Benzazoles: III. Synthesis and Transformations of 6-(Chlorosulfonyl)-1,3-benzothiazol-2(3H)-ones

Article abstract of DOI:10.1134/S1070428020090031

Abstract: Treatment of 1,3-benzothiazol-2(3H)-one andits 3-methyl derivative with chlorosulfonic acid afforded the corresponding2-oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonyl chlorides which reacted withwater, alcohols, and amines to give2-oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonic acids and their esters andamides.

Full text of DOI:10.1134/S1070428020090031

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2020, Vol. 56, No. 9, pp. 1519–1524. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Organicheskoi Khimii, 2020, Vol. 56, No. 9, pp. 1337–1343.
Benzazoles: III.1 Synthesis and Transformations
of 6-(Chlorosulfonyl)-1,3-benzothiazol-2(3H)-ones
D. A. Dushamova,*, Yu. R. Takhirova, R. Sh. Kuryazova, and N. S. Mukhamedovb
a Urgench State University, Urgench, 220100 Uzbekistan
b Yunusov Institute of the Chemistry of Plant Substances, Tashkent, 100170 Uzbekistan
*e-mail: dilshod.d71@mail.ru
Received May 18, 2020; revised June 1, 2020; accepted June 9, 2020
Abstract—Treatment of 1,3-benzothiazol-2(3H)-one and its 3-methyl derivative with chlorosulfonic acid
afforded the corresponding 2-oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonyl chlorides which reacted with water,
alcohols, and amines to give 2-oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonic acids and their esters and amides.
Keywords: 2-oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonamides, 2-oxo-2,3-dihydro-1,3-benzothiazole-6-sul-
fonic acid esters, 2-oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonic acids, 2-oxo-2,3-dihydro-1,3-benzothiazole-
6-sulfonyl chlorides, electrophilic substitution, nucleophilic substitution
DOI: 10.1134/S1070428020090031
Benzothiazole derivatives have attracted much
interest due to their high biological activity and broad
spectrum of action [2–5]. In particular, compounds
exhibiting fungicidal [2], herbicidal [3], growth-
stimulating [4], and defoliating activities [5] were
found among benzothiazole derivatives. In continuation
of out studies on electrophilic substitution in the series
of nitrogen heterocycles [6–11], herein we report
chlorosulfonation of 1,3-benzothiazol-2(3H)-one (1a)
and 3-methyl-1,3-benzothiazol-2(3H)-one (1b) and
some chemical transformations of their chlorosulfonyl
derivatives.
Compounds 1a and 1b reacted with chlorosulfonic
acid to give the corresponding 6-chlorosulfonyl deriva-
tives 2a and 2b, regardless of the reactant ratio. The
best yields of 2a and 2b (83 and 87%, respectively)
were obtained using 5 equiv of chlorosulfonic acid
(Scheme 1). It should be noted that intermediate 2-oxo-
2,3-dihydro-1,3-benzothiazole-6-sulfonic acids 3a and
3b could not be isolated. Presumably, the hydroxy
group on the sulfur atom is readily replaced by chlorine
due to increased positive charge on the sulfonyl sulfur
atom. Sulfonic acids 3a and 3b were obtained with
high yields by hydrolysis of 2a and 2b, respectively. In
Scheme 1.
O
O
S
S
O
N
S
N
HO
O
R
R
1a, 1b
3a, 3b
O
O
ClSO3H
50–60°C, 2 h
83–87%
H2O, 100°C, 2 h
91–92%
S
S
N
Cl
O
ClSO3H
50–60°C, 1 h
96–98%
R
2a, 2b
1–3, R = H (a), Me (b).
1
For communication II, see [1].
1519

DUSHAMOV et al.
1520
Scheme 2.
