Silver-mediated decarboxylative C-S cross-coupling of aliphatic carboxylic acids under mild conditions

Article abstract of DOI:10.1021/ol502144c

A silver-mediated decarboxylative C-S cross-coupling reaction of aliphatic carboxylic acid is described. This reaction occurs smoothly under mild conditions and shows good tolerance of functional groups. It provides an alternative approach for the synthesis of alkyl aryl sulfides.

Full text of DOI:10.1021/ol502144c

Letter
pubs.acs.org/OrgLett
Silver-Mediated Decarboxylative C−S Cross-Coupling of Aliphatic
Carboxylic Acids under Mild Conditions
Peng-Fei Wang,† Xiao-Qing Wang,† Jian-Jun Dai,† Yi-Si Feng,*,†,‡ and Hua-Jian Xu*,†
†School of Chemistry and Chemical Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009, P. R.
China
‡Anhui Key Laboratory of Controllable Chemical Reaction & Material Chemical Engineering, Hefei 230009, P. R. China, and
Anhui Provincial Laboratory of Heterocyclic Chemistry, Maanshan 243110, P. R. China
S
* Supporting Information
ABSTRACT: A silver-mediated decarboxylative C−S cross-
coupling reaction of aliphatic carboxylic acid is described. This
reaction occurs smoothly under mild conditions and shows
good tolerance of functional groups. It provides an alternative
approach for the synthesis of alkyl aryl sulfides.
Scheme 1. Decarboxylative C−S Coupling Reactions
rganic molecules containing C−S bonds widely exist in
1,2
Omany biologically active compounds.
They are also
frequently used as building blocks of many functional polymer
materials.3 Although the methods for C−N4 and C−O5 bonds
formation receive extensive attention in the field of traditional
metal-catalyzed cross-couplings, efficient construction of a C−S
bond through transition-metal catalysis still needs more studies.
Recent progress has been made in C−S cross-couplings
catalyzed by Pd,6 Cu,7 and Ni,2d,8 but many of these methods
depend on harsh reaction conditions such as high reaction
temperature, the necessity of strong base, and use of expensive
ligand, and they suffer from limited substrate scope. Moreover,
catalyst poisoning by the sulfide is one of the limiting factors in
these approaches. Consequently, it remains important to
explore new approaches for efficient construction of the C−S
bonds.
In recent years, a new method for the C−S bond formation
has emerged that relies on decarboxylative C−S couplings of
aryl carboxylic acids.9 For instance, Liu et al. developed a
method to synthesize aryl sulfides by decarboxylative C−S
cross-coupling of aryl carboxylic acids and thiols (Scheme 1, eq
1).9a More recently, they developed a synthesis of vinyl sulfides
by the decarboxylative cross-coupling of arylpropiolic acids with
thiols using copper(I) salts as catalysts (Scheme 1, eq 2).9b
Afterward, Becht et al. reported a simple route to diaryl sulfides
using a decarboxylative palladium-catalyzed reaction between
electron-rich 2,6-dialkoxybenzoic acid derivatives and diaryl
disulfides (Scheme 1, eq 3).9c In 2012, Li et al. reported the
silver-catalyzed decarboxylative chlorination, fluorination, and
alkynylation of aliphatic carboxylic acids under mild reaction
conditions.10 These studies greatly promoted the chemistry of
decarboxylative coupling.11 The related decarboxylative reac-
tions involving the cleavage of C(sp3)−COOH bonds were
reported by others12,13 and our group.14 Such reactions are
synthetically useful for preparing aliphatic compounds and
therefore need more studies. Moreover, aliphatic carboxylic
acids are cheap and available substrates. Herein, we reported a
silver-mediated decarboxylative C−S cross-coupling reaction of
aliphatic carboxylic acids (Scheme 1, eq 4).
