Efficient Thiolation of Alcohols Catalyzed by Long Chained Acid-Functionalized Ionic Liquids under Mild Conditions

Article abstract of DOI:10.1002/ejoc.201900169

Thioethers as important building blocks have been usually found in organic synthesis. Herein, a series of long chained acid-functionalized ionic liquids derived from pyrrolidine were applied for the thiolation of alcohols to synthesize different compounds containing thioether structures. This kind of ionic liquids exhibited higher efficiency than general ionic liquids based on imidazole, providing up to 99 % yield with [BsCtP][OTf] as the catalyst at room temperature for 0.25 h. The results indicated that the activities of the ionic liquids have relationship with the side chain length of ionic liquids based on pyrrolidine, anions and cations. The catalytic system had wide substrate scope and was applicable for the reaction of aromatic primary and secondary alcohols and thiols including aliphatic and aromatic thiols, benzothiazole-2-thiols and benzooxazole-2-thiols. Besides, there was no obvious change in activity of the catalyst after six runs. Thus, the catalytic system exhibited good recyclability. Additionally, carbocations should be the key intermediate and several functionalized groups of the ionic liquids have synergetic effect for the thiolation.

Full text of DOI:10.1002/ejoc.201900169

A Journal of
Accepted Article
Title: Efficient Thiolation of Alcohols Catalyzed by Long Chained Acid-
functionalized Ionic Liquids under Mild Conditions
Authors: Chengxia Miao, Hongfeng Zhuang, Yating Wen, Feng Han,
Qing-Feng Yang, Lei Yang, Zhen Li, and Chungu Xia
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10.1002/ejoc.201900169
European Journal of Organic Chemistry
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Efficient Thiolation of Alcohols Catalyzed by Long Chained Acid-
functionalized Ionic Liquids under Mild Conditions
Chengxia Miao,[a,b] Hongfeng Zhuang,[a] Yating Wen,[a] Feng Han,* [a,b] Qing-Feng Yang,[c] Lei Yang,[b]
Zhen Li,[b] and Chungu Xia*[b]
Abstract: Thioethers as important building blocks have been usually
found in organic synthesis. Herein, a series of long chained acid-
functionalized ionic liquids derived from pyrrolidine were applied for
the thiolation of alcohols to synthesize different compounds
containing thioether structures. This kind of ionic liquids exhibited
higher efficiency than general ionic liquids based on imidazole,
providing up to 99% yield with [BsCtP][OTf] as the catalyst at room
temperature for 0.25 h. The results indicated that the activities of the
ionic liquids have relationship with the side chain length of ionic
liquids based on pyrrolidine, anions and cations. The catalytic
system had wide substrate scope and was applicable for the
reaction of aromatic primary and secondary alcohols and thiols
including aliphatic and aromatic thiols, benzothiazole-2-thiols and
benzooxazole-2-thiols. Besides, there was no obvious change in
activity of the catalyst after six runs. Thus, the catalytic system
exhibited good recyclability. Additionally, carbocations should be the
key intermediate and several functionalized groups of the ionic
liquids have synergetic effect for the thiolation.
cross-coupling of aryl boronic acids and alkyl thiols or N-
thio(alkyl, aryl, heteroaryl)imides,[14,15,16] metal catalyzed
hydrothiolation of alkynes and so on.[17] During the development
of the system for synthesis of thioethers, significant progress
has been made.
With the development of Green Chemistry, easily available
and cheap alcohols are attractive sources of electrophiles and
Figure 1. Some important compounds containing thioethers structure.
the only byproduct formed in the reaction of alcohols and thiols
is water. Thus, direct nucleophilic substitution reactions of
alcohols have gained much attention.[18-22] Previously, we
realized direct synthesis of polysubstituted olefins via
construction of C-C bonds from alcohols or alkenes with
alcohols and also developed system for direct amination of
alcohols.[23,24] Generally, carbocations from alcohols were
proposed as the active intermediates during the systems. As for
the direct displacement of alcohols with sulfur nucleophiles,
there are also some reported systems at present. Sanz achieved
the direct nucleophilic substitution of the hydroxy group of allylic
and benzylic alcohols with a large variety of carbon- and
heteroatom-centered nucleophiles catalyzed by simple Brønsted
acids such as p-toluenesulfonic acid monohydrate or polymer-
Introduction
Sulfur-containing compounds serve important functions in
organic synthesis, such as substrates, photosensitizers or
hydrogen-atom-transfer (HAT) reagents and so on.[1] Thioethers
as important building blocks in some important drugs or some
biologically active compounds (shown in Figure 1) have led to an
increased awareness of researchers.[2-4] At present, a variety of
methods for the corresponding synthesis of thioethers are
available in the literatures.[5-8] The reaction of aryl halides and
thiols is the typical method to construct C-S bonds.[9-11]
Researchers also built other important methods for the formation
of thioethers, such as the addition of thiols to carbonyl
compounds followed by the in-situ reduction of the generated
intermediate thionium ion,[12] deoxygenation of sulfoxides,[13]
bound
p-toluenesulfonic
acid.[25]
Aluminum
dodecatungstophosphate or ZrCl2 was also beneficial for the
thiolation of alcohols, providing excellent yields.[26,27] Bandgar
employed silica supported perchloric acid as the catalyst for
synthesis of thioethers from alcohols and thiols.[28] Wu group
also successfully realized the direct displacement of alcohols
with sulfur nucleophiles catalyzed by Ga(OTf)3.[29] Based on the
systems, we found thiolation of alcohols could be carried out
well with simple Lewis or Brønsted acids as the catalysts.
