Synthesis, structure, and UV-VIS absorption spectra of azo dyes derived from (dialkylamino)thiazole dimers

Article abstract of DOI:10.1039/b006991o

(Dialkylamino)thiazole dimers act as very strong electron-donating coupling components in azo dyes, the first and second UV-VIS absorption bands of which were observed at λ = 568-737 (ε = 24000-88000) and 404-475 (ε = 9200-52000) nm in dichloromethane, respectively. The azo compounds derived from the (dialkylamino)thiazole dimers having very strong electron-withdrawing moieties such as 4-(perfluoroalkylsulfonyl)phenyls, 2,4-dinitrophenyl, and thiazol-2-yls exhibited a negative solvatochromism. This is the first example of a negative solvatochromism in neutral azo dyes.

Full text of DOI:10.1039/b006991o

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Synthesis, structure, and UV–VIS absorption spectra of azo dyes
derived from (dialkylamino)thiazole dimers†
Jae Joon Kim,a Kazumasa Funabiki,a Hiroshige Muramatsu,a Katsuyoshi Shibata,a
Sung Hoon Kim,b Hisayoshi Shiozaki,c Horst Hartmannd and Masaki Matsui*a
2
a Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu, 501-1193,
Japan. E-mail: matsui@apchem.gifu-u.ac.jp, Fax: +81 58 230 1893, Tel: +81 58 293 2601
b Department of Dyeing and Finishing, College of Engineering, Kyungpook National University,
Taegu, 702-701, Korea
c Technology Research Institute of Osaka Prefecture, Kishibe-naka 1-18-13, Suita, 564-0002,
Japan
d Fachhochschule Merseburg, Fachbereich Chemie, D-06217, Merseburg, Germany
Received (in Cambridge, UK) 29th August 2000, Accepted 12th January 2001
First published as an Advance Article on the web 16th February 2001
(Dialkylamino)thiazole dimers act as very strong electron-donating coupling components in azo dyes, the first and
second UV–VIS absorption bands of which were observed at λ = 568–737 (ε = 24000–88000) and 404–475 (ε = 9200–
52000) nm in dichloromethane, respectively. The azo compounds derived from the (dialkylamino)thiazole dimers
having very strong electron-withdrawing moieties such as 4-(perfluoroalkylsulfonyl)phenyls, 2,4-dinitrophenyl, and
thiazol-2-yls exhibited a negative solvatochromism. This is the first example of a negative solvatochromism in neutral
azo dyes.
Azo dyes contain intramolecular charge-transfer chromo-
phores and therefore, their UV–VIS absorption bands depend
on the combination of electron-donating and -withdrawing
moieties in the molecules.1 Nitrophenyl and thiazoles are
known as electron-withdrawing diazotisation components.
2,3,6,7-Tetrahydro-1H,5H-pyrido[3,2,1-ij]quinoline
(julol-
idine),2 5-acetylamino-2-methoxy-N,N-dialkylanilines,3 and
2,3-dihydroperimidines4 are strong electron-donating coupling
components in azo dyes. Azo dyes derived from these com-
pounds have very important applications. They have been used
as dyestuffs,5 inks,6 dichroic dyes,7 and near-infrared absorbing
dyes.8 Recently, (dialkylamino)thiazole dimers, assumed to be
electron-rich substrates, have been synthesized.9 These com-
pounds can act as novel coupling components in dye synthesis.
Although a few azo dyes derived from (dialkylamino)thiazole
dimers have been synthesized, detailed information on them has
not yet been reported. We report here the synthesis, structure,
and UV–VIS absorption spectra of the azo dyes derived from
(dialkylamino)thiazole dimers.
Fig. 1 UV–VIS absorption spectrum of 3a measured in dichloro-
methane.
and 3Јa, respectively. A series of other azo dyes 4–9 was also
prepared by the same reaction in order to compare their
UV–VIS absorption spectra.
To synthesize an azo dye with a much stronger electron-
withdrawing moiety, the formylthiazolyl azo derivative
3q was reacted with a pyridone to give 3r, as shown in Scheme
2.
