Iron-catalyzed synthesis of thioesters from thiols and aldehydes in water

Article abstract of DOI:10.1021/jo500574p

The preparation of thioesters through the iron-catalyzed coupling reaction of thiols with aldehydes is described. The reactions were carried out by using tert-butyl hydroperoxide (TBHP) as an oxidant and water as a solvent in most cases. This system is co

Full text of DOI:10.1021/jo500574p

Article
pubs.acs.org/joc
Iron-Catalyzed Synthesis of Thioesters from Thiols and Aldehydes in
Water
Yu-Ting Huang, Shao-Yi Lu, Chih-Lun Yi, and Chin-Fa Lee*
Department of Chemistry, National Chung Hsing University, Taichung, Taiwan 402, Republic of China
S
* Supporting Information
ABSTRACT: The preparation of thioesters through the iron-catalyzed
coupling reaction of thiols with aldehydes is described. The reactions were
carried out by using tert-butyl hydroperoxide (TBHP) as an oxidant and water
as a solvent in most cases. This system is compatible with a variety of
functional groups.
1−11) suggested that FeBr2 was the best catalyst, providing the
product in 82% yield (Table 1, entry 9). A comparative yield
was obtained when extra pure FeBr2 was employed as a catalyst,
and this result eliminated the contribution from other
transition-metal contaminants in FeBr2 (Table 1, entry 12).
Screening oxidants (Table 1, entries 13−18) indicated that
TBHP was superior to DTBP, AcOOH, BPO, H2O2, K2S2O8,
and TBPB. An 85% yield of product was afforded when the
reaction was carried out at 110 °C (Table 1, entry 19). Shorter
reaction times reduced the yield of the product (Table 1, entry
20). Interestingly, it was observed that a higher amount of
TBHP (Table 1, entry 21) and lower FeBr2 loadings (Table 1,
entry 22) diminished the yield of the product. Control
experiments showed that 28% yield was obtained in the
absence of catalyst (Table 1, entry 23).
With the optimized reaction conditions in hand, we explored
the scope of the substrates possible with this novel system. The
results are summarized in Table 2. A variety of alkyl thiols were
coupled with aldehydes. Aryl aldehydes containing electron-
donating or electron-withdrawing groups also reacted smoothly
with alkyl thiols, giving thioesters in moderate to excellent
yields. Functional groups including chloro (Table 2, entries 1
and 13), bromo (Table 2, entries 5 and 16), trifluoromethyl
(Table 2, entries 6 and 17), nitrile (Table 2, entry 7), and ester
(Table 2, entry 20) are all tolerated under the reaction
conditions. Sterically demanding substrates slightly reduce the
product yield (Table 2, entry 3). Alkyl aldehydes were also
coupled with thiols to give the corresponding thioesters along
with disulfides as the byproducts (Table 2, entries 9−11). In
general, the product yields for the coupling of alkyl aldehydes
with thiols are lower than those of coupling between aryl
aldehydes and thiols.
INTRODUCTION
■
Thioesters are important building blocks for organic synthesis1
and chemical biology.2 Recently, the direct coupling of
aldehydes with sulfur surrogates has become an atom-economic
strategy for the preparation of thioesters.3−8 It is shown that
thioesters can be prepared via photoirradiation of thiols with
aldehydes. However, the scope of the substrate is limited to
benzaldehyde, and it is not applicable to substituted aryl
aldehydes. Moreover, recquisite dilute reaction conditions make
photoirradiation difficult to scale up.4 Takemote et al. described
the carbene-catalyzed coupling reaction of thiols with
aldehydes. Some synthetic limitations are presented in this
system: (1) carbenes used in this system are expensive; (2)
electron-rich carbenes are necessary for alkyl aldehydes.5 Kita
and co-workers reported the C−S bond formation between
pentafluorophenyl disulfide and aldehydes; however, other
diaryl and dialkyl disulfides are not suitable as the coupling
partners in this system.6 Bandgar and co-workers demonstrated
that a combination of Dess−Martin periodinane and NaN3 is
able to promote the synthesis of thioesters from aryl thiols and
aldehydes. However, 6 equiv of Dess−Martin periodinane and
6 equiv of NaN3 are required. Moreover, the substrate is limited
to aryl thiols.7 Recently, we reported the copper-catalyzed
coupling of aldehydes with thiols in water by using TBHP as an
oxidant.8a However, owing to the high binding affinity between
copper and heteroatoms, a low product yield was obtained
when the reaction was carried out by using 2-thiophenecarbox-
aldehyde and 4-methylbenzenethiol as the coupling partners
(31% yield).8a Moreover, only trace amounts of products were
detected when pyridine- or furan-containing substrates were
employed. Alternatively, iron is cheap and nontoxic, and iron
salts have been utilized for many useful reactions.9,10 As part of
our ongoing progress toward C−S bond coupling reac-
tions,10f,g,11 we report herein the iron-catalyzed coupling
reaction of thiols with aldehydes.
On the basis of promising results for alkyl thiols, we then
turned our attention to aryl thiols. As shown in Table 3, the
system once again shows good functional group compatibility.
Chloro (Table 3, entries 1, 3, 5, 6, 9, 13, 15−17, and 20),
trifluoromethyl (Table 3, entries 2, 4, 7, and 8), nitrile (Table 3,
RESULTS AND DISCUSSION
■
We initially examined the coupling reaction of benzaldehyde
with 1-dodecanethiol in the presence of iron salt and oxidant in
water at 100 °C for 1 h. The study of iron salts (Table 1, entries
Received: March 11, 2014
Published: April 21, 2014
© 2014 American Chemical Society
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Table 1. Optimization of Iron-Catalyzed Coupling of
1‑Dodecanethiol with Benzaldehyde
CONCLUSION
■
a
In summary, we have developed a generally applicable iron-
catalyzed coupling reaction of aldehydes with thiols in water.
Functional groups including chloro, bromo, trifluoromethyl,
and nitrile and heteroaryls including thiophene, furan, and
pyridine are all tolerated under the reaction conditions.
entry
“Fe” (concn, mol %)
oxidant
yield (%)
EXPERIMENTAL SECTION
1
2
FeCl2 (2.5)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.0)
DTBP (1.0)
AcOOH (1.0)
BPO (1.0)
66
53
52
32
25
78
70
69
82
41
79
78
−
■
General Information. All reagents and solvents were purchased
from commercial suppliers and used without additional purification.
The acetonitrile used for the reactions was dried by distillation over
CaH2 and stored in the presence of activated molecular sieves. All
reactions were carried out under an inert atmosphere. Flash
chromatography was performed on silica gel 60 (230−400 mesh).
Analysis. NMR spectra were recorded using CDCl3 as the solvent.
Chemical shifts are reported in parts per million and referenced to the
residual solvent resonance. Coupling constants (J) are reported in
hertz. 13C{1H} NMR spectra were recorded on a 100 MHz
spectrometer using broad-band proton decoupling. Standard abbrevia-
tions indicating multiplicity are used as follows: br s (broad singlet), s
(singlet), d (doublet), t (triplet), dd (doublet of doublets), q (quartet),
m (multiplet). Melting points (mp’s) were determined using an
apparatus and are reported uncorrected. High-resolution mass
spectrometry (HRMS) was performed on an electron ionization
time-of-flight (EI-TOF) mass spectrometer.
