Pd/C-catalyzed ligand-free Hiyama cross-coupling reaction of Aryl halides under aqueous conditions

Article abstract of DOI:10.14233/ajchem.2014.15797

A mild and efficient ligand-free Hiyama cross-coupling reaction using Pd/C as a catalyst under aqueous conditions has been developed. A wide variety of aryl bromides undergo the cross-coupling with aryl siloxanes in excellent yields without the use of any additives. The operational simplicity and the mild reaction conditions add to the value of this method as a practical alternative to the Hiyama cross-coupling of aryl and heteroaryl halides.

Full text of DOI:10.14233/ajchem.2014.15797

Asian Journal of Chemistry; Vol. 26, No. 4 (2014), 1015-1018
http://dx.doi.org/10.14233/ajchem.2014.15797
Pd/C-Catalyzed Ligand-Free Hiyama Cross-Coupling
Reaction of Aryl Halides Under Aqueous Conditions
1
,2,*
2
3
NAGARAJU MITTAPELLY
, KHAGGA MUKKANTI and BUCHI REDDY REGURI
1
2
3
Inogent Laboratories Private Limited, A GVK BIO Company, 28A, IDA, Nacharam, Hyderabad-500 076, India
Centre for Chemical Sciences and Technology, I.S.T. Jawaharlal Nehru Technological University, Kukatpally, Hyderabad-500 085, India
Orchid Chemicals and Pharmaceuticals Ltd., Sholinganallur, Chennai-600 119, India
*
Corresponding author: E-mail: nagunitrogen@yahoo.co.in
Received: 18 May 2013; Accepted: 7 August 2013;
Published online: 15 February 2014;
AJC-14690
A mild and efficient ligand-free Hiyama cross-coupling reaction using Pd/C as a catalyst under aqueous conditions has been developed.
A wide variety of aryl bromides undergo the cross-coupling with aryl siloxanes in excellent yields without the use of any additives. The
operational simplicity and the mild reaction conditions add to the value of this method as a practical alternative to the Hiyama cross-
coupling of aryl and heteroaryl halides.
Keywords: Hiyama cross-coupling, Aryl halide, Pd/C.
aqueous Hiyama reaction was recognized with the develop-
ment of sodium hydroxide as an efficient promoter and several
examples of the Hiyama reaction in aqueous medium using
INTRODUCTION
The efficient formation of carbon–carbon bonds is among
1
2,13
the most crucial transformations in synthetic chemistry. The
palladium-catalyzed aryl-aryl cross-coupling reaction is one
such route to these bond formations and the formed biaryl
substructure is a widely occurring component of biologically
nitrogen based ligands were recently demonstrated
.
However, the main drawback of homogeneous catalysis
is associated with separation and reuse of the catalyst. This
condition leads to a loss of expensive metal (and ligands) and
to the presence of metal impurities in the products. The comp-
lete removal of residual metals is a huge problem especially
for pharmaceutical products where carryover of metal impu-
rities may cause serious problems in the production of many
1
active and functional molecules , which includes the pharma-
2
ceuticals valsartan, telmisartan, felbinac, losartan, imatinib,
3
4
the agrochemical Boscalid , the natural product , biphenomycin
5
and liquid crystals for LCD screens .
2
Traditional methods that have been employed to accom-
formulations .
6
7
plish this biaryls include Pd-catalyzed Suzuki , Negishi ,
In order to address these problems, heterogeneous Pd
catalysis is a promising option. Pd(0) or Pd(II) can be fixed to
a solid support such as activated carbon (charcoal), zeolites
and molecular sieves, metal oxides clays, alkali and alkaline
earth salts, porous glass, organic polymers, or polymers
embedded in porous glass. Different Pd nanoparticles are also
8
9
10
Kumada , Hiyama and Stille reactions. Recently, Hiyama
cross-coupling reaction has gained increased attention as
organosilicon reagents are commercially available at relatively
low cost or can be easily prepared. These reagents are also
nontoxic and quite stable to the presence of other functionalities
and to a variety of reaction conditions.