O
O
O
O
O
O
R22NH, Me2CO
20°C, 2 h
R3OH, Me2CO
20°C, 2 h
R2
S
S
S
S
N
S
S
N
N
Cl
R3O
O
O
O
R2
64–82%
64–68%
N
R1
R1
R1
4a–4h
2a, 2b
5a–5d
2, R = H (a), Me (b); 4: R1 = H (a, b, e, f), Me (c, d, g, h); R2 = Et (a, c), Bu (b, d); R22N = piperidin-1-yl (e, g),
morpholin-4-yl (f, h); 5, R1 = H (a, b), Me (c, d); R3 = Me (a, c), Et (b, d).
turn, sulfonic acids 3a and 3b were smoothly and
quantitatively converted to sulfonyl chlorides 2a and
2b by treatment with chlorosulfonic acid (Scheme 1).
formation of fragment ion with m/z 214. Methyl-
substituted analog 2b decomposed via elimination of
methyl radical with the formation of fragment ion with
m/z 248 (Fig. 1). Regardless of the substituent on the
benzothiazole nitrogen atom and on C6, the mass
spectra of sulfonamides 4 and sulfonic acid esters 5
showed similar fragmentation patterns involving cleav-
age of the SO2–N or SO2–O bond and formation of
fragments A and B (Fig. 2).
The 1H NMR spectra of 2–5 contained signals from
aromatic protons at δ 7.02–7.21 (d, J4,5 = 8.4–8.9 Hz,
4-H), 7.59–7.79 (d.d, J5,4 = 8.4–8.9 Hz, J5,7 = 1.6–
1.9 Hz, 5-H), and 7.76–7.95 ppm (d, J7,5 = 1.6–1.9 Hz,
7-H). The N3H proton resonated at a low field (δ 9.17–
9.31 ppm), and signals of alkyl protons in the amide
or ester moiety were located in the expected upfield
regions (δ 0.77–3.73 ppm).
Sulfonyl chlorides 2a and 2b readily reacted with
aliphatic (diethylamine, dibutylamine) and heterocyclic
secondary amines (piperidine, morpholine) at room
temperature in acetone in the presence of triethylamine
to produce the corresponding N,N-dialkyl sulfonamides
4a–4h with high yields. Sulfonic acid esters 5a–5d
were synthesized by reacting 2a and 2b with methanol
and ethanol (Scheme 2).
The structure of compounds 2–5 was confirmed by
IR, 1H NMR, and mass spectra and elemental analyses.
The IR spectra of 2–5 characteristically showed
asymmetric (1220–1409 cm–1) and symmetric (1055–
1215 cm–1) stretching vibration bands of the sulfonyl
group, as well as C–S stretchings at 709–756 cm–1. In
addition, the IR spectra of 3a and 3b contained an ab-
sorption band at 645– 655 cm–1 due to S–O stretching
vibrations. Out-of-plane C–H bending vibrations of
the 1,2,4-trisubstituted benzene ring were observed at
805–825 and 870–880 cm–1.
EXPERIMENTAL
The IR spectra were recorded in KBr on a Perkin
Elmer 2000 spectrometer (USA). The 1H NMR spectra
were run on a Varian Unity 400 Plus spectrometer
(USA) at 400 MHz using DMSO-d6 as solvent and
tetramethylsilane as internal standard. The mass spectra
(electron impact, 70 eV) were obtained on a Kratos
MS-30 mass spectrometer (UK) with direct sample
The mass spectra of 2–5 displayed the molecular
and fragment ion peaks in agreement with the proposed
structures. Fragmentation of the molecular ion of 2a
involves initial dissociation of the S–Cl bond with the
O
S
S
·
Cl
O
+
O
+·
N
O
O
S
R
S
Cl
m/z 214
O
N
O
O
R
S
S
N
2a, 2b, M+·
·
R
Cl
+
O
m/z 248
Fig. 1. Fragmentation of sulfonyl chlorides 2a and 2b under electron impact.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 9 2020

BENZAZOLES: III.