We began our investigation by exploring the reaction
between 1,4-benzodioxane-2-carboxylic acid (1e) and diphenyl
disulfide (II) (Table 1). Unfortunately, no desired product
could be obtained in different solvents such as THF, CH3CN,
CH2Cl2, H2O, CH2Cl2/H2O, and acetone/H2O at 50 °C in the
presence of AgNO3 (30 mol %) and 3 equiv of K2S2O8 (the
results are not shown in Table 1). We were delighted to find
that when CH3CN/H2O was used as the solvent, the desired
product 3e was obtained in 49% yield at 50 °C under an argon
atmosphere (entry 1). Then various silver salts such as Ag2CO3,
AgBF4, AgOAc, AgOTf were further examined. It turned out
that less than 44% yield of 3e was detected (entries 2−5). With
regard to the influence of reaction temperature, it was found
that the yield of 3e increased to 54% at 60 °C, whereas the yield
Received: July 21, 2014
© XXXX American Chemical Society
A
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Organic Letters
Letter
a
a,b
Table 1. Optimization of the Reaction Conditions
Scheme 2. Scope of Aliphatic Carboxylic Acids
b
oxidant
(equiv)
temp
(°C)
time
(h)
yield
entry catalyst (equiv)
(%)
1
AgNO3 (0.3)
Ag2CO3 (0.3)
AgBF4 (0.3)
AgOAc (0.3)
K2S2O8 (3)
K2S2O8 (3)
K2S2O8 (3)
K2S2O8 (3)
K2S2O8(3)
K2S2O8 (3)
K2S2O8 (3)
K2S2O8 (3)
K2S2O8 (3)
K2S2O8(3)
K2S2O8 (3)
K2S2O8 (2)
K2S2O8 (4)
K2S2O8 (3)
K2S2O8 (3)
K2S2O8 (3)
50
50
50
50
50
60
70
60
60
60
60
60
60
60
60
60
60
60
60
24
24
24
24
24
24
24
24
24
24
24
24
24
18
30
24
24
24
24
49
41
37
43
34
54
52
60
69
79
78
70
75
67
74
77
2
3
4
e
5
AgOTf (0.3)
6
AgNO3 (0.3)
AgNO3 (0.3)
AgNO3 (0.5)
AgNO3 (0.8)
AgNO3 (1)
AgNO3 (1.2)
AgNO3 (1)
AgNO3 (1)
AgNO3 (1)
AgNO3 (1)
AgNO3 (1)
AgNO3 (1)
7
8
9
10
11
12
13
14
15
c
16
17
18
19
K2S2O8 (3)
AgNO3 (1)
d
AgNO3 (1)
77
a
Unless otherwise stated, all reactions were carried out with 1e (0.25
mmol), II (1.5 equiv), and MeCN/H2O (1:1, 2 mL) under an argon
b
c
atmosphere. Isolated yields based on 1e. The amount of diphenyl
a
Reaction conditions: 1 (0.25 mmol), 2 (1.5 equiv), AgNO3 (1 equiv),
d
disulfide was increased to 2.5 equiv. SDS (20 mol %) was added to
the reaction (SDS = sodium dodecyl sulfate). AgOTf = silver
b
K2S2O8 (3 equiv), CH3CN/H2O (1:1, 2 mL), 60 °C, 24 h. Isolated
e
yield based on 1.
trifluoromethanesulfonate.
had a slight reduction when the reaction was conducted at 70
°C (entries 6 and 7). By changing the amount of AgNO3, we
further improved the yield of 3e to 79% (entries 8−11).
Furthermore, the amount of K2S2O8, diphenyl disulfide, and
reaction time were investigated, but an elevated yield was not
obtained (entries 12−16). It should be mentioned that no
product was detected when the reaction was performed in the
absence of AgNO3 or K2S2O8 (entries 17−18). The results
proved that both AgNO3 and K2S2O8 were essential for the
reaction. While our study was in progress, Shen et al. reported
silver-catalyzed decarboxylative trifluoromethylthiolation of
aliphatic carboxylic acids in aqueous emulsion.15 Inspired by
their works, we also tried to add SDS to our reaction, but it
failed to improve the reaction (entry 19).
With the optimal reaction conditions in hand, we then
explored the scope of this method with various aliphatic
carboxylic acids (Scheme 2). It was found that various aliphatic
carboxylic acids could successfully decarboxylate to give the
desired products in modest to good yields. For example, the
reactions of 1,4-benzodioxane-2-carboxylic acid (1e) achieved
the desired products in good yields (3e,g,h), whereas modest
yields were obtained when 1,2-di(pyridin-2-yl)disulfane and
1,2-bis(4-chlorophenyl)disulfane were used to react with the
acid (3f,j). Tertiary alkyl carboxylic acids underwent decarbox-
ylation to give alkyl aryl sulfides in modest to good yields (3a−
c). Other secondary alkyl acids were employed as the substrates
to produce the corresponding products in 40% yield (3d,i). It
should be noted that primary aliphatic carboxylic acids could
also undergo decarboxylation to generate the desired products
in yields of 28−70% (3k−n). Using 2-(phenylthio)acetic acid
as a coupling partner could give low yields of 34% and 28%,
respectively (3k,l).
The lower yields indicated that the reactivity of primary
aliphatic carboxylic acids was very low. On the other hand,
aromatic acids such as 4-methylbenzoic acid under the above
conditions failed to produce the expected product (3o).
