Nano-CuFe2O4 as a magnetically separable and reusable catalyst for the synthesis of diaryl/aryl alkyl sulfides via cross-coupling process under ligand-free conditions

Article abstract of DOI:10.1039/c1ob05597f

An efficient protocol was developed for the CuFe₂O₄ nanopowder-catalyzed aryl-sulfur bond formation between aryl halide and thiol/disulfide. A variety of aryl sulfides were synthesized in impressive yields with good chemoselectivity and functional group tolerance in the presence of a catalytic amount of CuFe₂O₄, Cs₂CO ₃ as base, in nitrogen atmosphere, under ligand-free conditions, in DMSO as solvent at 100 °C. The catalyst is air-stable, inexpensive, magnetically separable and recyclable up to four cycles.

Full text of DOI:10.1039/c1ob05597f

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Nano-CuFe2O4 as a magnetically separable and reusable catalyst for the
synthesis of diaryl/aryl alkyl sulfides via cross-coupling process under
ligand-free conditions†
Kokkirala Swapna, Sabbavarapu Narayana Murthy, Mocharla Tarani Jyothi and
Yadavalli Venkata Durga Nageswar*
Received 14th April 2011, Accepted 17th May 2011
DOI: 10.1039/c1ob05597f
An efficient protocol was developed for the CuFe2O4 nanopowder-catalyzed aryl–sulfur bond formation
between aryl halide and thiol/disulfide. A variety of aryl sulfides were synthesized in impressive yields
with good chemoselectivity and functional group tolerance in the presence of a catalytic amount of
CuFe2O4, Cs2CO3 as base, in nitrogen atmosphere, under ligand-free conditions, in DMSO as solvent at
100 ◦C. The catalyst is air-stable, inexpensive, magnetically separable and recyclable up to four cycles.
salts. These systems suffer from certain limitations such as
moisture sensitive phosphine ligands, tedious synthetic procedures
etc. Recently, several transition metal-catalyzed coupling systems
Introduction
The C–S cross-coupling reaction plays a significant role in
involving nickel,10 and cobalt,11 were demonstrated for thioether
bond formation between aryl halides and thiols. Often these above
mentioned homogeneous methods have limitations of requiring
excessive use of reagents, toxic metals, and low turnover numbers.
However, further development of these classical Ullmann
coupling reactions,12 were explored by using easily available and
cheap metals like copper13 and iron,14 for the C–S bond formation
by the coupling of aryl halides with thiols. The traditional
copper-mediated C–S bond formation reactions also involve
drawbacks, such as the use of stoichiometric amounts of the
catalyst, high reaction temperatures, longer reaction times, as
well as sensitivity to functional groups on the aryl halide.5b,15
Palomo16 and co-workers reported C–S cross-coupling reactions
by using CuBr and expensive phosphazene base as ligand.
Venkataraman17 and coworkers described an efficient protocol
utilizing CuI/neocuproine in the presence of NaOtBu. Kumar
and Engman18 described a microwave-assisted copper/bipyridyl-
catalyzed preparation of diaryl sulfides by employing aryl halides
and diaryl disulfide as coupling partners in the presence of
Mg as additive. Bolm19 et al., achieved great success in C–S
cross-coupling reactions by utilizing a catalytic amount of FeCl3
in combination with DMEDA ligand. Sekar20 and coworkers
developed an efficient, mild and intermolecular Ullmann-type
synthesis of thioethers catalyzed by a diol–copper(I) complex
system.
