Palladium(II)/Copper(II)-Catalyzed C–H Sulfidation or Selenation of Arenes Leading to Unsymmetrical Sulfides and Selenides

Article abstract of DOI:10.1002/ejoc.201801765

A novel palladium(II)/copper(II)-catalyzed sulfidation of the C–H bond in electron-rich arenes and in pentafluorobenzene with disulfides was developed. This catalytic system can be used to efficiently produce various types of either unsymmetrical aryl sulfides or alkyl aryl sulfides. The present protocol could also be applied to the direct preparation of unsymmetrical aryl selenides via C–H selenation.

Full text of DOI:10.1002/ejoc.201801765

A Journal of
Accepted Article
Title: Palladium(II)/Copper(II)-Catalyzed C-H Sulfidation or Selenation
of Arenes Leading to Unsymmetrical Sulfides and Selenides
Authors: Kota Nishino, Shouya Tsukahara, Yohei Ogiwara, and Norio
Sakai
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201801765
Link to VoR: http://dx.doi.org/10.1002/ejoc.201801765
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10.1002/ejoc.201801765
European Journal of Organic Chemistry
FULL PAPER
Palladium(II)/Copper(II)-Catalyzed C-H Sulfidation or Selenation of
Arenes Leading to Unsymmetrical Sulfides and Selenides
Kota Nishino,[a] Shouya Tsukahara,[a] Yohei Ogiwara,[a] and Norio Sakai*[a]
Abstract: We developed a novel palladium(II)/copper(II)-catalyzed
sulfidation of the C–H bond in electron-rich arenes and in
pentafluorobenzene with disulfides. This catalytic system can be used
to efficiently produce various types of either unsymmetrical aryl
sulfides or alkyl aryl sulfides. Also, the present protocol could be
applied to the direct preparation of unsymmetrical aryl selenides via
C–H selenation.
Recently, as other approaches, metal-free preparations of aryl
sulfides through the reactions of either electron-rich arenes, such
as trimethoxybenzene,[13] and N-heterocyclic arenes,[14] or
electron-deficient arenes, such as pentafluorobenzene[15] with
typical sulfur sources, such as thiols and disulfides, has been
demonstrated. Also, the reactions of these arenes with
electrophilic organosulfur reagents such as an N-
thiosuccinimide[13d] and an aryl sulfinic acid derivative[13c,13e,14c]
have led to the preparation of aryl sulfide derivatives. These
methods, however, generally require either a catalytic or a
stoichiometric amount of an oxidizing agent, molecular iodine, a
strong acid or a base.
Introduction
Aryl sulfides constitute a common framework for highly functional
molecule, such as pharmaceuticals and organic materials.[1] The
conventional preparation of an aryl sulfide involves a coupling
reaction of aryl halides with sulfur sources as alkali sulfides and
elemental sulfur, and organosulfur compounds, such as thiols and
disulfides.[2]
Our group reported a PdCl2-catalyzed intramolecular cyclization
of 2-biphenyl disulfides to dibenzothiophenes in DMSO (eq 1 in
Scheme 1).[16] This protocol via C–H sulfidation was useful for the
C–S bond formation of a variety of 2-biphenylyl disulfides because
this synthetic method does not require extra additives, such as
metal oxidant, a ligand, and a base. In the present study, we first
attempted to apply the utility of the PdCl2/DMSO catalytic system
described in eq 1 to an intermolecular mode between electron-
rich arenes and disulfides (eq 2 in Scheme 1). Second, we
investigated the intermolecular bis-sulfidation of a C–H/C–F bond
in an electron-deficient arene, pentafluorobenzene, (eq 3 in
Scheme 1). Finally, we developed a direct and effective selenation
of these arenes. Herein, we report the full details.
The directly transition-metal-catalyzed formation of a C(sp2)–S
bond from a C–H bond of arenes has recent received much
attention, because this strategy enables to lead
a target
compound without extra functional group transformations. The
synthetic protocols of aryl sulfides, Pd,[3] Ni,[4] Rh,[5] Cu,[6] Co,[7] or
Ru,[8]-catalyzed C–H sulfidation have been demonstrated. Most of
these sulfidations, however, have been limited to the use of
starting materials bearing a directing group such as a pyridyl
group,[3a,5a,6b] a pyrimidyl group,[4f,5b,6d,7a] and an 8-aminoquinolyl
group,[4c,4d,4e,6a] which creates difficulties in expanding the
substrate scope.
our previous work
PdCl2 (5 mol %)
S
On the other hand, C–H sulfidation of electron-rich or electron-
withdrawing group-substituted arenes have been investigated.