General Procedure for Table 1. A Schlenk tube equipped with a
magnetic stir bar was charged with iron salt (0.0125 mmol) in a
nitrogen-filled glovebox. The Schlenk tube was then covered with a
rubber septum and removed from the glovebox. Under a nitrogen
atmosphere, 1-dodecanethiol (0.125 mL, 0.5 mmol), benzaldehyde
(0.26 mL, 2.5 mmol), oxidant (1.0 mmol), and solvent (1.5 mL) were
added via syringe, and the Schlenk tube was connected to a nitrogen-
filled balloon and heated at 100 °C in an oil bath. After being stirred at
this temperature for 1 h, the heterogeneous mixture was cooled to
room temperature and diluted with ethyl acetate (20 mL). The
resulting solution was directly filtered through a pad of silica gel, then
washed with ethyl acetate (20 mL), and concentrated to give the crude
material, which was then purified by column chromatography (SiO2,
hexane) to yield 3a.
Representative Example for Table 1. S-Dodecyl Benzothioate
(3a) (Entry 19).8a The general procedure for Table 1 was followed
using FeBr2 (2.8 mg, 0.0125 mmol), benzaldehyde (0.26 mL, 2.5
mmol), 1-dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL,
1.0 mmol) in H2O (1.5 mL). The product was then purified by
column chromatography (SiO2, hexane) to provide 3a as a yellow oil
(131 mg, 85% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.8
Hz, 3 H), 1.26−1.44 (m, 18 H), 1.63−1.69 (m, 2H), 3.07 (t, J = 7.2
Hz, 2 H), 7.44 (t, J = 7.6 Hz, 2 H), 7.55 (t, J = 7.4 Hz, 1 H), 7.97 (d, J
= 8.0 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 14.1, 22.7, 28.9, 29.0,
29.1, 29.3, 29.5, 29.5, 29.5, 29.6, 29.6, 31.9, 127.1, 128.5, 133.1, 137.2,
192.1.
General Procedure for Table 2. A Schlenk tube equipped with a
magnetic stir bar was charged with FeBr2 (2.8 mg, 0.0125 mmol) in a
nitrogen-filled glovebox. The Schlenk tube was then covered with a
rubber septum and removed from the glovebox. Under a nitrogen
atmosphere, thiol (0.5 mmol), aldehyde (2.5 mmol), TBHP (0.14 mL,
1.0 mmol), and H2O (1.5 mL) were added via syringe, and the
Schlenk tube was connected to a nitrogen-filled balloon and heated at
110 °C in an oil bath. After being stirred at this temperature for 1 h,
the heterogeneous mixture was cooled to room temperature and
diluted with ethyl acetate (20 mL). The resulting solution was directly
filtered through a pad of silica gel, then washed with ethyl acetate (20
mL), and concentrated to give the crude material, which was then
purified by column chromatography (SiO2, hexane) to yield 3.
S-Dodecyl 4-Chlorobenzothioate (3b) (Table 2, Entry 1).8a The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-chlorobenzaldehyde (359 mg, 2.5 mmol), 1-
dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
Fe(OAc)2 (2.5)
Fe2O3 (2.5)
Fe2(CO)9 (2.5)
Fe3(CO)12 (2.5)
Fe(acac)3 (2.5)
Fe(NO3)3·9H2O (2.5)
FeCp2 (2.5)
FeBr2 (2.5)
3
4
5
6
7
8
9
10
11
FeBr3 (2.5)
FeCl3 (2.5)
b
12
FeBr2 (2.5)
13
14
15
16
17
18
FeBr2 (2.5)
FeBr2 (2.5)
trace
12
−
FeBr2 (2.5)
FeBr2 (2.5)
H2O2 (1.0)
K2S2O8 (1.0)
TBPB (1.0)
TBHP (1.0)
TBHP (1.0)
TBHP (1.5)
TBHP (1.0)
TBHP (1.0)
FeBr2 (2.5)
−
FeBr2 (2.5)
58
85
54
62
75
28
c
19
FeBr2 (2.5)
c,d
20
21
22
23
FeBr2 (2.5)
ce
,
FeBr2 (2.5)
c
c
FeBr2 (1.25)
a
Reaction conditions: iron source (0.0125 mmol, 2.5 mol %), oxidant
(1.0 mmol), 1-dodecanethiol (0.125 mL, 0.5 mmol), and benzalde-
hyde (0.26 mL, 2.5 mmol) under a nitrogen atmosphere in H2O (1.5
mL) for 1 h. FeBr2 (99.999%). Temperature 110 °C. Time 30 min.
A 1.5 mmol portion of TBHP (70% in H2O) was used. TBHP = tert-
butyl hydroperoxide. DTBP = di-tert-butyl peroxide. AcOOH =
peracetic acid. BPO = benzoyl peroxide. H2O2 = hydrogen peroxide.
K2S2O8 = potassium persulfate. TBPB = tert-butyl perbenzoate.
b
c
d
e
entry 6), and bromo (Table 3, entries 8, 12, 14, 18, 19, and 21)
are all tolerated under the reaction conditions. Remarkably,
thiophene-, furan-, and pyridine-containing aldehydes could not
serve as good coupling partners with thiols through copper
catalysis;8 however, such heterocyclo-containing aldehydes
were reacted with thiols to give the corresponding thioesters
in moderate to good yields (Table 3, entries 9−11, 16, and 17).
Alkyl aldehydes could also be used as the coupling partners
with thiols to provide the corresponding thioesters in moderate
to excellent yields (Table 3, entries 14, 15, and 18−21).
A plausible mechanism for iron-catalyzed coupling of an
aldehyde with a thiol is shown in Scheme 1. Iron(IIII) complex
A is formed when FeBr2 is reacted with TBHP, and t-BuOO•
radical is generated at the same time.12 A hydrogen atom is
then abstracted from the aldehyde to give an acyl radical.
