Br?nsted Acid-Assisted Zinc-Catalyzed Markovnikov-Type Hydrothiolation of Alkenes Using Thiols

Article abstract of DOI:10.1021/acs.joc.0c00487

The zinc-catalyzed regioselective hydrothiolation of alkenes with thiols was achieved in the presence of 4-toluenesulfonic acid. Through this procedure, Markovnikov-type sulfides were synthesized in excellent yields, and the formation of anti-Markovnikov-

Full text of DOI:10.1021/acs.joc.0c00487

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Article
Brønsted Acid-Assisted Zinc-Catalyzed Markovnikov-
Type Hydrothiolation of Alkenes Using Thiols
Nobukazu Taniguchi
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c00487 • Publication Date (Web): 20 Apr 2020
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Brønsted Acid-Assisted Zinc-Catalyzed
Markovnikov-Type Hydrothiolation of Alkenes
Using Thiols
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Nobukazu Taniguchi*
aDepartment of Chemistry, Fukushima Medical University, Fukushima 960-1295, Japan
taniguti@fmu.ac.jp
R3SH,
SR3
R2
cat.ZnI2, TsOH
R2
R1
R1
96-48%
R1 = Aryl
CH2Cl2, rt
R2 = H or Akyl
Regioselectivity
Abstract
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The zinc-catalyzed regioselective hydrothiolation of alkenes with thiols was achieved in
the presence of 4-toluenesulfonic acid. Through this procedure Markovnikov-type sulfides
were synthesized in excellent yields, and the formation of anti-Markovnikov-type sulfides
was suppressed. Furthermore, the combination of numerous aryl alkenes with arenethiols
or alkyl thiols was achieved using the procedure.
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Introduction
Transition metal-catalyzed reactions involving carbonsulfur bond formation are
important in organic syntheses.1,2 Among them, the catalytic hydrothiolation of alkenes
has been extensively researched. The procedure reported herein generally involves a
radical process and the production of anti-Markovnikov-type products in excellent yields
(Scheme 1).3 Conversely, the research on the catalytic Markovnikov-type hydrothiolation
reaction is very restricted,4,5 although a stoichiometric reaction has been developed.6,7
Some reactions are exploited as follows (Scheme 2). The reaction of alkyl alkenes with
alkyl thiols has been achieved over an indium catalyst.4a-c The hydrothiolation of vinyl
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ethers or vinyl pyrrolidone has been achieved using a Pd(OAc)2 or Cu(OAc)2 catalyst.4d,e
In addition, a montmorillonite K10 can be employed to catalyze the reactions of various
substrates, although the regioselectivity of the reaction cannot be satisfactorily
controlled.4f These catalytic methods afford excellent yields when alkyl alkenes or alkyl
thiols are employed. Regrettably, the combination of aryl alkenes and arenethiols
preferentially affords anti-Markovnikov-type products.
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It is commonly known that the formation of thiyl radicals from arenethiols occurs at a
much faster rate than that of alkyl thiols. The reaction involving arenethiols tends to afford
anti-Markovnikov products via a radical pathway.8 To achieve a Markovnikov-type
reaction, the generation of thiyl radicals must be suppressed (Figure 1). To solve this
problem, a metal catalyst that can suppress the generation of thiyl radicals or act as a -
π
acid is required.3a,9 Fortunately, the zinc-catalyzed hydrothiolation of alkenes can afford
Markovnikov type products regioselectively in excellent yields in the presence of 4-
toluenesulfonic acid. The methodology will be described in this article.
Scheme 1. Reaction of alkenes with arenethiols
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ArSH, cat.LA
R1
SAr
R1
1
2
via Radical reaction
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Scheme 2. Hydorothiolation of alkenes via a non-radical reaction
Alkyl-SH
SAlkyl
In(OTf)3(5 mol%)
Alkyl
Alkyl
2A
88-58%
1A
AreneSH or AlkylSH,
Pd(OAc)2 or Cu(OAc)2
(5 mol%)
SR
AlkylO
AlkylO
1B
2B
95-39%
SR2
R2SH or R2COSH,
Mont K 10 (10% wt)
SR2
+
R1
R1
R1
2
3
1
96-22%
branch/linear = 31/59-2/83
R1 = Aryl or Alkyl
Figure 1. Strategy for hydorothiolation of alkenes
m-X
ArS-m
ArSH
ArS
C
B
A
R1
R1
1
1
SAr
SAr
R1
R1
3
2
Results and Discussion
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To establish optimum reaction conditions, a ZnI2-catalyzed reaction using styrene with
4-toluenethiol was conducted in air (Table 1). When the reaction was initially examined in
CH2Cl2 or PhMe, an anti-Markovnikov-type product 3aa was selectively produced without
the formation of a Markovnikov-type sulfide 2aa (Entries 1 and 2). The addition of 4-
toluenesulfonic acid monohydrate (0.3 mmol) at 100 ºC or 80 ºC in toluene or benzene
facilitated the production of the expected sulfide 2aa regioselectively, although in low
yields (Entries 3 and 4). Notably, when the reaction was performed at room temperature
in dichloromethane, the yield increased to 95% without the formation of 3aa and 4aa
(Entry 5). Furthermore, the use of 0.5 equiv. of TsOH∙H2O provided similar results (Entry
6). The reaction under nitrogen atmosphere in the dark afforded same result (Entry 7).
However, the reaction under oxygen atmosphere could not promote Markovnikov-type
reaction owing to the formation of hydroxysulfide 4aa (Entry 8). The use of MsOH or
MsOH and water afforded same result (Entries 9 and 10). These results indicate that
water is not required for the promoting the reaction. Contrarily, other acids or zinc
catalysts could not promote the reaction satisfactorily except for ZnBr2 (Entries 1117).
Similarly, other metal catalysts were then researched. The reaction using FeBr3 could
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produce 2aa in 93% yield whereas the using AlCl3 or CuI promoted anti-Markovnikov-
type reaction (Entries 1820).
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Table 1. Investigation of suitable conditionsa
4-MeC6H4SH,
SC6H4Me-4
ZnI2, additive
SC6H4Me-4
+
Ph
Ph
Ph
solv.