Because these methods do not require substrates with a directing
group, the development of this type of synthetic protocol is
valuable and practical. For example, arenes such as an indole,[9]
S
(1)
(2)
DMSO, 120 °C, 12 h
S
this work
PdCl2 (5 mol %)
CuCl2 (5 mol %)
Ar
trimethoxybenzene,[10]
a
benzothiazole,[11]
and
S
S
+
Ar-H
pentafluorobenzene[12] have been subjected to C–H sulfidation
with a transition metal catalyst.
Ar
S
Ar
Ar
F
DMSO, 120 °C, 12 h
Ar = electron-rich arene
F
PdCl2 (5 mol %)
CuCl2 (5 mol %)
base (2 equiv)
F
[a]
K. Nishino, S. Tsukahara, Dr. Y. Ogiwara, Prof. Dr. N. Sakai
Department of Pure and Applied Chemistry
Faculty of Science and Technology, Tokyo University of Science
(RIKADAI)
F
S
F
Ar
S
Ar
+
(3)
Ar
S
Ar
DMSO, 120 °C, 12 h
F
F
S
F
F
Noda, Chiba, 278-8510 (Japan)
Scheme 1. PdCl2-catalyzed construction of a C-S bond from a C–H bond.
E-mail: sakachem@rs.noda.tus.ac.jp
Homepage: http://www.rs.tus.ac.jp/sakaigroup/
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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10.1002/ejoc.201801765
European Journal of Organic Chemistry
FULL PAPER
With the optimal conditions in hand, the synthesis of various
unsymmetrical sulfides bearing a trimethoxybenzene moiety was
then examined and the results are listed in Table 2. When using
electron-donating substituted disulfides 2b and 2c, the
corresponding sulfides 3b and 3c were obtained in high yields.
Next, when examining the preparation of a sulfide bearing
electron-withdrawing groups such as a chloro and a nitro group,
the expected sulfides 3d and 3e were provided in high yields.
Moreover, the synthesis of a heterocycle-substituted sulfide was
attempted, and sulfide 3f bearing a pyridinyl group was afforded
in a moderate yield. We were pleased to discover that the
preparation of sulfide 3g bearing a benzothiazolyl group was
achieved in a high yield. Consequently, this protocol revealed a
relatively wide scope of disulfide substrates, which led to the
production of various unsymmetrical diaryl sulfides. Furthermore,
when applying dibenzyl disulfide to a dialkyl disulfide under our
optimal conditions, the desired aryl benzyl sulfide 3h was
obtained in a relatively good yield.[19]
Results and Discussion
Initially, we focused on optimizing the reaction conditions. When
1,3,5-trimethoxybenzene (1) as an electron-rich arene and
diphenyl disulfide (2a) were treated with palladium dichloride, the
desired sulfide 3a was obtained in a low yield (Table 1, entry 1).
Without a metal catalyst, however, the expected coupling product
was not obtained (entry 2). Next, when adding a catalytic amount
of CuCl2 as an oxidant, the yield of 3a was greatly improved to
93% (entry 3). When a thiol is formed through hydrolysis of a
palladium thiolate species in a sulfidation series, one of the roles
of CuCl2 is believed to be the re-oxidization of the thiol to a
disulfide.[17] Compared with the use of PdCl2, however, other
palladium catalysts such as Pd(OAc)2, Pd(dba)2, and Pd(PPh3)4
produce lower yields of 3a (entries 4-6). Also, NiCl2 did not show
a highly catalytic activity for the sulfidation (entry 7). Lowering the
reaction temperature led to a slight decrease in the product yield
of 3a (entry 8). When attempting the use of DMF as a solvent, the
expected reaction did not proceed well (entry 9). Thus, DMSO
played the role of an oxidant and was an essential agent in this
reaction.[18] Moreover, when using only CuCl2, sulfidation was not
effective (entry 10).
