Carbon-carbon bond forming reactions via Pd-catalyzed detellurative homocoupling of diorganyl tellurides

Article abstract of DOI:10.1016/j.tetlet.2017.07.087

A simple and highly efficient method for the constructions of Csp-Csp, Csp²-Csp² and Csp³-Csp³ bonds is reported. The symmetrical diaryl tellurides undergo detellurative homocouplings to afford symmetrical biaryl products. The reactions are carried out at ambient temperature using PdCl₂ as a catalyst in the presence of Ag₂O and Na₂CO₃. Similarly, the detellurative homocouplings of dibenzyl telluride and bis(phenylethynyl)telluride give bibenzyl and the conjugated diyne, respectively.

Full text of DOI:10.1016/j.tetlet.2017.07.087

Accepted Manuscript
Carbon-carbon bond forming reactions via Pd-catalyzed detellurative homo-
coupling of diorganyl tellurides
Shaozhong Zhang, Lalitha Kolluru, Souseelya K Vedula, Drew Whippie, Jin Jin
PII:
S0040-4039(17)30943-7
DOI:
http://dx.doi.org/10.1016/j.tetlet.2017.07.087
TETL 49169
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Accepted Date:
24 May 2017
24 July 2017
Please cite this article as: Zhang, S., Kolluru, L., Vedula, S.K., Whippie, D., Jin, J., Carbon-carbon bond forming
reactions via Pd-catalyzed detellurative homocoupling of diorganyl tellurides, Tetrahedron Letters (2017), doi:
http://dx.doi.org/10.1016/j.tetlet.2017.07.087
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Graphical Abstract
Carbon-carbon bond forming reactions via Pd-catalyzed
detellurative homocoupling of diorganyl tellurides
Leave this area blank for abstract info.
Shaozhong Zhang, Lalitha Kolluru, Souseelya Keerthi Vedula, Drew Whippie and Jin Jin*
Department of Chemistry, Western Illinois University, Macomb, IL 61455
PdCl , Na CO
3
2
2
RTeR
R-R
Ag O or AgOAc, CH OH, rt, 2 h
2
3

1
Tetrahedron Letters
Carbon-carbon bond forming reactions via Pd-catalyzed detellurative
homocoupling of diorganyl tellurides
Shaozhong Zhang, Lalitha Kolluru, Souseelya K Vedula, Drew Whippie and Jin Jin*
Department of Chemistry, Western Illinois University, Macomb, IL 61455
ARTICLE INFO
ABSTRACT
2
2
3
Article history:
Received
A simple and highly efficient method for the constructions of Csp-Csp, Csp -Csp and Csp -
3
Csp bonds is reported. The symmetrical diaryl tellurides undergo detellurative homocouplings
Received in revised form
Accepted
to afford symmetrical biaryl products. The reactions are carried out at ambient temperature using
PdCl as a catalyst in the presence of Ag O and Na CO . Similarly, the detellurative
2 2 2 3
Available online
homocouplings of dibenzyl telluride and bis(phenylethynyl)telluride give bibenzyl and the
conjugated diyne, respectively.
Keywords:
Symmetrical diorganyl telluride
Detelluration
Homocoupling
2009 Elsevier Ltd. All rights reserved.
Palladium chloride
Introduction
system in the presence of phosphines as a successful catalyst for
the detelluration of organotellurides and ditellurides.
22
Organotellurium compounds have attracted more
attentions in recent years due to their important roles in
organic synthesis and biological activities. They have been
Here we report a very simple method for the synthesis of
symmetrical biaryl compounds via the detellurative
homocoupling of symmetrical diaryl tellurides. The
1
used instead of halogens as electrophilic partners in some
palladium-catalyzed cross-coupling reactions such as Heck
reactions are promoted by a catalytic amount of PdCl
2
2
3
4
reaction, Negishi coupling and Suzuki coupling. Carbon-
carbon bond formation is involved in all areas of organic
chemistry since the skeleton of all organic molecules is
made of carbon-carbon bonds. The formation of aryl-aryl
bond is one of the most important targets in organic
synthesis. The biaryl scaffold is a core component occurring
without using any ligands and occur at room temperature
with good yields. The use of tellurium agents here is
advantageous compared to the usual previously described
methods because of the mildness of the experimental
conditions.
5
6
7
in natural products, pharmaceuticals, agrochemicals and
Conjugated diynes or dienes are also important structures
8
many biologically important molecules. Many biaryl
23
and useful building blocks in organic synthesis. They have
compounds have been reported to possess activities like
been found to exist widely in nature and possess special
9
10
11
antibiotic,
anti-inflammatory,
antidiabetic,
antihypertensive,
etc. The synthesis of
symmetrical biaryls has been traditionally achieved by
24
biological activities. In addition, conjugated diynes have
1
2
13
anticancer,
25
also been found to be crucial in material science. Therefore
we also explored the detelluration reactions on
bis(ethynyl)telluride and bis(vinyl)telluride. In order to
examine whether the reaction will occur on dialkyl
tellurides, we synthesized dibenzyl telluride as well and
performed the detelluration reaction on it.
1
4
Ullmann reaction. Other methods include using metal-
catalyzed homocoupling of aryl halides, aryl boronic
acids, aryl Grignard reagents, methoxyarenes and aryl
diazonium salts.
1
5
1
6
17
18
1
9
As reported by Bergman in 1970s, diaryltellurium dichlorides
We recently reported a method to prepare symmetrical
are detellurated by treatment with degassed Raney nickel in
0
diaryl tellurides in a catalyst-free condition using Te as the
20
diglyme at reflux, giving the corresponding biaryls. Since then,
there have been more reports on detelluration of organotellurium
chalcogen source in the presence of KOH, which is shown
26
in Scheme 1.
21
compounds. For example, it was reported by Barton that
palladium(0) converts symmetrical and unsymmetrical tellurides
21
into coupled compounds. The drawback of these methods is the
necessity of more than a stoichiometric amount of the required
metal or the requirement of harsh condition such as high
Te0
Te
I
R
R
R
KOH, DMSO
o
temperature. Further reports describe the use of the Ni(PEt
3
)
4
110 C, 10 h
R = H, p-CH , m-CH , p-Cl, p-OCH , naphthyl, o-OCH ,
3
3
3
3
m-OCH , p-F, p-OCF , p-t-butyl, o-OCF , p-Br, 2,4-dimethyl
3
3
3