Results and discussion
The azo dyes 3 and 3Јa derived from (dialkylamino)thiazole
dimers 2 and 2Ј were synthesized by the diazotisation–coupling
reaction shown in Scheme 1. The coupling reaction of the dia-
zonium salts of 1 with 2 and 2Ј proceeded to give the azo dyes 3
The UV–VIS absorption spectrum of 3a is depicted in Fig. 1.
The first and second absorption bands were observed at λ = 637
and 449 nm in dichloromethane, respectively.
The shape of the absorption bands of 3a did not change in
the range of dye concentration of 1 × 10Ϫ5–1 × 10Ϫ3 mol dmϪ3,
suggesting that the dye 3a did not aggregate at these dye con-
centrations. The UV–VIS absorption spectra of azo dyes 3, 3Јa,
and 4–9 are summarized in Table 1. The azo dyes 3 and 3Јa
showed their first and second absorption bands at λ = 568–737
and 404–475 nm, respectively.
Scheme 1 Synthesis of 3, 3Јa, and 4–9.
† Physical and spectral data for 4a, 4p, 5a, 6a, 6p, 7a, 8a, 8c, 8p, and 9a
are available as supplementary data. For direct electronic access see
http://www.rsc.org/suppdata/p2/b0/b006991o/
DOI: 10.1039/b006991o
J. Chem. Soc., Perkin Trans. 2, 2001, 379–387
This journal is © The Royal Society of Chemistry 2001
379

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The azo dyes 3 and 3Јa derived from the (dialkylamino)-
thiazole dimers showed three characteristic points in their UV–
VIS absorption spectra compared with usual azo dyes such as
4–9.
to exhibit positive solvatochromism.12 Only two types of ionic
azo compounds, 4-[2-(triphenylphosphonio)phenylazo]phenol-
ates and (1-methylpyridinium-2-ylazo)- and (1-methylquino-
linium-2-ylazo)tetracyanocyclopentadienides,
have
been
First, the absorption bands of azo dyes 3 and 3Јa were
bathochromically shifted compared with azo dyes 4–9. The
relationship between the absorption maxima (λmax) of azo dyes
3a, 3Јa, 4a, 5a, 6a, 7a, 8a, and 9a and the oxidation potentials
(Eox) of their coupling components is indicated in Fig. 2. It is
clear that the lower the oxidation potential of the coupling
components, the more bathochromic the absorption band of
their azo derivatives. It is of importance that the Eox of the
(dialkylamino)thiazole dimers 2 and 2Ј are very low (Ϫ0.16 and
Ϫ0.07 V vs. Ag/AgNO3 in CH3CN, respectively) compared with
those of the other coupling components (0.19–0.93 V). The λmax
of the azo dye derived from the (dialkylamino)thiazole mono-
mer, 2,4-bis(dimethylamino)-5-(4-nitrophenylazo)thiazole has
been reported to be 545 nm (ε = 45000) in chloroform,10 being
more hypsochromic than 3c (λmax = 669 nm (ε = 64000) in
dichloromethane). Thus, the azo dyes 3 and 3Јa are compounds
with a bathochromically shifted absorption band arising from
the strong electron-donating nature of the (dialkylamino)thia-
zole dimers.