1aa
2aa
3aa
OH
SC6H4Me-4
+
Ph
4aa
Entry
Additive/solvent
ZnX2
The ratio
2aa
(%)
ºC
of
2aa/3aa/
4aab
1
2
None/CH2Cl2
None/PhMe
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
ZnI2
rt
rt
0/100/0
0/100/0
95/5/0
95/5/0
100/0/0
98/1/1
99/1/0
1/98/1
99/1/0
99/1/0
54/3/43
47/53/0
-
0
0
3
TsOH∙H2O/PhMe
TsOH∙H2O/PhH
TsOH∙H2O/CH2Cl2
TsOH∙H2O/CH2Cl2
TsOH∙H2O/CH2Cl2
TsOH∙H2O/CH2Cl2
MsOH /CH2Cl2
100
80
rt
40
45
95
94
93
0
4
5
6c
rt
7c,d
8c,e
9c,f
10c,f,g
11c,h
12c
13c
14c
rt
rt
rt
92
90
38
35
0i
MsOH/H2O/CH2Cl2
CSA/CH2Cl2
rt
rt
CF3CO2H/CH2Cl2
HCl(36% aq)/CH2Cl2
AcOH/CH2Cl2
rt
rt
rt
0/100/0
0
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15c
16c
17c
18c
19c
20c
TsOH∙H2O/CH2Cl2
ZnCl2
ZnBr2
Zn(OAc)2
FeBr3
rt
rt
rt
rt
rt
rt
3/83/4
74/11/15
-
trace
73
TsOH∙H2O/CH2Cl2
TsOH∙H2O/CH2Cl2
TsOH∙H2O/CH2Cl2
TsOH∙H2O/CH2Cl2
TsOH∙H2O/CH2Cl2
trace
93
100/0/0
0/86/24
0/85/25
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AlCl3
trace
trace
CuI
aReaction condition: A mixture of 1 (0.3 mmol), RSH (0.33 mmol), additive (0.3 mmol) and ZnI2
or MXn (10 mol%) in the solvent. (0.3 mL) was treated. bDetermined by 1H NMR. c0.5 equiv. of
d
e
acid was used. The reaction was performed under N2 in the dark. The reaction was performed
f
g
under O2. MsOH is methanesulfonic acid. 0.5 equiv. of H2O was added. hCSA is
camphorsulfonic acid. iHydrochloride derivative was obtained in 21% yield.
On the basis of the developed procedure, numerous substrates were then screened
(Table 2). Initially, reactions between styrene and various arenethiols were conducted
and the expected sulfides were obtained regioselectively in excellent yields. From these
reactions, trace amounts of -hydroxysulfides were also produced. On the contrary, when
the reaction was conducted using 4-methoxybenzene thiol, the yield decreased to 25%
yield owing to the generation of -hydroxysulfides and linear sulfides. However, the using
CSA instead of TsOH was increased to 48% yield. The reaction produced good results
even with alkyl thiols and heteroaryl thiols. Although various aryl alkenes afforded
excellent results, 4-trifluoromethylstyrene exhibited a relatively low reactivity. Moreover,
the reaction involving 2-naphthylstyrene, -methylstyrene and vinyl pyrrolidinone afforded
the corresponding products regioselectively in good results. The hydrothiolation of vinyl
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ether proceeded smoothly, however an unexpected dithioacetal was produced in 42%
yield. Regrettably, alkyl alkenes exhibited low reactivities, and disulfides were formed.
Similarly, internal alkenes can be employed in the reaction. As shown in Table 3, the
employed aryl alkenes afforded the desired products regioselectively in excellent yields.
However, the reaction of alkyl alkenes such as cyclohexene, 2-methyl-1-hexene, and 1-
methyl-1-cyclohexene was not promoted. On the other hand, The reaction of methyl
acrylate or (E)-methyl but-2-enoate gave only 1,4-addacts in 93% or 12% yield without the
production of other compounds.
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Table 2. Zn-catalyzed hydrothiolation of terminal alkenesa
R3SH,
ZnI2 (10 mol%),
SR3
TsOH·H2O
R1
R1
CH2Cl2, rt, 18 h
1
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SAr
SC6H4Me-4
5
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R
b
2aa
Ar = 4-MeC6H4
2ab
:94%(99/1)
b
2ba
R = Me
: 79%(91/9)
b,c
C6H5
: 87%(100/0)
b
2ca
MeO
: 72%(100/0)
b,e,f
2ac
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4-MeOC6H4
: 48%(100/0)
b
2da
Cl
: 93%(100/0)
25%(100/0)b,f
b
2ea
F
: 83%(100/0)
b
2ad
4-BrC6H4
4-ClC6H4
: 79%(99/1)
b,c
2ma
F3C
: trace(100/0)
b
2ae
: 52%(100/0)
b,c
2af
4-F3CC6H4
2-MeC6H4
: 69%(100/0)
SC6H4Me-4
b
2ag
: 85%(100/0)
b,e,f
2ah
2-MeOC6H4
: 93%(100/0)
31%(100/0)b,f
b,c
b
fa
2
: 70%(93/7)
2ai
2-BrC6H4
: 95%(100/0)
: 66%(100/0)
b,c
2aj
2-Naphtyl
SC6H4Me-4
SAlkyl
b
ga
2
: 89%(100/0)
b
2ak
Alkyl = nBu
: 93%(100/0)
SC6H4Me-4
O
b
2al
nOctyl
: 91%(100/0)
N
b
2am
PhCH2
: 96%(100/0)
b
ha
: 93%(100/0)
2
X
N
SC6H4Me-4
S
Alkyl
g
2na
Alkyl = nBuO
: trace
b
2an
2ao
X = O
S
: 75%(100/0)
2oa
PhCH2
: trace
: 0%
b
: 70%(100/0)
2pa
nBu
aReaction condition: A mixture of 1 (0.3 mmol), thiol (0.33 mmol), TsOH∙H2O (0.15 mmol), and
ZnI2 (10 mol%) in CH2Cl2 (0.15 mL) was treated at room temperature. bThe ratio of regioisomers
(branch/linear) is shown. This is determined by 1H NMR. cTsOH∙H2O (0.3 mmol) was used. d2-
e
Hexanol was obtained. CSA (0.3 mmol) instead of TsOH∙H2O was used in CH2Cl2 (0.5 mL).
hThe reaction was performed for 40 h. gDithioacetal was obtained in 42% yield.
