Aryldithiocarbamates as thiol alternatives in Cu-catalyzed C(aryl)-S coupling reactions using aryldiazonium tetrafluoroborate salts

Article abstract of DOI:10.1039/c9ob01976f

An efficient method for the synthesis of unsymmetrical diaryl sulfides has been developed by the C-S cross coupling of aryldithiocarbamates and aryldiazonium salts in the presence of CuI-2,2′-bipyridine and Zn. Aryldithiocarbamate compounds have been used here as thiol substitutes. The protocol shows wide substrate scope and good yields of the products.

Full text of DOI:10.1039/c9ob01976f

Organic &
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Aryldithiocarbamates as thiol alternatives in
Cu-catalyzed C(aryl)–S coupling reactions
using aryldiazonium tetrafluoroborate salts†
Cite this: Org. Biomol. Chem., 2019,
17, 9360
Soumya Dutta and Amit Saha
*
Received 10th September 2019,
Accepted 8th October 2019
An efficient method for the synthesis of unsymmetrical diaryl sulfides has been developed by the C–S
cross coupling of aryldithiocarbamates and aryldiazonium salts in the presence of CuI-2,2’-bipyridine and
Zn. Aryldithiocarbamate compounds have been used here as thiol substitutes. The protocol shows wide
substrate scope and good yields of the products.
DOI: 10.1039/c9ob01976f
rsc.li/obc
presence of 120 mol% of Cu(OAc)2. They have also synthesized
biarylsulfides by the cross-coupling reactions of aryldithiocar-
Introduction
Dithiocarbamate compounds are valuable due to their prevalent bamates and aryl iodides18 as electrophilic aryl donors in the
applications in agricultural chemistry,1 medicinal chemistry,2 presence of NiCl2 catalyst, bipyridine ligand and an excess of
solid phase organic synthesis3 and in the development of mole- Zn (200 mol%) as the reducing agent. In our current study, we
cular electronic devices.4 Dithiocarbamate structural motifs are have employed a reactive and easily available electrophilic aryl
found in many biologically active compounds.5 Recently organic donor, such as aryl diazonium tetrafluoroborate salts for the
dithiocarbamates have become popular as useful synthetic preparation of unsymmetrical biaryl sulfides using aryldithio-
intermediates in organic syntheses.6 Earlier, we have reported carbamates as the thiol surrogates. Various aryldithiocarb-
the use of dithiocarbamate intermediates to prepare unsymme- amates were allowed to undergo cross-coupling reactions
trical thioureas7 and mixed disulfide compounds.8 As a part of with aryl diazonium tetrafluoroborate salts in the presence of
our ongoing research to explore the synthetic utility of dithiocar- the CuI-2,2′-bipyridine (bpy) catalytic system and Zn powder
bamates, here we have employed aryldithiocarbamate com- (Scheme 1).
pounds as thiol transferring agents in aryl-S cross-coupling reac-
tions to prepare unsymmetrical diaryl sulfides.
Diaryl sulfides have gained special attention due to their
occurrence in biologically and medicinally valuable organic
compounds9 (Fig. 1). The classical method for the synthesis of
unsymmetrical thioethers involves the use of toxic, volatile
and foul smelling thiols. Organic disulfides,10 N-(thio)succin-
imides/phthalimides,11 thioureas,12 thioacetamides,13 sulfonyl
hydrazides,14 sulfoxides,15 and sodium arylthiolate16 are the
popular thiol alternatives which have been used in the syn-
thesis of biaryl sulfides. However, the potential of dithiocarba-
mate compounds as thiol donors is not studied exhaustively.
To the best of our knowledge, there are only two reports for
the use of dithiocarbamate compounds as thiol substitutes in
the synthesis of biaryl sulfides. Dong and co-workers accom-
Fig. 1 Biologically active organic molecules containing the biaryl
sulfide framework.
plished the synthesis of biaryl sulfides by oxidative coupling of
arylboronic acids with dithiocarbamate compounds17 in the
Department of Chemistry, Jadavpur University, Kolkata 700032, India.
E-mail: amit.saha@jadavpuruniversity.in
†Electronic supplementary information (ESI) available: NMR and HRMS spectra.
Scheme 1 Synthesis of diaryl sulfides using aryl diazonium salts and
See DOI: 10.1039/c9ob01976f
dithiocarbamates as sulfur sources.