reported to reveal negative solvatochromic behavior.13 How-
ever, no negative solvatochromism in neutral azo dyes has been
reported so far. The typical solvatochromic effects in 3 are
shown in Fig. 3. The azo dyes 3a, 3p and 3r showed a
negative solvatochromism, while 3c exhibited positive solvato-
chromic behavior. In particular, dye 3r, having very strong
electron-withdrawing pyridone-substituted thiazolylazo and
electron-donating bithiazolyl moieties, showed a large negative
solvatochromism. The solvatochromism of the other azo dyes
was also examined in toluene (molar electron transition energy
ET = 33.9 kcal molϪ1),14 dichloromethane (40.7 kcal molϪ1), and
dimethyl sulfoxide (DMSO, 45.1 kcal molϪ1). These results
are summarized in Table 2. Azo dyes 3a, 3b, 3m, 3p, 3q, 3r, and
3Јa having very strong electron-withdrawing moieties such
as 4-(perfluoroalkylsulfonyl)phenyls, 2,4-dinitrophenyl, and
thiazol-2-yls showed negative solvatochromism. This result is in
contrast to the positive solvatochromism of the near-infrared
absorbing push–pull 5-acetylamino-4-(4-chloro-5-substituted
thiazol-2-ylazo)-2-methoxy-N-(hexan-2-yl)aniline derivative.8
The other azo dyes 3c–l, 3o, and 4a–9a exhibited positive
solvatochromism. The dipole moments (µ) of the azo dyes in
the excited and ground states of their optimized structures were
calculated with the MOPAC AM-1 program. The µ values of 3c
in the ground and excited states were calculated to be 14.58 and
18.98 D, respectively. These calculations are consistent with the
Secondly, the azo dyes 3 and 3Јa showed both positive and
negative solvatochromism depending on the type of electronic
effect in the diazotisation moiety. It is known that azo dyes
normally show a positive solvatochromism.11 Recently, 5-(4-
nitrophenylazo)-2-alkylaminothiazoles, in which the thiazole
moiety acts as a coupling component, have also been reported
Fig. 2 Relationship between the first absorption band and the
ionization potential of couplers. Measured at Au electrodes vs. Ag/Ag+
in acetonitrile containing 0.1 M tetra-n-butylammonium perchlorate
(scan rate: 200 mV sϪ1).
Fig. 3 Solvatochromism of 3a, 3c, 3p, and 3r. The spectra were
measured in toluene (ET: 33.9 kcal molϪ1), diethyl ether (34.5), ethyl
acetate (38.1), dichloromethane (40.7), benzonitrile (41.5), DMSO
(45.1). The compounds 3p and 3r were insoluble in diethyl ether.
Scheme 2 Synthesis of 3r.
380
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Table 1 UV–VIS absorption bands of azo dyes measured in dichloromethane
3, 3Јa, 4–9
Ar2
Compound
Ar1
λmax/nm (ε/l molϪ1 cmϪ1
)
3a
449 (25000)
637 (82000)
3b
3c
3d
3e
3f
450 (23000)
640 (76000)
431 (29000)
669 (64000)
405 (13000)
572 (30000)
423 (15000)
568 (40000)
413 (9200)
582 (27000)
3g
3h
432 (17000)
611 (37000)
436 (18000)
614 (39000)
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Table 1 (Contd.)
3, 3Јa, 4–9
Compound
Ar1
Ar2
λmax/nm (ε/l molϪ1 cmϪ1
)
3i
409 (14000)
583(36000)
3j
438 (21000)
619 (56000)
3k
413 (16000)
587 (38000)
3l
404 (19000)
572 (43000)
3m
3n
3o
3p
435 (32000)
668 (88000)
447 (36000)
721 (69000)
435 (52000)
663 (81000)
441 (35000)
665 (48000)
382
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Table 1 (Contd.)
3, 3Јa, 4–9
Compound
Ar1
Ar2
λmax/nm (ε/l molϪ1 cmϪ1
)
3q
475 (22000)
640 (35000)
3r
457 (51000)
737 (24000)
3Јa
445 (22000)
641 (69000)
4a
4c
4p
545 (41000)
550 (30000)
362 (19000)
648 (11000)
5a
6a
486 (38000)
522 (45000)
6c
6p
7a
529 (32000)
629 (47000)
478 (26000)
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Table 1 (Contd.)