Table 3. Zn-catalyzed hydrothiolation of internal alkenesa
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R3SH,
ZnI2 (10 mol%),
SR3
TsOH·H2O
R2
R1
R1
R2
1
CH2Cl2, rt
2
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SC6H4Me-4
R
SAlkyl
b
b
2ai
2aj
2ik
R = Me
Ph
: 90%(100/0) (18 h) Alkyl = nBu
: 70%(100/0) (18 h)
b
b
2im
: 72%(100/0) (36 h)
SC6H4Me-4
Bn
: 88%(100/0) (18 h)
SC6H4Me-4
Ph
b
la
2 : 55% (18 h)
ja
2 : 76%(98/2) (18 h)
SC6H4Me-4
SC6H4Me-4
b
qa
: trace (18 h)
2
ka
2
: 92%(98/2) (18 h)
SC6H4Me-4
SC6H4Me-4
ra
2
: 0% (18 h)
sa
2
: 0% (18 h)
SC6H4Me-4
R
MeO2C
c
ta
R = H 2 : 0% (18 h)
d
ua
Me 2 : 0% (18 h)
aReaction condition: A mixture of 1 (0.3 mmol), thiol (0.33 mmol) and ZnI2 (10 mol%) in CH2Cl2
(0.15 mL) was treated at room temperature. bThe ratio of regioisomers is shown as determined by
1H NMR. c1,4-addact was obtained in 93% yield. d1,4-addact was obtained in 12% yield.
To elucidate the reaction mechanism, we investigated whether the reaction proceeds
via a radical or non-radical pathway. When the reaction was carried out in the presence
of BHT as a radical scavenger, the corresponding sulfide was produced in 89% yield
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without the formation of other products (Scheme 3). The result indicates that the
hydrothiolation proceeds via non-radical process. Afterward, the role of the zinc catalyst
was investigated (Scheme 4). The reaction using 4-toluenesulfonic acid in the absence
of the zinc catalyst could not afford the Markovnikov-type sulfide, and the anti-
Markovnikov-type sulfide was obtained in 58% yield. In addition, the zinc-catalyzed
reaction in the absence of 4-toluenesulfonic acid afforded only linear alkyl sulfides
(Entries 1 and 2, Table 1). These results show that both of the zinc-catalyst and 4-
toluenesulfonic acid are required for the promotion of the Markovnikov-type
hydrothiolation. To investigate the role of iodide ion, the reaction using NH4X (X = I and
Cl, 20 mol%) in the absence of zinc catalyst was examined (Scheme 5). The reaction
using NH4I could not promote both Markovnikov and anti-Markovnikov-type reaction,
whereas the using NH4Cl promoted anti-Markovnikov-type reaction. Therefore, it seems
that the using of ZnI2 is superior to other zinc salts. Then, the reaction of ZnI2 with thiol in
the absence of alkene was examined (Scheme 6). When the mixture of ZnI2 (20 mol%),
4-toluenethiol and TsOH in the absence of styrene was stirred for 1 h, the colorless
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solution including precipitates changed to yellow solution. It seems that iodide ion and
RS-ZnX complex is produced.
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From these experiments, a plausible mechanism is considered as follows (Figure 2).
Arenethiyl radicals B are easily produced under various conditions.10 However, the
presence of both TsOH and ZnI2 suppresses the formation of thiyl radicals B, and
facilitates the facile production of the zinc-sulfide complex. Sequentially, the obtained
complex reacts with an alkene, and a zinc intermediate 2C is produced. Finally, the
intermediate 2C is immediately converted into the expected sulfides 2 by protonation,
thereby suppressing the formation of linear alkyl sulfides.
Furthermore, the dihydrothiolation of 1-butyl vinyl ether using 2 equiv. of 4-toluenethiol
was performed (Scheme 7).4e This reaction afforded the corresponding dithioacetal 6
regioselectively in 94% yield.
Finally, a gram-scale reaction was attempted (Scheme 8). When the reaction of styrene
with 4-toluenethiol or 1-butanethiol was conducted over a ZnI2 catalyst in the presence of
4-toluenesulfonic acid, the expected branched alkylsulfides 2aa and 2ak were produced
regioselectively in excellent yields.
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Scheme 3. Zn-catalyzed hydrothiolation in the presence of BHT
8
9
4-MeC6H4SH,
ZnI2 (10 mol%),
TsOH·H2O
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SC6H4Me-4
BHT (1.0 equiv.)
SC6H4Me-4
+
Ph
Ph
Ph
1aa
CH2Cl2, rt, 18 h
3aa
Not observed
2aa
%
89
Scheme 4. Hydrothiolation in the presence of TsOH
4-MeC6H4SH,
TsOH·H2O
SC6H4Me-4
SC6H4Me-4
3aa
+
Ph
Ph
Ph
CH2Cl2, rt, 18 h
2aa
0%
1a
58%
OH
SC6H4Me-4
+
Ph
4aa
5%
Scheme 5. Hydrothiolation in the absence of Zn
4-MeC6H4SH,
NH4X (20 mol%)
TsOH·H2O
2aa
0%
0%
4aa
trace
trace
5aa
14%
0%
3aa
9%
70%
+
+
+
Ph
CH2Cl2, rt, 18 h
X = I:
Cl:
1a
SC6H4Me-4
SC6H4Me-4
Ph
5aa
Scheme 6. A reaction of thiol with ZnI2
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4-MeC6H4SH,
TsOH·H2O
ZnI2
(20 mol%)
Yellow solution
CH2Cl2, rt, 1h
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Figure 2. Plausible reaction mechanism
O2,
ArS-ZnI
ArSH
(or light)
ArS
C
A
B
H+
ArS
A'
R1
ZnI2
HI
R1
1
1
SAr
SAr
SAr
R1
ZnI
Fast
R1
R1
3B
2
2C
Scheme 7. Dihydrothiolation of vinyl ether
2x4-MeC6H4SH,
ZnI2(10 mol%),
SC6H4Me-4
TsOH·H2O
SC6H4Me-4
nBuO
CH2Cl2, rt, 18 h
6
7
94%
Scheme 8. Gram-scale reaction
RSH,
ZnI2(10 mol%)
TsOH·H2O
SR
Ph
Ph
CH2Cl2, rt, 18 h
1a
2aa
R = 4-MeC6H4
: 2.07 g (91%)
1.04 g
(10 mmol)
2ak
nBu
: 1.73 g (89%)
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In conclusion, the zinc-catalyzed hydrothiolation of alkenes afforded Markovnikov-type
products in excellent yields. The reaction proceeded efficiently in the presence of 4-
toluenesulfonic acid. Numerous arenethiols or alkyl thiols were available. Furthermore,
the method could be applied to the synthesis of dithioacetals from vinyl ethers or the
gram-scale reaction.