Table 2. Scope of the sulfidation of trimethoxybenzene with diaryl disulfides.[a]
OMe
OMe
PdCl2 (5 mol %)
CuCl2 (5 mol %)
Ar
S
Ar
S
+
OMe
Ar
S
Table 1. Examination of the reaction conditions.[a]
DMSO, 120 °C, 12 h
MeO
MeO
OMe
OMe
OMe
1: (0.5 mmol)
2: (0.5 equiv)
3
Metal catalyst (5 mol %)
Oxidant (5 mol %)
S
OMe
OMe
Ph
S
Ph
+
Ph
S
S
S
DMSO, 120 °C, 12 h
MeO
OMe
MeO
OMe
3a
MeO
Me
MeO
OMe
1: (0.5 mmol) 2a: (0.5 equiv)
OMe
3b: 88%
OMe
OMe
3c: 76%
Entry
Metal
Oxidant
Conversion
Yield [%][b]
catalyst
OMe
S
S
1
PdCl2
----
24
17
>99
85
37
92
75
61
29
33
14
0
MeO
MeO
Cl
MeO
NO2
Bn
2
----
----
OMe
OMe
3d: 86%
3e: 74%
3
PdCl2
CuCl2
CuCl2
CuCl2
CuCl2
CuCl2
CuCl2
CuCl2
CuCl2
93 (84)
76
3
OMe
OMe
OMe
S
4
Pd(OAc)2
Pd(dba)2
Pd(PPh3)4
NiCl2
S
N
S
S
N
5
MeO
MeO
OMe
OMe
OMe
3h: 60%b
6
75
62
54
22
17
3g: 88%
3f: 49%
7
[a] Reaction conditions: trimethoxybenzene (1: 0.5 mmol), disulfide (2: 0.25
mmol), PdCl2 (0.025 mmol), CuCl2 (0.025 mmol) in DMSO (0.5 mL), 120 °C, 12
h, under air. [b] At 100 °C.
8[c]
9[d]
10
PdCl2
PdCl2
Subsequently, the substrate scope was extended to an electron-
rich heterocycle (Table 3). In the reaction between indole and
diphenyl disulfide, a thiophenyl group was selectively introduced
at the C3 position of indole to produce unsymmetrical sulfide 5a
in a moderate yield. With di-(p-tolyl) disulfide, the corresponding
product 5b was given in a 60% yield. When using N-methyl indole
and a disulfide bearing a benzothiazole ring, an interesting
unsymmetrical sulfide 5c that involved two different heterocyclic
moieties was given in a practical yield. Additionally, in two cases
with N-methylindole bearing a phenyl group at the C2 position,
----
[a] Reaction conditions: trimethoxybenzene (1: 0.5 mmol), diphenyl disulfide
(2a: 0.25 mmol), a metal catalyst (0.025 mmol), an additive (0.025 mmol),
DMSO (0.5 mL), 120 °C, 12 h, under air. [b] GC yield; Isolated yield is given in
parenthesis. [c] At 80 °C. [d] In DMF.
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10.1002/ejoc.201801765
European Journal of Organic Chemistry
FULL PAPER
each sulfidation effectively proceeded to give 5d and 5e in good
yields. This catalytic protocol shows a high effect for sulfidation of
even 2-substituted indole, which generally shows a high degree
of steric hindrance toward the C3 position. Fortunately, when
using an indole bearing a bromo group at the C5 position, the
group of which frequently reacts with a palladium catalyst, sulfide
5f preserved the bromo group was provided in a good yield. Thus,
the present catalytic system composed of palladium(II) with a
copper(II) catalyst shows a relatively wide tolerance of functional
groups.
Table 4. Sulfidation of the imidazopyridine and the indolizine.[a]
PdCl2 (5 mol %)
CuCl2 (5 mol %)
S
Ar
HetAr—H
+
HetAr—SAr
Ar
S
DMSO, 120 °C, 12 h
6: (0.5 mmol) 2: (0.5 equiv)
7
Yield (%)
HetAr
Disulfide
Product
N
N
63%
N
N
Me
S
6a
2b
Me
Table 3. Scope of the sulfidation of an indole.[a]
7a
OMe
Ar
S
PdCl2 (5 mol %)
CuCl2 (5 mol %)
S
S
Ar
Ar
R
Ar
R
+
Ar
S
62%
DMSO, 120 °C, 12 h
N
N
N
N
MeO
R
R
2cb
S
6b
4: (0.5 mmol)
2: (0.5 equiv)
5
OMe
7b
N
Me
S
S
S
S
S
S
S
N
S
N
H
N
N
51%
N
N
H
Me
N
S
5a: 37%
5b: 60%
5c: 65%
2gb
6b
N
N
N
OMe
7c
S
S
S
S
S
Br
[a] Reaction conditions: N-heterocycles (6: 0.5 mmol), disulfide (2: 0.25 mmol),
PdCl2 (0.025 mmol), CuCl2 (0.025 mmol) in DMSO (0.5 mL), 120 °C, 12 h, under
air. [b] disulfide (1.0 equiv).