7
active catalytic systems due to their large surface area and
Generally, phosphine ligands are used to complex and
activate the palladium species and excellent results have been
reported for the palladium-catalyzed Hiyama cross-coupling
some of them have been also used for Hiyama cross-coupling
reaction. Among heterogeneous Pd sources, palladium acti-
vated on carbon (Pd/C) is a commercially available, inexpen-
sive and very stable under acid and basic conditions. Recently,
11
reaction in presence of fluoride anion . However, phosphine
ligands are undesirable because of their toxicity and air as
well as moisture sensitive with conversion to, e.g., phosphine
oxide species and the requirement of corrosive fluoride anion
5
different coupling procedures for carbon-carbon, carbon-
oxygen and carbon-nitrogen bond formation in the presence
of Pd/C have been developed. Pd/C-catalyzed Hiyama
coupling reactions of aryl halides including ligand-free fashion
6
,9,10
for the activation of organosilanes . The potential of the

1
016 Mittapelly et al.
Asian J. Chem.
1
3c
1
were also reported , but they have limited scope with low
availability of substrates or the use of highly polar organic
2-Methyl-biphenyl (Table-2, entry 7): H NMR (300
MHz, CDCl ): δ 2.26 (s, 3H), 7.17-7.22 (m, 4H), 7.26-7.31
(m, 3H), 7.34-7.39 (m, 2H). C NMR (75 MHz, CDCl ): δ
3
14
13
solvents .
We report herein, on the application of Pd/C for the
Hiyama cross-coupling of aryl halides with aryl siloxanes in
the presence of NaOH as the base under aqueous conditions
3
20.4, 125.7, 126.7, 127.2, 128.0, 129.1, 129.7, 130.2, 135.3,
+
141.9. EI MS (m/z): 168 (M ).
1
4-Fluoro-biphenyl (Table-2, entry 9): H NMR (300
(
Scheme-I).
MHz, CDCl
3
): δ 7.07-7.13 (m, 2H), 7.27-7.32 (m, 1H), 7.36-
13
7
.41 (m, 2H), 7.47-7.53 (m, 4H). C NMR (75 MHz, CDCl ):
3
R2
δ 115.4, 115.7, 126.9, 127.2, 128.6, 128.8, 137.3, 140.2. EI
MS (m/z): 172 (M ).
+
Br
Si(OR)
3
3
3
mol % Pd/ C
equi v NaOH
1
1-Biphenyl-4-yl-ethanone (Table-2, entry 10): H NMR
+
R
1
R
2
R1
(300 MHz, CDCl ): δ 2.62 (s, 3H), 7.34-7.38 (m, 1H), 7.41-
3
H
2
O
7.45 (m, 2H), 7.58 (d, 2H, J = 7.9 Hz), 7.65 (d, 2H, J = 8.9
3 2 5
R = CH or C H
13
Hz), 8.00 (d, 2H, J = 8.9 Hz). C NMR (75 MHz, CDCl
3
): δ
Scheme-I
2
1
6.5, 127.1, 127.2, 128.2, 128.8, 128.9, 135.7, 139.8, 145.7,
+
97.6. EI MS (m/z): 196 (M ).
4-Nitro-biphenyl (Table-2, entry 11): H NMR (300
MHz, CDCl ): δ 7.40-7.50 (m, 3H), 7.59 (d, 2H, J = 8.3 Hz),
.72 (d, 2H, J = 8.3 Hz), 8.30 (d, 2H, J = 9.0 Hz). C NMR
75 MHz, CDCl ): δ 124.0, 127.3, 127.7, 128.8, 129.1, 138.7,
47.6. EI MS (m/z): 199 (M ).
Biphenyl-4-carbaldehyde (Scheme 2): H NMR (300
MHz, CDCl ): δ 7.37-7.49 (m, 3H), 7.58-7.62 (m, 2H), 7.72
d, 2H, J = 8.3 Hz), 7.93 (d, 2H, J = 8.3 Hz). C NMR (75
MHz, CDCl ): δ 127.3, 127.6, 128.4, 128.9, 130.2, 130.7,
35.1, 147.2, 191.9. EI MS (m/z): 282 (M ).
,4',5,6-Tetramethoxybiphenyl-2-carbaldehyde
Scheme-II): IR (neat): 2940, 1683, 1587, 1464, 1324, 1141,
1
EXPERIMENTAL
3
Experimental procedure for the Hiyama cross-coupling
reaction: A mixture of aryl bromide (1 mmol), aryl siloxane
1.2 mmol), NaOH (3 mmol), Pd/C catalyst (2 mol % of Pd)
13
7
(
1
3
(
+
and distilled water (3 mL) was taken in a round-bottomed flask
and stirred at 100 ºC for appropriate time.After completion of
the reaction (monitored by TLC) the catalyst was easily sepa-
rated from the reaction mixture with simple filtration. After
removing the solvent, the crude material was chromatographed
on silica gel to afford the pure product. The spectroscopic data
of all known compounds were identical to those reported in
the literature.