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Experimental Section
General Procedure and Chemicals. All reactions were carried out in air. 1H and 13C NMR
spectra were recorded at 270 and 67.8 MHz, respectively. Chemical shifts are reported
in  ppm referenced to an internal tetramethylsilane standard for 1H NMR and chloroform-
d ( 77.0) for 13C NMR.
Typical procedure for zinc-catalyzed hydorthiolation of alkenes: Synthesis of 1-Phenyl-1-
(4-methylphenylthio)ethane (2aa) (Table 2, entry 1)
To a mixture of styrene (31.2 mg, 0.3 mmol), 4-Toluenethiol (41.0 mg, 0.33 mmol), and 4-
Toluenesulfonic acid monohydrate (28.5 mg, 0.15 mmol) in CH2Cl2 (0.3 mL), ZnI2 (9.6 mg, 0.03
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mmol) was added, and the mixture was stirred at room temperature for 18 h in air. After the residue
was dissolved in Et2O, the solution was washed with H2O and saturated sodium chloride and dried
over anhydrous magnesium sulfate. Chromatography on silica gel (hexane) gave 1-Phenyl-1-(4-
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1
methylphenylthio)ethane 2aa (64.0 mg, 94%)4f: Colorless oil; H NMR (270 MHz, CDCl3) 
7.27–7.17 (m, 7H, Ar-H), 7.02 (d, J = 8.2 Hz, 2H, Ar-H), 4.26 (q, J = 7.0 Hz, 1H, CH), 2.28
(s, 3H, Ar-CH3), 1.60 (d, J = 7.0 Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)  143.3,
137.3, 133.2, 131.2, 129.4, 128.3, 127.3, 127.0, 48.3, 22.1, 21.1; IR (neat) 3027, 2968,
2922, 1600, 1492, 1451 cm-1; Anal. Calcd for C15H16S: C, 78.90; H, 7.06. Found: C, 79.01;
H, 7.12.
1-Phenyl-1-phenylthioethane (2ab): The title compound was obtained as a colorless oil
(56.1 mg, 87%).1H NMR (270 MHz, CDCl3)  7.31–7.17 (m, 10H, Ar-H), 4.33 (q, J = 7.0
Hz, 1H, CH), 1.62 (d, J = 7.0 Hz, 3H, CH3); C{1H} NMR (67.8 MHz, CDCl3)  143.2,
13
135.1, 132.5, 128.6, 128.4, 127.2, 127.1, 127.0, 48.0, 22.3; IR (neat) 3060, 3028, 2968,
1583, 1480, 1451, 1025 cm-1; Anal. Calcd for C14H14S: C, 78.46; H, 6.58. Found: C, 78.68;
H, 6.53.
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1-Phenyl-1-(4-methoxyphenylthio)ethane (2ac): The title compound was obtained as a colorless
oil (35.5 mg, 48%).1H NMR (270 MHz, CDCl3)  7.28–7.17 (m, 7H, Ar-H), 6.76 (d, J = 8.2
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Hz, 2H), 4.17 (q, J = 6.7 Hz, 1H, CH), 3.77 (s, 3H), 1.59 (d, J = 6.7 Hz, 3H, CH3); 13C{1H}
NMR (67.8 MHz, CDCl3)  159.6, 143.4, 136.0, 128.2, 127.3, 127.0, 125.1, 114.2, 55.2,
49.1, 21.8; IR (neat) 3061, 2965, 2834, 1591, 1492, 1285, 1246, 1172 cm-1; Anal. Calcd
for C15H16OS: C, 73.73; H, 6.60. Found: C, 73.90; H, 6.70.
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1-Phenyl-1-(4-bromophenylthio)ethane (2ad): The title compound was obtained as a colorless
oil (69.4 mg, 79%).1H NMR (270 MHz, CDCl3)  7.33–7.18 (m, 7H, Ar-H), 7.10 (d, J = 8.5
Hz, 2H), 4.30 (q, J = 7.0 Hz, 1H, CH), 1.61 (d, J = 7.0 Hz, 3H, CH3); 13C{1H} NMR (67.8
MHz, CDCl3)  142.8, 134.2, 134.0, 131.7, 128.4, 127.3, 127.2, 121.3, 48.1, 22.2; IR
(neat) 3028, 2969, 2924, 1492, 1471, 1384, 1091 cm-1; Anal. Calcd for C14H13BrS: C,
57.35; H, 4.47. Found: C, 57.52; H, 4.53.
1-Phenyl-1-(4-chlorophenylthio)ethane (2ae): The title compound was obtained as a colorless
oil (38.4 mg, 52%).1H NMR (270 MHz, CDCl3)  7.27–7.17 (m, 9H, Ar-H), 4.29 (q, J = 7.0
13
Hz, 1H, CH), 1.62 (d, J = 7.0 Hz, 3H, CH3); C{1H} NMR (67.8 MHz, CDCl3)  142.8,
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133.9, 133.4, 128.8, 128.4, 127.3, 127.2, 48.3, 22.2; IR (neat) 3028, 2969, 2924, 1475,
1094 cm-1; Anal. Calcd for C14H13ClS: C, 67.59; H, 5.27. Found: C, 67.67; H, 5.33.
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1-Phenyl-1-(4-trifluoromethylphenylthio)ethane (2af): The title compound was obtained as a
colorless oil (58.4 mg, 69%).1H NMR (270 MHz, CDCl3)  7.43 (d, J = 8.2 Hz, 2H), 7.36–
7.22 (m, 7H, Ar-H), 4.45 (q, J = 7.0 Hz, 1H, CH), 1.65 (d, J = 7.0 Hz, 3H, CH3); 13C{1H}
2
NMR (67.8 MHz, CDCl3)  142.6, 140.9, 130.3, 128.6, 127.3 (d, JC-F = 20 Hz), 127.1,
125.5 (t, 1JC-F = 223 Hz), 125.4 (d, 3JC-F = 4 Hz), 125.3, 47.0, 22.6; IR (neat) 3030, 2978,
1606, 1326, 1165, 1123 cm-1; Anal. Calcd for C15H13F3S: C, 63.81; H, 4.61. Found: C,
63.62; H, 4.50.
1-Phenyl-1-(2-methylphenylthio)ethane (2ag)4f: The title compound was obtained as a colorless
oil (58.0 mg, 85%).
