Cu-Catalyzed Oxidative Thioesterification of Aroylhydrazides with Disulfides

Article abstract of DOI:10.1021/acs.joc.0c02328

An alternative thioesterification reaction via copper-catalyzed oxidative coupling of readily available aroylhydrazides with disulfides is developed, in which oxidative expulsion of N2 overcomes the activation barrier between the carboxylic acid derivativ

Full text of DOI:10.1021/acs.joc.0c02328

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Article
Cu-Catalyzed Oxidative Thioesterification of Aroylhydrazides with
Disulfides
Shimin Xie,∥ Lebin Su,∥ Min Mo, Wang Zhou, Yongbo Zhou, and Jianyu Dong*
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ABSTRACT: An alternative thioesterification reaction via copper-
catalyzed oxidative coupling of readily available aroylhydrazides with
disulfides is developed, in which oxidative expulsion of N2 overcomes
the activation barrier between the carboxylic acid derivatives and the
products. The reaction produces various thioesters in good to excellent
yields with good functional group tolerance. In the reaction, stable and
easily available aroylhydrazides are used as acyl sources and the
relatively odorless disulfides are used as S sources. Mechanistic
investigations demonstrate that the reaction of copper salt and oxidant
(NH4)2S2O8 allows for achievement of tandem processes, including
deprotonation, free-radical-mediated denitrogenation, and C−S bond formation.
frequently used. However, these methods often suffer from
some disadvantages, such as the use of toxic, inaccessible, and/
or difficult-to-handle substrates and limitations of the
substrates. Undoubtedly, use of stable and easily available
carboxylic acids and their derivatives as acyl sources is an ideal
choice for the direct synthesis of thioesters.
INTRODUCTION
■
Thioesters are important structural units found in a broad
range of pharmaceuticals and natural products, and thioesters
bearing functional groups with sulfur display unique biological
properties (Figure 1).1,2 This kind of compounds are also
frequently used as an acyl transfer reagent in synthetic
chemistry and chemical biology.3
However, there have only been a few reports demonstrating
this strategy.9−12 The underdevelopment of this strategy is due
to the thermodynamic disfavor,9a,13 in which, owing to the
strong conjugation effect, the acyl C−O/or C−N bond of the
common carboxylic acids and their derivatives is more stable
than the acyl C−S bond of thioesters. Indeed, previous studies
have employed substrates that have a decreased activation
barrier (Scheme 1a−c), which leads to the use of specially
structured substrates (or in situ formed).9b,11,12 For example,
Plietker’s work limits to the p-chloro-substituted aryl esters.11
Our previous procedure requires the use of specially structured
amides, i.e., 1-benzoylpyrrolidine-2,5-dione derivatives, which
contain two strong electron-drawing groups (Scheme 1b).12
Lin’s reaction relies on the assistance of hydrosilanes to form
reactive species (RCOOSi, Scheme 1c).9b Therefore, develop-
ment of a simple and general approach for the generation of
thioesters from carboxylic acid derivatives is still highly
attractive and desirable.
Figure 1. Representative bioactive compounds bearing thioester
structures.
Over the past three decades, several strategies4−12 have been
developed, leading to more than 100 methods for the synthesis
of thioesters. Among them, nucleophilic substitution of acyl
chlorides/anhydrides with thiols/disulfides,5 direct coupling of
aldehydes with thiols/disulfides,6 thiocarbonylation of aryl
halides with CO,7 and decarboxylation coupling of α-keto
acids with thiols/disulfides8 have been well developed and are
Received: September 30, 2020
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phenyl 4-methoxybenzothioate (3a) was obtained in 70% gas
chromatography (GC) yield (Table 1, entry 1, yield based on
Scheme 1. Synthesis of Thioesters from Carboxylic Acids
and Their Derivatives
a
Table 1. Optimization of the Reaction Conditions
b
entry
catalyst
Cul
CuCl
oxidant
solvent
temp (°C) yield (%)
1
2
3
4
5
6
7
8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
K2S2O8
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
THF
CH3CN
DCE
DMF
DMSO
DMSO
DMSO
DMSO
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
80
70
71
72
70
93
74
69
78
75
16
68
82
6
CuBr
Cu2O
CuCN
CuCl2
CuBr2
Cu(OAc)2
CuO
9
10
11
12
13
14
15
16
17
18
19
20
21
22
−
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
CuCN
Na2S2O8
DTBP
TBHP
O2
8
25
10
20
33
23
trace
42
83
11
0
Ag2CO3
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
(NH4)2S2O8
-
Herein, as a continuation of our interest in copper
catalysis,14 we report a facile and general approach for
accessing thioesters via Cu-catalyzed cross-coupling of readily
available aroylhydrazides with disulfides (Scheme 1d). This
reaction produces a variety of functionalized thioesters in good
to excellent yields with broad substrate scope and good
functional group tolerance under mild conditions. Different
from known methods, this reaction overcomes the activation
barrier by the oxidative expulsion of N2. Subsequent release of
acyl radicals allows incorporation of both S atoms of the
disulfide into the desired products.
Aroylhydrazides are readily accessible carboxylic acid
derivatives. Compared with other types of carboxylic acid
derivatives, simple aroylhydrazides are stable solids and
compatible with moisture. Due to their easy availability and
handling, aroylhydrazides have been proven to be powerful and
versatile building blocks in organic synthesis15−17 by
functioning as aryl,15 acyl,16 and N sources.17 In contrast,
there have been a few reports on the use of aroylhydrazides as
acyl sources.18 It was noted that the strategy for overcoming
the activation barrier by expulsion of CO2 had been reported.8a
However, this method employs α-oxocarboxylic acids as
substrates, which are not simple and easily available carboxylic
acids. Moreover, the known approach involves decarboxylation
via C−C bond cleavage, and the acyl radicals in the reaction
derive from α-keto of α-oxocarboxylic acids, other than
carboxylic groups. Furthermore, it requires 1 equiv of disulfides
(2 equiv of S source) and suffers from a limited scope of
substrates and functional groups. Therefore, the chemistry of
the oxidative thioesterification of aroylhydrazides with
disulfides is quite different from the reported reaction.