Complex A further reacts with the thiol to give an iron(III)
thiolate complex, B. This complex traps the acyl radical to
provide a thioester, along with the generation of iron complex
C.13 FeBr2 is regenerated when complex C is reacted with HBr
from the first step of the catalytic cycle. A radical coupling of an
acyl radical with a thiyl radical is also possible in this reaction.6c
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a
Table 2. Substrate Scope of Aldehydes and Alkyl Thiols
a
Reaction conditions unless otherwise stated: FeBr2 (0.0125 mmol, 2.5 mol %), TBHP (1.0 mmol, 70% in water), thiol (0.5 mmol), and aldehyde
b
(2.5 mmol) under a nitrogen atmosphere in H2O (1.5 mL) for 1 h. In acetonitrile (1.5 mL) at 90 °C for 1 h.
chromatography (SiO2, hexane) to provide 3b as a yellow oil (140 mg,
82% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 7.0 Hz, 3 H),
1.26−1.43 (m, 18 H), 1.62−1.68 (m, 2 H), 3.06 (t, J = 7.4 Hz, 2 H),
7.40 (dd, J = 1.6, 6.4 Hz, 2 H), 7.90 (dd, J = 2.0, 6.8 Hz, 2 H). 13C
NMR (100 MHz, CDCl3): δ 14.1, 22.7, 28.9, 29.1, 29.1, 29.3, 29.5,
29.6, 29.6, 29.6, 31.9, 128.5, 128.8, 135.5, 139.5, 190.8.
chromatography (SiO2, hexane) to provide 3d as a colorless oil (89
mg, 55% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.2 Hz, 3
H), 1.26−1.44 (m, 18 H), 1.63−1.68 (m, 2 H), 2.48 (s, 3 H), 3.03 (t, J
= 7.2 Hz, 2 H), 7.21−7.24 (m, 2 H), 7.36 (t, J = 7.6 Hz, 1 H), 7.76 (d,
J = 7.6 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 14.1, 20.5, 22.7,
28.9, 29.2, 29.3, 29.5, 29.6, 29.6, 31.9, 125.6, 128.3, 131.4, 136.6, 137.8,
194.5.
S-Dodecyl 4-Methoxybenzothioate (3c) (Table 2, Entry 2).8a The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-methoxybenzaldehyde (0.31 mL, 2.5 mmol), 1-
dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 3c as a
S-Dodecyl 4-Methylbenzothioate (3e) (Table 2, Entry 4).8a The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-methylbenzaldehyde (0.30 mL, 2.5 mmol), 1-
dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3e as a yellow oil (126 mg,
79% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.6 Hz, 3 H),
1.26−1.43 (m, 18 H), 1.64−1.67 (m, 2 H), 3.85 (s, 3 H), 3.04 (t, J =
7.4 Hz, 2 H), 7.21 (d, J = 8.0 Hz, 2 H), 7.86 (d, J = 8.0 Hz, 2 H). 13C
NMR (100 MHz, CDCl3): δ 14.1, 21.5, 22.6, 28.9, 28.9, 29.1, 29.3,
29.5, 29.6, 29.6, 31.9, 127.2, 129.1, 134.7, 143.8, 191.5.
1
yellow oil (148 mg, 88% yield). H NMR (400 MHz, CDCl3): δ 0.88
(t, J = 6.8 Hz, 3 H), 1.26−1.43 (m, 18 H), 1.61−1.67 (m, 2 H), 3.04
(t, J = 7.4 Hz, 2 H), 3.83 (s, 3 H), 6.90 (d, J = 8.8 Hz, 2 H), 7.94 (d, J
= 8.8 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 14.0, 22.6, 28.8, 28.9,
29.1, 29.3, 29.5, 29.5, 29.6, 29.6, 29.6, 31.9, 55.3, 113.6, 129.2, 130.1,
163.5, 190.5.
S-Dodecyl 2-Methylbenzothioate (3d) (Table 2, Entry 3).8a The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 2-methylbenzaldehyde (0.30 mL, 2.5 mmol), 1-
dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
S-Dodecyl 4-Bromobenzothioate (3f) (Table 2, Entry 5).8a The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-bromobenzaldehyde (467 mg, 2.5 mmol), 1-
dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
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a
Table 3. Iron-Catalyzed C−S Bond Formation between Various Aldehydes and Aryl Thiols
a
Reaction conditions unless otherwise stated: FeBr2 (0.0125 mmol, 2.5 mol %), TBHP (1.0 mmol, 70% in H2O), thiol (0.5 mmol), and aldehyde
b
(2.5 mmol) under a nitrogen atmosphere in H2O (1.5 mL) for 1 h. In acetonitrile (1.5 mL) at 90 °C for 1 h.
chromatography (SiO2, hexane) to provide 3f as a yellow oil (160 mg,
83% yield). 1H NMR (400 MHz, CDCl3) δ 0.87 (t, J = 6.8 Hz, 3 H),
1.25−1.42 (m, 18 H), 1.62−1.69 (m, 2 H), 3.05 (t, J = 7.4 Hz, 2 H),
7.56 (d, J = 8.4 Hz, 2 H), 7.81 (d, J = 8.4 Hz, 2 H). 13C NMR (100
MHz, CDCl3) δ 14.1, 22.7, 28.9, 29.1, 29.1, 29.3, 29.4, 29.5, 29.5, 29.6,
29.6, 31.9, 128.1, 128.6, 131.7, 135.9, 190.9.
3.10 (t, J = 7.4 Hz, 2 H), 7.70 (d, J = 8.4 Hz, 2 H), 8.06(d, J = 8.0 Hz,
2 H). 13C NMR (100 MHz, CDCl3): δ 14.0, 22.7, 28.9, 29.1, 29.3,
29.4, 29.4, 29.5, 29.6, 29.6, 29.6, 31.9, 123.5 (q, J = 271.3 Hz), 125.6
(q, J = 3.7 Hz), 127.5, 134.5 (q, J = 32.6 Hz), 140.0, 191.0. 19F NMR
(376 MHz, CDCl3): δ −65.6 (s). HRMS (EI-TOF) (m/z): calcd for
C20H29F3OS, 374.1891; found, 374.1887.
S-Dodecyl 3-Cyanobenzothioate (3h) (Table 2, Entry 7). The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 3-formylbenzonitrile (331 mg, 2.5 mmol), 1-
dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 3h as a
white solid (92 mg, 56% yield). Mp: 36−37 °C. 1H NMR (400 MHz,
CDCl3): δ 0.88 (t, J = 6.8 Hz, 3 H), 1.26−1.45 (m, 18 H), 1.65−1.72
S-Dodecyl 4-(Trifluoromethyl)benzothioate (3g) (Table 2, Entry
6). The general procedure for Table 2 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 4-(trifluoromethyl)benzaldehyde (0.35 mL, 2.5
mmol), 1-dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL,
1.0 mmol) in H2O (1.5 mL). The product was then purified by
column chromatography (SiO2, hexane) to provide 3g as a white solid
1
(93 mg, 50% yield). Mp: 39−40 °C. H NMR (400 MHz, CDCl3): δ
0.88 (t, J = 7.0 Hz, 3 H), 1.26−1.45 (m, 18 H), 1.65−1.72 (m, 2 H),
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49% yield). 1H NMR (400 MHz, CDCl3): δ 0.86−0.93 (m, 6 H), 1.16
(d, J = 7.2 Hz, 3 H), 1.26−1.37 (m, 18 H), 1.43−1.59 (m, 3 H), 1.70−
1.77 (m, 1 H), 2.52−2.58 (m, 1 H), 2.85 (t, J = 7.4 Hz, 2 H). 13C
NMR (100 MHz, CDCl3): δ 11.6, 14.1, 17.2, 22.7, 27.2, 28.5, 28.8,
29.1, 29.3, 29.5, 29.6, 31.9, 50.2, 204.0. HRMS (EI-TOF) (m/z): calcd
for C17H34OS, 286.2330; found, 286.2336.
