Recyclable heterogeneous supported copper-catalyzed coupling of thiols with aryl halides: base-controlled differential arylthiolation of bromoiodobenzenes

Article abstract of DOI:10.1002/adsc.200900358

Alumina-supported copper sulfate efficiently catalyzes the 5-arylation of aromatic, heteroaromatic and aliphatic thiols with aryl as well as heteroaryl halides under aerobic, ligand-free conditions. This protocol provides an easy access to a variety of thioethers as well as unsymmetrical bis-thioethers by base-controlled differential coupling of thiols with iodo- and bromo-substituents in an aromatic halide. The catalyst is inexpensive, non-air sensitive, environmentally friendly and recyclable.

Full text of DOI:10.1002/adsc.200900358

FULL PAPERS
DOI: 10.1002/adsc.200900358
Recyclable Heterogeneous Supported Copper-Catalyzed Coupling
of Thiols with Aryl Halides: Base-Controlled Differential
Arylthiolation of Bromoiodobenzenes
Sukalyan Bhadra,a Bojja Sreedhar,b and Brindaban C. Ranua,*
a
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata – 700 032, India
Fax : (+91)-33-2473-2805; e-mail: ocbcr@iacs.res.in
Inorganic Chemistry Division, Indian Institute of Chemical Technology, Hyderabad – 500 007, India
b
Received: May 22, 2009; Published online: September 23, 2009
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200900358.
Abstract: Alumina-supported copper sulfate effi- iodo- and bromo-substituents in an aromatic halide.
ciently catalyzes the S-arylation of aromatic, hetero- The catalyst is inexpensive, non-air sensitive, envi-
aromatic and aliphatic thiols with aryl as well as het- ronmentally friendly and recyclable.
eroaryl halides under aerobic, ligand-free conditions.
This protocol provides an easy access to a variety of Keywords: aryl-sulfur bond; cross-coupling; hetero-
thioethers as well as unsymmetrical bis-thioethers by geneous catalyst; recycling; unsymmetrical organic
base-controlled differential coupling of thiols with sulfides
Introduction
Catalysis by a metal, anchored on a heterogeneous
support, has received tremendous attention in recent
The formation of aryl-sulfur, aryl-nitrogen and aryl- times.[8] The primary advantages of using a heteroge-
oxygen bonds is of much importance because of the neous catalyst compared to a homogeneous counter-
presence of these bonds in many molecules of biologi- part are ease of separation of product, reusability of
cal and material interest.[1] The transition metal-cata- catalyst, improved efficiency due to stable active site
lyzed coupling of aryl halides with thiols, phenols and and better steric control of a reaction intermediate.[9]
amines are one of the most powerful tools for the
As a part of our program to utilize heterogeneous
construction of these bonds.[2] Among these three catalysts for useful reactions[10] we report here an alu-
aryl-heteroatom bonds, aryl-sulfur bond formation is mina-supported Cu(II)-catalyzed,[11,12] ligand-free cou-
relatively complicated because of the associated oxi- pling of aryl halides and thiols in presence of a base
À
dative S S coupling reaction and deactivation of (Scheme 1).
metal catalysts by sulfur compounds. A variety of
Pd,[3] Cu,[4] Co,[5] Ni[6] and more recently Fe[7] catalysts,
usually in presence of a ligand has been used for aryl-
sulfur bond formation by the coupling of aryl halides
with thiols. However, the high cost and air sensitivity
of Pd catalysts and often tedious procedure for the
preparation of ligands restrict their applications in
Scheme 1. Cross-coupling of aryl halides and thiols.
large-scale processes. On the other hand, in general,
Co and Ni catalysts are associated with toxicity. The
Cu-mediated reactions sometimes require the use of Results and Discussion
Cu salts in a more than stoichiometric amount, high
temperature and long reaction time. Thus, develop- The catalyst was prepared by stirring an aqueous solu-
ment of alternative inexpensive, ligand-free, non-air tion of CuSO4 and basic alumina followed by removal
sensitive and recyclable catalysts for this useful reac- of water under reduced pressure at 1208C. EDX
tion is highly desirable in the context of environmen- (energy dispersive X-ray) spectra (Figure 1) of the
tal and industrial cocerns.
light green powder confirmed the presence of Cu and
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Figure 1. EDX spectra of the catalyst.