120
100
100
c
23
24
a
Reaction conditions: 1a (0.4 mmol, 2.0 equiv, 66.5 mg), 2a (0.1
mmol, 21.8 mg), catalyst (0.02 mmol, 10 mol %, based on 0.2 mmol
of S source), oxidant (0.3 mmol, 1.5 equiv), solvent (1.0 mL) at 100
b
°C for 6 h under N2. GC yields using n-tridecane as an internal
standard. Under air.
c
0.2 mmol of S). The choice of copper catalysts was critical to
this coupling reaction. Cu(I) salts such as CuCl, CuBr, Cu2O,
and CuCN were first investigated, and CuCN gave the highest
yield (93%) (Table 1, entries 2−5). Cu(II) catalysts, CuCl2,
CuBr2, Cu(OAc)2, and CuO also showed good efficiency for
this reaction (Table 1, entries 6−9). In the absence of copper
salt, only 16% GC yield of 3a was obtained, indicating that
copper was essential for the reaction (Table 1, entry 10). An
assessment of oxidants revealed that (NH4)2S2O8 was optimal
for the reaction (Table 1, entry 5), and K2S2O8 and Na2S2O8
also showed good efficiency, whereas di-tert-butyl peroxide
(DTBP), tert-butyl hydroperoxide (TBHP), molecular oxygen,
and Ag2CO3 gave very low yields of 3a (Table 1, entries 11−
16). Other solvents such as tetrahydrofuran (THF), CH3CN,
1,2-dichloroethane (DCE), and N,N-dimethylformamide
(DMF) were inferior to DMSO (Table 1, entries 17−20).
The reaction was also sensitive to the reaction temperature
(Table 1, entries 21 and 22). A slightly lower yield of 3a was
observed at 120 °C. However, a lower reaction temperature
(80 °C) resulted in a lower yield of the product (42%). Under
air, a low yield of the coupling product 3a was observed (Table
1, entry 23). Notably, the reaction did not proceed without
(NH4)2S2O8 (Table 1, entry 24).
RESULTS AND DISCUSSION
■
We commenced our study upon treatment of 4-methox-
ybenzohydrazide (1a) and 1,2-diphenyldisulfane (2a) in the
presence of CuI (10 mol %) and (NH4)2S2O8 (0.3 mmol, 1.5
equiv) in dimethyl sulfoxide (DMSO) at 100 °C for 6 h. S-
B
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After the optimal conditions were determined, we next
investigated the scope of the substrates, and the results are
summarized in Table 2. This Cu-catalyzed cross-coupling of
aroylhydrazides with disulfides produced a wide scope of
substrates and good tolerance toward functional groups,
producing various thioesters in good to excellent yields.
Aromatic disulfides substituted with fluoro (3b), chloro (3c
and 3d), alkyl (3e and 3f), methoxy (3g), and thiomethyl (3h)
groups afforded the corresponding thioesters in 79−96%
yields. Heteroaromatic disulfides containing a furyl group also
reacted efficiently, producing the desired product (3i) in 55%
yield. Aliphatic disulfides were also good substrates, and the
corresponding thioesters were produced in good to excellent
yields (54−90%, 3j−q). Functional groups such as alkyl (3j−
l), cycloalkyl (3m), vinyl (3n), hydroxyl (3o), benzyl (3p),
and furyl (3q) were all tolerated.
a
Table 2. Substrate Scope
For aroylhydrazides, benzoyl hydrazide readily underwent
cross-coupling with alkyl and aryl disulfides, producing the
corresponding thioesters in good yields (3r, 81%; 3s, 65%).
Electron-donating groups on the phenyl rings, such as OMe,
Me, t-Bu, and OBn, significantly facilitated the reaction, and
the desired products (3a and 3t−x) were obtained in 84−92%
yields. In comparison, slightly lower yields were observed when
the aromatic ring contained electron-withdrawing substituents
(3y, 82%; 3za, 63%). This electronic effect is attributed to
electron-donating groups facilitating the formation of the
carbonyl radical (vide infra), whereas electron-withdrawing
groups hindered this process. Furthermore, 3,5-dimethoxy
benzohydrazide reacted efficiently with 1,2-diphenyl disulfide,
giving the target product (3zb) in 70% yield. Notably, NH2
and phenolic hydroxy groups, which are sensitive to oxidants,
were also compatible, and the desired products (3zc−ze) were
isolated in 50, 41, and 39% yields, respectively. 4-
Biphenylcarboxylic acid hydrazide also successfully produced
the corresponding product (3zf) in 57% yield. An o-
heterocycle-based aroylhydrazide was also very suitable for
this transformation (3zg, 80% yield). In addition, the arene
ring was not limited to benzene, as demonstrated by the
isolation of S-phenyl thiophene-2-carbothioate 3zh in good
yield (63%). Notably, functional groups such as NH2, OH, and
furyl are very important and are frequently found in
functionalized thioester derivatives.1a Thus, this method
provides a good alternative to previously reported meth-
ods.4−12 Unfortunately, when pyridyl hydrazide was employed
as the substrate, only a trace of the desired product, S-phenyl
pyridine-2-carbothioate (3zi), was generated, which was
probably due to the strong coordination of the N atom of
pyridine with the copper catalyst. In comparison, aliphatic
hydrazides showed a lower reactivity. For example, treatment
of ethyl carbazate, methyl carbazate, and acethydrazide with 2a
afforded the corresponding products (3zj−zl) in 40, 35, and
21% yields.
a
General reaction conditions: 1 (0.4 mmol, 2.0 equiv), 2 (0.1 mmol),
CuCN (0.02 mmol, 10 mol %, 1.79 mg), and (NH4)2S2O8 (0.3 mmol,
1.5 equiv, 68.5 mg) in DMSO (1.0 mL) at 100 °C for 6 h under N2.
Isolated yields based on 0.2 mmol of S. 12 h. (NH4)2S2O8 (0.6
mmol, 3.0 equiv).
b
c
Thiols are malodorous and very toxic. Another problem
associated with the use of thiols as coupling partners during
C−S bond formation is their propensity to undergo oxidative-
Scheme 2. Thioesterification of Aroylhydrazides with Thiols
C
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self dimerization, inhibiting the desired C−S bond formation.
Thus, replacing thiols with disulfides is a good choice for the
synthesis of thioesters.19 As shown in Scheme 2, an
investigation of the efficiency of the reaction of aroylhydrazides
with thiols was conducted. 4-Methoxybenzohydrazide coupled
with aryl thiols in the presence of 1.5 equiv of the oxidant to
produce the corresponding thioesters in high yields (3b, 3e,
and 3g, 86, 90, and 84% yields, respectively). The reaction of
the aliphatic thiol cyclohexanethiol with 4-methoxybenzohy-
drazide produced the desired thioester (3m) in 45% yield. In
comparison, the reaction efficiency of disulfides was higher
than that of thiols, which was another advantage of this
reaction.
use of an excess Cu(OAc)2 (2.0 equiv) did not produce the
desired product, in spite of the addition of the oxidant
(Scheme 4c). This is likely due to the coordination of Cu(II)
with the N−N double bond of diazene C, which disfavored the
formation of the acyl radical E (vide infra). It has been
reported that diazene C can be easily transformed into acyl
radical E via the N−N double-bond radical D in the presence
of a suitable oxidant.18 Hence, we propose that the copper(II)
salt promoted the oxidation of the aroylhydrazide to diazene C
in the catalytic cycle, while it disfavored the followed processes
(C to E). Indeed, when a stoichiometric amount of Cu(OAc)2·
bipy (7) that Cu(II) has been coordinated to the N atom was
subjected to the reaction, 3a was produced in 14% yield.
