Solvatochromism of mesoionic iodo(1,3-dithiol-2-ylium-4-yl)phenolates

Article abstract of DOI:10.1007/s00706-008-0944-y

Novel mesoionic phenolates were synthesized via 4-hydroxyaryl-1,3- dithiolium salts and characterized spectroscopically by UV-Vis. The bathochromic effect induced by iodine substituents was investigated for several solvents. A negative solvatochromism was recorded for the intramolecular charge transfer absorption band.

Full text of DOI:10.1007/s00706-008-0944-y

Monatsh Chem 139, 1433–1438 (2008)
DOI 10.1007/s00706-008-0944-y
Printed in The Netherlands
Solvatochromism of mesoionic iodo(1,3-dithiol-2-ylium-4-yl)phenolates
Lucian M. Birsa, Luliean V. Asaftei
Department of Organic Chemistry, Al.I. Cuza University of Iasi, Iasi, Romania
Received 23 March 2008; Accepted 26 March 2008; Published online 2 June 2008
# Springer-Verlag 2008
Abstract Novel mesoionic phenolates were synthe-
sized via 4-hydroxyaryl-1,3-dithiolium salts and
characterized spectroscopically by UV-Vis. The batho-
chromic effect induced by iodine substituents was
investigated for several solvents. A negative solvato-
chromism was recorded for the intramolecular charge
transfer absorption band.
nature of substituents, we decided to investigate the
influence of both acceptor and donor moieties on
the intramolecular charge transfer absorption band.
Several mesoionic phenolates with different second-
ary amines (dimethylamino, diethylamino, piperidine,
morpholine) at the 2-position of the 1,3-dithiol-2-
ylium ring were synthesized and investigated spec-
troscopically by UV-Vis. Since the position of intra-
molecular charge transfer absorption band was not
affected by the nature of secondary amine moiety
we decided to introduce iodine substituents on the
donor part of the mesoionic 2-(1,3-dithiol-2-ylium-
4-yl)phenolates. This paper deals with the synthesis
and UV-Vis behavior of new iodo substituted 2-(2-
dialkylamino-1,3-dithiol-2-ylium-4-yl)-phenolates.
Keywords Dithiocarbamates; Dithiolium salts; Mesoionic
compounds; Charge transfer.
Introduction
Solvatochromic dyes have played an important role
in the understanding of solvent polarity effects and
are increasingly important as probes of complex bi-
ological systems [1–3]. The systems where a donor
moiety is linked through a ꢀ- or ꢁ-bonded bridge to
the acceptor moiety received special interest [4]. A
variety of acceptor units have been investigated with
special attention paid to cationic systems, such as
pyridinium and bipyridinium cations [5–7].
In this context, investigations of a series of 2-[2-
(pyrrolidin-1-yl)-1,3-dithiol-2-ylium-4-yl]phenolates
have shown that 1,3-dithiolium cations can also
serve as acceptor moieties in intramolecular charge
transfer complexes [8]. The above mesoionic com-
pounds showed only a small negative solvatochro-
mism (ꢀÁl ¼ 10–15 nm). Therefore, by varying the
Results and discussion
Phenacyl N,N-dialkyldithiocarbamates 2a–2f have
been prepared by reaction of !-bromo-ketones
1a–1c with the corresponding N,N-dialkyldithiocar-
bamates (Scheme 1). 2-Bromo-1-(2-hydroxy-3-iodo-
5-methylphenyl)butan-1-one (1c) has been obtained
by bromination of 1-(2-hydroxy-3-iodo-5-methyl-
phenyl)butan-1-one [9] in glacial acetic acid as the
solvent.
As previously reported, attempts to cyclize N,N-
dialkyldithiocarbamates 2 using common cyclization
agents according to literature [10–12], led to deg-
radation of the substrates, often accompanied by
loss of molecular iodine. Using a P2O5 – CH3SO3H
(1:10) mixture as cyclization agent proved to be a
Correspondence: Lucian M. Birsa, Department of Organic
Chemistry, Al.I. Cuza University of Iasi, 700506 Iasi, Romania.
E-mail: lbirsa@uaic.ro

1434
L. M. Birsa, L. V. Asaftei
Scheme 1
Scheme 2
proper way to obtain 1,3-dithiolium salts 3 as pure
compounds and in high yields. Furthermore, we have
found that the cyclocondensation takes place in high
yields even at room temperature. Thus, a suspension
of 2 in three parts of the ‘‘superacid’’ mixture was
stirred at room temperature for 30 min to give a
solution, which contained the corresponding 1,3-
dithiolium cation. Addition of 70% perchloric acid
and methyl acetate to this solution give perchlorates
3a–3f as white crystalline products (Scheme 2).