Scheme 1. Plausible Mechanism
S-Decyl Benzothioate (3m) (Table 2, Entry 12).14 The general
procedure for Table 2 was followed using FeBr2 (2.8 mg, 0.0125
mmol), benzaldehyde (0.26 mL, 2.5 mmol), 1-decanethiol (0.108 mL,
0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in H2O (1.5 mL). The
product was then purified by column chromatography (SiO2, hexane)
to provide 3m as a yellow oil (95 mg, 75% yield). 1H NMR (400 MHz,
CDCl3): δ 0.88 (t, J = 6.8 Hz, 3 H), 1.26−1.44 (m, 14 H), 1.63−1.70
(m, 2H), 3.06 (t, J = 7.4 Hz, 2 H), 7.43 (t, J = 7.8 Hz, 2 H), 7.55 (t, J =
7.4 Hz, 1 H), 7.97 (d, J = 7.2 Hz, 2 H). 13C NMR (100 MHz, CDCl3):
δ 14.1, 22.6, 28.9, 29.0, 29.1, 29.3, 29.5, 29.5, 29.5, 31.8, 127.1, 128.5,
133.1, 137.2, 192.0.
S-Decyl 4-Chlorobenzothioate (3n) (Table 2, Entry 13). The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-chlorobenzaldehyde (359 mg, 2.5 mmol), 1-
decanethiol (0.108 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3n as a colorless oil (130
mg, 83% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.8 Hz, 3
H), 1.26−1.43 (m, 14 H), 1.63−1.70 (m, 2 H), 3.06 (t, J = 7.4 Hz, 2
H), 7.26−7.43 (m, 2 H), 7.89−7.92 (m, 2 H). 13C NMR (100 MHz,
CDCl3): δ 14.1, 22.6, 28.9, 29.1, 29.1, 29.3, 29.5, 29.5, 31.9, 128.5,
128.8, 135.5, 139.5, 190.8. HRMS (EI-TOF) (m/z): calcd for
C17H25ClOS, 312.1315; found, 312.1320.
S-Decyl 3-Methylbenzothioate (3o) (Table 2, Entry 14). The
general procedure for Table 2 was followed using FeBr2(2.8 mg,
0.0125 mmol), 3-methylbenzaldehyde (0.30 mL, 2.5 mmol), 1-
decanethiol (0.108 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in
H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3o as a yellow oil (117
mg, 80% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.8 Hz, 3
H), 1.26−1.43 (m, 14 H), 1.62−1.68 (m, 2 H), 2.39 (s, 3 H), 3.05 (t, J
= 7.2 Hz, 2 H), 7.28−7.36 (m, 2 H), 7.76−7.77 (m, 2 H). 13C NMR
(100 MHz, CDCl3): δ 14.1, 21.2, 22.6, 28.9, 29.0, 29.1, 29.3, 29.5,
29.5, 29.7, 31.8, 124.3, 127.6, 128.3, 133.9, 137.2, 138.3, 192.1. HRMS
(EI-TOF) (m/z): calcd for C18H28OS, 292.1861; found, 292.1852.
S-Decyl 4-Methoxybenzothioate (3p) (Table 2, Entry 15). The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-methoxybenzaldehyde (0.31 mL, 2.5 mmol), 1-
decanethiol (0.108 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in
H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 3p as a
yellow oil (99 mg, 64% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t,
J = 6.8 Hz, 3 H), 1.26−1.42 (m, 14 H), 1.64−1.68 (m, 2 H), 3.04 (t, J
= 7.4 Hz, 2 H), 3.85 (s, 3 H), 6.91 (d, J = 7.0 Hz, 2 H), 7.95 (d, J = 7.0
Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 14.1, 22.6, 28.9, 28.9, 29.1,
29.3, 29.5, 29.5, 29.7, 31.8, 55.4, 113.6, 129.3, 130.1, 163.6, 190.6.
HRMS (EI-TOF) (m/z): calcd for C18H28O2S, 308.1810; found,
308.1801.
(m, 2 H), 3.11 (t, J = 7.4 Hz, 2 H), 7.59 (t, J = 7.8 Hz, 2 H), 7.82−7.85
(m, 1 H), 8.16−8.24 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ 14.0,
22.6, 28.8, 29.0, 29.3, 29.4, 29.4, 29.5, 29.5, 31.8, 113.1, 117.7, 129.5,
130.7, 131.0, 135.9, 138.0, 190.1. HRMS (EI-TOF) (m/z): calcd for
C20H29NOS, 331.1970; found, 331.1979.
S-Dodecyl Naphthalene-2-carbothioate (3i) (Table 2, Entry 8).
The general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 2-naphthaldehyde (398 mg, 2.5 mmol), 1-dodeca-
nethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in
H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 3i as a
yellow oil (91 mg, 51% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t,
J = 6.8 Hz, 3 H), 1.26−1.46 (m, 18 H), 1.67−1.72 (m, 2 H), 3.12 (t, J
= 7.4 Hz, 2 H), 7.51−7.59 (m, 2 H), 7.84−7.87 (m, 2 H), 7.95 (d, J =
8.0 Hz, 1 H), 7.99 (dd, J = 1.2, 8.8 Hz, 1 H), 8.53 (s, 1 H). 13C NMR
(100 MHz, CDCl3): δ 14.1, 22.7, 29.0, 29.2, 29.3, 29.5, 29.6, 29.6,
29.6, 31.9, 123.2, 126.8, 127.7, 128.3, 128.4, 128.4, 129.5, 132.4, 134.5,
135.7, 192.0. HRMS (EI-TOF) (m/z): calcd for C23H32OS, 356.2174;
found, 356.2183.
S-Dodecyl Hexanethioate (3j) (Table 2, Entry 9). The general
procedure for Table 2 was followed using FeBr2 (2.8 mg, 0.0125
mmol), hexaldehyde (0.31 mL, 2.5 mmol), 1-dodecanethiol (0.125
mL, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in H2O (1.5 mL).
The product was then purified by column chromatography (SiO2,
1
hexane) to provide 3j as a yellow oil (95 mg, 63% yield). H NMR
(400 MHz, CDCl3): δ 0.86−0.91 (m, 6 H), 1.26−1.36 (m, 22 H),
1.54−1.57 (m, 2 H), 1.64−1.68 (m, 2 H), 2.53 (t, J = 7.6 Hz, 2 H),
2.86 (t, J = 7.4 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 13.8, 14.1,
22.3, 22.7, 25.4, 28.8, 28.8, 29.1, 29.3, 29.5, 29.5, 29.6, 29.6, 29.6, 31.1,
31.9, 44.1, 199.7. HRMS (EI-TOF) (m/z): calcd for C18H36OS,
300.24787; found, 300.2477.