organic synthesis and constitutes a key step in the synthesis
of many molecules that are of biological, chemical, material
or pharmaceutical interest.1 These organosulfur compounds are
used in diverse fields with various applications, such as treatment
of cancer,2 diabetes, inflammation, Alzheimer’s and Parkinson’s
diseases,3 and HIV.4 The traditional methods for C–S bond
formation were achieved under drastic reaction conditions such
as elevated reaction temperatures (>200 ◦C), with the use of
toxic and high boiling polar solvents like quinoline, HMPA
or N,N-dimethylacetamide. Alternatively, these sulfides can be
synthesized by the reduction of aryl sulfones or aryl sulfoxides
using strong reducing agents like DIBAL-H or LiAlH4.5 In today’s
chemical research arena, transition metals play a prominent role
in bringing tremendous progress in the field of organosulfur
chemistry, even though C–S cross-coupling reactions are less
explored when compared to C–N or C–O bond formation due
to the deactivation of the metal catalyst in view of the strong
coordination properties of organosulfur compounds,6 often mak-
ing the catalytic system ineffective. To overcome these difficulties,
several transition metal-catalyzed cross-coupling reactions were
developed. Migita et al. first reported that palladium catalyzed
C–S bond formation, involving the coupling between aryl halides
and thiols using Pd(PPh3)4 as catalyst.7 However, these palladium-
catalyzed reactions8 also require bidentate phosphine ligands or
diverse oxo phosphane derivatives,9 as well as high cost palladium
In recent times, several catalytic systems based on metals like
Cu,21 Cu/Fe,22 In,23 La24 and Mn25 were explored for C–S cross-
coupling reaction with aryl halides and thiols in the presence of
various ligands. However, these aforementioned protocols suffer
from one or more drawbacks such as the use of various well-
designed ligands, lack of recyclability etc. Hence, the development
Organic Chemistry Division-I, Indian Institute of Chemical Technology,
Uppal Road, Tarnaka, Hyderabad 500607, India. E-mail: dryvdnageswar@
gmail.com
† Electronic supplementary information (ESI) available: 1H NMR
and 13C NMR spectroscopic data of all the compounds. See DOI:
10.1039/c1ob05597f
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Table 1 Nano-copper ferrite-catalyzed cross-coupling of iodobenzene
of an alternative inexpensive, ligand-free, air-resistant and re-
cyclable catalyst for the formation of the thioether linkage is
highly desirable in the context of environmental and industrial
concerns. In the realm of cross-coupling reactions, metal-anchored
heterogeneous supported reagents have received paramount at-
tention in recent times in view of their advantages and improved
efficacy due to their stable active sites, better steric control of
the reaction intermediate and reusability of the catalyst.26 B. C.
Ranu27 and coworkers reported reusable heterogeneous supported
copper/Al2O3-catalyzed coupling of thiols with aryl halides under
aerobic, ligand-free conditions. Very recently, Rao et al., reported
a recyclable iron/graphite,28 catalyst for C–S cross-coupling of
thiols with aryl halides under ligand-free conditions to afford
cross-coupled products in good to excellent yields. Catalysts in
nanoscale are more advantageous due to their greater exposed
active surface area to bind the substrates selectively, making
it an effective process, allowing genuine advance in relation to
traditional methodologies.
with benzenethiola
Entry
Solvent
Base
T/◦C
Yieldb (%)
1
2
3
4
5
6
7
8
DMSO
DMSO
DMSO
DMF
1,4-dioxane
toluene
water
CH3CN
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
K3PO4
rt
80
—
70
98
71
65
70
—
45
75
80
60
55
56
55
100
100
100
100
100
100
100
100
100
100
100
100
9
10
11
12
13
14
NaOH
NaOMe
NaO-tBu
KO-tBu
30
Recently, several transition metal oxides like CuO29 and In2O3
in the form of nanoparticles were employed as recyclable catalysts
for C–S cross-coupling processes under ligand-free conditions.
In general, nanomaterials with natural morphologies containing
higher surface area as reactive sites allows them to act as effective
catalysts for organic synthesis.31 These nanoparticles have pro-
vided a simplified isolation procedure for the product, with small
amounts of catalyst, affording easy recovery and recyclability of
the catalyst. Inspired by the utilization of magnetically separable
CuFe2O4 nanoparticles as a catalyst for the C–S cross-coupling
process and as a part of our continuous interest in the field of
cross-coupling reactions,32 herein we describe for the first time
inexpensive, air-stable, magnetically separable, recyclable CuFe2O4
nanoparticle-catalyzed synthesis of diaryl thioether derivatives
from the corresponding aryl halides and benzenethiol under mild
ligand-free reaction conditions.
a Reaction conditions: 1a (1.0 mmol), 2a (1.0 mmol), CuFe2O4 (5 mol%,
12 mg), N2, 24 h. b Isolated yield.