Treatment of these perchlorates with a saturated
NaHCO3 solution gives the corresponding pheno-
lates 4a–4f as yellow crystalline products, which
show mesoionic character [13–15] (Scheme 1).
In a previous paper [8], the comparative study of
UV-Vis absorption spectra of 2-, 3-, and 4-[2-(pyr-
rolidin-1-yl)-1,3-dithiol-2-ylium-4-yl]phenolates has
shown that the yellow color of the above zwitterionic
compounds is due to a charge transfer between
electron-rich and electron-deficient regions of the
molecules and not to the contribution of quinoid
structures in the ground states (Scheme 2).
Investigations of UV-Vis absorption spectra of
mesoionic phenolates 4a–4f confirm the previous
findings. In comparison to the corresponding unsub-
stituted phenolates, the absorption spectra of 4a–4f
reveal a new absorption band at 255 nm. Our initial
assumptions placed the contribution of a quinoid
structure to 2-[2-(pyrrolidin-1-yl)-1,3-dithiol-2-ylium-
4-yl]phenolates around 235 nm, partially overlapped
ꢁ
by the ꢀ-ꢀ absorption band of aromatic ring. The
known bathochromic effect induced by iodine sub-
stituents confirms the above; the absorption band
placed at 255 nm clearly belongs to the contribution
of quinoid structures to the ground state of 4a–4f.
Usually, the intramolecular charge-transfer UV-
Vis absorption of such chromophores results from
a charge transfer from the HOMO of the donor part
to the LUMO of the acceptor part. For this reason,
the position of the charge-transfer band should de-
pend on solvent polarity [16–19], defined here as the
overall solvation ability of a solvent. In comparison
to the above studied unsubstituted (1,3-dithiol-2-
ylium-4-yl)phenolates, iodo substituted phenolates

Solvatochromism of mesoionic iodo(1,3-dithiol-2-ylium-4-yl)phenolates
1435
4a–4f should have a HOMO orbital of lower energy
and therefore a larger solvatochromism.
atom of the 1,3-dithiol-2-ylium ring. On going from
mesoionic compound 4a to 4d and 4e, the electronic
density at C-5 changes significantly, with the ex-
perimentally observed hypsochromic charge-transfer
band shift with increasing solvent polarity as a
consequence.
From the common solvents of the ET(30) solvent
polarity scale [20–24], methanol was found as the
highest polarity solvent, which ensures a sufficient
concentration for UV-Vis measurements. In this
solvent, a bathochromic effect was also recorded for
the intramolecular charge transfer absorption band,
390 nm vs 375 nm, in unsubstituted mesoionic phe-
nolates. In acetonitrile, a solvent of intermediate
polarity, the UV-Vis spectra of phenolates 4 display
a pronounced bathochromic shift of the charge-trans-
fer band. The highest shift was recorded in THF, a
low-polarity solvent. Thus, with increasing solvent
polarity, a hypsochromic band shift of Ál ¼ ꢀ44 to
ꢀ54 nm for representative phenolates 4a, 4d, and 4e
is observed, corresponding to a negative solvato-
chromism (Fig. 1, Table 1).
The intramolecular nature of charge-transfer band
of mesoionic phenolates 4 was proved by measure-
ments at different concentrations. Although an im-
portant hypsochromic shift of the charge-transfer
absorption band is induced by the iodine substituents
on the donor part, better results may be achieved in
systems with an extended positive charge delocaliza-
tion. By replacing the secondary amine substituent
with an appropriate one (e.g. aromatic units) the en-
ergy of LUMO orbital should increase do to the ex-
tended delocalization of positive charge. Therefore
a larger solvatochromism should be recorded. The
synthesis of such systems is under evaluation.
In conclusion, an improved method for cyclocon-
densation of some iodo-substituted phenacyl N,N-dial-
kyldithiocarbamates is described. These compounds
exhibit a larger negative solvatochromism than previ-
ously reported unsubstituted systems.
These results suggest a decrease in the ionization
energy of the phenolate moiety because of electronic
effects of substituents in both, aromatic ring and C-5
Experimental
Melting points were obtained on a Mel-Temp II apparatus. IR
spectra were recorded on a Bruker Tensor 27 instrument.
