A sustainable oxidative esterification of thiols with alcohols by a cobalt nanocatalyst supported on doped carbon

Article abstract of DOI:10.1039/c8gc00441b

Here, we developed a new cobalt nanocatalyst supported on N-SiO₂-doped activated carbon (Co/N-SiO₂-AC), which exhibits excellent catalytic performance towards the oxidative esterification of (hetero)aryl and alkyl thiols with alcohols. A wide array of sulfinic esters were efficiently afforded in an exclusive chemoselective manner. The developed synthetic method proceeds with the merits of mild reaction conditions, broad substrate scope, operational simplicity, good functional group tolerance, earth-abundant and reusable cobalt catalysts, the utilization of renewable alcohols as the coupling partners and molecular O₂ as the sole oxidant, which offers a practical method for sustainable synthesis of sulfinic esters.

Full text of DOI:10.1039/c8gc00441b

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A sustainable oxidative esterification of thiols with alcohols by a
cobalt nanocatalyst supported on doped carbon
Changjian Zhou,a Zhenda Tan,a Huanfeng Jianga and Min Zhang*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Here, we developed a new cobalt nanocatalyst supported on N-SiO2-doped activated carbon (Co/N–SiO2–AC), which
exhibits excellent catalytic performance towards the oxidative esterification of (hetero)aryl and alkyl thiols with alcohols. A
wide array of sulfinic esters were efficiently afforded in an exclusive chemoselective manner. The developed synthetic
method proceeds with merits of mild reaction conditions, broad substrate scope, operational simplicity, good functional
group tolerance, earth-abundant and reusable cobalt catalysts, the utilization of renewable alcohols as the coupling
partners and molecular O2 as the sole oxidant, which offers a practical way for sustainable synthesis of sulfinic esters.
www.rsc.org/
with methanol in the presence of molecular sieves (Scheme 1e).13
Interestingly, the aerobic copper-catalyzed cross-coupling of
sulfonyl hydrazides (Scheme 1f)14 or thiols (Scheme 1g)15 with
Introduction
Sulfinic esters constitute an important class of organic compounds，
which exhibit diverse biological and therapeutic activities such as
stimulating the glucose uptake in muscle cells,1a and regulating the
mitochondrial function of the Parkinsonism protein DJ-1.1b In
addition, due to the two faces of chemical property,2 sulfinic esters
can serve as both electrophiles and nucleophiles, which have been
extensively employed for the preparation of a wide array of
functional products such as sulfonylmethyl isonitriles,3 α, β-
alcohols have also been nicely demonstrated. Despite the
significant utility, most of these transformations suffer from one or
more drawbacks such as the need for excessive amount of waste-
generating agents [i.e., NBS, Br2, PhI(OCOCF3)2, DCC, H2SO4, etc.],
difficult catalyst reusability, harsh reaction conditions, poor
functional group tolerance, limited chemoselectivity and tedious
synthetic procedures to access substrates. Hence, there is a high
demand for efficient and environmentally benign new methods for
the synthesis of sulfinic esters from readily available starting
materials with natural abundant metal catalysts, preferably
recyclable and reusable ones.
unsaturated
ketones,4
sulfinamides
and
sulfonamides5
sulfonimidamides,6 sulfoxides7 and sulfonyl allenes8.
Due to the interesting applications, the development of
alternative approaches to access sulfinic esters is of high
importance in synthetic chemistry. The early representative
protocols are mainly based on the oxidation of diaryl disulfides with
O
NBS (3 equiv), K2CO3, 0 oC - r.t.