Under the optimal conditions, we further explored the scope
of diaryl disulfides (Scheme 3). Both the electron-rich and
-deficient diaryl disulfides gave the desired products in modest
to good yields (3aa−aj). The diaryl disulfide bearing an ortho-
substitutent also worked well to produce the desired product
(3ag). It should be pointed out that the reaction was
compatible with heterocyclic aromatic disulfides, such as
thiophene and pyridine (3ah,ai). It is interesting to note that
the corresponding product was obtained in 31% yield when
benzyl disulfide, a dialkyl disulfide, was used as a substrate
(3aj). However, the reaction did not tolerate an unprotected
amino group (3ak).
Next, we conducted a gram-scale experiment using 1,4-
benzodioxane-2-carboxylic acid and 2-thienyl disulfide as the
substrates. We found that the corresponding alkyl aryl sulfide
was obtained in 68% yield (Scheme 4). Stoichimetric silver
nitrate was used in the reaction, whereas a catalytic amount of
silver nitrate was used for decarboxylation of aliphatic
carboxylic acids according to previous reports.10 Thus, we
studied the possible reason for using stoichimetric silver nitrate.
We isolated the main byproducts in some reactions, and it was
found that diaryl disulfides were oxidized into the arylthiosul-
fonates in the presence of silver nitrate through NMR and
HRMS analysis. When 1-adamantanecarboxylic acid (1a) and
B
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Letter
a,
b
a
Scheme 3. Scope of Diaryl Disulfides
Scheme 5. Study on the Side Reactions
a
Isolated yield of 3ab based on 1a and isolated yield of 4b based on
2b.
Scheme 6. Proposed Reaction Mechanism
a
Reaction conditions: 1a (0.25 mmol), 2 (1.5 equiv), AgNO3 (1
equiv), K2S2O8 (3 equiv), CH3CN/H2O (1:1, 2 mL), 60 °C, 24 h.
b
Isolated yield based on 1a.
Scheme 4. Gram-Scale Reaction
could be performed under mild reaction conditions. Fur-
thermore, the reaction provided a new approach to the
synthesis of alkyl aryl sulfides.
ASSOCIATED CONTENT
* Supporting Information
Detailed experimental procedures and spectra data for all
compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
1,2-bis(4-methoxyphenyl)disulfane (2b) were used as the
substrates, the corresponding product (3ab) was obtained in
71% yield. In this case, we also isolated the main byproduct, S-
(4-methoxyphenyl)-4-methoxybenzensulfinothioate (4b) in
59% yield (Scheme 5a). The results indicated that silver nitrate
was not only used for the decarboxylation of aliphatic
carboxylic acids but also used for oxidation of diaryl disulfides
to arylthiosulfonates, and thus, it helped to explain the possible
reason for using stoichimetric silver nitrate. To explore whether
the side products could react with aliphatic carboxylic acids to
produce the same thiolation products, another experiment was
carried out by using 1a and 4b as coupling partners. It was
found that alkyl aryl sulfide 3ab was obtained in 12% yield
(Scheme 5b).
■
S
AUTHOR INFORMATION
Corresponding Authors
■
*E-mail: fengyisi2008@126.com.
*E-mail: hjxu@hfut.edu.cn.
Notes
The authors declare no competing financial interest.
According to the previous studies,10,16 we proposed that the
reaction may proceed through the mechanism presented in
Scheme 6. First, Ag(I) is oxidized to Ag(II) in the presence of
persulfate, and subsequently, Ag(II) combines with aliphatic
carboxylic acid to produce the alkyl radical via decarboxylation
pathway. Then, the alkyl radical attacks diaryl disulfide to
generate the desired product.
ACKNOWLEDGMENTS
■
We gratefully acknowledge financial support from the National
Natural Science Foundation of China (No. 21371044,
21272050) and the Program for New Century Excellent
Talents in University of the Chinese Ministry of Education
(NCET-11-0627).
In conclusion, we developed a silver-mediated decarbox-
ylative C−S cross-coupling reaction of aliphatic carboxylic acids
using K2S2O8 as the oxidant and diaryl disulfides as the sulfur
source. The new reaction tolerated many functional groups and
REFERENCES
■
(1) (a) Liu, G.; Link, J. T.; Pei, Z.; Reilly, E. B.; Leitza, S.; Nguyen,
B.; Marsh, K. C.; Okasinski, G. F.; von Geldern, T. W.; Ormes, M.;
Fowler, K.; Gallatin, M. J. Med. Chem. 2000, 43, 4025. (b) Liu, G.;
C
dx.doi.org/10.1021/ol502144c | Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Huth, J. R.; Olejniczak, E. T.; Mendoza, R.; DeVries, P.; Leitza, S.;
Reilly, E. B.; Okasinski, G. F.; Fesik, S. W.; von Geldern, T. W. J. Med.
