Copper-catalyzed selective syntheses of Markovnikov-type hydrothiolation products and thioacetals by the reactions of thiols with alkenes bearing heteroatoms

Article abstract of DOI:10.1016/j.tet.2016.05.050

Catalyst-controlled divergent reactions of thiophenols with alkenes bearing heteroatoms have been developed. Markovnikov-type hydrothiolation products and thioacetals were synthesized selectively by switching copper catalysts.

Full text of DOI:10.1016/j.tet.2016.05.050

Tetrahedron 72 (2016) 4111e4116
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Copper-catalyzed selective syntheses of Markovnikov-type
hydrothiolation products and thioacetals by the reactions of thiols
with alkenes bearing heteroatoms
*
Hui Xi, Enlu Ma, Zhiping Li
Department of Chemistry, Renmin University of China, Beijing 100872, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 April 2016
Received in revised form 16 May 2016
Accepted 18 May 2016
Available online 20 May 2016
Catalyst-controlled divergent reactions of thiophenols with alkenes bearing heteroatoms have been
developed. Markovnikov-type hydrothiolation products and thioacetals were synthesized selectively by
switching copper catalysts.
Ó 2016 Elsevier Ltd. All rights reserved.
Keywords:
Copper catalysis
Hydrothialation
Markovnikov addition
Controlling selectivity
Thioacetal
1. Introduction
The construction of CeS bonds is one of significant goals in
synthetic chemistry because of the numerous sulfur-containing
natural products and pharmaceuticals as well as the increasing
synthetic importance of sulfur-containing compounds.1,2 Addition
reactions of organosulfur compounds to alkenes present a general
atom-economical method for CeS bond formation, and a great ef-
forts have been made to tackle this challenge over the past de-
cades.3 anti-Markovnikov addition of thiols to alkenes has been
well established since 1905 (thiol-ene reaction).4 It usually un-
dergoes a radical-type mechanism promoted by initiators, such as
peroxides, AIBN or photochemistry (Scheme 1a, left).5 In contrast,
Markovnikov-type hydrothiolation of alkenes is far less developed
(Scheme 1a, right), mainly because it lacks the driving force to
achieve catalytic ionic process. The successful examples generally
Scheme 1. Addition reaction of organosulfur compounds to alkenes.
Controlling selectivity is one of great importance to chemistry,
especially in transition-metal-catalyzed reactions.9 Furthermore,
exploring of selective methods to access divergent products from
simple starting materials has attracted much more attentions from
a synthetic point of view. Both the Markovnikov-type hydro-
thiolation products and thioacetals are present in natural prod-
ucts10 and play important roles in organic synthesis.11 Herein, we
report an efficient and practical copper-catalyzed Markovnikov-
type hydrothiolation of alkenes bearing heteroatoms, in which both
Markovnikov-type hydrothiolation products and thioacetals can be
selectively achieved by simply switching copper catalysts
(Scheme 1c).
happened along with harsh reaction conditions.6 Recently, some
8
progress has been made by Ogawa group7 and Dunach group. In
~
2014, Ogawa and co-workers successfully realized catalytic
Markovnikov-type hydrothiolation of alkenes with thiols assisted
by the coordination of heteroatom and double bond to palladium
(Scheme 1b).7a
* Corresponding author. Tel.: þ86 10 6251 4226; fax: þ86 10 6251 6444; e-mail
address: zhipingli@ruc.edu.cn (Z. Li).
http://dx.doi.org/10.1016/j.tet.2016.05.050
0040-4020/Ó 2016 Elsevier Ltd. All rights reserved.

4112
H. Xi et al. / Tetrahedron 72 (2016) 4111e4116
2. Results and discussion
Subsequently, we investigated the generality of the methods for
selective syntheses of 3 and 4 using Cu(OAc)2 and CuBr2 as catalyst,
respectively (Tables 2e4). First, the scope and limitation of alkenes
in the hydrothiolation reactions were investigated in the presence
of Cu(OAc)2 (Table 2). Both linear and cyclic vinyl ethers 1aei
reacted with 2a to give the corresponding hydrothiolation products
3aei selectively with good to excellent yields (entries 1e9). The
reactions of the chloro-substituted and eudipleural polysubstitued
substrates, 1e and 1f, proceeded efficiently (entries 5 and 6), which
indicating a potential application in organic synthesis. In addition,
In 2013, we reported a Mn-catalyzed oxidative cyclization
between thiophenols and alkynes for synthesis of benzothio-
phene derivatives using O2 as oxidant.12 To continue our efforts
on CeS bond formation, we further investigated the reactions of
thiophenols and alkenes. When the reactions of 1-(vinyloxy)bu-
tane 1a and 4-methylbenzenethiol 2a were carried out, the
hydrothiolation product 3a and the thioacetal 4a were obtained
(Table 1). Trace amount of 3a and 4a were observed in the
presence of Mn(OAc)2 (entry 1), while a full conversion of 1a was
achieved when the catalyst was switched to FeCl2 (entry 2). 3a
and 4a were obtained in 31% and 62% yields, respectively. Al-
though 3a was formed in only 34% yield using Fe(OAc)2 as cat-
alyst, the selectivity of the reaction is excellent (entry 3). To our
delight, Cu(OAc)2 turned out to be effective and selective catalyst
for the formation of 3a (entry 4). Co(OAc)2$4H2O showed lower
efficiency compared with Cu(OAc)2 (entry 5). Interestingly, 4a
turned out to be the major product when copper halides were
applied as catalyst (entries 6e8) and an excellent yield of 4a was
achieved in 99% yield in the presence of CuBr2 (entry 8). CuSO4
also gave an excellent yield of 4a (entry 9), while 4a was ob-
tained in only 43% when catalyzed by Cu(OTf)2 (entry 10). It
should be noted that strong Br4nsted acids were also effective
for the formation of 4a (entries 11 and 12). Trace amount of 3a
and 4a were detected in other solvents, such as MeCN, PhMe and
THF (entries 13e15), indicating that DCE is a suitable solvent for
synthesis of 3a. The reaction could also be carried out under
nitrogen atmosphere (entries 16 and 17), however, a prolonged
reaction time was needed to accomplish the desired reaction
(entry 17). Importantly, 3a was obtained in good yields under air
(entries 18 and 19). These results suggested that oxygen could
greatly accelerate the reaction rate.