S-Dodecyl 3-Methylbutanethioate (3k) (Table 2, Entry 10). The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), isovaleraldehyde (0.27 mL, 2.5 mmol), 1-dodeca-
nethiol (0.125 mL, 0.5 mmol). and TBHP (0.14 mL, 1.0 mmol) in
H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3k as a colorless oil (94
mg, 66% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.6 Hz, 3
H), 0.95 (d, J = 6.8 Hz, 6 H), 1.26−1.34 (m, 18 H), 1.52−1.57 (m, 2
H), 2.13−2.19 (m, 1 H), 2.41 (d, J = 7.2 Hz, 2 H), 2.86 (t, J = 7.2 Hz,
2 H). 13C NMR (100 MHz, CDCl3): δ 14.1, 22.2, 22.7, 26.4, 28.8,
29.1, 29.3, 29.5, 29.5, 29.6, 31.9, 52.9, 199.1. HRMS (EI-TOF) (m/z):
calcd for C17H34OS, 286.2330; found, 286.2336.
S-Decyl 4-Bromobenzothioate (3q) (Table 2, Entry 16). The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-bromobenzaldehyde (467 mg, 2.5 mmol), 1-
decanethiol (0.108 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3q as a colorless oil (130
mg, 73% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.0 Hz, 3
H), 1.26−1.41 (m, 14 H), 1.62−1.68 (m, 2 H), 3.06 (t, J = 7.2 Hz, 2
H), 7.55−7.59 (m, 2 H), 7.81−7.84 (m, 2 H). 13C NMR (100 MHz,
CDCl3): δ 14.1, 22.6, 28.9, 29.1, 29.2, 29.3, 29.4, 29.5, 29.5, 31.9,
128.2, 128.6, 131.8, 136.0, 191.1. HRMS (EI-TOF) (m/z): calcd for
C17H25BrOS, 356.0809; found, 356.0803.
S-Dodecyl 2-Methylbutanethioate (3l) (Table 2, Entry 11). The
general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 2-methylbutyraldehyde (0.27 mL, 2.5 mmol), 1-
dodecanethiol (0.125 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3l as a colorless oil (70 mg,
S-Decyl 4-(Trifluoromethyl)benzothioate (3r) (Table 2, Entry 17).
The general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 4-(trifluoromethyl)benzaldehyde (0.35 mL, 2.5 mmol),
1-decanethiol (0.108 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol)
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in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3r as a yellow oil (118 mg,
68% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.8 Hz, 3 H),
1.27−1.44 (m, 14 H), 1.65−1.72 (m, 2 H), 3.10 (t, J = 7.2 Hz, 2 H),
7.71 (d, J = 8.4 Hz, 2 H), 8.06 (d, J = 8.4 Hz, 2 H). 13C NMR (100
MHz, CDCl3): δ 14.1, 22.7, 28.9, 29.1, 29.3, 29.4, 29.4, 29.5, 29.5,
31.9, 123.5 (q, J = 271.2 Hz), 125.6 (q, J = 3.8 Hz), 127.5, 134.5 (q, J
= 32.6 Hz), 140.0, 191.2. 19F NMR (376 MHz, CDCl3) δ −64.7 (s).
HRMS (EI-TOF) (m/z): calcd for C18H25F3OS, 346.1578; found,
346.1587.
S-(4-(Trifluoromethyl)phenyl) 4-Methoxybenzothioate (5b)
(Table 3, Entry 2).8a The general procedure for Table 3 was followed
using FeBr2 (2.8 mg, 0.0125 mmol), 4-methoxybenzaldehyde (0.31
mL, 2.5 mmol), 4-(trifluoromethyl)benzenethiol (0.071 mL, 0.5
mmol), and TBHP (0.14 mL, 1.0 mmol) in H2O (1.5 mL). The
product was then purified by column chromatography (SiO2, hexane/
EtOAc, 100:1) to provide 5b as a white solid (118 mg, 75% yield).
Mp: 105−106 °C (lit.8a 105−106 °C). 1H NMR (400 MHz, CDCl3):
δ 3.82 (s, 3 H), 6.92 (d, J = 10.2 Hz, 2 H), 7.60 (d, J = 8.4 Hz, 2 H),
7.65 (d, J = 8.4 Hz, 2 H), 7.96 (d, J = 6.4 Hz, 2 H). 13C NMR (100
MHz, CDCl3): δ 55.6, 114.0, 123.9 (q, J = 271.0 Hz), 125.9 (q, J = 3.7
Hz), 127.9, 128.9, 129.8, 131.2 (q, J = 32.6 Hz), 132.5, 135.2, 164.3,
187.2. 19F NMR (376 MHz, CDCl3): δ −64.3 (s).
S-Decyl Naphthalene-2-carbothioate (3s) (Table 2, Entry 18).
The general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 2-naphthaldehyde (398 mg, 2.5 mmol), 1-decanethiol
(0.108 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in H2O (1.5
mL). The product was then purified by column chromatography
(SiO2, hexane/EtOAc, 100:1) to provide 3s as a yellow oil (74 mg,
45% yield). 1H NMR (400 MHz, CDCl3): δ 0.88 (t, J = 6.8 Hz, 3 H),
1.25−1.44 (m, 14 H), 1.68−1.72 (m, 2 H), 3.11 (t, J = 7.2 Hz, 2 H),
7.52−7.57 (m, 2 H), 7.84−7.87 (m, 2 H), 7.94 (d, J = 8.0 Hz, 1 H),
7.99 (d, J = 8.4 Hz, 1 H), 8.52 (s, 1 H). 13C NMR (100 MHz, CDCl3):
δ 14.1, 22.7, 29.0, 29.2, 29.3, 29.5, 29.5, 29.6, 29.7, 31.9, 123.2, 126.8,
127.7, 128.3, 128.3, 128.4, 129.5, 132.4, 134.5, 135.7, 192.0. HRMS
(EI-TOF) (m/z): calcd for C21H28OS, 328.1861; found, 328.1850.
S-(2-Methyl-1-butyl) 4-Methoxybenzothioate (3t) (Table 2, Entry
19).8a The general procedure for Table 2 was followed using FeBr2
(2.8 mg, 0.0125 mmol), 4-methoxybenzaldehyde (0.31 mL, 2.5
mmol), 2-methyl-1-butanethiol (0.065 mL, 0.5 mmol), and TBHP
(0.14 mL, 1.0 mmol) in ACN (1.5 mL). The product was then purified
by column chromatography (SiO2, hexane/EtOAc, 100:1) to provide
3t as a yellow oil (60 mg, 50% yield). 1H NMR (400 MHz, CDCl3): δ
0.93 (t, J = 7.4 Hz, 3 H), 0.99 (d, J = 6.4 Hz, 3 H), 1.23−1.30 (m, 1
H), 1.47−1.54 (m, 1 H), 1.65- 1.70 (m, 1 H), 2.93 (dd, J = 7.2, 12.8
Hz, 1 H), 3.11 (dd, J = 5.6, 12.8 Hz, 1 H), 3.84 (s, 3 H), 6.91 (d, J =
10.2 Hz, 2 H), 7.96 (d, J = 10.2 Hz, 2 H). 13C NMR (100 MHz,
CDCl3): δ 11.3, 18.8, 28.7, 35.1, 35.4, 55.4, 113.6, 129.3, 130.1, 163.6,
190.6.