Al. FESEM (field emission scanning electron micro-
scopy) (Figure 2) and AFM (atomic force microsco-
py) images (Figure 3, top and bottom) illustrate its
morphology.
To optimize the reaction conditions, the coupling of
iodobenzene with thiophenol was studied. The best
results for this reaction were obtained using 5 mol%
catalyst in DMF at 100–1108C in presence of K2CO3
(Table 1, a), whereas the coupling of bromobenzene
and thiophenol proceeded efficiently in the presence
of Cs2CO3 (Table 1, b).
The reaction is not very effective using CuSO4
alone without anchoring it on basic alumina. The re-
action of iodobenzene and thiophenol using CuSO4
alone provides only 35% yield, whereas the reaction
with bromobenzene gives even lower yield (10%).
The reaction using a mixture of alumina and CuSO4
Figure 3. ACHTNUTRGNE(UGN Top) AFM image of Cu/Al2O3 catalyst. (Bottom)
AFM topological image of the catalyst.
Table 1. Optimization of reaction conditions.
also did not show much improvement. Use of basic
alumina as support is found to give best results in
terms of yield and reaction time compared to neutral
Figure 2. SEM image of Cu/Al2O3 catalyst.
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Recyclable Heterogeneous Supported Copper-Catalyzed Coupling of Thiols
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alumina, zeolite and hydrotalcite. The other Cu(II) (Table 3). A heteroaryl bromide, ortho-substituted
salts such as Cu(OAc)2, Cu(NO3)2, Cu(OTf)2 and bromobenzene and heteroaryl thiols were compatible
CuCl2 in place of CuSO4 did not produce good results in this coupling too. Under these conditions the Br
A
R
ACHTUNGTRENNUNG
when anchored on basic alumina.
substituent couples selectively with SH without any
À
Several substituted aryl iodides underwent coupling reaction with the NH2 present in the aryl ring of the
with a variety of functionalized thiols in the presence thiol (Table 3, entry 4). On the other hand, reaction
of K2CO3 to produce the corresponding diaryl/aryl- of 4-chlorothiophenol with 2-bromoaniline is limited
alkyl sulfides. The results are summarized in Table 2. to coupling of SH with Br only without any self-cou-
Both electron-donating and electron-withdrawing pling of bromoaniline (Table 3, entry 5). Taking ad-
group-substituted iodobenzenes participated in this vantage of the base-controlled highly selective aryl-
reaction with similar efficiency. A heteroaryl iodide
ACHTUNGTRENtNUNG hiolation of iodo- and bromobenzenes we then fo-
underwent arylthiolation efficiently (Table 2, cused our attention to the sequential coupling of io-
entry 16). Aliphatic thiols also coupled with aryl io- dobromobenzenes. Thus, iodobromobenzene was cou-
dides under these conditions (Table 2, entries 14 and pled with n-butyl thiol in the presence of K2CO3
15), which is difficult to achieve.[7b] The sterically hin- followed by treatment with 2-aminothiophenol in the
dered ortho-substituted iodobenzoic acid underwent presence of Cs2CO3 leading to a benzene derivative
arylthiolation without any difficulty (Table 2, entry 9). substituted with two different thio-moieties at two
This Cu catalyst was also found to be very effective ends.
for coupling of aryl iodides with thiols bearing hetero-
Several bis-thioethers were achieved by this se-
cyclic moieties (Table 2, entries 11, 17 and 18). This quence as illustrated in Scheme 2. This reaction has
reaction is of much importance as these heterocyclic enormous scope for an easy access to a library of bis-
sulfides are very useful compounds.[13] Nevertheless, thioethers and will have much potential in organic
this coupling is rarely addressed by earlier methods.[7b] synthesis. For example, the poly-(p-phenylene sulfide)
This Al2O3-supported Cu catalyst is highly chemose- polymers are commercially very important materials
À
lective, demonstrating exclusive coupling of SH with
because of their uses as thermoplastics, fire retardants
I without any parallel coupling with OH present in etc.[14]
À
À
the aryl ring of the thiol (Table 2, entries 4 and 5).