Table 2
Scope of the substrate 1a
Table 1
Optimization of reaction Conditionsa
Entry
cat.
Solvent
3a (%)b
4a (%)b
1
2
3
4
5
6
7
8
Mn(OAc)2
FeCl2
Fe(OAc)2
Cu(OAc)2
Co(OAc)2$4H2O
CuCl
CuCl2
CuBr2
CuSO4
Cu(OTf)2
TsOH
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
MeCN
PhMe
THF
DCE
DCE
DCE
DCE
Trace
31
34
91
55
Trace
62
Trace
Trace
Trace
60
90
99
95
43
40
10
Trace
Trace
Trace
Trace
Trace
6
Trace
Trace
34
9
10
11
12
13
14
15
16c
17d
18e
19f
96
94
TfOH
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Trace
Trace
Trace
Trace
Trace
Trace
Trace
90
80
91
aReaction conditions: 1 (0.5 mmol), 2a (2.0 mmol), Cu(OAc)2 (0.025 mmol),
DCE (5.0 mL), oxygen atmosphere, 50 oC, 3 h.
bReported yields were based on 1 and determined by 1H NMR using an
internal standard; the isolated yields were given in parentheses.
cThe reaction time is 5 h.
a
Reaction conditions: 1a (0.5 mmol), 2a (2.0 mmol), cat. (0.025 mmol), DCE
(5.0 mL), oxygen atmosphere, 50 ꢀC, 3 h; unless otherwise noted.
b
NMR yields were determined by 1H NMR using an internal standard.
Nitrogen atmosphere, 3 h.
Nitrogen atmosphere, 8 h.
Under air, 3 h.
c
d
dThe reaction time is 7 h.
e
eNot Detected.
f
Under air, 5 h.

H. Xi et al. / Tetrahedron 72 (2016) 4111e4116
4113
Table 3
smoothly with 1a to provide the desired products 3mer under
the standard reaction conditions. It is worth noting that many
synthetically relevant functional groups such as chloro and
bromo were compatible with the conditions, revealing the pos-
sibility of further transformations by the well-established cross-
coupling reactions.
Scope of the substrate 2a
Furthermore, synthesis of thioacetals 4 was studied by the
reactions of vinyl ethers 1 reacted with thiols 2 in the presence
of CuBr2 (Table 4). To our satisfaction, various thioacetals 4
were obtained in excellent yields under the standard reaction
conditions. Importantly, the reaction of 1a with phenyl-
methanethiol gave the corresponding thioacetals 4e in 95%
yield. When the hydrothiolation product 3a was used to re-
place vinyl ether 1a, the thioacetal 4a was obtained in 99%
yield in the presence of CuBr2 (Eq. 1). The result indicated that
the thioacetals 4 are generated by the reactions of the hydro-
thiolation products 3 with thiols 2. Unfortunately, the attempts
for selective synthesis of mixed thioacetals from 3 were not
successful. For example, the reaction of 3a and 2c led to the
desired mixed thioacetal 4ab in 50% yield, accompanying with
the formation of 4a and 4b (Eq. 2).
aReaction conditions: 1a (0.5 mmol), 2 (2.0 mmol), Cu(OAc)2 (0.025
mmol), DCE (5.0 mL), oxygen atmosphere, 50 oC, 3 h.
bReported yields were based on 1a and determined by 1H NMR using
an internal standard; the isolated yields were given in parentheses.
alkenes bearing nitrogen functional groups, 1j and 1k, also reacted
smoothly with 2a, affording the corresponding products in 95% and
92% yields, respectively (entries 10 and 11). However, the desired
hydrothiolation product 3l was not detected (entry 12), probably
due to the lower electron density of 1l.
Next, the scope of aryl thiols 2 in the hydrothiolation re-
actions was investigated in the presence of Cu(OAc)2 (Table 3). A
variety of thiophenols bearing both electron-donating and
electron-withdrawing substituents on the aromatic ring reacted
To demonstrate the protocol is practical and useful in organic
synthesis, Gram-scale synthesis was investigated (Eq. 3). A 5 mmol-
scale of 1a reacted with 2a in the presence of Cu(OAc)2 providing 3a
in 1.03 g (92% isolated yield).