3, 3Јa, 4–9
Compound
Ar1
Ar2
λmax/nm (ε/l molϪ1 cmϪ1
)
8a
552 (22000)
8c
8p
9a
557 (22000)
665 (29000)
423 (52000)
Table 2 Solvatochromism of azo dyes
λmax b/nm
more polar, charge-separated diazamerocyanine structures A,
AЈ, and AЉ could be predominant in the ground state and with
the less polar neutral azo form B in the excited state. This is
different from the reported negative solvatochromic azo com-
pounds, which could have charge-separated azo and neutral
diazamerocyanine structures in the ground and excited states,
respectively.13
Finally, the absorption band of 2-(5-nitrothiazolylazo)
derivative 3p was more hypsochromic than that of the 4-nitro-
phenylazo derivative 3c. In the case of the usual intramolecular
charge-transfer azo dyes, the 2-(5-nitrothiazolylazo) derivatives
are more bathochromic than the 4-nitrophenylazo derivatives.
The 2-(5-nitrothiazolylazo) derivatives 4p [λmax = 648 nm
(ε = 11000)], 6p [λmax = 629 nm (ε = 47000)], and 8p [λmax = 665
nm (ε = 29000)] were much more bathochromic than the
4-nitrophenylazo derivatives 4c [λmax = 550 nm (ε = 30000)], 6c
[λmax = 529 nm (ε = 32000)], and 8c [λmax = 557 nm (ε = 22000)]
respectively, the ∆λmax being 98–108 nm. In contrast, the first
absorption bands of 3p and 3c were observed at λ = 665 and
Solvato-
Dichloro-
methane
Compound
chromisma
Toluene
DMSO
3a
3b
3c
3d
3e
3f
3g
3h
3i
N
N
P
P
P
P
P
P
P
P
P
P
N
—
P
N
N
N
N
P
642
646
663
568
565
574
611
609
576
616
584
570
669
709
656
688
667
792
642
541
472
505
476
553
421
637
640
669
572
568
582
611
614
583
619
587
572
668
721
663
665
640
737
641
545
486
522
478
561
423
634
638
677
581
582
593
614
615
590
620
612
583
657
715
696
650
619
676
639
546
503
538
546
589
434
3j
3k
3l
3m
3n
3o
3p
3q
3r
3Јa
4a
5a
6a
7a
8a
9a
c
669 nm respectively, i.e.,
4 nm hypsochromic for the
2-(5-nitrothiazolylazo) derivative 3p. The positive solvatochro-
mic 4-nitrophenylazo derivative 3c and negative solvatochromic
2-(5-nitrothiazolylazo) derivative 3p could have intramolecular
charge-transfer azo (neutral azo) and charge-separated diaza-
merocyanine structures in their ground states, respectively.
Therefore, the λmax of 3p is not comparable to that of 3c because
of their different chromophores.
P
P
P
P
P
In conclusion, we have synthesized a series of azo dyes
derived from unique coupling components: (dialkylamino)-
thiazole dimers. The bithiazolyl moiety showed a very strong
electron-donating nature. These dyes exhibited their first
and second absorption bands at λ = 568–737 and 404–475
nm in dichloromethane, respectively. The dyes having very
strong electron-withdrawing moieties showed negative solvato-
chromism owing to their charge-separated, polar diazamero-
cyanine structures in the ground state.
a P and N represent positive and negative solvatochromism, respec-
tively. b First absorption band. c Not defined.
positive solvatochromic behavior of 3c. Thus, the electron-
withdrawing nature of the nitro group (σp (NO2) = 0.78) is not
strong enough to cause a negative solvatochromism in the azo
dyes 3. The ground state of the 4-(trifluoromethylsulfonyl)
derivative 3a (σp (CF3SO2) = 0.93)15 was calculated to be
slightly more polar (µ = 15.96 D) than the excited state (15.85
D). The ground state of compound 3r, showing a large negative
solvatochromism, was also calculated to be more polar (24.67
D) than the excited state (23.26 D). The other azo derivatives
showing a negative solvatochromism 3b, 3m, 3p, 3q, and 3Јa
were also calculated to be more polar in their ground states
than in their excited states. The possible mesomeric structures
of 3a in the ground and excited states are depicted in Fig. 4. The
Experimental
Instruments
Melting points were measured with a Yanagimoto micro-
melting-point apparatus. NMR spectra were recorded in CDCl3
on a JEOL α 400 spectrometer using tetramethylsilane as an
384
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Fig. 4 Possible mesomeric structures of 3a.
internal standard. Mass spectra (70 eV, EI) were taken on a
Shimadzu QP 1000 spectrometer. UV–VIS spectra were
mixture. The physical and spectral data of the products are
given below.
measured with a Shimadzu UV 160A spectrometer.