or Br2 (3 equiv), Na2CO3
S
(a)
(b)
ArSSAr
Ar
OR'
+
R'OH
excess oxidants [i.e., N-bromosuccinimide (NBS),9a Br2 or
or PhI(OCOCF3)2 (3 equiv), reflux
4
PhI(OCOCF3)29b] in the presence of alcohols (Scheme 1a). Later, the
base-promoted reaction of sulfinic acid chlorides with alcohols at -
78 oC10 (Scheme 1b) and the condensation of sulfinic acids with
alcohols in the presence of N,N’-dicyclohexylcarbodiimide (DCC)
(Scheme 1c)11 have offered useful alternatives to realize the related
end. In 2015, Sun and the co-workers have demonstrated a new
method via in situ NBS-mediated C-S bond cleavage of t-Butyl
sulfoxide to form sulfinyl bromide followed by alcoholysis (Scheme
1d).12 More recently, the group of Menezes and Oliveira has
illustrated a sulfuric acid-promoted coupling of sulfinic acid salts
O
S
O
S
pyridine or i-Pr2NEt, -78 o
C
+
+
+
R'OH
R'OH
R'OH
R
OR'
R
Cl
O
S
O
c
( )
DCC (1 equiv)
S
Ar
OH
t-Bu
ONa
Ar
R
OR'
O
O
NBS, AcOH, DCM, r. t.
S
d
( )
R
OR'
O
S
O
H2SO4 (2 equiv), MS (4 Ao)
(e)
(f)
+
+
R'OH
S
Ar
Ar
R
OR'
OMe
SR'
O
S
O
S
Cu(OTf)2 (20 mol %)
O2, 40 oC, 12 h
MeOH
NHNH2
R
R
O
O
S
CuI (5 mol %), TBD (10 mol %)
O2, 65 oC, 18 h
(TBD: 1,5,7-triazabicyclo[4.4.0]dec-5-ene)
+
RSH
+
R'OH
S
R
OR'
(g)
O
Scheme 1 The existed representative methods to access sulfinic esters.
As our continuous research interests in the transformation of
abundant and sustainable alcohol resources into functional
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molecules16 and the search for efficient methods to construct N-
heterocycles17 as well as the design of non-noble metal catalysts,17b
we were therefore motivated to develop a new protocol for the
synthesis of sulfinic esters by employing heterogeneous catalysts. In
consideration of the natural abundance of cobalt and its capability
in activation of inert substrates via oxidation18 as well as the
potential of silica in adjusting the micropore size of carbon
materials to favor the mass transfer,19 we herein report the
preparation and characterization of a new cobalt nanocatalyst
supported on N–SiO2-doped activated carbon (Co/N–SiO2–AC), and
describe, for the first time, its application on oxidative esterification
of thiols with alcohols in the presence of molecular O2 (Scheme 2).
Entry
1
Catalyst
Co/N–SiO2–AC
Co/N–AC
t (h)
24
24
24
24
24
24
24
24
24
24
24
24
Yield (%)b
0c
70
0
2
3
N–SiO2–AC
4
Co/SiO2–AC
Co(OAc)2·4H2O
Co/N–SiO2–AC
-
0
5
trace
96
0
6
7
8
Co/N–SiO2–AC
Cu/N–SiO2–AC
Mn/N–SiO2–AC
Pd/N–SiO2–AC
Fe/N–SiO2–AC
0d
9
0
O
S
reusable Co/N-SiO2-AC
60-80 oC, O2, K2CO3
10
11
12
0
+
RSH
R'OH
0
R
OR'
0
Scheme 2 Oxidative esterification of thiols with alcohols.
a
Conditions: unless otherwise stated, the reaction of 1a (0.5 mmol), K2CO3
(0.1 mmol), catalyst (40 mg, Co: 1.46 mol %) in CH3OH (1.5 mL) was charged
with O2 and stirred at 60 oC for 24 h. b GC yield using hexadecane as an
internal standard. c Catalyst without pyrolysis. d Without base.