Although low, it was an essential improvement in comparison
to Cu(OAc)2. These results further confirmed the suggestion
that Cu(II) salts have a detrimental effect on the reaction via
coordination with the N−N double bond of diazene C, and
thus Cu(II) cannot transform C to the carbonyl radical E.
It was proved that p-MePhSCu(I) (8) was also a good
catalyst for this reaction (90% yield of 3a, Scheme 4e). But, by
the replacement of 1,2-di-p-tolyl disulfide (2e) with 8, the
thioesterification product 3e was only isolated in 21% yield
(Scheme 4e) in the presence of 1.5 equiv of the oxidant. In
addition, the reaction of 1a and 2a with a stoichiometric
amount of 8 produced 3a as a major product (56% yield) and
concomitant generation of 3e as a minor product (11% yield,
Scheme 4f). These results suggested that p-MePhSCu(I) (8)
was not the major intermediate and that the involvement of the
Cu(II) species G (vide infra) that are probably derived from
the combination of sulfur radical F and Cu(I) in the reaction
was a minor pathway.23
To further extend the practicability of this new thioester-
ification reaction, a gram-scale reaction was conducted under
standard reaction conditions, and the reaction successfully
delivered the desired product (3a) in a comparable yield
(1.024 g, 84% yield; Scheme 3a).
Scheme 3. Synthetic Utility
Although the specific mechanism remains unclear, tentative
pathways have been proposed based on the above results and
literature reports (Scheme 5).18,21−23 Initially, homolytic
cleavage of (NH4)2S2O8 produces an ammonium sulfate
radical under the reaction conditions. In the presence of
copper(I) and S2O82−, the cation radical A is generated by
single electron transfer between aroylhydrazide and a copper-
(II) species (Scheme 5, major pathway). Then, sequential
single electron transfer and deprotonation form diazene C via
the radical intermediate B.21 Diazene C further reacts with an
ammonium sulfate radical to generate radical D. By the
expulsion of molecular nitrogen, the radical D quickly turns
into acyl radical E.18,21,22 Then, the acyl radical E subsequently
reacts with disulfide 2 to form thioester 3, concomitantly
generating sulfur radical F (F can also be produced by
homolytic cleavage of disulfide 2).
The desired products are probably produced by another
three pathways: (1) direct combination of acyl radical E and
sulfur radical F; (2) sulfur radical F reacts with Cu(I) to form a
Cu(II) species G,23 then further reacts with acyl radical E to
provide Cu(III) species H, accompanied by a single electron
transfer process. Reductive elimination of Cu(III) species H
delivers thioesterification product 3 and regenerates Cu(I); (3)
ammonium sulfate radical reacts with the aroylhydrazide to
form radical D, and acyl radical E is produced by a release of
N2 by D. Finally, E is converted into thioester 3 by a free-
radical-mediated C−S bond formation (minor pathway, Table
1, entry 10).
Because unsymmetrical aryl thioethers are valuable synthetic
intermediates and pharmaceutically active molecules, the direct
decarbonylative thioetherification of S-(2-methylfuran-3-yl) 4-
methoxy-benzothioate (3i) and S-phenyl benzo[d][1,3]-
dioxole-5-carbothioate (3zg) was investigated, and selective
C−S cleavage/CO extrusion generated the desired unsym-
metrical aryl thioethers 5 and 6 in 96 and 78% yields,
respectively (Scheme 3b,c).20 Therefore, the above results
demonstrated the synthetic value of this method in organic
synthesis.
To gain insights into the mechanism, Cu-catalyzed coupling
of 1a and 2a was performed in the presence of the radical
scavenger TEMPO (2.0 equiv, based on 0.2 mmol; Scheme
4a). The reaction was thoroughly suppressed, suggesting that
the reaction involved a free-radical process. The addition of the
radical scavenger 1,1-diphenylethylene could also block this
reaction, which further confirmed this suggestion. When 2a
was reacted with benzaldehyde, benzoic acid, or benzoic amide
under optimized conditions, no desired product was observed
(Scheme 4b). These results demonstrated that the release of
N2 is essential for the reaction to overcome the activation
barrier and generate the carbonyl radical (vide infra). Copper
salt played different roles in this reaction. A low loading of
copper(I) promoted the reaction efficiency, and 1, 5, and 10
mol % CuCN resulted in increased yields (respectively, 28, 81,
and 93% vs 16%; Scheme 4c). In contrast, higher amounts of
CuCN (20 and 100 mol %) produced much lower yields (57
and 45% vs 93%). Although copper(II) salt could also catalyze
this coupling reaction (10 mol % Cu(OAc)2, 78% yield), the
CONCLUSIONS
In summary, we have developed a new type of thioester-
ification reaction via copper-catalyzed oxidative coupling of
■
D
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Scheme 4. Control Experiments
readily available aroylhydrazides with disulfides, in which
oxidative expulsion of N2 overcomes the activation barrier
between the carboxylic acid derivatives and the products. This
procedure is applicable to a wide range of substrates, including
aromatic, heteroaromatic, and aliphatic disulfides, and is
tolerant to many important functional groups, especially
furans, thiophenes, alkenes, SMe, NH2, and OH. The reaction
proceeds via free-radical-mediated acyl C−N bond cleavage
and C−S bond formation, allowing the incorporation of both S
atoms of disulfides into the desired molecules. Mechanism
investigation reveals that some interesting pathways are
involved in the reaction, in which the reaction of copper salt
and (NH4)2S2O8 allows for achievement tandem processes.
This reaction allows for an efficient, practical, and general
synthesis of thioesters from readily accessible carboxylic acid
derivatives, and the advantages of this reaction, such as the
easy availability of the starting materials, use of odorless
disulfides, no requirement for exotic additives, and facile
operation, make this protocol particularly attractive and
represent a good alternative method to synthesize thioesters.