1
3
13
(
3
+
1
4
(
-1
1
1087, 996 cm . H NMR (300 MHz, CDCl ): δ 3.56 (s, 3H),
3
Spectroscopic data for the products
3.86 (s, 3H), 3.96 (s, 3H), 3.97 (s, 3H), 6.93 (d, 2H, J = 8.3
13
1
Hz), 7.22 (d, 2H, J = 9.0 Hz), 7.29 (s, 1H), 9.63 (s, 1H). C
NMR (75 MHz, CDCl ): δ 55.1, 55.9, 60.8, 60.9, 105.0, 113.3,
Biphenyl (Table-2, entry 1): H NMR (300 MHz,
3
CDCl ): δ 7.67-7.32 (m, 2H), 7.36-7.42 (m, 4H), 7.52-7.56
3
1
3
124.6, 129.7, 132.1, 134.1, 151.1, 152.7, 159.2, 191.3. ESI
(
1
m, 4H). C NMR (75 MHz, CDCl
3
): δ 127.1, 127.2, 128.7,
+
MS (m/z): 303 (M + H).
41.2. EI MS (m/z): 154 (M ).
1
1
4,4''-Dimethyl-[1,1';4',1'']terphenyl (Scheme-III): H
4
-Methoxy-biphenyl (Table-2, entry 2): H NMR (300
NMR (300 MHz, CDCl
7
3
): δ 2.35 (s, 6H), 7.19- 7.26 (m, 8H),
.33 (s, 4H). C NMR (75 MHz, CDCl ): δ 20.5, 125.7, 127.2,
128.8, 129.8, 130.3, 135.4, 140.3, 141.6. EI MS (m/z): 258 (M ).
MHz, CDCl
3
): δ 3.84 (s, 3H), 6.92 (d, 2H, J = 8.9 Hz), 7.24-
13
3
7
7
1
.27 (m, 1H), 7.35-7.38 (m, 2H), 7.47 (d, 2H, J = 8.9 Hz),
.50 (d, 2H, J = 7.9 Hz). C NMR (75 MHz, CDCl
+
13
3
): δ 55.3,
1
Tetraphenyl (Scheme-III): H NMR (300 MHz, CDCl
3
):
14.2, 126.6, 126.7, 128.1, 128.6, 133.7, 140.8, 159.1. EI MS
+
δ 2.47 (s, 9H), 7.24-7.48 (m, 6H), 7.55-7.75 (m, 6H), 7.82 (s,
(
m/z): 184 (M ).
-Methoxy-biphenyl (Table-2, entry 3): H NMR (300
MHz, CDCl ): δ 3.81 (s, 3H), 6.93-7.00 (m, 2H), 7.26-7.29
m, 3H), 7.34-7.38 (m, 2H), 7.47 (d, 2H, J = 6.9 Hz).
NMR (75 MHz, CDCl ): δ 55.5, 111.2, 120. 8, 126.8, 127.9,
28.5, 129.5, 130.8, 138.5, 156.4. EI MS (m/z): 194 (M ).
1
3
1
3H). C NMR (75 MHz, CDCl ): δ 21.1, 124.5, 127.1, 129.5,
3
2
+
1
37.2, 138.3, 142.1. EI MS (m/z): 348 (M ).
3
1
13
4'-Methoxy-4-methyl-biphenyl (Table-3, entry 2): H
NMR (300 MHz, CDCl ): δ 2.38 (s, 3H), 3.82 (s, 3H), 6.90 (d,
2H, J = 9.0 Hz), 7.16 (d, 2H, J = 8.3 Hz), 7.38 (d, 2H, J = 8.3
(
C
3
3
+
1
13
1
Hz), 7.44 (d, 2H, J = 9.0 Hz). C NMR (75 MHz, CDCl ): δ
3
3
-Methoxy-biphenyl (Table-2, entry 4): H NMR (300
MHz, CDCl ): δ 386 (s, 3H), 6.84 (dd, 1H, J = 2.0 Hz, 8.1
Hz), 7.07 (s, 1H), 7.13 (d, 1H, J = 7.4 Hz), 7.31 (t, 2H, J = 7.4
2
1
1.0, 55.3, 114.1, 126.5, 127.9, 129.4, 133.7, 136.3, 137.9,
3
+
58.8. EI MS (m/z): 198 (M ).
1
13
2,4'-Dimethyl-biphenyl (Table-3, entry 3): H NMR
Hz), 7.40 (t, 2H, J = 8.1 Hz), 7.55 (d, 2H, J = 6.8 Hz). C
NMR (75 MHz, CDCl ): δ 55.3, 112.6, 112.8, 119.6, 127.1,
27.4, 128.7, 129.7, 141.1, 142.7, 159.9. EI MS (m/z): 184
(
8
300 MHz, CDCl
H). C NMR (75 MHz, CDCl ): δ 20.5, 21.2, 125.7, 127.0,
3
): δ 2.25 (s, 3H), 2.41 (s, 3H), 7.14-7.72 (m,
3
13
3
1
+
+
128.7, 129.0, 129.8, 130.2, 136.3, 138.9. EI MS (m/z): 182 (M ).
