Synthetic potentials of heptamethine merocyanine dyes containing an active chlorine atom: reactivity towards nucleophiles

Article abstract of DOI:10.1002/ejoc.200900564

The reactivity of heptamethine merocyanine dyes that contain an active chlorine atom at a meso position of the polymethine chain towards nucleophiles is investigated for the first time. The reactivity differs completely from that of cationic cyanine dyes

Full text of DOI:10.1002/ejoc.200900564

FULL PAPER
DOI: 10.1002/ejoc.200900564
Synthetic Potentials of Heptamethine Merocyanine Dyes Containing an Active
Chlorine Atom: Reactivity towards Nucleophiles
Tzveta Gospodova,[a] Jivka Rashkova,[a] Diana Ivanova,[a] Lilia Viteva,*[a]
Christine Duprat,[b] Marie-Rose Mazières,[b] Snezhana Bakalova,[a] and Jose Kaneti[a]
Keywords: Dyes/Pigments / Cyanines / Reaction mechanisms / UV/Vis spectroscopy / Photophysics
The reactivity of heptamethine merocyanine dyes that con-
tain an active chlorine atom at a meso position of the poly-
methine chain towards nucleophiles is investigated for the
first time. The reactivity differs completely from that of cat-
ionic cyanine dyes and is consistent with a concerted SNAr
addition–elimination mechanism. This mechanism is ad-
ditionally supported by the performed DFT calculations in
the gas phase and in solution. The observed dependence of
the reaction on the type of the nucleophilic agents is dis-
cussed in terms of Pearson’s theory. Additional diversification
of and improvement in the stability of the ramified merocyan-
ines is achieved in reactions with methyl-substituted quater-
nary salts of nitrogen-containing heterocycles. The photo-
physical characteristics of the novel dyes are reported and
compared with those of the parent merocyanine.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
influence of the substituents at the central and terminal po-
sitions of the polymethine chain on the photophysical char-
Introduction
As a result of the wide use of merocyanines as new or- acteristics of the new dyes is discussed.
ganic materials, their structural design and reactivity are in
the focus of cyanine dyes chemistry.[1–9] In a recent paper
we reported a simple and efficient enolate-based synthetic
approach to rigidized mono- and bis(heptamethine) mero-
cyanines with variable donor and acceptor groups pos-
Results and Discussion
Synthesis of Ramified Heptamethine Merocyanine Dyes
sessing a chlorine substituent at a meso position.[10] De-
pending on the reaction conditions, the interaction of the
new dyes with 3-ethyl-2-methyl benzothiazol-3-ium iodide
afforded products with lengthened and/or ramified poly-
methine chains. X-ray crystallographic analysis revealed
that the ramification occurs through a sulfur bridge as a
result of a ring-opening reaction.
As a first stage of this study we examined the possibility
for ramification of the merocyanine chain by replacement
of the chlorine atom by various nucleophiles. Direct substi-
tution of the nucleofugal chlorine atom in heptamethine cy-
anines is well recognized and has been used as a common
access to functionalized dyes for near-infrared fluorescence
labelling. According to the literature, the reaction occurs
readily with nucleophiles having good electron-donor abil-
ity through a SRN1 mechanistic pathway.[12–16] In agreement
with the postulated mechanism, the substitution is found to
be efficient in solvents promoting the single electron-trans-
fer process (e.g., DMF).[17] Alternatively, in media where
such a transfer is not favoured, for example, aqueous
alcohol, the substitution is completely suppressed.[18]
Note that although direct functionalization of the chlo-
rine-substituted heptamethine cyanines is well documen-
ted,[12–17] surprisingly and to the best of our knowledge no
examples are reported for analogous merocyanine dyes.
The reaction was examined by using the readily available
merocyanine MC1 with a diethylamino end group and a set
of -NH, -OH and -SH nucleophiles. In a single case, the
merocyanine MC2 possessing a piperidine moiety at a ter-
minal position was applied.
Later, we demonstrated that the main product of the
basic hydrolysis of 3-ethyl-2-methyl benzothiazol-3-ium
iodide, as usually used in the syntheses of dyes, is N-(2-
mercaptophenyl)-N-ethylacetamide, which is the actual spe-
cies accomplishing the nucleophilic attack.[11]
In this paper, we report a convenient preparation of
multifunctional merocyanine dyes by consecutive, two-stage
ramification/prolongation of the polymethine chain of the
readily available meso-chlorine-substituted precursors, em-
ploying in each reaction step a different nucleophile. The
[a] Institute of Organic Chemistry with Centre of Phytochemistry,
Bulgarian Academy of Sciences,
1113 Sofia, Bulgaria
[b] Synthèse et Physicochimie de Molécules d’Intérêt Biologique,
UMR 5068, Université Paul Sabatier,
118 route de Narbonne, 31062 Toulouse Cedex 9, France
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Our attempts to perform the substitution under SRN
1
Table 1. Synthesis of ramified, through a sulfur linker, heptame-
thine merocyanines.
conditions as described for the cyanine dyes series[12–17]
completely failed with all tested nucleophiles. On the con-
trary, in boiling ethanol in the presence of a piperidine base
as recently reported,[10] we found dependence of the reac-
Compound (ratio)
Base
MC1/ArSH
Time
[min]
Yield[d]
[%]
1a(2a)[a] (86:14)
piperidine
piperidine
piperidine
piperidine
piperidine
1:5
1:5
1:5
1:5
1:5
1:5
1:1
1:5
1:5
1:3
1:3
1:1
1:5
60
90
60
30
60
30
30
30
60
30
30
30
180
93
91
95
84
98
81
80
88
76
89
72
95
63
tion course on the type of the nucleophilic agent. Thus, the 1b(2b)[a] (91:9)
1d(2d)[a] (80:20)
use of -NH (morpholine, piperidine) and -OH (phenol, p-
1e(2e)[a] (90:10)
aminophenol) nucleophiles did not result in successful ram-
1f(2f)[a] (86:14)
ification. Instead, as proved by 1H NMR spectroscopic
1g(2g)[a] (80:20)
2c
2d
2e
2f
piperidine
analysis, a partial exchange of the terminal diethylamino
group by a piperidino one occurred.
Under identical conditions all tested -SH nucleophiles
(Scheme 1, Table 1) replaced the chlorine atom efficiently,
and the conversion was complete within 0.5–3 h (TLC mon-
itoring of the reaction). As noted above, the nucleophilic 3[c]
substitution was accompanied by a partial exchange of the
end group, thus giving a mixture of products 1 and 2 in
different proportions. Our attempt to avoid this side reac-
tion by decreasing the base from 1.5 to 0.3 equivalents was
unsuccessful. An exception was observed in the case of 2h,
where the crude target compound was obtained in 96% pu-
rity (NMR spectroscopic analysis).
diethylamine
diethylamine
diethylamine
diethylamine
diethylamine
piperidine
2g
2h[b]
piperidine
[a] Compounds were isolated as mixtures of 1 and 2 with a strong
predominance of products 1 (1H NMR spectroscopic analysis).
[b] Obtained in the presence of piperidine (0.3 equiv.). [c] Starting
from merocyanine MC2. [d] Yield after a general workup procedure
followed by washing with dry diethyl ether (see Experimental Sec-
tion).
Next, we examined the possibility to direct the reaction reaction mixtures demonstrated, however, that although
entirely to products 1 by increasing the quantity of the pip- compounds 1 strongly predominated, small proportions of
1
eridine base to 5 equivalents. The H NMR spectra of the products 2 were still present. Because these proportions did
Scheme 1. Synthesis of ramified merocyanine dyes using -SH nucleophiles.
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Synthetic Potentials of Heptamethine Merocyanine Dyes
not change with prolongation of the reaction time indicated quaternary salts of nitrogen-containing heterocycles. We ex-
in Table 1, they most probably reflect the thermodynamic pected that the successful proceeding of this reaction will
stability of the products. Unfortunately, our efforts to purify contribute both to the synthetic diversity and the stability
compounds 1 by recrystallization were unsuccessful.
of the new dyes.[10]
As might be expected, the observed complication due to
The condensation with benzothiazolium salts bearing
the end group exchange was prevented by performing the different functional groups was carried out in boiling pyr-
1
reaction in the presence of an amine, identical with the ter- idine[10] (Scheme 2, Table 2). H NMR spectroscopic analy-
minal amino group in the merocyanine precursor. Follow- sis of the reaction products revealed however that in some
ing this improved protocol, pure samples of compounds 2 of the cases studied the chain prolongation is accompanied
were obtained from MC1 in the presence of diethylamine. by replacement of the aromatic residue at the central posi-
Alternatively, merocyanine MC2 with a terminal piperidino tion by the corresponding mercaptan, in situ produced from
group gave compound 3 in good yield and purity in the hydrolysis of the quaternized heterocycle.[11]
presence of piperidine. The experimental data are summa-
Table 2. Conversion of ramified heptamethine merocyanines into
their nona analogues.
rized in Table 1.