S-(4-Chlorophenyl) 4-Methoxybenzothioate (5c) (Table 3, Entry
3).8a The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 4-methoxybenzaldehyde (0.31 mL, 2.5 mmol), 4-
chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 5c as a
white solid (83 mg, 59% yield). Mp: 94−95 °C (lit.8a 96−97 °C). H
1
NMR (400 MHz, CDCl3): δ 3.88 (s, 3 H), 6.96 (d, J = 8.8 Hz, 2 H),
7.42 (s, 4 H), 7.99 (d, J = 8.4 Hz, 2 H). 13C NMR (100 MHz, CDCl3):
δ 55.5, 114.0, 126.1, 129.1, 129.4, 129.7, 135.8, 136.4, 164.1, 188.0.
S-(3-(Trifluoromethyl)phenyl) 4-Methylbenzothioate (5d) (Table
3, Entry 4).8a The general procedure for Table 3 was followed using
FeBr2 (2.8 mg, 0.0125 mmol), 4-methylbenzaldehyde (0.30 mL, 2.5
mmol), 3-(trifluoromethyl)benzenethiol (0.070 mL, 0.5 mmol), and
TBHP (0.14 mL, 1.0 mmol) in H2O (1.5 mL). The product was then
purified by column chromatography (SiO2, hexane) to provide 5d as a
yellow solid (104 mg, 70% yield). Mp: 59−60 °C(lit.8a 62−63 °C). 1H
NMR (400 MHz, CDCl3): δ 2.42 (s, 3 H), 7.28 (d, J = 8.0 Hz, 2 H),
7.55 (t, J = 7.8 Hz, 1 H), 7.68(d, J = 8.0 Hz, 2 H), 7.78 (s, 1 H), 7.91
(d, J = 8.0 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 21.7, 123.6 (q, J
= 271.2 Hz), 126.1 (q, J = 3.7 Hz), 127.6, 129.0, 129.3, 129.3, 129.5,
129.5, 131.5 (q, J = 32.5 Hz), 131.7 (q, J = 3.8 Hz), 133.6, 138.5,
145.1, 188.6. 19F NMR (376 MHz, CDCl3): δ −64.2 (s).
Ethyl 2-((3-Methylbenzoyl)thio)acetate (3u) (Table 2, Entry 20).8a
The general procedure for Table 2 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 3-methylbenzaldehyde (0.30 mL, 2.5 mmol), ethyl 2-
mercaptoacetate (0.056 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in H2O (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 3u as a yellow oil (48 mg,
40% yield). 1H NMR (400 MHz, CDCl3): δ 1.30 (t, J = 6.8 Hz, 3 H),
2.41 (s, 3 H), 3.88 (s, 2 H), 4.23 (q, J = 7.2 Hz, 2 H), 7.32−7.41 (m, 2
H), 7.77−7.79 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ 14.1, 21.2,
31.4, 61.8, 124.6, 127.8, 128.5, 134.5, 136.1, 138.6, 168.8, 190.2.
General Procedure for Table 3. A Schlenk tube equipped with a
magnetic stir bar was charged with FeBr2 (2.8 mg, 0.0125 mmol) in a
nitrogen-filled glovebox. The Schlenk tube was then covered with a
rubber septum and removed from the glovebox. Under a nitrogen
atmosphere, thiol (0.5 mmol), aldehyde (2.5 mmol), TBHP (0.14 mL,
1.0 mmol), and H2O (1.5 mL) were added via syringe, and the
Schlenk tube was connected to a nitrogen-filled balloon and heated at
110 °C in an oil bath. After being stirred at this temperature for 1 h,
the heterogeneous mixture was cooled to room temperature and
diluted with ethyl acetate (20 mL). The resulting solution was directly
filtered through a pad of silica gel, then washed with ethyl acetate (20
mL), and concentrated to give the crude material, which was then
purified by column chromatography (SiO2, hexane) to yield 5.
S-(4-Chlorophenyl) 4-Chlorobenzothioate (5a) (Table 3, Entry
1).8a The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 4-chlorobenzaldehyde (359 mg, 2.5 mmol), 4-
chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 5a as a white solid (87 mg,
S-(4-Chlorophenyl) 2-Methylbenzothioate (5e) (Table 3, Entry
5).8a The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 2-methylbenzaldehyde (0.30 mL, 2.5 mmol), 4-
chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 5e as a white solid (86 mg,
66% yield). Mp: 90−91 °C (lit.8a 90−91 °C). H NMR (400 MHz,
1
CDCl3): δ 2.49 (s, 3 H), 7.25−7.32 (m, 2 H), 7.41−7.45 (m, 5 H),
7.93 (d, J = 8.0 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 20.8, 125.9,
126.6, 128.6, 129.5, 131.8, 132.2, 135.9, 136.1, 136.3, 137.6, 191.5.
S-(4-Chlorophenyl) 3-Cyanobenzothioate (5f) (Table 3, Entry 6).
The general procedure for Table 3 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 3-formylbenzonitrile (331 mg, 2.5 mmol), 4-
chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 5f as a white
1
solid (47 mg, 40% yield). Mp: 128−129 °C. H NMR (400 MHz,
CDCl3): δ 7.44 (s, 4H), 7.64 (t, J = 8.0 Hz, 1 H), 7.89 (d, J = 7.6 Hz, 1
H), 8.22 (d, J = 7.6 Hz, 1 H), 8.28 (s, 1 H). 13C NMR (100 MHz,
CDCl3): δ 113.3, 117.5, 124.5, 129.7, 129.8, 130.9, 131.3, 136.1, 136.4,
136.6, 137.1, 187.9. HRMS (EI-TOF) (m/z): calcd for C14H8ClNOS,
273.0015; found, 273.0007.
S-(4-(Trifluoromethyl)phenyl) 3-Methylbenzothioate (5g) (Table
3, Entry 7). The general procedure for Table 3 was followed using
FeBr2 (2.8 mg, 0.0125 mmol), 3-methylbenzaldehyde (0.30 mL, 2.5
mmol), 4-(trifluoromethyl)benzenethiol (0.071 mL, 0.5 mmol), and
TBHP (0.14 mL, 1.0 mmol) in ACN (1.5 mL). The product was then
purified by column chromatography (SiO2, hexane) to provide 5g as a
white solid (90 mg, 61% yield). Mp: 72−73 °C. 1H NMR (400 MHz,
CDCl3): δ 2.44 (s, 3 H), 7.36−7.45 (m, 2 H), 7.67 (dd, J = 8.0, 24.0
Hz, 4 H), 7.82−7.83 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ 21.3,
123.8 (q, J = 271.2 Hz), 125.9 (q, J = 3.7 Hz), 128.0, 128.7, 131.3 (q, J
= 32.5 Hz), 132.3, 134.8, 135.2, 136.2, 138.8, 189.0. 19F NMR (376
62% yield). Mp: 135−136 °C (lit.8a 136−137 °C). H NMR (400
1
MHz, CDCl3): δ 7.42 (s, 4 H), 7.45 (d, J = 8.4 Hz, 2 H), 7.94 (d, J =
8.4 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 125.3, 128.8, 129.1,
129.5, 134.6, 136.1, 136.2, 140.3, 188.5.