Table 4
Scope of synthesis of thioacetals 4a,b
A plausible mechanism for the formation of 3 and 4 is described
in Scheme 2.13 A copper thiolate intermediate A is generated in situ,
and oxygen might accelerate this transportation process. Pro-
tonation of alkene 1 leads to an oxonium ion intermediate C.14
Followed by thiolation of C with B gives Markovnikov-type
hydrothiolation product 3. When CuBr2 is applied as catalyst,
a thionium ion intermediate D will be subsequently generated due
to the HBr generation from the reaction with thiol.15 The reaction of
D with thiol 2 generates thioacetal 4 by releasing an alcohol.
However, in the case of Cu(OAc)2 as catalyst, the reaction with thiol
generates more weaker acetic acid, which cannot accelerate the
hydrothiolation.
3. Conclusions
aReaction conditions: 1a (0.5 mmol), 2 (2 mmol), DCE (5.0 mL),
oxygen atmosphere, 50 oC, 3 h.
In conclusion, we have developed selective and efficient
methods for synthesis of Markovnikov-type hydrothiolation prod-
ucts and thioacetals from the same starting materials, thiophenols
1
bReported yields were based on 1 and determined by H NMR using
an internal standard; the isolated yields were given in parentheses.

4114
H. Xi et al. / Tetrahedron 72 (2016) 4111e4116
4.2.1. (1-Butoxyethyl)(p-tolyl)sulfane (3a).7a Isolated by flash col-
umn chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.4) in 86% yield (96.3 mg). Colorless oil; IR (KBr): nmax 2993,
2362, 1770, 1759, 1216, 1105, 1056, 912, 808, 744 cmꢁ1 1H NMR
;
(400 MHz, CDCl3)
d
7.36 (d, J¼8.0 Hz, 2H), 7.11 (d, J¼8.0 Hz, 2H), 4.82
(q, J¼6.4 Hz, 1H), 3.94e3.85 (m, 1H), 3.47e3.38 (m, 1H), 2.34 (s, 3H),
1.63e1.53 (m, 2H), 1.48 (d, J¼6.4 Hz, 3H), 1.44e1.34 (m, 2H), 0.93 (t,
J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d 137.5, 134.2, 129.4, 129.1,
84.7, 67.8, 31.5, 22.5, 21.1, 19.4, 13.9.
4.2.2. (1-Ethoxyethyl)(p-tolyl)sulfane (3b). Isolated by flash column
chromatography (ethyl acetate/petroleumether¼1:20, Rf¼0.5)in76%
yield (74.5 mg). Colorless oil; IR (KBr): nmax 3412, 2976, 1770, 1757,
1637,1616,1492,1442,1398,1371,1245,1149,1105, 808 cmꢁ1; 1H NMR
(400MHz,CDCl3)
d
7.36 (d, J¼8.0Hz, 2H), 7.11(d, J¼8.0Hz,2H),4.82(q,
J¼6.4 Hz,1H), 4.03e3.89 (m,1H), 3.54e3.41 (m,1H), 2.33 (s, 3H),1.48
(d, J¼6.4 Hz, 3H), 1.22 (t, J¼6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3)
Scheme 2. Proposed mechanism.
d
137.7, 134.3, 129.5, 129.0, 84.6, 63.4, 22.7, 21.1, 14.9; HRMS calcd for
C
11H16NaOS (MþNa)þ: 219.0814; found: 219.0805.
4.2.3. (1-Isobutoxyethyl)(p-tolyl)sulfane (3c). Isolated by flash col-
umn chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.7) in 68% yield (76.2 mg). Colorless oil; IR (KBr): nmax 2956,
2927, 1768, 1757, 1490, 1375, 1245, 1103, 1089, 1055, 912, 808,
and alkenes, by simply switching copper catalysts. The developed
protocols are general and practical. Efforts to understand the re-
action mechanism and apply this catalytic system to other sub-
strates are under way.
742 cmꢁ1
;
1H NMR (400 MHz, CDCl3)
d
7.36 (d, J¼8.0 Hz, 2H), 7.10
(d, J¼8.0 Hz, 2H), 4.82 (q, J¼6.4 Hz, 1H), 3.65 (dd, J¼9.2, 6.8 Hz, 1H),
3.20 (dd, J¼9.2, 6.8 Hz, 1H), 2.32 (s, 3H), 1.94e1.77 (m, 1H), 1.47 (d,
J¼6.4 Hz, 3H), 0.95e0.89 (m, 6H); 13C NMR (100 MHz, CDCl3)
4. Experimental section
d
137.5, 134.1, 129.4, 129.1, 84.9, 74.8, 28.3, 22.5, 21.1, 19.5; HRMS
calcd for C13H20NaOS (MþNa)þ: 247.1127; found: 247.1112.