EXPERIMENTAL SECTION
■
General Information. All reactions were carried out in 25 mL
Schlenk tubes under N2 atmosphere. The heat source is an IKA
magnetic stirrer with RCT Basic. Reagents and solvents were obtained
from commercial sources (Energy Chemical, Alfa Aesar, Aladdin,
Sigma-Aldrich, and J&K Scientific) and used without further
purification. Column chromatography was performed using Silica
Gel 60 (300−400 mesh). The reactions were monitored by GC and
gas chromatography−mass spectrometry (GC−MS). The GC−MS
results were recorded on a GC−MS QP2010, and the GC analysis
E
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Scheme 5. Possible Reaction Mechanism
was performed on a GC 2014 Plus. The 1H, 13C, and 19F NMR
spectra were recorded on Bruker 400 and 500 MHz spectrometers at
20 °C, and chemical shifts were reported in parts per million (ppm).
Electron ionization (EI) method was used for HRMS measurement,
and a time-of-flight (TOF) mass analyzer was used for EI.
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a colorless solid in 89% yield (43.4 mg); mp
92−93 °C. 1H NMR (400 MHz, CDCl3): δ 8.02 (d, J = 8.4 Hz, 2H),
7.54−7.45 (m, 5H), 6.96 (d, J = 8.4 Hz, 2H), 3.87 (s, 3H). 13C{1H}
NMR (100 MHz, CDCl3): δ 188.5, 163.9, 135.1, 129.6, 129.3, 129.3,
129.1, 127.6, 113.9, 55.5.
General Experimental Procedure for the Synthesis of
Thioesters. An oven-dried 25 mL Schlenk tube equipped with a
magnetic stir bar was charged with CuCN (0.02 mmol, 1.79 mg, 10
mol %, based on 0.2 mmol of S source), to which (NH4)2S2O8 (0.3
mmol, 1.5 equiv, 68.5 mg), aryl hydrazide 1 (0.40 mmol, 2.0 equiv),
disulfide 2 (0.1 mmol), and DMSO (0.2 M, 1.0 mL) were added. The
reaction mixture was heated at 100 °C for 6 h under N2. After
completion of the reaction, the reaction mixture was cooled to room
temperature, then washed with saturated NH4Cl aqueous solution
(5.0 mL), and extracted with ethyl acetate (3 × 5 mL). The organic
layer was dried over anhydrous Na2SO4 and concentrated under
vacuum. The desired product 3 was isolated by column chromatog-
raphy (eluent: ethyl acetate/petroleum ether = 1/40−1/20) over
silica gel (300−400 mesh) using petroleum ether−ethyl acetate as an
eluent.
General Experimental Procedure for the Thioesterification
of Aroylhydrazides with Thiols. An oven-dried 25 mL Schlenk
tube equipped with a magnetic stir bar was charged with CuCN (0.02
mmol, 1.79 mg), to which (NH4)2S2O8 (0.3 mmol, 1.5 equiv, 68.5
mg), aryl hydrazide 1 (0.40 mmol, 2.0 equiv), thiol 4 (0.2 mmol), and
DMSO (0.2 M, 1.0 mL) were added. The reaction mixture was heated
at 100 °C for 16 h under N2. After completion of the reaction, the
reaction mixture was cooled to room temperature, then washed with
saturated NH4Cl aqueous solution (5.0 mL), and extracted with ethyl
acetate (3 × 5 mL). The organic layer was dried over anhydrous
Na2SO4 and concentrated under vacuum. The desired product 3 was
isolated by column chromatography (eluent: ethyl acetate/petroleum
ether = 1/40−1/20) over silica gel (300−400 mesh) using petroleum
ether−ethyl acetate as an eluent.
S-(4-Fluorophenyl) 4-Methoxybenzothioate (3b).7b The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (20:1) to afford a colorless solid in 92%
yield (48.2 mg); mp 86−87 °C. 1H NMR (400 MHz, CDCl3): δ 8.00
(d, J = 9.2 Hz, 2H), 7.48 (dd, J = 8.8 Hz, J = 5.6 Hz, 2H), 7.14 (t, J =
8.8 Hz, 2H), 6.95 (d, J = 8.8 Hz, 2H), 3.86 (s, 3H). 13C{1H} NMR
(100 MHz, CDCl3): δ 188.3, 164.0, 163.4 (d, JC‑F = 248 Hz), 137.1
(d, JC‑F = 8.6 Hz), 129.6, 129.0, 122.9 (d, JC‑F = 3.5 Hz), 116.3 (d, JC‑F
= 21.9 Hz), 113.9, 55.4. 19F NMR (376 MHz, CDCl3): δ −111.3 (s,
1F).
S-(3-Chlorophenyl) 4-Methoxybenzothioate (3c). The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (40:1) to afford a yellow oil in 79%
yield (43.9 mg). 1H NMR (400 MHz, CDCl3): δ 7.88 (d, J = 8.4 Hz,
2H), 7.43 (s, 1H), 7.32−7.24 (m, 3H), 6.85 (d, J = 8.8 Hz, 2H), 3.76
(s, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 187.5, 164.1, 134.7,
134.5, 133.2, 130.0, 129.7, 129.4, 129.4, 128.9, 113.9, 55.5. HRMS
(EI) m/z: [M + H+] calcd for C14H12ClO2S+: 279.0241, found:
279.0246.
S-(2-Chlorophenyl) 4-Methoxybenzothioate (3d). The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (20:1) to afford a yellow oil in 81%
yield (45.0 mg). 1H NMR (400 MHz, CDCl3): δ 8.03 (d, J = 8.4 Hz,
2H), 7.61 (d, J = 7.6 Hz, 1H), 7.55 (d, J = 8.0 Hz, 1H), 7.41−7.31
(m, 2H), 6.96 (d, J = 8.4 Hz, 2H), 3.86 (s, 3H). 13C{1H} NMR (100
MHz, CDCl3): δ 186.6, 164.0, 139.0, 137.6, 131.0, 130.1, 129.8,
128.9, 127.2, 113.9, 55.5. HRMS (EI) m/z: [M + H+] calcd for
C14H12ClO2S+: 279.0241, found: 279.0248.
General Procedure for the Synthesis of 5 and 6.20 An oven-
dried 25 mL Schlenk tube equipped with a magnetic stir bar was
charged with a thioester substrate (0.1 mmol), to which Ni(dppp)Cl2
(0.01 mmol, 5.42 mg), Na2CO3 (0.15 mmol, 15.9 mg), and
anhydrous 1,4-dioxane (0.5 mL, 0.2 M) were added. The reaction
mixture was heated at 160 °C for 15 h under N2. After the indicated
time, the reaction mixture was diluted with CH2Cl2 (2 mL), filtered,
and concentrated. The desired product was isolated by column
chromatography (eluent: ethyl acetate/petroleum ether = 1/80) over
silica gel (300−400 mesh) using petroleum ether−ethyl acetate as an
eluent.