Results and discussion
Typically, the cobalt catalyst was synthesized via the following
procedure: The mixture of Co(OAc)2·4H2O and 1,10-phenanthroline
in ethanol was stirred at 100 oC for 1 hour to form the cobalt
complex. Then, silica was introduced into the above solution via in
situ hydrolysis of the added Si(OC2H5)4 (TEOS) with aqueous
ammonia. The resulting mixture was followed by successive
addition of activated carbon (AC) support, refluxing at 100 oC for 5 h
and removal of the solvent, the reaming sample was pyrolyzed at
o
800 C under a flow of argon, and etched the non-supported cobalt
particles generated during the pyrolysis process with aqueous HCl.
The prepared material is named as Co/N–SiO2–AC with a Co content
of 1.08 wt % (measured by ICP-OES analysis). In addition, for the
purpose of comparison, the materials without addition of Si
precursor, 1,10-phenanthroline, metal source during the preparing
process were denoted as Co/N–AC, Co/SiO2–AC and Metal/N–SiO2–
AC, respectively.
Fig. 1 TEM images of Co/N–SiO2–AC and the corresponding elemental
mapping images of C, N, Si and Co, respectively.
With the catalyst materials prepared, they were then applied to
the oxidative esterification of 4-methylbenzenethiol 1a with
methanol 2a. By performing the reaction at 60 oC in the presence of
molecular O2 and catalytic amounts of K2CO3, we tested the effect
of Co/N–SiO2–AC (without pyrolysis), Co/N–AC, N–SiO2–AC,
Co/SiO2–AC, Co(OAc)2·4H2O, Co/N–SiO2–AC, AC, N–AC, SiO2–AC and
Co/AC on the reaction (Table 1, entries 1–6 and Table S1, entries 1–
4, ESI†), only Co/N–AC and Co/N–SiO2–AC were able to afford the
sulfinic ester 3aa in 70% and 96% yields, respectively (entries 2 and
6), implying that the Co–N species plays a decisive role on the
reaction. Then, Co/N–SiO2–AC catalyst without pyrolysis and the
absence of catalyst or base resulted in no product formation
(entries 1, 7 and 8). Further, inspired by the excellent catalytic
performance of Co/N–SiO2–AC pyrolyzed at 800 oC (entry 6), we
further prepared the Cu-, Mn-, Pd- and Fe-catalyst materials.
However, they showed no activity under the identical conditions
(entries 9–12). Hence, the optimal reaction system is as shown in
entry 6 of Table 1.
Characterization of Co/N–SiO2–AC was performed by XRD, BET,
TEM, XPS, EDX and ICP-OES, respectively. The XRD pattern (Fig. S1,
ESI†) showed no peaks ascribing to the Co metal. Except for two
peaks of carbon at 26o and 43o, which are denoted to the (002) and
(100) planes, the diffraction pattern of graphite-like carbon
structure.20 However, the existence of cobalt was confirmed by EDX
detection (Fig. S2, ESI†) and the transmission electron microscopy
(TEM, Fig. S3, ESI†). These results indicate that the cobalt particles
are highly dispersed with low density and small size. In comparison
with Co/N–AC, Co/N–SiO2–AC has a regular morphology although
both samples have highly dispersed metal particles (Fig. S3, ESI†).
The mean size of the Co particles in Co/N–SiO2–AC was measured as
0.52 nm by TEM (Fig. S4, ESI†). In addition, the element mapping
images reveal the uniform distribution of Co, N, Si and C (Fig. 1),
which is in accordance with the result of EDX (Fig. S2, ESI†).
The specific surface area of Co/N–SiO2–AC detected by the
Brunauer-Emmett-Teller (BET) is 566.2 m2g-1 (Table S2, ESI†), and
Co/N–SiO2–AC mainly contains mesopores with a total pore volume
Table 1 Optimization of reaction conditionsa
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of 0.69 cm3g-1 and an average pore width of 4.9 nm, whereas the substrates such as furan-3-thiol 1r and thiophene-2-thiol 1s were
Co/N–AC mainly has micropores with a total pore volume of 0.33 also amenable to the transformation to afford the desired products
cm3g-1 and a mean pore width of 1.9 nm, the totally different in good yields (3ra, 3sa). Moreover, the alkyl thiol 1t was able to
material parameters reflect the capability of the doped SiO2 in undergo smooth oxidative esterification to couple with methanol,
modification of the catalyst structure and change of the catalytic affording the methyl hexane-1-sulfinate 3ta in a moderate yield
performance. Further, the cobalt content of the Co/N–SiO2–AC was (45%). Further, the change of methanol to ethanol, propyl alcohol,
detected as 1.08 wt % by means of ICP-OES analysis.