4.1. General information
4.2.4. (1-(Cyclohexyloxy)ethyl)(p-tolyl)sulfane (3d). Isolated by flash
column chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.5) in 90% yield (112.5 mg). Colorless oil; IR (KBr): nmax 2929,
1H NMR spectra were recorded on 400 or 600 MHz spectrom-
eter and the chemical shifts were reported in parts per million (d)
relative to internal standard TMS (0 ppm) for CDCl3. The peak
patterns are indicated as follows: s, singlet; d, doublet; dd, doublet
of doublet; t, triplet; m, multiplet; q, quartet. The coupling con-
stants, J, are reported in Hertz (Hz). 13C NMR spectra were obtained
at 100 or 150 MHz and referenced to the internal solvent signals
(central peak is 77.0 ppm in CDCl3). CDCl3 were used as the NMR
solvent. HRMS measurements were recorded on a FTMS analyzer
using an ESI source in the positive mode. Flash column chroma-
tography was performed over silica gel 200e300. All reagents were
weighed and handled in air at room temperature. All reagents were
purchased from a commercial source and used without further
purification. 1,2-Dichloroethane (DCE) was freshly distilled with
calcium hydride before use.
2854, 1772, 1490, 1448, 1367, 1245, 1099, 1087, 1055, 972, 808 cmꢁ1
;
1H NMR (400 MHz, CDCl3)
d
7.38 (d, J¼8.0 Hz, 2H), 7.10 (d, J¼8.0 Hz,
2H), 4.95 (q, J¼6.4 Hz,1H), 3.84e3.71 (m, 1H), 2.33 (s, 3H), 1.95e1.82
(m, 2H), 1.79e1.67 (m, 2H), 1.58e1.50 (m, 1H), 1.45 (d, J¼6.4 Hz, 3H),
1.41e1.15 (m, 5H); 13C NMR (100 MHz, CDCl3)
d 137.6, 134.5, 129.4,
128.9, 81.6, 74.7, 33.1, 31.1, 25.7, 24.3, 24.0, 23.2, 21.1; HRMS calcd for
C
15H22NaOS (MþNa)þ: 273.1284; found: 273.1273.
4.2.5. (1-(2-Chloroethoxy)ethyl)(p-tolyl)sulfane (3e). Isolated by
flash column chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.6) in 57% yield (66.0 mg). Colorless oil; IR (KBr): nmax 2980,
1768, 1757, 1490, 1445, 1373, 1242, 1107, 1051, 912, 810, 744 cmꢁ1; 1H
NMR (400 MHz, CDCl3)
d
7.38 (d, J¼8.0 Hz, 2H), 7.12 (d, J¼8.0 Hz, 2H),
4.90 (q, J¼6.4 Hz, 1H), 4.17e4.08 (m, 1H), 3.76e3.68 (m, 1H),
4.2. General procedure for synthesis of hydrothiolation
product 3
3.67e3.62 (m, 2H), 2.34 (s, 3H), 1.50 (d, J¼6.4 Hz, 3H); 13C NMR
(100 MHz, CDCl3)
d 137.9, 134.2, 129.5, 128.4, 84.9, 67.7, 42.7, 22.2,
21.1; HRMS calcd for C11H15ClNaOS (MþNa)þ: 253.0424; found:
A dried Schlenk tube was evacuated and then filled with ox-
ygen through an oxygen balloon, then Cu(OAc)2 (4.5 mg,
0.025 mmol) was added under oxygen atmosphere. The Schlenk
tube was sealed with a rubber plug, evacuated, and filled with
oxygen through an oxygen balloon. Alkene 1 (0.5 mmol), thio-
phenol 2 (2.0 mmol) and DCE (5.0 mL) were added sequentially.
The reaction mixture was vigorously stirred at 50 ꢀC for 3 h. After
cooling down to room temperature, the resulting reaction solu-
tion was filtered through a pad of silica with ethyl acetate as
eluent. The solvent was evaporated in vacuo to give the crude
product 3. NMR yield was determined by 1H NMR using dibro-
momethane as an internal standard. Solvent was evaporated and
the residue was purified by flash column chromatography on
silica gel (eluent: ethyl acetate/petroleum ether) to afford the
product 3.
253.0414.
4.2.6. (((Oxybis(ethane-2,1-diyl))bis(oxy))bis(ethane-1,1-diyl))bis(p-
tolylsulfane) (3f). Isolated by flash column chromatography (ethyl
acetate/petroleum ether¼1:10, Rf¼0.3) in 66% yield (133.9 mg).
Colorless oil; IR (KBr): nmax 2976, 2926, 2866, 1768, 1757, 1492, 1371,
1245, 1103, 1087, 912, 810, 742 cmꢁ1 1H NMR (400 MHz, CDCl3)
;
d
7.38 (d, J¼8.0 Hz, 4H), 7.10 (d, J¼8.0 Hz, 4H), 4.94e4.84 (m, 2H),
4.11e3.98 (m, 2H), 3.73e3.59 (m, 6H), 2.32 (s, 6H), 1.48 (d, J¼6.4 Hz,
6H); 13C NMR (100 MHz, CDCl3)
d 137.6, 134.1, 129.4, 128.8, 84.9,
70.2, 70.1, 66.9, 22.4, 21.0; HRMS calcd for C22H30NaO3S2 (MþNa)þ:
429.1529; found: 429.1518.