4-Amino-2-(diethylamino)-5-{2-(diethylamino)-5-[4-(trifluoro-
methylsulfonyl)phenylazo]thiazol-4-yl}thiazole 3a. Yield 30%;
mp 218–220 ЊC (Found: C, 45.16; H, 4.69; N, 17.03. C21H26F3-
N7O2S3 requires C, 44.91; H, 4.67; N 17.46%); δH 1.36 (12H, t,
J 7.1), 3.50–3.78 (8H, m), 7.61 (2H, d, J 9.0), 7.83 (2H, d, J 9.0);
m/z 561 (M+; 100%), 444 (14), 428 (19), 398 (32), 263 (30), 226
(17), 135 (53), 99 (29), 77 (34), 72 (56).
Materials
4-(Trifluoromethylsulfonyl)aniline (1a) was purchased from
JRD Fluorochemicals Ltd. 4-Nitroaniline (1c), aniline (1d),
4-anisidine (1e), N,N-dimethylamino-p-phenylenediamine (1f ),
3-nitroaniline (1g), 2-nitroaniline (1h), 2-anisidine (1i),
2-cyanoaniline (1j), 2-(trifluoromethyl)aniline (1k), 2-sec-
butylaniline (1l), 2,4-dinitroaniline (1m), 1-amino-4-nitro-
naphthalene (1n), 4-aminoazobenzene (1o), 2-amino-5-
nitrothiazole (1p), N,N-diethylaniline and 1-naphthylamine
were purchased from Tokyo Kasei Co., Ltd. Julolidine was
purchased from Sigma-Aldrich Co., Ltd. 5-Acetylamino-2-
methoxy-N,N-diethylaniline was supplied by Mitsubishi
Chemical Co., Ltd. 4-(Perfluorohexylsulfonyl)aniline (1b),16
2-amino-4-chloro-5-formylthiazole (1q),17 2,3-dihydro-2,2-
dimethylperimidine,18 3-cyano-1-ethyl-5-hydroxy-4-methyl-2-
pyridone,19 4-amino-2-diethylamino-5-(2-diethylaminothiazol-
4-yl)thiazole (2),9 4-amino-2-morpholino-5-(2-morpholino-
thiazol-4-yl)thiazole (2Ј),9 5-acetylamino-2-methoxy-4-nitro-
phenylazo-N,N-diethylaniline (4c),20 9-(4-nitrophenylazo)-
2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinoline (6c)21 and
1-butyl-3-cyano-5-hydroxy-4-methyl-2-pyridone19 were pre-
pared as described in the literature.
4-Amino-2-(diethylamino)-5-{2-(diethylamino)-5-[4-(perfluoro-
hexylsulfonyl)phenylazo]thiazol-4-yl}thiazole 3b. Yield 18%; mp
235–237 ЊC (Found: C, 38.27; H, 3.22; N, 12.02. C26H26F13-
N7O2S3 requires C, 38.47; H, 3.23; N, 12.08%); δH 1.35 (12H, t,
J 7.2), 3.55–3.71 (8H, m), 7.60 (1H, d, J 8.7), 7.82 (2H, d, J 8.7);
m/z 811 (M+; 18%), 445 (37), 444 (59), 428 (100), 226 (16), 99
(18), 76 (30), 72 (34).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(4-nitro-
phenylazo)thiazol-4-yl]thiazole 3c. Yield 29%; mp 252–253 ЊC
(Found: C, 50.76; H, 5.54; N, 23.24. C20H26N6O2S2 requires C,
50.61; H, 5.52; N, 23.61%); δH 1.35 (12H, t, J 7.2), 3.59–
3.67 (8H, m), 7.52 (2H, d, J 8.2), 8.16 (2H, d, J 8.2); m/z
474 (M+; 100%), 387 (17), 226 (26), 101 (20), 99 (40), 72 (53).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(phenylazo)-
thiazol-4-yl]thiazole 3d. Yield 46%; mp 226–228 ЊC (Found:
C, 56.19; H, 6.43; N, 22.46. C20H27N7S2 requires C, 55.91;
H, 6.33; N, 22.82%); δH 1.30 (6H, t, J 6.6), 1.32 (6H, t, J 6.8),
3.48–3.68 (8H, m), 7.10 (1H, t, J 7.3), 7.35 (2H, t, J 7.3),
7.65 (2H, d, J 7.3); m/z 429 (M+; 100%), 342 (10), 226 (14), 99
(18).