The reaction with the tested -SH nucleophiles occurs in
Compound
Ratio 4/5
Time [min]
Yield [%]
high to moderate yields. The reaction time and the excess
amount of the nucleophilic agent are specified for each par-
ticular case. In general, the target products Ϫ individual or
as a mixture of compounds 1 and 2 Ϫ have up to 95%
purity (NMR spectroscopic data) after a common workup
4a[a]
4b[a]
4c
84:26
63:37
100:0
100:0
100:0
100:0
100:0
10
10
10
15
15
25
30
30
32
36
55
54
64
62
4d
4e[b]
procedure followed by trituration with diethyl ether. As 4f[b]
4g
mentioned above, attempts at purification by recrystalli-
zation or by flash chromatography decreased significantly
the reaction yields and in some cases worsened the purities
of the products obviously as a result of their chemical insta-
bility.
[a] Compounds were isolated as mixtures of 4 and 5. Ratio 4/5 was
1
determined by H NMR spectroscopic analysis of the crude prod-
ucts. [b] Two equivalents of the quaternary salt are employed.
The observed side reaction was efficiently avoided by use
of quaternary 1-ethyl-2,3,3-trimethyl-3H-indolium iodide
(compounds 4e–g) where such a competition does not oc-
cur. Note that the new dyes with elongated polymethine
chains have substantially enhanced stability compared to
their ramified precursors. They are purified by column
chromatography on silica and are stable both in solution
and the solid state.
All new compounds are deep-red-coloured substances.
Their structures were undoubtedly proven by elemental and
1
spectral analysis (mass, H and 13C NMR spectra). Note,
whereas the products are stable for months in the solid
state, their stability in solution is poor.
Conversion of the Ramified Heptamethine Merocyanines
into Nonamethine Dyes
Photophysical Properties
With a series of ramified merocyanines in hand we exam-
ined the possibility for elongation of the polyene chain by
The absorption and fluorescence characteristics of new
employing a condensation reaction with methyl-substituted dyes 2 and 4 are shown in Table 3. The values for the parent
Scheme 2. Elongation of the polymethine chain of the ramified heptamethine merocyanines.
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L. Viteva et al.
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chlorine-containing merocyanine MC1 are given for com- with about 2000 cm–1 in the case of compounds 4a–d and
parison. All the studied compounds in ethanol solution at 1350 cm–1 for compounds 4e–g. The effect on the energy of
room temperature absorb and fluoresce in the visible region the fluorescence Franck–Condon transition is less pro-
of the spectrum. Their longest wavelength absorption max- nounced. It is shifted to the red region with approximately
ima are between 16000 and 19000 cm–1 with molar absorp- 1000 cm–1.
tivities in the range 32000–45000 Lmol–1 cm–1. Correspond-
ingly, the fluorescence Franck–Condon transitions lie be-
Reaction Mechanism
tween 14200 and 15500 cm–1. The fluorescence quantum
Finally, we would like to comment on the mechanistic
aspects of the reaction under consideration. As reported,
the conditions where we achieved a successful nucleophilic
replacement of the meso-chlorine atom Ϫ 96% ethanol in
the presence of an organic base Ϫ are apparently inconsist-
ent with the SRN1 reaction mechanism widely accepted for
analogous cationic cyanine dyes.
Taking into account our experimental data and the elec-
tronic structure of the merocyanines, delocalized π elec-
tronic systems,[3] we presumed that the examined nucleo-
philic substitution follows a SNAr addition–elimination
pathway as depicted in Scheme 3.
yields are uniformly low. Some representative absorption
and fluorescence spectra of ramified merocyanines 2 and 4
are shown in Figure 1.
Table 3. Absorption and fluorescence characteristics of the studied
compounds at 293 K in ethanol: ν is the energy of the longest
˜
abs
wavelength absorption Franck–Condon transition; ε is the molar
absorptivity; ν is the energy of the fluorescence Franck–Condon
˜
F
transition; QF is the fluorescence quantum yield.
Compound
ν
ε
ν
QF
˜
˜
abs
F
[cm–1]
[Lmol–1 cm–1] [cm–1]
MCl
2c
2d
2e
2f
18650
18830
18880
18660
18970
18940
18870
16780
16950
16670
16720
17390
17240
17300
32000
38600
39890
41360
39320
41580
35770
40780
38200
36600
32230
43810
40820
45280
15630
15410
15390
15240
15460
15470
15230
14080
14630
14290
14710
14290
14180
14180
0.03
0.03
0.03
0.02
0.03
0.03
0.03
0.01
0.01
0.02
0.01
0.01
0.01
0.01
2g
2h
4a
4b
4c
4d
4e
4f
4g
Scheme 3. Probable mechanism of the nucleophilic replacement of
the meso-chlorine atom.
We further performed DFT calculations to study the
mechanism by using the B3PW91 functional as im-
plemented in Gaussian 03, which show somewhat different
mechanistic pictures for “hard” and “soft” nucleophiles.
The “hard” -OH and -NH reagents do not form any inter-
mediate adduct, and the nucleophilic attack occurs concert-
edly on the “front side”[19] of a tetrahedral transition struc-
ture. In contrast, attack of the “soft” -SH nucleophiles (Fig-
ure 2) leads to formation of two transition structures with
close geometry parameters, separated by a shallow interme-
diate. However, account for solvent in the DFT calculations
indicates concertedness and front-side substitution also by
“soft” -SH nucleophiles. Details of these calculations will
be published elsewhere.
Figure 1. Normalized absorption spectra of compound 2e (curve
1); 4e (curve 2) and 4a (curve 3) and corrected fluorescence spectra
of compound 2e (curve 4); 4e (curve 5) and 4a (curve 6) in ethanol
(concentration 1ϫ10–5 Lmol–1) at room temperature.
The observed dependence of the reactivity on the type
As seen from Table 3, ramification of the polymethine of the nucleophilic agent could be rationalized in terms of
chain through a sulfur linkage (compounds 2) does not ap- Pearson’s theory.[20] Most probably -NH and -OH nucleo-
preciably change the basic properties of the parent meso- philes failed to react owing to their “harder” character than
chlorine-substituted dye MC1, independently of the type of the -SH reagents. It the latter case, the better fit between
residue attached. To the contrary, the prolongation of the the “soft” nucleophilic centre – sulfur atom – and the “soft”
conjugated system leads to a bathochromic shift in the electrophile – delocalized merocyanine chain – seems to be
longest wavelength absorption Franck–Condon transition of crucial importance for a successful reaction.
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Synthetic Potentials of Heptamethine Merocyanine Dyes
with a UV/Vis Spectrophotometer Perkin–Elmer Lambda 25. The
corrected fluorescence spectra were measured with a Perkin–Elmer
LS 55 spectrofluorimeter (photomultiplier R928). The fluorescence
quantum yield (QF) was determined relative to that of the dye
Rhodamine 6G (QF = 0.58 in ethanol)[21] and Cresyl Violet (QF
=
0.53 in methanol).[22]
General Experimental Procedure for the Synthesis of Ramified Hep-
tamethine Merocyanines 1–3: The optimized reaction parameters Ϫ
ratio between the reactants and the reaction time Ϫ for each par-
ticular case are shown in Table 1. To a solution of the starting mer-
ocyanine MC (1 mmol) and the corresponding thiol (ArSH) in 96%
EtOH (35 mL) was dropwise added the organic base (piperidine or
diethylamine, 5 mmol). The reaction was kept under reflux for the
time indicated and then cooled to room temperature. After removal
of the solvent in vacuo the residue was dissolved in dichlorometh-
ane (50 mL) and washed consecutively with 10% NaOH (5 mL)
and water (2ϫ20 mL). The organic layer was dried with Na2SO4
and filtered, and the solvent was evaporated under reduced pres-
sure. Trituration of the crude products with dry ethyl ether
(1ϫ10 mL) afforded the ramified merocyanines as mixtures of 1
and 2 (synthesis in the presence of piperidine) or as individual com-
pounds 2 and 3 (synthesis in the presence of diethylamine). All new
products (mixtures or individual adducts) have satisfactory purity
according to 1H NMR and elemental analysis (for individual com-
pounds).
Figure 2. Transition structure for the attack of thiophenol on a
model merocyanine MC1, optimized at the B3PW91/6-31G* level
of theory in the gas phase.
Conclusions
In this paper we investigated for the first time the reactiv-
ity of rigidized heptamethine merocyanine dyes containing
a nucleofugal chlorine atom at a meso position of the poly-
methine chain. Our experimental data clearly demonstrated
that the reactivity towards nucleophiles differs completely
from that reported for analogous cationic cyanine dyes and
is consistent with a front-side SNAr addition–elimination
mechanism. This mechanism is further supported by the
performed DFT calculations. Additional diversification of
the ramified merocyanine dyes concerning both the length
of the polymethine chain and its functionality was achieved
by employing a condensation reaction with methyl-substi-
tuted quaternary salts of nitrogen-containing heterocycles.