4.2.7. (1-Ethoxypropyl)(p-tolyl)sulfane (3g). Isolated by flash col-
umn chromatography (ethyl acetate/petroleum ether¼1:20,

H. Xi et al. / Tetrahedron 72 (2016) 4111e4116
4115
Rf¼0.6) in 80% yield (84.0 mg). Colorless oil; IR (KBr): nmax 2980,
2935, 1768, 1759, 1490, 1375, 1246, 1058, 912, 744 cmꢁ1 1H NMR
(400 MHz, CDCl3)
7.36 (d, J¼8.0 Hz, 2H), 7.10 (d, J¼8.0 Hz, 2H), 4.53
1.43e1.33 (m, 2H), 0.93 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3)
;
d 159.7, 136.5, 122.8, 114.2, 84.9, 68.0, 55.3, 31.5, 22.5, 19.4, 13.9.
d
(t, J¼6.4 Hz, 1H), 4.05e3.92 (m, 1H), 3.53e3.40 (m, 1H), 2.32 (s, 3H),
4.2.14. (4-Bromophenyl)(1-butoxyethyl)sulfane (3o). Isolated by
flash column chromatography (ethyl acetate/petroleum
1.84e1.64 (m, 2H), 1.22 (t, J¼7.2 Hz, 3H), 0.99 (t, J¼7.2 Hz, 3H); 13
C
NMR (100 MHz, CDCl3)
d
137.5, 134.1, 129.4, 129.3, 90.9, 63.5, 29.1,
ether¼1:20, Rf¼0.7) in 86% yield (123.8 mg). Colorless oil; IR (KBr):
21.1, 14.8, 10.8; HRMS calcd for C12H18NaOS (MþNa)þ: 233.0971;
nmax 2956, 2931, 2870, 1768, 1471, 1384, 1371, 1246, 1109, 1085, 1010,
found: 233.0959.
912, 815, 742 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d 7.46e7.39 (m, 2H),
7.36e7.30 (m, 2H), 4.87 (q, J¼6.4 Hz, 1H), 3.91e3.80 (m, 1H),
3.48e3.37 (m, 1H), 1.65e1.53 (m, 2H), 1.48 (d, J¼6.4 Hz, 3H),
1.44e1.32 (m, 2H), 0.92 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3)
4.2.8. 2-(p-Tolylthio)tetrahydro-2H-pyran (3h).16 Isolated by flash
column chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.5) in 70% yield (72.8 mg). Colorless oil; IR (KBr): nmax 2937,
2862, 1770, 1757, 1492, 1438, 1242, 1186, 1103, 1076, 1035, 1004, 914,
d
135.1, 132.2, 131.7, 121.7, 84.5, 67.7, 31.4, 22.4, 19.4, 13.9; HRMS
calcd for C12H17BrNaOS (MþNa)þ: 311.0076; found: 311.0080.
808, 721 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
7.38 (d, J¼8.0 Hz, 2H),
7.10 (d, J¼8.0 Hz, 2H), 5.20e5.06 (m, 1H), 4.23e4.10 (m, 1H),
4.2.15. (1-Butoxyethyl)(2,4-dimethylphenyl)sulfane (3p). Isolated by
3.63e3.50 (m, 1H), 2.32 (s, 3H), 2.07e1.94 (m, 1H), 1.91e1.75 (m,
flash
column
chromatography
(ethyl
acetate/petroleum
2H), 1.68e1.54 (m, 3H); 13C NMR (100 MHz, CDCl3)
d
136.9, 131.6,
ether¼1:20, Rf¼0.7) in 72% yield (85.7 mg). Colorless oil; IR (KBr):
131.4, 129.5, 85.6, 64.6, 31.5, 25.5, 21.7, 21.0.
nmax 2955, 1768, 1757, 1475, 1373, 1242, 1097, 1055, 912, 812,
742 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
7.38 (d, J¼8.0 Hz,1H), 7.03 (s,
4.2.9. 2-(p-Tolylthio)tetrahydrofuran (3i).17 Isolated by flash col-
umn chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.5) in 77% yield (74.7 mg). Colorless oil; IR (KBr): nmax 2976,
1H), 7.95 (d, J¼8.0 Hz, 1H), 4.84 (q, J¼6.4 Hz, 1H), 3.90e3.80 (m, 1H),
3.46e3.35 (m, 1H), 2.41 (s, 3H), 2.29 (s, 3H), 1.61e1.51 (m, 2H), 1.47
(d, J¼6.4 Hz, 3H), 1.41e1.33 (m, 2H), 0.91 (t, J¼7.2 Hz, 3H); 13C NMR
2949, 2868, 1768, 1757, 1492, 1375, 1242, 1049, 912, 808, 742 cmꢁ1
;
(100 MHz, CDCl3) d 140.8, 137.6, 134.7, 131.0, 129.0, 127.0, 84.9, 67.8,
1H NMR (400 MHz, CDCl3)
d
7.40 (d, J¼8.0 Hz, 2H), 7.10 (d, J¼8.0 Hz,
31.5, 22.5, 21.1, 21.0, 19.4, 13.9; HRMS calcd for C14H22NaOS
2H), 5.61e5.53 (m, 1H), 4.06e3.97 (m, 1H), 3.97e3.89 (m, 1H),
(MþNa)þ: 261.1284; found: 261.1301.
2.38e2.29 (m, 1H), 2.31(S, 3H), 2.06e1.80 (m, 3H); 13C NMR
(100 MHz, CDCl3)
d
136.9, 131.7, 129.5, 87.4, 67.1, 32.5, 24.7, 21.0.