1521
+
O
S
S
N
2
2 ·
·
O
+
[R NR ]
O
+·
O
O
R2
S
R1
S
N
N
A
B
O
R2
·
O
S
R1
S
N
4a–4h, M+·
2
2 +
·
O
+
[R NR ]
O
R1
A
B
+
O
S
S
N
3
·
O
+
R O
O
+·
O
O
R3
S
R1
S
N
O
A
B
O
·
O
S
R1
S
N
5a–5d, M+·
3
+
·
O
+
R O
O
R1
A
B
Fig. 2. Fragmentation of sulfonamides 4a–4h and sulfonic acid esters 5a–5d under electron impact.
2-Oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonyl
admission into the ion source. The elemental analyses
were carried out with a EuroVector EA-3000 automated
CHNS analyzer (Italy). The melting points were meas-
ured on Boetius (Germany) and MEL-TEMP (USA)
melting point apparatuses. The progress of reactions
and the purity of the isolated compounds were moni-
tored by TLC on Silufol UV-254 plates using benzene–
acetone (10:1) as eluent; spots were visualized under
UV light and by treatment with iodine vapor.
chloride (2a). Yield 2.07 g (83%), colorless crystals,
mp 168–170°C (from heptane). IR spectrum, ν, cm–1
:
1365 s (SO2, asym.), 1175 s (SO2, sym.), 725 s (C–S).
1H NMR spectrum, δ, ppm: 7.14 d (1H, 4-H, J =
8.4 Hz), 7.79 d.d (1H, 5-H, J = 1.6, 8.4 Hz), 7.95 d
(1H, 7-H, J = 1.6 Hz), 9.31 s (1H, NH). Mass spectrum:
m/z 249 (Irel 81%) (35Cl). Found, %: C 33.43; H 1.58;
N 5.83; S 25.52. C7H4ClNO3S2. Calculated, %:
C 33.66; H 1.60; N 5.61; S 25.65.
Initial 1,3-benzothiazol-2(3H)-one (1a) was synthe-
sized by oxidation of 1,3-benzothiazole-2(3H)-thione
with potassium permanganate, and 3-methyl-1,3-ben-
zothiazol-2(3H)-one (1b) was prepared by phase-
transfer alkylation of 1a with dimethyl sulfate.
3-Methyl-2-oxo-2,3-dihydro-1,3-benzothiazole-6-
sulfonyl chloride (2b). Yield 2.29 g (87%), colorless
crystals, mp 151–152°C (from benzene). IR spectrum,
ν, cm–1: 1370 s (SO2, asym.), 1181 s (SO2, sym.), 730 s
1
(C–S). H NMR spectrum, δ, ppm: 3.41 s (3H, CH3),
Sulfonyl chlorides 2a and 2b (general procedures).
a. Chlorosulfonic acid, 5.83 g (50 mmol), was cooled
to 5–10°C, and 10 mmol of compound 1a or 1b was
added in portions with stirring at such a rate that the
temperature did not exceed 15°C. The mixture was
then heated to 50–60°C, kept for 2 h at that tempera-
ture, and poured onto crushed ice. The precipitate of 2a
or 2b was filtered off, washed with water, and
recrystallized.
7.21 d (1H, 4-H, J = 8.4 Hz), 7.77 d.d (1H, 5-H, J =
1.6, 8.4 Hz), 7.93 d (1H, 7-H, J = 1.6 Hz). Mass
spectrum: m/z 263 (Irel 81%) [M]+ (35Cl). Found, %:
C 36.27; H 2.19; N 5.12; S 24.14. C8H6ClNO3S2. Cal-
culated, %: C 36.43; H 2.27; N 5.31; S 24.29.
b. Chlorosulfonic acid, 2.33 g (20 mmol), was
cooled to 0°C, and 10 mmol of sulfonic acid 3a or 3b
was added in portions with stirring at such a rate that
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 9 2020

DUSHAMOV et al.