Synthesis of azo dyes 3, 3Ј and 4–9
To a DMF solution (5 ml) of arylamine 1 (1.5 mmol) were
added sodium nitrite (1.5 mmol) and concentrated sulfuric acid
(0.5 ml), and the mixture was stirred at 0 ЊC for 3 h. To the
mixture was added a DMF solution (15 ml) of the coupling
components (1.5 mmol), and the mixture was stirred at room
temperature overnight. After the reaction was complete, the
mixture was poured into water, neutralized, and extracted with
dichloromethane (200 ml × 2). After evaporation of the solvent
in vacuo, the product was isolated by column chromatography
(SiO2, AcOEt) and recrystallised from a chloroform–hexane
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(4-methoxy-
phenylazo)thiazol-4-yl]thiazole 3e. Yield 12%; mp 193–194 ЊC
(Found: C, 54.49; H, 6.30; N, 20.87. C21H29N7OS2 requires C,
54.88; H, 6.36; N, 21.33%); δH 1.26–1.33 (12H, m), 3.56 (8H, q,
J 7.2), 3.84 (3H, s), 6.90 (2H, d, J 9.2), 7.62 (2H, d, J 9.2);
m/z 459 (M+; 100%), 444 (51), 99 (16), 72 (24).
J. Chem. Soc., Perkin Trans. 2, 2001, 379–387
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4-Amino-2-(diethylamino)-5-{2-(diethylamino)-5-[4-(dimethyl-
amino)phenylazo]thiazol-4-yl}thiazole 3f. Yield 21%; mp 231–
232 ЊC (Found: C, 56.20; H, 6.43; N, 22.46. C22H32N8S2 requires
C, 55.90; H, 6.82; N, 23.71%); δH 1.30 (12H, t, J 6.3), 1.53 (6H,
s), 3.45–3.69 (8H, m), 6.99 (2H, s), 7.52 (2H, s); m/z 472 (M+;
100%), 135 (14), 120 (17).
m/z 524 (M+; 100%), 494 (15), 226 (18), 116 (21), 99 (30), 72
(45).