1-Phenyl-1-(2-methoxyphenylthio)ethane (2ah): The title compound was obtained as a colorless
oil (68.2 mg, 93%).1H NMR (270 MHz, CDCl3)  7.33–7.14 (m, 7H, Ar-H), 6.79 (t, J = 7.6
Hz, 2H, Ar-H), 4.48 (q, J = 7.0 Hz, 1H, CH), 3.84 (s, 3H, OCH3), 1.62 (d, J = 7.0 Hz, 3H,
CH3); 13C{1H} NMR (67.8 MHz, CDCl3)  158.5, 143.3, 133.3, 128.4, 128.2, 127.2, 126.9,
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123.2, 120.7, 110.5, 55.7, 45.5, 22.2; IR (neat) 3061, 2965, 2834, 1581, 1476, 1271 cm-
1; Anal. Calcd for C15H16OS: C, 73.73; H, 6.60. Found: C, 73.95; H, 6.65.
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1-Phenyl-1-(2-bromophenylthio)ethane (2ai): The title compound was obtained as a colorless
oil (83.7 mg, 95%).1H NMR (270 MHz, CDCl3)  7.53 (d, J = 7.9 Hz, 1H, Ar-H), 7.36 (d, J
= 8.2 Hz, 1H, Ar-H), 7.297.17 (m, 5H, Ar-H), 7.11 (t, J = 7.9 Hz, 1H, Ar-H), 6.99 (t, J =
8.2 Hz, 1H, Ar-H), 4.73 (q, J = 7.0 Hz, 1H, CH), 1.65 (d, J = 7.0 Hz, 3H, CH3); 13C{1H}
NMR (67.8 MHz, CDCl3)  142.5, 136.7, 133.0, 132.2, 128.5, 127.8, 127.5, 127.3, 127.2,
126.2, 46.7, 22.3; IR (neat) 3059, 3027, 2969, 1557, 1491, 1448, 1106 cm-1; Anal. Calcd
for C14H13BrS: C, 57.35; H, 4.47. Found: C, 57.39; H, 4.57.
1-Phenyl-1-(2-naphthylthio)ethane (2aj): The title compound was obtained as a colorless oil
1
(52.0 mg, 66%). Mp 59.5-60.0 C; H NMR (270 MHz, CDCl3)  7.77–7.66 (m, 4H, Ar-H),
7.46–7.20 (m, 8H, Ar-H), 4.45 (q, J = 7.0 Hz, 1H, CH), 1.66 (d, J = 7.0 Hz, 3H, CH3);
13C{1H} NMR (67.8 MHz, CDCl3)  143.1, 133.5, 132.6, 132.2, 131.0, 129.7, 128.4, 128.1,
127.6, 127.4, 127.3, 127.2, 126.3, 126.0, 47.9, 22.3; IR (CHCl3) 3056, 3012, 1588, 1499,
1452, 1216 cm-1; Anal. Calcd for C18H16S: C, 81.77; H, 6.10. Found: C, 81.62; H, 6.12.
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1-Phenyl-1-(1-butylthio)ethane (2ak): The title compound was obtained as a colorless oil (54.1
mg, 93%).1H NMR (270 MHz, CDCl3)  7.36–7.20 (m, 5H, Ar-H), 3.94 (q, J = 7.0 Hz, 1H,
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CH), 2.34–2.24 (m, 2H, CH2), 1.56 (d, J = 7.0 Hz, 3H, CH3), 1.53–1.38 (m, 2H, CH2),
1.38–1.27 (m, 2H, CH2), 0.84 (t, J = 7.2 Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3) 
144.2, 128.4, 127.2, 126.9, 44.0, 31.4, 30.9, 22.6, 22.0, 13.6; IR (CHCl3) 2959, 2927,
1602, 1491, 1451, 1373, 1217 cm-1; Anal. Calcd for C12H18S: C, 74.17; H, 9.34. Found:
C, 73.88; H, 9.28.
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1-Phenyl-1-(1-octylthio)ethane (2al): The title compound was obtained as a colorless oil (68.3
mg, 91%).1H NMR (270 MHz, CDCl3)  7.36–7.19 (m, 5H, Ar-H), 3.94 (q, J = 7.0 Hz, 1H,
CH), 2.38–2.21 (m, 2H, CH2), 1.57 (d, J = 7.0 Hz, 3H, CH3), 1.48–1.43 (m, 2H, CH2),
1.31–1.22 (m, 10H, CH2), 0.87 (t, J = 6.8 Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)
 144.2, 128.4, 127.2, 126.9, 44.0, 31.8, 31.3, 29.3, 29.1, 28.9, 22.6, 22.5, 14.1; IR (neat)
2925, 2854, 1602, 1491, 1452, 1372, 1220, 1026 cm-1; Anal. Calcd for C16H26S: C, 76.73;
H, 10.46. Found: C, 76.77; H, 10.48.
1-Phenyl-1-benzylthioethane (2am): The title compound was obtained as a colorless oil (65.6
mg, 96%).1H NMR (270 MHz, CDCl3)  7.33–7.18 (m, 10H, Ar-H), 3.80 (q, J = 7.0 Hz, 1H,
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CH), 3.48 (dd, J = 29.0 and 13.5 Hz, 2H, CH2), 1.53 (d, J = 7.0 Hz, 3H, CH3); C{1H}
NMR (67.8 MHz, CDCl3)  143.8, 138.4, 128.9, 128.5, 128.4, 127.4, 127.0, 126.8, 43.5,
35.7, 25.5; IR (neat) 3027, 2966, 1601, 1492, 1452, 1222 cm-1; Anal. Calcd for C16H16S:
C, 79.95; H, 6.71. Found: C, 79.67; H, 7.05.
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1-Phenyl-1-benzoxazolylthioethane (2an)6e: The title compound was obtained as a colorless oil
(57.5 mg, 75%).
1-Phenyl-1-benzothiazolylthioethane (2ao): The title compound was obtained as a colorless oil
(56.8 mg, 70%).1H NMR (270 MHz, CDCl3)  7.90 (d, J = 8.6 Hz, 1H, Ar-H), 7.72 (d, J =
8.6 Hz, 1H, Ar-H), 7.49–7.23 (m, 7H, Ar-H), 5.15 (q, J = 7.0 Hz, 1H, CH), 1.85 (d, J = 7.0
Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)  197.2, 165.8, 153.2, 141.8, 128.7, 127.8,
127.4, 126.0, 124.3, 121.7, 120.9, 47.6, 22.7; IR (CHCl3) 3061, 2969, 1455, 1426, 1238
cm-1; Anal. Calcd for C15H13NS2: C, 66.38; H, 4.83. Found: C, 66.41; H, 4.91.