(
M ).
1
1
4'-Methoxy-4-methyl-biphenyl (Table-3, entry 4): H
4
-Methyl-biphenyl (Table-2, entry 6): H NMR (300
MHz, CDCl ): δ 2.50 (s, 3H),7.35 (d, 2H, J = 7.9 Hz), 7.42 (t,
H, J = 7.6 Hz), 7.53 (t, 2H, J = 7.6 Hz), 7.60 (d, 2H, J = 8.1
3
NMR (300 MHz, CDCl ): δ 2.35 (s, 3H), 3.78 (s, 3H), 6.88-
3
6
.99 (m, 2H), 7.22-7.28 (m, 2H), 7.15 (d, 2H, J = 8.0 Hz),
1
13
13
7.35 (d, 2H, J = 8.0 Hz). C NMR (75 MHz, CDCl ): δ 21.1,
3
Hz), 7.69 (d, 2H, J = 7.2 Hz). C NMR (75 MHz, CDCl
3
): δ
5
5.4, 111.1, 120.7, 128.3, 128.6, 129.3, 130.7, 131.4, 131.5,
2
1.1, 126.9, 127.0, 128.6, 129.4, 136.9, 138.3, 141.1. EI MS
+
+
136.4, 156.4. EI MS (m/z): 198 (M ).
(
m/z): 168 (M ).

Vol. 26, No. 4 (2014)
Pd/C-Catalyzed Ligand-Free Hiyama Cross-Coupling Reaction of Aryl Halides 1017
Br
TABLE-2
Pd/C CATALYZED HIYAMA CROSS-COUPLING
OF DIFFERENT BROMOARENES WITH
H
O
a
OCH
3
TRIMETHOXYPHENYLSILANE
3
H CO
Si
H
OCH
3
2
2
mol% Pd/C
equiv TBAF
Entry
1
Aryl halide
Product
Time
4
Yield (%)
91
O
O
R
H
3
CO
H
!
,4-dioxane
O
Br
H
H
3
CO
H
3
CO
R = H or OCH
3
H
OCH
3
OCH
3
3
CO
Br
Br
OCH
3
2
4
6
4
85
76
82
Scheme-II
H3CO
H3CO
Br
OCH
3
H
3
CO
3
4
Si
Br
OCH
OCH3
Br
OCH3
3
2
3
mol% Pd/C
equiv NaOH
+
2
H O
Br
Br
OCH3
OCH3
OCH
3
H
3
CO
O
O
Br
O
O
Si
5
6
7
4
4
7
85
80
74
OCH
3
2
mol% Pd/C
equiv NaOH
+
3
Br
Br
Br
Br
2
H O
Scheme-III
RESULTS AND DISCUSSION
In an effort to develop a better catalytic system, initially
we investigated the coupling of 4-bromotoluene with tri-
methoxyphenylsilane in pure water at 100 °C under open air
by using different bases and the results are summarized in
Table-1. The bases used in this study includes NaOH, KOH,
Br
Br
8
9
4
4
90
88
Cl
F
Cl
F
Br
Br
2
LiOH, K CO
3
, K
3
PO
4
, Cs
2
CO
3
, KF, NaHCO
3
and NaOAc. The
10
4
92
base has a pronounced effect in this reaction and out of which
NaOH has been proven to the best base and KOH proven to
O
O
11
2
95
be equally good as NaOH (Table-1, entries 1-2). LiOH, K
Cs CO
Table-1, entries 3-6) and no product was formed with K
2
CO
3
,
O2N
O2N
2
3
and KF gave the product in low to moderate yields
a
Reaction conditions: aryl halide (1 mmol), trimethoxyphenylsilane
1.2 mmol), 2 mol % of Pd/C, NaOH (3 equiv) water (3 mL) stirred at
(
3
PO
4
,
(
NaHCO
3
and NaOAc (Table-1, entries 7). The control reaction
100 ºC
conducted under identical conditions and devoid of Pd/C gave
no coupled product, despite a prolonged reaction time.