butyl alcohol, isopropanol and benzyl alcohol also led to the
generation of desired sulfinic ester products at slightly elevated
temperature (3ab, 3gb, 3ac, 3ad, 3ae and 3ef). It is worth
mentioning that a variety of functional groups such as –Me, –OMe,
–t-Bu, –F, –Cl, –Br, –CF3, –NH2 and MeCONH– are well tolerated in
the transformation, which would offer the potential for molecular
complexity via further transformations.
Subsequently, X-ray photoelectron spectroscopy (XPS) analysis
was employed to identify the surface chemistry of the developed
Co/N–SiO2–AC and Co/N–AC, the Co2p spectra of both catalysts
show three peaks with the electron binding energies of 778.2,
780.0 and 782.2 eV, which are assigned to Co, CoOx and Co-N,
respectively. The content of Co-N and CoOx in Co/N-SiO2-AC is
63.7% and 13.8%, respectively, while 39.1% of Co-N and 54.3% of
CoOx were found in Co/N–AC (Figure 2 and Table 2), implying that
the Co-N serves as the catalytic active ingredient (Table 1, entries 2
and 6). In the N region of Co/N–SiO2–AC, there are three distinct
peaks (Figure S5, ESI†) with electron binding energies of 398.9
(pyridine-type), 400.7 (pyrrole-type) and 402.2 eV (ammonia N),
and the pyridine-type nitrogen in this case is bonded to the cobalt,
while the pyrrole-type N originates from the calcination of the 1,10-
phenanthroline. Deconvolution shows that around 43.9% of the N
atoms are bonded to the cobalt metal (see Table S3, Co–N, ESI†),
which derives from the graphitization of the Co-Phen complex.21
O
Co/N-SiO2-AC
60-80 oC, O2, K2CO3, 24 h
S
RSH
R'OH
R
OR'
2
1
3
O
O
O
S
O
S
S
S
OMe
OMe
OMe
OMe
3aa, 91%
3ba, 85%
3ca, 75%
3da, 80%
O
S
O
S
O
S
O
S
OMe
OMe
OMe
OMe
OMe
Ph
OMe
MeO
t-Bu
3ea, 87%
3ga, 88%
3fa, 85%
3ha, 83%
O
S
O
S
O
O
S
S
OMe
OMe
OMe
Cl
Cl
67%
F
Br
3ia, 82%
3ja, 75%
3ka,
3la,
3pa,
3ta,
83%
O
S
O
S
O
O
Cl
S
S
OMe
OMe
OMe
H2N
F3C
Fig. 2 Co2p XPS spectra of the Co/N–SiO2–AC (left) and Co/N–AC (right).
