Gold-catalyzed direct oxidative coupling reactions of non-activated arenes

Article abstract of DOI:10.1016/j.jorganchem.2008.11.016

A general gold-catalyzed oxidative homo- and hetero-coupling of arenes in mild conditions is described. This reaction gives moderate to excellent yield using PhI(OAc)₂ as an oxidant. The effects of temperature, solvent, oxidant and concentration of substrate in this process have also been studied in detail. The product identity and distribution as well as the substrate limitation give us insights into this type of gold catalysts. Depending upon the reaction conditions, the gold catalyst behaves as a simple Lewis acid, which produces amines from arenes using DIAD as an aminating reagent.

Full text of DOI:10.1016/j.jorganchem.2008.11.016

Journal of Organometallic Chemistry 694 (2009) 524–537
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Gold-catalyzed direct oxidative coupling reactions of non-activated arenes
Anirban Kar a, Naveenkumar Mangu a, Hanns Martin Kaiser a,b, Man Kin Tse a,b,
*
a Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
b University of Rostock, Center for Life Science Automation (CELISCA), Friedrich-Barnewitz-Str. 8, D-18119 Rostock-Warnemünde, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 June 2008
Received in revised form 3 November 2008
Accepted 4 November 2008
Available online 14 November 2008
A general gold-catalyzed oxidative homo- and hetero-coupling of arenes in mild conditions is described.
This reaction gives moderate to excellent yield using PhI(OAc)2 as an oxidant. The effects of temperature,
solvent, oxidant and concentration of substrate in this process have also been studied in detail. The prod-
uct identity and distribution as well as the substrate limitation give us insights into this type of gold cat-
alysts. Depending upon the reaction conditions, the gold catalyst behaves as a simple Lewis acid, which
produces amines from arenes using DIAD as an aminating reagent.
Keywords:
Gold
Ó 2008 Elsevier B.V. All rights reserved.
Coupling
Catalysis
Oxidation
CH-functionalization
1. Introduction
lective C–H bond activation with subsequent coupling reaction has
better atom efficiency [5]. However, direct aromatic C–H function-
In recent decades, transition metal-catalyzed coupling reactions
to construct aromatic C–C and C–X (X = N, O, S) bonds have gained
great attention of the scientific community and presently reached a
highly advanced status [1]. The classical way to this type of trans-
formation is the metal-mediated coupling reactions of the ‘‘pre-
activated” compounds, such as halogenated arenes [2]. The most
simple and convenient method to connect the electrophilic re-
agents (ArX) with the nucleophilic counter part, such as organome-
tallic derivatives (ArM), or amines, alcohols and thiols, is
undoubtedly the transition metal-catalyzed cross-coupling reac-
tions [1,3]. The major drawback of these reactions is the necessity
of an activating group on both or at least one of the coupling part-
ners, which may not be always easily available. Also this ‘‘pre-acti-
vation”, such as halogenation, sulfonate formation or preparation
of organometallic reagents, normally refers to an extra step to-
wards the final product.
Biaryls as well as aromatic amines constitute important struc-
tural motifs in natural products, pharmaceuticals, agrochemicals
and materials. Owing to the numerous appealing applications,
many efforts have been devoted to providing direct and efficient
processes for their preparation. Organometallic reagents from ele-
gant C–H bond functionalization methods save one synthetic step
[4] and direct metal, such as Pd, Rh and Ru etc., catalyzed regiose-
alization has not been reached its optimum level as practical
synthetic utility demands less expensive, highly efficient, environ-
mentally friendly catalytic systems. Recently, significant advances
have been made in the development of arylation of arenes, such as
indole, benzofuran and naphthalene, with benzenes in metal-cata-
lyzed reactions in the presence of oxidants [6]. Light mediated Ar–H
substitution [7] and Lewis acid [8] mediated oxidative coupling of
arenes are also impressive. On the other hand, metal-mediated di-
rect aromatic C–H activation followed by coupling with amines [9]
or Lewis acid-catalyzed amination of electron-rich arenes with elec-
trophilic nitrogen source to produce aromatic amines has been well
documented in the literature [10]. In general, use of inert atmo-
sphere or drastic conditions and limited substrate scope often ren-
ders the practicability of industrial usage of these types of
reactions. Therefore, the improvement of aromatic C–H bond trans-
formations under practical and mild conditions is one of the priority
tasks for modern organic chemists.