However, these catalysts could not be recycled and separated
easily with the product. On the other hand, some developed
supported catalysts exhibited good recyclability but relatively
poor activity. Therefore, it is significant and innovative to develop
catalytic systems having both high activity and recyclability for
thiolation of alcohols.
Ionic Liquids (ILs) are organic salts, generally composed of an
organic cation and a wide range of different anions.[30] Ionic
liquids were often used as a class of environmentally friendly
solvents because of their extraordinary properties such as
nonvolatility, nonflammability, high stability, high ionic
conductivity, and easy recyclability.[31] Recently, task-specific
ionic liquids have received more and more attention and were
[a]
[b]
Dr. C. Miao, H. Zhuang, Y. Wen, Prof. F. Han
College of Chemistry and Material Science, Shandong Agricultural
University, Tai’an 271018, Shandong, China
E-mail: fenghan@sdau.edu.cn
https://orcid.org/0000-0003-0707-8575
Dr. C. Miao, Prof. F. Han, Dr. L. Yang, Dr. Z. Li, Prof. C. Xia
State Key Laboratory for Oxo Synthesis and Selective Oxidation,
Suzhou Research Institute of LICP, Lanzhou Institute of Chemical
Physics (LICP), Chinese Academy of Sciences, Lanzhou 730000,
Gansu, China
E-mail: cgxia@licp.cas.cn
https://www.mendeley.com/authors/55539136900/
Dr. Q.-F. Yang
[c]
State Key Laboratory of High-efficiency Utilization of Coal and Green
Chemical Engineering, Ningxia University, Yinchuan 750021,
Ningxia, China
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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10.1002/ejoc.201900169
European Journal of Organic Chemistry
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employed as the catalyst and so on.[32] Among them, acidic ionic
liquids have been widely used in alkylation, oxidation,
esterification and so on and long chained ionic liquids would
exhibit surface activity and have certain promoted effect on
reactions.[33]
that the length of the side chain would affect the yields of the
products. [BsCtP][OTf] with sixteen carbons on the side chain
provided 87% yield, however, the yield would reduce by further
Table 1. Screening of ionic liquids for thiolation of diphenylcarbinol with
benzooxazole-2-thiol.[a]
In our continuing effort on developing acidic ionic liquids
catalyzed reactions,[23,24,34-37] we synthesized a series of muti-
functionalized ionic liquids derived from pyrrolidine and applied
them for the thiolation of alcohols (Figure 2). Delightedly, the
Entry
1
2
3
4
Catalyst
[BMIM][BF4]
[BMIM][PF6]
[HMIM][OTs]
[BsMIM][HSO4]
[BsMIM][OTf]
[TG][OTf]
Yield (%)[b]
NR[c]
NR[c]
NR[c]
28
5
6
59
79
7
8
9
10
11
12
[BsMP][OTf]
[BsHP][OTf]
[BsDP][OTf]
[BsTdP][OTf]
[BsCtP][OTf]
[BsOdP][OTf]
34
68
80
83
87
81
[a] Reaction conditions: diphenylcarbinol (0.5 mmol), benzooxazole-2-thiol
(0.6 mmol) and catalyst (10 mol%, according to diphenylcarbinol) dissolved
in 2 mL of 1,2-dichloroethane were stirred at room temperature for 1 h. [b]
GC yield, biphenyl as internal standard. [c] NR = no reaction.
Figure 2.
A
series of ionic liquids used in the work. (OTf
=
trifluoromethanesulfonyl, OTs = p-toluenesulfonyl).
increasing the chain length (Table 1, entries 11 vs 12).
Subsequently, other reaction conditions such as solvents and
the loading of catalyst were also investigated (Table S1 and S2).
Then, [BsCtP][OTf] (10 mol%) as the catalyst, 1,2-
dichloroethane (DCE) as the solvent and room temperature
were the optimized reaction conditions.
With optimized reaction conditions in hand, we first
investigated the reactivities of a series of aromatic secondary
and primary alcohols with benzooxazole-2-thiol or benzenethiols
shown in Table 2. Obviously, the activities of benzohydrol
derivatives had certain relationship with the electron properties
and steric hindrance of substituent groups on the phenyl ring
(Table 2, entries 1-6). Benzohydrol derivatives with electron-
donating groups (such as OMe, Me) on one side of the phenyl
ring gave better activities (Table 2, entries 2, 3 vs 1). On the
other hand, benzohydrol derivatives with electron-withdrawing
groups (Cl) as the substrate could give 90% yield when the
ionic liquids based on pyrrolidine exhibited more efficiency than
general ionic liquids based on imidazole, providing up to 99%
yield with [BsCtP][OTf] as the catalyst at room temperature for
0.25 h (Scheme 1). The results indicated that the activities of the
ionic liquids have relationship with anions, cations and the side
chain length of ionic liquids based on pyrrolidine. Moreover, the
catalytic system exhibited good recyclability.
Scheme 1. Thiolation of alcohols at room temperature.
reaction time was
4 h (Table 2, entry 4). (3- or 2-
Chlorophenyl)(phenyl)methanol provided 89% or 84% yield
respectively after prolonging the reaction time to 20 hours (Table
2, entries 5 and 6). And there is no significant influence of the
electron properties on the activities by using diphenylcarbinol
derivatives with two substituent groups on two phenyl rings as
the substrates (Table 2, entries 7 and 8). Additionally, a series of
benzyl alcohols were also examined. The electron properties
and steric hindrance of substituent groups on the phenyl ring
also affected the activities of the benzyl alcohols (Table 2,
entries 9-11). Then the reactivities of aromatic secondary and
primary alcohols with benzenethiol were studied (Table 2,
entries 12-15). Interestingly, benzohydrol with 4-substituted
groups exhibited better reactivities than simple diphenylcarbinol,
providing more than 90% yields within 0.25 h (Table 2, entries
13, 14 vs 12). Additionally, 83% yield could be obtained by
employing 4-methoxybenzyl alcohol as the substrate (Table 2,
entry 15).