1-(4-Methylphenyl)-1-(4-methylphenylthio)ethane (2ba): The title compound was obtained as
a colorless oil (57.6 mg, 79%).1H NMR (270 MHz, CDCl3)  7.22–7.16 (m, 4H, Ar-H), 7.09–
7.01 (m, 4H, Ar-H), 4.25 (q, J = 7.0 Hz, 1H, CH), 2.30 (s, 3H, CH3), 2.29 (s, 3H, CH3),
1.58 (d, J = 7.0 Hz, 3H, CH3); C{1H} NMR (67.8 MHz, CDCl3)  140.3, 137.2, 136.6,
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133.0, 131.5, 129.4, 129.0, 127.1, 48.0, 22.3, 21.1, 21.0; IR (CHCl3) 2969, 2921, 1513,
1492, 1446, 1209, 1018 cm-1; Anal. Calcd for C16H18S: C, 79.29; H, 7.49. Found: C, 79.27;
H, 7.54.
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1-(4-Methoxyphenyl)-1-(4-methylphenylthio)ethane (2ca): The title compound was obtained as
a colorless oil (55.7 mg, 72%). Mp 55.8-56.5 ̊
C; 1H NMR (270 MHz, CDCl3)  7.25–7.18 (m,
4H, Ar-H), 7.04 (d, J = 8.2 Hz, 2H, Ar-H), 6.80 (d, J = 8.5 Hz, 2H, Ar-H), 4.25 (q, J = 7.0
Hz, 1H, CH), 3.78 (s, 3H, OCH3), 2.30 (s, 3H, CH3), 1.58 (d, J = 7.0 Hz, 3H, CH3); 13C{1H}
NMR (67.8 MHz, CDCl3)  158.5, 137.2, 135.4, 133.1, 131.4, 129.4, 128.3, 113.7, 55.2,
47.7, 22.3, 21.1; IR (CHCl3) 3019, 2969, 1610, 1511, 1492 cm-1; Anal. Calcd for
C16H18OS: C, 74.38; H, 7.02. Found: C, 74.37; H, 7.01.
1-(4-Chlorophenyl)-1-(4-methylphenylthio)ethane (2da): The title compound was obtained as
a colorless oil (73.5 mg, 93%).1H NMR (270 MHz, CDCl3)  7.23–7.14 (m, 6H, Ar-H), 7.03
(d, J = 7.9 Hz, 2H, Ar-H), 4.22 (q, J = 7.0 Hz, 1H, CH), 2.29 (s, 3H, CH3), 1.57 (d, J = 7.0
Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)  142.0, 137.6, 133.4, 132.5, 130.7, 129.5,
128.6, 128.4, 47.7, 22.0, 21.1; IR (neat) 2970, 2922, 1491, 1091 cm-1; Anal. Calcd for
C15H15ClS: C, 68.56; H, 5.75. Found: C, 68.55; H, 5.80.
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1-(4-Fluorophenyl)-1-(4-methylphenylthio)ethane (2ea): The title compound was obtained as a
colorless oil (61.4 mg, 83%).1H NMR (270 MHz, CDCl3)  7.23–7.14 (m, 4H, Ar-H), 7.02 (d,
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J = 7.9 Hz, 2H, Ar-H), 6.93 (d, J = 8.7 Hz, 2H, Ar-H), 4.23 (q, J = 7.0 Hz, 1H, CH), 2.29
(s, 3H, CH3), 1.58 (d, J = 7.0 Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)  161.6 (d,
JC-F = 244.8 Hz), 139.1 (d, JC-F = 3.4 Hz), 137.5, 133.4, 130.9, 129.5, 128.8 (d, JC-F = 7.8
Hz), 115.0 (d, JC-F = 21.7 Hz), 47.6, 22.2, 21.1; IR (neat) 3018, 2974, 2925, 1603, 1508,
1218, 1158 cm-1; Anal. Calcd for C15H15FS: C, 73.14; H, 6.14. Found: C, 73.22; H, 6.19.
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1-(2-Naphtyl)-1-(4-methylphenylthio)ethane (2fa): The title compound was obtained as a
colorless solid (58.1 mg, 70%). Mp 63.9-64.5 ̊
C; 1H NMR (270 MHz, CDCl3)  7.79–7.71 (m,
3H, Ar-H), 7.59 (s, 1H, Ar-H), 7.547.50 (m, 1H, Ar-H), 7.467.39 (m, 2H, Ar-H),
7.227.17 (m, 2H, Ar-H), 6.99 (d, J = 7.9 Hz, 2H, Ar-H), 4.22 (q, J = 7.0 Hz, 1H, CH), 2.26
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(s, 3H, CH3), 1.69 (d, J = 7.0 Hz, 3H, CH3); C{1H} NMR (67.8 MHz, CDCl3)  140.7,
137.4, 133.2, 133.1, 132.6, 131.1, 129.4, 128.1, 127.8, 127.6, 126.0, 125.8, 125.7, 125.6,
48.6, 22.2, 21.1; IR (CHCl3) 3018, 2973, 1600, 1492 cm-1; Anal. Calcd for C19H18S: C,
81.97; H, 6.52. Found: C, 81.73; H, 6.51.
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2-Methyl-1-phenyl-1-(4-methylphenylthio)ethane (2ga): The title compound was obtained as a
colorless oil (65.1 mg, 89%).1H NMR (270 MHz, CDCl3)  7.41 (d, J = 8.2 Hz, 2H, Ar-H),
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7.30–7.19 (m, 3H, Ar-H), 7.03 (d, J = 8.2 Hz, 2H, Ar-H), 6.98 (d, J = 8.2 Hz, 2H, Ar-H),
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2.29 (s, 3H, CH3), 1.67 (s, 6H, CH3); C{1H} NMR (67.8 MHz, CDCl3)  146.5, 138.6,
136.6, 129.3, 129.0, 127.8, 126.6, 126.4, 50.7, 29.6, 21.2; IR (neat) 2967, 2921, 1598,
1492, 1447, 1129 cm-1; Anal. Calcd for C16H18S: C, 79.29; H, 7.49. Found: C, 79.37; H,
7.48.