S-(p-Tolyl) 4-Methoxybenzothioate (3e).5e The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a yellow solid in 95% yield (49.2
mg); mp 65−66 °C. 1H NMR (400 MHz, CDCl3): δ 8.00 (d, J = 8.8
Hz, 2H), 7.39 (d, J = 7.6 Hz, 2H), 7.25 (d, J = 8.0 Hz, 2H), 6.93 (d, J
= 8.4 Hz, 2H), 3.84 (s, 3H), 2.39 (s, 3H). 13C{1H} NMR (100 MHz,
CDCl3): δ 188.9, 163.8, 139.5, 135.0, 129.9, 129.6, 129.4, 123.9,
113.8, 55.4, 21.3.
1H, 13C, and 19F NMR Spectral Data of the Products. S-Phenyl
4-Methoxybenzothioate (3a).7b The title compound was prepared
according to the general procedure and purified by column
S-(4-(tert-Butyl) Phenyl) 4-Methoxybenzothioate (3f). The title
compound was prepared according to the general procedure and
F
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purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (40:1) to afford a colorless oil in 96%
yield (57.6 mg). 1H NMR (400 MHz, CDCl3): δ 8.02 (d, J = 8.0 Hz,
2H), 7.49−7.43 (m, 4H), 6.96 (d, J = 8.0 Hz, 2H), 3.87 (s, 3H), 1.36
(s, 9H). 13C{1H} NMR (100 MHz, CDCl3): δ 188.9, 163.9, 152.5,
134.8, 129.6, 129.5, 126.3, 124.1, 113.8, 55.5, 34.7, 31.2. HRMS (EI)
m/z: [M + H+] calcd for C18H21O2S+: 301.1257, found: 301.1259.
S-(3-Methoxyphenyl) 4-Methoxybenzothioate (3g).7b The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (5:1) to afford a colorless solid in 95%
CDCl3): δ 190.4, 163.5, 130.4, 129.2, 113.6, 55.4, 42.4, 33.3, 26.0,
25.6.
S-Allyl 4-Methoxybenzothioate (3n).26 The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
1
acetate (40:1) to afford a colorless oil in 56% yield (23.3 mg). H
NMR (400 MHz, CDCl3): δ 7.94 (d, J = 8.8 Hz, 2H), 6.91 (d, J = 8.8
Hz, 2H), 5.94−5.84 (m, 1H), 5.33−5.28 (m, 1H), 5.14−5.12 (m,
1H), 3.85 (s, 3H), 3.71 (d, J = 6.8 Hz, 2H). 13C{1H} NMR (100
MHz, CDCl3): δ 189.7, 163.8, 133.4, 129.8, 129.4, 117.8, 113.8, 55.5,
31.7.
S-(2-Hydroxyethyl) 4-Methoxybenzothioate (3o).5e The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (2:1) to afford a colorless oil in 78%
yield (33.1 mg). 1H NMR (400 MHz, CDCl3): δ 7.94 (d, J = 8.8 Hz,
2H), 6.91 (d, J = 9.2 Hz, 2H), 3.86−3.83 (m, 5H), 3.26 (t, J = 6.0 Hz,
2H), 2.26 (br s, 1H). 13C{1H} NMR (100 MHz, CDCl3): δ 190.6,
163.9, 129.6, 129.5, 113.8, 62.0, 55.5, 31.8.
1
yield (52.1 mg); mp 138−139 °C. H NMR (400 MHz, CDCl3): δ
8.00 (d, J = 8.0 Hz, 2H), 7.42 (d, J = 8.0 Hz, 2H), 6.98 (d, J = 8.0 Hz,
2H), 6.95 (d, J = 8.4 Hz, 2H), 3.86 (s, 3H), 3.84 (s, 3H). 13C{1H}
NMR (100 MHz, CDCl3): δ 189.4, 163.8, 160.6, 136.6, 129.6, 129.4,
118.1, 114.8, 113.8, 55.4, 55.3.
S-(4-(Methylthio)phenyl) 4-Methoxybenzothioate (3h). The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (20:1) to afford a yellow oil in 83%
yield (48.1 mg). 1H NMR (400 MHz, CDCl3): δ 7.99 (d, J = 8.4 Hz,
2H), 7.39 (d, J = 7.6 Hz, 2H), 7.29 (d, J = 8.0 Hz, 2H), 6.95 (d, J =
8.4 Hz, 2H), 3.86 (s, 3H), 2.50 (s, 3H). 13C{1H} NMR (100 MHz,
CDCl3): δ 188.7, 163.9, 140.9, 135.4, 129.6, 129.2, 126.5, 123.3,
S-Benzyl 4-Methoxybenzothioate (3p).26 The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a white solid in 90% yield (46.4 mg); mp 50−
51 °C. 1H NMR (500 MHz, CDCl3): δ 7.94 (d, J = 9.0 Hz, 2H), 7.37
(d, J = 7.5 Hz, 2H), 7.31 (t, J = 7.5 Hz, 2H), 7.26−7.23 (m, 1H), 6.90
(d, J = 9.0 Hz, 2H), 4.30 (s, 2H), 3.84 (s, 3H). 13C{1H} NMR (125
MHz, CDCl3): δ 189.7, 163.7, 137.7, 129.5, 129.4, 128.9, 128.6,
127.2, 113.7, 55.4, 33.1.
S-(Furan-2-ylmethyl) 4-Methoxybenzothioate (3q). The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (40:1) to afford a colorless oil in 78%
yield (38.7 mg). 1H NMR (400 MHz, CDCl3): δ 7.94 (d, J = 9.2 Hz,
2H), 7.34−7.33 (m, 1H), 6.91 (d, J = 9.2 Hz, 2H), 6.31−6.28 (m,
2H), 4.33 (s, 2H), 3.84 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3):
δ 189.1, 163.9, 150.7, 142.1, 129.5, 113.8, 110.6, 107.9, 55.4, 25.6.
HRMS (EI) m/z: [M + H+] calcd for C13H13O3S+: 249.0580, found:
249.0582.
+
113.8, 55.5, 15.3. HRMS (EI) m/z: [M + H+] calcd for C15H15O2S2 :
291.0508, found: 291.0512.
S-(2-Methylfuran-3-yl) 4-Methoxybenzothioate (3i). The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (40:1) to afford a white solid in 55%
yield (27.3 mg). mp 89−90 °C. 1H NMR (500 MHz, CDCl3): δ 8.00
(d, J = 8.5 Hz, 2H), 7.41−7.40 (m, 1H), 6.95 (d, J = 9.0 Hz, 2H),
6.40−6.39 (m, 1H), 3.87 (s, 3H), 2.30 (s, 3H). 13C{1H} NMR (125
MHz, CDCl3): δ 188.0, 163.9, 156.6, 141.1, 129.7, 129.1, 115.2,
113.8, 103.5, 55.5, 11.9. HRMS (EI) m/z: [M + H+] calcd for
C13H13O3S+: 249.0580, found: 249.0585.