Table 2 The binding energy and content of Co in the catalysts
Cl
3ma,
Cl
60%
75%
3oa,
3na,
70%
80%
O
O
S
O
S
S
O
S
OMe
OMe
O
OMe
S
Binding Energy / eV (Area/%)
Sample
OMe
N
H
3qa,
Co
CoOx
780.2
(54.3)
780.0
(13.8)
Co–N
781.8
(39.1)
782.2
(63.7)
Satellites
O
3ra,
3sa,
81%
70%
O
90%
45%
778.2
(6.5)
778.2
(3.6)
Co/N
–AC
-
O
O
S
O
S
S
786.8
(18.8)
OEt
Co/N SiO2
–
–AC
O
OEt
d
b
(3gb, 80%)c
(
85%)
(3ab, 89%)b
3ac,
With the developed Co/N–SiO2–AC catalyst in hand, a series of
structurally diverse thiols 1 with different alcohols 2 were employed
to investigate the generality of the esterification protocol under the
optimal conditions. Initially, the reactions of a series of (hetero)aryl
thiols with methanol were tested. Gratifyingly, all the reactions
proceeded smoothly and furnished the desired sulfinic esters in
good to excellent yields upon isolation (Scheme 3, 3aa-3sa). The
substituents on the aryl ring of aryl thiols influenced the product
yields to some extent. In general, substrates 1 bearing an electron-
donating group (3aa-3ha) are able to afford relatively higher yields
than those of electron-deficient ones (3la, 3na, 3oa and 3pa). This
phenomenon is rationalized as the electron-rich aryl thiols are
beneficial to form more stable radical intermediates, thus favoring
the coupling process.15 Interestingly, the less-reactive heterocyclic
O
O
O
S
S
S
O
O
O
(3ad, 83%)d
(3ae, 75%)d
3ef,
(
67%)
Scheme 3 Oxidative esterification of thiols.a a Standard conditions: unless
otherwise stated, the reaction of 1 (0.5 mmol), 2 (1.5 mL), catalyst (40 mg,
1.46 mol %), K2CO3 (0.1 mmol) was stirred at 60 oC for 24 h under O2. b At 80
oC. c At 70 oC. d At refluxing temperature.
To check the stability of the developed catalyst material (Co/N–
SiO2–AC), it was recycled and reused for six consecutive runs with
the model reaction. As illustrated in Fig. 3, the catalytic activity
maintains very well. After six recycles, the ICP-OES analysis showed
only a slight decrease of Co content from 1.08 wt % to 1.05 wt %.
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afforded via K2CO3–promoted necleophilic substitution of 1-2 by the
high concentration of alcohol 2 (solvent).
Meanwhile, a slight decrease of the specific surface area, pore
volume and width of the Co/N–SiO2–AC was found, which still
belongs to mesopore structure and causes no obvious decrease in
catalytic activity (Table S2, ESI†).
100
90
80
70
60
50
40
30
20
10
0
Scheme 5 The possible reaction pathway.
Conclusions
0
1
2
3
4
5
6
In conclusion, by developing a cobalt nanocatalyst supported
Recycle time
on N–SiO2-doped activated carbon, which exhibits excellent
Fig. 3 The reusability of the Co-N-SiO2/AC catalyst.
catalytic performance towards the oxidative esterification of
aryl, heteroaryl and alkyl thiols with alcohols. A wide array of
sulfinic esters were efficiently afforded in an exclusive
chemoselective manner. The developed synthetic protocol
proceeds with the merits of mild reaction conditions, broad
substrate scope, operational simplicity, good functional group
tolerance, high atom-efficiency earth-abundant and reusable
cobalt catalyst, the utilization of renewable alcohols as the
coupling partners and molecular O2 as the sole oxidant, which
offers a practical way for sustainable synthesis of sulfinic
esters.
To gain insight into the mechanistic information, the model
reaction under standard conditions was terminated after 1 h to
analyze the product system. 3aa was detected in 8% yield along
with diaryl disulfide 1a-1 and thiosulfinate 1a-2 in 91% and 1%
yields, respectively (Scheme 4, eq 1). Then, the prepared 1a-1 and
1a-2 were able to couple with alcohol 2a to give product 3aa in
excellent yields (eq 2 and 3), showing that both diaryl disulfide 1a-1
and thiosulfinate 1a-2 serve as the key reaction intermediates.
Further, addition of excess TEMPO into the reaction significantly
suppressed the product formation (eq 4), reaveling that the
reaction involves a radical mechanism.
Experimental
General information
All the obtained products were characterized by melting points
1
(m.p), H-NMR, 13C-NMR and infrared spectra (IR). Melting points
were measured on an Electrothermal SGW-X4 microscopy digital
melting point apparatus and are uncorrected; IR spectra were
recorded on a FTLA2000 spectrometer; 1H-NMR and 13C-NMR
spectra were obtained on Bruker-400 and referenced to 7.27 ppm
for chloroform solvent with TMS as internal standard (0 ppm).