to other bases such as K2CO3, K3PO4, NaOH, NaOMe, NaO-tBu,
KO-tBu (Table 1, Entries 9–14). It is noteworthy to observe that the
choice of DMSO as the solvent with Cs2CO3 as a base at 100 ◦C
was crucial for the present C–S coupling reaction. Studies were
conducted on different metal oxides as catalysts for the synthesis of
diaryl sulfides. The coupling reaction did not occur in the absence
of catalyst, and the optimal reaction conditions for the desired
C–S cross-coupling reaction were found to be 5 mol% CuFe2O4,
1.0 equiv. of Cs2CO3 and DMSO (2.0 mL) as solvent at 100 ◦C to
afford the corresponding diphenyl sulfide as product in 98% yield
(Table 2, Entry 5).
In the course of optimization studies towards C–S bond
formation, different metal oxide nanoparticles, such as SnO2,
Y2O3, NiFe2O4, ZnFe2O4, CuFe2O4, YFe2O4 and Co3O4, were
used as catalysts for the C–S cross-coupling process with aryl
halides and thiols under ligand-free conditions and the results are
summarized in Table 2. After standardization of all the reaction
parameters, the proposed catalytic system was employed to cross-
couple a wide variety of commercially available aliphatic/aromatic
iodides and aryl bromides with aromatic/aliphatic thiols under
ligand-free conditions. In general, all the reactions were very clean,
neat and the corresponding diaryl sulfides were obtained in good
to excellent yields as presented in Table 3. Electron withdrawing
groups at the para-position of the aryl iodides afforded high
yields compared to electron donating groups at the para-position.
Satisfactory yields were obtained in the case of electron donating
and electron withdrawing groups at the para-position of the
aryl thiols. Using this protocol, various alkyl-substituted iodides
reacted with different thiols affording the corresponding products
in good to high yields (Table 3, Entries 18–20). It was observed
that there is a slight decrease in the product yield as the carbon
length chain was increased in the case of the aliphatic thiols.
The sterically demanding ortho-substituents underwent aryl
thiolation without any difficulty and gave the corresponding diaryl
sulfides in good yields (Table 3, Entries 11–12). It is significant
to note that the aryl iodide, on reaction with benzenethiol, was
Results and discussion
During our initial studies towards the development of CuFe2O4
nanoparticle-catalyzed C–S cross-coupling reactions, iodoben-
zene and benzenethiol were chosen as model substrates and the
reaction was conducted in the presence of Cs2CO3 as base and
◦
DMSO as solvent at 100 C (Scheme 1). In this process various
parameters were investigated, such as the effect of temperature,
base and solvent on the synthesis of the diaryl sulfides.
Scheme 1 Nano-CuFe2O4-catalyzed cross-coupling of aryl iodide with
benzenethiol.
The reaction failed to give the desired product when it is at room
temperature, instead starting materials were recovered (Table 1,
Entry 1). The same reaction at the slightly elevated temperature
around 80 ◦C afforded a low yield of the product (Table 1, Entry
2). Among the several solvents tested, DMF, 1,4-dioxane, toluene,
water and CH3CN were less effective compared to DMSO (Table 1,
Entries 4–8). Cs2CO3 as base gave impressive yield when compared
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Table 2 Optimization studies on C–S cross-coupling reaction with different nanocatalystsa
Entry
Aryl halide
Benzenethiol
Diphenyl sulphide
Nanocatalyst (5 mol%)
Yieldb (%)
1
2
3
4
5
6
7
SnO2
Y2O3
NiFe2O4
ZnFe2O4
CuFe2O4
YFe2O4
CoFe2O4
58
75
70
60
98
65
62
8
9
10
11
12
13
14
SnO2
Y2O3
NiFe2O4
ZnFe2O4
CuFe2O4
YFe2O4
CoFe2O4
54
52
45
42
81
43
45
15
16
17
18
19
20
21
SnO2
Y2O3
NiFe2O4
ZnFe2O4
CuFe2O4
YFe2O4
CoFe2O4
56
50
50
55
89
45
48
a Reaction conditions: aryl halide (1.0 mmol), benzenethiol (1.0 mmol), Cs2CO3 (1.0 equiv.), DMSO (2.0 mL), N2, 100 ◦C, 24 h. b Isolated yield.
proved to be more reactive towards the thioetherification process
than aryl bromide (Table 3, Entries 21–25), and chlorobenzene did
not react in the present reaction conditions (Table 3, Entry 26).