1522
the temperature did not exceed 10°C. The mixture was
then heated to 50–60°C, kept at that temperature for
1 h, and poured onto crushed ice. The precipitate was
filtered off, washed with water, and recrystallized.
Yield 96% (2a), 98% (2b). The products were identical
to samples prepared as described above in a (no
depression of the melting point was observed on
mixing).
Found, %: C 45.87; H 4.78; N 10.01; S 22.22.
C11H14N2O3S2. Calculated, %: C 46.15; H 4.89;
N 9.79; S 22.37.
N,N-Dibutyl-2-oxo-2,3-dihydro-1,3-benzothia-
zole-6-sulfonamide (4b). Yield 2.29 g (67%), colorless
crystals, mp 95–97°C (from EtOH). IR spectrum, ν,
cm–1: 1354 s (SO2, asym.), 1164 s (SO2, sym.), 734 s
1
(C–S). H NMR spectrum, δ, ppm: 0.83–0.91 m (6H,
CH3), 1.12–1.16 m (4H, CH2CH3), 1.38–1.46 m (4H,
NCH2CH2), 3.11–3.21 m (4H, NCH2), 7.14 d (1H,
4-H, J = 8.9 Hz), 7.73 d.d (1H, 5-H, J = 1.8, 8.9 Hz),
7.89 d (1H, 7-H, J = 1.8 Hz), 9.19 s (1H, NH). Mass
spectrum: m/z 342 (Irel 32%) [M]+. Found, %: C 52.37;
H 6.29; N 7.99; S 18.52. C15H22N2O3S2. Calculat-
ed, %: C 52.63; H 6.43; N 8.18; S 18.71.
Sulfonic acids 3a and 3b (general procedure).
A mixture of 10 mmol of compound 2a or 2b and
20 mL of water was refluxed for 2 h. The mixture was
partially evaporated, and the precipitate was filtered off
and recrystallized from water.
2-Oxo-2,3-dihydro-1,3-benzothiazole-6-sulfonic
acid (3a). Yield 2.10 g (91%), colorless crystals,
mp 238–240°C (from H2O). IR spectrum, ν, cm–1:
1220 s (SO2, asym.), 1055 s (SO2, sym.), 745 s (C–S),
N,N-Diethyl-3-methyl-2-oxo-2,3-dihydro-1,3-
benzothiazole-6-sulfonamide (4c). Yield 2.46 g
(82%), colorless crystals, mp 136–138°C (from EtOH–
H2O). IR spectrum, ν, cm–1: 1353 s (SO2, asym.),
1167 s (SO2, sym.), 756 s (C–S). 1H NMR spectrum, δ,
ppm: 1.08 t (6H, CH2CH3, J = 7.2 Hz), 2.53 q (4H,
NCH2, J = 7.2 Hz), 7.02 d (1H, 4-H, J = 8.6 Hz),
7.69 d.d (1H, 5-H, J = 1.8, 8.6 Hz), 7.85 d (1H, 7-H,
J = 1.8 Hz). Mass spectrum: m/z 300 (Irel 36%) [M]+.
Found, %: C 47.72; H 5.15; N 9.61; S 21.21.
C12H16N2O3S2. Calculated, %: C 47.99; H 5.33;
N 9.33, S 21.33.
1
645 s (S–O). H NMR spectrum, δ, ppm: 7.04 d (1H,
4-H, J = 8.5 Hz), 7.68 d.d (1H, 5-H, J = 1.6, 8.5 Hz),
7.82 d (1H, 7-H, J = 1.6 Hz), 9.27 s (1H, NH). Mass
spectrum: m/z 231 (Irel 38%) [M]+. Found, %: C 36.15;
H 2.11; N 5.83; S 27.58. C7H5NO4S2. Calculated, %:
C 36.36; H 2.16; N 6.06; S 27.70.