Chemical shifts were reported in parts per million (ppm, δ)
downfield from tetramethylsilane. Proton coupling patterns are
described as singlet (s), doublet (d), triplet (t), multiplet (m); TLC
was performed using commercially available 100–400 mesh silica
gel plates (GF254), and visualization was effected at 254 nm; Unless
otherwise stated, all the reagents were purchased from commercial
sources (J&K Chemic, TCI, Fluka, Acros, SCRC) and used without
further purification.
Scheme 4 The control experiments.
On the basis of the above findings, a possible reaction pathway is
depicted in Scheme 5. The active Co-N sites of the catalyst Co/N–
SiO2–AC (simplified as [Co-N]) captures the molecular oxygen under
the assistance of the doped nitrogen, the single electron
oxidation[17a] of thiol 1 by [Co-N]/O2 initially forms species A and
the thiol radical 1‘. Then, another single electron oxidation of thiol 1
by A also gives radical 1‘ and regenerates the catalytic species. The
homo-coupling of 1‘ forms the disulfide 1-1 in situ. Further, the
oxidation of 1-1 by [Co-N]/O2 results in species B and its tautomer
C,[15] and the interaction between C and radical 1‘ would lead to
generation of thiosulfinate 1-2. Finally, the desired sulfinic ester 3 is
X-ray diffraction (XRD) was used for crystal structure
identification by a Bruker D8 advanced X-ray diffractometer.
Micromeritics ASAP 2020 was employed to measure the specific
surface area and pore structure (BET) by N2 adsorption.
Transmission electron microscopy (TEM) and Energy Dispersive X-
ray spectroscopy (EDX) by a Tecnai-G20 were used to detect the
morphology of the samples. The atomic emission spectrometry
(ICP) was used to analyse the metal content. And the electronic
states were measured by X-ray photoelectron spectroscopy (XPS)
4 | J. Name., 2012, 00, 1-3
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3
4
5
6
J. A. Lujan-Montelongo, A. O. Estevez and F. F. Fleming, Eur.
J. Org. Chem., 2015, 1602.
using a K-Alpha spectrometer with a monochromatized Al-Kα X-ray
source (300W).
J. E. Resek and A. I. Meyers, Tetrahedron Lett., 1995, 36
7051.
,
Catalyst Preparation
F. Yuste, J. García Ruano, A. Parra and V. Mastranzo,
Synthesis, 2008, 311.
M. Funes Maldonado, F. Sehgelmeble, F. Bjarnemark, M.
Svensson, J. Åhman and P. I. Arvidsson, Tetrahedron, 2012,
68, 7456.
(a) F. Yuste, A. H. Linares, V. M. Mastranzo, B. Ortiz, R.
Sanchez-Obregon, A. Fraile and J. L. Ruano, J. Org. Chem.,
2011, 76, 4635; (b) N. T. Nguyen, H. T. Vo, F. Duus and T. X. T.
Luu, Molecules, 2017, 22, 1458; (c) M. E. Jung and T. I.
Lazarova, Tetrahedron Lett., 1996, 37, 7.
Initially, a mixture of Co(OAc)2·4H2O and 1,10-phenanthroline was
added to ethanol and stirred for 1 hour at 100 oC to in situ generate
the cobalt complex. Then, Si(OC2H5)4 was added into the above
solution and followed by hydrolysis of TEOS with aq. ammonia to in
situ form the silica. After refluxing for 2 hours, the activated carbon
as the support was poured into the solvent and refluxed for another
5 h. After cooling down to room temperature, the solvent of the
suspension was removed under vacuum and the remained solid was
dried overnight. Then, the powdered sample was pyrolyzed at 800
oC under a constant argon atmosphere for 2 h. Subsequently, the
cooled sample was treated with HCl solution to selectively remove
the unsupported cobalt particles generated during the pyrolysis
process, and the remaining catalyst is named as Co–N–SiO2/AC (Co
content: 1.08 wt % detected by ICP-OES). Similarly, the other
prepared metal catalysts are denoted as Metal–N–SiO2/AC.