In recent years, gold has emerged as one of the most discussed
topic of the catalysis community [11]. Gold catalysts are known to
produce extraordinary results both in the fields of heterogeneous
and homogeneous catalysis. Although in the last few years, there
is a significant increase in scientific publication using gold as
homogeneous catalysts, especially as a ‘‘soft” Lewis acid to perform
C–C [12], C–N [13], C–O [14] and C–F [15] bond formation reac-
tions with multiple bonds, heterogeneous gold catalysts are still
dominant. Gold catalysts also have been employed in redox-type
reactions such as reduction [16], oxidation [17], diboration [18],
homo-coupling of boronic acids [19], cross-coupling reactions
* Corresponding author. Address: Leibniz-Institut für Katalyse e.V. an der,
Universität Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany. Tel.: +49
381 1281 193; fax: +49 381 1281 51193.
E-mail address: man-kin.tse@catalysis.de (M.K. Tse).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.11.016

A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
525
[20] and coupling of alkyl triflates with electron-rich arenes [21].
They have been used fruitfully for multi-component and cascade
reactions to generate complex structures [22]. Mechanistically,
there is still a concern associated with the role of protons in reac-
tions catalyzed by gold and other Lewis acids [23].
tetramethylbiphenyl using PhI(OAc)2 as the oxidant (Table 1). Ini-
tially we started with 5 mol% of HAuCl4 as catalyst with respect to
the oxidant employed. This reaction went smoothly to yield the
biphenyl in 65% at 55 °C (Table 1, entry 2) but remained unreactive
in the absence of the catalyst (Table 1, entry 1). Control experi-
ments without employing PhI(OAc)2, using catalytic and substoi-
chiometric amounts of HAuCl4 gave no product (not shown in
Table 1). As substantial amount of chlorination of p-xylene also ob-
served with 5 mol% of HAuCl4, reduction of the catalyst loading to
2 mol% slightly enhanced the product yield by decreasing the
amount of chlorine source (Table 1, entry 3). Further experiments
show that catalyst loading can be reduced down to 1 mol% with a
slight decrement in yield but with accretion in TON and TOF of the
reaction (Table 1, entry 4).
With 2 mol% of the catalyst loading, other gold catalysts such as
Au(OAc)3, AuCl(PPh3) and Au(OAc)PPh3 also showed moderate
activity, whereas AuCN remained completely inactive (Table 1, en-
tries 5, 7, 8 and 6). Though Lewis acid mediated oxidative coupling
of electron-rich arenes has been reported, low temperature
(ꢀ78 °C), inert gas (N2) and overstoichiometric amount of the Le-
wis acid (BF3 ꢁ Et2O) are necessary [8]. Typical Lewis acids like FeCl3
and BF3 ꢁ OEt2 did not work under our catalytic reaction conditions
(Table 1, entries 9 and 13). Catalysts like NH4FeCl4, AgNO3, CuCl2
also remained unreactive (Table 1, entries 10, 11 and 12). These re-
sults reveal that the reaction do not follow a simple electrophilic
substitution reaction pathway through a non-stabilized cationic
radical [8].
Gold is known to react with arenes to produce stable aryl-gold
complexes. In early landmark reports, these aryl complexes used to
be synthesized from Au(I)/(III) complexes with Grignard reagents
or organo-mercury compounds [24]. These Au(I) aryl complexes
can be further oxidized to their Au(III) derivatives [24a,24b]. C–H
bond activation of arenes with Au(III) complexes to produce gold
aryl complexes has also been reported in the literature, which is of-
ten stabilized by N-donating ligands [25]. In stoichiometric reac-
tions, this gold complex reacts with acetylenes to produce aryl
acetylenes and Au(I) species [26]. However, when this reaction
was performed in catalytic amount of gold in the presence of var-
ious oxidants, only hydroarylation of alkynes was observed [27]. It
should be noted that C–H bond activation and homo-coupling of
the coordinating ligand itself was determined [28]. On the basis
of these observations it was thought for long times that switching
over between two distinct oxidation states of gold in catalytic
reaction conditions will be fruitful to the chemical enterprise. Very
recently, it has been demonstrated that gold with a suitable ligand
system can also perform Suzuki [29] as well as Cu-free Sonogashira
[20a] coupling reactions. In our long term searching for efficient
C–H functionalization of arenes [30] and oxidation reaction sys-
tems [31], we thought that gold can be a good candidate to act
as catalyst for biaryl synthesis from arenes with a suitable oxidant
[32].