3-Methyl-2-oxo-2,3-dihydro-1,3-benzothiazole-6-
sulfonic acid (3b). Yield 2.25 g (92%), colorless
crystals, mp 228–230°C (from H2O). IR spectrum, ν,
cm–1: 1230 s (SO2, asym.), 1070 s (SO2, sym.), 757 s
(C–S), 655 s (S–O). 1H NMR spectrum, δ, ppm: 3.40 s
(3H, CH3), 7.09 d (1H, 4-H, J = 8.6 Hz), 7.68 d.d (1H,
5-H, J = 1.7, 8.6 Hz), 7.83 d (1H, 7-H, J = 1.7 Hz).
Mass spectrum: m/z 245 (Irel 41%) [M]+. Found, %:
C 39.06; H 2.78; N 5.82; S 25.88. C8H7NO4S2.
Calculated, %: C 39.18; H 2.86; N 6.06; S 26.12.
N,N-Dibutyl-3-methyl-2-oxo-2,3-dihydro-1,3-
benzothiazole-6-sulfonamide (4d). Yield 2.35 g
(66%), colorless crystals, mp 91–92°C (from EtOH–
H2O). IR spectrum, ν, cm–1: 1348 s (SO2, asym.),
1164 s (SO2, sym.), 741 s (C–S). 1H NMR spectrum, δ,
ppm: 0.77–0.87 m (6H, CH2CH3), 1.38–1.46 m (4H,
CH2CH3), 1.57–1.64 m (4H, NCH2CH2), 3.11–3.21 m
(4H, NCH2), 3.39 s (3H, 3-CH3), 7.05 d (1H, 4-H, J =
8.7 Hz), 7.69 d.d (1H, 5-H, J = 1.7, 8.7 Hz), 7.87 d
(1H, 7-H, J = 1.7 Hz). Mass spectrum: m/z 356
(Irel 28%) [M]+. Found, %: C 53.77; H 6.66; N 8.15;
S 17.76. C16H24N2O3S2. Calculated, %: C 53.93;
H 6.74; N 7.86; S 17.97.
Sulfonamides 4a–4h (general procedure). Com-
pound 2a or 2b, 10 mmol, was dissolved in 20 mL of
acetone, and a solution of 10 mmol of the correspond-
ing secondary amine and 1.01 g (10 mmol) of triethyl-
amine in 10 mL of acetone was added dropwise. The
mixture was stirred at room temperature for 2 h, the
solvent was distilled off, the residue was treated with
100 mL of water, and the precipitate was filtered off
and purified by recrystallization.
6-(Piperidin-1-ylsulfonyl)-1,3-benzothiazol-
2(3H)-one (4e). Yield 2.11 g (71%), colorless crystals,
mp 211–213°C (from EtOH). IR spectrum, ν, cm–1:
1343 s (SO2, asym.), 1166 s (SO2, sym.), 745 s (C–S).
1H NMR spectrum, δ, ppm: 2.44–2.49 m (2H, 4′-H),
2.86 q (4H, 3′-H, 5′-H, J = 6.9 Hz), 3.61 q (4H, 2′-H,
6′-H, J = 6.9 Hz), 7.04 d (1H, 4-H, J = 8.9 Hz),
7.65 d.d (1H, 5-H, J = 1.8, 8.9 Hz), 7.79 d (1H, 7-H,
J = 1.8 Hz), 9.18 s (1H, NH). Mass spectrum: m/z 298
(Irel 100%) [M]+. Found, %: C 48.09; H 4.57; N 9.09;
S 21.22. C12H14N2O3S2. Calculated, %: C 48.32;
H 4.69; N 9.39; S 21.47.