In general, the reactions are very clean and high
The substituted fluoro, chloro and bromo functionali- yielding. No ligand has been used. No diaryl/dialkyl
ties in aryl iodides remained inert under these condi- disulfide was found in any of these coupling reactions.
tions using K2CO3 as base (Table 2, entries 6, 10, 11, The CuSO4/Al2O3 catalyst is very robust and not air-
12, 14, 15). Very interestingly, the coupling of thiols sensitive. The reactions were carried out in ordinary
with bromobenzenes proceeded efficiently in the DMF (no drying is necessary) without the require-
presence of Cs2CO3 (Table 1, b). Thus several substi- ment of an inert atmosphere. No appreciable leaching
tuted bromobenzenes were treated with various func- of catalyst was detected as measured by ICP-MS (in-
tionalized thiols to provide the corresponding sulfides ductively coupled plasma mass spectrometry) and
À
Scheme 2. Base-controlled differential C S bond formation of bromoiodobenzene.
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Table 2. Cu-catalyzed C-S cross-coupling of aryl iodides.[a]
[a]
Reaction conditions: ArI (1.0 equiv.), RSH (1.1 equiv.), Cu/Al2O3 (5 mol%), K2CO3
(2 equiv.), DMF (3 mL), 1108C. [b] Isolated yield of pure product.
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Recyclable Heterogeneous Supported Copper-Catalyzed Coupling of Thiols
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[a]
À
Table 3. Cu-catalyzed C S cross coupling of aryl bromides.
[a]
Reaction conditions: ArBr (1.0 equiv.), RSH (1.1 equiv.), Cu/Al2O3 (5 mol%), Cs2CO3
(1.5 equiv.), DMF (3 mL), 1108C.
Isolated yield of pure product.
[b]
[a]
À
Table 4. Cu-catalyzed C O cross-coupling of aryl iodides.
control experiments. The catalyst in DMF was heated
for 8 h in the presence of K2CO3 and the supernetant
liquid after centrifuging did not show any catalytic ac-
tivity for a coupling reaction of iodobenzene and thio-
phenol. The catalyst is recyclable and in fact, it was
reused for eight times without any loss of efficiency
(Cu content in fresh catalyst: 0.517 mmolgÀ1, Cu con-
tent in recovered catalyst after 8th cycle: 0.503 mmol
gÀ1as measured by ICP-MS). This procedure is com-
patible with a variety of functionalities such as OMe,
OCF3, CO2H, CF3, CN, NH2 etc.
[a]
Reaction
conditions:
Ar1I
(1.0 equiv.),
Ar2OH
(1.2 equiv.), Cu/Al2O3 (5 mol%), Cs2CO3 (2 equiv.), DMF
(3 mL), 1108C.
This Cu/Al catalyst is also effective for the O-aryla-
tion of phenols and N-arylation of amines by aryl hal-
ides as illustrated in Table 4 and Table 5.
[b]
Isolated yield of pure product.
Recently, we reported a similar coupling reaction of
aryl iodide and thiophenol using copper nanoparticles
under ligand-free conditions.[4g] However, the present tron spectroscopic (XPS) study of the fresh and used
procedure using the supported Cu(II) catalyst pro- Cu/Al2O3 catalyst at the Cu 2p level shows the 2p3/2
vides a wider scope using a variety of halides and lines at 934.7 and 934.6 eV, respectively, which indi-
thiols, phenols and amines, sequential thioarylation, cates that Cu is in the +2 oxidation state before and
low catalyst loading and recyclability of catalyst.
after the reaction (Figure 4). To find the intermediate,
To investigate the mechanism of this reaction a few when thiophenol was treated with the catalyst in the
experiments were carried out. The X-ray photoelec- absence of any base, a dirty white complex was
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Table 5. Cu-catalyzed C-N cross-coupling of aryl halides.[a]
base K2CO3 and thus a stronger base, Cs2CO3, is re-
quired to polarize the aryl-Br bond for further reac-
tion.