This structural modification improves significantly the sta-
bility of the ramified precursors both in solution and in the
solid state.
Our study reveals the synthetic utility of the chlorine-
substituted merocyanine dyes and contributes to their de-
sign and synthetic diversity. It offers an easy and general
approach to the ramified, through a sulfur linker, and rigid-
ized analogues.
As a result of the present investigation a new series of
merocyanine dyes, differently functionalized at the central
and the terminal positions, were synthesized in good to
moderate yields.
NMR chemical shift assignments of the new merocyanines follow
the numbering system shown below:
1
The H and 13C NMR chemical shifts of compounds 1 are taken
from the spectra of the corresponding mixtures with compounds 2,
where products 1 strongly predominate (see Table 1). Compounds
2a and 2b were detected as minor impurities of compounds 1a and
1b and are not described. The ratios 1/2, indicated in Table 1, were
determined by integration of the signals for the 7-H protons, having
sufficiently different chemical shifts.
1-(Naphthalen-2-yl)-3-[2-(phenylthio)-3-(piperidin-1-ylmethylene)cyclo-
pent-1-enyl]prop-2-en-1-one (1a): Starting from merocyanine MC1
(365 mg, 1 mmol) and benzenethiol (550 mg, 5 mmol), the general
procedure afforded a spectroscopically pure mixture of 1a/2a
(86:14) as a dark-red solid. Yield: 420 mg (93%). Rf = 0.45 (diethyl
ether/hexane, 1:1). MS (EI, 9 eV): m/z = 451 [M]+. 1H NMR
(CDCl3): δ = 1.53 (br., 6 H, 3 CH2pip), 2.93–3.06 (m, 4 H, 2
CH2c-pent), 3.27 (br., 4 H, 2 CH2pip), 6.66 (s, 1 H, 7-H), 6.87 (d, J
= 15 Hz, 1 H, 2-H), 7.19–7.21 (m, 5 H, Harom), 7.51–7.63 (m, 2 H,
Harom), 7.87–8.07 (m, 4 H, Harom), 8.25 (d, J = 15 Hz, 1 H, 3-H),
8.42 (s, 1 H, Harom) ppm. 13C NMR (CDCl3, DEPT): δ = 24.25,
26.06 (CH2pip), 27.27, 30.52 (CH2c-pent), 51.61 (CH2pip), 116.06
(Cq), 118.9, 124.77, 125.40, 126.37, 127.35, 127.67, 128.08, 128.82,
129.10, 129.35 (CH) 132.58, 134.99, 136.67, 136.78 (Cq), 138.26
(CH), 138.43 (Cq), 139.27 (CH), 146.77 (Cq), 190.50 (CO) ppm.
Experimental Section
General: The starting merocyanines were synthesized as re-
ported.[10] All other reagents are commercially available and were
used without further purification. Thin-layer chromatography
(TLC) of the reaction mixtures and determination of the Rf values
of the products were performed on aluminum sheets precoated with
silica gel 60 F254 (Merck). Melting points were determined with a
Kofler apparatus and are uncorrected. NMR spectra were recorded
at ambient temperature (300 K) in CDCl3 solutions with a Bruker
Avance DRX-250 spectrometer, operating at 250.13 and
1
62.90 MHz for H and 13C nuclei or with an Avance 600 II+ spec-
3-[2-(4-Chlorophenylthio)-3-(piperidin-1-ylmethylene)cyclopent-1-
enyl]-1-(naphthalen-2-yl)prop-2-en-1-one (1b): Starting from mero-
cyanine MC1 (365 mg, 1 mmol) and 4-chlorobenzenethiol (723 mg,
5 mmol), the general procedure afforded a spectroscopically pure
mixture of 1b/2b (91:9) as a dark-red solid. Yield: 442 mg (91%).
Rf = 0.55 (diethyl ether/hexane, 1:1). MS (EI, 70 eV): m/z = 485
[M]+. 1H NMR (CDCl3): δ = 1.59 (br., 6 H, 3 CH2pip), 2.9–3.06
(m, 4 H, 2 CH2c-pent), 3.28 (m, 4 H, 2 CH2pip), 6.61 (s, 1 H, 7-H),
1
trometer, operating at 600.13 and 150.92 MHz for H and 13C nu-
clei, respectively, with TMS as internal standard for chemical shifts.
Mass spectra (MS) were recorded with Hewlett–Packard 5973A,
Perkin–Elmer Sciex (API 365) or Applied Biosystems (Q TRAP)
spectrometers. Elemental analysis were performed by the Micro-
analytical service Laboratory of the Institute of Organic Chemistry,
Bulgarian Academy of Sciences. Absorption spectra were scanned
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6.88 (d, J = 15 Hz, 1 H, 2-H), 7.11–7.25 (m, 4 H, Harom), 7.52– (br., 6 H, 3 CH2pip), 2.9–3.05 (m, 4 H, 2 CH2c-pent), 3.29 (br., 4 H,
7.63 (m, 2 H, Harom), 7.88–8.05 (m, 4 H, Harom), 8.2 (d, J = 15 Hz, 2 CH2pip), 3.99 (s, 3 H, CH3), 6.65 (s, 1 H, 7-H), 6.93 (d, J = 15 Hz,
1 H, 3-H), 8.42 (s, 1 H, Harom) ppm. 13C NMR (CDCl3, DEPT): δ 1 H, 2-H), 7.53–7.58 (m, 2 H, Harom), 7.86–8.06 (m, 4 H, Harom),
= 24.22, 26.09 (CH2pip), 27.25, 30.51 (CH2c-pent), 51.63 (CH2pip),
115.70 (Cq), 119.13, 124.71, 126.42, 127.69, 127.77, 128.14, 128.49, (CDCl3, DEPT): δ = 24.17, 26.17 (CH2pip), 27.25, 30.58 (CH2c-pent),
128.93, 129.13 (CH), 129.27 (Cq), 129.36 (CH), 131.18, 132.58, 34.44 (CH3), 51.68 (CH2pip), 114.69 (Cq), 119.55, 124.56, 126.61,
135.03, 135.41, 136.59 (Cq), 138.09 (CH), 138.58 (Cq), 138.89 (CH), 127.78, 128.03, 128.34, 129.27, 129.43 (CH), 132.66, 135.25, 136.35
8.21 (d, J = 15 Hz, 1 H, 3-H), 8.45 (s, 1 H, Harom) ppm. 13C NMR
145.99 (Cq), 190.41 (CO) ppm.
(Cq), 137.07 (CH), 138.22 (Cq), 138.60 (CH), 139.45, 151.04 (Cq),
189.78 (CO) ppm.
3-[2-(Benzothiazol-2-ylthio)-3-(piperidin-1-ylmethylene)cyclopent-1-
enyl]-1-(naphthalen-2-yl)prop-2-en-1-one (1d): Reaction between
MC1 (365 mg, 1 mmol) and benzothiazole-2-thiol (835 mg,
5 mmol) afforded a pure mixture of 1d/2d (80:20) as a dark-red
solid. Yield: 483 mg (95%). Rf = 0.86 (dichloromethane/MeOH,
19:1). MS (EI, 70 eV): m/z = 508 [M]+. 1HNMR (CDCl3): δ = 1.59
(br., 6 H, 3 CH2pip), 2.98–3.15 (m, 4 H, 2 CH2c-pent), 3.32 (br., 4
H, 2 CH2pip), 6.79 (s, 1 H, 7-H), 6.94 (d, J = 15 Hz, 1 H, 2-H),
7.27–7.32 (m, 1 H, Harom), 7.4–7.6 (m, 3 H, Harom), 7.7 (d, J =
8.7 Hz, 1 H, Harom), 7.82–7.92 (m, 4 H, Harom), 8.02 (d, J = 8.7 Hz,
3-{2-(4-Bromophenylthio)-3-[(diethylamino)methylene]cyclopent-1-
enyl}-1-(naphthalen-2-yl)prop-2-en-1-one (2c): Starting from mero-
cyanine MC1 (365 mg, 1 mmol) and 4-bromobenzenethiol (189 mg,
1 mmol), the general procedure afforded spectroscopically and ana-
lytically pure 2c as a dark-red viscous oil. Yield: 414 mg (80%).