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(10 mol%) and 2,2′-bipyridine ligand (20 mol%) along with
0.3 equiv. of Zn powder to give the product 3d in 85% yield
Results and discussion
The reactions are very easy to perform.
A
mixture of (entry 12, Table 1). Other ligands such as L-proline, ethylene-
S-aryldithiocarbamate and aryldiazonium tetrafluoroborate in diamine (en), 1,10-phenantholine (1,10-phen) and N,N′-di-
DMF was stirred at 120 °C in the presence of CuI (10 mol%), methylethylenediamine (DMEDA) (entries 10, 11, 13 and 14,
2,2′-bipyridine (20 mol%) and Zn powder (30 mol%) for a Table 1) were not effective to produce the desired product sat-
certain time period. After completion of the reaction (checked isfactorily. The reaction did not give a satisfactory result in the
by TLC), the product was obtained by usual work-up and puri- presence of other copper catalysts such as Cu(OAc)2, CuCl,
fied by column chromatography.
CuBr, CuSO4 and Cu powder (entries 16–20, Table 1). The
To standardize the reaction conditions, phenyldithiocarba- product, 3d was obtained only in trace amounts in the pres-
mate (1a) and 4-methoxyphenyl diazonium tetrafluoroborate ence of iron powder as the additive (entry 8, Table 1). Lowering
(2d) were allowed to undergo a cross-coupling reaction under the reaction temperature (80 °C) decreases the yield of
the various reaction conditions (Table 1). The reaction of 1a the product to 60% (entry 21, Table 1). Allowing 3 h of
and 2d was tried in DMSO solvent at 120 °C (entry 1, Table 1) reaction time period causes the reaction to remain incomplete
in the presence of 20 mol% of CuI and 0.5 equiv. of Zn powder (entry 22, Table 1). The crucial roles of CuI and Zn were rea-
and we observed the formation of the desired biaryl sulfide lized by the blank experiments. The reaction was found to be
(3d) in 38% yield. The reaction did not proceed at all in arrested either in the absence of Zn powder (entry 23, Table 1)
dioxane (entry 3, Table 1), THF (entry 4, Table 1), MeCN (entry or in the absence of CuI (entry 24, Table 1). The yield of the
5, Table 1) and water (entry 15, Table 1). In DMF solvent (entry product did not boost up at a higher reaction temperature and
7, Table 1) the reaction proceeds to produce the desired under a prolonged reaction time period.
product (3d) with a much better yield (64%) in comparison
The scope of the reaction was established by carrying out
with other solvents, like NMP (entry 2, Table 1) and DMAc the reaction with a variety of substrates under the optimized
(entry 6, Table 1). Upon using the triphenylphosphine ligand reaction conditions (entry 12, Table 1). Phenyldithiocarbamate
(40 mol%) along with 10 mol% of CuI, the yield of the reaction (1a) was subjected to undergo cross-coupling reactions with
improved significantly (78%) (entry 9, Table 1). However, different substituted aryldiazonium tetrafluoroborate salts (2)
the optimum reaction condition was achieved by using CuI (Table 2).
Table 1 Optimization of the reaction conditionsa
Entry
Solvent
Catalyst (mol%)
Ligand (mol%)
Additive (equiv.)
Temp (°C)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
DMSO
NMP
Dioxane
THF
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (20)
CuI (10)
CuI (10)
CuI (10)
CuI (10)
CuI (10)
CuI (10)
CuI (10)
Cu(OAc)2 (10)
CuCl (10)
CuBr (10)
CuSO4 (10)
Cu powder (10)
CuI (10)
CuI (10)
CuI (10)
—
—
—
—
—
—
—
—
—
Zn (0.5)
Zn (0.5)
Zn (0.5)
Zn (0.5)
Zn (0.5)
Zn (0.5)
Zn (0.5)
Fe (0.5)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
Zn (0.3)
—
120
120
100
66
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
3
5
5
38
58
NR
NR
NR
60
64
Trace
78
Trace
Trace
85
MeCN
DMAc
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
H2O
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
82
120
120
120
120
120
120
120
120
120
100
120
120
120
120
120
80
9
PPh3 (40)
L-Proline (20)
en (20)
bpy (20)
1,10-Phen (20)
DMEDA (20)
bpy (20)
bpy (20)
bpy (20)
bpy (20)
bpy (20)
bpy (20)
bpy (20)
bpy (20)
bpy (20)
—
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
23
Trace
NR
61
20
43
Trace
30
60
37
Trace
NR
120
120
120
Zn (0.3)
a Reaction condition: The mixture of 1a (1 mmol, 197 mg) and 2d (1.2 mmol, 266 mg) in 3 ml of solvent was heated in the presence of the cata-
lyst, ligand and additive under an argon atmosphere.