Conclusions
In summary, we have developed an efficient protocol
for the S-arylation of aromatic, heteroaromatic and
aliphatic thiols with aryl as well as heteroaryl iodides
and bromides using a heterogeneous Al2O3-supported
Cu catalyst under aerobic, ligand-free conditions.
Such a wide scope demonstrated by a single catalyst
has not been reported earlier and this procedure pro-
vides a convenient route to a variety of substituted or-
ganic sulfides. The most attractive feature of this pro-
tocol is the base-controlled differential coupling of
thiols with iodo- and bromo-substituents in an aryl
halide providing unsymmetrical bis-thioethers. To the
[a]
Reaction conditions: ArI/ArBr (1.0 equiv.), R1NHR2
(1.2 equiv.), Cu/Al2O3 (5 mol%), K2CO3 (2 equiv.), H2O
(4 mL), 1008C.
Isolated yield of pure product.
[b]
[c]
Only mono-arylated product.
formed, which shows the appearance of a new band best of our knowledge, we are not aware of any
at 2800–3000 cmÀ1 by FTIR (Figure 5, top and report demonstrating such differential S-arylation in
middle) due to aromatic C-H stretching indicating the this type of coupling reactions. In addition, this novel
addition of thiophenol to the complex and this peak Cu-catalyzed S-arylation protocol is of potential in-
disappeared after the reaction (Figure 5, bottom). The dustrial significance because of its high yields, simplic-
complex II was isolated and when it was treated with ity in operation, scaling up to multogram quantitites,
iodobenzene, no reaction occurred in the absence of and environmental (no leaching of catalyst) and eco-
K2CO3 or Cs2CO3. In the presence of a base, the cor- nomical advantages using commercially available
responding sulfide was obtained. Obviously, the base DMF, an inexpensive, stable and recyclable heteroge-
has a decisive role in this addition-elemination step. neous catalyst, no inert atmosphere and no special
Based on these observations we speculate that in the device for reaction. Further investigations on other
presence of K2CO3/Cs2CO3, complex II[15] undergoes useful applications of this catalyst are in process.
oxidative addition with iodobenzene to give a transi-
ent complex III which on reductive elimination via IV
provided the product and regenerated the catalyst
Experimental Section
À
(Scheme 3). We explain the differential coupling of
I
À
and Br groups using K2CO3 and Cs2CO3 respectively,
by the fact that the bromo substituent being relatively
less reactive than iodo substituent, is not likely to un-
dergo oxidative addition in the presence of the milder
Preparation of Cu/Al2O3 Catalyst
To a well-stirred aqueous solution of CuSO4·5H2O (1.0 g,
4 mmol CuSO4·5H2O dissolved in 25 mL of water) basic alu-
Figure 4. XPS of Cu 2p3/2 for (left) Cu/Al2O3 fresh catalyst; (right) Cu/Al2O3 used catalyst.
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Recyclable Heterogeneous Supported Copper-Catalyzed Coupling of Thiols
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Figure 5. ACHTUNGTRENNUNG(Top) FT-IR spectrum of the fresh Cu/Al2O3 catalyst. (Middle) FT-IR spectrum of Cu/Al2O3-thiophenol complex.
(Bottom) FT-IR spectrum of used catalyst.
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Figure 6. Recyclability chart of the Cu/Al2O3 catalyst.
Scheme 3. Possible reaction pathway.