Chem. 2001, 44, 1202. (c) Babu, S. G.; Karvembu, R. Tetrahedron Lett.
2013, 54, 1677.
(14) (a) Feng, Y.-S.; Wu, W.; Xu, Z.-Q.; Li, Y.; Li, M.; Xu, H.-J.
Tetrahedron. 2012, 68, 2113. (b) Feng, Y.-S.; Xu, Z.-Q.; Mao, L.;
Zhang, F.-F.; Xu, H.-J. Org. Lett. 2013, 15, 1472.
(15) Hu, F.; Shao, X.; Zhu, D.; Lu, L.; Shen, Q. Angew. Chem., Int. Ed.
2014, 53, 6105.
(2) (a) McReynolds, M. D.; Dougherty, J. M.; Hanson, P. R. Chem.
Rev. 2004, 104, 2239. (b) Marcantoni, E.; Massaccesi, M.; Petrini, M.;
Bartoli, G.; Bellucci, M. C.; Bosco, M.; Sambri, L. J. Org. Chem. 2000,
65, 4553. (c) D’Angelo, N. D.; Kim, T.-S.; Andrews, K.; Booker, S. K.;
Caenepeel, S.; Chen, K.; D’Amico, D.; Freeman, D.; Jiang, J.; Liu, L.;
McCarter, J. D.; Miguel, T. S.; Mullady, E. L.; Schrag, M.;
Subramanian, R.; Tang, J.; Wahl, R. C.; Wang, L.; Whittington, D.
A.; Wu, T.; Xi, N.; Xu, Y.; Yakowec, P.; Yang, K.; Zalameda, L. P.;
Zhang, N.; Hughes, P.; Norman, M. H. J. Med. Chem. 2011, 54, 1789.
(d) Xu, X.-B.; Liu, J.; Zhang, J.-J.; Wang, Y.-W.; Peng, Y. Org. Lett.
2013, 15, 550.
(16) (a) Guo, S.-R.; Yuan, Y.-Q.; Xiang, J.-N. Org. Lett. 2013, 15,
4654. (b) Du, B.; Jin, B.; Sun, P. Org. Lett. 2014, 16, 3032.
(3) (a) Yamaguchi, H.; Minoura, Y. J. Appl. Polym. Sci. 2003, 15,
1869. (b) Beletskaya, I. P.; Ananikov, V. P. Chem. Rev. 2011, 111,
1596.
(4) (a) Shin, K.; Ryu, J.; Chang, S. Org. Lett. 2014, 16, 2022.
(b) Creutz, S. E.; Lotito, K. J.; Fu, G. C.; Peters, J. C. Science 2012,
338, 647. (c) Bissember, A. C.; Lundgren, R. J.; Creutz, S. E.; Peters, J.
C.; Fu, G. C. Angew. Chem., Int. Ed. 2013, 52, 5129. (d) Guo, S.; Qian,
B.; Xie, Y.; Xia, C.; Huang, H. Org. Lett. 2011, 13, 522.
(5) (a) Xiao, B.; Gong, T.-J.; Liu, Z.-J.; Liu, J.-H.; Luo, D.-F.; Xu, J.;
Liu, L. J. Am. Chem. Soc. 2011, 133, 9250. (b) Wang, X.; Lu, Y.; Dai,
H.-X.; Yu, J. Q. J. Am. Chem. Soc. 2010, 132, 12203. (c) Modak, A.;
Dutta, D.; Kancherla, R.; Maity, R.; Bhadra, M.; Mobin, S. M.; Maiti,
D. Org. Lett. 2014, 16, 2602. (d) Liang, Z.; Hou, W.; Du, Y.; Zhang, Y.;
Pan, Y.; Mao, D.; Zhao, K. Org. Lett. 2009, 11, 4978.
(6) (a) Alvaro, E.; Hartwig, J. F. J. Am. Chem. Soc. 2009, 131, 7858.
(b) Itoh, T.; Mase, T. Org. Lett. 2004, 6, 4587. (c) Lee, J.-Y.; Lee, P. H.
J. Org. Chem. 2008, 73, 7413.
(7) (a) Bates, C. G.; Gujadhur, R. K.; Venkataraman, D. Org. Lett.