Rf = 0.86 (dichloromethane/MeOH, 19:1). C29H28BrNOS (518.51):
calcd. C 67.18, H 6.30, N 2.70, S 6.18; found C 67.23, H 6.07, N
1
2.63, S 6.11. MS (EI, 9 eV): m/z = 519 [M]+. H NMR (CDCl3): δ
= 1.07 (t, J = 7 Hz, 6 H, 2 CH3), 2.88–3.02 (m, 4 H, 2 CH2c-pent),
3.19 (q, J = 7 Hz, 4 H, 2 CH2CH3), 6.6 (s, 1 H, 7-H), 6.84 (d, J =
15 Hz, 1 H, 2-H), 7.03–7.09 (m, 2 H, Harom), 7.29–7.36 (m, 2 H,
1 H, Harom), 8.20 (d, J = 15 Hz, 1 H, 3-H), 8.42 (s, 1 H, Harom
)
ppm. 13C NMR (CDCl3, DEPT): δ = 24.23, 26.20 (CH2pip), 27.43,
30.63 (CH2c-pent), 51.66 (CH2pip), 115.27 (Cq), 120.31, 120.80,
121.78, 124.24, 124.73, 126.07, 126.49, 127.73, 127.88, 128.23,
129.36 (CH), 132.58, 135.14, 135.72, 136.38 (Cq), 137.61, 138.17
(CH), 139.33, 142.71, 153.89 (Cq), 190.48 (CO) ppm.
Harom), 7.49–7.59 (m, 2 H, Harom), 7.83–8.04 (m, 4 H, Harom), 8.19
(d, J = 15 Hz, 1 H, 3-H), 8.39 (s, 1 H, Harom) ppm. 13C NMR
(CDCl3, DEPT): δ = 14.84 (2 CH3), 26.81, 30.49 (CH2c-pent), 46.69
(2 CH3CH2), 114.34 (Cq), 118.70 (CH), 119.03 (Cq), 124.80, 126.45,
127.74, 128.16, 128.88, 129.13, 129.40, 131.82, 132.24 (CH), 132.64,
135.06, 136.23, 136.75 (Cq), 137.26 (CH), 137.97 (Cq), 139.02 (CH),
146.24 (Cq) 190.47 (CO) ppm.
(E)-1-(Naphthalen-2-yl)-3-[(Z)-3-(piperidin-1-ylmethylene)-2-(pyr-
imidin-2-ylthio)cyclopent-1-enyl]prop-2-en-1-one (1e): Reaction be-
tween MC1 (365 mg, 1 mmol) and pyrimidine-2-thiol (560 mg,
5 mmol) afforded a pure mixture of 1e/2e (90:10) as a dark-red
solid. Yield: 381 mg (84%). Rf = 0.35 (dichloromethane/methanol,
100:2). MS (EI, 9 eV): m/z = 453 [M]+. 1H NMR (CDCl3): δ = 1.59
(br., 6 H, 3 CH2pip), 2.95–3.13 (m, 4 H, 2 CH2c-pent), 3.29 (br., 4
H, 2 CH2pip), 6.66 (s, 1 H, 7-H), 6.9 (d, J = 15 Hz, 1 H, 2-H), 6.98
(t, J = 5 Hz, 1 H, Hpyrim), 7.5–7.61 (m, 2 H, Harom), 7.87–8.05 (m,
4 H, Harom), 8.16 (d, J = 15 Hz, 1 H, 3-H), 8.44 (s, 1 H, Harom),
8.50 (d, J = 5 Hz, 2 H, Hpyrim) ppm. 13C NMR (CDCl3, DEPT): δ
= 24.28, 26.14 (CH2pip), 27.45, 30.68 (CH2c-pent), 51.59 (CH2pip),
116.93 (Cq), 117.07, 118.96, 124.72, 126.44, 127.73, 127.77, 128.12,
129.11, 129.38 (CH) 132.65, 135.07, 136.72 (Cq), 137.37 (CH),
138.98 (Cq), 139.02 (CH), 143.22 (Cq), 157.66 (CH), 171.69 (Cq),
190.16 (CO) ppm.
(E)-3-{(E)-2-(Benzo[d]thiazol-2-ylthio)-3-[(diethylamino)methylene]-
cyclopent-1-enyl}-1-(naphthalen-2-yl)prop-2-en-1-one (2d): Starting
from merocyanine MC1 (365 mg, 1 mmol) and benzothiazole-2-
thiol (836 mg, 5 mmol), the general procedure afforded pure 2d as
a dark-red solid. Yield: 437 mg (88%). Rf = 0.24 (diethyl ether/
hexane, 1:1). M.p. 154–156 °C. C30H28N2OS2 (496.69): calcd. C
72.55, H 5.68, N 5.64, S 12.91; found C 72.71, H 5.95, N 5.49, S
1
12.80. MS (EI, 9 eV): m/z = 496 [M]+. HNMR (CDCl3): δ = 1.12
(t, J = 7.1 Hz, 6 H, 2 CH3CH2), 2.97–3.1 (m, 4 H, 2 CH2c-pent),
3.24 (q, J = 7.1 Hz, 4 H, 2 CH3CH2), 6.84 (s, 1 H, 7-H), 6.89 (d,
J = 15 Hz, 1 H, 2-H), 7.24–7.30 (m, 1 H, Harom), 7.36–7.58 (m, 3
H, Harom), 7.80–7.97 (m, 4 H, Harom), 7.98–8.01 (m, 1 H, Harom),
8.18 (d, J = 15 Hz, 1 H, 3-H), 8.39 (s, 1 H, Harom) ppm. 13C NMR
(CDCl3, DEPT): δ = 14.95 (CH3CH2), 26.92, 30.54 (CH2c-pent),
46.73 (CH3CH2), 114.34 (Cq), 119.80, 120.81, 121.77, 124.26,
124.75, 126.07, 126.50, 127.74, 127.86, 128.22, 129.32, 129.36 (CH),
132.59, 135.12, 135.74, 136.47 (Cq), 136.92, 138.28 (CH), 138.59,
143.00, 153.82 (Cq), 190.46 (CO) ppm.
2-[(5-Methyl-1,3,4-thiadiazol-2-ylthio)-3-(piperidin-1-ylmethylene)cy-
clopent-1-enyl]-1-(naphthalen-2-yl)prop-2-en-1-one (1f): Reaction of
MC1 (365 mg, 1 mmol) with 5-methyl-1,3,4-thiadiazole-2-thiol
(660 mg, 5 mmol) gave a pure mixture of 1f/2f (86:14) as a dark-red
solid. Yield: 464 mg (97%). Rf = 0.36 (dichloromethane/methanol,
(E)-3-{(Z)-3-[(Diethylamino)methylene]-2-(pyrimidin-2-ylthio)cyclo-
pent-1-enyl}-1-(naphthalen-2-yl)prop-2-en-1-one (2e): Reaction be-
tween merocyanine MC1 (365 mg, 1 mmol) and pyrimidine-2-thiol
(560 mg, 5 mmol) afforded pure 2e as a dark-red solid. Yield:
335 mg (76%). Rf = 0.23 (dichloromethane/methanol, 100:2). M.p.
168–170 °C. C27H27N3OS (441.59): calcd. C 73.44, H 6.16, N 9.52,
S 7.26; found C 73.29, H 6.02, N 9.29, S 7.03. MS (EI, 70 eV): m/z
= 441 [M]+. 1HNMR (CDCl3): δ = 1.1 (t, J = 7.1 Hz, 6 H, 2
CH3CH2), 2.88–3.02 (m, 4 H, 2 CH2c-pent), 3.20 (q, J = 7.1 Hz, 4
H, 2 CH3CH2), 6.69 (s, 1 H, 7-H), 6.86 (d, J = 14.9 Hz, 1 H, 2-H),
6.95 (t, J = 4.8 Hz, 1 H, Hpyrim), 7.48–7.58 (m, 2 H, Harom), 7.48–
8.02 (m, 4 H, Harom), 8.15 (d, J = 14.9 Hz, 1 H, 3-H), 8.41 (s, 1 H,
Harom), 8.48 (d, J = 4.8 Hz, 2 H, CHpyrim) ppm. 13C NMR (CDCl3,
DEPT): δ = 14.79 (CH3CH2), 26.89, 30.52 (CH2c-pent), 46.53
(CH3CH2), 115.78 (Cq), 116.97, 118.47 (CH), 124.71, 126.36,
127.66, 128.03, 128.99, 129.32 (CH), 132.61, 135.00 (Cq), 136.47
1
19:1). MS (EI, 9 eV): m/z = 473 [M]+. HNMR (CDCl3): δ = 1.59
(br., 6 H, 3 CH2pip), 2.65 (s, 3 H, CH3), 2.90–3.10 (m, 4 H, 2
CH2c-pent), 3.31 (br., 4 H, 2 CH2pip), 6.72 (s, 1 H, 7-H), 6.92 (d, J
= 15 Hz, 1 H, 2-H), 7.52–7.58 (m, 2 H, Harom), 7.85–8.05 (m, 4 H,
Harom), 8.1 (d, J = 15 Hz, 1 H, 3-H), 8.21 (s, 1 H, Harom) ppm. 13C
NMR (CDCl3, DEPT): δ = 15.75 (CH3), 24.22, 26.23 (CH2pip),
27.32, 30.54 (CH2c-pent), 51.69 (CH2pip), 114.75 (Cq), 119.92,
124.65, 126.58, 127.78, 127.98, 128.29, 129.30, 129.42 (CH), 135.21,
136.38 (Cq), 137.69, 137.90 (CH), 138.42, 143.70, 166.01, 167.13
(Cq), 190.02 (CO) ppm.