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Table 2 Substrate scope for the synthesis of diaryl sulfides from
various aryldiazonium fluoroborate saltsa
Table 3 Substrate scope with substituted aryl dithiocarbamatesa
a Reaction condition: The mixture of 1a (1 mmol) and 2 (1.2 mmol) in
3 ml of DMF was heated at 120 °C in the presence of CuI (10 mol%),
bpy (20 mol%) and Zn powder (0.3 equiv.) under an argon atmosphere.
Yields mentioned are isolated yields.
a Reaction condition: The mixture of 1 (1 mmol) and 2 (1.2 mmol) in
3 ml of DMF was heated at 120 °C in the presence of CuI (10 mol%),
bpy (20 mol%) and Zn powder (0.3 equiv.) under an argon atmosphere.
Yields mentioned are isolated yields.
Electron donating groups, such as Me and OMe, and elec-
tron withdrawing groups, such as F, Cl, Br, NO2, and CO2Et
were tolerable under the reaction conditions. The reaction
shows good chemoselectivity in the case of 4-bromophenyl dia-
zonium salt and 4-chlorophenyl diazonium salt producing
exclusively the biaryl sulfides (3g and 3f respectively) with 4-Br
and 4-Cl groups unaffected. The sterically hindered diazonium
cation with two ortho-Me substituents underwent C–S cross
coupling with 1a smoothly to provide the desired diaryl sulfide
(3j) in good yield (78%). Next we explored our reaction protocol
with several structurally variable aryldithiocarbamates (1)
(Table 3). Aryldithiocarbamates containing substituents, such
as 4-Cl, 4-NO2, 3-NO2, and 4-OMe underwent C–S bond for-
mation efficiently with different aryldiazonium tetrafluoro-
borate salts (2).
Scheme 2 Synthesis of biaryl sulfides from two different aryldiazonium
salts.
Aryldithiocarbamate compounds (1) were prepared by the
three component reactions of the corresponding aryldiazo-
nium tetrafluoroborate salts19 (1′) with dimethylamine and CS2
(Scheme 2). Thus, the biaryl sulfide (3) can be obtained
starting from two different aryldiazonium salts (1′ and 2)
(Scheme 2).
Aryldiazonium cations are well known to undergo various
cross-coupling reactions via the generation of aryl radical20
intermediates. However, the use of
a radical quencher,
TEMPO, in excess amount (2 equiv.), did not have any adver-
sarial effect on the cross coupling reaction of p-methoxyphe-
nyldiazonium cation (2d) with phenyldithiocarbamate (1a) and
the yield of the reaction remained unaltered. Thus, the possi-
bility of a radical pathway in our present protocol was ruled
out. We believe that the reaction proceeds through an oxidative
addition-reductive elimination type mechanism as shown in
Scheme 3. At first, CuI gets reduced to Cu(0) by Zn. Now Cu(0)
undergoes oxidative addition to aryldiazonium tetrafluoro- Scheme 3 Proposed mechanistic pathway.
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borate (2)21 to generate the arylazo-Cu(II) complex (A). After the 0–5 °C. After stirring for 5 minutes aryl diazonium tetrafluoro-
expulsion of dinitrogen from complex A, a cationic arylcopper borate (1 mmol) was added portion wise under cold conditions
complex (B)22 is formed. The arydithiocarbamate (1) now and the reaction mixture was stirred at room temperature
reacts with complex B to produce intermediate C and Me2NC (25 °C) for 3 h (monitored by TLC). After completion of the
(S)F (4). The generation of Me2NC(S)F (4) was detected by reaction, the crude product was obtained by the usual work up
HRMS analysis (characteristic signal calculated for C3H6FNSNa procedure using an EtOAc–water mixture. The crude product
[M + 23]+ = 130.0103, found = 130.0437) of a crude reaction was further purified by column chromatography using an
mixture obtained from the reaction between 1a and 2d for 1 h EtOAc–hexane solvent mixture to afford the desired compound 1.
of reaction time period. Intermediate C undergoes reductive 1H spectra of all synthesized S-aryldithiocarbamates (1a–1e)
elimination to provide the desired diaryl sulfide (3) product.
are included in the ESI.†
General procedure for the synthesis of aryldiazonium
tetrafluoroborates (2)23
Conclusions
5 mmol of aromatic amine was dissolved in a 1 : 1 mixture of
concentrated HCl (40 mmol, 1.23 mL) and water (1.23 mL).