In order to extend the scope of the proposed catalytic system, the
thioetherification process has been studied with various aryl/alkyl
iodides on reaction with various thiols and the results are presented
in Table 4. This protocol very efficiently cross-coupled various
iodobenzenes with diphenyl disulfide and it was found that the
yields of the expected products, were good to excellent as shown
in the representative Table 5.
The reusability of the nano-CuFe2O4 catalyst was examined
and the results are summarized in Table 6. The catalyst was
magnetically separated from the reaction mixture after completion
of the reaction, washed with ethyl acetate and acetone, air dried
and used directly for further catalytic reactions. No significant loss
of catalyst (CuFe2O4) activity was observed up to four cycles.
Next, the leaching of metal from the CuFe2O4 nanopowder
was checked. After the separation, the filtrate was tested by
the AAS (Atomic Absorption Spectroscopy) technique; it was
found that 0.001% of the metal leached into the solution after
the second cycle. This study clearly demonstrated that there
was no significant amount of leaching. It is also observed from
spectral studies that there is no change in the nature of the
catalyst even after four cycles. The SEM analysis34 of CuFe2O4
nanoparticles before and after the reaction showed identical shape
and size (Fig. 1, ESI†). In addition, the powder X-ray diffraction
analysis34 exhibited identical peaks for both fresh and recovered
CuFe2O4 nanoparticles, which were compared with those reported
in the literature33 (Fig. 2, ESI†). These experimental results clearly
suggest that there was no significant change in the catalytic activity
of nano-CuFe2O4 before and after the reaction.
Scheme 2 Proposed mechanism for C–S cross-coupling.
Conclusions
In summary, we have developed a facile and efficient protocol for
the S-arylation of aryl/aliphatic halides with aromatic/aliphatic
thiols as well as diphenyl disulfide using a heterogeneous CuFe2O4
nanoparticle catalyst in the absence of any ligand. This inex-
pensive, mild and clean procedure provides a convenient route
for a variety of substituted organic sulfides, offers significant
improvements with regard to operational simplicity, and works
efficiently with general applicability giving high yields of the
corresponding products. Further investigations on other useful
applications of this catalyst are in progress. To the best of our
knowledge, this is the first report on magnetically separable
recyclable nano-CuFe2O4-catalyzed C–S bond formation with
aryl/alkyl iodides and aryl/alkyl thiols to afford aryl and alkyl
sulfides.
We thought that the proposed mechanism for the CuFe2O4
nanoparticle-catalyzed coupling reaction involves a oxidative ad-
dition followed by reductive elimination mechanism as illustrated
in Scheme 2.
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Table 3 Nano-copper ferrite-catalyzed cross-coupling of aryl halides
Table 3 (Contd.)
with thiolsa
Entry Aryl halide
17
Product
Yieldb (%)
Entry Aryl halide
1
Product
Yieldb (%)
3q 88
3a 98
2
3
3b 81
18
19
20
21
22
C10H21I
C8H17I
C6H13I
3r
3s
3t
3a
3e
78
80
85
80
75
3c
82
4
3d 79
5
6
7
8
3e
3f
85
84
23
24
25
26
3b 70
3g 89
3h 83
3g
3c
3a
72
70
—
9
3i
3j
80
70
10
a Reaction conditions: aryl halide (1.0 mmol), benzenethiol (1.0 mmol),
CuFe2O4 (5 mol%, 12 mg), Cs2CO3 (1.0 equiv.), DMSO (2.0 mL), N2,
100 ◦C, 24 h. b Isolated yield.