Solvent shows pivotal effects to this reaction and acetic acid ap-
peared to be the best solvent. Acids activate the gold catalyst. Only
Herein we present more detailed studies of the homo- and het-
ero-coupling of non-activated arenes on the basis of aromatic C–H
bond functionalization catalyzed by gold [33], and some initial
experiments on aromatic electrophilic amination reaction. These
results give us some insights on the diverse reaction mechanism.
Kozhevnikov et al. reported the oxidative homo-coupling of p-
xylene using Pd via a one electron transfer mechanism [34]. We
have chosen p-xylene as a model substrate to form 2,20,5,50-
small amounts of HOAc (56 lL) provided sufficient activity (66%)
for the reaction (Table 2, entry 8). For a more practical reaction
protocol for solid substrates, 1–2 mL of HOAc proved to be conve-
nient. When strong acid (TFA) was used as the solvent, the reaction
furnished rapidly but produced inferior results, possibly due to the
formation of polymers (Table 2, entries 6). Catalytic amounts of
TFA (5 mol%) with HAuCl4 (2 mol%) showed moderate activity (Ta-
ble 2, entry 9). On the other hand, when catalytic amounts of TFA
Table 1
Catalyst screening of oxidative homo-coupling of p-xylene.a
Me
Me
Me
catalyst
HOAc, 55 oC, 17 h
+
PhI(OAc)2
Me
Me
Me
2
1
d
Entry
Catalyst
Yield (%)b
TONc
TOF (hꢀ1
)
1
Nil
0
65
74
57
39
0
0
13
37
57
20
0
0
2e
3
HAuCl4
HAuCl4
HAuCl4
Au(OAc)3
AuCN
0.8
2.2
3.4
1.1
0
4f
5
6
7
8
9
AuCl(PPh3)
Au(OAc)PPh3
FeCl3
76
75
0
38
38
0
2.2
2.2
0
10
11
12
13
NH4FeCl4
AgNO3
CuCl2
BF3 ꢁ OEt2
0
0
0
0
0
0
0
0
0
0
0
0
a
Reaction conditions: PhI(OAc)2 (1.0 mmol), p-xylene (10.0 mmol), dodecane (55 lL, internal standard) and catalyst (0.02 mmol, 2.0 mol%) were heated in HOAc (1.0 mL) at
55 °C in air for 17 h.
b
Calibrated GC yields were reported; % yield = (no. of moles of biaryl)/(no. of moles of oxidant) ꢂ 100%.
Turnover number (TON) = (no. of moles of biaryl produced)/(no. of moles of catalyst).
Turnover frequency (TOF) = (no. of moles of biaryl produced)/[(no. of moles of catalyst) ꢂ (reaction time in hour)].
5 mol% of catalyst used.
c
d
e
f
1 mol% of catalyst used.

526
A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
Table 2
Solvent screening for oxidative homo-coupling of p-xylene.a
Me
Me
Me
2 mol% HAuCl4
Solvent, 55 oC, 17 h
+
PhI(OAc)2
Me
Me
Me
1
2
d
Entry
Solvent
Yield (%)b
TONc
TOF (hꢀ1
)
1
2
3
4
5
6
7
p-Xylene
CH3CN
CH3NO2
ClCH2CH2Cl
MeOH
TFA
HOAc
HOAc
TFA
Ac2O
58
0
12
42
3
<1
74
66
63
71
29
0
6
21
2
<1
37
33
32
36
1.7
0
0.4
1.2
0.1
<0.1
2.2
2.0
2.0
2.1
8e
9f
10
a
Reaction conditions: PhI(OAc)2 (1.0 mmol), p-xylene (10.0 mmol), dodecane (55 lL, internal standard) and HAuCl4 (3.2 mg, 0.02 mmol, 2.0 mol%) were heated in an
appropriate solvent (2.0 mL) at 55 °C in air for 17 h.
b
Calibrated GC yields were reported; % Yield = (no. of moles of biaryl)/(no. of moles of oxidant) ꢂ 100%.
c
d
e
f
Turnover number (TON) = (no. of moles of biaryl produced)/(no. of moles of catalyst).