NMR spectra were recorded on a Bruker DPX-300 spectrom-
eter. Chemical shifts are reported in ppm downfield from TMS.
UV-Vis absorption spectra were recorded on a Varian Cary
100 Bio spectrophotometer. Elemental analyses (C, H, N, S)
were conducted using the CE440 Elemental Analyser; their
results were found to be in good agreement (ꢂ0.2%) with the
calculated values.
2-Bromo-1-(2-hydroxy-3-iodo-5-methylphenyl)butan-1-one
(1c, C11H12BrIO2)
Fig. 1 UV-Vis absorption spectra of mesoionic phenolate 4a
in different solvents ( —– MeOH; – – – – MeCN; ꢄ ꢄ ꢄ ꢄ ꢄ ꢄ
Me2Cl2; -ꢄ -ꢄ -ꢄ THF)
To a solution of 10g 1-(2-hydroxy-3-iodo-5-methylphenyl)bu-
tan-1-one (32 mmol) in 200cm3 glacial acetic acid a solution
of 1.7 cm3 bromine (32 mmol) in 10cm3 glacial acetic acid
was added under vigorous stirring. After decoloration the re-
action mixture was poured into 300cm3 water and the solid
was filtered off, dried, and recrystallized from EtOH. Yellow
crystals (8.5g, 69%) were obtained. Mp 109–110ꢃC; 1H NMR
(CDCl3): ꢂ ¼ 1.11 (t, J ¼ 7.2 Hz, CH3), 1.95 (m, CH2), 2.29 (s,
CH3), 5.23 (t, J ¼ 7.2 Hz, CH), 7.83 (d, J ¼ 2.1 Hz, Har-4),
7.90 (d, J ¼ 2.1 Hz, Har-6), 12.82 (s, OH) ppm; 13C NMR
(CDCl3): ꢂ ¼ 10.1 (CH3), 20.3 (CH3), 25.9 (CH2), 57.1 (CH),
84.6 (CHar), 126.9 (CHar), 130.1 (CHar), 131.9 (CHar), 144.5
(CHar), 163.3 (CHar), 194.5 (C) ppm; IR (ATR): ꢃꢀ¼ 3438,
Table 1 Long-wavelength, solvent dependent charge-transfer
absorption maxima, lmax=nm, of mesoionic phenolates 4a,
4d, and 4e, measured at 25ꢃC and at normal pressure
7a
394
425
430
438
ꢀ44
7d
371
409
413
425
ꢀ54
7e
360
405
406
409
ꢀ49
MeOH
MeCN
Me2Cl2
THF
Ál nm
2948, 1634, 1457, 1157, 862, 721, 679 cmꢀ1
.

1436
L. M. Birsa, L. V. Asaftei
2.01 (m, CH2), 2.26 (s, CH3), 4.06 (m, 2CH2–N), 5.82 (t,
J ¼ 7 Hz, CH), 7.80 (d, J ¼ 2.2 Hz, Har), 7.86 (d, J ¼ 2.2 Hz,
Har), 12.80 (s, OH) ppm; 13C NMR (DMSO-d6): ꢂ ¼ 11.9
(CH3), 20.4 (CH3), 23.2 (CH2), 24.3 (CH2), 24.5 (CH2),
24.6 (CH2), 52.3 (CH2–N), 54.1 (CH2–N), 56.6 (2-C), 86.3
(3-Car), 118.2 (Car), 130.2 (Car), 130.8 (Car), 146.8 (Car), 159.4
(Car), 194.4 (C), 203.1 (C) ppm. IR (ATR): ꢃꢀ¼ 3452, 2940,
2-(2-Hydroxy-3,5-diiodophenyl)-2-oxoethyl-N,N-dimethyldi-
thiocarbamate (2a, C11H11I2NO2S2). General Procedure
To a solution of 2.34g 2-bromo-1-(2-hydroxy-3,5-diiodophe-
nyl)ethan-1-one (1a) (5mmol) in 50 cm3 acetone a solution of
0.72g sodium N,N-dimethyldithiocarbamate (5mmol) in
10cm3 water=acetone (1:1) was added. The reaction mixture
was refluxed for 10 min, cooled and the obtained solid filtered,
washed with water, and dried. Recrystallization from 45cm3
dioxane gave yellow pale crystals, 1.8g (72%) 2a; mp 193–
194ꢃC (dec); 1H NMR (DMSO-d6): ꢂ ¼ 3.33 (s, CH3), 3.43 (s,
CH3), 4.95 (s, CH2), 8.24 (d, J ¼ 2.3 Hz, Har-4), 8.42 (d,
J ¼ 2.3 Hz, Har-6), 12.46 (s, 1H, OH) ppm; 13C NMR
(DMSO-d6): ꢂ ¼ 44.1 (CH2), 48.8 (CH3), 49.2 (CH3), 81.3
(Car), 87.7 (Car), 121.8 (Car), 138.3 (Car), 153.3 (Car), 161.1
(Car), 191.27 (C), 198.6 (C) ppm; IR (ATR): ꢃꢀ¼ 3440, 2938,
1634, 1434, 1229, 1152, 975, 786, 709 cmꢀ1
.