Cu conÀte1nt of the catalyst after 8th cycle is found to be 0.503
mmolg compared to that of the fresh catalyst as 0.517
mmolgÀ1 as detected by ICP-MS analysis.
mina (6.5 g) was added and the resulting solution was stirred
at an ambient temperature for 2 h. The excess water was
evaporated on a rotary-evaporator under reduced pressure
followed by drying under high vacuum at 1208C for 8 h to
get the Cu/Al2O3 catalyst as a light green powder. (Copper
content of the fresh catalyst: 0.517 mmolgÀ1 as measured by
ICP-MS).
Although the representative experimental procedure was
based on a mmol scale, this procedure was also effective for
multigram (10 g) scale reactions with uniform results.
The known compounds were identified by comparison of
their spectra with those of authentic samples (see references
in Tables 2–5). The unknown compounds were properly
characterized by their spectroscopic data (IR, 1H NMR,
13C NMR and HR-MS) data and elemental analysis and
these data are provided below in order of their entries in
the respective Tables.
General Procedure for Coupling of Thiophenol with
Aryl Iodide
1-Fluoro-3-(4-chlorophenylsulfanyl)benzene
entry 6): Yellow liquid; IR (neat): n=3039, 1486, 1474, 1103,
754, 619 cmÀ1 1H NMR (300 MHz, CDCl3): d=6.93–7.00
(m, 2H), 7.07 (d, 1H, J=7.86 Hz), 7.23–7.44 (m, 5H);
13C NMR (75 MHz, CDCl3): d=113.9 (d, JC,F =22.5 Hz),
116.8 (d, JC,F =22.5 Hz), 125.5, 129.4, 129.7 (2C), 130.5 (d,
(Table 2,
To a solution of iodobenzene (204 mg, 1 mmol) and thiophe-
nol (121 mg, 1.1 mmol) in DMF (3 mL) was added K2CO3
(276 mg, 2 mmol) and Cu-Al2O3 catalyst (100 mg, 5 mol%)
and the mixture was heated at 1108C (oil bath) for a period
of time required for completion (TLC). The reaction mix-
ture was allowed to cool and diluted with Et2O (30 mL) fol-
lowed by washing with aqueous (10%) NaOH solution (2ꢁ
2 mL) and brine. The organic phase was dried (Na2SO4) and
evaporated to leave the crude product which was purified
by column chromatography over silica gel (hexane) to pro-
vide pure diphenyl sulfide as a colourless oil; yield: 181 mg
(97%). The spectroscopic data (1H NMR and 13C NMR) of
this product are in good agreement with those of an authen-
tic sample.
;
J
J
C,F =8.5 Hz), 133.9 (2C), 138.5 (d, JC,F =7.65 Hz), 163.0 (d,
C,F =247.5 Hz); anal. calcd. for C12H8ClFS: C 60.38, H 3.38;
found: C 60.67, H 3.32.
1-(4-Chlorophenylsulfanyl-4-trifluoromethoxybenzene
(Table 2, entry 7): Yellow liquid; IR (neat): n=3018, 1489,
1475, 1261, 1215, 1170, 758 cmÀ1
;
1H NMR (300 MHz,
CDCl3): d=7.16 (d, 2H, J=8.4 Hz), 7.27–7.35 (m, 6H);
13C NMR (75 MHz, CDCl3): d=118.8, 121.9 (2C), 129.7
(2C), 132.2 (2C), 132.8 (2C), 133.7, 133.9, 148.5; anal. calcd
for C13H8ClF3OS: C 51.25, H 2.65; found: C 51.17, H 2.67.
2-(4-Chlorophenylthio)benzoic acid (Table 2, entry 9):
White solid (mp 162–1638C); IR (KBr): n=3320, 1676,
This procedure was followed for all the reactions listed in
Table 2. The coupling with aryl bromide was carried out by
the same procedure using CS2CO3 (1.5 equiv.) in place of
K2CO3 (Table 3).