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MHz, CDCl3): δ −64.2 (s). HRMS (EI-TOF) (m/z): calcd for
C15H11F3OS, 296.0483; found, 296.0491.
0.0125 mmol), hexaldehyde (0.31 mL, 2.5 mmol), 4-bromobenzene-
thiol (0.099 g, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in ACN
(1.5 mL). The product was then purified by column chromatography
S-(4-(Trifluoromethyl)phenyl) 4-Bromobenzothioate (5h) (Table
3, Entry 8). The general procedure for Table 3 was followed using
FeBr2 (2.8 mg, 0.0125 mmol), 4-bromobenzaldehyde (467 mg, 2.5
mmol), 4-(trifluoromethyl)benzenethiol (0.071 mL, 0.5 mmol), and
TBHP (0.14 mL, 1.0 mmol) in H2O (1.5 mL). The product was then
purified by column chromatography (SiO2, hexane) to provide 5h as a
white solid (115 mg, 64% yield). Mp: 94−95 °C. 1H NMR (400 MHz,
CDCl3): δ 7.62−7.71(m, 6 H), 7.87 (d, J = 7.6 Hz, 2 H). 13C NMR
(100 MHz, CDCl3): δ 55.5, 114.0, 123.8 (q, J = 225.7 Hz), 123.7 (q, J
= 271.1 Hz), 126.0 (q, J = 3.6 Hz), 128.6, 129.2, 131.6 (t, J = 16.3 Hz),
132.2, 134.9, 135.1, 187.9. 19F NMR (376 MHz, CDCl3): δ −64.4 (s).
HRMS (EI-TOF) (m/z): calcd for C14H8BrF3OS, 359.9431; found,
359.9439.
1
(SiO2, hexane) to provide 5n as a yellow oil (121 mg, 85% yield). H
NMR (400 MHz, CDCl3): δ 0.89−0.92 (m, 3 H), 1.25−1.36 (m, 4
H), 1.69−1.73 (m, 2 H), 2.65 (t, J = 7.6 Hz, 2 H), 7.26 (d, J = 7.2 Hz,
2 H), 7.53 (d, J = 8.4 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 13.8,
22.3, 25.2, 31.0, 43.7, 123.9, 127.0, 132.3, 135.9, 196.8. HRMS (EI-
TOF) (m/z): calcd for C12H15BrOS, 286.0027; found, 286.0028.
S-(4-Chlorophenyl) Hexanethioate (5o) (Table 3, Entry 15).17 The
general procedure for Table 3 was followed using FeBr2 (2.8 mg,
0.0125 mmol), hexaldehyde (0.31 mL, 2.5 mmol), 4-chlorobenzene-
thiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in ACN
(1.5 mL). The product was then purified by column chromatography
1
(SiO2, hexane) to provide 5o as a yellow oil (103 mg, 85% yield). H
S-(4-Chlorophenyl) Thiophene-2-carbothioate (5i) (Table 3, Entry
9). The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 2-thiophenecarboxaldehyde (0.24 mL, 2.5 mmol),
4-chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 5i as a
NMR (400 MHz, CDCl3): δ 0.83−0.92 (m, 3 H), 1.26−1.34 (m, 4
H), 1.69−1.72 (m, 2 H), 2.64 (t, J = 7.4 Hz, 2 H), 7.34 (dd, J = 8.4,
19.6 Hz, 4 H). 13C NMR (100 MHz, CDCl3): δ 13.8, 22.3, 25.2, 31.0,
43.7, 126.4, 129.4, 135.7, 197.0.
S-(4-Chlorophenyl) Furan-2-carbothioate (5p) (Table 3, Entry
16).18 The general procedure for Table 3 was followed using FeBr2
(2.8 mg, 0.0125 mmol), 2-furancarboxaldehyde (0.21 mL, 2.5 mmol),
4-chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 5p as a
white solid (50 mg, 42% yield). Mp: 102−103 °C (lit.18 106−107 °C).
1H NMR (400 MHz, CDCl3): δ 6.58 (q, J = 1.7, 1 H), 7.27 (dd, J =
1
yellow oil (100 mg, 79% yield). H NMR (400 MHz, CDCl3): δ 7.15
(t, J = 4.2 Hz, 1 H), 7.39−7.45 (m, 4 H), 7.67 (d, J = 4.4 Hz, 1 H),
7.89 (d, J = 3.6 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ 125.3,
128.0, 129.4, 131.8, 133.5, 136.0, 136.2, 140.9, 181.4. HRMS (EI-
TOF) (m/z): calcd for C11H7ClOS2: 253.9627; found, 253.9620.
S-4-Tolyl Thiophene-2-carbothioate (5j) (Table 3, Entry 10).8a
The general procedure for Table 3 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 2-thiophenecarboxaldehyde (0.24 mL, 2.5 mmol), 4-
methylbenzenethiol (0.063 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 5j as a
yellow oil (61 mg, 52% yield). 1H NMR (400 MHz, CDCl3): δ 2.39 (s,
3 H), 7.14 (t, J = 4.4 Hz, 1 H), 7.25 (d, J = 8.0 Hz, 2 H), 7.40 (d, J =
8.0 Hz, 2 H), 7.64 (d, J = 4.8 Hz, 1 H), 7.89 (d, J = 4.0 Hz, 1 H). 13C
NMR (100 MHz, CDCl3): δ 21.3, 123.3, 127.9, 130.1, 131.5, 133.0,
135.0, 139.9, 141.4, 182.5.
0.8, 4.0 Hz, 1H), 7.42 (s,4H), 7.63 (dd, J = 0.8, 1.6 Hz, 1H). 13C NMR
(100 MHz, CDCl3): δ 112.5, 116.5, 124.6, 129.5, 136.1, 136.3, 146.6,
150.0, 178.1.
S-(4-Chlorophenyl) Pyridine-2-carbothioate (5q) (Table 3, Entry
17). The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 2-pyridinecarboxaldehyde (0.24 mL, 2.5 mmol), 4-
chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 10:1) to provide 5q as a white
1
solid (39 mg, 31% yield). Mp: 105−106 °C. H NMR (400 MHz,
S-Phenyl Thiophene-2-carbothioate (5k) (Table 3, Entry 11).15
The general procedure for Table 3 was followed using FeBr2 (2.8 mg,
0.0125 mmol), 2-thiophenecarboxaldehyde (0.24 mL, 2.5 mmol),
benzenethiol (0.06 mL, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol)
in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane/EtOAc, 100:1) to provide 5k as a
yellow oil (50 mg, 46% yield). 1H NMR (400 MHz, CDCl3): δ 7.15 (t,
J = 4.2 Hz, 1 H), 7.44 (t, J = 3.2 Hz, 3 H), 7.51−7.53 (m, 2 H), 7.65
(d, J = 5.2 Hz, 1 H) 7.90 (d, J = 4.0 Hz, 1 H). 13C NMR (100 MHz,
CDCl3): δ 126.9, 128.0, 129.2, 129.6, 131.6, 133.2, 135.0, 141.3, 182.0.