Moreover, without addition of Si precursor, 1,10-phenanthroline or
metal source, the resulting materials were donated as Co–N/AC,
Co–SiO2/AC and N–SiO2/AC, respectively.
7
8
9
R. R. Tata, C. S. Hampton and M. Harmata, Adv. Synth.
Catal., 2017, 359, 1232.
(a) P. Brownbridge and I. C. Jowett, Synthesis, 1988, 252; (b)
M. Xia and Z. C. Chen, Synth. Commun., 1997, 27, 1321.
10 I. Fermindev. N. Khtar, A. Roca, A. Benabra, A. AIcudia, J. L.
Esparlero and F. AIcudia, Tetrahedron Lett., 1999, 40, 2029.
11 A. R. Hajipour, A. R. Falahati and A. E. Ruoho, Tetrahedron
Lett., 2006, 47, 2717.
12 J. Wei and Z. Sun, Org Lett., 2015, 17, 5396.
13 A. Tranquilino, S. R. C. P. Andrade, A. P. M. da Silva, P. H.
Menezes and R. A. Oliveira, Tetrahedron Lett., 2017, 58
1265.
,
14 B. Du, Z. Li, P. Qian, J. Han and Y. Pan, Chem. Asian J., 2016,
11, 478.
15 P. K. Shyam, Y. K. Kim, C. Lee and H. Y. Jang, Adv. Synth.
Catal., 2016, 358, 56.
Typical procedure for the synthesis of sulfinic ester 3aa
The mixture of 4-methylbenzenethiol 1a (0.5 mmol), methanol 2a
(1.5 mL), K2CO3 (0.1 mmol) and Co–N–SiO2/AC (40 mg, 1.46 mol %
Co) were successively added into a 25 mL Schlenk tube, then stirred
at 60 oC for 24 h under O2 atmosphere. The resulting mixture was
filtered and washed with ethyl acetate, and then concentrated by
removing the solvent under vacuum. Finally the residue was
purified by preparative TLC on silica, eluting with petroleum ether
(60 – 90 oC) : ethyl acetate (20 : 1) to give the product.
16 (a) B. Xiong, J. Jiang, S. Zhang, H. Jiang, Z. Ke and M. Zhang,
Org. Lett., 2017, 19, 2730; (b) S. Zhang, Z. Tan, B. Xiong, H. F.
Jiang and M. Zhang, Org. Biomol. Chem., 2018, 16, 531; (c)
W. Lv, B. Xiong, H. Jiang and M. Zhang, Adv. Synth. Catal.,
2017, 359, 1202; (d) B. Xiong, S. Zhang, H. Jiang and M.
Zhang, Org. Lett., 2016, 18, 724; (e) B. Xiong, S. D. Zhang, L.
Chen, B. Li, H. F. Jiang and M. Zhang, Chem. Commun., 2016,
52, 10636; (f) B. Xiong, Y. Li, W. Lv, Z. Tan, H. Jiang and M.
Zhang, Org. Lett., 2015, 17, 4054; (g) F. Xie, M. Zhang, H.
Jiang, M. Chen, W. Lv, A. Zheng and X. Jian, Green Chem.,
2015, 17, 279; (h) F. Xie, M. Zhang, M. Chen, W. Lv and H.
Conflicts of interest
Jiang, ChemCatChem, 2015,
17 (a) T. Liang, Z. Tan, H. Zhao, X. Chen, H. Jiang and M. Zhang,
ACS Catal., 2018, , 2242; (b) X. Chen, H. Zhao, C. Chen, H.
7, 349.
There are no conflicts to declare.