1-[(1-Phenylthio)ethyl]-2-pyrrolidinone (2ha): The title compound was obtained as a colorless
oil (63.9 mg, 93%).1H NMR (270 MHz, CDCl3)  7.29 (d, J = 7.9 Hz, 2H, Ar-H), 7.08 (d, J
= 7.9 Hz, 2H, Ar-H), 5.83 (q, J = 7.0 Hz, 1H, CH), 3.643.55 (m, 1H, CH2), 3.353.27 (m,
1H, CH2), 2.30 (s, 3H, CH3), 2.272.23 (m, 1H, CH2), 2.202.03 (m, 1H, CH2), 1.961.78
(m, 2H, CH2), 1.47 (d, J = 7.0 Hz, 3H, CH3); C{1H} NMR (67.8 MHz, CDCl3)  174.4,
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137.7, 132.8, 129.5, 129.1, 54.8, 41.2, 31.1, 21.1, 18.8, 17.6; IR (neat) 2978, 1694, 1493,
1411, 1267, 1059 cm-1; Anal. Calcd for C13H17NOS: C, 66.35; H, 7.28. Found: C, 66.02;
H, 7.28.
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1-Phenyl-1-(4-methylphenylthio)propane (2ia): The title compound was obtained as a colorless
oil (65.4 mg, 90%).1H NMR (270 MHz, CDCl3)  7.28–7.13 (m, 7H, Ar-H), 7.00 (d, J = 8.2
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Hz, 2H, Ar-H), 3.97 (dd, J = 8.6 and 6.3 Hz, 1H, CH), 2.27 (s, 3H, CH3), 2.05–1.84 (m,
2H, CH2), 0.90 (t, J = 7.4 Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)  142.0, 137.1,
133.0, 131.2, 129.4, 128.2, 127.9, 126.9, 55.7, 29.2, 21.1, 12.3; IR (neat) 3026, 2964,
2930, 1491, 1451 cm-1; Anal. Calcd for C16H18S: C, 79.29; H, 7.49. Found: C, 79.34; H,
7.50.
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1,2-Diphenyl-1-(4-methylphenylthio)ethane (2ja): The title compound was obtained as a
colorless oil (65.5 mg, 72%).1H NMR (270 MHz, CDCl3)  7.22–7.08 (m, 10H, Ar-H), 7.02–
6.96 (m, 4H, Ar-H), 4.31 (dd, J = 8.9 and 6.2 Hz, 1H, CH), 3.28–3.11 (m, 2H, CH2), 2.27
(s, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)  141.3, 138.8, 137.3, 132.9, 131.2, 129.5,
129.1, 128.2, 128.1, 128.0, 127.1, 126.3, 55.5, 42.6, 21.1; IR (CHCl3) 3027, 1946, 1902,
1601, 1493, 1452, 1217 cm-1; Anal. Calcd for C21H20S: C, 82.85; H, 6.62. Found: C, 82.96;
H, 6.65.
1-Phenyl-1-(1-butylthio)propane (2ik): The title compound was obtained as a colorless oil (43.6
mg, 70%).1H NMR (270 MHz, CDCl3)  7.31–7.22 (m, 5H, Ar-H), 3.66 (dd, J = 8.6 and 6.3
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Hz, 1H, CH), 2.33–2.17 (m, 2H, CH2), 1.95–1.80 (m, 2H, CH2), 1.55–1.37 (m, 2H, CH2),
1.35–1.26 (m, 2H, CH2), 0.89 (t, J = 7.4 Hz, 3H, CH3), 0.83 (t, J = 7.2 Hz, 3H, CH3);
13C{1H} NMR (67.8 MHz, CDCl3)  142.9, 128.3, 127.9, 126.8, 51.5, 31.5, 30.7, 29.7, 22.0,
13.6, 12.4; IR (CHCl3) 3019, 1520, 1216 cm-1; Anal. Calcd for C13H20S: C, 74.94; H, 9.68.
Found: C, 74.71; H, 9.68.
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1-Phenyl-1-benzylthiopropane (2im): The title compound was obtained as a colorless oil (63.7
mg, 88%).1H NMR (270 MHz, CDCl3)  7.36–7.19 (m, 10H, Ar-H), 3.59–3.37 (m, 3H, CH
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and CH2), 1.94–1.74 (m, 2H, CH2), 0.83 (t, J = 7.2 Hz, 3H, CH3); C{1H} NMR (67.8
MHz, CDCl3)  142.4, 138.5, 128.9, 128.4, 128.3, 128.1, 127.0, 126.8, 50.9, 35.4, 29.5,
12.2 ; IR (CHCl3) 3027, 2964, 2929, 1601, 1492, 1452 cm-1; Anal. Calcd for C16H18S: C,
79.29; H, 7.49. Found: C, 79.21; H, 7.46.
1-(4-Methylphenylthio)indan (2ja): The title compound was obtained as a colorless oil (51.9 mg,
76%).1H NMR (270 MHz, CDCl3)  7.30–7.13 (m, 6H, Ar-H), 7.09 (d, J = 7.9 Hz, 2H), 4.68
(dd, J = 7.2 and 4.0 Hz, 1H, CH), 3.05–2.93 (m, 1H, CH2), 2.87–2.77 (m, 1H, CH2), 2.55–
2.41 (m, 1H, CH2), 2.32 (s, 3H, CH3), 2.32–2.14 (m, 1H, CH2); 13C{1H} NMR (67.8 MHz,
CDCl3)  143.7, 143.0, 137.0, 132.2, 132.0, 129.6, 127.6, 126.4, 124.9, 124.6, 52.4, 33.5,
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30.7, 21.1; IR (neat) 3021, 2939, 1491, 1459, 1299, 1091 cm-1; Anal. Calcd for C16H16S:
C, 79.95; H, 6.71. Found: C, 79.90; H, 6.58.