1-(2-Hydroxy-3-iodo-5-methylphenyl)-1-oxobutan-2-yl-
morpholine-4-carbodithioate (2f, C16H20INO3S2)
1
Yield 70%, yellow pale crystalls; mp 146–147ꢃC; H NMR
(DMSO-d6): ꢂ ¼ 1.01 (t, J ¼ 7.3 Hz, CH3), 2.01 (m, CH2), 2.29
(s, CH3), 3.76 (m, 2CH2), 4.13 (m, CH2), 5.84 (t, J ¼ 7 Hz,
CH), 7.80 (d, J ¼ 2.1 Hz, Har), 7.86 (d, J ¼ 2.1 Hz, Har), 12.71
(s, OH) ppm; 13C NMR (DMSO-d6): ꢂ ¼ 11.8 (CH3), 20.4
(CH3), 24.6 (CH2), 50.9 (CH2–N), 51.8 (CH2–N), 56.4 (CH2),
66.2 (CH2–O), 66.4 (CH2–O), 86.4 (Car), 118.2 (Car), 130.5
(Car), 130.9 (Car), 146.8 (Car), 159.5 (Car), 194.2 (C), 203.0
(C) ppm; IR (ATR): ꢃꢀ¼ 3448, 2940, 1634, 1429, 1231, 1150,
1633, 1478, 1238, 1145, 979, 759, 696 cmꢀ1
.
1-(2-Hydroxy-3,5-diiodophenyl)-1-oxopropan-2-yl-N,N-
dimethyldithiocarbamate (2b, C14H17I2NO2S2)
1
Yield 88%, pale yellow crystals; mp 128–129ꢃC; H NMR
968, 786, 695 cmꢀ1
.
(DMSO-d6): ꢂ ¼ 1.24 (t, J ¼ 5.5 Hz, 2CH3), 1.55 (d, J ¼ 6.7 Hz,
CH3); 3.71 (q, J ¼ 5.5 Hz, CH2–N), 4.01 (q, J ¼ 5.5 Hz, CH2–
N), 5.77 (q, J ¼ 6.7 Hz, CH), 8.20 (d, J ¼ 2.3 Hz, Har-4), 8.31
(d, J ¼ 2.3 Hz, Har-6), 12.80 (s, OH) ppm; 13C NMR (DMSO-
d6): ꢂ ¼ 12.1 (CH3), 12.6 (CH3), 17.5 (3-C), 47.5 (CH2–N),
50.8 (CH2–N), 51.4 (2-C), 80.5 (3-Car), 87.8 (5-Car), 120.2 (1-
Car), 139.0 (6-Car), 152.2 (4-Car), 160.1 (2-Car), 193.4 (C),
199.0 (C) ppm; IR (ATR): ꢃꢀ¼ 3445, 2934, 1631, 1481,
2-(Dimethylamino)-4-(2-Hydroxy-3,5-diiodophenyl)-1,3-
dithiol-2-ylium perchlorate (3a, C11H10ClI2NO5S2).
General Procedure
To a mixture of 3 cm3 P2O5–CH3SO3H (1:10) 1.01g dithio-
carbamate 2a (2mmol) were added in several portions. The
reaction mixture was stirred for 30min at room temperature.
To the homogeneous mixture 0.5 cm3 70% HClO4 were added
and the crude 3a was precipitated with 50cm3 AcOMe. This
was filtered off, dried, and recrystallized from 100 cm3 EtOH
to give the pure product as white crystals, 1.08 g (92%). Mp
1236, 1139, 985, 757, 689 cmꢀ1
.