8
Jiang and M. Zhang, Org. Lett., 2018, 20, 1171; (c) X. Chen, H.
Zhao, C. Chen, H. Jiang, M. Zhang, Angew. Chem., Int. Ed.,
2017, 56, 14232; (d) F. Xie, R. Xie, J. X. Zhang, H. F. Jiang, L.
Acknowledgements
Du and M. Zhang, ACS Catal., 2017, 7, 4780; (e) Z. Tan, H.
We thank State Key Laboratory of Pulp and Paper Engineering
(2017TS02), Science Foundation for Distinguished Young
Scholars of Guangdong Province (2014A030306018), the
National Natural Science Foundation of China (21472052), the
Fundamental Research Funds for the Central Universities
(2017ZD060) and “1000-Youth Talents Plan” for financial
support.
Jiang and M. Zhang, Chem. Commun., 2016, 52, 9359.
18 (a) Z. Li, A. W. Peters, A. E. Platero-Prats, J. Liu, C. W. Kung, H.
Noh, M. R. DeStefano, N. M. Schweitzer, K. W. Chapman, J. T.
Hupp and O. K. Farha, J. Am. Chem. Soc., 2017, 139, 15251;
(b) K. H. He, F. F. Tan, C. Z. Zhou, G. J. Zhou, X. L. Yang and Y.
Li, Angew. Chem., Int. Ed., 2017, 56, 3080; c) R. Xu, S.
Chakraborty, H. Yuan and W. D. Jones, ACS Catal., 2015, 5,
6350.
19 Selected examples, see: (a) D. Forberg, T. Schwob, M.
Zaheer, M. Friedrich, N Miyajima and R. Kempe, Nat.
Notes and references
Commun., 2016, , 13201; (b) S. M. Sachau, M. Zaheer, A.
7
Lale, M. Friedrich, C. E. Denner, U. B. Demirci, S. Bernard, G.
Motz and R. Kempe, Chem. Eur. J., 2016, 22, 15508; (c) G.
Hahn, J. K. Ewert, C. Denner, D. Tilgner and R. Kempe,
1
(a) J. H. Kim, J. O. Lee, S. K. Lee, J. W. Moon, G. Y. You, S. J.
Kim, S. H. Park, J. M. Park, S. Y. Lim, P. G. Suh, K. O. Uhm, M.
S. Song and H. S. Kim, J. Biol. Chem., 2011, 286, 7567; (b) J.
Blackinton, M. Lakshminarasimhan, K. J. Thomas, R. Ahmad,
E. Greggio, A. S. Raza, M. R. Cookson and M. A. Wilson, J.
Biol. Chem., 2009, 284, 6476.
ChemCatChem, 2016, 8, 2461.
20 D. Deng, L. Yu, X. Chen, G. Wang, L. Jin, X. Pan, J. Deng, G.
Sun and X. Bao, Angew. Chem., Int. Ed., 2013, 52, 371.
21 M. Lefevre, E. Proietti, F. Jaouen and J. P. Dodelet, Science,
2009, 324, 71.
2
A. Tapia-Pineda, C. Perez-Arrieta, C. Silva-Cuevas, E. Paleo
and J. A. Lujan-Montelongo, J. Chem. Edu., 2016, 93, 1470.
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Green Chemistry
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DOI: 10.1039/C8GC00441B
ARTICLE
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Green Chemistry
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DOI: 10.1039/C8GC00441B
By developing new cobalt nanocatalyst supported on N-SiO2-doped activated carbon
(Co/N–SiO2–AC), which exhibits excellent catalytic performance towards the
oxidative esterification of (hetero)aryl and alkyl thiols with alcohols. A wide array of
sulfinic esters were efficiently afforded in an exclusive chemoselective manner
together with merits of mild reaction conditions, broad substrate scope, operational
simplicity, good functional group tolerance, earth-abundant and reusable cobalt
catalysts, the utilization of renewable alcohols as the coupling partners and molecular
O2 as the sole oxidant.