Turnover frequency (TOF) = (no. of moles of biaryl produced)/[(no. of moles of catalyst) ꢂ (reaction time in hour)].
56
lL of HOAc used.
5 mol% TFA was used.
(5 mol%) was merely used without employing HAuCl4, it did not
give the desired product (no polymerization was observed in GC).
Both acetic acid anhydride and HOAc produced the desired biaryl
in comparable yields, when they were used as the solvent (Table
2, entry 7 and 10). These results imply that water in the reaction
mixture does not affect our system very much. The reaction can
also be carried out in the presence of non-coordinative solvents
like 1,2-dichloroethane and the substrate, p-xylene itself but with
comparatively lower yield (Table 2, entries 1 and 4). As HOAc was
generated during the reaction, the reaction may activate itself.
With strongly coordinative solvents like CH3CN and MeNO2 (Table
2, entries 2 and 3), either there was no reaction or the yield was
very poor, suggesting that the reduced Lewis acidity may be the
reason for this.
Amongst the oxidant used, PhI(OAc)2 was found to be the best
oxidant of this reaction (Table 3, entries 1). PhI(OCOCF3)2, a suit-
able reagent for Lewis acid mediated biaryl formation reactions,
gave slightly lower productivity in our model reaction (Table 3, en-
try 2). Hypervalent iodine seems participating in the reaction as
well. Indeed only very low yield of product was detected, PhI with
peracetic acid, a formal in situ generation method for PhI(OAc)2,
gave 3% of the biphenyl while peracetic acid alone did not produce
any coupling product. Other conventional oxidants such as K2S2O8,
OxoneÒ and Cu(OAc)2 did not work at all (Table 3, entries 2–6).
To improve the effectiveness of the gold catalytic system, the
concentration effect was examined using the preliminary opti-
mized reaction conditions (Table 4). The reaction is dependent on
the concentration of substrate, mainly because of the formation
of undesired oligomers observed by GC–MS (Table 4, entries 1,
4–6). When the concentration of the substrate such as p-xylene
and benzene was increased to 20-fold compared to the oxidant,
the yield of the corresponding homo-coupled product was also in-
creased substantially especially in the latter case (Table 4, entries 6
and 9). While temperature effect is insignificant to electron-rich
p-xylene (Table 4, entries 1–3), it is beneficial to non-activated
benzene (Table 4, entries 7 and 8). With these reaction conditions,
various non-activated arenes were coupled to test the effectiveness
of the gold catalytic system.
While electron-rich substrates work well at 55 °C, neutral or
electron deficient substrates need slightly higher temperature
(95 °C). In general, the reaction works smoothly in good to excel-
lent yield. Even though slightly higher concentration (10 equiva-
lents to the oxidant) of arene is used to get optimized yield, the
excess starting material can be recovered and reused. For example,
7.5 equivalents of 4-bromo-2-methylanisole with respect to
PhI(OAc)2 were recovered after the reaction (Table 5, entry 10).
The regioselectivity of the reaction follows typical electrophilic
aromatic substitution pattern. A range of arenes worked compara-
bly well under our reaction conditions to give the corresponding
biaryls in moderate to good yields (Table 5). Even difficult sub-
strates such as 4-nitroanisole, which was reported to be unreactive
in Lewis acid mediated oxidative coupling [35], produced the cor-
responding biaryl in moderate yield (Table 5, entry 12). Highly
electron deficient substrates like 1,3-dicholorobenzene also re-
acted at elevated temperature (Table 5, entry 16).
A wide range of functional groups has been tolerated by the
present reaction protocol. All halogens survived and kept intact
during the course of the reaction. To the best of our knowledge,
neither palladium- nor Lewis acid-catalyzed reactions can main-
tain the reactivity tolerating all halogens (Table 5, entries 5–11).