11
12
3k 76
Experimental section
3l
75
General information
Aryl halides (99%), diphenyl disulphide (99.5%), benzenethiol
(99%), nano-CuFe2O4 (99.9%) and other aryl halides were pur-
chased from Sigma Aldrich and Fluka and were used without
purification. All experiments were carried out under nitrogen
atmosphere. Column chromatography was carried out with 60–120
sized mesh silica gel using hexane as eluent. Analytical TLC was
performed with Merck silica gel 60 F254 plates, and the products
were visualized by UV detection. 1H NMR and 13C NMR (Avance
300, Innova 400 MHz and Brucker Gemini 200 MHz) spectra were
recorded in CDCl3 using TMS as internal standard. Chemical
shifts (d) are reported in ppm, and spin–spin coupling constants
(J) are in Hz. Melting points were determined on a Fischer–Johns
melting point apparatus. IR and MS were recorded on a Thermo
13
14
3m 76
3n 80
15
16
3o 86
3p 85
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Table 4 Nano-copper ferrite catalyzed cross-coupling of aryl iodides with
Table 5 Nano-copper ferrite-catalyzed cross-coupling of aryl halides
various thiolsa
with diphenyl disulfidesa
Entry Aryl halide Thiol
1
Product
Yieldb (%)
Entry
1
Aryl halide
Product
Yieldb (%)
97
3c 89
3a
3b
2
3
4a 85
3b 88
2
3
4
89
90
86
3c
3f
4
5
4b 81
3r 80
4c 79
5
3d
85
6
7
C5H11SH
6
7
3e
3g
86
82
C4H9SH
C4H9SH
4d 79
8
4e 81
4f 80
4g 80
8
9
3m 80
9
3h
81
10
10
11
12
C6H13I
C10H21I
C8H17I
3t
3r
3s
85
78
80
a Reaction conditions: aryl iodide (1.0 mmol), thiol (1.0 mmol), CuFe2O4
(5 mol%, 12 mg), Cs2CO3 (1.0 equiv.), DMSO (2.0 mL), N2, 100 ◦C, 24 h.
b Isolated yield.
Nicolet Nexus 670 FT-IR spectrometer and Finnegan MAT 1020
mass spectrometer operating at 70 eV.
a Reaction conditions: aryl iodide (1.0 mmol), diphenyl disulfide
(0.5 mmol), CuFe2O4 (5 mol, 12 mg), Cs2CO3 (1.0 equiv.), DMSO (2.0 mL),
N2, 100 ◦C. 24 h. b Isolated yield.
Representative experimental procedure for the synthesis of diphenyl
sulfides using CuFe2O4 as a catalyst
Table 6 Recyclability of nano-CuFe2O4 catalysta
To a stirred solution of aryl halide (1.0 mmol) and thiol (1.0 mmol)
in dry DMSO (2.0 mL) were added CuFe2O4 nanopowder (5
mol%, 12 mg) and Cs2CO3 (1.0 equiv.), and the reaction mixture
was heated at 100 ◦C under nitrogen atmosphere. After the
completion of the reaction for 24 h, as monitored by TLC, the
reaction mixture was extracted with ethyl acetate (3 ¥ 10 ml). The
combined organic layers were dried with anhydrous Na2SO4. The
solvent was evaporated under vacuum to give the crude product,
which was purified by column chromatography with hexane as
eluent to get the expected products in good yields. The purity
Entry
Isolated product yield (%)
Catalyst recovery (%)
1
2
3
98
91
89
95
90
85
a Reaction conditions: 1a (1.0 mmol), 2a (1.0 mmol), CuFe2O4 (5 mol %,
1
of the product was confirmed by H and 13C NMR and mass
12 mg), Cs2CO3 (1.0 equiv.), DMSO (2.0 mL), N2, 100 ◦C, 24 h.
spectroscopy.
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Spectral data for representative examples
7.12 (m, 5H), 6.88–6.79 (m, 2H), 6.75–6.69 (m, 1H), 3.74 (s, 3H).
13C NMR (75 MHz, CDCl3) d 160.1, 137.2, 135.5, 131.3, 129.8,
129.1, 127.1, 123.0, 115.9, 112.8, 55.1. IR (neat): n 3448, 3050,
1579, 1535, 1490, 1045, 875, 776 cm-1. EI-MS: m/z 216.