Results and Discussion
We commenced our studies with diphenylcarbinol and
benzooxazole-2-thiol as the substrates and the results were
summarized in Table 1. Initially, simple neutral ionic liquids such
as [BMIM][BF4] and [BMIM][PF6] were tested and no reaction
occurred (Table 1, entries 1-2). The reaction was also inert using
[HMIM][OTs] as the catalyst (Table 1, entry 3). Fortunately, the
reaction could work smoothly when ILs based on imidazolium
have acidic anions and the side chain introduced by acidic group
(Table 1, entries 4 and 5). Moreover, OTf- as the anion gave
better result. Guanidinium ionic liquids ([TG][OTf]) provided up to
79% yield (Table 1, entry 6). The results indicated that the
activities of the reactions have relationship with anions and
cations of the ionic liquids. Inspired by this, a series of
pyrrolidinium ionic liquids were synthesized and applied for the
reaction (Table 1, entries 7-12). And the results demonstrated
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Table 2. Thiolation of a series of aromatic alcohols with benzooxazole-2-thiol or benzenethiol catalyzed by [BsCtP][OTf].[a]
Entry
1
Alcohol
Thiol
Product
t (h)
Yield
(%)
1
87[c]
2
3
4
1
1
4
96
97
90
5
6
7
20
20
89
84
2
92
8
2
97
9
2
2
95
81
10
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11
2
85
71
12
13
0.5
0.25
0.25
2
94
91
83
14
15
[a] Reaction conditions: alcohol (0.5 mmol), thiol (0.6 mmol) and [BsCtP][OTf] (10 mol%, according to alcohol) dissolved in 2 mL of 1,2-dichloroethane were
stirred at room temperature for certain time. [b] Isolated yields. [c] GC yield, biphenyl as internal standard.
Subsequently,
the
reactions
of
(4-
reactivities (Table 3, entries 1-4). And 71% yield could be
obtained even with phenylmethanethiol as the substrates just
with 0.25 h (Table 3, entry 5). Besides, a series of aliphatic thiols
afforded the corresponding products in excellent yields within
0.5 h (Table 3, entries 6-11). And the results indicated that there
is a peak value when the carbon chain length of the substrate is
about six (Table 3, entry 7). Additionally, ethane-1,2-dithiol also
provided good yield, up to 93% within 0.5 h (Table 3, entry 11).
methoxyphenyl)(phenyl)methanol and a series of thiols were
examined shown in Table 3. Interestingly, either aromatic or
aliphatic thiols exhibited high activities, giving high yields within
0.5 h at room temperature. Firstly, several aromatic thiols were
investigated. The results indicated that the electron properties
and the steric hindrance of the substituted groups on the phenyl
rings of benzohydrol derivatives have small influence on the
Table 3. Thiolation of (4-methoxyphenyl)(phenyl)methanol with a series of thiols catalyzed by [BsCtP][OTf].[a]
Entry
1
Thiol
Product
t (h)
0.25
Yield (%)[b]
93
2
0.25
99
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3
0.25
0.25
96
90
4
5
6
0.25
0.5
0.5
0.5
0.5
0.5
71
89
96
95
93
85
7
8
9
10
11
0.5
93
[a] Reaction conditions: (4-methoxyphenyl)(phenyl)methanol (0.5 mmol), thiol (0.6 mmol) and [BsCtP][OTf] (10 mol%, according to alcohol) dissolved in 2
mL of 1,2-dichloroethane were stirred at room temperature for certain time. [b] Isolated yields.
Delightedly, the catalytic system was also suitable for the
thiolation of aromatic primary and secondary alcohols with a
series of benzothiazole-2-thiol, although the progress needed
more time (Table 4). Aromatic secondary alcohols exhibited
better activity than that of aromatic primary alcohols (Table 4,
entries 1 vs 2-4). Up to 92% yield could be obtained with
benzothiazole-2-thiol and (4-methoxyphenyl)(phenyl)methanol
as the substrates at room temperature for 2 h (Table 4, entry 1).
And the steric hindrance of the substituted groups on the phenyl
rings of primary alcohol has certain effect on the activities (Table
4, entries 2-4). o-Substituted group led to the decrease of the
yield (Table 4, entry 3). The activities of 5-NO2-benzothiazole-2-
thiol also has similar regular. However, electron withdrawing
group was not beneficial for the reaction. And about 80% yields
could be obtained after prolonging the reaction time to 12 or 24
h (Table 4, entries 5-7). In addition, the activities of the reactions
of aromatic primary or secondary alcohols and 5-methoxy
benzothiazole-2-thiol were similar (Table 4, entries 8-10).
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Table 4. Thiolation of aromatic primary and secondary alcohols with a series of benzothiazole-2-thiol.[a]
Entry
1
Alcohol
Thiol
Product
t (h)
Yield
(%)[b]
2
92
2
3
12
12
94
84
4
5
12
12
91
81
6
7
24
79
24
12
87
89
8
9
12
12
94
86
10
[a] Reaction conditions: alcohol (0.5 mmol), benzothiazole-2-thiol derivertive (0.6 mmol) and [BsCtP][OTf] (10 mol%, according to alcohol) dissolved in 2 mL of
1,2-dichloroethane were stirred at room temperature for certain hours. [b] Isolated yields.
