 1162, 1096, 809, 757. UV (CH3OH) (λmax nm)
487. HNMR (400 MHZ, DMSO): δH 11.03 (s, 1H, OH),
1
1
OH), 8.00 (m, 4H, aromatic CH), 7.81 (dd, j = 2.4 Hz,
J = 7.81 Hz, 1H, aromatic CH), 7.68 (d, J = 7.6 Hz,
2H, aromatic CH), 7.48 (t, J = 7.6 Hz, 2H, aromatic
CH), 7.38 (m, 1H, aromatic CH), 7.2 (d, J = 8.4 Hz,
1H, aromatic CH), 6.49 (s, 1H, CH), 2.48 (s, 3H,
CH3). 13CNMR(400 MHZ, DMSO): δC 160.17, 155.90,
154.09, 153.20, 139.48, 139.20, 133.36, 132.35, 129.46,
129.26, 128.20, 127.66, 126.89, 126.82, 126.71, 126.42,
122.05, 120.21, 119.61, 109.84, 18.65. Anal. Calcd. for
C22H16N2O3: C, 74.15; H, 4.49; N, 7.86. Found: C, 74.02;
H, 4.53; N, 7.69.
7.95–8.09 (m, 4H, aromatic CH), 7.73–7.87 (m, 4H,
aromatic CH), 7.24–7,55 (m, 3H, aromatic CH), 2.9 (t,
J = 6 Hz, 4H, 2CH2), 1.86 (m, J = 3.2 Hz, 4H, 2CH2).
13CNMR (400 MHZ, DMSO): δC 160.45, 154.98, 152.38,
151.92, 146.86, 138.98, 138.63, 132.63, 131.89, 128.96,
127.16, 126.20, 124.87, 124.20, 121.70, 119.68, 118.95,
118.08, 109.14, 24.69, 23.92, 20.92, 20.71. MS (m/z):
396 [C25H20N2O3]+, 199 [C13H11O2]+, 197 [C12H9N2O]+,
169 [C12H9O]+, 141, 115, 77, 53. Anal. Calcd. for
C25H20N2O3: C, 75.75; H, 5.05; N, 7.07. Found: C, 75.61;
H, 4.93; N, 7.15.
Scheme 1 Synthesis of
7-amino coumarins
Me
O
O
Me
OC2H5
H2N
O
O
2a
3a
H2N
OH
Z
rOCl2 .8H2O/SiO2
or
+
Solvent-Free, 90 oC
1
O
O
OC2H5
H2N
O
O
3b
2b
1 3

J IRAN CHEM SOC
m-amino phenol 1 with β-ketoester 2 under thermal and
solvent- free conditions (Scheme 1) [21].
Results and discussion
Subsequently, the novel azo-coumarin dyes 7 were pre-
pared by the diazotization of 7-amino coumarins 3 followed
by coupling with naphthols 5 or phenols 6. (Scheme 2;
Table 1).
Firstly, 7-amino coumarins 3 were synthesized via the
ZrOCl2.8H2O/SiO2-catalyzed Pechmann condensation of
CH3
CH3
OH
O
CH3
O
O
N
N
O
O
N
N
6c
5a
OH
7e
CH3
O
7a
(ii)
(ii)
CH3
OH
N
O
-Cl+N2
O
N
5b
N
N
O
O
OH
6d
4a
(ii)
(ii)
HO
7b
(i)
7f
3a
or
3b
N
N
O
O
(i)
N
O
O
N
OH
HO
5a
6c
7g
(ii)
OH
7c
(ii)
-Cl+N2
O
O
N
O
O
5b
N
6d
N
N
O
O
OH
(ii)
(ii)
4b
HO
7d
OH
7h
HO
OH
6d:
OH
5b:
OH
6c:
5a:
(i)
(ii): NaOH, 0 oC
:
NaNO2, HCl, 0 oC
Scheme 2 Synthesis of azo-coumarin dyes
1 3