1-(2-Hydroxy-3,5-diiodophenyl)-1-oxapropan-2-yl-
piperidine-1-carbodithioate (2c, C15H17I2NO2S2)
1
1
209–210ꢃC (dec); H NMR (DMSO-d6): 3.51 (s, CH3), 3.53
Yield 88%, pale yellow crystals; mp 134–135ꢃC; H NMR
(DMSO-d6): ꢂ ¼ 1.54 (d, J ¼ 6.6 Hz, CH3), 1.66 (m, 3CH2),
4.04 (m, 2CH2–N), 5.78 (q, J ¼ 6.7 Hz, CH), 8.19 (d, J ¼
2.4 Hz, Har-4), 8.31 (d, J ¼ 2.4 Hz, Har-6), 12.79 (s, OH) ppm;
13C NMR (DMSO-d6): ꢂ ¼ 17.5 (CH3), 23.5 (CH2), 24.3 (CH2),
24.5 (CH2), 51.5 (CH2), 52.5 (CH2–N), 54.2 (CH2–N), 82.0
(Car), 89.4 (Car), 125.5 (Car), 138.9 (Car), 151.6 (Car), 160.7
(Car), 193.0 (C), 198.2 (C) ppm; IR (ATR): ꢃꢀ¼ 3446, 2935,
(s, CH3), 7.88 (d, J ¼ 1.8 Hz, Har), 8.02 (s, CH), 8.12 (d, J ¼
1.8 Hz, Har), 10.42 (s, OH) ppm; 13C NMR (DMSO-d6): ꢂ ¼
47.3 (CH3), 47.7 (CH3), 85.5 (Car), 92.8 (Car), 121.6 (CH),
122.7 (Car), 132.9 (C), 137.1 (Car), 147.9 (Car), 153.5 (Car),
186.9 (C) ppm; IR (ATR): ꢃꢀ¼ 3441, 2943, 1577, 1448, 1273,
1087 (b), 846, 623 cmꢀ1
.
Compounds 3b–3f were obtained using the same experi-
mental conditions.
1634, 1448, 1232, 1147, 972, 783, 695 cmꢀ1
.
1-(2-Hydroxy-3,5-diiodophenyl)-1-oxopropan-2-yl-mor-
2-(Diethylamino)-4-(2-hydroxy-3,5-diiodophenyl)-5-methyl-
1,3-dithiol-2-ylium perchlorate (3b, C14H16ClI2NO5S2)
Yield 84%, white crystals; mp 159–160ꢃC; 1H NMR (DMSO-
d6): ꢂ ¼ 1.32 (t, J ¼ 7.3 Hz, CH3), 1.35 (t, J ¼ 7.0 Hz, CH3),
2.23 (s, CH3), 3.82 (q, J ¼ 7.3 Hz, CH2), 3.87 (q, J ¼ 7.0 Hz,
CH2), 7.64 (d, J ¼ 1.9 Hz, Har), 8.14 (d, J ¼ 1.9 Hz, Har), 10.24
(s, OH) ppm; 13C NMR (DMSO-d6): ꢂ ¼ 10.8 (CH3), 10.8
(CH3), 15.2 (CH3), 53.6 (CH2), 53.7 (CH2), 83.2 (Car), 91.33
(Car), 118.8 (C), 127.2 (Car), 134.3 (C), 139.6 (Car), 148.4
(Car), 155.6 (Car), 184.3 (C) ppm; IR (ATR): ꢃꢀ¼ 3345,
pholine-4-carbodithioate (2d, C14H15I2NO3S2)
1
Yield 72%, pale yellow crystals; mp 173–174ꢃC; H NMR
(DMSO-d6): ꢂ ¼ 1.54 (d, J ¼ 6.7 Hz, CH3), 3.73 (m, 2CH2),
4.08 (m, 2CH2), 5.78 (q, J ¼ 6.7Hz, CH), 8.19 (d, J ¼ 2.3 Hz,
Har), 8.32 (d, J ¼ 2.3 Hz, Har), 12.68 (s, OH) ppm; 13C NMR
(DMSO-d6): ꢂ ¼ 17.3 (CH3), 51.1 (CH2), 51.9 (CH2–N), 52.0
(CH2–N), 66.5 (CH2–O), 66.5 (CH2–O), 81.5 (Car), 90.3
(Car), 122.2 (Car), 140.1 (Car), 152.1 (Car), 162.1 (Car), 191.8
(C), 198.4 (C) ppm. IR (ATR): ꢃꢀ¼ 3446, 2939, 1632, 1425,
1231, 1151, 982, 781, 710 cmꢀ1
.