results are presented in Table-3. Unsubstituted as well as
4
-methyl, 4-methoxy, 3-methoxy, 3,4-methylenedioxide
TABLE-1
substituted bromobenzenes underwent smooth reaction with
good yields when compared to 2-methyl and 2-methoxy
bromobenzenes (Table-3, entries 1-7). Furthermore, the reaction
was extended to other aryl halides having electron withdrawing
groups to generate biaryl products in good to excellent yields
SCREENING OF VARIOUS BASES FOR THE HIYAMA CROSS-
COUPLING REACTION BETWEEN 4-BROMOTOLUENE AND
a
TRIMETHOXYPHENYLSILANE
Entry
Base
NaOH
KOH
Yield (%)
1
2
3
4
5
6
80
72
34
16
14
41
(
Table-3, entries 8-11).
LiOH
K CO
Unfortunately, this catalytic system was ineffective for
2
3
the reaction with the aldehyde substituted bromo arenes under
the optimized reaction conditions (Scheme-II). However, best
results were obtained by changing the solvent from H
1
the Pd/C possessed good catalytic activity for both 4-bromo
benzaldehyde and 2-bromo-3,4,5-trimethoxy benzaldehydes.
The formed product 4,4',5,6-tetramethoxybiphenyl-2-
carbaldehyde is useful for the synthesis of antitumor agent
allocolchicine methyl ether.
To show the convenience of our approach for the synthesis
of multivalent structures, the coupling of 1,2-dibromobenzene
and 1,3,5-tribromobenzenes with p-methyl phenyltrimethoxysilane
Cs CO
2
3
KF
O to
a
2
Reaction conditions: 4-bromotoluene (1 mmol), trimethoxyphenyl-
silane (1.2 mmol), Pd/C (2 mol %), NaOH (3 equiv), water (3 mL)
stirred at 100 ºC for 6 h.
,4-dioxane and NaOHto TBAF. Under the above conditions
We observed that the best conditions developed for
trimethoxyphenylsilane and 4-bromotoluene were found to be
broadly applicable. When they were applied to a variety of
neutral, electron-rich and electron-poor aryl halides to inves-
tigate the synthetic scope of the reaction, the corresponding
biaryls were isolated in good to excellent yields. Our preparative

1
018 Mittapelly et al.
Asian J. Chem.
TABLE-3
Pd/C CATALYZED HIYAMA CROSS-COUPLING OF
DIFFERENT ARYLSILOXANES WITH 4-BROMOTOLUENE
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(
Entry
Aryl siloxane
Product
Time
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1
6
92
Si(OC2H5)3
Si(OC2H5)3
2
6
6
6
94
86
82
H3CO
H3CO
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OCH3
OCH3
5
6
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O
O
Si(OC2H5)3
O
O
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(
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metallics, 22, 987 (2003).
a
Reaction conditions: 4-bromotoluene (1 mmol), aryl siloxane (1.2
mmol), 2 mol % of Pd/C, NaOH (3 equiv) water (3 mL) stirred at 100 ºC.
was carried out under the optimized reaction conditions to
afford high yields of terphenyl and tetraphenyl respectively
7
.
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Dai and C. Fu, J. Am. Chem. Soc., 123, 2719 (2001).
(
Scheme-III).
Given the remarkably high levels of catalytic activity
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374 (1972); (b) W.A. Herrmann, V.P.W. Bohm and C. Reisinger, J.
4
Organomet. Chem., 576, 23 (1999).
displayed with Pd/C catalyst, we investigated its use for the
preparation of biaryls from 4-bromotoulene and different
phenyl trimethoxysilanes. As can be seen from the Table-3,
phenyl triethoxysilanes with electron-donating groups such
as methoxy, methyl and 3,4-methylenedioxy groups (Table-3,
entries 1,2 and 5) underwent smooth reaction with excellent
yields compared to those with electron-donating groups (Table-
9
1
.
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(
(
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3, entries 3 and 4) present in the ortho-position of the phenyl
ring.
Conclusion
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Y. Masuda, Synthesis, 2231 (2001).
In conclusion, we have developed a simple and efficient
method for the synthesis of biaryls via fluoride-free aqueous
Hiyama cross-coupling of bromoarenes with aryl siloxanes
using heterogeneous Pd/C as the catalyst under mild reaction
conditions. This protocol can be used to generate a diverse
range of biaryls in good to excellent yields.
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