J IRAN CHEM SOC
Table 1 Synthesis of azo-coumarin dyes 7a–h by the coupling of
7-amino coumarins and phenol derivatives
appearing in the 6.7–8.5 ppm are attributed to aromatic
rings protons. The proton decoupled 13C NMR spectrum
of 7b showed 20 distinct resonances in agreement with the
proposed structure.
Entry
7a
Product
Mp (˚C)
248–250
Yield (%)a
78
CH3
O
The infrared spectra (IR) of these dyes show intense
carbonyl bands appearing at 1700–1750 cm−1. The broad
bands in region of 3000–3450 cm−1 are attributed to ν
(O–H) vibrations. The peaks appearing at 1000–1350 cm−1
are attributed to ν (C–N) and ν (C–O) stretching vibration.
The spectra also show the existence of (–N=N–) group at
OH
N
N
O
CH3
7b
7c
206–208
170–172
80
53
N
O
O
N
1450–1500 cm−1
.
OH
Conclusions
N
N
O
O
In summary, a new series of azo-coumarin dyes 7a–h were
obtained by coupling of 7-amino coumarins and phenol
derivatives. The use of coumarin as a diazotized aromatic
amine is new. By this development, the scope of heterocy-
clic compounds was increased. Short reaction times, high
yields, a clean process, simple methodology, easy workup
and green conditions are advantages of these protocols.
HO
7d
7e
210–212
132–134
74
54
N
O
O
N
OH
Acknowledgments Financial support from Yasouj University of
Iran is gratefully acknowledged.
CH3
N
O
O
N
OH
References
OH
1. M.A. Satam, R.K. Raut, N. Sekar, Dyes Pigm. 96, 92 (2013)
2. E.O.M. Rufchahi, A.G. Gilani, Dyes Pigm. 95, 632 (2012)
3. W. Herbst, K. Hunger, Industrial organic pigments: production,
properties, applications, 3rd edn. (Wiley-VCH Verlag GmbH &
Co. KGaA, Weinheim, 2004)
4. P. Bamfield, M.G. Hutchings, Chromic phenomena technological
applications of colour chemistry. 2nd edn. The Royal Society of
Chemistry, Cambridge,(2010)
7f
112–114
230–232
58
68
CH3
O
N
N
O
HO
N
7g
5. H. Valizadeh, M. Shomali, S. Nourshargh, R. Mohammad-
Rezaei, Dyes Pigm. 113, 522 (2015)
6. H. Khanmohammadi, K. Rezaeian, M.M. Amini, N.S. Weng,
Dyes Pigm. 98, 557 (2013)
N
O
O
OH
7. J. Koh, A.J. Greaves, Dyes Pigm. 50, 117 (2001)
8. H.S. Bhatti, S. Seshadri, Color. Technol. 120, 151 (2004)
9. F. Karci, N. Sener, M. Yamac, I. S¸ener, A. Demircali, Dyes Pigm.
OH
˙
7h
188–190
71
80, 47 (2009)
10. H. Sawada, Chem. Rev. 96, 779 (1997)
11. P. Moecki, Dyes Pigm. 1, 3 (1980)
12. T. Patonay, G. Litkei, R. Bongar, J. Erdei, Pharat Pharm. 39, 86
(1984)
N
O
O
N
OH
13. F.V. Traven, V.V. Negrebesy, H.L. Vorobjeva, A.E. Carberry, Can.
J. Chem. 75, 377 (1997)
a
Isolated yield
14. R.D.H. Murray, J. Mendezand, S.A. Brown, The Natural Cou‑
marins: Occurrence. Chemistry and Biochemistry (Wiley, New
York, 1982)
15. D. Yu, M.L. Xie, S.L. Morris-Natschke, K.H. Lee, Med. Res.
Rev. 23, 322 (2003)
As a representative sample, the 1H NMR spectrum of 7b
exhibited a sharp singlet identified as methyl (δ = 2.41),
an olefinic C–H of the coumarin ring (δ = 6.40), a sin-
glet corresponded to the OH group (δ = 15.70). The peaks
16. M. Zabradink, The Production and Application of Fluorescent
Brightening Agent (Wiley, New York, 1992)
17. B.B. Raju, T. Varadarajan, Laser Chem. 16, 109 (1995)
1 3

J IRAN CHEM SOC
18. C.J. Wang, Y.J. Hsieh, C.Y. Chu, Y.L. Lin, Cancer Lett. 183, 163
22. B. Karami, M. Kiani, M. Ahmad Hoseini, Chin. J. Catal. 35,
1206 (2014)
(2002)
19. N.R. Ayyangar, K.V. Srinivasan, T. Daniel, Dyes Pigm. 113, 522
23. B. Karami, M. Kiani, J. Chin. Chem. Soc. 61, 213 (2014)
24. B. Karami, S. Khodabakhshi, M. Nikrooz, Polycycl. Aromat.
Comp. 31, 97 (2011)
25. M. Montazerozohori, B. Karami, Helv. Chim. Acta 89, 2922
(2006)
(2015)
20. M. El-Kemary, W. Rettig, Phys. Chem. Chem. Phys. 5, 5221
(2003)
21. B. Karami, M. Kiani, Catal. Commun. 14, 62 (2011)
1 3