N,N-Diethyl-2-oxo-2,3-dihydro-1,3-benzothia-
zole-6-sulfonamide (4a). Yield 1.86 g (65%), colorless
crystals, mp 150–152°C (from EtOH). IR spectrum, ν,
cm–1: 1347 s (SO2, asym.), 1175 s (SO2, sym.), 746 s
1
(C–S). H NMR spectrum, δ, ppm: 1.05 t (6H,
CH2CH3, J = 7.2 Hz), 2.47 q (4H, NCH2, J = 7.2 Hz),
7.09 d (1H, 4-H, J = 8.9 Hz), 7.75 d.d (1H, 5-H, J =
1.8, 8.9 Hz), 7.92 d (1H, 7-H, J = 1.8 Hz), 9.21 s (1H,
NH). Mass spectrum: m/z 286 (Irel 29%) [M]+.
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BENZAZOLES: III.
1523
Mass spectrum: m/z 245 (Irel 39%) [M]+. Found, %:
C 38.92; H 2.71; N 5.92; S 25.88. C8H7NO4S2.
Calculated, %: C 39.18; H 2.85; N 5.71; S 26.12.
6-(Morpholin-4-ylsulfonyl)-1,3-benzothiazol-
2(3H)-one (4f). Yield 2.07 g (69%), colorless crystals,
mp 213–215°C (from EtOH). IR spectrum, ν, cm–1:
1345 s (SO2, asym.), 1169 s (SO2, sym.), 749 s (C–S).
1H NMR spectrum, δ, ppm: 2.87 t (4H, CH2OCH2, J =
7.9 Hz), 3.60 t (4H, CH2NCH2, J = 7.9 Hz), 7.07 d
(1H, 4-H, J = 8.8 Hz), 7.68 d.d (1H, 5-H, J = 1.8,
8.8 Hz), 7.81 d (1H, 7-H, J = 1.8 Hz), 9.17 s (1H, NH).
Mass spectrum: m/z 300 (Irel 56%) [M]+. Found, %:
C 43.87; H 3.87; N 9.61; S 21.14. C11H12N2O4S2.
Calculated, %: C 44.00; H 3.99; N 9.33; S 21.33.
Ethyl 2-oxo-2,3-dihydro-1,3-benzothiazole-6-sul-
fonate (5b). Yield 1.76 g (68%), colorless crystals,
mp 156–158°C (from EtOH). IR spectrum, ν, cm–1:
1409 s (SO2, asym.), 1196 s (SO2, sym.), 714 s (C–S).
1H NMR spectrum, δ, ppm: 3.68 t (3H, CH2CH3, J =
7.1 Hz), 4.06 q (2H, OCH2, J = 7.1 Hz), 7.03 d (1H,
4-H, J = 8.8 Hz), 7.64 d.d (1H, 5-H, J = 1.9, 8.8 Hz),
7.76 d (1H, 7-H, J = 1.9 Hz), 9.19 s (1H, NH). Mass
spectrum: m/z 259 (Irel 51%) [M]+. Found, %: C 41.42;
H 3.39; N 5.26; S 24.49. C9H9NO4S2. Calculated, %:
C 41.69; H 3.47; N 5.40; S 24.71.
3-Methyl-6-(piperidin-1-ylsulfonyl)-1,3-benzo-
thiazol-2(3H)-one (4g). Yield 2.09 g (67%), colorless
crystals, mp 201–203°C (from EtOH–H2O). IR spec-
trum, ν, cm–1: 1346 s (SO2, asym.), 1166 s (SO2, sym.),
Methyl 3-methyl-2-oxo-2,3-dihydro-1,3-benzo-
thiazole-6-sulfonate (5c). Yield 1.65 g (64%), color-
less crystals, mp 142–144°C (from EtOH–H2O). IR
spectrum, ν, cm–1: 1402 s (SO2, asym.), 1215 s (SO2,
asym.), 718 s (C–S). 1H NMR spectrum, δ, ppm: 3.46 s
(3H, 3-CH3), 3.71 s (3H, OCH3), 7.09 d (1H, 4-H, J =
8.7 Hz), 7.59 d.d (1H, 5-H, J = 1.7, 8.7 Hz), 7.76 d
(1H, 7-H, J = 1.7 Hz). Mass spectrum: m/z 259
(Irel 29%) [M]+. Found, %: C 41.39; H 3.35; N 5.56;
S 24.38. C9H9NO4S2. Calculated, %: C 41.69; H 3.47;
N 5.40; S 24.71.