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Subsequently, a series of catalytic recycle were also tested for
the thiolation of (4-methoxyphenyl)(phenyl)methanol with benzo
oxazole-2-thiol by employing [BsCtP][OTf] as the catalyst. In
each cycle, the solvent was removed firstly by rotary evaporator.
Then the separation of the catalyst and the product could be
easily achieved via extraction with ethyl acetate and the catalyst
was dried in vacuum, and the recovered catalyst could be
reused for subsequent reaction directly. Interestingly, the yield
was changed from 97% to 92% after six runs (Figure 3). That’s
to say, the catalyst could be reused for at least six times with
slight loss
Scheme 3. Proposed mechanism for the thiolation of alcohols.
may have synergistic effect. Moreover, the results indicated that
the activities of secondary alcohols were usually better than that
of primary alcohols (Table 4). The phenomena also
demonstrated that stabilized carbocations would be benefit for
the reaction. Then substrate 4 would react with 3 by the
nucleophilic attack, generating the desired product. On the other
hand, 3 also could react with 1 to produce intermediate 6 and 6’,
which further react with material 4 to provide 5. And some
control experiments were carried out to prove our speculation
(Scheme 4). Intermediate 6 could be detected under our
optimized reaction conditions with lower reaction rate. And the
desired product was obtained from intermediate 6 and thiol
under some reaction conditions.
Figure 3. The recyclability of [BsCtP][OTf] in thiolation of (4-
methoxyphenyl)(phenyl)methanol with benzooxazole-2-thiol.
Scheme 4. Control experiments for the thiolation of alcohols.
of its catalytic activity. Subsequently, we examined the
scalability of our catalytic system by employing (4-
methoxyphenyl)(phenyl)methanol and benzooxazole-2-thiol as
the substrates under optimized reactions (Scheme 2).
Interestingly, 1.64 g of the desired product was obtained with
only slightly decrease in yield (94% vs 97%).
Conclusions
We have developed a metal-free and efficient protocol by
employing muti-functionalized ionic liquids (long chain and acid)
derived from pyrrolidine as the catalyst for the thiolation of
alcohols. The system was suitable for the reaction of aromatic
primary and secondary alcohols with benzooxazole-2-thiol,
benzothiazole-2-thiol, aromatic and aliphatic thiols, providing the
corresponding products with up to 99% yield within 0.25 h at
room temperature. Cations, anions and the chain length of ionic
liquids based on pyrrolidine have certain relationship with their
corresponding activities. Moreover, [BsCtP][OTf] exhibited good
recyclability and there was just small decrease in yield after six
runs. And the gram-scale reaction was also successfully
demonstrated. Besides, a mechanism involving carbocation was
proposed. Developing new reactions catalyzed by muti-
functionalized ionic liquids is in progress in our laboratory.
Scheme 2. Scale-up experiment.
According to previous research and the above results,[22,23] we
proposed a possible mechanism for the thiolation of alcohols
(Scheme 3). Carbocations may be the key intermediate. Initially,
the acidic condition was very important for the reaction (Table 1,
entry1-3 vs 4-12) and there is certain interaction between the
proton of the ionic liquids and hydroxyl of the alcohols, which is
beneficial for the formation of intermediate 2. Meanwhile,
Experimental Section
-
CF3SO3 would stabilize the cations 2 and 3. During the
General
formation of carbocations, anion and cation of the ionic liquids
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NMR spectra were recorded on BRUKER AVANCETM III spectrometers.
1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were obtained as
solutions in CDCl3 or D2O. Chemical shifts were reported in parts per
million (ppm, δ) and referenced to CHCl3 (δ 7.26) or D2O (δ 4.88). GC-
MS analyses were performed using an Agilent 6850 system (FID) and ion
source of mass spectrometer is EI. Mass spectra (MS) were recorded on
Waters ZQ4000 mass instrument (ESI). IR spectra were recorded by FT-
IR spectroscopy Nexus 870.
2-((4-methoxyphenyl)(phenyl)methylthio)benzo[d]oxazole[38]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.81 (s, 1H), 6.50 (d, J = 7.6 Hz,
1H), 6.86-6.90 (m, 2H), 6.98-7.02 (m, 1H), 7.14-7.27 (m, 6H), 7.34-7.37
(m, 3H), 7.53(s, 1H).13C NMR (100 MHz, CDCl3) δ 55.3, 64.6, 110.4,
112.2, 114.2, 123.9, 124.5, 128.2, 128.4, 128.8, 130.0, 131.1, 136.4,
147.1, 159.6, 181.0.
2-((4-chlorophenyl)(phenyl)methylthio)benzo[d]oxazole[38]
Most chemicals used for synthetic procedures were reagent grade and
the residue were purified using a silica gel column unless specified
otherwise. All reactions were monitored by TLC with silica gel coated
plates and detected by UV absorption (254 nm). And silica gel (200-300
microns) was used for all chromatography.
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 6.32 (s, 1H), 7.17-7.28 (m,
5H), 7.30-7.38 (m, 3H), 7.43-7.45 (m, 4H), 7.45-7.56 (m, 1H); 13C NMR
(100 MHz, CDCl3) δ 54.5, 109.9, 118.7, 124.1, 124.3, 128.0, 128.2, 128.7,
128.8, 129.7, 133.5, 138.6, 139.3, 141.7, 151.7, 163.0.
