Nickel-Schiff base complex catalyzed C-S cross-coupling of thiols with organic chlorides

Article abstract of DOI:10.1016/j.tet.2014.08.020

We report an efficient, mild and convenient synthetic protocol for the C-S cross-coupling reaction of various aryl, benzyl, allyl chlorides and thiols using 5 mol % Nickel-Schiff base catalyst with NaOH as the base, in DMF at 70 °C. Using this protocol, we have shown that a variety of aryl sulfides can be synthesized in excellent yields from readily available organic chlorides and thiols.

Full text of DOI:10.1016/j.tet.2014.08.020

Accepted Manuscript
Nickel-Schiff base complex catalyzed C-S cross-coupling of thiols with organic
chlorides
Prasanta Gogoi, Sukanya Hazarika, Manas J. Sarma, Kuladip Sarma, Pranjit Barman
PII:
S0040-4020(14)01183-1
10.1016/j.tet.2014.08.020
TET 25920
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 3 May 2014
Revised Date: 6 August 2014
Accepted Date: 8 August 2014
Please cite this article as: Gogoi P, Hazarika S, Sarma MJ, Sarma K, Barman P, Nickel-Schiff base
complex catalyzed C-S cross-coupling of thiols with organic chlorides, Tetrahedron (2014), doi: 10.1016/
j.tet.2014.08.020.
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ACCEPTED MANUSCRIPT

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Nickel-Schiff base complex catalyzed C-S cross-coupling of thiols with organic chlorides
Prasanta Gogoi,a Sukanya Hazarika,a Manas J. Sarma,b Kuladip Sarma,a and Pranjit Barmana*
aDepartment of Chemistry, National Institute of Technology, Silchar 788010, Assam, India
bDepartment of Chemistry, Gauhati University, Guwahati 781014, Assam, India
Graphical Abstract:
Keywords: Nickel-Schiff base complex, Thiols, Organic chloride, NaOH
_________
Corresponding author: Tel: +91 9435374128, fax: +91 3842 224797,
E-mail: barmanpranjit@yahoo.co.in (P. Barman)
Abstract: We report an efficient, mild and convenient synthetic protocol for the C-S cross-
coupling reaction of various aryl, benzyl, allyl chlorides and thiols using 5 mol % Nickel-
o
Schiff base catalyst with NaOH as the base, in DMF at 70 C. Using this protocol, we have
shown that a variety of aryl sulfides can be synthesized in excellent yields from readily
available organic chlorides and thiols.

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1. Introduction
Sulfides are important compounds in organic synthesis and many of which are
biologically and pharmacologically active natural products.1 The synthesis of this
privileged structure has attracted significant interest of synthetic chemist who in
recent years have developed numerous synthetic methodologies of organic sulfides.
Most of these methods are focused on transition-metal-catalyzed C–S bond formation
reactions.2 The transition metal catalysts used are palladium,3 nickel,4 copper,5
cobalt,6 zinc,7 iron,8 and indium.9 But almost all of these methods have some inherent
shortcomings like harsh reaction conditions, metal toxicity, and high cost of the metal
which restrict their applications especially in large scale processes. A few reports on
the C-S bond formation using metal-Schiff base complexes10 are also known. More
recently synthesis of diaryl sulfides from thiophenols and aryliodides has been
reported by Punniyamurthy et al.11 albeit in a relatively slow reaction whereas, Peng
et al.12 synthesis of diarylsulfides with electron withdrawing groups in the substrates
gives poor yields. In this piece of work we report an efficient Nickel(II)-Schiff base
complex mediated C-S cross coupling of thiophenols with organic chlorides (Table 2).
2. Results and discussion
Table 1: Optimization of reaction condition for coupling reaction
Entry
Catalyst (mol %)
-------------------
NiCl2.6H2O (10)
Base (Temp oC)
NaOH (100)
NaOH (70)
Solvent
DMF
Time (h)
Yield (%)a
1
2
3
3
nr
DMF
40
3
4
5
NiNO3.6H2O (10)
NiNO3.3H2O (10)
NiL2 (5)
NaOH (70)
NaOH (70)
NaOH (100)
DMF
DMF
DMF
5
5
1
20
19
90