The resulting solution was stirred for 5 minutes and then
cooled to 0–5 °C in an ice bath. To it a cold solution of
NaNO2 (5.4 mmol) in 1 mL of water was added dropwise with
vigorous stirring and the temperature was maintained at 5 °C
by adding crushed ice, if necessary. After 5 minutes of con-
tinuous stirring a chilled solution of sodium tetrafluoro-
borate (7 mmol) in 1.5 mL of water was added dropwise
under 0–5 °C and allowed to stand for 10 minutes with fre-
quent stirring. The precipitated diazonium salt was filtered
with suction on a Buchner funnel, drained well, and washed
with 1 mL of ice water, 1 mL of methanol and 2 mL of ether.
The desired product was dried well in vacuo and stored
below −10 °C.
In conclusion, a general and convenient synthesis route of
diaryl sulfides has been demonstrated. Aryldithiocarbamates
were efficiently coupled with aryldiazonium salts. Starting
from two different aryldiazonium salts the unsymmetrical
diaryl sulfide can be prepared very easily by this protocol.
Broad substrate scope, good yields of the products and easy
availability of the starting materials render the method syn-
thetically useful.
Experimental section
General information
Unless otherwise stated, all commercial reagents were pur-
chased from commercial suppliers and used without further
purification. All reactions were performed in an oven-dried
round bottom flask (10 mL) with a Teflon coated magnetic
stirring bar at 120 °C under an argon atmosphere. Solvents
were dried using standard methods and distilled before use.
Reactions were monitored by thin layer chromatography (TLC)
on silica gel plates (Merck silica gel 60, GF254) and the spots
were visualized with UV light (254). The crude product was
purified by column chromatography on Merck silica gel
(60–120 mesh). 1H NMR spectra were recorded at 300 MHz
(Bruker-DPX) and 400 MHz (Bruker Avance III) and 13C NMR
spectra were recorded at 75 MHz (Bruker-DPX) and 100 MHz
(Bruker Avance III) frequency in a deuterated solvent (CDCl3)
using TMS as the internal standard. Chemical shifts were
measured in parts per million (ppm) referenced to 0.0 ppm for
tetramethylsilane. NMR data are reported as follows: chemical
shift, multiplicity (s = singlet, d = doublet, t = triplet, q =
quartet, m = multiplet, br. = broad). Coupling constants J were
reported in hertz unit (Hz). High-resolution mass spectra
(HRMS) were recorded in methanol solvent on a Waters
MicromassQtofMicromass spectrometer using the electrospray
ionization method. Melting points were determined by using
LabX India digital melting point apparatus.
General procedure for the synthesis of diarylsulfide
compounds (3a–3y) as exemplified for 3d
A mixture of phenyl dimethylcarbamodithioate 1a (1 mmol,
197 mg), p-methoxyphenyldiazonium tetrafluoroborate 2d
(1.2 mmol, 266 mg), CuI (0.1 mmol, 20 mg), bipyridine
(0.2 mmol, 31.5 mg) and zinc (0.3 mmol, 20 mg) in DMF
(3 mL) was stirred at 120 °C (silicon oil bath) for 5 h (moni-
tored by TLC) under an argon atmosphere. After completion of
the reaction, the crude product was obtained by the usual
work-up procedure using EtOAc and the crude was further pur-
ified by column chromatography using the EtOAc–hexane
solvent mixture to afford the desired product 3d as a yellow oil
(183 mg, 85% yield).
All the synthesized known compounds are characterized by
1H NMR and 13C NMR spectra and the unknown compounds
are characterized by 1H NMR, 13C NMR spectra and HRMS.
Characterization data of synthesized compounds
Diphenylsulfide24 (Table 2, 3a). Yellow oil (148 mg, 5 h, 80%
yield); Rf −0.6 (in hexane); purified by column chromatography
using (EtOAc/hexane = 1/9, v/v). 1H NMR (CDCl3, 400 MHz)
δ 7.38–7.21 (m, 10H) ppm. 13C NMR (CDCl3, 100 MHz)
δ 135.79, 131.05, 129.22, 127.17 ppm.