(E)-3-[(E)-2-(1-Methyl-1H-tetrazol-5-ylthio)-3-(piperidin-1-ylmeth-
ylene)cyclopent-1-enyl]-1-(naphthalen-2-yl)prop-2-en-1-one (1g):
Starting from merocyanine MC1 (365 mg, 1 mmol) and 1-methyl-
1H-tetrazole-5-thiol (348 mg, 3 mmol), the general procedure af-
forded a spectroscopically pure mixture of 1g/2g (80:20) as a dark-
red solid. Yield: 370 mg (81%). Rf = 0.6 (dichloromethane/MeOH, (CH), 136.79, 138.18 (Cq), 139.07 (CH), 143.53 (Cq), 157.55, 157.85
1
30:1). MS (EI, 9 eV): m/z = 457 [M]+. H NMR (CDCl3): δ = 1.58
(CH), 171.70 (Cq), 190.14 (CO) ppm.
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Synthetic Potentials of Heptamethine Merocyanine Dyes
(E)-3-{(E)-3-[(Diethylamino)methylene]-2-(5-methyl-1,3,4-thiadi- 13.80, S 6.32; found C 70.73, H 5.59, N 13.72, S 6.09. MS (EI,
azol-2-ylthio)cyclopent-1-enyl}-1-(naphthalen-2-yl)prop-2-en-1-one
(2f): Reaction of merocyanine MC1 (365 mg, 1 mmol) with 5-
9 eV): m/z = 507 [M]+. 1H NMR (CDCl3) δ = 1.62 (br., 6 H, 3
CH2pip), 2.90–3.05 (m, 4 H, 2 CH2c-pent), 3.33 (br., 4 H, 2 CH2pip),
methyl-1,3,4-thiadiazole-2-thiol (396 mg, 3 mmol) afforded 2f as a 4.03 (s, 3 H, CH3), 6.69 (s, 1 H, 7-H), 6.98 (d, J = 15 Hz, 1 H, 2-
dark-red solid. Yield: 410 mg (89%). Rf = 0.45 (dichloromethane/
methanol, 19:1). M.p. 76–77 °C. C26H27N3OS2 (461.64): calcd. C
67.65, H 5.90, N 9.10, S 13.89; found C 67.38, H 5.73, N 9.00, S
H), 7.65–7.80 (m, 2 H, Harom), 7.84–7.89 (m, 2 H, Harom), 7.93–
7.97 (m, 1 H, Harom), 8.22–8.30 (m, 2 H, Harom, 3-H), 8.51- 8.52
(m, 1 H, Harom), 8.73–8.80 (m, 2 H, Harom) ppm. 13C NMR
13.71. MS (EI, 9 eV): m/z = 461 [M] +. 1H NMR (CDCl3): δ = 1.12 (CDCl3, DEPT): δ = 24.17, 26.19 (3CH2pip), 27.27, 30.57 (CH2c-
(t, J = 7.1 Hz, 6 H, 2 CH3CH2), 2.64 (s, 3 H, CH3), 2.88–3.00 (m, pent), 34.45 (CH3), 51.69 (CH2pip), 114.73 (Cq), 119.46, 123.06,
4 H, 2 CH2c-pent), 3.24 (q, J = 7.1 Hz, 4 H, 2 CH3CH2), 6.78 (s, 1
H, 7-H), 6.9 (d, J = 14.9 Hz, 1 H, 2-H), 7.52–7.57 (m, 2 H, Harom),
125.60, 126.95, 127.41, 127.57, 127.73, 128.69, 129.25 (CH), 131.55,
132.89, 136.84 (Cq), 137.14 (CH), 138.21 (Cq), 138.66 (CH), 139.43,
7.85–8.05 (m, 4 H, Harom), 8.19 (d, J = 14.9 Hz, 1 H, 3-H), 8.44 (s, 139.58 (Cq), 189.52 (CO) ppm.
1 H, Harom) ppm 13C NMR (CDCl3, DEPT): δ = 14.95 (2
General Experimental Procedure for the Conversion of Ramified
CH3CH2), 15.74 (CH3), 26.83 (CH2c-pent), 30.46 (CH2c-pent), 46.74
(2 CH3CH2), 113.82 (Cq), 119.15, 124.68, 126.55, 127.77, 127.94,
128.27, 129.24, 129.40 (CH), 132.65, 135.18, 136.48 (Cq), 137.13
(CH), 137.77 (Cq), 137.81 (CH), 143.95, 166.05, 167.12 (Cq), 190.04
(CO) ppm.
Heptamethine Merocyanines into Nonamethine Merocyanines Dyes:
A solution of the corresponding ramified merocyanine 2 (1 mmol)
and benzazolium salt (1 or 2 mmol) in dry pyridine (10 mL) was
kept under reflux for the time indicated in Table 2. The mixture
was allowed to cool to room temperature and then poured onto
cold water. The separated fine crystals were collected by filtration.
(E)-3-{(E)-3-[(Diethylamino)methylene]-2-(1-methyl-1H-tetrazol-5-
ylthio)cyclopent-1-enyl}-1-(naphthalen-2-yl)prop-2-en-1-one (2g): Pure compounds 4a–4g were obtained after column chromatog-
Reaction of merocyanine MC1 (365 mg, 1 mmol) with 1-methyl-
tetrazole-5-thiol (348 mg, 3 mmol) gave pure 2g as a dark-red gum.
Yield: 320 mg (72%). Rf = 0.28 (dichloromethane/methanol, 100:2).
C25H27N5OS (445.58): calcd. 67.39, H 6.11, N 15.72, S 7.20; found
C 67.12, H 5.93, N 15.49, S 7.03. MS (EI, 9 eV): m/z = 445 [M]+.
1HNMR (CDCl3) δ = 1.16 (t, J = 7.1 Hz, 6 H, 2 CH3CH2), 2.8–
3.05 (m, 4 H, 2 CH2c-pent), 3.26 (q, J = 7.1 Hz, 4 H, 2 CH3CH2),
4.02 (s, 3 H, CH3), 6.76 (s, 1 H, 7-H), 6.96 (d, J = 14.8 Hz, 1 H,
2-H), 7.55–7.64 (m, 2 H, Harom), 7.92–8.10 (m, 4 H, Harom), 8.28
(d, J = 14.8 Hz, 1 H, 3-H), 8.49 (s, 1 H, Harom) ppm. 13C NMR
(CDCl3, DEPT): δ = 14.89 (2CH3CH2), 26.77, 30.49 (CH2c-pent),
34.50 (CH3), 46.74 (2CH3CH2), 113.73 (Cq), 119.12, 124.57,
126.61, 127.78, 128.02, 128.33, 129.23, 129.43 (CH), 132.65, 135.23,
136.42, (Cq), 137.17 (CH), 137.61 (Cq), 137.93 (CH), 139.78, 150.94
(Cq), 189.75 (CO) ppm.
raphy purification on silica gel.