Ph
Ph
N
N
N
H
Me
Me
5e: 82%b
5d: 83%
5f: 76%b
F
PdCl2 (5 mol %)
CuCl2 (5 mol %)
CsF (2 equiv)
Ph
F
[a] Reaction conditions: indole (4: 0.5 mmol), disulfide (2: 0.25 mmol), PdCl2
(0.025 mmol), CuCl2 (0.025 mmol) in DMSO (0.5 mL), 120 °C, 12 h, under air.
[b] DMSO (0.5 M).
F
S
S
F
F
F
Ph
S
+
Ph
Ph
S
DMSO, 120 °C, 12 h
F
F
F
The present C–H sulfidation was further applied to two electron-
rich heteroarenes (Table 4). When using 2-phenylimidazo[1,2-
a]pyridine (6a) as a substrate, the expected sulfidated compound
7a was afforded in a good yield. Also, under the optimal conditions,
2-phenylindolizine (6b) and 1.0 equiv of disulfide 2c yielded a
double-sulfidated product 7b as the sole product, but the
formation of a mono-sulfidated compound was not observed.[20] In
a similar manner, heterocyclic disulfide 2g afford a di-sulfidated
indolizine in a moderate yield. Unlike previous studies at the bis-
sulfidation of indolizines,[21] a primary feature of our C–H bis-
sulfidation is that the reaction catalytically proceeds.
8: (0.5 mmol) 2a: (1.0 equiv)
9a
80% (GC yield)
Without CsF: 0%
Scheme 2. Bis-sulfidation of pentafluorobenzene with diphenyl disulfide by
addition of CsF.
Based on the results shown in Scheme 2, the scope of the bis-
sulfidation of pentafluorobenzene with several disulfides was
investigated, and the results are summarized in Table 5. When
using diphenyl disulfide with CsF, the corresponding product 9a
was isolated in a 73% yield. A methyl-substituted disulfide at
either the m- or the p-position was also converted into the bis-
sulfidated compounds 9b and 9c in good yields, and 4-
ethylphenyl disulfide gave product 9d in a 37% yield. Notably, an
aliphatic disulfide, dibutyl disulfide, provided the corresponding
product 9e in a moderate yield.
Next, sulfidation of
a
strong electron-deficient arene,
pentafluorobenzene, with a disulfide was attempted using the
PdCl2/DMSO system. In this reaction, the optimal conditions
required a further addition of 2 equiv of CsF to effectively promote
bis-sulfidation of both
a C–H bond and a C–F bond of
pentafluorobenzene (Scheme 2).[22] We speculated that CsF,
which cooperates with a palladium catalyst would function as a
base to abstract an acidic proton of pentafluorobenzene.
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10.1002/ejoc.201801765
European Journal of Organic Chemistry
FULL PAPER
Table 5. Scope of the bis-sulfidation of pentafluorobenzene with disulfides.[a]
reaction of trimethoxybenzene (1a) with 1.0 equiv of diphenyl
diselenide was conducted in the presence of 5 mol % of PdCl2
and CuCl2 in DMSO, the corresponding di-selenated compound
10a was obtained in a 69% yield.[23] Additionally, N-methyl-2-
phenylindole gave the corresponding unsymmetrical selenide 10b
in an excellent yield. When using 2-phenylindolizine and diphenyl
diselenide, as well as the reaction with diphenyl disulfide (vide
Table 4), double C–H selenation proceeded to produce bis-
selenated 2-phenylindolizine 10c in a moderate yield. This
process was also successful in the bis-selenation of
pentafluorobenzene. This type of direct bis-selenation of either 2-
phenylindolizine or pentafluorobenzene is unprecedented.