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6
NiL2 (5)
NiL2 (5)
NiL2(5)
NaOH (70)
DMF
DMSO
DMF
1
3
4
4
3
95
50
12
23
11
7
NaOH (70)
8
Piperidine (70)
Triethyl amine (70)
Ethylene
9
NiL2 (10)
NiL2 (10)
DMF
10
DMSO
diammine (70)
aIsolated yield
NiL2 Preparation: The preparation of Nickel-Schiff base complex followed by our earlier
work.13
In our initial screening experiments we chose thiophenol and benzylchloride as the
model substrates (Table 1). Initially we investigated the C-S cross coupling reaction
without a catalyst when no reaction took place (entry 1). However, when an
equimolar mixture of these substrates was stirred for 3 hr at 70 oC in DMF and NaOH
in presence of Ni-catalyst (NiCl2.6H2O) C-S bond formation took place to give 40%
of the desired organic sulfide (entry 2). The yields were still lower when nickel nitrate
hexahydrate and nickel nitrate trihydrate were used as the catalysts under same
reaction conditions (entries 3-4). But the yield dramatically increased when nickel-
Schiff base complex was used as the catalyst (entry 5). The optimum temperature for
o
the best result was found to be 70 C (entry 6) and inorganic base sodium hydroxide
was found to give much better yields in comparison with organic bases pyridine,
piperidine, triethylamine and ethylene diamine (entries 8-10). DMF was found to be
the solvent of choice. The optimized reaction condition, turned out to be using nickel-
Schiff base complex NiL2 (5 mol %), NaOH (1.5 equivalent) in reagent grade DMF at
70 oC for 1 h.
The structure of 2-nitrophenyl benzyl sulfide, 3o (Fig 2) was characterized by X-ray
diffraction.

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Fig 1: Nickel-Schiff base complex (NiL2)
Fig 2: X ray crystal structure analysis of 3o (CCDC 1018005)

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Table 2: C-S cross coupling of Aryl thiols with various organic chloridea
Entry
Product (3)
Time (h)
Yield (%)b
1
3
82
3a
3b
2
3
3
3
74
88
3c
4
5
2
2
99
96
3d
3e
3f
6
7
2
1
81
93
3g
8
3
77
3h
3i
9
3
3
79
76
10
3j

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11
12
3
78
95
3k
3l
1
1
1
1
13
14
15
78
85
99
3m
3n
3o
3p
3q
3r
16
17
18
19
20
89
86
84
77
75
2
2
2
3
3
3s
3t
21
2
88
3u

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22
23
3
74
70
3v
5
3w
24
25
4
2
70
73
3x
3y
26
27
2
3
77
72
3z
3Aa
3Ab
28
29
30
31
2
2
3
3
89
76
65
68
3Ac
3Ad
3Ae
aReaction conditions: NiL2 (5 mol %), arylthiol (1 mmol), organic chloride (1 mmol), NaOH
(1.5 mmol) in DMF (2 mL)
bIsolated yield

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To determine the scope of this method and to test the generality of the protocol, a
range of thiophenols and aryl chlorides were surveyed (Table 2). Various substituents
such as Me, NO2, CN, CF3, COOH, CHO, CO2CH3, COCH3, and OH in the aromatic
ring of the aryl chlorides were well tolerated in the reactions to give good to excellent
yields of the desired diaryl sulfides (Table 2). The polar effects of the substituent in
the aryl halides were found to have very limited influence on the yields of the reaction
through electron withdrawing substituents in the aromatic ring gave a little better
yields (Table 2, entries 4-5 and 7) than those with electron releasing groups in the ring
(Table 2 entries 8-11 and 23).
We consider it to be worth mentioning here that this methodology is quite suitable
with different types of organic chlorides such as allyl, aryl, and benzyl chlorides
though benzyl chlorides were found to be most reactive of all giving desired sulfides
in excellent yields (Table 2, entries 12-15). On the other hand, all types of substituents
in the aromatic ring of the other component thiophenol were found to be well
tolerated in the reaction giving good to excellent yields of the desired organic sulfides.
Polar effects of these substituents on the reactions were found to be minimal (Table 2,
entries 22-31).
The proposed mechanism of this C-S bond formation reaction is in the well known
line11,14 of such low valent transition metal mediated reactions. This involved an
oxidative addition of a substrate to the Ni(0) to give an intermediate (A) which on
ligand substitution reaction with a thiolate anion forms another intermediate (B). The
latter undergoes a reductive elimination of a diaryl sulfide molecule to regenerate the
catalyst Ni(0) (Scheme 1).