(E)-3-{(E)-3-[(Z)-2-(3-Ethylbenzo[d]thiazol-2(3H)-ylidene)ethyl-
idene]-2-(pyrimidin-2-ylthio)cyclopent-1-enyl}-1-(naphthalen-2-yl)-
prop-2-en-1-one (4a): The general experimental procedure followed
by separation of the crude product, a mixture of 4a/5b (84:26),
by column chromatography (silica; CH2Cl2/CH3OH, 30:1) afforded
pure 4a as a dark-blue solid. Yield: 164 mg (30 %). M.p. 205–
208 °C. C33H27N3OS2 (545.16): calcd. C 72.63, H 4.99, N 7.70, S
11.75; found C 72.81, H 5.15, N 7.47, S 11.92. MS (ESI): m/z (%)
1
= 546.2 (25) [M + 1]+. H NMR (CDCl3): δ = 1.32 (t, J = 7.0 Hz,
3 H, CH3), 2.93–2.97 (m, 2 H, CH2c–pent), 3.05–3.09 (m, 2 H,
CH2c-pent), 3.84 (q, J = 7.0 Hz, 2 H, CH3CH2), 5.38 (d, J = 11.6 Hz,
1 H, 8-H), 6.57 (d, J = 11.6 Hz, 1 H, 7-H), 6.76 (d, J = 8.07 Hz, 1
H, CHarom), 6.92 (t, J = 7.6 Hz, 1 H, CHarom), 6.99 (t, J = 4.8 Hz,
1 H, CHarom), 7.09 (d, J = 15.1 Hz, 1 H, 2-H), 7.17 (t, J = 7.8 Hz,
1 H, CHarom), 7.25 (d, J = 7.6 Hz, 1 H, CHarom), 7.56 (t, J = 7.6 Hz,
7-{(E)-5-[(Diethylamino)methylene]-2-[(E)-3-(naphthalen-2-yl)-3-
oxoprop-1-enyl]cyclopent-1-enylthio}-4-methyl-2H-chromen-2-one 1 H, CHarom), 7.60 (t, J = 7.8 Hz, 1 H, CHarom), 7.90 (t, J = 8.5 Hz,
(2h): Reaction of merocyanine MC1 (365 mg, 1 mmol) and 7-mer-
capto-4-methyl-2H-chromen-2-one (192 mg, 1 mmol) produced
pure 2h as a dark-red solid. Yield: 495 mg (95%). Rf = 0.84 (dichlo-
romethane/methanol, 19:1). M.p. 125–128 °C. C33H31NO3S
(521.67): calcd. C 75.98, H 5.99, N 2.68, S 6.15; found C 75.73, H
5.77, N 2.48, S 6.00. MS (EI, 9 eV): m/z = 521 [M]+. 1HNMR
2 H, CHarom), 7.96 (d, J = 7.6 Hz, 1 H, CHarom), 8.05 (d, J =
7.3 Hz, 1 Harom), 8.17 (d, J = 15.1 Hz, 1 H, 3-H), 8.46 (s, 1 H,
CHarom), 8.53 (d, J = 4.8 Hz, 2 H, CHpyrim) ppm. 13C NMR
(CDCl3, DEPT): δ = 11.34 (CH3), 26.94 (CH2c-pent), 30.12
(CH2c-pent), 39.28 (CH2CH3), 90.20, 108.06, 117.13, 120.93, 121.46,
121.89, 122.42, 124.65, (CH), 124.84 (Cq), 126.22, 126.57, 127.78,
(CDCl3): δ = 1.1 (t, J = 7 Hz, 6 H, 2 CH2CH3), 2.38 (d, J = 1.2 Hz, 128.02, 128.30, 129.44, 129.47 (CH), 132.61, 135.23, 136.25 (Cq),
3 H, CH3), 2.95–3.1 (m, 4 H, 2 CH2c-pent), 3.21 (q, J = 7 Hz, 4 H, 138.38 (CH), 138.83, 140.57, 142.40, 146.72, 147.79 (Cq), 157.66
2 CH2CH3), 6.17 (d, J = 1.2 Hz, 1 H), 6.67 (s, 1 H, 7-H), 6.89 (d,
J = 15 Hz, 1 H, 2-H), 7.03 (d, J = 1.8 Hz, 1 H, CHcoum), 7.16 (d,
J = 1.8 Hz, 1 H, CHcoum), 7.42 (d, J = 8, 1H Hz, CHcoum), 7.51–
7.56 (m, 2 H, CHnapht), 7.84–7.93 (m, 4 H, CHnapht), 8.00 (dd, J =
8, 1.8 Hz, 1 H, CHcoum), 8.14 (d, J = 15 Hz, 1 H, 3-H), 8.41 (s, 1
H, CHnapht) ppm. 13C NMR (CDCl3, DEPT): δ = 14.83 (CH3CH2),
18.54 (CH3coum), 26.79, 30.47 (CH2c-pent), 46.61 (CH3CH2), 113.65,
113.87 (CH), 114.54, 117.15 (Cq), 118.93, 122.36, 124.54, 124.65,
126.42, 127.69, 127.79, 128.12, 129.11, 129.34 (CH), 132.61, 135.08,
136.62 (Cq), 136.79, 138.37 (CH), 138.47, 143.29, 144.14, 152.22,
153.91 (Cq), 160.69 (COcoum), 190.05 (COmerocyanine) ppm.
(CH),171.55 (Cq), 190.10 (CO) ppm. Compound 5a, isolated from
the same separation procedure (56 mg, 9 %), was previously de-
scribed.[10]
N,N-Dimethyl-3-{(Z)-2-[(E)-2-{3-[(E)-3-(naphthalen-2-yl)-3-oxo-
prop-1-enyl]-2-(pyrimidin-2-ylthio)cyclopent-2-enylidene}ethyl-
idene]benzo[d]thiazol-3(2H)-yl}propanamide (4b): Pure 4b was iso-
lated from the crude mixture of 4b/5b (63:37) by column
chromatography (silica; CH2Cl2/CH3OH, 40:1) as a dark-blue so-
lid. Yield: 197 mg (36 %). M.p. 175–178 °C. C36H32N4O2S2
(616.20): calcd. C 70.10, H 5.23, N 9.08, S 10.40; found C 70.39,
H 5.01, N 9.32, S 10.23. MS (ESI): m/z (%) = 617.2 (100) [M +
1]+. 1H NMR (600 MHz, CDCl3): δ = 2.71 (t, J = 7.2 Hz, 2 H,
CH2CO), 2.94–2.96 (m, 2 H, CH2c-pent), 2.97 [s, 3 H, CON(CH3)2],
2.98 [s, 3 H, CON(CH3)2], 3.05–3.08 (m, 2 H, CH2c-pent), 4.17 (t, J
= 7.6 Hz, 2 H, NCH2), 5.41 (d, J = 11.6 Hz, 1 H, 8-H), 6.54 (d, J
= 11.6 Hz, 1 H, 7-H), 6.84 (d, J = 7.9 Hz, 1 H, CHarom), 6.91 (dt,
J = 7.6, 0.9 Hz, 1 H, CHarom), 6.99 (t, J = 4.8 Hz, 1 H, CHarom),
(E)-3-[(E)-2-(1-Methyl-1H-tetrazol-5-ylthio)-3-(piperidin-1-ylmeth-
ylene)cyclopent-1-enyl]-1-(phenanthren-3-yl)prop-2-en-1-one (3): Re-
action of merocyanine MC2 (428 mg, 1 mmol) and 1-methyl-1H-
tetrazole-5-thiol (580 mg, 5 mmol) gave pure 3 as a dark-red solid.
Yield: 320 mg (63%). Rf = 0.28 (dichloromethane/methanol, 100:2).
M.p. 178–180 °C. C30H29N5OS (507.65): calcd. C 70.98, H 5.76, N
Eur. J. Org. Chem. 2009, 5063–5071
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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FULL PAPER
7.11 (d, J = 15.1 Hz, 1 H, 2-H), 7.16 (t, J = 8.2 Hz, 1 H, CHarom),
7.24 (dd, J = 7.6, 0.9 Hz, 1 H, CHarom), 7.54–7.62 (m, 2 H,
CHarom), 7.89 (d, J = 7.3 Hz, 1 H, CHarom), 7.90 (d, J = 8.5 Hz, 1
H, CHarom), 7.97, (d, J = 7.9 Hz, 1 H, CHarom), 8.04 (dd, J = 8.5,
1.8 Hz, 1 H, CHarom), 8.15 (d, J = 15.1 Hz, 1 H, 3-H), 8.46 (s, 1
H, CHarom), 8.53 (d, J = 4.8 Hz, 2 H, CHpyrim) ppm. 13C NMR
(CDCl3, DEPT): δ = 27.03 (CH2c-pent), 29.36 (CH2CO), 30.17
(CH2c-pent), 35.43, 37.18 [CON(CH3)2], 40.58 (NCH2), 90.49,
108.39, 117.15, 121.18, 121.47, 122.00, 122.20, 124.60 (CH), 124.62
(Cq), 126.35, 126.60, 127.79, 128.08, 128.33, 129.48 (CH), 132.60,
135.26, 136.18 (Cq), 138.30 (CH), 139.41, 140.35, 142.33, 147.20,
147.43 (Cq), 157.66 (CH),170.29 (Cq), 171.50, 190.10 (CO) ppm.
126.63, 127.78, 128.12, 128.37, 129.47, 129.50 (CH), 132.60, 135.15,
137.45 (Cq), 137.66 (CH), 141.59, 142.32, 142.79, 146.87, 148.66,
152.34, 153.85, 160.82 (Cq), 190.00, 207.10 (CO) ppm.