Preparation procedure for ionic liquids of N-cetyl-[N-(4-sulfonbutyl)
pyrrolidine] trifluoromethanesulfonate ([BsCtdP][OTf])
2-((3-chlorophenyl)(phenyl)methylthio)benzo[d]oxazole[38]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 6.32 (s, 1H), 7.15-7.26 (m,
5H), 7.29-7.41 (m, 4H), 7.43-7.45 (m, 2H), 7.50 (s, 1H), 7.54-7.56 (m,
1H); 13C NMR (100 MHz, CDCl3) δ 54.7, 110.0, 118.8, 124.2, 124.4,
126.6, 128.0, 128.1, 128.3, 128.5, 128.9, 130.0, 134.6, 139.2, 141.8,
142.2, 151.8, 163.0.
N-cetyl pyrrolidine (5.90 g, 0.020 mol) and 1,4-butane sultone (2.25 mL,
0.022 mol) were charged into a 100 mL round bottom flask and stirred at
40 °C for 10 h. The formed white solid zwitterion was washed repeatedly
with ether and ethyl acetate to remove any unreacted starting materials
and dried in vacuum. Then,
a
stoichiometric amount of
trifluoromethanesulfonic acid (1.80 mL, 0.020 mol) was added dropwisely
to the above intermediate dissolved in toluene and the mixture was
stirred for 12 h at 80 oC, resulting in the formation of N-cetyl-[N-(4-
sulfonbutyl)pyrrolidine] trifluoromethanesulfonate ([BsCtP][OTf]). The
ionic liquid phase was washed repeatedly with ethyl acetate to remove
non-ionic residues, and dried in vacuum. The ionic liquid (11.2 g, 96%
yield) was formed quantitatively with high purity as assessed by NMR, IR
and MS spectroscopy. 1H NMR (400 MHz, D2O)  0.76 (t, J = 5.6 Hz, 2H),
1.18-1.23 (m, 27H), 1.59-1.77 (m, 5H), 2.05-2.10 (m, 4H), 2.79 (t, J = 7.2
Hz, 3H), 3.12-3.23 (m, 4H), 3.42-3.50 (m, 4H); 13C NMR (100 MHz, D2O)
 13.8, 21.5, 21.7, 22.7, 23.1, 24.2, 26.3, 29.2, 29.6, 29.8, 29.9, 30.0,
30.1, 30.2, 32.1, 50.1, 59.2, 59.6, 62.8, 72.0, 89.6, 118.3, 121.4, 202.8;
IR: 3321, 2952, 1628, 1589, 1459, 1407, 1291, 1228, 1165, 1059, 1028,
897, 761, 719, 638, 573, 574, 478; MS (ESI): [m/z]+ = 399.1, [m/z]- =
148.9.
2-((2-chlorophenyl)(phenyl)methylthio)benzo[d]oxazole[38]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 6.79 (s, 1H), 7.17-7.27 (m,
5H), 7.30-7.34 (m, 2H), 7.37-7.39 (m, 2H), 7.47-7.49 (m, 2H), 7.51-7.56
(m, 1H), 7.67 (dd, J = 2.0, 7.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
51.8, 109.9, 118.9, 124.0, 124.3, 127.2, 127.9, 128.5, 128.7, 129.0,
129.8, 130.0, 133.9, 137.5, 138.4, 141.8, 151.8, 162.9.
2-(bis(4-chlorophenyl)methylthio)benzo[d]oxazole[38]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 6.29 (s, 1H), 7.21-7.27 (m,
1H), 7.28-7.32 (m, 4H), 7.39-7.46 (m, 6H), 7.55-7.57 (m, 1H); 13C NMR
(100 MHz, CDCl3) δ 53.8, 110.0, 118.8, 124.3, 124.4, 129.0, 129.7, 133.9,
138.0, 141.6, 151.7, 162.6.
2-(bis(4-methoxyphenyl)methylthio)benzo[d]oxazole[38]
Representative procedure for the thiolation of alcohols
White solid, 1H NMR (400 MHz, CDCl3) δ 3.80 (s, 6H), 6.52 (d, J = 7.6 Hz,
1H), 6.86-6.89 (m, 4H), 6.99-7.03 (m, 1H), 7.14-7.20 (m, 5H), 7.34 (d, J =
8.0 Hz, 1H), 7.46 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 55.3, 64.1, 110.4,
112.2, 114.1, 123.9, 124.5, 128.4, 129.7, 131.1, 147.1, 159.5, 180.9.
Alcohol (0.5 mmol), thiol (0.6 mmol) and catalyst (10 mol%, according to
alcohol) were added into a Schlenk tube in 1,2-dichloroethane (2 mL)
and stirred at room temperature for certain time. Then the reaction
solution was subjected to GC analysis or silicon column to determine the
product yield.
2-(4-methoxybenzylthio)benzo[d]oxazole[39]
The NMR data of the products
White solid, 1H NMR (400 MHz, CDCl3) δ 3.80 (s, 3H), 4.54 (s, 2H), 6.85-
6.88 (m, 2H), 7.23-7.32 (m, 2H), 7.37-7.45 (m, 3H), 7.62-7.64 (m, 1H);
13C NMR (100 MHz, CDCl3) δ 36.2, 55.3, 109.9, 14.2, 118.4, 124.0,
124.3, 127.7, 130.3, 141.8, 151.8, 159.3, 1647.
2-(benzhydrylthio)benzo[d]oxazole[38]
White solid, 1H NMR (400 MHz, CDCl3) δ 6.35 (s, 1H), 7.17-7.26 (m, 4H),
7.30-7.39 (m, 5H), 7.49 (d, J = 8.0 Hz, 4H), 7.55 (d, J = 7.6 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ 55.2, 109.9, 118.7, 124.0, 124.2, 127.7, 128.3,
128.7, 140.0, 141.9, 157, 163.4.