4.2.16. (1-Butoxyethyl)(2-chlorophenyl)sulfane (3q). Isolated by
flash
ether¼1:20, Rf¼0.6) in 68% yield (83.0 mg). Colorless oil; IR (KBr):
nmax 2958, 2929, 1452, 1373, 1247, 1105, 1035, 750, 661 cmꢁ1 1H
NMR (400 MHz, CDCl3) 7.66e7.59 (m, 1H), 7.44e7.36 (m, 1H),
column
chromatography
(ethyl
acetate/petroleum
4.2.10. 1-(1-(p-Tolylthio)ethyl)pyrrolidin-2-one (3j).7a Isolated by
flash column chromatography (ethyl acetate/petroleum ether¼1:1,
Rf¼0.2) in 87% yield (102.2 mg). Colorless oil; IR (KBr): nmax 2976,
1768, 1691, 1597, 1490, 1458, 1411, 1375, 1282, 1199, 1058, 808,
;
d
7.23e7.15 (m, 2H), 5.07 (q, J¼6.4 Hz, 1H), 3.86e3.77 (m, 1H),
3.50e3.42 (m, 1H), 1.58 (d, J¼6.4 Hz, 3H), 1.57e1.51 (m, 2H),
1.41e1.30 (m, 2H), 0.90 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3)
742 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
7.30 (d, J¼8.0 Hz, 2H), 7.08 (d,
J¼8.0 Hz, 2H), 5.83 (q, J¼6.8 Hz, 1H), 3.64e3.54 (m, 1H), 3.37e3.26
(m,1H), 2.30 (s, 3H), 2.29e2.21 (m,1H), 2.15e2.04 (m,1H),1.99e1.74
d
136.4, 134.0, 133.3, 129.7, 128.1, 126.9, 84.3, 67.2, 31.5, 22.1, 19.3,
(m, 2H), 1.47 (d, J¼6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d
174.4,
13.8; HRMS calcd for C12H17ClNaOS (MþNa)þ: 267.0581; found:
137.7, 132.8, 129.5, 129.1, 54.8, 41.2, 31.1, 21.1, 18.8, 17.6.
267.0573.
4.2.11. 1-(1-(p-Tolylthio)ethyl)azepan-2-one (3k). Isolated by flash
column chromatography (ethyl acetate/petroleum ether¼1:5,
Rf¼0.3) in 84% yield (110.5 mg). White solid; IR (KBr): nmax 2964,
2927, 2856, 1643, 1492, 1438, 1411, 1259, 1182, 1145, 1091, 1062, 975,
4.2.17. (1-Butoxyethyl)(naphthalen-1-yl)sulfane (3r). Isolated by
flash
column
chromatography
(ethyl
acetate/petroleum
ether¼1:20, Rf¼0.5) in 85% yield (109.2 mg). Colorless oil; IR (KBr):
nmax 2956, 2931, 1768, 1759, 1373, 1242, 1097, 1055, 912, 796, 771,
806, 729 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
7.25 (d, J¼8.0 Hz, 2H),
744 cmꢁ1
;
1H NMR (400 MHz, CDCl3)
d
8.53 (d, J¼8.4 Hz, 1H),
7.07 (d, J¼8.0 Hz, 2H), 6.45 (q, J¼6.8 Hz, 1H), 3.52e3.43 (m, 1H),
3.34e3.24 (m, 1H), 2.42e2.32 (m, 2H), 2.29 (s, 3H), 1.69e1.46 (m,
7.87e7.74 (m, 3H), 7.59e7.47 (m, 2H), 7.45e7.38 (m, 1H), 4.98 (q,
J¼6.4 Hz, 1H), 3.95e3.86 (m, 1H), 3.49e3.39 (m, 1H), 1.60e1.51 (m,
2H), 1.48 (d, J¼6.4 Hz, 3H), 1.41e1.31 (m, 2H), 0.90 (t, J¼7.2 Hz, 3H);
6H), 1.41 (d, J¼6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d 175.6, 136.7,
130.9, 130.1, 129.5, 56.3, 42.6, 37.3, 29.8, 29.0, 23.2, 21.0, 19.1; HRMS
13C NMR (150 MHz, CDCl3)
d 135.0, 134.0, 133.4, 131.0, 128.6, 128.4,
calcd for C15H21NNaOS (MþNa)þ: 286.1236; found: 286.1227.
126.4, 126.1, 126.0, 125.5, 85.6, 68.1, 31.5, 22.7, 19.4, 13.8; HRMS
calcd for C16H21OS (MþH)þ: 261.1308; found: 261.1302.
4.2.12. (1-Butoxyethyl)(phenyl)sulfane (3m).7a Isolated by flash
column chromatography (ethyl acetate/petroleum ether¼1:10,
Rf¼0.6) in 68% yield (71.4 mg). Colorless oil; IR (KBr): nmax 2958,
4.3. General procedure for synthesis of thioacetal 4
2929, 2870, 1768, 1757, 1475, 1371, 1246, 1109, 912, 746 cmꢁ1
;
1H
A dried Schlenk tube was evacuated and then filled with oxygen
through an oxygen balloon, then CuBr2 (5.6 mg, 0.025 mmol) was
added under oxygen atmosphere. The Schlenk tube was sealed with
a rubber plug, evacuated, and filled with oxygen through an oxygen
balloon. Alkene 1 (0.5 mmol), thiophenol 2 (2.0 mmol) and DCE
(5.0 mL) were added sequentially. The reaction mixture was vig-
orously stirred at 50 ꢀC for 3 h. After cooling down to room tem-
perature, the resulting reaction solution was filtered through a pad
of silica with ethyl acetate as eluent. The solvent was evaporated in
vacuo to give the crude product 4. NMR yield was determined by 1H
NMR using dibromomethane as an internal standard. Solvent was
evaporated and the residue was purified by flash column chroma-
tography on silica gel (eluent: ethyl acetate/petroleum ether) to
afford the product 4.