PdCl2 (5 mol %)
CuCl2 (5 mol %)
CsF (2 equiv)
F
F
F
F
F
S
S
F
R
S
R
+
R
S
R
DMSO, 120 °C, 12 h
F
F
F
8: (0.5 mmol) 2: (1.0 equiv)
9
F
F
F
Me
F
S
S
F
S
F
S
Ph
Ph
F
F
Me
9b: 69%b
9a: 73%
To gain preliminary insight into the sulfidation of
pentafluorobenzene, control experiments were performed. Under
the optimal conditions with or without PdCl2, the initial reaction of
prepared mono-sulfidated arene 11 with diphenyl disulfide (2a)
resulted in a rather low conversion of 11 (eq 1 in Scheme 3). The
reaction between prepared substrate 12 and diphenyl disulfide
with only CsF (2 equiv), however, yielded bis-sulfidated
compound 9a in a 78% yield (eq 2 in Scheme 3). In the absence
of CsF, product 9a was not obtained. These results showed that,
rather than the substitution of compound 11 at the C–H side, the
substitution of compound 12 at the C–F bond is the major key step
in the sulfidation series, and the mechanism of the C–S bond
formation from the C–F bond of intermediate 12 proceeds through
CsF-promoted aromatic nucleophilic substitution that involves
neither PdCl2 nor CuCl2.
F
F
S
F
F
Me
S
F
Et
Me
S
Et
F
S
F
F
9c: 85%b
9d: 37%b
F
F
Me
S
F
F
S
Me
9e: 54%
[a] Reaction conditions: pentafluorobenzene (8: 0.5 mmol), disulfide (2: 0.5
mmol), PdCl2 (0.025 mmol), CuCl2 (0.025 mmol), CsF (1.0 mmol) in DMSO (0.5
mL), 120 °C, 12 h, under air. [b] At 140 °C.
F
PdCl2 (5 mol %)
CuCl2 (5 mol %)
CsF (2 equiv)
F
Table 6. Selenation of arenes with a PdCl2/CuCl2 catalyst.[a]
F
SPh
(1)
F
H
S
Ph
+
PdCl2 (5 mol %)
Ph
S
DMSO, 120 °C, 12 h
PhS
F
CuCl2 (5 mol %)
PhS
F
Se
Se
Ar
F
+
Ar—H
F
Se
DMSO, 120 °C, 12 h
11: (0.2 mmol) 2a: (0.5 equiv)
9a
(0.5 mmol)
(1.0 equiv)
10
9a: 4%, recovery of 11: 71% (GC yield)
without PdCl2, 9a: 11%, recovery of 11: 61% (GC yield)
OMe
F
F
Se
Se
Se
F
SPh
F
SPh
+
CsF (2 equiv)
S
Ph
Ph
(2)
Ph
S
DMSO, 120 °C, 12 h
N
PhS
F
F
F
MeO
OMe
Me
F
9a
F
10a: 69%b
10b: 94%c
12: (0.2 mmol) 2a: (0.5 equiv)
9a: 78%, recovery of 12: 0% (GC yield)
without CsF, 9a: 0%, recovery of 12: 86% (GC yield)
Se
Se
F
Scheme 3. Control experiments to clarify a key intermediate.
Se
F
Se
N
On the basis of these results, a plausible reaction mechanism for
a series of sulfidation is outlined in Scheme 4. Initially, a
palladium(II) catalyst reacts with an arene leading to palladium
arene species A through C–H functionalization. Then, oxidative
addition of A into a disulfide occurs to generate palladium(IV)
complex B.[24] Subsequently, reductive elimination from complex
B provides unsymmetrical sulfide C and palladium thiolate
species D, the latter of which would be hydrolyzed by HX to
reproduce PdX2 and a thiol. Also, the role of CuCl2 is assumed to
be that of an oxidant to generate a disulfide from a formed thiol,
and DMSO must function as a re-oxidant of CuCl. In the case of
F
F
10c: 43%
10d: 59%d,e
[a] Reaction conditions: arene (0.5 mmol), diphenyl diselenide (0.5 mmol), PdCl2
(0.025 mmol), CuCl2 (0.025 mmol) in DMSO (0.5 mL), 120 °C, 12 h, under air.
[b] a little amount of mono-selenated compound was observed. [c] diphenyl
diselenide (0.5 equiv). [d] At 140 °C. [e] added CsF (2 equiv).