Corresponding author. Tel.: +1-309-298-2261; fax: +1-309-298-2180;
Scheme 1. Synthesis of symmetrical diaryl tellurides
e-mail: j-jin@wiu.edu

2
Table 2: Synthesis of symmetrical biaryls by detelluration of diaryl telluridesa
The diaryl tellurides synthesized above would then be
used as the substrates for the detellurative coupling reactions
to form symmetrical biaryls. In order to find the optimal
conditions, we selected bis(p-tolyl)telluride as a model
substrate (Table 1). A variety of conditions were screened
such as catalyst, additive, base, solvent and reaction
temperature. Among the four catalysts screened, we found
PdCl , Na CO
3
2
2
ArTeAr
Ar-Ar
Ag2O, CH3OH, rt 2h
Diaryl tellurides (ArTeAr)
Te
Biaryls (Ar-Ar)
Yield (%)b
Entry
1
PdCl
reaction (Table 1, entry 1-4). Subsequently, Na
found to be a more proper base when compared to Et
Table 1, entry 2 and 5). Several kinds of solvents such as
2
was the optimal catalyst for the detellurative coupling
95
92
2
CO was
3
1
2
3
N
Te
(
2
3
CH
CH
3
OH, DMSO and CH
3
CN were also examined, and
3
OH was the optimal solvent for this reaction (Table 1,
Te
Te
entry 5-7). The oxidant additive is also critical in this
reaction. We found the detelluration reaction did not
proceed at all in the absence of Ag O or AgOAc as the
2
80
3
Cl
Cl
4
5
92
additive (Table 1, entry 10). Furthermore, when the reaction
o
Cl
Cl
4
temperature was lowered from 65 C to the ambient
Te
temperature with either Ag
same yields were obtained as that at higher temperature
Table 1, entry 5, 8 and 9). Based on these results, the
optimal conditions for the detellurative coupling of diaryl
tellurides involved the use of 10 mol% of PdCl as catalyst,
Ag O or AgOAc as additive, Na CO as base in CH OH at
2
O or AgOAc as the additive, the
H3CO
OCH3
90
89
H CO
OCH3
3
5
(
Te
6
7
2
2
2
3
3
6
room temperature for 2 hours in ambient air.
OCH3
OCH3
Te
OCH3
8
0
a
Table 1: Optimization of detellurative coupling reactions
H3CO
OCH3
7
Catalyst, Additive
Te
H CO
Te
OCH3
3
75
85
8
9
Base, Solvent, Temp
8
H3CO
1
Te
Temp ( C) Yieldb (%)
o
Entry Catalyst
Additive
Base
Solvent
F
F
F
F
1
2
Pd(OAc)2
PdCl2
Ag2O
Ag2O
Et3N
Et3N
CH3OH
CH3OH
65
65
20
50
9
Te
1
1
0
F3CO
OCF3
7
2
3
4
5
6
7
8
9
CuI
Ag2O
Ag2O
Ag2O
Ag2O
Ag2O
Ag2O
AgOAc
Et3N
CH3OH
CH3OH
CH3OH
DMSO
65
65
65
65
65
rt
0
F3CO
OCF3
10
NiSO4
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
Et3N
0
Te
Na2CO3
Na2CO3
Na CO
95
60
20
95
95
1
75
74
1
1
CH3CN
CH3OH
CH3OH
OCF3
2
3
OCF3
OCF3
2
Na CO
3
12
Te
Na2CO3
rt
F3CO
1
a
0
PdCl2
Na2CO3
CH3OH
65
0
1
2
Reaction conditions: bis(p-toly)telluride (1 equiv.), catalyst (10 mol %),
Te
additive (2 equiv.), base (2 equiv.), solvent (3 mL), under air, 2 h.
Br
Br
1
3
83
60
b
Isolated yield.
Br
Br
13
Te
Te
With the optimal conditions for the detelluration reaction in
hand, a series of parent precursors of symmetrical diaryl
tellurides were conveniently prepared in high yields using the
1
4
1
4
approach mentioned in Scheme 1.
Subsequently, the
1
5
H2N
NH2
0
detellurative coupling reactions were performed on these diaryl
tellurides (Table 2). The reactions proceeded nicely with
electron-withdrawing and most electron-donating substituents at
ortho, meta or para position in the biaryl architecture. However,
it should be pointed out that when bis(p-aminophenyl)telluride
was used as the substrate, the desired biaryl product 15 was not
obtained (Table 2, entry 15). An unidentified product was
resulted probably due to the coordination reaction between N and
H N
2
NH2
1
5
a
Reaction conditions: diaryl telluride (1 mmol), PdCl2 (0.1 mmol),
Ag O (2 mmol), Na CO (2 mmol), CH OH (3 mL), rt, 2 h.
2
2
3
3
b
Isolated yield.
Pd.
All other symmetrical biaryl products (1-14) were
successfully prepared by the detellurative coupling approach in