General procedure for the synthesis of S-aryl
Phenyl(o-tolyl)sulfide18 (Table 2, 3b). Yellow oil (168 mg,
6 h, 84% yield); Rf −0.5 (in hexane); purified by column chrom-
dithiocarbamates (1)19
To a stirred solution of carbon disulfide (2.5 mmol) in water atography using (EtOAc/hexane = 1/9, v/v). 1H NMR (CDCl3,
(2 mL) dimethyl amine was added (1.2 mmol) dropwise at 400 MHz) δ 7.26–7.06 (m, 9H), 2.30 (s, 3H) ppm. 13C NMR
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(CDCl3, 100 MHz) δ 140.13, 136.34, 133.91, 133.17, 130.73,
129.77, 129.19, 128.04, 126.84, 126.46 ppm.
Ethyl 4-(phenylthio)benzoate10e (Table 2, 3k). Colourless oil
(216 mg, 5 h, 84% yield); Rf −0.32 (in 2% EtOAc–hexane); puri-
Phenyl(p-tolyl)sulfide24 (Table 2, 3c). Yellow oil (164 mg, fied by column chromatography using (EtOAc/hexane = 2/8,
6 h, 82% yield); Rf −0.64 (in hexane); purified by column v/v). 1H NMR (CDCl3, 400 MHz) δ 7.81 (d, J = 8 Hz, 2H),
chromatography using (EtOAc/hexane = 1/9, v/v). 1H NMR 7.39–7.27 (m, 5H), 7.11 (d, J = 8 Hz, 2H), 4.27 (q, J = 8 Hz, 2H),
(CDCl3, 400 MHz) δ 7.32–7.10 (m, 9H), 2.30 (s, 3H) ppm. 1.27 (t, J = 8 Hz, 3H), 1.61 (s, 6H) ppm. 13C NMR (CDCl3,
13C NMR (CDCl3, 100 MHz) δ 137.59, 137.18, 132.40, 131.33, 100 MHz) δ 166.20, 144.16, 133.61, 132.83, 130.12, 129.66,
130.19, 129.97, 129.17, 126.55, 21.14 ppm.
128.62, 127.98, 127.75, 60.96, 14.38 ppm.
(4-Methoxyphenyl)(phenyl)sulfide24 (Table 2, 3d). Yellow oil
(4-Bromophenyl)(4-chlorophenyl)sulfide27 (Table 3, 3l).
(183 mg, 5 h, 85% yield); Rf −0.54 (in hexane); purified by Colourless oil (242 mg, 5 h, 81% yield); Rf −0.64 (in hexane);
column chromatography using (EtOAc/hexane = 1/9, v/v). purified by column chromatography using (EtOAc/hexane =
1
1H NMR (CDCl3, 400 MHz) δ 7.42 (d, J = 8 Hz, 2H), 7.24 1/9, v/v). H NMR (CDCl3, 400 MHz) δ 7.42 (d, J = 8 Hz, 2H),
(t, J = 8 Hz, 2H), 7.18–7.12 (m, 3H), 6.90 (d, J = 8 Hz, 2H), 7.28–7.26 (m, 4H), 7.18 (d, J = 8 Hz, 2H) ppm. 13C NMR (CDCl3,
3.82 (s, 3H) ppm. 13C NMR (CDCl3, 100 MHz) δ 160.00, 100 MHz) δ 134.96, 133.85, 132.57, 132.48, 132.40, 129.59,
138.74, 135.47, 129.07, 128.42, 125.93, 124.55, 115.15, 129.38, 121.49 ppm.
55.51 ppm.
(4-Chlorophenyl)(4-methoxyphenyl)sulfide28 (Table 3, 3m).