2-(3,4-dimethoxybenzylthio)benzo[d]oxazole[39]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.86 (s, 3H), 3.87 (s, 3H), 4.53
(s, 2H), 6.81 (d, J = 8.8 Hz, 1H), 6.99-7.01 (m, 2H), 7.22-7.31 (m, 2H),
7.44 (d, J = 7.6 Hz, 1H), 7.62 (d, J = 7.2 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 36.7, 55.8, 55.9, 109.9, 111.2, 112.2, 118.4, 121.5, 124.0,
124.3, 128.1, 141.9,148.8, 149.0, 151.8, 164.6.
2-(phenyl(4-tolyl)methylthio)benzo[d]oxazole[38]
White solid, 1H NMR (400 MHz, CDCl3) δ 2.36 (s, 3H), 6.51 (d, J = 8.0 Hz,
1H), 6.98-7.02 (m, 1H), 7.15-7.19 (m, 5H), 7.25-7.28 (m, 2H), 7.34-7.36
(m, 4H), 7.55 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 21.2, 64.8, 123.9,
124.5, 128.4, 128.5, 128.6, 128.8, 129.5, 131.1, 133.1, 136.3, 138.4,
147.1.
2-(4-(phenoxymethyl)benzylthio)benzo[d]oxazole[39]
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10.1002/ejoc.201900169
European Journal of Organic Chemistry
FULL PAPER
White solid, 1H NMR (400 MHz, CDCl3) δ 4.54 (s, 2H), 5.05 (s, 2H), 6.92-
6.95 (m, 2H), 7.23-7.45 (m, 10H), 7.62-7.64 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ 36.2, 70.1, 109.9, 115.1, 118.4, 124.0, 124.4, 127.5, 127.9,
128.0, 128.6, 130.4, 136.8, 141.7, 151.8, 158.6, 164.8.
benzyl((4-methoxyphenyl)(phenyl)methyl)sulfane[43]
White solid, 1H NMR (400 MHz, CDCl3) δ 2.34 (s, 3H), 3.77 (s, 3H), 5.49
(s, 1H), 6.81-6.83 (m, 2H), 6.96-6.99 (m, 4H), 7.01-7.12 (m, 5H), 7.29-
7.41 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 20.4, 55.3, 113.9, 55.68,
126.1, 126.3, 127.2, 128.3, 128.5, 129.5, 129.6, 130.0, 133.1, 135.7,
137.8, 141.2, 158.7.
benzhydryl(phenyl)sulfane[40]
White solid, 1H NMR (400 MHz, CDCl3) δ 5.54 (s, 1H), 7.10-7.24 (m, 7H),
7.29 (t, J = 7.6 Hz, 4H), 7.41 (d, J = 7.6 Hz, 4H); 13C NMR (100 MHz,
CDCl3) δ 57.4, 126.6, 127.2, 128.4, 128.5, 128.7, 130.5, 136.1, 141.0.
ethyl((4-methoxyphenyl)(phenyl)methyl)sulfane[44]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 1.11 (t, J = 7.6 Hz, 3H),
2.29 (q, J = 7.2 Hz, 2H), 3.65 (s, 3H), 5.06 (s, 1H), 6.72-6.76 (m, 2H),
7.09-7.12 (m, 1H), 7.18-7.26 (m, 4H), 7.32 (d, J = 7.6 Hz, 2H); 13C NMR
(100 MHz, CDCl3) δ 13.2, 25.2, 52.0, 54.2, 112.8, 125.9, 127.2, 127.4,
128.3, 132.5, 140.8, 157.5.
phenyl(phenyl(p-tolyl)methyl)sulfane[40]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 2.30 (s, 3H), 5.52 (s, 1H),
7.08-7.24 (m, 9H), 7.28-7.31 (m, 3H), 7.40 (d, J = 7.6 Hz, 2H); 13C NMR
(100 MHz, CDCl3) δ 21.1, 57.1, 126.4, 127.1, 128.2, 128.4, 128.5, 128.7,
129.2, 130.3, 136.4, 136.9 138.0 141.2.
hexyl((4-methoxyphenyl)(phenyl)methyl)sulfane[41]
((4-chlorophenyl)(phenyl)methyl)(phenyl)sulfane[40]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 0.57 (t, J = 6.8 Hz, 3H),
1.18-1.35 (m, 6H), 1.49-1.57 (m, 2H), 2.35 (t, J = 7.2 Hz, 2H), 3.71 (s,
3H), 5.10 (s, 1H), 6.79-6.83 (m, 2H), 7.15-7.19 (m, 1H), 7.25-7.33 (m,
4H), 7.40 (d, J = 7.2 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 14.2, 22.6,
28.7, 29.1, 31.5, 32.4, 53.6, 55.3, 113.9, 127.1, 128.3, 128.6, 129.4,
133.8, 142.0, 158.7.
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 5.49 (s, 1H), 7.13-7.38 (m,
14H); 13C NMR (100 MHz, CDCl3) δ 56.9, 126.9, 127.5, 128.4, 128.7,
128.9, 129.8, 130.8, 133.1, 135.7, 139.7, 140.6.
(4-methoxybenzyl)(phenyl)sulfane[41]
((4-methoxyphenyl) (phenyl) methyl)(octyl)sulfane[41]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.78 (s, 3H), 4.07 (s, 2H), 6.80-
6.83 (m, 2H), 7.15-7.31 (m, 7H); 13C NMR (100 MHz, CDCl3) δ 38.5, 55.3,
113.9, 126.3, 128.8, 129.4, 129.8, 129.9, 136.6, 158.8.