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Scheme 1. Outline of a possible reaction pathway
3. Conclusions
In summary, we have developed an efficient catalytic system for the C-S coupling reaction of
o
organic halide with thiols at 70 C in DMF. Under optimal conditions, for all aryl halides,
allyl halides and benzyl halides the corresponding coupling products can be achieved in good
to high yields. This novel method provides a complementary, efficient and easy operational
approach to accessing C-S derivatives.
4. Experimental Section
4.1 General Information
All solvents and chemicals were purchased commercially and used without further
purification. Column chromatography was generally performed on silca gel (230-400 mesh)
and reactions were monitored by thin layer chromatography (TLC) using UV light (254 nm)
1
13
to visualise the course of reactions. H and C Nuclear Magnetic Resonance spectra of pure
compounds were acquired at 400 and 100 MHz respectively. All NMR samples were
recorded in deuterated chloroform. Chemical shifts (ppm) were recorded with
tetramethylsilane (TMS) as the internal reference standard. Elemental analyses were
performed on a Flash 2000 Thermo Scientific instrument at NIT Silchar. CCDC number for
the compound 3o is CCDC 1018005. This data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/deposit/, or from the Cambridge Crystallographic Data Centre,

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12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
4-Nitrophenyl phenyl sulfide (3d):
A mixture of p-nitro-chlorobenzene (157 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 2 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 20/1) to give the title compound 3d (228 mg, 99%) as a pale
o
yellow solid; mp 55-56 C; [Found: C, 62.28; H, 3.96; N, 6.09. C12H9NO2S requires C, 62.32; H,
3.92; N, 6.06 %]; Rf = 0.4 (hexane/ethyl acetate = 20/1). 1H NMR (400 MHz, CDCl3): δ 8.11 (d,
13
J=7.2 Hz, 2H), 7.67-7.59 (m, 2H), 7.47– 7.42 (m, 3H), 7.07 (d, J=8.0 Hz, 2H). C NMR
(100 MHz, CDCl3): δ 148.6, 145.3, 134.8, 130.2, 129.6, 126.7, 124.7, 124.2.
2-Nitrophenyl phenyl sulfide (3e):
A mixture of o-nitro-chlorobenzene (157 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 2 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 4/1) to give the title compound 3e (222 mg, 96%) as a
orange oil; [Found: C, 62.37; H, 3.91; N, 6.11. C12H9NO2S requires C, 62.32; H, 3.92; N, 6.06%]; Rf
= 0.4 (hexane/ethyl acetate = 4/1). 1H NMR (400 MHz, CDCl3): δ 8.21 (d, J=7.3 Hz, 2H), 7.58
(d, J=7.2 Hz, 2H), 7.47(s, 3H), 7.34-7.18 (m, 1H), 6.83 (d, J=7.4 Hz, 1H).13C NMR (100
MHz, CDCl3): δ 144.7, 139.2, 135.7, 133.4, 131.6, 130.9, 130.2, 130.0, 128.7, 125.3, 124.3.
Diphenyl sulfide (3f):
A mixture of chlorobenzene (112 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH (60 mg, 1.5
o
mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 C for 2 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column