1558, 1462, 1315, 1253, 900, 813, 744 cmÀ1
;
1H NMR
(300 MHz, DMSO-d6): d=6.75 (d, 1H, J=8.04 Hz), 7.21 (t,
1H, J=7.38 Hz), 7.36 (t, 1H, J=8.04 Hz), 7.55 (m, 4H),
7.93 (d, 1H, J=7.38 Hz), 13.27 (bs, 1H); 13C NMR
(75 MHz; DMSO-d6): d=127.1, 127.9, 130.3 (2C), 130.8,
131.4, 132.4, 136.5 (2C), 140.8, 167.3; HR-MS: m/z=
286.9903, calcd. for C13H9ClO2S [M+Na]+: 286.9909.
Recovery of Catalyst
After the reaction was over, the reaction mixture was centri-
fuged and filtered. The residue was washed with water (5ꢁ
3 mL) followed by acetone (3ꢁ4 mL). The solid was then
dried at 1008C for 8 h for further use. The catalyst was recy-
cled for 8 times for the coupling reaction of iodobenzene
and thiophenol without any loss of activity (Figure 6). The
2-(2-Bromophenylsulfanyl)pyridine (Table 2, entry 11):
Colourless liquid; IR (neat): n=3047, 1573, 1448, 1417,
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1
1116, 1020, 754 cmÀ1; H NMR (300 MHz, CDCl3): d=6.91
(d, 1H, J=7.9 Hz), 7.02 (t, 1H, J=6.08 Hz), 7.23 (t, 1H, J=
7.45 Hz), 7.32 (t, 1H, J=7.45 Hz), 7.48 (t, 1H, J=7.62 Hz),
7.62 (d, 1H, J=7.62 Hz), 7.68 (d, 1H, J=7.90 Hz), 8.43 (s,
1H); 13C NMR (75 MHz, CDCl3): d=120.4, 122.1, 128.3,
129.4 (2C), 130.4, 132.8, 133.8, 136.4, 136.9, 149.8, 159.2;
HR-MS: m/z=295.9646, calcd. for C11H8BrNS [M+H]+:
265.9639.
3H, J=7.97 Hz), 7.79 (d, 1H, J=7.97 Hz); 13C NMR
(75 MHz, CDCl3): d=21.4, 120.7, 121.7, 124.1, 126.1, 126.2
(2C), 130.7 (2C), 135.4, 135.5 (2C), 154.0, 170.8; HR-MS:
m/z= 258.0425, calcd. for C14H11NS2 [M+H]+: 258.0411.
2-(4-Butylsulfanylphenylsulfanyl)phenylamine (Scheme 2,
entry 1): Pale brown oil; IR (neat): n=3426, 2252, 1665,
1108, 1051, 1026, 824, 762 cmÀ1
;
1H NMR (300 MHz,
CDCl3): d=0.90–0.96 (m, 3H), 1.38–1.50 (m, 2H), 1.56–1.67
(m, 2H), 2.87 (t, 3H, J=7.2 Hz), 4.27 (broad, 2H), 6.75–
6.83 (m, 2H), 7.04 (d, 2H, J=8.3 Hz), 7.19–7.27 (m, 3H),
7.46 (d, 1H, J=7.6 Hz); 13C NMR (75 MHz, CDCl3): d=
13.7, 21.9, 31.3, 33.7, 115.6, 118.9, 121.9, 123.6, 126.2 (2C),
129.9 (2C), 131.1, 134.2, 137.3, 148.5; anal. calcd. for
C16H19NS2: C 66.39, H 6.62, N 4.84; found: C 66.20, H 6.51,
N 4.81.
3-(4-Chlorophenylthio)pyridine
(Table 2,
entry 16):
Yellow oil; IR (neat): n=3070, 3043, 1566, 1473, 1406, 1091,
1014, 819, 704 cmÀ1; H NMR (300 MHz, CDCl3): d=7.23–
1
7.28 (m, 5H), 7.57–7.60 (m, 1H), 8.47–8.55 (m, 2H);
13C NMR (75 MHz, CDCl3): d=122.8, 128.3 (2C), 131.2,
131.4 (2C), 131.9, 132.6, 136.8, 146.6, 149.5; HR-MS: m/z=
222.0139, calcd. for C11H8ClNS [M+H]+: 222.0156.