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 0.87 (t, J = 6.8 Hz, 3H),
1.21-1.35 (m, 10H), 1.50-1.57 (m, 2H), 2.36 (t, J = 7.2 Hz, 2H), 3.76 (s,
3H), 5.11 (s, 1H), 6.81-6.85 (m, 2H), 7.18-7.23 (m, 1H), 7.27-7.35 (m,
4H), 7.41 (d, J = 7.6 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 14.1, 22.7,
28.9, 29.1, 29.2, 31.8, 32.3, 53.5, 55.3, 113.9, 127.0, 128.3, 128.5, 129.4,
133.8, 142.0, 158.6.
(4-chlorophenyl)((4-methoxyphenyl)(phenyl)methyl)sulfane[41]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.77 (s, 1H), 5.47 (s, 1H), 6.80-
6.84 (m, 2H), 7.13 (s, 4H), 7.20-7.32 (m, 5H), 7.38-7.40 (m, 2H); 13C
NMR (100 MHz, CDCl3) δ 55.3, 57.0, 114.0, 127.3, 128.3, 128.6, 128.9,
129.5, 132.0, 132.6, 134.7, 140.9, 158.8.
dodecyl ((4-methoxyphenyl)(phenyl)methyl)sulfane[41]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 0.88 (t, J = 6.4 Hz, 3H),
1.23-1.30 (m, 18H), 1.50-1.57 (m, 2H), 2.36 (t, J = 7.2 Hz, 2H), 3.75 (s,
3H), 5.10 (s, 1H), 6.81-6.85 (m, 2H), 7.17-7.22 (m, 1H), 7.27-7.34 (m,
4H), 7.40 (d, J = 7.6 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 14.2, 32.7,
28.9, 29.1, 29.2, 29.4, 29.5, 29.6, 29.7, 29.7, 32.0, 32.4, 53.5, 55.3,
113.9, 127.0, 128.3, 128.5, 129.4, 133.8, 142.0, 158.6.
(4-methoxyphenyl)((4-methoxyphenyl)(phenyl)methyl)sulfane[41]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.74 (s, 3H), 3.76 (s, 3H), 5.32
(s, 1H), 6.69-6.73 (m, 2H), 6.79-6.83 (s, 2H), 7.18-7.22 (m, 3H), 7.25-
7.30 (m, 4H), 7.37 (d, J = 7.2 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 55.3,
58.6, 113.8, 114.3, 126.1, 127.0, 128.3, 128.4, 129.5, 133.4, 134.6,
141.6, 158.6, 159.3.
((4-methoxyphenyl)(phenyl)methyl)(octadecyl)sulfane[41]
White solid, 1H NMR (400 MHz, CDCl3) δ 0.89(t, J = 6.8 Hz, 3H), 1.24-
1.26 (m, 30H), 1.51-1.58 (m, 2H), 2.37 (t, J = 7.2 Hz, 2H), 3.78 (s, 3H),
5.11 (s, 1H), 6.84 (d, J = 8.4 Hz, 2H), 7.21-7.43 (m, 7H); 13C NMR (100
MHz, CDCl3) δ 22.7, 28.9, 29.1, 29.2, 29.4, 29.5, 29.6, 29.7, 29.7, 29.7,
31.9, 32.3, 53.5, 55.2, 113.9, 127.0, 128.2, 128.5, 129.3 133.7, 141.9,
158.6.
((4-methoxyphenyl)(phenyl)methyl)(p-tolyl)sulfane[41]
White solid, 1H NMR (400 MHz, CDCl3) δ 2.33 (s, 3H), 3.68 (s, 3H), 5.48
(s, 1H), 6.77-6.80 (m, 2H), 6.92-7.01 (m, 2H), 7.07-7.11 (m, 2H), 7.15-
77.18 (m, 1H), 7.22-7.31 (m, 4H), 7.37-7.40 (m, 2H); 13C NMR (100 MHz,
CDCl3) δ 20.6, 55.3, 55.9,114.0, 126.2, 126.4, 127.3, 128.5, 128.7, 129.7,
129.8, 130.1, 133.2, 135.8, 137.9, 141.4, 158.9.
1,2-bis((4-methoxyphenyl)(phenyl)methylthio)ethane[44]
((4-methoxyphenyl)(phenyl)methyl)(naphthalen-2-yl)sulfane[42]
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 2.53 (s, 4H), 3.74 (s, 6H),
5.05 (s, 2H), 6.79-6.83 (m, 4H), 6.18-6.22 (m, 2H), 7.12-7.29 (m, 8H),
7.33-7.35 (m, 4H); 13C NMR (100 MHz, CDCl3) δ 32.0, 53.5, 55.3, 114.0,
127.2, 128.3, 128.6, 129.4, 133.3, 141.5, 158.8.
White solid, 1H NMR (400 MHz, CDCl3) δ 3.75 (s, 3H), 5.64 (s, 1H), 6.82
(d, J = 8.8 Hz, 2H), 7.19-7.45 (m, 10H), 7.60-7.65 (m, 3H), 7.71-7.73 (m,
1H); 13C NMR (100 MHz, CDCl3) δ 55.2, 56.7, 113.9, 125.8, 126.3, 127.2,
127.3, 127.6, 128.0, 128.1, 128.4, 128.6, 128.7, 129.5, 131.9, 133.0,
133.6, 133.8, 141.2, 158.7.