N,N-Dimethyl-3-{(Z)-2-[(E)-2-{2-(4-methyl-2-oxo-2H-chromen-7-yl-
thio)-3-[(E)-3-(naphthalen-2-yl)-3-oxoprop-1-enyl]cyclopent-2-
enylidene}ethylidene]benzo[d]thiazol-3(2H)-yl}propanamide (4d):
Pure 4d was obtained after purification of the crude mixture by
column chromatography (silica; CH2Cl2/CH3OH, 20:1). Yield:
383 mg (55%). M.p. 157–160 °C. C42H36N2O4S2 (696.21): calcd. C
72.39, H 5.21, N 4.02, S 9.20; found C 72.61, H 5.45, N 4.37, S
9.68. MS (ESI): m/z (%) = 697.3 (100) [M + 1]+. 1H NMR
(600 MHz, CDCl3): δ = 2.39 (s, 3 H, CH3coum), 2.71 (t, J = 7.5 Hz,
2 H, CH2CO), 2.88–2.95 (m, 2 H, CH2c-pent), 2.96 [s, 3 H,
CON(CH3)2], 2.98 [s, 3 H, CON(CH3)2], 3.04–3.09 (m, 2 H,
CH2c-pent), 4.17 (t, J = 7.5 Hz, 2 H, NCH2), 5.37 (d, J = 11.5 Hz,
1 H, 8-H), 6.19 (s, 1 H, CHcoum), 6.51 (d, J = 11.5 Hz, 1 H, 7-H),
6.85 (d, J = 11.5 Hz, 1 H, CHarom), 6.92 (t, J = 7.5 Hz, 1 H,
CHarom), 7.08–7.19 (m, 3 H, C Harom, 2-H), 7.23 (d, J = 7.3 Hz, 2
H, CHarom), 7.47 (d, J = 8.5 Hz, 1 H, CHarom), 7.54–7.63 (m, 2 H,
CHarom), 7.90 (t, J = 9.7 Hz, 2 H, CHarom), 7.97 (d, J = 7.9 Hz, 1
H), 8.05 (d, J = 9.1 Hz, 1 H, CHarom), 8.17 (d, J = 15.1 Hz, 1 H,
3-H), 8.47 (s, 1 H, CHarom) ppm. 13C NMR (CDCl3, DEPT): δ =
18.67 (CH3coum), 26.89 (CH2c-pent), 29.37 (CH2CO), 30.10
(CH2c-pent), 35.44, 37.21 [CON(CH3)2], 40.59 (NCH2), 90.23,
108.55, 113.76, 114.53 (CH), 117.41 (Cq), 121.36, 121.47, 122.49,
122.94, 122.97 (CH), 124.47 (Cq), 124.55, 124.67, 126.44, 126.65,
127.78, 128.16, 128.40, 129.49, 129.55 (CH), 132.59, 135.31, 136.06
(Cq), 137.55 (CH), 138.03, 141.36, 142.24, 142.78, 147.39, 148.27,
152.38, 153.85 (Cq), 160.81, 170.19, 189.95 (CO) ppm.
3-{(Z)-2-[(E)-2-{2-(2-{N-[3-(Dimethylamino)-3-oxopropyl]acet-
amido}phenylthio)-3-[(E)-3-(naphthalen-2-yl)-3-oxoprop-1-enyl]cyclo-
pent-2-enylidene}ethylidene]benzo[d]thiazol-3(2H)-yl}-N,N-dimethyl-
propanamide (5b): The above described experiment gave access to
pure 5b as a dark-blue solid. Yield: 123 mg (16 %). M.p. 193–
196 °C. C45H46N4O4S2 (770.30): calcd. C 70.10, H 6.01, N 7.27, S
8.32; found C 70.36, H 5.87, N 7.11, S 8.49. MS (ESI): m/z (%) =
771 (100) [M + 1]+. 1H NMR (600 MHz (CDCl3): δ = 1.98 (s, 3 H,
COCH3), 2.69 (t, J = 7.5 Hz, 2 H, CH2CO), 2.79–2.86 (m, 1 H,
CH2CO), 2.90–2.93 (m, 3 H, CH2c-pent, 1 H, CH2CO), 2.93 [s, 3 H,
CON(CH3)2], 2.94 [s, 3 H, CON(CH3)2], 2.97 [s, 3 H, CON-
(CH3)2], 3.05–3.08 (m, 2 H, CH2c-pent), 3.11 [s, 3 H, CON(CH3)2],
3.88–3.93 (m, 1 H, NCH2), 4.15 (t, J = 7.5 Hz, 2 H, NCH2), 4.25–
4.30 (m, 1 H, NCH2), 5.35 (d, J = 11.7 Hz, 1 H, 8-H), 6.47 (d, J
= 11.7 Hz, 1 H, 7-H), 6.82 (d, J = 8.1 Hz, 1 H, CHarom), 6.92 (dt,
J = 7.6, 0.9 Hz, 1 H, CHarom), 7.00 (dd, J = 7.2, 1.9 Hz, 1 H,
CHarom), 7.10 (d, J = 15.1 Hz, 1 H, H-2), 7.14–7.23 (m, 4 H,
CHarom), 7.33 (dd, J = 7.8, 1.0 Hz, 1 H, CHarom), 7.54 (dt, J = 8.1,
1.2 Hz, 1 H, CHarom), 7.59 (dt, J = 6.7, 1.2 Hz, 1 H, CHarom), 7.88
(t, J = 8.9 Hz, 2 H, CHarom) 7.92 (d, J = 8.1 Hz, 1 H, CHarom),
8.01 (dd, J = 8.5, 1.8 Hz, 1 H, CHarom), 8.08 (d, J = 15.1 Hz, 1 H,
H-3), 8.43 (s, 1 H, CHarom). 13C NMR (CDCl3, DEPT): δ = 22.62
(CH3CO), 26.89 (CH2c-pent), 29.39 (CH2CO), 30.18 (CH2c-pent),
32.31 (CH2CO), 35.31, 35.43, 37.18, 37.49 [2ϫCON(CH3)2], 40.60,
45.50 (2ϫNCH2), 89.92, 108.43, 121.43, 121.81, 122.49, 122.80,
124.55, 126.25, 126.38, 126.65, 127.15, 127.78, 128.14, 128.39,
128.98 (CH), 129.40 (Cq), 129.45, 129.51 (CH), 132.54, 135.25,
136.01, 136.52 (Cq), 137.72 (CH), 137.95, 139.55, 140.95, 142.19,
147.80, 148.60 (Cq), 170.21, 170.80, 171.24, 190.10 (CO) ppm.
(E)-3-{(E)-3-[(E)-2-(1-Ethyl-3,3-dimethylindolin-2-ylidene)ethyl-
idene]-2-(pyrimidin-2-ylthio)cyclopent-1-enyl}-1-(naphthalen-2-yl)-
prop-2-en-1-one (4e): Pure 4e was obtained after purification of the
crude mixture by column chromatography (silica; CH2Cl2/CH3OH,
160:1). Yield: 301 mg (54 %). M.p. 108–110 °C. C36H33N3OS
(555.23): calcd. C 77.80, H 5.99, N 7.56, S 5.77; found C 77.53, H
1
5.68, N 7.87, S 5.58. MS (ESI): m/z (%) = 556.3 (28) [M + 1]+. H
NMR (600 MHz, CDCl3): δ = 1.24 (t, J = 7.0 Hz, 3 H, CH2CH3),
1.58 [s, 6 H, C(CH3)2], 2.93–2.97 (m, 2 H, CH2c-pent), 3.34–3.38 (m,
2 H, CH2c-pent), 3.66 (q, J = 7.0 Hz, 2 H, CH2CH3), 5.32 (d, J =
12.6 Hz, 1 H, 8-H), 6.59 (d, J = 7.8 Hz, 1 H), 6.83 (t, J = 7.3 Hz,
1 H, CHarom), 6.96 (t, J = 7.3 Hz, 1 H, CHarom), 7.04–7.09 (m, 2
H, CHarom), 7.10 (d, J = 15.1 Hz, 1 H, 2-H), 7.15 (dt, J = 7.6,
1.2 Hz, 1 H, CHarom), 7.53–7.57 (m, 1 H, CHarom), 7.57–7.61 (m,
1 H, CHarom), 7.87 (d, J = 8.1 Hz, 1 H, CHarom), 7.89 (d, J =
8.8 Hz, 1 H, CHarom), 7.96 (d, J = 7.4 Hz, 1 H, CHarom), 8.04 (dd,
J = 8.6, 1.6 Hz, 1 H, CHarom), 8.23 (d, J = 15.1 Hz, 1 H, 3-H),
8.46 (s, 1 H, CHarom), 8.51 (d, J = 4.8 Hz, 2 H, CHpyrim) ppm. 13C
NMR (CDCl3, DEPT): δ = 11.14 (CH2CH3), 26.19 (CH2c-pent),
27.96 (C(CH3)2), 30.17 (CH2c-pent), 36.86 (CH2CH3), 45.78 (Cq),
77.24, 94.03, 105.99, 117.05, 119.77, 121.59, 121.67, 122.20, 124.66,
126.61, 127.71, 127.81, 128.08, 128.36, 129.49 (CH), 132.63, 135.27,
136.24 (Cq), 138.29 (CH), 138.69, 139.19, 141.15, 144.05, 146.89,
156.86 (Cq), 157.68 (CH), 171.55 (Cq), 190.25 (CO) ppm.