4-Amino-2-(diethylamino)-5-{2-(diethylamino)-5-[4-(phenyl-
azo)phenylazo]thiazol-4-yl}thiazole 3o. Yield 31%; mp 219–
221 ЊC (Found: C, 58.22; H, 5.89; N, 23.26. C26H31N9S2 requires
C, 58.51; H, 5.85; N, 23.62%); δH 1.34 (12H, t, J 7.3), 3.61 (8H,
q, J 7.1), 7.40–7.52 (3H, m), 7.72 (2H, d, J 7.3), 7.89 (2H, d,
J 7.3), 7.94 (2H, d, J 8.8); m/z 533 (M+; 77%), 226 (15), 116 (10),
77 (100).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(3-nitro-
phenylazo)thiazol-4-yl]thiazole 3g. Yield 44%; mp 224–226 ЊC
(Found: C, 50.45; H, 5.61; N, 23.25. C20H26N8O2S2 requires C,
50.61; H, 5.52; N 23.61%); δH 1.35 (12H, t, J 7.3), 3.67 (8H, q,
J 7.3), 7.42 (1H, t, J 7.8), 7.78–7.83 (2H, m), 8.60 (1H, s);
m/z 474 (M+; 100%), 99 (17), 72 (24).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(5-nitro-
thiazol-2-ylazo)thiazol-4-yl]thiazole 3p. Yield 10%; mp 217 ЊC
(decomp.) (Found: C, 42.01; H, 4.77; N, 26.09. C17H23N9O2S3
requires C, 42.39; H, 4.81; N, 26.17%); δH 1.30–1.39 (12H, m),
3.52–3.84 (8H, m), 8.45 (1H, s); m/z 481 (M+; 30%), 436 (28),
338 (68), 307 (71), 293 (93), 72 (93), 55 (100).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(2-nitro-
phenylazo)thiazol-4-yl]thiazole 3h. Yield 14%; mp 212–214 ЊC
(Found: C, 50.94; H, 5.62; N, 23.13. C20H26N6O2S2 requires C,
50.61; H, 5.52; N, 23.61%); δH 1.32 (6H, t, J 5.9), 1.33 (6H, t,
J 5.9), 3.40–3.78 (8H, m), 6.96 (1H, t, J 7.3), 7.40 (1H, t, J 7.3),
7.69 (1H, d, J 7.3), 7.79 (1H, d, J 7.3); m/z 474 (M+; 100%), 340
(25), 226 (19), 116 (43), 99 (36).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(4-chloro-5-
formylthiazol-2-ylazo)thiazol-4-yl]thiazole 3q. Yield 20%; mp
282–284 ЊC (decomp.) (Found: C, 43.77; H, 4.62; N, 2.09.
C18H23ClN8OS3 requires C, 43.32; H, 4.65; N, 22.45%); δH 1.25–
1.40 (12H, m), 3.55–3.76 (8H, m), 9.76 (1H, s); m/z 501 (M++2;
11%), 499 (M+; 26), 498 (97), 336 (65), 307 (67), 293 (90) 72
(100).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(2-methoxy-
phenylazo)thiazol-4-yl]thiazole 3i. Yield 58%; mp 194–195 ЊC
(Found: C, 56.50; H, 6.52; N, 21.68. C21H29N7OS2 requires C,
54.88; H, 6.36; N, 21.33%); δH 1.27–1.33 (12H, m), 3.53–3.58
(8H, m), 3.95 (3H, s), 6.93 (1H, d, J 7.8), 6.95 (1H, t, J 7.8), 7.08
(1H, t, J 7.8), 7.72 (1H, d, J 7.8); m/z 459 (M+; 100%), 352 (23),
267 (11), 116 (38), 99 (39).
4-Amino-2-(morpholino)-5-{2-morpholino-5-[4-(trifluoro-
methylsulfonyl)phenylazo]thiazol-4-yl}thiazole 3Јa. Yield 34%;
mp > 300 ЊC (Found: C, 42.77; H, 3.87; N, 16.21. C21H22F3-
N7O4S3 requires C, 42.78; H, 3.76; N, 16.63%); δH 3.71–
3.75 (8H, m), 3.86 (8H, t, J 4.3), 7.64 (2H, d, J 8.3), 7.88
(2H, d, J 8.3); m/z 589 (M+; 100%), 472 (15), 456 (19), 240
(20).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(2-cyano-
phenylazo)thiazol-4-yl]thiazole 3j. Yield 36%; mp 220–222 ЊC
(Found: C, 55.70; H, 5.89; N, 24.66. C21H26N8S2 requires C,
55.48; H, 5.76; N, 24.65%); δH 1.32 (12H, t, J 7.1), 3.43–3.77
(8H, m), 6.96 (1H, t, J 7.6), 7.43 (1H, t, J 7.6), 7.55 (1H, d,
J 7.6), 7.67–7.76 (1H, m); m/z 454 (M+; 100%), 383 (16), 325
(17), 226 (20), 102 (37), 72 (32).