(4-Fluorophenyl)(phenyl)sulfide24 (Table 2, 3e). Colourless White solid (212 mg, 6 h, 85% yield); Rf −0.54 (in hexane); pur-
oil (173 mg, 5 h, 85% yield); Rf −0.52 (in hexane); purified by ified by column chromatography using (EtOAc/hexane = 1/9,
column chromatography using (EtOAc/hexane = 1/9, v/v). v/v); melting point: 64–66 °C. 1H NMR (CDCl3, 500 MHz) δ 7.41
1H NMR (CDCl3, 400 MHz) δ 7.51(d, J = 8 Hz, 2H), 7.30–7.22 (d, J = 8.8 Hz, 2H), 7.19 (d, J = 8.6 Hz, 2H), 7.08 (d, J = 8.6 Hz,
(m, 5H), 7.03–7.00 (m, 2H) ppm. 13C NMR (CDCl3, 100 MHz) 2H), 6.91 (d, J = 8.8 Hz, 2H), 3.82 (s, 3H) ppm. 13C NMR
δ 163.74, 161.27, 136.76, 134.24, 134.16, 130.08, 129.30, (CDCl3, 125 MHz) δ 160.16, 137.50, 135.60, 131.68, 129.40,
126.88, 116.63, 116.41 ppm.
129.10, 123.83, 115.23, 55.46 ppm.
(4-Chlorophenyl)(phenyl)sulfide18 (Table 2, 3f). Yellow oil
(4-Chlorophenyl)(p-tolyl)sulfide28 (Table 3, 3n). White solid
(180 mg, 5 h, 82% yield); Rf −0.64 (in hexane); purified by (196 mg, 6 h, 84% yield); Rf −0.66 (in hexane); purified by
column chromatography using (EtOAc/hexane = 1/9, v/v). column chromatography using (EtOAc/hexane = 1/9, v/v);
1H NMR (CDCl3, 300 MHz) δ 7.35–7.29 (m, 5H), 7.27–7.21 (m, melting point: 70–72 °C. 1H NMR (CDCl3, 400 MHz)
4H) ppm. 13C NMR (CDCl3, 100 MHz) δ 135.27, 134.80, 133.15, δ 7.35–7.29 (m, 4H), 7.24–7.17 (m, 4H), 2.39 (s, 3H) ppm.
132.16, 131.47, 129.48, 129.45, 127.30 ppm.
(4-Bromophenyl)(phenyl)sulfide17 (Table 2, 3g). Colourless 130.95, 130.33, 129.45, 129.28, 21.27 ppm.
13C NMR (CDCl3, 100 MHz) δ 138.03, 136.23, 132.67, 132.51,
oil (232 mg, 5 h, 88% yield); Rf −0.68 (in hexane); purified by
Bis(4-chlorophenyl)sulfide29 (Table 3, 3o). White solid
column chromatography using (EtOAc/hexane = 1/9, v/v). (209 mg, 5 h, 82% yield); Rf −0.64 (in hexane); purified by
1H NMR (CDCl3, 300 MHz) δ 7.44–7.18 (m, 7H), 7.04 (d, J = column chromatography using (EtOAc/hexane = 1/9, v/v);
9 Hz, 2H) ppm. 13C NMR (CDCl3, 75 MHz) δ 135.61, 134.94, melting point: 94–96 °C. 1H NMR (CDCl3, 400 MHz)
132.34, 132.19, 131.67, 129.49, 127.67, 120.98 ppm.
(3-Nitrophenyl)(phenyl)sulfide24 (Table 2, 3h). Yellow solid 100 MHz) δ 134.22, 133.72, 132.46, 129.64 ppm.
δ 7.33–7.30 (m, 4H), 7.28–7.26 (m, 4H) ppm. 13C NMR (CDCl3,
(180 mg, 5 h, 78% yield); Rf −0.48 (in hexane); purified by
(4-Chlorophenyl)(2,6-dimethylphenyl)sulfide (Table 3, 3p).
column chromatography using (EtOAc/hexane = 1/9, v/v); Colourless oil (200 mg, 6 h, 81% yield); Rf −0.58 (in hexane);
melting point: 92 °C. 1H NMR (CDCl3, 300 MHz) δ 8.03–8.01 purified by column chromatography using (EtOAc/hexane =
(m, 2H), 7.48–7.26 (m, 7H) ppm. 13C NMR (CDCl3, 75 MHz) 1/9, v/v). 1H NMR (CDCl3, 400 MHz) δ 7.42–7.40 (m, 1H),
δ 148.79, 140.67, 134.34, 133.52, 132.21, 129.95, 129.77, 7.29–7.23 (m, 2H), 7.19 (d, J = 8 Hz, 2H), 7.17 (d, J = 8 Hz, 2H),
129.04, 123.23, 121.00 ppm.