2002, 4, 2803. (b) Deng, W.; Zou, Y.; Wang, Z.-F.; Liu, L.; Guo, Q.-X.
Synlett 2004, 1254. (c) Xu, H.-J.; Zhao, X.-Y.; Deng, J.; Fu, Y.; Feng,
Y.-S. Tetrahedron Lett. 2009, 50, 434. (d) Feng, Y.-S.; Li, Y.-Y.; Tang,
L.; Wu, W.; Xu, H.-J. Tetrahedron Lett. 2010, 51, 2489. (e) Feng, Y.-S.;
Qi, H.-X.; Wang, W.-C.; Liang, Y.-F.; Xu, H.-J. Tetrahedron Lett. 2012,
53, 2914. (f) Xu, H.-J.; Zhao, Y.-Q.; Feng, T.; Feng, Y.-S. J. Org. Chem.
2012, 77, 2878. (g) Wu, Z.; Song, H.; Cui, X.; Pi, C.; Du, W.; Wu, Y.
Org. Lett. 2013, 15, 1270. (h) Kabir, M. S.; Lorenz, M.; van Linn, M.
L.; Namjoshi, O. A.; Ara, S.; Cook, J. M. J. Org. Chem. 2010, 75, 3626.
(i) Yang, C.-T.; Fu, Y.; Huang, Y.-B.; Yi, J.; Guo, Q.-X.; Liu, L. Angew.
Chem., Int. Ed. 2009, 48, 7398. (j) Zhao, Q.; Li, L.; Fang, Y.; Sun, D.;
Li, C. J. Org. Chem. 2009, 74, 459.
(8) (a) Taniguchi, N. J. Org. Chem. 2004, 69, 6904. (b) Cristau, H. J.;
Chabaud, B.; Labaudiniere, R.; Christol, H. J. Org. Chem. 1986, 51,
875. (c) Zhang, Y.; Ngeow, K. C.; Ying, J. Y. Org. Lett. 2007, 9, 3495.
(9) (a) Duan, Z.; Ranjit, S.; Zhang, P.; Liu, X. Chem.Eur. J. 2009,
15, 3666. (b) Ranjit, R.; Duan, Z.; Zhang, P.; Liu, X. Org. Lett. 2010,
12, 4134. (c) Becht, J.-M.; Drian, C. L. J. Org. Chem. 2011, 76, 6327.
(10) (a) Wang, Z.; Zhu, L.; Yin, F.; Su, Z.; Li, Z.; Li, C. J. Am. Chem.
Soc. 2012, 134, 4258. (b) Yin, F.; Wang, Z.; Li, Z.; Li, C. J. Am. Chem.
Soc. 2012, 134, 10401. (c) Liu, X.; Wang, Z.; Cheng, X.; Li, C. J. Am.
Chem. Soc. 2012, 134, 14330.
(11) (a) Mai, W.-P.; Song, G.; Sun, G.-C.; Yang, L.-R.; Yuan, J.-W.;
Xiao, Y.-M.; Mao, P.; Qu, L.-B. RSC Adv. 2013, 3, 19264. (b) Shang,
R.; Liu, L. Sci. China Chem. 2011, 54, 1670.
(12) (a) Shang, R.; Yang, Z.-W.; Wang, Y.; Zhang, S.-L.; Liu, L. J. Am.
Chem. Soc. 2010, 132, 14391. (b) Shang, R.; Ji, D.-S.; Chu, L.; Fu, Y.;
Liu, L. Angew. Chem., Int. Ed. 2011, 50, 4470. (c) Shang, R.; Huang, Z.;
Chu, L.; Fu, Y.; Liu, L. Org. Lett. 2011, 13, 4240. (d) Shang, R.; Huang,
Z.; Xiao, X.; Lu, X.; Fu, Y.; Liu, L. Adv. Synth. Catal. 2012, 354, 2465.
(13) (a) Bi, H.-P.; Zhao, L.; Liang, Y.-M.; Li, C.-J. Angew. Chem., Int.
Ed. 2009, 48, 792. (b) Zhang, C.; Seidel, D. J. Am. Chem. Soc. 2010,
132, 1798. (c) Das, D.; Richers, M. T.; Ma, L.; Seidel, D. Org. Lett.
2011, 13, 6584. (d) Zuo, J.; Liao, Y.-H.; Zhang, X.-M.; Yuan, W.-C. J.
Org. Chem. 2012, 77, 11325. (e) Lalic, G.; Aloise, A. D.; Shair, M. D. J.
Am. Chem. Soc. 2003, 125, 2852.
D
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