It was rewarding to find that the present reaction system was
applicable to C–H selenation (Table 6). For example, when the
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10.1002/ejoc.201801765
European Journal of Organic Chemistry
FULL PAPER
pentafluorobenzene, the C–F bond of unsymmetrical sulfide C (Ar
= C6F5) again reacts with a disulfide in the presence of CsF via
aromatic nucleophilic substitution, which finally yields bis-
sulfidated compound E.[25, 26]
solution was then filtered through a celite pad. The filtered solution
was dried over anhydrous Na2SO4, filtered and then evaporated
under reduced pressure. The crude material was purified by a
silica gel column chromatography (hexane/EtOAc) to give the
corresponding sulfide 3.
Me2S, H2O
DMSO
CuCl2
CuCl, HCl
Ar–H
Acknowledgments
S
R
S
PdX2
RSH
R
HX
This work was partially supported by the Sasagawa Scientific
Research Grant from The Japan Science Society.
HX
Pd(II)
Ar
X
PdX(SR)
A
Keywords: Palladium • Sulfidation • Selenation • C–H activation
• Oxidation
D
CsF
F
S
R
SR
Pd(IV)
R
S
S
R
F
SR
R
S
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Müller, L. Ackermann, Chem. Eur. J. 2016, 22, 14151-14154; g) F.
Gao, W. Zhu, D. Zhang, S. Li, J. Wang, H. Liu, J. Org. Chem. 2016,
81, 9122-9130; h) J.-M. Ki, Y. Yu, J. Weng, G. Lu, Org. Biomol.
Chem. 2018, 16, 6047.
S
C
Ar
R
Ar
X
SNAr
(Ar = C6F5)
RS
F
SR
B
F
E
Scheme 4. Proposed reaction mechanism.
Conclusions
In this study, C–H sulfidation of electron-rich arenes such as
trimethoxybenzene and N-heterocyclic compounds was
accomplished using the developed PdCl2/CuCl2 catalytic system.
When using 2-phenylindolizine, the transformation of its double
C–H bonds into a C–S bond proceeded. Also, in the case of
pentafluorobenzene, the addition of 2 equiv of CsF to the catalytic
system underwent the same bis-sulfidation with the
transformation of both the C–H and C–F bonds to two C–S bonds.
Moreover, the present catalytic system was applied to the direct
selenation of various arenes such as trimethoxybenzene, an
indole, an indolizine, and pentafluorobenzene. Further studies of
the extension of derivatives and a mechanistic study are ongoing
in this laboratory.
Experimental Section
General procedure A for the PdCl2-catalyzed synthesis of
sulfide 3
To a freshly distilled DMSO solution (0.5 mL) in a screw-capped
test tube under an ambient atmosphere were successively added
a magnetic stirrer, trimethoxybenzene (1: 84 mg, 0.50 mmol), a
disulfide (2: 0.25 mmol), palladium dichloride (4.4 mg, 0.025
mmol), and copper dichloride (3.35 mg, 0.025 mmol). The test
tube was sealed with a cap that contained a PTFE septum and
was heated to 120 °C for 12 h. After the reaction, the resultant
reaction mixture was diluted with ethyl acetate (3 mL). The
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10.1002/ejoc.201801765
European Journal of Organic Chemistry
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Entry for the Table of Contents
(Please choose one layout)
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C–H sulfidation or selenation of
arenes by a Pd(II)/Cu(II) catalytic
system: Preparation of unsymmetrical
sulfides or selenides by C–H
functionalization has been disclosed.
C–H sulfidation
S
R
S
R
S
Pd(II)/Cu(II) cat.
DMSO
Ar
Ar
R
Kota Nishino, Shouya Tsukahara, Yohei
Ogiwara, Norio Sakai*
+
Ar–H
Se
R
Se
R
Se
R
C–H sulfidation
C–H selenation
OMe
Page No. – Page No.
H
This protocol could be applied
a
H
N
Ar
R
Palladium(II)/Copper(II)-Catalyzed C–
H Sulfidation or Selenation of Arenes
Leading to Unsymmetrical Sulfides
and Selenides
various of arenes. In the case of using
an indolizine and pentafluorobenzene,
bis-sulfidated product were obtained.
N
N
MeO
OMe
R
H
F
H
F
H
N
F
F
H
F
This article is protected by copyright. All rights reserved.