(4-Nitrophenyl)(phenyl)sulfide25 (Table 2, 3i). Yellow solid 130.56, 129.59, 129.38, 129.09, 128.67, 126.93, 21.87 ppm.
2.44 (s, 6H) ppm. 13C NMR (CDCl3, 100 MHz) δ 143.88, 136.79,
(187 mg, 5 h, 81% yield); Rf −0.46 (in hexane); purified by HRMS: calcd for
C14H13ClS [M +
H]+ 249.0426; found
column chromatography using (EtOAc/hexane = 1/9, v/v); 249.1790.
1
melting point: 56 °C. H NMR (CDCl3, 400 MHz) δ 8.06 (d, J =
(4-Chlorophenyl)(naphthalen-1-yl)sulfide24 (Table 3, 3q).
8 Hz, 2H), 7.55–7.53 (m, 2H), 7.46–7.45 (m, 3H), 7.18 (d, J = Yellow oil (221 mg, 6 h, 82% yield); Rf −0.54 (in hexane); puri-
8 Hz, 2H) ppm. 13C NMR (CDCl3, 100 MHz) δ 148.60, 145.57, fied by column chromatography using (EtOAc/hexane = 1/9,
1
134.87, 130.68, 130.17, 129.79, 126.90, 124.18 ppm.
v/v). H NMR (CDCl3, 400 MHz) δ 8.38–8.36 (m, 1H), 7.80 (d,
(2,6-Dimethylphenyl)(phenyl)sulfide26 (Table 2, 3j). Yellow J = 8 Hz, 2H), 7.72 (d, J = 4 Hz, 1H), 7.56–7.54 (m, 2H),
oil (166 mg, 6 h, 78% yield); Rf −0.40 (in hexane); purified by 7.47–7.41 (m, 1H), 7.19 (d, J = 8 Hz, 2H), 7.11 (d, J = 8 Hz, 2H)
column chromatography using (EtOAc/hexane = 1/9, v/v). ppm. 13C NMR (CDCl3, 100 MHz) δ 135.89, 134.44, 133.69,
1H NMR (CDCl3, 400 MHz) δ 7.36–7.22 (m, 5H), 7.09 (d, J = 133.15, 132.09, 130.64, 130.01, 129.79, 129.29, 128.77, 127.25,
8 Hz, 1H), 6.97 (d, J = 8 Hz, 2H), 2.47 (s, 6H) ppm. 13C NMR 126.66, 125.95, 125.64 ppm.
(CDCl3, 100 MHz) δ 144.04, 138.19, 130.69, 129.38, 129.03,
128.58, 125.84, 124.77, 21.96 ppm.
(4-Chlorophenyl)(4-nitrophenyl)sulfide30 (Table 3, 3r). Yellow
solid (198 mg, 5 h, 75% yield); Rf −0.36 (in 2% EtOAc–hexane);
9364 | Org. Biomol. Chem., 2019, 17, 9360–9366
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purified by column chromatography using (EtOAc/hexane = 2H), 3.82 (s, 3H), 2.30 (s, 3H) ppm. 13C NMR (CDCl3, 100 MHz)
1
2/8, v/v); melting point: 58–60 °C. H NMR (CDCl3, 400 MHz) δ 159.87, 138.87, 138.34, 135.30, 129.11, 128.95, 126.90,
δ 8.07 (d, J = 8 Hz, 2H), 7.47–7.40 (m, 4H), 7.18 (d, J = 8 Hz, 2H) 125.63, 124.72, 115.08, 55.45, 21.47 ppm.
ppm. 13C NMR (CDCl3, 100 MHz) δ 147.64, 145.76, 136.13,
135.89, 130.36, 129.34, 127.12, 124.24 ppm.
(4-Chlorophenyl)(3-nitrophenyl)sulfide31 (Table 3, 3s). Conflicts of interest
Yellow oil (204 mg, 5 h, 77% yield); Rf −0.38 (in 2% EtOAc–
There are no conflicts to declare.
hexane); purified by column chromatography using (EtOAc/
1
hexane = 2/8, v/v). H NMR (CDCl3, 400 MHz) δ 8.05–8.03 (m,
2H), 7.58–7.51 (m, 1H), 7.47–7.37 (m, 5H) ppm. 13C NMR
Acknowledgements
(CDCl3, 100 MHz) δ 148.80, 139.79, 135.21, 134.65, 134.47,
131.05, 130.10, 129.95, 123.55, 121.39 ppm.