Diphenylsulfane (3a)22 (Table 3, Entry 1). Colorless oil (98%,
182 mg). 1H NMR (300 MHz, CDCl3) d 7.33–7.16 (m, 10H). 13
C
NMR (75 MHz, CDCl3) d 135.7, 130.9, 129.1, 126.9, 124.7. IR
(neat): n 3056, 2924, 2853, 1948, 1475, 1078, 908, 739, 690 cm-1.
EI-MS: m/z 186.
2-(Phenylthio)phenol (3k)17 (Table 3, Entry 11). Colorless oil
(76%, 153 mg). 1H NMR (300 MHz, CDCl3) d 7.42–7.17 (m, 9H).
13C NMR (75 MHz, CDCl3) d 162.3, 135.8, 131.0, 129.1, 128.2,
127.0, 125.5, 116.4. IR (neat): n 3400, 2925, 1599, 1130, 879, 760
cm-1. EI-MS: m/z 202.
(4-Methoxyphenyl)(phenyl)sulfane (3b)22 (Table 3, Entry 2).
Colorless oil (81%, 174 mg). 1H NMR (300 MHz, CDCl3) d 7.41
(d, J = 8.2 Hz, 2H), 7.24–7.17 (m, 2H), 7.14–7.12 (m, 3H), 6.84 (d,
J = 8.2 Hz, 2H), 3.77 (s, 3H). 13C NMR (75 MHz, CDCl3) d 159.5,
138.7, 135.5, 128.9, 128.3, 125.8, 124.2, 115.1, 55.4. IR (neat): n
3448, 1575, 1490, 1045, 853, 747 cm-1. EI-MS: m/z 216.
(2-Nitrophenyl)(phenyl)sulfane (3l)23 (Table 3, Entry 12). Yel-
lowish oil (75%, 173 mg). 1H NMR (300 MHz, CDCl3) d 7.42 (d,
J = 1.6 Hz, 1H), 7.56–7.43 (m, 5H) 7.11 (d, J = 9.0 Hz, 2H). 13
C
NMR (75 MHz, CDCl3) d 148.9, 145.6, 135.2, 130.9, 130.2, 130.1,
127.2, 124.5. IR (neat): n 3448, 3040, 3100, 3090, 2950, 2854, 845,
725 cm-1. EI-MS: m/z 231.
Phenyl(p-tolyl)sulfane (3c)22 (Table 3, Entry 3). Yellowish oil
(82%, 164 mg). 1H NMR (300 MHz, CDCl3) d 7.31–7.18 (m, 4H),
7.17–7.07 (m, 3H) 7.01 (d, J = 7.5 Hz, 2H), 2.34 (s, 3H). 13C NMR
(75 MHz, CDCl3) d 137.7, 137.1, 132.4, 131.3, 130.1, 129.5, 128.5,
126.1, 21.1. IR (neat): n 3448, 2923, 2854, 1582, 1082, 808, 741,
516 cm-1. EI-MS: m/z 200.
(4-Isopropylphenyl)(phenyl)sulfane (3m)30 (Table 3, Entry 13).
Yellowish oil (76%, 173 mg). 1H NMR (300 MHz, CDCl3) d 7.46–
7.12 (m, 9H), 3.05–2.78 (m, 1H), 1.27 (d, J = 7.2 Hz, 6H). 13C
NMR (75 MHz, CDCl3) d 148.5, 136.9, 132.0, 131.8, 130.1, 129.2,
128.1, 127.3, 127.0, 126.5, 33.8, 23.7. IR (neat): n 3448, 3050, 2915,
2854, 1052, 875, 736 cm-1. EI-MS: m/z 228.
(4-Tert-butylphenyl)(phenyl)sulfane (3d)21b (Table 3, Entry 4).
Yellowish oil (79%, 191 mg). 1H NMR (300 MHz, CDCl3) d
7.37–7.07 (m, 9H), 1.31 (s, 9H). 13C NMR (75 MHz, CDCl3) d
152.1, 136.5, 131.5, 130.5, 130.2, 129.0, 128.2, 126.6, 124.2, 34.6,
31.3. IR (neat): n 3055, 2915, 2854, 1022, 842, 736 cm-1. EI-MS:
m/z 242.