2-(3-Phenylsulfanylphenylsulfanyl)phenylamine
2-[3-(Trifluoromethyl)phenylthio]benzo[d]thiazole
(Scheme 2, entry 3): Brownish viscous oil; IR (neat): n=
3470, 3369, 3059, 1606, 1568, 1477, 1438, 1307, 1159, 1072,
(Table 2, entry 17): Colourless oil; IR (neat): n=3063, 1461,
1426, 1323, 1130, 756, 695 cmÀ1
;
1H NMR (300 MHz,
1
771, 748 cmÀ1; H NMR (300 MHz, CDCl3): d=4.57 (broad,
CDCl3): d=7.25 (t, 1H, J=7.41 Hz), 7.37 (t, 1H, J=
7.41 Hz), 7.52 (t, 1H, J=7.41 Hz), 7.62–7.69 (m, 2H), 7.83–
7.87 (m, 2H), 7.95 (s, 1H); 13C NMR (75 MHz, CDCl3): d=
121.0, 121.6, 122.3, 124.8, 126.4, 126.9, 130.3, 131.3, 131.6,
132.4, 135.7, 137.9, 153.7, 166.7; HR-MS: m/z=310.0120,
calcd. for C14H8F3NS2 [M+H]+: 312.0156.
2H), 6.74–6.84 (m, 2H), 6.90–6.95 (m, 1H), 7.03–7.06 (m,
2H), 7.09–7.16 (m, 1H), 7.20–7.45 (m, 7H); 13C NMR
(75 MHz, CDCl3): d=114.5, 116.0, 119.5, 124.7, 127.1, 127.6,
129.3 (2C), 129.6, 131.3, 132.0 (2C), 134.5, 137.4, 137.6,
138.1, 147.9; anal. calcd. for C18H15NS2: C 69.86, H 4.89, N
4.53; found: C 69.81, H 4.77, N 4.61.
2-(3,5-Dimethylphenylthio)pyridine (Table 2, entry 18):
Colourless oil; IR (neat): n=3041, 2917, 1600, 1573, 1560,
1447, 1416, 1144, 1124, 849, 758, 688 cmÀ1
;
1H NMR
(300 MHz, CDCl3): d=2.33 (s, 6H), 6.89 (d, 1H, J=7.9 Hz),
6.94–6.97 (m, 1H), 6.98 (s, 1H), 7.22 (s, 2H), 7.39–7.45 (m,
1H), 8.40–8.42 (m, 1H); 13C NMR (75 MHz, CDCl3): d=
21.1 (2C), 119.6, 121.1, 130.2, 130.9, 132.5 (2C), 136.6, 139.2
(2C), 149.4, 161.9; HR-MS: m/z=216.0845, calcd. for
C13H13NS [M+H]+: 216.0859.
Acknowledgements
We are pleased to acknowledge the financial support from
DST, New Delhi under the J.C. Bose fellowship to B.C. Ranu
(SR/S2/JCB-11/2008). S.B. thanks CSIR, New Delhi for his
fellowship.
2-(4-Fluorophenylsulfanyl)phenylamine (Table 3, entry 4):
Colourless liquid; IR (neat): n=3317, 2956, 1513, 1469,
1288, 1102, 1010, 811, 752 cmÀ1
;
1H NMR (300 MHz,
DMSO-d6): d=5.40 (broad, 2H), 6.55–6.60 (m, 1H), 6.79–
6.82 (m, 1H), 7.10–7.18 (m, 5H), 7.29–7.32 (m, 1H);
13C NMR (75 MHz, DMSO-d6): d=113.0, 115.4, 116.5 (d,
2C, JC,F =22.5 Hz), 117.2, 129.4 (2C), 131.5, 132.5, 137.2,
150.6, 161.0 (d, 1C, JC,F =247.5 Hz); HRMS: m/z=220.0598,
calcd. for C12H10FNS [M+H]+: 220.0625.
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Adv. Synth. Catal. 2009, 351, 2369 – 2378
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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