Some C–H functionalization reactions exhibit such high halogen
group preservation [4a]. Methoxide and ester groups also survived
and worked equally well in our reaction conditions (Table 5, en-
tries 13 and 14). The electron-rich heterocycle, thiophene also cou-
pled to the corresponding product in single regioisomeric form in
moderate yield (Table 5, entry 15). One of the drawbacks for this
protocol is the compatibility with strong coordinating groups. Sub-
strates containing functionalization such as N,N-dimethylbenzyl
amine, 2-phenyl pyridine, N-acetyl aniline, aliphatic aromatic ke-
tones did not give any desired product. Although auration of 2-
phenyl pyridine is reported in the literature [24c], it did not give
any desired product. Electron-rich mesitylene did not produce
the desired homo-coupled product possibly due to the increased
steric bulk in the substrate.
Nevertheless, the present protocol is very easy to handle. It can
be managed in ambient conditions and is not necessary to protect

A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
527
Table 3
Oxidant screening of oxidative homo-coupling of p-xylene.a
Me
Me
Me
2 mol% HAuCl4
HOAc, 55 oC, 17 h
+
Oxidant
Me
Me
Me
1
2
d
Entry
Oxidant
Yield (%)b
TONc
TOF (hꢀ1
)
1
2
PhI(OAc)2
PhI(OCOCF3)2
74
69
37
35
2.2
2.1
O
3
0
0
0
O
I
OH
4
5
6
7
45% IBX
<1
1
0
3
0
<1
<1
0
2
0
<0.1
<0.1
0
<0.1
0
Dess-Martin
35% CH3CO3H
PhI + 35% CH3CO3H
DMSO
8
9
10
11
K2S2O8
0
0
0
0
0
0
0
0
0
OxoneÒ
Cu(OAc)2
a
Reaction conditions: oxidant (1.0 mmol), p-xylene (10.0 mmol), dodecane (55 lL, internal standard) and HAuCl4 (3.2 mg, 0.02 mmol, 2.0 mol%) were heated in HOAc
(1.0 mL) at 55 °C in air for 17 h.
b
Calibrated GC yields were reported; % yield = (no. of moles of biaryl)/(no. of moles of oxidant) ꢂ 100%.
c
Turnover number (TON) = (no. of moles of biaryl produced)/(no. of moles of catalyst).
d
Turnover frequency (TOF) = (no. of moles of biaryl produced)/[(no. of moles of catalyst) ꢂ (reaction time in hour)].
Table 4
Concentration effects on Au-catalyzed oxidative homo-coupling of arenes.a
R
R
R
2 mol% HAuCl4
+
PhI(OAc)2
HOAc, temp., 17 h
R
R
R
R = H, Me
Entry
1
ArH
ArH:PhI(OAc)2:HOAcb
Major product
Temperature (°C)
Yield (%)c
74
10:1:17
55
Me
Me
Me
Me
Me
2
Me
1
2
3
4
5
6
1
1
1
1
1
10:1:17
10:1:17
10:1:3
10:1:9
20:1:17
2
2
2
2
2
75
95
55
55
55
74
70
31
52
81
7
10:1:17
55
34
3
4
8
9
3
3
10:1:17
20:1:17
4
4
95
95
54
71
a
Reaction conditions: oxidant (1.0 mmol), p-xylene, dodecane (55 lL, internal standard) and HAuCl4 (0.02 mmol, 2.0 mol%) were heated in the appropriate solvent (1.0 mL)
and temperature in air for 17 h.
b
Molar ratio.
GC yields.
c
the mixture under inert atmosphere or pre-treat of the solvent or
substrate.