S-(4-Bromophenyl) 4-Methylbenzothioate (5l) (Table 3, Entry
12). The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 4-methylbenzaldehyde (0.30 mL, 2.5 mmol), 4-
bromobenzenethiol (0.099 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 5l as a white solid (92 mg,
60% yield). Mp: 120−121 °C. 1H NMR (400 MHz, CDCl3): δ 2.43 (s,
3 H), 7.28 (d, J = 8.0 Hz, 2 H), 7.36 (d, J = 8.4 Hz, 2 H), 7.57 (d, J =
8.4 Hz, 2 H), 7.90 (d, J = 8.4 Hz, 2 H). 13C NMR (100 MHz, CDCl3):
δ 21.7, 124.1, 126.6, 127.6, 129.4, 132.4, 133.7, 136.5, 144.8, 189.0.
HRMS (EI-TOF) (m/z): calcd for C14H11BrOS, 305.9714; found,
305.9718.
CDCl3): δ 7.42−7.47 (m, 4 H), 7.57 (t, J = 6.0 Hz, 1 H), 7.88 (t, J =
7.6 Hz, 1 H), 7.96 (d, J = 8.0 Hz, 1 H), 8.74 (d, J = 4.8 Hz, 1 H). 13C
NMR (100 MHz, CDCl3): δ 120.8, 126.7, 128.2, 129.4, 135.8, 136.1,
137.4, 149.2, 151.3, 191.5. HRMS (EI-TOF) (m/z): calcd for
C12H8ClNOS, 249.0015; found, 249.0020.
S-(4-Bromophenyl) 2-Methylpropanethioate (5r) (Table 3, Entry
18). The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), isobutyraldehyde (0.23 mL, 2.5 mmol), 4-
bromobenzenethiol (0.099 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 5r as a colorless oil (83 mg,
64% yield). 1H NMR (400 MHz, CDCl3): δ 1.26 (d, J = 6.8 Hz, 6 H),
2.81−2.88 (m, 1 H), 7.26 (d, J = 8.4 Hz, 2 H), 7.52 (d, J = 8.4 Hz, 1
H). 13C NMR (100 MHz, CDCl3): δ 19.3, 43.0, 123.8, 126.9, 132.2,
136.0, 201.2. HRMS (EI-TOF) (m/z): calcd for C10H11ClOS,
257.9714; found, 257.9708.
S-(4-Bromophenyl) 3-Methylbutanethioate (5s) (Table 3, Entry
19). The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), isovaleraldehyde (0.27 mL, 2.5 mmol), 4-
bromobenzenethiol (0.099 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 5s as a colorless oil (81
mg, 59% yield). 1H NMR (400 MHz, CDCl3): δ 1.00 (d, J = 6.4 Hz, 6
H), 2.17−2.24 (m, 1 H), 2.53 (d, J = 7.2 Hz, 2 H), 7.25 (d, J = 7.4 Hz,
2 H), 7.53 (d, J = 8.4 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 22.2,
26.5, 52.4, 123.9, 127.0, 132.3, 135.8, 196.2. HRMS (EI-TOF) (m/z):
calcd for C11H13BrOS, 271.9870; found, 271.9872.
S-(4-Chlorophenyl) 2-Methylbutanethioate (5t) (Table 3, Entry
20). The general procedure for Table 3 was followed using FeBr2 (2.8
mg, 0.0125 mmol), 2-methylbutyraldehyde (0.27 mL, 2.5 mmol), 4-
chlorobenzenethiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0
mmol) in ACN (1.5 mL). The product was then purified by column
chromatography (SiO2, hexane) to provide 5t as a colorless oil (64 mg,
S-(4-Chlorophenyl) Benzothioate (5m) (Table 3, Entry 13).16 The
general procedure for Table 3 was followed using FeBr2 (2.8 mg,
0.0125 mmol), benzaldehyde (0.26 mL, 2.5 mmol), 4-chlorobenzene-
thiol (0.074 g, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in ACN
(1.5 mL). The product was then purified by column chromatography
(SiO2, hexane) to provide 5m as a white solid (64 mg, 51% yield). Mp:
1
72−73 °C. H NMR (400 MHz, CDCl3): δ 7.43−7.50 (m, 6 H),
7.59−7.63 (m, 1 H), 8.00 (d, J = 5.2 Hz, 2 H). 13C NMR (100 MHz,
CDCl3): δ 125.7, 127.4, 128.8, 129.5, 133.8, 135.9, 136.2, 136.3, 189.6.
S-(4-Bromophenyl) Hexanethioate (5n) (Table 3, Entry 14). The
general procedure for Table 3 was followed using FeBr2 (2.8 mg,
4567
dx.doi.org/10.1021/jo500574p | J. Org. Chem. 2014, 79, 4561−4568

The Journal of Organic Chemistry
Article
56% yield). 1H NMR (400 MHz, CDCl3): δ 0.97 (t, J = 7.6 Hz, 3 H),
1.22−1.26 (m, 3 H), 1.50−1.57 (m, 1 H), 1.76−1.83 (m, 1 H), 2.65−
2.70 (m, 1 H), 7.31−7.38 (m, 4 H). 13C NMR (100 MHz, CDCl3): δ
11.6, 17.1, 27.1, 50.0, 126.4, 129.3, 135.5, 135.7, 201.0. HRMS (EI-
TOF) (m/z): calcd for C11H13ClOS, 228.0376; found, 228.0378.
S-(4-Bromophenyl) Octanethioate (5u) (Table 3, Entry 21). The
general procedure for Table 3 was followed using FeBr2 (2.8 mg,
0.0125 mmol), octanaldehyde (0.39 mL, 2.5 mmol), 4-bromobenze-
nethiol (0.099 g, 0.5 mmol), and TBHP (0.14 mL, 1.0 mmol) in ACN
(1.5 mL). The product was then purified by column chromatography
(SiO2, hexane) to provide 5u as a colorless oil (73 mg, 46% yield). 1H
NMR (400 MHz, CDCl3): δ 0.87−0.88 (m, 3 H), 1.28−1.32 (m, 8
H), 1.67−1.74 (m, 2 H), 2.65 (t, J = 7.4 Hz, 2 H), 7.26 (d, J = 8.0 Hz,
2 H), 7.53 (d, J = 8.4 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 14.0,
22.5, 25.5, 28.9, 31.6, 43.7, 123.9, 127.0, 132.3, 135.9, 196.8. HRMS
(EI-TOF) (m/z): calcd for C14H19BrOS, 314.0340; found, 314.0335.
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AUTHOR INFORMATION
■
Corresponding Author
*E-mail: cfalee@dragon.nchu.edu.tw.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The Ministry of Science and Technology, Taiwan (Grant NSC
101-2113-M-005-008-MY3), the National Chung Hsing
University, and the Center of Nanoscience and Nano-
technology (NCHU) are gratefully acknowledged for financial
support. We also thank Prof. Fung-E Hong (NCHU) for
sharing his GC−MS instruments. C.-F.L. is a Golden-Jade
Fellow of the Kenda Foundation, Taiwan.
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