NMR (400 MHz, CDCl3) d 7.51e7.44 (m, 2H), 7.33e7.23 (m, 3H), 4.89
(q, J¼6.4 Hz, 1H), 3.94e3.82 (m, 1H), 3.50e3.37 (m, 1H), 1.63e1.52
(m, 2H), 1.50 (d, J¼6.4 Hz, 3H), 1.45e1.33 (m, 2H), 0.92 (t, J¼7.2 Hz,
3H); 13C NMR (100 MHz, CDCl3)
67.7, 31.5, 22.5, 19.4, 13.9.
d 133.7, 133.1, 128.6, 127.4, 84.6,
4.2.13. (1-Butoxyethyl)(4-methoxyphenyl)sulfane (3n).7a Isolated by
flash column chromatography (ethyl acetate/petroleum
ether¼1:20, Rf¼0.2) in 84% yield (100.8 mg). Colorless oil; IR (KBr):
nmax 2958, 2931, 2870, 1591, 1492, 1244, 1103, 1089, 1033, 827,
744 cmꢁ1
; d 7.43e7.37 (m, 2H),
1H NMR (400 MHz, CDCl3)
6.89e6.82 (m, 2H), 4.73 (q, J¼6.4 Hz,1H), 3.96e3.87 (m,1H), 3.80 (s,
3H), 3.46e3.34 (m, 1H), 1.62e1.53 (m, 2H), 1.43 (d, J¼6.4 Hz, 3H),

4116
H. Xi et al. / Tetrahedron 72 (2016) 4111e4116
4.3.1. Ethane-1,1-diylbis(p-tolylsulfane) (4a). Isolated by flash
column chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.7) in 91% yield (124.6 mg). Colorless oil; IR (KBr): nmax
(10XNL017), and Beijing National Laboratory for Molecular Sciences
(BNLMS).
2976, 1770, 1757, 1490, 1240, 1049, 912, 808, 744 cmꢁ1 1H NMR
;
Supplementary data
(400 MHz, CDCl3)
d
7.38 (d, J¼8.0 Hz, 4H), 7.12 (d, J¼8.0 Hz,
Supplementary data(Copies of 1H and 13C NMR spectra of all
new compounds) associated with this article can be found in the
online version, at http://dx.doi.org/10.1016/j.tet.2016.05.050.
4H), 4.42 (q, J¼6.8 Hz, 1H), 2.34 (s, 6H), 1.55 (d, J¼6.8 Hz, 3H);
13C NMR (100 MHz, CDCl3)
d 137.9, 133.5, 130.3, 129.6, 52.8,
22.6, 21.2; HRMS calcd for C16H18NaS2 (MþNa)þ: 297.0742;
found: 297.0743.
References and notes
4.3.2. Ethane-1,1-diylbis((4-methoxyphenyl)sulfane) (4b). Isolated
by flash column chromatography (ethyl acetate/petroleum
ether¼1:20, Rf¼0.3) in 95% yield (145.4 mg). Colorless oil; IR (KBr):
ꢀ
ꢁ
1. (a) Denes, F.; Pichowicz, M.; Povie, G.; Renaud, P. Chem. Rev. 2014, 114, 2587; (b)
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Yin, C.; Huo, F.; Zhang, J.; Martínez-Manez, R.; Yang, Y.; Lv, H.; Li, S. Chem. Soc.
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1596; (d) Corma, A.; Leyva-Perez, A.; Sabater, M. J. Chem. Rev. 2011, 111, 1657; (e)
nmax 2960, 1770, 1589, 1490, 1284, 1244, 1170, 1029, 912, 742 cmꢁ1
;
ꢀ
1H NMR (400 MHz, CDCl3)
d
7.43 (d, J¼8.8 Hz, 4H), 6.85 (d, J¼8.8 Hz,
Hoyle, C. E.; Bowman, C. N. Angew. Chem., Int. Ed. 2010, 49, 1540; (f) Dondoni, A.
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4H), 4.24 (q, J¼6.8 Hz, 1H), 3.80 (s, 6H), 1.50 (d, J¼6.8 Hz, 3H); 13C
NMR (100 MHz, CDCl3)
d 159.8, 136.1, 124.2, 114.3, 55.3, 54.3, 22.5;
ꢀ
2. (a) Arrayas, R. G.; Carretero, J. C. Chem. Commun. 2011, 2207; (b) McGarrigle, E. M.;
HRMS calcd for
329.0645.
C
16H18NaO2S2 (MþNa)þ: 329.0640; found:
Myers, E. L.; Illa, O.; Shaw, M. A.; Riches, S. L.; Aggarwal, V. K. Chem. Rev. 2007, 107,
5841; (c) Pachamuthu, K.; Schmidt, R. R. Chem. Rev. 2006, 106, 160; (d) Jeppesen, J.