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1,2,3,4-Tetrahydro-1-(4-methylphenylthio)naphthalene (2ka): The title compound was
obtained as a colorless oil (70.1 mg, 92%).1H NMR (270 MHz, CDCl3)  7.42–7.35 (m, 3H,
Ar-H), 7.20–7.05 (m, 5H, Ar-H), 4.48 (t, J = 4.0 Hz, 1H, CH), 2.86–2.72 (m, 2H, CH2),
2.32 (s, 3H, CH3), 2.28–2.17 (m, 1H, CH2), 2.02–1.90 (m, 2H, CH2), 1.76–1.69 (m, 1H,
CH2); 13C{1H} NMR (67.8 MHz, CDCl3)  137.5, 137.2, 135.6, 132.7, 132.3, 130.5, 129.7,
129.2, 126.9, 125.6, 48.2, 29.1, 28.4, 21.1, 18.5; IR (neat) 2931, 1490, 1451, 1269, 1209
cm-1; Anal. Calcd for C17H18S: C, 80.27; H, 7.13. Found: C, 80.28; H, 7.12.
1-Phenyl-1-(4-methylphenylthio)cyclohexane (2la): The title compound was obtained as a
colorless oil (46.5 mg, 55%).1H NMR (270 MHz, CDCl3)  7.25–7.15 (m, 5H, Ar-H), 6.95–
6.85 (m, 4H, Ar-H), 2.28 (s, 3H, CH3), 2.24–2.16 (m, 2H, CH2), 2.05–1.95 (m, 2H, CH2),
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1.82–1.77 (m, 2H, CH2), 1.49–1.37 (m, 4H, CH2); C{1H} NMR (67.8 MHz, CDCl3) 
138.5, 137.0, 128.9, 128.2, 127.8, 127.0, 126.1, 55.0, 36.3, 25.9, 22.9, 21.2; IR (neat)
3019, 2935, 1492, 1447 cm-1; Anal. Calcd for C19H22S: C, 80.08; H, 7.85. Found: C, 79.83;
H, 7.80.
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Zn-catalyzed hydrothiolation in the presence of BHT (Scheme 3)
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To a mixture of styrene (31.2 mg, 0.3 mmol), 4-Toluenethiol (41.0 mg, 0.33 mmol), 4-
Toluenesulfonic acid monohydrate (28.5 mg, 0.15 mmol), and BHT (58.9 mg, 0.3 mmol) in
CH2Cl2 (0.3 mL), ZnI2 (9.6 mg, 0.03 mmol) was added, and the mixture was stirred at room
temperature for 18 h in air. After the residue was dissolved in Et2O, the solution was washed with
H2O and saturated sodium chloride and dried over anhydrous magnesium sulfate. Chromatography
on silica gel (hexane) gave 1-Phenyl-1-(4-methylphenylthio)ethane 2aa (60.8 mg, 89%).
Hydrothiolation in the presence of TsOH (Scheme 4)
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A mixture of styrene (31.2 mg, 0.3 mmol), 4-Toluenethiol (41.0 mg, 0.33 mmol), and 4-
Toluenesulfonic acid monohydrate (28.5 mg, 0.15 mmol) in CH2Cl2 (0.3 mL) was stirred at room
temperature for 18 h in air. After the residue was dissolved in Et2O, the solution was washed with
H2O and saturated sodium chloride and dried over anhydrous magnesium sulfate. Chromatography
on silica gel (5% diethyl ether / hexane) gave 1-Phenyl-2-(4-methylphenylthio)ethane 3aa (39.6
mg, 58%) and 1-Phenyl-2-(4-methylphenylthio)ethan-1-ol 4aa (3.7 mg, 5%).
Hydrothiolation in the absence of Zn (Scheme 5)
To a mixture of styrene (31.2 mg, 0.3 mmol), 4-Toluenethiol (41.0 mg, 0.33 mmol), and 4-
Toluenesulfonic acid monohydrate (58.9 mg, 0.3 mmol) in CH2Cl2 (0.3 mL), NH4X (X = I: 8.7
mg, X = Cl: 3.2 mg, 0.06 mmol) was added, and the mixture was stirred at room temperature for
18 h in air. After the residue was dissolved in Et2O, the solution was washed with H2O and
saturated sodium chloride and dried over anhydrous magnesium sulfate. The crude was separated
by Chromatography on silica gel (hexane).
A reaction of thiol with ZnI2 (Scheme 6)
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To a mixture of 4-Toluenethiol (41.0 mg, 0.33 mmol), and 4-Toluenesulfonic acid monohydrate
(58.9 mg, 0.3 mmol) in CH2Cl2 (0.3 mL), ZnI2 (9.6 mg, 0.03 mmol) was added, and the mixture
was stirred at room temperature for 1 h in air. The colorless solution changed to yellow.
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Synthesis of 1,1-di(4-methylphenylthio)ethane (Scheme 7)
To a mixture of n-butyl vinyl ether (30.0 mg, 0.3 mmol), 4-toluenethiol (78.3 mg, 0.63 mmol), and
4-toluenesulfonic acid monohydrate (28.5 mg, 0.15 mmol) in CH2Cl2 (0.3 mL) were added ZnI2
(9.6 mg, 0.03 mmol), and the mixture was stirred at room temperature for 18 h in air. After the
residue was dissolved in Et2O, the solution was washed with H2O and saturated sodium chloride
and dried over anhydrous magnesium sulfate. Chromatography on silica gel (hexane) gave 1,1-
di(4-methylphenylthio)ethane 7 (76.9 mg, 94%)5e: Colorless oil; 1H NMR (270 MHz, CDCl3) 
7.37 (d, J = 8.2 Hz, 4H, Ar-H), 7.11 (d, J = 8.2 Hz, 4H, Ar-H), 4.42 (d, J = 7.0 Hz, 1H,
CH3), 2.33 (s, 6H, CH3), 1.55 (d, J = 7.0 Hz, 3H, CH3); 13C{1H} NMR (67.8 MHz, CDCl3)
 137.9, 133.5, 130.3, 129.6, 52.8, 22.6, 21.1; IR (neat) 2920, 1491, 1442, 1178 cm-1;
Anal. Calcd for C16H18S2: C, 70.02; H, 6.61. Found: C, 70.20; H, 6.66.
Gram-scale reaction (Scheme 8)
To a mixture of styrene (1.04 mg, 10 mmol), 4-Toluenethiol (1.37 mg, 11 mmol) or n-Butyl thiol
(992.1 mg, 11 mmol), and 4-Toluenesulfonic acid monohydrate (951.1 mg, 5 mmol) in CH2Cl2
(10 mL), ZnI2 (319.1 mg, 1.1 mmol) was added, and the mixture was stirred at room temperature
for 18 h in air. After the residue was dissolved in Et2O, the solution was washed with H2O and
saturated sodium chloride and dried over anhydrous magnesium sulfate. Chromatography on silica
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