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chromatography (hexane/ethyl acetate = 4/1) to give the title compound 3f (150 mg, 81%) as a
colourless oil; [Found C, 77.55; H, 5.47; C12H10S requires C, 77.37; H, 5.41%]; Rf = 0.4
13
(hexane/ethyl acetate = 4/1). 1H NMR (400 MHz, CDCl3): δ 7.40 – 7.27 (m, 10H). C NMR
(100 MHz, CDCl3): δ 135.5, 131.2, 129.2, 127.7.
4-(Phenylthio)benzonitrile (3g):
A mixture of 4-chlorobenzonitrile (137 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 1 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 25/1) to give the title compound 3g (196 mg, 93%) as a
colourless oil; [Found: C, 73.93; H, 4.21; N, 6.68. C13H9NS requires C, 73.90; H, 4.29; N, 6.63%]; Rf
= 0.4 (hexane/ethyl acetate = 25/1). 1H NMR (400 MHz, CDCl3): δ 7.58-7.43 (m, 7H), 7.21-7.17
13
(m, 2H). C NMR (100 MHz, CDCl3): δ 145.3, 135.5, 132.4, 130.6, 130.1, 129.2, 127.4,
118.9, 109.1.
4-Methylphenyl phenyl sulfide (3i):
A mixture of 1-chloro-4-methyl benzene (126 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH (60
mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 3 h. The reaction mixture
was filtered and the solvent evaporated in vacuo to give the crude product, which was purified by
column chromatography (hexane/ethyl acetate = 20/1) to give the title compound 3i (158 mg, 79%) as
a colorless oil; [Found: C, 77.98; H, 6.11. C13H12S requires C, 77.95; H, 6.04%]; Rf = 0.4
(hexane/ethyl acetate = 20/1).1H NMR (400 MHz, CDCl3): δ 7.36-7.22 (m, 9H), 2.37 (s, 3H).
13C NMR (100 MHz, CDCl3): δ 137.8, 137.2, 132.4, 131.2, 129.8, 128.1, 126.8, 21.2.

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3-Methylphenyl phenyl sulfide (3j):
A mixture of 1-chloro-3-methyl benzene (126 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH (60
o
mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 C for 3h. The reaction mixture
was filtered and the solvent evaporated in vacuo to give the crude product, which was purified by
column chromatography (hexane/ethyl acetate = 10/1) to give the title compound 3j (152 mg, 76%) as
a colorless oil; [Found: C, 77.90; H, 6.12. C13H12S requires C, 77.95; H, 6.04%]; Rf = 0.4
(hexane/ethyl acetate = 10/1).1H NMR (400 MHz, CDCl3): δ 7.33-7.21 (m, 9H), 2.33 (s, 3H).
13C NMR (100 MHz, CDCl3): δ 139.6, 136.2, 135.4, 131.7, 130.4, 129.4, 129.1, 128.4, 128.2,
126.7, 21.4.
2-Methylphenyl phenyl sulfide (3k):
A mixture of 1-chloro-2-methyl benzene (126 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH
o
(60 mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 C for 3 h. The reaction
mixture was filtered and the solvent evaporated in vacuo to give the crude product, which was
purified by column chromatography (hexane/ethyl acetate = 10/1) to give the title compound 3k (156
mg, 78%) as a colorless oil; [Found: C, 77.96; H, 6.13. C13H12S requires C, 77.95; H, 6.04%]; Rf = 0.4
(hexane/ethyl acetate = 10/1). 1H NMR (400 MHz, CDCl3): δ 7.32-7.22 (m, 9H), 2.38 (s, 3H).
13C NMR (100 MHz, CDCl3): δ 140.7, 136.2, 133.4, 131.3, 131.3, 128.4, 127.2, 125.2, 124.7,
123.1, 122.2, 20.5.
Phenyl benzyl sulfide (3l):
A mixture of benzyl chloride (127 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH (60
mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 1 h. The reaction
mixture was filtered and the solvent evaporated in vacuo to give the crude product, which
was purified by column chromatography (hexane/ethyl acetate = 4/1) to give the title
compound 3l (190 mg, 95%) as a colourless oil; [Found: C, 77.90; H, 6.21. C13H12S requires
1
C, 77.95; H, 6.04%]; Rf = 0.4 (hexane/ethyl acetate = 4/1). H NMR (400 MHz, CDCl3): δ