S-Propyl 4-Methoxybenzothioate (3j).25 The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (80:1) to afford a colorless oil in 79% yield (33.2 mg); mp
89−90 °C. 1H NMR (400 MHz, CDCl3): δ 7.94 (d, J = 8.8 Hz, 2H),
6.90 (d, J = 9.2 Hz, 2H), 3.84 (s, 3H), 3.02 (t, J = 7.2 Hz, 2H), 1.71−
1.66 (m, 2H), 1.02 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (100 MHz,
CDCl3): δ 190.5, 163.6, 130.1, 129.3, 113.6, 55.4, 30.7, 23.1, 13.4.
S-(n-Butyl) 4-Methoxybenzothioate (3k).6g The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a colorless oil in 83% yield (37.2
S-Phenyl Benzothioate (3r).7b The title compound was prepared
according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a colorless solid in 81% yield (34.7 mg); mp
56−57 °C. 1H NMR (400 MHz, CDCl3): δ 8.03 (d, J = 8.0 Hz, 2H),
7.63−7.59 (m, 1H), 7.54−7.45 (m, 7H). 13C{1H} NMR (100 MHz,
CDCl3): δ 190.1, 136.6, 135.1, 133.6, 129.5, 129.2, 129.0, 128.7,
127.5.
S-(n-Butyl)benzothioate (3s).6g The title compound was prepared
according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (100:1) to afford a white solid in 65% yield (25.2 mg); mp
1
mg). H NMR (400 MHz, CDCl3): δ 7.93 (d, J = 8.8 Hz, 2H), 6.90
(d, J = 9.2 Hz, 2H), 3.84 (s, 3H), 3.04 (t, J = 7.2 Hz, 2H), 1.67−1.60
(m, 2H), 1.49−1.39 (m, 2H), 0.93 (t, J = 7.6 Hz, 3H). 13C{1H} NMR
(100 MHz, CDCl3): δ 190.6, 163.6, 130.1, 129.2, 113.6, 55.4, 31.7,
28.54, 22.0, 13.6.
1
119−120 °C. H NMR (400 MHz, CDCl3): δ 7.96 (d, J = 8.4 Hz,
2H), 7.55 (t, J = 7.6 Hz, 1H), 7.44 (t, J = 8.0 Hz, 2H), 3.08 (t, J = 7.6
Hz, 2H), 1.70−1.62 (m, 2H), 1.50−1.41 (m, 2H), 0.95 (t, J = 7.2 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3): δ 192.1, 137.3, 133.1, 128.5,
127.1, 31.61, 28.7, 22.0, 13.6.
S-Isopropyl 4-Methoxybenzothioate (3l). The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a yellow oil in 60% yield (25.2 mg). 1H NMR
(400 MHz, CDCl3): δ 7.92 (d, J = 9.2 Hz, 2H), 6.90 (d, J = 8.8 Hz,
2H), 3.85 (s, 3H), 3.83−3.77 (m, 1H), 1.39 (d, J = 7.2 Hz, 6H).
13C{1H} NMR (100 MHz, CDCl3): δ 190.7, 163.6, 130.3, 129.2,
113.7, 55.5, 34.7, 23.2. HRMS (EI) m/z: [M + H+] calcd for
C11H15O2S+: 211.0750, found: 211.0756.
S-Phenyl 4-Methylbenzothioate (3t).7b The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a colorless solid in 89% yield (40.6 mg); mp
94−95 °C. 1H NMR (400 MHz, CDCl3): δ 7.91 (d, J = 8.0 Hz, 2H),
7.51−7.42 (m, 5H), 7.25 (d, J = 7.6 Hz, 2H), 2.39 (s, 3H). 13C{1H}
NMR (100 MHz, CDCl3): δ 189.6, 144.5, 135.1, 134.0, 129.3, 129.1,
127.5, 21.6.
S-Cyclohexyl 4-Methoxybenzothioate (3m).5e The title com-
pound was prepared according to the general procedure and purified
by column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a yellow oil in 54% yield (27 mg).
1H NMR (400 MHz, CDCl3): δ 7.92 (d, J = 9.2 Hz, 2H), 6.90 (d, J =
8.8 Hz, 2H), 3.85 (s, 3H), 3.72−3.65 (m, 1H), 2.03−1.99 (m, 2H),
1.77−1.72 (m, 2H), 1.63−1.38 (m, 6H). 13C{1H} NMR (100 MHz,
S-Phenyl 3-Methylbenzothioate (3u).7b The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
1
acetate (40:1) to afford a colorless oil in 90% yield (41.0 mg). H
NMR (400 MHz, CDCl3): δ 7.87−7.85 (m, 2H), 7.55−7.36 (m, 7H),
2.44 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 190.2, 138.6,
136.6, 135.0, 134.4, 129.4, 129.2, 128.6, 127.9, 127.4, 124.6, 21.3.
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S-Phenyl 2-Methylbenzothioate (3v).7b The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a colorless solid in 87% yield (39.7 mg); mp
45−46 °C. 1H NMR (400 MHz, CDCl3): δ 7.95 (dd, J = 7.6, 0.8 Hz,
1H), 7.55−7.41 (m, 6H), 7.33−7.26 (m, 2H), 2.51 (s, 3H). 13C{1H}
NMR (100 MHz, CDCl3): δ 192.1, 137.4, 136.7, 134.9, 131.9, 131.7,
129.4, 129.2, 128.6, 128.2, 125.8, 20.7.
mg). 1H NMR (400 MHz, CDCl3): δ 10.76 (s, 1H), 8.00 (dd, J = 8.0,
1.2 Hz, 1H), 7.55−7.49 (m, 6H), 7.01−6.95 (m, 2H). 13C NMR (100
MHz, CDCl3): δ 195.8, 159.7, 136.3, 135.5, 130.0, 129.4, 128.9,
125.9, 119.5, 119.4, 118.3.
S-Phenyl [1,1′-Biphenyl]-4-carbothioate (3zf).29 The title com-
pound was prepared according to the general procedure and purified
by column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a colorless oil in 57% yield (33.1
mg). 1H NMR (400 MHz, CDCl3): δ 8.11 (d, J = 8.0 Hz, 2H), 7.72−
7.64 (m, 4H), 7.55−7.40 (m, 8H). 13C{1H} NMR (100 MHz,
CDCl3): δ 189.7, 146.4, 139.7, 135.3, 135.1, 129.5, 129.2, 128.9,
128.3, 128.0, 127.4, 127.3.