2998, 1542, 1450, 1095 (b), 851, 613cmꢀ1
.
1-(2-Hydroxy-3-iodo-5-methylphenyl)-1-oxobutan-2-yl-
4-(2-Hydroxy-3,5-diiodophenyl)-5-methyl-2-(piperidin-1-yl)-
1,3-dithiol-2-ylium perchlorate (3c, C15H16ClI2NO5S2)
Yield 85%, white crystals; mp 190–191ꢃC; 1H NMR (DMSO-
d6): ꢂ ¼ 1.67 (m, CH2), 1.82 (m, 2CH2), 2.24 (s, CH3), 3.83
piperidine-1-carbodithioate (2e, C17H22INO2S2)
1
Yield 68%, yellow pale crystals; mp 182–183ꢃC; H NMR
(DMSO-d6): ꢂ ¼ 0.98 (t, J ¼ 7.3 Hz, CH3), 1.68 (m, 3CH2),

Solvatochromism of mesoionic iodo(1,3-dithiol-2-ylium-4-yl)phenolates
1437
(m, 2CH2), 7.62 (d, J ¼ 2.0 Hz, Har), 8.16 (d, J ¼ 2.0 Hz, Har),
10.32 (s, OH) ppm; 13C NMR (DMSO-d6): 15.3 (CH3), 21.6
(CH2), 24.9 (CH2), 56.5 (CH2–N), 57.1 (CH2–N), 83.9 (Car),
91.2 (Car), 118.9 (C), 126.7 (Car), 134.0 (C), 139.7 (Car), 148.5
(Car), 155.4 (Car), 184.8 (C) ppm; IR (ATR): ꢃꢀ¼ 3339, 1545,
Compounds 4b–4f were obtained in the same experimental
conditions.
2-[2-(Diethylamino)-5-methyl-1,3-dithiolium-4-yl]-4,6-
diiodophenolate (4b, C14H15I2NOS2)
1451, 1248, 1088 (b), 885, 624 cmꢀ1
.
1
Yield 100%, yellow crystals; mp 192–193ꢃC (dec); H NMR
(DMSO-d6): ꢂ ¼ 1.31 (t, J ¼ 7.2 Hz, CH3), 1.34 (t, J ¼ 7.2 Hz,
CH3), 2.23 (s, CH3-5), 3.82 (q, J ¼ 7.2 Hz, CH2), 3.87 (q, J ¼
7.2 Hz, CH2), 7.62 (d, J ¼ 1.9 Hz, Har), 8.12 (d, J ¼ 1.9 Hz,
Har) ppm; 13C NMR (DMSO-d6): 10.35(CH3), 10.4 (CH3),
15.3 (CH3), 53.8 (CH2), 53.9 (CH2), 83.3 (Car), 91.2 (Car),
118.3 (C), 127.1 (Car), 134.5 (C), 139.8 (Car), 148.6 (Car),
155.6 (Car), 184.0 (C) ppm; IR (ATR): ꢃꢀ¼ 3410, 2943,
4-(2-Hydroxy-3,5-diiodophenyl)-5-methyl-2-(morpholin-4-
yl)-1,3-dithiol-2-ylium perchlorate (3d, C14H14ClI2NO6S2)
Yield 95%, white crystals; mp 216–217ꢃC; 1H NMR (DMSO-
d6): ꢂ ¼ 2.23 (s, CH3), 3.42 (m, 2CH2N), 3.86 (m, 2CH2O),
7.63 (d, J ¼ 2.1 Hz, Har), 8.17 (d, J ¼ 2.1 Hz, Har), 10.28 (s,
OH) ppm; 13C NMR (DMSO-d6): ꢂ ¼ 15.3 (CH3), 54.2 (CH2–
N), 54.3 (CH2–N), 65.0 (CH2–O), 84.0 (Car), 91.3 (Car), 119.1
(C), 126.5 (Car), 134.1 (C), 139.8 (Car), 148.6 (Car), 155.3
(Car), 186.0 (C) ppm; IR (ATR): ꢃꢀ¼ 3252, 1549, 1455,
1550, 1456, 1259, 1132cmꢀ1
.