3
2
7
good yields, as summarized in Table 2. All of the synthesized
altogether
for
the
detelluration
of
(Z,Z)-
1
13
products were characterized by H, C NMR and Mass
spectroscopy.
bis(phenylethenyl)telluride, 17 at a ratio of 1:6:3, as determined
by H NMR spectroscopy. However, the detellurative coupling of
1
18 and 19 proceeded nicely to afford the corresponding
conjugated diyne 18a and bibenzyl 19a in high yields, as shown
in Table 3.
2
1
According to a previous report, the catalytic cycle for the
detellurative coupling of symmetrical diary tellurides involves
the formation of a telluride-palladium (II) complex (a) which
further undergoes a double aryl migration affording another
palladium complex (b), as shown in Scheme 2. Reductive
elimination of complex (b) leads to the formation of biaryl
compound (Ar-Ar) along with Pd(0) and elemental tellurium.
Table 3: Detelluration of other diorganyl tellurides
PdCl , Na CO
3
2
2
RTeR
R-R
AgOAc, CH OH, rt
3
+
Pd(0) is later oxidized by Ag ions to Pd(II) thus completing the
Entry
1
Diaryl tellurides
Biaryls
Yield (%)
Ph
catalytic cycle.
Ph
Ph
Ar
Ph
Ph
Te
Ph
Ph
Ph
84
Ar
Ph
17b, ZE
Te
Pd (II)
(a)
17a, ZZ
Ph
17c, EE
Te
Pd (0)
17
Ar
(17a: 17b: 17c = 1:6:3)
Ar
2
3
Te
Ph
Ph
90
18
18a
ArTeAr
Ar
Ph
Te
Pd
Ph
Ph
Te Ph
19
Pd (II)
Ag+
Ar
90
(
b)
19a
Ar-Ar
+ Te
Pd (0)
Conclusions
Scheme 2: Possible mechanism for the formation of symmetrical biaryls
In summary, we demonstrated a simple method for carbon-
carbon bond forming reactions. The detellurative homocouplings
of symmetrical diaryl tellurides provide biaryl compounds. The
reaction requires only a catalytic amount of palladium catalyst
and completes efficiently at room temperature. Similarly, the
detellurative homocouplings of other diorganyl tellurides such as
dibenzyl telluride and bis(phenylethynyl)telluride afford the
corresponding bibenzyl and the conjugated diyne, respectively.
Next, in order to examine if this approach is also applicable
for the synthesis of unsymmetrical biaryls, we synthesized an
unsymmetrical diaryl telluride (4-methoxyphenyl phenyl
28
telluride, 16) according to the literature method and proceeded
the detelluration reaction on it. However, the desired detellurative
coupling product (4-methoxybiphenyl, 16a) was obtained
together with the formation of the other two symmetrical biaryl
by-products (16b and 16c) in a ratio of 3:5:2, as shown in
Scheme 3. Therefore we conclude this methodology is not ideal
for the synthesis of unsymmetrical biaryl products.
Acknowledgments
The authors are grateful to NSF MRI award (Acquisition of a
400-MHz NMR Spectrometer to Support Faculty-Student
Research and Training at WIU and Partner Institutions), college
of arts and science at WIU for financial support.
B(OH)2
Fe
Supplementary data
PhTeTePh
+
Te
OCH3
Full experimental details and spectroscopic data of all
DMSO, 130 o
C
1
13
16
compounds, H and C NMR, HRMS data can be found.
Supplementary data associated with this article can be found.
OCH3
PdCl2,
AgOAc, MeOH, rt, 2 h
Na2CO3
OCH3
+
+ H3CO
OCH3
References and notes
1
6a
16a: 16b: 16c = 3:5:2)
Scheme 3: Detelluration reaction of unsymmetrical diaryl telluride
16b
16c
nd
(
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