Synthesis of 4-amino-2-(diethylamino)-5-{2-(diethylamino)-5-[4-
chloro-5-(1-butyl-5-cyano-4-methyl-2,6-dioxo-1,6-dihydro-
pyridin-3(2H)-ylidenemethyl)thiazol-2-ylazo]thiazol-4-yl}-
thiazole (3r)
4-Amino-2-(diethylamino)-5-{2-(diethylamino)-5-[2-(trifluoro-
methyl)phenylazo]thiazol-4-yl}thiazole 3k. Yield 13%; mp 230–
231 ЊC (Found: C, 50.71; H, 5.12; N, 19.79. C21H26F3N7S2
requires C, 50.69; H, 5.27; N, 19.70%); δH 1.31 (12H, t, J 5.8),
3.46–3.78 (8H, m), 7.05 (1H, t, J 7.4), 7.44 (1H, t, J 7.4), 7.60
(1H, d, J 7.4), 7.75–7.85 (1H, m); m/z 497 (M+; 100%), 226 (26),
145 (47), 99 (27).
To an ethanol solution (10 ml) of 4-amino-2-(diethylamino)-5-
[2-(diethylamino)-5-(4-chloro-5-formylthiazol-2-ylazo)thiazol-
4-yl]thiazole 3q (25 mg, 0.05 mmol) was added 1-butyl-3-cyano-
5-hydroxy-4-methyl-2-pyridone (10 mg, 0.05 mmol). The
mixture was refluxed for 1 h. After the reaction was com-
plete, the mixture was concentrated. Column chromato-
graphy (SiO2, AcOEt–Me2CO = 1:1) followed by recrystallis-
ation from a chloroform–hexane mixture gave 10 mg (30%)
of the desired product. Mp 269 ЊC (decomp.) (Found: C,
50.25; H, 5.27; N, 20.20. C29H35ClN10O2S3 requires C, 50.68;
H, 5.13; N, 20.38%); δH 0.90 (3H, t, J 7.3), 1.29–1.47 (16H,
m), 2.46 (3H, s), 3.74–3.86 (8H, m), 3.94 (2H, t, J 7.3), 7.83
(1H, s).
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(2-sec-butyl-
phenylazo)thiazol-4-yl]thiazole 3l. Yield 34%; mp 220–222 ЊC
(Found: C, 59.12; H, 7.12; N, 19.76. C24H35N7S2 requires C,
59.35; H, 7.26; N, 20.19%); δH 0.87 (3H, t, J 7.3), 1.27–1.30
(12H, m), 1.33 (3H, d, J 7.3), 1.57–1.77 (2H, m), 3.52–3.60 (8H,
m), 3.72 (1H, sextet, J 7.3), 6.30–6.54 (1H, m), 7.10 (1H, t,
J 7.1), 7.16 (1H, t, J 7.1), 7.66 (1H, d, J 7.1); m/z 485 (M+; 91%),
339 (41), 267 (67), 72 (100).
Acknowledgements
This work was supported by a Grant-in-aid for Scientific
Research (No. 11650869) from the Ministry of Edu-
cation, Science, Sport and Culture. The authors are grate-
ful to Dr Kazuko Shirai and Professor Dr Masaru Matsuoka
for their elemental analysis measurements and useful
discussions.
4-Amino-2-(diethylamino)-5-[2-(diethylamino)-5-(2,4-dinitro-
phenylazo)thiazol-4-yl]thiazole 3m. Yield 35%; mp 287–
288 ЊC (Found: C, 45.89; H, 4.75; N, 24.04. C20H25N9O4S2
requires C, 46.23; H, 4.85; N, 24.26%); δH 1.37 (12H, t,
J 7.1), 3.48–3.82 (8H, m), 7.68 (1H, d, J 9.3), 8.10 (1H, d, J 9.3),
8.65 (1H, s); m/z 519 (M+; 100%), 340 (24), 116 (43), 99 (43), 72
(65).
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