S-Phenyl 4-(tert-Butyl) Benzothioate (3w).6g The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a colorless oil in 92% yield (49.7
mg). 1H NMR (400 MHz, CDCl3): δ 8.00 (d, J = 8.8 Hz, 2H), 7.56−
7.43 (m, 7H), 1.38 (s, 9H). 13C{1H} NMR (100 MHz, CDCl3): δ
189.6, 157.5, 135.1, 133.9, 129.3, 129.1, 127.6, 127.4, 125.6, 35.2,
31.0.
S-Phenyl Benzo[d][1,3]dioxole-5-carbothioate (3zg). The title
compound was prepared according to the general procedure and
purified by column chromatography on silica gel and eluted with
petroleum ether/ethyl acetate (20:1) to afford a white solid in 80%
S-Phenyl 4-(Benzyloxy) Benzothioate (3x).27 The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (20:1) to afford a colorless solid in 84% yield
(53.8 mg); mp 160−161 °C. 1H NMR (400 MHz, CDCl3): δ 8.02 (d,
J = 8.8 Hz, 2H), 7.53−7.34 (m, 10H), 7.04 (d, J = 8.8 Hz, 2H), 5.15
(s, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ 188.5, 163.1, 136.0,
135.2, 129.7, 129.6, 129.3, 129.1, 128.7, 128.3, 127.6, 127.5, 114.8,
70.2.
1
yield (41.3 mg); mp 84−85 °C. H NMR (400 MHz, CDCl3): δ
7.70−7.68 (m, 1H), 7.52−7.43 (m, 6H), 6.88 (d, J = 8.4 Hz, 1H),
6.05 (s, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ 188.3, 152.2,
148.1, 135.1, 131.0, 129.4, 129.1, 127.5, 123.6, 108.1, 107.4, 101.9.
HRMS (EI) m/z: [M + H+] calcd for C14H11O3S+: 259.0423, found:
259.0428.
S-Phenyl Thiophene-2-carbothioate (3zh).7b The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a yellow solid in 63% yield (27.7
S-Phenyl 4-Fluorobenzothioate (3y).7a The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a colorless solid in 82% yield (38.1 mg); mp
1
mg); mp 59−60 °C. H NMR (400 MHz, CDCl3): δ 7.92−7.90 (m,
1H), 7.67−7.65 (m, 1H), 7.54−7.44 (m, 5H), 7.17−7.14 (m, 1H).
13C{1H} NMR (100 MHz, CDCl3): δ 182.0, 141.4, 135.0, 133.2,
131.6, 129.6, 129.2, 127.9, 126.9.
1
59−60 °C. H NMR (400 MHz, CDCl3): δ 8.07−8.04 (m, 2H),
7.50−7.46 (m, 5H), 7.16 (t, J = 8.0 Hz, 2H). 13C{1H} NMR (100
MHz, CDCl3): δ 188.6, 166.0 (d, JC‑F = 255.4 Hz), 135.1, 132.9 (d,
O-Ethyl-S-phenyl Carbonothioate (3zj).30 The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a yellow oil in 40% yield (14.6
mg). 1H NMR (400 MHz, CDCl3): δ 7.56−7.52 (m, 2H), 7.45−7.37
(m, 3H), 4.30 (q, J = 7.2 Hz, 2H), 1.33 (t, J = 6.8 Hz, 3H). 13C{1H}
NMR (100 MHz, CDCl3): δ 169.5, 134.8, 129.4, 129.1, 127.8, 63.9,
14.2.
JC‑F = 3.2 Hz), 130.0 (d, JC‑F = 9.4 Hz), 129.6, 129.3, 127.0, 115.9 (d,
JC‑F = 22.2 Hz). 19F NMR (376 MHz, CDCl3): δ −104.2 (s, 1F).
S-Phenyl 4-Chlorobenzothioate (3za).7b The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (40:1) to afford a colorless solid in 63% yield (31.2 mg); mp
81−82 °C. 1H NMR (400 MHz, CDCl3): δ 7.97 (d, J = 8.4 Hz, 2H),
7.52−7.45 (m, 7H). 13C{1H} NMR (100 MHz, CDCl3): δ 189.0,
140.0, 135.0, 134.9, 129.7, 129.3, 129.0, 128.8, 126.9.
O-Methyl-S-phenyl Carbonothioate (3zk).30 The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a colorless oil in 35% yield (11.8
mg). 1H NMR (400 MHz, CDCl3): δ 7.56−7.51 (m, 2H), 7.44−7.39
(m, 3H), 3.84 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 170.2,
134.8, 129.6, 129.2, 127.6, 54.5.
S-Phenyl 3,5-Dimethoxybenzothioate (3zb). The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (20:1) to afford a colorless oil in 70% yield (38.4
mg). 1H NMR (400 MHz, CDCl3): δ 7.53−7.45 (m, 5H), 7.17−7.15
(m, 2H), 6.70−6.68 (m, 1H), 3.84 (s, 6H). 13C{1H} NMR (100
MHz, CDCl3): δ 189.9, 160.9, 138.5, 134.9, 129.5, 129.2, 127.4,
105.9, 105.1, 55.6. HRMS (EI) m/z: [M + H+] calcd for C15H15O3S+:
275.0736, found: 275.0739.
S-Phenyl Ethanethioate (3zl).31 The title compound was prepared
according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
1
acetate (40:1) to afford a yellow oil in 21% yield (6.4 mg). H NMR
(400 MHz, CDCl3): δ 7.44−7.41 (m, 5H), 2.42 (s, 3H). 13C{1H}
NMR (100 MHz, CDCl3): δ 193.9, 134.4, 129.4, 129.2, 127.9, 30.2.
3-((4-Methoxyphenyl)thio)-2-methylfuran (5). The title com-
pound was prepared according to the general procedure and purified
by column chromatography on silica gel and eluted with petroleum
S-Phenyl 4-Aminobenzothioate (3zc).7a The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether/ethyl
acetate (5:1) to afford a colorless solid in 50% yield (22.9 mg); mp
1
1
157−158 °C;. H NMR (400 MHz, CDCl3): δ 7.87 (d, J = 8.0 Hz,
ether to afford a yellow oil in 96% yield (211.2 mg). H NMR (400
2H), 7.51−7.42 (m, 5H), 6.64 (d, J = 8.0 Hz, 2H), 4.16 (br s, 2H).