1
747 s (C–S). H NMR spectrum, δ, ppm: 2.46–2.51 m
(2H, 4′-H), 2.85 t (4H, 3′-H, 5′-H, J = 6.9 Hz), 3.39 s
(3H, 3-CH3), 3.61 t (4H, 2′-H, 6′-H, J = 6.9 Hz), 7.06 d
(1H, 4-H, J = 8.9 Hz), 7.71 d.d (1H, 5-H, J = 1.7,
8.6 Hz), 7.79 d (1H, 7-H, J = 1.7 Hz). Mass spectrum:
m/z 312 (Irel 100%) [M]+. Found, %: C 49.81; H 5.02;
N 9.15; S 20.28. C13H16N2O3S2. Calculated, %:
C 50.02; H 5.13; N 8.97; S 20.51.
3-Methyl-6-(morpholin-4-ylsulfonyl)-1,3-benzo-
thiazol-2(3H)-one (4h). Yield 2.01 g (64%), colorless
crystals, mp 227–229°C (from EtOH–H2O). IR spec-
trum, ν, cm–1: 1353 s (SO2, sym.), 1152 s (SO2, sym.),
Ethyl 3-methyl-2-oxo-2,3-dihydro-1,3-benzothia-
zole-6-sulfonate (5d). Yield 1.80 g (66%), colorless
crystals, mp 129–131°C (from EtOH–H2O). IR spec-
trum, ν, cm–1: 1405 s (SO2, asym.), 1207 s (SO2, sym.),
1
753 s (C–S). H NMR spectrum, δ, ppm: 2.86 t (4H,
CH2OCH2, J = 8.0 Hz), 3.39 s (3H, 3-CH3), 3.59 t (4H,
CH2NCH2, J = 8.0 Hz), 7.04 d (1H, 4-H, J = 8.6 Hz),
7.65 d.d (1H, 5-H, J = 1.8, 8.6 Hz), 7.76 d (1H, 7-H,
J = 1.8 Hz). Mass spectrum: m/z 314 (Irel 47%) [M]+.
Found, %: C 45.57; H 4.33; N 8.65; S 20.12.
C12H14N2O4S2. Calculated, %: C 45.85; H 4.45;
N 8.91; S 20.38.
1
716 s (C–S). H NMR spectrum, δ, ppm: 3.45 s (3H,
3-CH3). 3.70 t (3H, CH2CH3, J = 7.1 Hz), 4.08 q (2H,
OCH2, J = 7.1), 7.08 d (1H, 4-H, J = 8.9 Hz), 7.62 d.d
(1H, 5-H, J = 1.8, 8.9 Hz), 7.81 d (1H, 7-H, J =
1.8 Hz). Mass spectrum: m/z 273 (Irel 32%) [M]+.
Found, %: C 43.77; H 3.94; N 4.88; S 23.25.
C10H11NO4S2. Calculated, %: C 43.95; H 4.03; N 5.12;
S 23.44.
Sulfonic acid esters 5a–5d (general procedure).
A solution of 10 mmol of methanol or ethanol and
1.01 g (10 mmol) of triethylamine in 10 mL of acetone
was added dropwise to a solution of 10 mmol of
compound 2 in 20 mL of acetone. The mixture was
stirred at room temperature for 2 h, the solvent was
distilled off, and the residue was treated with 100 mL
of water. The precipitate of 5a–5d was filtered off and
purified by recrystallization.
CONFLICT OF INTEREST
The authors declare the absence of conflict of interest.
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