(3,5-Dimethylphenyl)(phenyl)sulfane (3n)21d (Table 3, Entry 14).
Yellowish oil (80%, 171 mg). 1H NMR (300 MHz, CDCl3) d 7.35–
7.15 (m, 4H), 7.12–7.03 (m, 2H), 6.97–6.82 (m, 2H), 2.27 (s, 6H).
13C NMR (75 MHz, CDCl3) d 138.6, 135.1, 131.6, 130.4, 129.2,
129.0, 128.2, 127.5, 126.5, 125.5, 21.2. IR (neat): n 3050, 2918,
1570, 809, 727 cm-1. EI-MS: m/z 214.
(4-Fluorophenyl)(phenyl)sulfane23 (3e) (Table 3, Entry 5). Yel-
lowish oil (85%, 173 mg). 1H NMR (300 MHz, CDCl3) d 7.38–7.31
(m, 2H), 7.26–7.12 (m, 5H), 6.98 (t, J = 8.3 Hz, 2H). 13C NMR
(75 MHz, CDCl3) d 164.0, 160.5, 136.8, 134.1, 134.1, 130.2, 129.8,
129.2, 126.8, 116.4, 116.1. IR (neat): n 1599, 1576, 1060, 827, 730
cm-1. EI-MS: m/z 204.
Naphthalen-2-yl(phenyl)sulfane (3o)23 (Table 3, Entry 15). Yel-
lowish oil (86%, 202 mg). 1H NMR (300 MHz, CDCl3) d 8.0–7.62
(m, 4H), 7.60–7.09 (m, 8H). 13C NMR (75 MHz, CDCl3) d 135.8,
133.9, 132.8, 132.2, 130.9, 129.7, 129.1, 128.9, 128.5, 127.5, 127.3,
127.0, 126.7, 126.3. IR (neat): n 3054, 1560, 1510 cm-1. EI-MS:
m/z 236.
(4-Chlorophenyl)(phenyl)sulfane (3f)22 (Table 3, Entry 6). Yel-
lowish oil (84%, 184 mg). 1H NMR (300 MHz, CDCl3) d 7.29–7.07
(m, 9H). 13C NMR (75 MHz, CDCl3) d 132.8, 131.3, 129.5, 127.3.
IR (neat): n 1595, 1570, 1050 cm-1. EI-MS: m/z 220.
2-(Phenylthio)thiophene (3p)17 (Table 3, Entry 16). Colorless
1
oil (85%, 163 mg). H NMR (300 MHz, CDCl3) d 7.59–7.43 (m,
4-(Phenylthio)benzonitrile (3g)22 (Table 3, Entry 7). Colorless
3H), 7.37–7.18 (m, 5H). 13C NMR (75 MHz, CDCl3) d 137.0,
129.0, 127.5, 127.1. IR (neat): n 3070, 1515, 1470, 1435, 1395 cm-1.
EI-MS: m/z 192.
1
oil (89%, 187 mg). H NMR (300 MHz, CDCl3) d 7.53–7.44 (m,
4H), 7.32–7.24 (m, 3H), 7.23–7.17 (m, 2H). 13C NMR (75 MHz,
CDCl3) d 140.5, 137.1, 129.0, 127.5, 127.1, 115.6, 108.6. IR (neat):
n 2924, 2250, 1567, 1577, 1403 cm-1. EI-MS: m/z 211.
1,4-Bis(phenylthio)benzene (3q)28 (Table 3, Entry 17). Color-
less oil (88%, 258 mg). 1H NMR (300 MHz, CDCl3) d 7.61–7.54
(m, 3H), 7.40–7.17 (m, 8H), 7.03–6.97 (m, 3H). 13C NMR (75 MHz,
CDCl3) d 139.3, 138.0, 132.0, 131.8, 129.3, 127.5. IR (neat): n 3449,
2922, 2852, 1469, 1081, 806, 690 cm-1. EI-MS: m/z 294.