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7.36-7.30 (m, 10 H), 4.06 (s, 2H), 13C NMR (100 MHz, CDCl3): δ 139.4, 138.8, 129.9, 128.4,
128.3, 127.2, 126.9, 39.3.
Benzyl 2-nitrophenyl sulfide (3o):
A mixture of benzyl chloride (127 mg, 1 mmol), 2-nitrothiophenol (155 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 1 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 8/1) to give the title compound 3o (243 mg, 95%) as a
o
yellow solid; mp 83-84 C; [Found: C, 63.61; H, 4.59. C13H11NO2S requires C, 63.65; H, 4.52%];
Rf = 0.4 (hexane/ethyl acetate = 8/1). 1H NMR (400 MHz, CDCl3): δ 8.22 (d, J=7.2 Hz, 1H),
13
7.53-7.23 (8H, m), 4.21 (2H, s). C NMR (100 MHz, CDCl3): δ 137.7, 134.8, 133.4, 128.9,
128.7, 127.6, 126.7, 125.9, 124.6, 37.4.
4-Fluorophenyl phenyl sulfide (3p):
A mixture of chlorobenzene (112 mg, 1 mmol), 4-fluorothiophenol (128 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 2 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 30/1) to give the title compound 3p (181 mg, 89%) as a
colourless oil; [Found: C, 70.50; H, 4.41. C12H9FS requires C, 70.56; H, 4.44%]; Rf = 0.5
(hexane/ethyl acetate = 30/1). 1H NMR (400 MHz, CDCl3): δ 7.37-7.31 (m, 2H), 7.25–7.18 (m,
13
5H), 6.96 (t, J=8.5 Hz, 2H). C NMR (100 MHz, CDCl3): δ 163.2, 160.4, 136.2, 133.9,
130.0, 129.7, 129.1, 126.8, 116.5, 116.3.

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4-Chlorophenyl phenyl sulfide (3q):
A mixture of chlorobenzene (112 mg, 1 mmol), 4-chlorothiophenol (144 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 2 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 40/1) to give the title compound 3q (189 mg, 86%) as a
colourless oil; [Found: C, 65.37; H, 4.16. C12H9ClS requires C, 65.30; H, 4.11%]; Rf = 0.5
(hexane/ethyl acetate = 40/1).1H NMR (400 MHz, CDCl3): δ 7.36-7.20 (m, 9H). 13C NMR (100
MHz, CDCl3): δ 135.0, 134.7, 133.1, 132.2, 131.7, 129.4, 128.0, 127.7.
4-bromophenyl phenyl sulfide (3r):
A mixture of chlorobenzene (112 mg, 1 mmol), 4-bromothiophenol (188 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 2 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 8/1) to give the title compound 3r (222 mg, 84%) as a
colourless oil; [Found: C, 54.31; H, 3.45. C12H9BrS requires C, 54.35; H, 3.42%]; Rf = 0.6
(hexane/ethyl acetate = 8/1). 1H NMR (400 MHz, CDCl3): δ 7.41-7.20 (m, 9H). 13C NMR (100
MHz, CDCl3): δ 135.2, 134.6, 132.4, 132.04, 131.3, 129.04, 127.2.
3-Chlorophenyl phenyl sulfide (3u):
A mixture of chlorobenzene (112 mg, 1 mmol), 3-chlorothiophenol (144 mg, 1 mmol), NaOH (60
mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 2 h. The reaction mixture
was filtered and the solvent evaporated in vacuo to give the crude product, which was purified by
column chromatography (hexane/ethyl acetate = 40/1) to give the title compound 3u (194 mg, 88%)
as a colourless oil; [Found: C, 65.33; H, 4.14. C12H9ClS requires C, 65.30; H, 4.11%]; Rf = 0.4
(hexane/ethyl acetate = 40/1). 1H NMR (400 MHz, CDCl3): δ 7.41-7.15 (m, 9H).13C NMR (100
MHz, CDCl3): δ 138.9, 134.6, 134.3, 132.2, 130.7, 129.7, 129.2, 128.6, 127.3, 126.2.