13C{1H} NMR (100 MHz, CDCl3): δ 188.0, 151.7, 135.2, 129.9,
129.1, 129.0, 128.0, 126.6, 113.8.
MHz, CDCl3): δ 7.32−7.30 (m, 1H), 7.13 (d, J = 8.8 Hz, 2H), 6.80
(d, J = 9.2 Hz, 2H), 6.34−6.32 (m, 1H), 3.76 (s, 3H), 2.36 (s, 3H).
13C{1H} NMR (100 MHz, CDCl3): δ 158.2, 155.6, 140.9, 129.3,
128.2, 115.1, 114.6, 109.7, 55.3, 11.8. HRMS (EI) m/z: [M + H+]
calcd for C12H13O2S+: 221.0631, found: 221.0636.
S-Phenyl 4-Hydroxybenzothioate (3zd).7a The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (2:1) to afford colorless crystals in 41% yield (18.9
5-(Phenylthio)benzo[d][1,3]dioxole (6).32 The title compound was
prepared according to the general procedure and purified by column
chromatography on silica gel and eluted with petroleum ether to
1
mg); mp 173−174 °C. H NMR (400 MHz, CDCl3): δ 7.94 (d, J =
1
8.8 Hz, 2H), 7.53−7.43 (m, 5H), 6.84 (d, J = 8.4 Hz, 2H), 6.27 (br s,
1H). 13C{1H} NMR (100 MHz, CDCl3): δ 189.6, 160.8, 135.2, 131.9,
130.0, 129.5, 129.2, 127.4, 115.5.
afford a colorless oil in 78% yield (179.4 mg). H NMR (400 MHz,
CDCl3): δ 7.30−7.17 (m, 5H), 7.03−7.01 (m, 1H), 6.94−6.92 (m,
1H), 6.81 (d, J = 8.0 Hz, 1H), 6.00 (s, 2H). 13C{1H} NMR (100
MHz, CDCl3): δ 148.3, 147.9, 137.9, 128.9, 128.9, 127.3, 126.3,
126.2, 113.5, 108.9, 101.4.
S-Phenyl 2-Hydroxybenzothioate (3ze).28 The title compound
was prepared according to the general procedure and purified by
column chromatography on silica gel and eluted with petroleum
ether/ethyl acetate (40:1) to afford a yellow oil in 39% yield (17.9
Cu(OAc)2·bipy (7). The title compound was prepared according to
the known methods.24 2,2′-Bipyridine (5.44 mmol, 849.6 mg), DMF
H
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(20 mL), Cu(OAc)2·H2O (8.16 mmol, 1.63 g), DMF (40 mL), blue
powder. Anal. calcd for C14H14N2O4Cu: C, 48.48; H, 4.36; N, 8.08.
Found: C, 48.58; H, 4.42; N, 8.17. IR (neat, cm−1): 2924, 1580, 1400,
1330,1248, 1169, 1023, 919, 769, 673.
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p-Me-PhSCu (8).23 The title compound was prepared according to
the known methods.23 Conc. aq. NH3 (6.25 mL), H2O (25 mL),
CuSO4·5H2O (6.25 mmol, 1.56 g), NH2OH·HCl (14 mmol, 0.97 g),
p-TolylSH (6.45 mmol, 0.8 g), EtOH (40 mL). Yellow solid (1.10 g,
80%). 1H NMR (400 MHz, CDCl3): δ 7.37 (d, J = 7.6 Hz, 2H), 7.09
(d, J = 8.0 Hz, 2H), 2.31 (s, 3H).
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.joc.0c02328.
■
sı
GC−MS analysis of the control experiments and copies
of 1 H, 19F, and 13C NMR spectra for all products (PDF)
AUTHOR INFORMATION
Corresponding Author
Jianyu Dong − Department of Educational Science, Hunan
First Normal University, Changsha 410205, China; College
of Chemistry and Chemical Engineering, Hunan University,
Changsha 410082, China; orcid.org/0000-0003-2161-
1372; Email: djyustc@hotmail.com
■
Authors
Shimin Xie − Department of Educational Science, Hunan First
Normal University, Changsha 410205, China; College of
Chemistry and Chemical Engineering, Hunan University,
Changsha 410082, China; Key Laboratory for Green
Organic Synthesis and Application of Hunan Province,
College of Chemistry, Xiangtan University, Xiangtan 411105,
China
Lebin Su − College of Chemistry and Chemical Engineering,
Hunan University, Changsha 410082, China
Min Mo − Department of Educational Science, Hunan First
Normal University, Changsha 410205, China
Wang Zhou − Key Laboratory for Green Organic Synthesis
and Application of Hunan Province, College of Chemistry,
Xiangtan University, Xiangtan 411105, China; orcid.org/
0000-0001-8629-086X
Yongbo Zhou − College of Chemistry and Chemical
Engineering, Hunan University, Changsha 410082, China;
orcid.org/0000-0002-3540-8618
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.joc.0c02328
Author Contributions
(4) (a) Ali, W.; Guin, S.; Rout, S. K.; Gogoi, A.; Patel, B. K.
Thioesterification of Alkylbenzenes with Thiols via Copper- Catalyzed
Cross-Dehydrogenative Coupling without a Directing Group. Adv.
Synth. Catal. 2014, 356, 3099. (b) Bao, W.-H.; Wu, C.; Wang, J.-T.;
Xia, W.; Chen, P.; Tang, Z.; Xu, X.; He, W.-M. Molecular iodine-
mediated synthesis of thiocarbamates from thiols, isocyanides and
water under metal-free conditions. Org. Biomol. Chem. 2018, 16, 8403.
(c) Hirschbeck, V.; Gehrtz, P. H.; Fleischer, I. Regioselective
Thiocarbonylation of Vinyl Arenes. J. Am. Chem. Soc. 2016, 138,
16794. (d) Hirschbeck, V.; Gehrtz, P. H.; Fleischer, I. Metal-
Catalyzed Synthesis and Use of Thioesters: Recent Developments.
Chem. − Eur. J. 2018, 24, 7092. (e) Kazemi, M.; Shiri, L. Thioesters
synthesis: recent adventures in the esterification of thiols. J. Sulfur
Chem. 2015, 36, 613. (f) Ranu, B. C.; Jana, R. Ionic Liquid as Catalyst
and Reaction Medium: A Simple, Convenient and Green Procedure
for the Synthesis of Thioethers, Thioesters and Dithianes using an
∥S.X. and L.S. contributed equally to this work.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support from the NSF of China (grant nos.
21706058, 21878072, and 21573065), the Hunan Provincial
Natural Science Foundation of China (grant no. 2020JJ2011),
and the China Postdoctoral Science Foundation (grant no.
2019M662774) is much appreciated.
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