4,6-Diiodo-2-[5-methyl-2-(piperidin-1-yl)-1,3-dithiol-2-
1289, 1105 (b), 884, 623 cmꢀ1
.
ylium-4-yl]phenolate (4c, C15H15I2NOS2)
1
Yield 100%, yellow crystals; mp 194–195ꢃC (dec); H NMR
(DMSO-d6): ꢂ ¼ 1.76 (m, 3CH2), 2.23 (s, CH3), 3.85 (m,
2CH2), 7.60 (d, J ¼ 2.0 Hz, Har), 8.15 (d, J ¼ 2.0 Hz, Har)
ppm; 13C NMR (DMSO-d6): ꢂ ¼ 15.2 (CH3), 21.3 (CH2),
24.6 (CH2), 56.3 (CH2–N), 57.0 (CH2–N), 83.3 (Car), 91.2
(Car), 118.7 (C), 126.3 (Car), 133.9 (C), 139.2 (Car), 148.6
(Car), 155.3 (Car), 184.3 (C) ppm; IR (ATR): ꢃꢀ¼ 3407,
4-Ethyl-5-(2-hydroxy-3-iodo-5-methylphenyl)-2-(piperidin-
1-yl)-1,3-dithiol-2-ylium perchlorate (3e, C17H21ClINO5S2)
Yield 83%, white crystals; mp 197–198ꢃC; 1H NMR (CDCl3):
ꢂ ¼ 1.25 (t, J ¼ 7.6 Hz, CH3), 1.80 (m, CH2), 1.94 (m, 2CH2),
2.26 (s, CH3), 2.64 (q, J ¼ 7.6 Hz, CH2), 3.85 (m, 2CH2), 6.28
(s, OH), 7.02 (d, J ¼ 2.0 Hz, Har), 7.64 (d, J ¼ 2.0 Hz, Har)
ppm; 13C NMR (CDCl3): ꢂ ¼ 14.6 (CH3), 19.8 (CH3), 21.5
(CH2), 23.3 (CH2), 24.7 (CH2), 56.4 (CH2–N), 56.6 (CH2–N),
77.2 (Car), 86.7 (Car), 114.3 (C), 126.7 (Car), 132.2 (Car), 132.2
(C), 142.0 (Car), 151.5 (Car), 185.4 (C) ppm; IR (ATR): ꢃꢀ¼
2951, 2865, 1465, 1259, 1139, 1023, 881cmꢀ1
.
4,6-Diiodo-2-[5-methyl-2-(morpholin-4-yl)-1,3-dithiol-2-
ylium-4-yl]phenolate (4d, C14H13I2NO2S2)
1
Yield 100%, yellow crystals; mp 184–185ꢃC (dec); H NMR
3381, 2951, 2874, 1525, 1444, 1272, 1091 (b), 863, 621 cmꢀ1
.
(DMSO-d6): ꢂ ¼ 2.22 (s, CH3), 3.44 (m, 2CH2N), 3.84 (m,
2CH2O), 7.61 (d, J ¼ 2.0 Hz, Har), 8.15 (d, J ¼ 2.0 Hz, Har)
ppm; 13C NMR (DMSO-d6): ꢂ ¼ 15.2 (CH3), 54.3 (CH2–N),
65.5 (CH2–O), 83.8 (Car), 91.3 (Car), 119.1 (C), 126.3 (Car),
134.6 (C), 139.3 (Car), 148.9 (Car), 155.3 (Car), 186.2 (C) ppm;
IR (ATR): ꢃꢀ¼ 3407, 2926, 1553, 1439, 1268, 1121, 1044,
4-Ethyl-5-(2-hydroxy-3-iodo-5-methylphenyl)-2-(morpholin-
4-yl)-1,3-dithiol-2-ylium perchlorate (3f, C16H19ClINO6S2)
Yield 94%, white crystals; mp 187–188ꢃC; 1H NMR (DMSO-
d6): ꢂ ¼ 1.25 (t, J ¼ 7.5 Hz, CH3), 2.27 (s, CH3), 2.64 (q,
J ¼ 7.5 Hz, CH2), 3.44 (m, 2CH2N), 3.87 (m, 2CH2O), 7.57
(d, J ¼ 2.0 Hz, Har), 8.09 (d, J ¼ 2.0 Hz, Har), 10.33 (s, OH)
ppm; 13C NMR (DMSO-d6): ꢂ ¼ 14.7 (CH3), 19.9 (CH3), 21.5
(CH2), 54.6 (CH2–N), 55.0 (CH2–N), 65.2 (CH2–O), 84.1
(Car), 91.5 (Car), 119.2 (C), 126.6 (Car), 134.5 (C), 139.8
(Car), 148.75 (Car), 155.8 (Car), 186.5 (C) ppm; IR (ATR):
886 cmꢀ1
.