2-((4-methoxyphenyl)(phenyl)methylthio)benzo[d]thiazole[41]
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900169
European Journal of Organic Chemistry
FULL PAPER
White solid, 1H NMR (400 MHz, CDCl3) δ 3.79 (s, 3H), 6.85-6.89 (m, 2H),
6.92 (d, J = 8.4 Hz, 1H), 7.03-7.07 (m, 1H), 7.16-7.20 (m, 1H), 7.23-7.28
(m, 4H), 7.31-7.35 (m, 3H), 7.45 (dd, J = 0.8, 8.0 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ 55.3, 63.5, 114.1, 115.7, 121.1, 124.3, 126.0, 127.0,
127.9, 128.2, 128.3, 128.7, 129.9, 136.4, 140.9, 159.3, 190.7.
63.6, 101.1, 112.3, 114.2, 118.2, 121.3, 128.0, 128.3, 128.8, 129.9,
136.6, 142.1, 158.4, 159.3, 191.6.
5-methoxy-2-(4-methoxybenzylthio)benzo[d]thiazole[27]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.79 (s, 3H), 3.88 (s, 3H), 4.55
(s, 2H), 6.84-6.88 (m, 2H), 6.95 (dd, J = 2.4, 8.8 Hz, 1H), 7.36-7.43 (m,
3H), 7.59 (d, J = 8.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 37.5, 55.3,
55.7, 104.5, 114.0, 114.1, 121.2, 126.9, 127.9, 130.3, 154.2, 159.0,
159.2, 167.9.
2-(4-methoxybenzylthio)benzo[d]thiazole[27]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.79 (s, 3H), 4.58 (s, 2H), 6.84-
6.88 (m, 2H), 7.29-7.33 (m, 1H), 7.36-7.45 (m, 3H), 7.75 (d, J = 8.0 Hz,
1H), 7.92 (d, J = 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 37.5, 55.3,
114.1, 121.0, 121.4, 124.4, 126.2, 127.9, 130.4, 135.1, 152.8, 159.2,
166.9.
5-methoxy-2-(2-methoxybenzylthio)benzo[d]thiazole[27]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.86 (s, 3H), 3.88 (s, 3H), 4.62
(s, 2H), 6.88-6.94 (m, 3H), 7.24-7.29 (m, 1H), 7.43-7.46 (m, 2H), 7.57 (d,
J = 8.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 38.3, 55.5, 55.6, 104.5,
110.6, 113.9, 120.5, 121.1, 124.5, 126.9, 129.3, 130.7, 154.3, 157.6,
158.9, 168.7.
2-(2-methoxybenzylthio)benzo[d]thiazole[45]
White solid, 1H NMR (400 MHz, CDCl3) δ 3.86 (s, 3H), 4.63 (s, 2H), 6.89
(t, J = 7.2 Hz, 2H), 7.24-7.30 (m, 2H), 7.39-7.47 (m, 2H), 7.73 (d, J = 7.6
Hz, 1H), 7.91 (d, J = 7.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 32.7,
55.5, 110.6, 120.6, 130.0, 121.5, 124.2, 124.6, 126.0, 129.3, 130.8,
135.3, 153.2, 157.6, 167.5
Acknowledgments
2-(3,4-dimethoxybenzylthio)benzo[d]thiazole[27]
This work was supported by the National Natural Science
Foundation of China (No. 21303231, 21173241, 21673259 and
21133011), Natural Science Foundation of Jiangsu Province
(BK20161261 and BK20171241), Foundation of State Key
Laboratory of High-efficiency Utilization of Coal and Green
Chemical Engineering (Grant NO. 2018K31) and Shandong
Agricultural University.
Colorless liquid, 1H NMR (400 MHz, CDCl3) δ 3.84 (s, 3H), 3.85 (s, 3H),
4.55 (s, 2H), 6.79 (d, J = 8.0 Hz, 1H), 6.97-7.01 (m, 2H), 7.26-7.30 (m,
1H), 7.39-7.43 (m, 1H), 7.73 (d, J = 8.0 Hz, 1H), 7.89 (d, J = 8.0 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ 37.8, 55.8, 55.9, 111.1, 112.2, 121.0,
121.4, 121.5, 124.3, 126.1, 128.4, 135.3, 148.6, 148.9, 153.1, 166.5 .
2-(((4-Methoxyphenyl)(phenyl)methyl)thio)-5-
nitrobenzo[d]thiazole[41]
Keywords: Long chained acid-functionalized ionic liquids
•Pyrrolidine• Thiolation•Alcohols• Thiols
White solid, 1H NMR (400 MHz, CDCl3) δ 3.81 (s, 3H), 6.86-6.91 (m, 2H),
6.98 (d, J = 9.2 Hz, 1H), 7.19-7.24 (m, 4H), 7.35-7.40 (m, 3H), 7.95 (dd, J
= 2.4, 9.2 Hz, 1H), 8.29 (s, 1H), 8.34 (d, J = 2.0 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ 55.3, 63.9, 114.4, 114.8, 116.8, 122.0, 127.4, 127.8,
128.1, 128.4, 129.1, 129.8, 135.7, 144.2, 145.2, 159.6, 192.3.
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10.1002/ejoc.201900169
European Journal of Organic Chemistry
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Long chained and SO3H-
Thiolation *
functionalized ionic liquids derived
from pyrrolidine were employed as
metal-free, efficient and recyclable
catalyst for thiolation of alcohols with
several kinds of thiols, providing up to
99% yield within 0.25 h at room
temperature.
Chengxia Miao, Hongfeng Zhuang,
Yating Wen, Feng Han,* Qing-Feng
Yang, Lei Yang, Zhen Li, and Chungu
Xia*
Page No. – Page No.
Efficient Thiolation of Alcohols
Catalyzed by Long Chained Acid-
functionalized Ionic Liquids under
Mild Conditions
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