(4-Nitrophenyl)(phenyl)sulfane (3h)21b (Table 3, Entry 8). Yel-
lowish oil (83%, 191 mg). 1H NMR (300 MHz, CDCl3) d 8.05 (d,
J = 8.9 Hz, 2H), 7.56–7.41 (m, 5H) 7.12 (d, J = 8.9 Hz, 2H). 13
C
NMR (75 MHz, CDCl3) d 148.9, 145.5, 135.0, 130.9, 130.3, 130.2,
127.3, 124.5. IR (neat): n 3040, 3100, 3090, 2950, 2854, 1570, 930,
845, 725 cm-1. EI-MS: m/z 231.
Decyl(phenyl)sulfane (3r)23 (Table 3, Entry 18). Colorless oil
(78%, 195 mg). 1H NMR (300 MHz, CDCl3) d 7.33–7.04 (m, 5H),
2.86 (t, J = 7.2 Hz, 2H), 1.71 (p, J = 7.1 Hz, 2H), 1.46–1.13 (m,
14H), 0.89 (t, J = 7.0 Hz, 2H). 13C NMR (75 MHz, CDCl3) d 137.1,
128.8, 125.5, 33.6, 31.7, 29.4, 29.3, 29.2, 28.7, 22.5, 14.1. IR (neat):
n 3449, 3359, 3010, 2850, 1158 cm-1. EI-MS: m/z 250.
Phenyl(3-(trifluoromethyl)phenyl)sulfane (3i)10a (Table 3, Entry
9). Colorless oil (80%, 203 mg). 1H NMR (300 MHz, CDCl3) d
7.60–7.54 (m, 1H), 7.28–7.16 (m, 4H), 7.01–6.92 (m, 2H), 6.84–
6.78 (m, 2H). 13C NMR (75 MHz, CDCl3) d 138.7, 133.6, 132.6,
129.6, 129.4, 128.2, 126.1, 126.2, 125.5, 123.1. IR (neat): n 2930,
1577, 1475, 1421, 1320, 1166 cm-1. EI-MS: m/z 254.
Octyl(phenyl)sulfane (3s)29a (Table 3, Entry 19). Colorless oil
(80%, 177 mg). 1H NMR (300 MHz, CDCl3) d 7.29–7.19 (m, 4H),
7.14–7.07 (m, 1H), 2.87 (t, J = 7.5 Hz, 2H), 1.63 (p, J = 7.5 Hz, 2H),
1.48–1.20 (m, 10H), 0.88 (t, J = 6.7 Hz, 2H). 13C NMR (75 MHz,
CDCl3) d 137.0, 128.6, 128.5, 125.3, 33.4, 31.7, 29.2, 29.1, 28.7,
(3-Methoxyphenyl)(phenyl)sulfane (3j)20b (Table 3, Entry 10).
Yellowish oil (70%, 151 mg). 1H NMR (300 MHz, CDCl3) d 7.35–
5994 | Org. Biomol. Chem., 2011, 9, 5989–5996
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22.6. 14.1. IR (neat): n 3449, 3359, 3010, 2850, 1158 cm-1. EI-MS:
m/z 222.
(75 MHz, CDCl3) d 136.5, 132.9, 131.2, 129.6, 47.0, 33.1, 26.0,
25.9, 21.1. IR (neat): n 3340, 2850, 1715, 1640, 1035, 740, 815, 635
cm-1. EI-MS: m/z 206.
Hexyl(phenyl)sulfane (3t)29a (Table 3, Entry 20). Colorless oil
(85%, 164 mg). 1H NMR (300 MHz, CDCl3) d 7.40–7.17 (m, 4H),
7.16–7.06 (m, 1H), 2.89 (t, J = 7.9 Hz, 2H), 1.64 (p, J = 7.9 Hz, 2H),
1.55–1.21 (m, 6H), 0.90 (t, J = 7.5 Hz, 2H). 13C NMR (75 MHz,
CDCl3) d 137.0, 128.7, 128.6, 125.5, 33.5, 31.9, 31.3, 29.6, 29.3,
29.0, 28.5, 22.5, 14.1. IR (neat): n 3400, 3359, 3010, 2925, 2850,
1579 cm-1. EI-MS: m/z 194.
Acknowledgements
We are grateful to UGC, New Delhi for the research fellowships
to KS and CSIR, New Delhi for SNM.
References
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C
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