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4.3.3. Ethane-1,1-diylbis((4-bromophenyl)sulfane) (4c). Isolated by
flash column chromatography (ethyl acetate/petroleum
ether¼1:20, Rf¼0.7) in 90% yield (180.5 mg). Colorless oil; IR (KBr):
nmax 2968, 2920, 1770, 1757, 1558, 1472, 1384, 1246, 1008, 912, 814,
743 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
7.43 (d, J¼8.4 Hz, 4H), 7.30
(d, J¼8.4 Hz, 4H), 4.47 (q, J¼6.8 Hz, 1H), 1.58 (d, J¼6.8 Hz, 3H); 13C
NMR (100 MHz, CDCl3) d 134.5, 132.7, 132.0, 122.3, 52.3, 22.5; HRMS
5. (a) Fadeyi, O. O.; Mousseau, J. J.; Feng, Y.; Allais, C.; Nuhant, P.; Chen, M. Z.;
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Seo, S.; Abu Bakar, N. S. B.; Greaney, M. F. Chem. Commun. 2015, 4383; (c) Tyson,
E. L.; Niemeyer, Z. L.; Yoon, T. P. J. Org. Chem. 2014, 79, 1427; (d) Tyson, E. L.;
Ament, M. S.; Yoon, T. P. J. Org. Chem. 2013, 78, 2046; (e) Lou, F.-W.; Xu, J.-M.;
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calcd for C14H12Br2NaS2 (MþNa)þ: 424.8639; found: 424.8652.
4.3.4. Ethane-1,1-diylbis((2,4-dimethylphenyl)sulfane) (4d). Isolated
by flash column chromatography (ethyl acetate/petroleum
ether¼1:20, Rf¼0.8) in 94% yield (141.9 mg). Colorless oil; IR (KBr):
nmax 2972, 2920,1770,1757, 1474, 1246,1047, 912, 813, 742 cmꢁ1; 1H
ꢀ
Leyva-Perez, A.; Corma, A. Adv. Synth. Catal. 2012, 354, 678; (c) Menggenbateer;
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J.-i.; Sonoda, N.; Hirao, T. J. Org. Chem. 1996, 61, 4161.
NMR (400 MHz, CDCl3)
d
7.38 (d, J¼8.0 Hz, 2H), 7.01 (s, 2H), 6.95 (d,
J¼8.0 Hz, 2H), 4.33 (q, J¼6.8 Hz, 1H), 2.34 (s, 6H), 2.28 (s, 6H), 1.57
(d, J¼6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d 140.5, 137.9, 133.9,
131.2, 130.2, 127.1, 52.2, 22.7, 21.0, 20.7; HRMS calcd for C18H22NaS2
(MþNa)þ: 325.1055; found: 325.1060.
ꢀ
~
8. (a) Weïwer, M.; Chaminade, X.; Bayon, J. C.; Dunach, E. Eur. J. Org. Chem. 2007,
~
2464; (b) Weïwer, M.; Coulombel, L.; Dunach, E. Chem. Commun. 2006, 332; (c)
4.3.5. Ethane-1,1-diylbis(benzylsulfane) (4e).18 Isolated by flash
column chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.2) in 86% yield (117.3 mg). Colorless oil; IR (KBr): nmax 2964,
~
Weïwer, M.; Dunach, E. Tetrahedron Lett. 2006, 47, 287.
9. For review see: (a) Mahatthananchai, J.; Dumas, A. M.; Bode, J. W. Angew. Chem.,
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1757, 1494, 1452, 1371, 1240, 1049, 912, 741, 698 cmꢁ1 1H NMR
;
(400 MHz, CDCl3)
d
7.32e7.18 (m, 10H), 3.85 (d, J¼13.2 Hz, 2H),
3.73 (d, J¼13.2 Hz, 2H), 3.63 (q, J¼6.8 Hz, 1H), 1.52 (d, J¼6.8 Hz,
3H); 13C NMR (100 MHz, CDCl3)
34.9, 22.5.
d 138.1, 128.9, 128.5, 126.9, 44.5,
4.3.6. Propane-1,1-diylbis(p-tolylsulfane) (4f). Isolated by flash col-
umn chromatography (ethyl acetate/petroleum ether¼1:20,
Rf¼0.8) in 91% yield (131.0 mg). Colorless oil; IR (KBr): nmax 3477,
3414, 2966, 1770, 1759, 1616, 1490, 1450, 1240, 1049, 912, 808, 742,
623, 495 cmꢁ1 1H NMR (400 MHz, CDCl3)
; d 7.41e7.33 (m, 4H),
7.16e7.06 (m, 4H), 4.23 (t, J¼6.6 Hz, 1H), 2.34 (s, 6H), 1.88e1.78 (m,
2H), 1.11 (t, J¼7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d 137.8, 133.3,
130.6, 129.6, 60.8, 28.8, 21.1, 11.7; HRMS calcd for C17H20NaS2
ꢀ
Int. Ed. 2015, 54, 1595; (c) Fang, W.; Presset, M.; Guerinot, A.; Bour, C.; Bezzenine-
(MþNa)þ: 311.0899; found: 311.0904.
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Acknowledgements
Financial support from the National Natural Science Foundation
of China (21272267), State Key Laboratory of Heavy Oil Processing
(SKLOP201401001), the Fundamental Research Funds for the Cen-
tral Universities, the Research Funds of Renmin University of China
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