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4-Methoxyphenyl phenyl sulfide (3v):
A mixture of chlorobenzene (112 mg, 1 mmol), 4-mercaptoanisole (140 mg, 1 mmol), NaOH (60 mg,
1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 oC for 3 h. The reaction mixture was
filtered and the solvent evaporated in vacuo to give the crude product, which was purified by column
chromatography (hexane/ethyl acetate = 40/1) to give the title compound 3v (160 mg, 74%) as a
colorless oil; [Found: C, 72.20; H, 5.66. C13H12OS requires C, 72.19; H, 5.59%]; Rf = 0.3
(hexane/ethyl acetate = 40/1). 1H NMR (400 MHz, CDCl3): δ 7.90 (d, J=7.4 Hz, 2H), 7.48-7.41
13
(m, 2H), 7.31– 7.23 (m, 3H), 6.94 (d, J=7.8 Hz, 2H), 3.88 (s, 3H). C NMR (100 MHz,
CDCl3): δ 160.0, 138.7, 135.2, 128.7, 127.8, 125.6, 124.0, 114.8, 55.4.
2-Acetyl-4-trifluoromethylphenylphenylsulfide (3z):
A mixture of 1-(2-chloro-5-(trifluoromethyl)phenyl) ethanone (222 mg, 1 mmol), thiophenol
(110 mg, 1 mmol), NaOH (60 mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred
at 70 oC for 2 h. The reaction mixture was filtered and the solvent evaporated in vacuo to give
the crude product, which was purified by column chromatography (hexane/ethyl acetate =
10/1) to give the title compound 3z (228 mg, 77%) as a yellow oil; [Found: C, 60.84; H, 3.71.
1
C15H11F3OS requires C, 60.80; H, 3.74%]; Rf = 0.3 (hexane/ethyl acetate = 10/1). H NMR
(400 MHz, CDCl3): δ 8.06 (d, J = 6.1 Hz, 1H), 7.74-7.68 (m, 2H), 7.53-7.45 (m, 4H), 6.71 (d,
13
J=8.3 Hz, 1H), 2.81 (s, 3H). C NMR (100 MHz, CDCl3): δ 195.3, 147.4, 134.6, 133.2,
131.2, 130.8, 130.3, 129.2, 127.6, 126.7, 125.3, 123.4, 28.0.
2-Acetyl-4-trifluoromethylphenyl4-methoxyphenylsulfide (3Aa):
A mixture of
1-(2-chloro-5-(trifluoromethyl)phenyl) ethanone (222 mg, 1 mmol), p-
thiocresol (124 mg, 1 mmol), NaOH (60 mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF
o
was stirred at 70 C for 3 h. The reaction mixture was filtered and the solvent evaporated in
vacuo to give the crude product, which was purified by column chromatography

16
ACCEPTED MANUSCRIPT
(hexane/ethyl acetate = 10/1) to give the title compound 3Aa (235 mg, 72%) as a white solid;
mp 76-78 oC; [Found: C, 58.81; H, 4.01. C16H13F3O2S requires C, 58.89; H, 4.02%]; Rf = 0.3
1
(hexane/ethyl acetate = 10/1). H NMR (400 MHz, CDCl3): δ 8.10 (s, 1H), 7.46-7.38 (m,
13
3H), 7.05 (d, J=8.4 Hz, 2H), 6.90 (d, J=8.4 Hz, 1H), 3.89 (s, 1H), 2.76 (s, 3H). C NMR
(100 MHz, CDCl3): δ 197.3, 161.8, 147.7, 136.9, 131.6, 128.8, 127.5, 126.6, 124.4, 121.7,
120.9, 115.8, 54.8, 28.0.
4-(Phenylthio)benzoic acid (3Ab):
A mixture of 4-chloro-benzoic acid (156 mg, 1 mmol), thiophenol (110 mg, 1 mmol), NaOH
o
(60 mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 C for 2 h. The
reaction mixture was filtered and the solvent evaporated in vacuo to give the crude product,
which was purified by column chromatography (hexane/ethyl acetate = 4/1) to give the title
compound 3Ab (204 mg, 89%) as a yellow solid; mp 173-174 oC; [Found: C, 67.81; H, 4.31.
C13H10O2S requires C, 67.80; H, 4.38%]; Rf = 0.2 (hexane/ethyl acetate = 4/1). 1H NMR (400
MHz, CDCl3): δ 7.92 (d, J=8.4 Hz, 2H), 7.51-7.44 (m, 2H), 7.36– 7.29 (m, 3H), 7.17 (d,
13
J=8.3 Hz, 2H). C NMR (100 MHz, CDCl3): δ 171.2, 146.0, 134.5, 131.5, 130.8, 129.2,
128.6, 127.0, 126.4.
2-Phenylsulfanylbenzoic acid methyl ester (3Ac):
A mixture of methyl-2-chloro-benzotae (170 mg, 1 mmol), thiophenol (110 mg, 1 mmol),
o
NaOH (60 mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 C for 2 h.
The reaction mixture was filtered and the solvent evaporated in vacuo to give the crude
product, which was purified by column chromatography (hexane/ethyl acetate = 20/1) to give
o
the title compound 3Ac (185 mg, 76%) as a white solid; mp 46-48 C; [Found: C, 68.81; H,
1
4.91. C14H12O2S requires C, 68.83; H, 4.95%]; Rf = 0.4 (hexane/ethyl acetate = 20/1). H
NMR (400 MHz, CDCl3): δ 8.07-7.92 (m, 1H), 7.68-7.59 (m, 2H), 7.44-7.37 (m, 3H), 7.23-
13
7.15 (m, 1H), 7.06 (t, J=7.3 Hz, 1H), 6.85 (d, J=8.2 Hz, 1H), 3.98 (s, 3H). C NMR (100