7-{(E)-5-[(Z)-2-{3-Ethylbenzo[d]thiazol-2(3H)-ylidene}ethylidene]-2-
[(E)-3-(naphthalen-2-yl)-3-oxoprop-1-enyl]cyclopent-1-ethylthio}-4-
methyl-2H-chromen-2-one (4c): Following the general procedure,
purification of the crude product by column chromatography (sil-
ica; CH2Cl2/CH3OH, 50:1) afforded pure 4c as a dark-blue solid.
Yield: 225 mg (36 %). M.p. 172–175 °C. C39H31NO3S2 (625.17):
calcd. C 74.84, H 4.99, N 2.24, S 10.25; found C 74.53, H 5.11, N
2.18, S 10.40. MS (ESI): m/z (%) = 626.2 (100) [M + 1]+. 1H NMR
(600 MHz, CDCl3): δ = 1.33 (t, J = 7.1 Hz, 3 H, CH3CH2), 2.43
(d, J = 1.0 Hz, 3 H, CH3coum), 2.91–2.96 (m, 2 H, CH2c-pent), 3.05–
3.09 (m, 2 H, CH2c-pent), 3.84 (q, J = 7.1 Hz, 2 H, CH3CH2), 5.34
(d, J = 11.7 Hz, 1 H, 8-H), 6.19 (d, J = 1.0 Hz, 1 H CHcoum), 6.55
(d, J = 11.7 Hz, 1 H, 7-H), 6.77 (d, J = 8.0 Hz, 1 H, CHarom), 6.92
(t, J = 7.1 Hz, 1 H, CHarom), 7.11–7.19 (m, 3 H, CHarom, 2-H), (E)-3-{(E)-3-[(E)-2-(1-Ethyl-3,3-dimethylindolin-2-ylidene)ethyl-
7.22–7.25 (m, 2 H, CHarom), 7.47 (d, J = 8.5 Hz, 1 H, CHarom), idene]-2-(1-methyl-1H-tetrazol-5-ylthio)cyclopent-1-enyl}-1-(naph-
7.55–7.61 (m, 2 H, CHarom), 7.90 (t, J = 11.7 Hz, 2 H, CHarom),
7.96 (d, J = 7.9 Hz, 1 H, CHarom), 8.05 (dd, J = 8.6, 1.7 Hz, 1 H,
thalen-2-yl)prop-2-en1-one (4f): Pure 4f was isolated after purifica-
tion of the crude mixture by column chromatography (silica;
CH2Cl2/CH3OH, 70:1). Yield: 357 mg (64 %). M.p. 92–95 °C.
CHarom), 8.18 (d, J = 15.1 Hz, 1 H, 3-H), 8.47 (s, 1 H, CHarom
)
ppm. 13C NMR (CDCl3, DEPT): δ = 11.38 (CH3CH2), 18.66 C34H33N5OS (559.24): calcd. C 72.96, H 5.94, N 12.51, S 5.73;
(CH3cum), 26.82 (CH2c-pent), 30.05 (CH2c-pent), 39.36 (CH2CH3), found C 72.56, H 5.71, N 12.78, S 5.97. MS (ESI): m/z (%) = 560.2
89.95, 108.23, 113.78, 114.59 (CH), 117.42 (Cq), 121.14, 121.48, (100) [M + 1]+. 1H NMR (600 MHz, CDCl3): δ = 1.23 (t, J =
122.23, 122.94, 123.39, 124.59, 124.67 (CH), 124.70 (Cq), 126.32, 7.2 Hz, 3 H, CH2CH3), 1.50 [s, 6 H, C(CH3)2], 2.86–2.90 (m, 2 H,
5070
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5063–5071

Synthetic Potentials of Heptamethine Merocyanine Dyes
CH2c-pent), 2.99–3.02 (m, 2 H, CH2c-pent), 3.67 (q, J = 7.2 Hz, 2 H,
CH2CH3), 4.01 (s, 3 H, CH3tetrazole), 5.23 (d, J = 12.4 Hz, 1 H, 8-
H), 6.64 (d, J = 7.8 Hz, 1 H), 6.89 (t, J = 7.3 Hz, 1 H, CHarom),
7.04 (d, J = 12.4 Hz, 1 H, 7-H), 7.13–7.20 (m, 3 H, CHarom), 7.55–
7.58 (m, 1 H, CHarom), 7.59–7.63 (m, 1 H, CHarom), 7.89 (d, J =
12.4 Hz, 1 H, CHarom), 7.93 (d, J = 8.7 Hz, 1 H, CHarom), 7.99 (d,
J = 7.9 Hz, 1 H, CHarom), 8.07 (dd, J = 8.5, 1.7 Hz, 1 H, CHarom),
8.26 (d, J = 15 Hz, 1 H, 3-H), 8.49 (s, 1 H, CHarom) ppm. 13C
NMR (CDCl3, DEPT): δ = 11.15 (CH2CH3), 26.20 (CH2c-pent),
28.06 [C(CH3)2], 29.97 (CH2c-pent), 34.49 (CH3tetrazole) 36.94
(CH2CH3), 46.16 (Cq), 93.78, 106.32, 120.36, 121.82, 122.87,
123.18, 124.49, 126.79, 127.74, 127.86, 128.34, 128.56, 129.53,
129.67 (CH), 132.61, 135.42, 135.87 (Cq), 136.42 (CH), 136.88,
137.05, 139.46, 143.74, 146.54, 150.76, 158.63 (Cq), 189.72 (CO)
ppm.
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[2] A. Ulman, Introduction to Ultrathin Organic Films, Academic
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481.
7-{(E)-5-[(E)-2-(1-Ethyl-3,3-dimethylindolin-2-ylidene)ethylidene]-2-
[(E)-3-(naphthalen-2-yl)-3-oxoprop-1-enyl]cyclopent-1-enylthio}-4-
methyl-2H-chromen-2-one (4g): Product 4g was isolated after purifi-
cation of the crude reaction mixture by column chromatography
(silica, CH2Cl2). Yield: 394 mg (62%). M.p. 123–126 °C.
C42H37NO3S (635.25): calcd. C 79.34, H 5.87, N 2.20, S 5.04; found
C 79.52, H 5.49, N 2.59, S 4.87. MS (ESI): m/z (%) = 636.3 (100)
[M + 1]+. 1H NMR (CDCl3): δ = 1.26 [t, J = 7.2 Hz, 6 H, C(CH3)
overlapped with CH2CH3], 1.63 [s, 3 H, C(CH3)], 2.36 (d, J =
1.0 Hz, 3 H, CH3coum), 2.93–2.98 (m, 2 H, CH2c-pent), 3.05–3.10 (m,
2 H, CH2c-pent), 3.67 (q, J = 7.2 Hz, 2 H, CH3CH2), 5.30 (d, J =
12.7 Hz, 1 H, 8-H), 6.19 (d, J = 1 Hz, 1 H, CHcoum), 6.63 (d, J =
7.7 Hz, 1 H, CHarom), 6.85 (t, J = 7.5 Hz, 1 H, CHarom), 7.00 (d, J
= 12.7 Hz, 1 H, 7-H), 7.07 (d, J = 6.8 Hz, 1 H, CHarom), 7.15–7.19
(m, 3 H, CHarom), 7.24 (dd, J = 8.4, 1.8 Hz, 1 H, CHarom), 7.48 (d,
J = 8.5 Hz, 1 H, CHarom), 7.55–7.60 (m, 1 H, CHarom), 7.60–7.65
(m, 1 H, CHarom), 7.91 (d, J = 8.0 Hz, 1 H, CHarom), 7.93 (d, J =
8.7 Hz, 1 H, CHarom), 8.00 (d, J = 7.0 Hz, 1 H, CHarom), 8.08 (dd,
J = 8.5, 1.6 Hz, 1 H), 8.25 (d, J = 15.1 Hz, 1 H, 3-H), 8.50 (s, 1 H,
CHarom) ppm. 13C NMR (CDCl3, DEPT): δ = 11.18 (CH3CH2),
18.62 (CH3cum), 26.09 (CH2c-pent), 27.80 [C(CH3)2], 30.11
(CH2c-pent), 36.91 (CH2CH3), 45.79 (Cq), 93.78, 106.16 (CH),
109.11 (Cq), 113.85, 114.77, 119.97, 121.64, 122.40, 122.75, 122.97,
124.59, 124.69, 126.67, 127.75, 127.82, 128.17, 128.42, 129.50,
129.56 (CH), 132.61, 135.33, 136.12, 136.70, 137.28 (Cq), 137.59
(CH), 139.13, 141.91, 142.57, 143.88, 147.25, 152.17 (Cq), 153.88,
190.07, (CO) ppm.
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Received: May 21, 2009
Published Online: August 28, 2009
Eur. J. Org. Chem. 2009, 5063–5071
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5071