2-[5-Ethyl-2-(piperidin-1-yl)-1,3-dithiol-2-ylium-4-yl]-6-
iodo-4-methylphenolate (4e, C17H20INOS2)
1
Yield 100%, yellow crystals; mp 173–174ꢃC (dec); H NMR
(CDCl3): 1.22 (t, J ¼ 7.5 Hz, CH3), 1.76 (m, CH2), 1.87 (m,
2CH2), 2.24 (s, CH3), 2.69 (q, J ¼ 7.5 Hz, CH2), 3.67 (m,
CH2), 3.73 (m, CH2), 6.94 (d, J ¼ 1.6 Hz, Har), 7.58 (d, J ¼
1.6 Hz, Har) ppm; 13C NMR (CDCl3): ꢂ ¼ 14.8 (CH3), 19.8
(CH3), 21.7 (CH2), 23.6 (CH2), 24.9 (CH2), 56.0 (CH2–N),
77.4 (Car), 90.6 (Car), 115.9 (C), 128.5 (Car), 131.3 (Car), 137.8
(C), 141.4 (Car), 155.9 (Car), 185.4 (C) ppm; IR (ATR):
ꢃꢀ¼ 3375, 2942, 1532, 1450, 1268, 1098 (b), 859, 630 cmꢀ1
.
2-[2-(Dimethylamino)-1,3-dithiol-2-ylium-4-yl]-4,6-
diiodophenolate (4a, C11H9I2NOS2). General Procedure
To a saturated sodium hydrogencarbonate solution 0.59 g per-
chlorate 3a (1mmol) was added. Carbon dioxide evolved and
the reaction mixture became yellow. After 2 h under vigorous
stirring at room temperature, the yellow solid was filtered off,
washed with water, and dried. Recrystallization from DMF=
AcOMe afforded the pure product as yellow crystals, 0.49g
(100%). Mp 208–209ꢃC (dec); 1H NMR (DMSO-d6): ꢂ ¼ 3.50
(s, CH3), 3.52 (s, CH3), 7.67 (d, J ¼ 1.9 Hz, Har), 8.00 (s, CH),
8.10 (d, J ¼ 1.9 Hz, Har) ppm; 13C NMR (DMSO-d6): ꢂ ¼ 47.1
(CH3), 47.5 (CH3), 85.3 (Car), 92.6 (Car), 121.3 (C), 122.4
(Car), 132.8 (C), 137.4 (Car), 147.2 (Car), 153.1 (Car), 186.3
(C) ppm; IR (ATR): ꢃꢀ¼ 3432, 2926, 1551, 1439, 1267, 1062,
ꢃꢀ¼ 3415, 2951, 2848, 1534, 1465, 1259, 1095, 863 cmꢀ1
.
2-[5-Ethyl-2-(morpholin-4-yl)-1,3-dithiol-2-ylium-4-yl]-6-
iodo-4-methylphenolate (4f, C16H18INO2S2)
Yield 100%, yellow crystals; mp 87–88ꢃC; 1H NMR (DMSO-
d6): ꢂ ¼ 1.23 (t, J ¼ 7.6 Hz, CH3), 2.25 (s, CH3), 2.63 (q, J ¼
7.6 Hz, CH2), 3.47 (m, 2CH2N), 3.92 (m, 2CH2O), 7.51 (d,
J ¼ 1.8 Hz, Har), 8.05 (d, J ¼ 1.8 Hz, Har) ppm; 13C NMR
(DMSO-d6): ꢂ ¼ 14.2 (CH3), 19.7 (CH3), 21.3 (CH2), 54.8
(CH2–N), 65.0 (CH2–O), 84.0 (Car), 91.9 (Car), 119.3 (C),
126.3 (Car), 134.0 (C), 139.3 (Car), 148.0 (Car), 156.0 (Car),
863 cmꢀ1
.

1438
L. M. Birsa, L. V. Asaftei
185.3 (C) ppm; IR (ATR): ꢃꢀ¼ 3410, 2946, 1528, 1458, 1263,
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