Soumya Dutta thanks CSIR, India for his fellowship (JRF). We
acknowledge the financial support from UGC-BSR Start-up-
grant (FD Diary No.4855; Dated: 24.09.2018). We also would
like to acknowledge UGC-CAS program in Chemistry, Jadavpur
(4-Fluorophenyl)(4-methoxyphenyl)sulfide32 (Table 3, 3t).
Yellow oil (191 mg, 6 h, 82% yield); Rf −0.46 (in 2% EtOAc–
hexane); purified by column chromatography using (EtOAc/
hexane = 1/9, v/v). 1H NMR (CDCl3, 400 MHz) δ 7.40 (d, J =
University and the DST-PURSE Program at Jadavpur University.
8 Hz, 2H), 7.26–7.22 (m, 2H), 7.01–6.96 (m, 2H), 6.91 (d, J =
8 Hz, 2H), 3.84 (s, 3H) ppm. 13C NMR (CDCl3, 100 MHz)
δ 162.96, 160.51, 159.82, 134.59, 133.24, 132.75, 131.25,
Notes and references
131.17, 125.43, 116.27, 116.05, 115.13, 55.45 ppm.
Bis(4-methoxyphenyl)sulfide33 (Table 3, 3u). Colourless oil
(198 mg, 5 h, 81% yield); Rf −0.48 (in 5% EtOAc–hexane); puri-
fied by column chromatography using (EtOAc/hexane = 2/8,
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v/v). H NMR (CDCl3, 300 MHz) δ 7.31–7.28 (m, 4H), 6.86–6.83
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(4-Methoxyphenyl)(3-nitrophenyl)sulfide34 (Table 3, 3v).
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hexane = 2/8, v/v). 1H NMR (CDCl3, 400 MHz) δ 7.90–7.87
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8 Hz, 2H), 3.82 (s, 3H) ppm. 13C NMR (CDCl3, 100 MHz)
δ 160.02, 142.71, 136.74, 132.44, 129.57, 123.54, 121.29, 120.12,
115.66, 114.72, 55.43 ppm.
(2,6-Dimethylphenyl)(4-methoxyphenyl)sulfide35 (Table 3,
3w). White solid (198 mg, 6 h, 81% yield); Rf −0.22 (in 2%
EtOAc–hexane); purified by column chromatography using
(EtOAc/hexane = 2/8, v/v), melting point: 52 °C. 1H NMR
(CDCl3, 100 MHz) δ 7.24–7.19 (m, 3H), 6.98 (d, J = 8 Hz, 2H),
6.80 (d, J = 8 Hz, 2H), 3.77 (s, 3H), 2.50 (s, 6H) ppm. 13C NMR
(CDCl3, 100 MHz) δ 157.69, 143.65, 132.07, 129.08, 128.76,
128.56, 128.11, 114.84, 55.40, 22.11 ppm.
Ethyl 4-((4-methoxyphenyl)thio)benzoate36 (Table 3, 3x).
Yellow oil (236 mg, 5 h, 82% yield); Rf −0.42 (in 5% EtOAc–
hexane); purified by column chromatography using (EtOAc/
hexane = 2/8, v/v). 1H NMR (CDCl3, 300 MHz) δ 7.83 (d, J =
9 Hz, 2H), 7.41 (d, J = 9 Hz, 2H), 7.01 (d, J = 9 Hz, 2H), 6.85 (d,
J = 9 Hz, 2H), 4.28 (q, J = 6 Hz, 2H), 3.78 (s, 3H), 1.27 (t, J =
6 Hz, 3H) ppm. 13C NMR (CDCl3, 75 MHz) δ 165.91, 159.31,
146.25, 137.15, 130.52, 127.95, 126.20, 122.02, 114.55, 61.31,
55.39, 14.61 ppm.
(4-Methoxyphenyl)(m-tolyl)sulfide30 (Table 3, 3y). Yellow oil
(195 mg, 6 h, 85% yield); Rf −0.58 (in 2% EtOAc–hexane); puri-
fied by column chromatography using (EtOAc/hexane = 1/9,
v/v). 1H NMR (CDCl3, 400 MHz) δ 7.45–7.42 (m, 2H), 7.15 (t, J =
8 Hz, 1H), 7.06 (s, 1H), 7.02–6.97 (m, 2H), 6.91 (d, J = 8 Hz,
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