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MHz, CDCl3): δ 166.6, 143.1, 134.8, 134.4, 133.3, 132.8, 128.4, 126.3, 125.1, 124.7, 123.2,
52.8.
3-(4-tert-Butylphenyl)sulfanylphenol (3Ad):
A mixture of 3-chlorophenol (128 mg, 1 mmol), 4-tert-butylthiophenol (166 mg, 1 mmol),
o
NaOH (60 mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 C for 3 h.
The reaction mixture was filtered and the solvent evaporated in vacuo to give the crude
product, which was purified by column chromatography (hexane/ethyl acetate = 10/1) to give
the title compound 3Ad (168 mg, 65%) as a colorless oil; [Found: C, 74.41; H, 7.01.
1
C16H18OS requires C, 74.38; H, 7.02%]; Rf = 0.2 (hexane/ethyl acetate = 10/1). H NMR
(400 MHz, CDCl3): δ 7.37-7.27 (m, 2H), 7.12 (t, J=8.1 Hz, 1H), 7.02 (t, J=8.1 Hz, 1H), 6.88-
13
6.79 (m, 1H), 6.69-6.65 (m, 1H), 6.52-6.47 (m, 2H). C NMR (100 MHz, CDCl3): δ 156.9,
132.5, 131.6, 131.2, 129.4, 128.7, 127.4, 117.7, 114.2, 112.3, 34.5, 31.4.
4-(3,5-Dimethylphenyl)sulfanylphenol (3Ae):
A mixture of 5-chloro-1,3-xylene (140 mg, 1 mmol), 4-mercaptoophenol (126 mg, 1 mmol),
o
NaOH (60 mg, 1.5 mmol) and 5 mol % NiL2 (38 mg) in DMF was stirred at 70 C for 3 h.
The reaction mixture was filtered and the solvent evaporated in vacuo to give the crude
product, which was purified by column chromatography (hexane/ethyl acetate = 10/1) to give
the title compound 3Ae (156 mg, 68%) as a colorless oil; [Found: C, 73.06; H, 6.11.
1
C14H14OS requires C, 73.01; H, 6.13 %]; Rf = 0.3 (hexane/ethyl acetate = 10/1). H NMR
13
(400 MHz, CDCl3): δ 7.46-7.40 (m, 2H), 6.87-6.79 (m, 5H), 4.81 (s, 1H), 2.27 (s, 6H). C
NMR (100 MHz, CDCl3): δ 155.4, 138.1, 134.8, 133.6, 127.8, 126.7, 116.7, 21.3.
Acknowledgements:
Authors acknowledges Director of NIT Silchar and CSIR, New Delhi for financial support,
and SAIF of IIT Bombay and Gauhati University, India for extending the facilities for
characterization of the samples and XRD analysis respectively.

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Supplementary data:
Supplementary data associated with this article can be found, in the online version, at
http://dx.doi.org................
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SUPPORTING INFORMATION
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Nickel-Schiff base complex catalyzed C-S cross-coupling of thiols with organic chlorides
Prasanta Gogoi,a Sukanya Hazarika,a Manas J. Sarma,b Kuladip Sarma,a and Pranjit Barmana*
aDepartment of Chemistry, National Institute of Technology, Silchar 788010, Assam, India
bDepartment of Chemistry, Gauhati University, Guwahati 781014, Assam, India
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X-ray crystal structure for 3o: (The following crystal structure has been deposited at the Cambridge Crystallographic
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Data Centre and has the deposition number CCDC 1018005)
Figure S1. Thermal ellipsoidal plot of compound 3o with atom labeling scheme. Displacement ellipsoids are drawn at
50% probability level except for the H atoms, which are shown as circles of arbitrary radius.
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