Exploration of oxidative hetero-coupling of arenes using our
protocols showed interesting concentration effects. With equal

528
A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
Table 5
Au-catalyzed oxidative homo-coupling of arenes.a
R3
R2
R1
R3
R2
R3
R2
2 mol% HAuCl4
+
PhI(OAc)2
HOAc, temp., 17 h
R1
R1
Entry
1c
ArH
Major product
Temperature (°C)
Yield (%)b
71d
95
3
4
Me
Me
Me
2c
55
81d
Me
Me
Me
Me
1
2
Me
Me
Me
3
55
75e
Me
Me
6
5
tBu
Me
Me
4
95
62
tBu
tBu
Me
8
7
F
OMe
F
5
95
68d
MeO
MeO
F
MeO
9
10
F
F
MeO
OMe
6
55
63f
F
11
12
F
F
F
7
95
63g
OMe
MeO
MeO
13
14
Cl
OMe
Cl
8
95
68
MeO
15
Cl
MeO
16
(continued on next page)

A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
529
Table 5 (continued)
Entry
9
ArH
Major product
Temperature (°C)
Yield (%)b
56
95
Br
OMe
Br
MeO
Br
MeO
17
18
Br
Me
OMe
Br
10
95
56h
MeO
Me
Br
MeO
Me
19
20
I
I
11
95
79i
MeO
OMe
MeO
I
21
22
OMe
NO2
NO2
12
13
14
95
95
95
38
O2N
MeO
24
MeO
23
OMe
O
MeO
O
MeO
OMe
O
86j
MeO
25
MeO
26
Me
OMe
O
O
OMe
78
Me
O
Me
S
MeO
S
27
28
Me
15
95
31
S
Me
Cl
Me
30
31
Cl
Cl
Cl
Cl
16
95
15k
Cl
33
32
(continued on next page)

530
A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
Table 5 (continued)
Entry
17
ArH
Major product
–
Temperature (°C)
Yield (%)b
0
95
Me
N
Me
34
18
19
–
–
95
95
0
0
N
35
O
HN
Me
36
O
Me
20
–
–
95
95
0
0
37
Me
Me
Me
21
38
a
Reaction conditions: oxidant (1.0 mmol), arene (10.0 mmol), dodecane (55 lL, internal standard) and HAuCl4 (0.02 mmol, 2.0 mol%) were heated in HOAc (1.0 mL) at
appropriate temperature in air for 17 h.
b
Isolated yields based on the oxidant used.
GC yields.
20.0 mmol of arene was used.
An isomer mixture was isolated; product ratio = 89:11 on GC-FID.
c
d
e
f
54% of para–para coupled product and 9% of para–ortho coupled product were isolated.
An isomer mixture was isolated; product ratio = 24:49:27 on GC-FID.
g
h
i
An isomer mixture was isolated; product ratio = 88:12 (1H NMR).
69% of para–para coupled product and 10% of para–ortho coupled product were isolated.
74% of para–para coupled product was isolated and 12% of para–ortho coupled product were observed.
An isomer mixture was isolated; product ratio = 94:6 on GC-FID.
j
k
amounts of para-haloanisole and benzene, nearly equal amount of
valent iodine salt and a Lewis acid was already reported in the lit-
erature [36], which supports our observation during the homo-
coupling experiments with para-iodoanisole. But surprisingly, the
same substrate in hetero-coupling conditions produced different
amount of homo- and hetero-coupling product of para-iodoanisole
together with the formation of biphenyl (4) but not the acetoxylat-
ed product.
Gold catalysts can be extended to C–N bond formation [37]. The
same type of C–N bond formation reaction of electron-rich arenes
was reported in the literature promoted mainly with stoichiome-
tric amount of Lewis acids [10]. In a model reaction C–N bond
formation of p-xylene catalyzed by gold catalysts using diisopro-
pylazodicarboxylate (DIAD) as a nitrogen source was performed
(Table 7). To our delight, 5% HAuCl4 catalyzed the reaction to yield
the major product in 31% at 55 °C using MeNO2 as solvent (Table 7,
entry 1).
the homo-coupling product of biphenyl and the hetero-coupling
product of phenylanisole was observed, whereas the yield of bis-
anisole was only in a few percent (Table 6, entries 3, 9, 15). Clearly
it can be imagined that the activation of benzene occurs in the ini-
tial step and the reactive intermediate is then trapped by another
arene. Hence the biphenyl to phenylanisole ratio is close to the
concentration ratio of benzene and anisole. Increasing the amount
of benzene from 1 to 10 equivalents to PhI(OAc)2 caused increment
of biphenyl, as expected (Table 6, entries 1–4).
Higher concentration of arenes resulted in a better total yield.
The best result was obtained when a ratio of 15:6:1 of para-bromo-
anisole:benzene:PhI(OAc)2 was performed, in which a total yield of
95% was attained with 55% of cross-coupling product (Table 6, en-
try 12). On the other hand, in the case of para-iodoanisole, ortho-
acetoxylated product with respect to the methoxy goup, which
was the major product in homocouplig reaction conditions, was
not observed (according to GS–MS spectra of the crude reaction
mixtures). The formation of such acetoxylated product with hyper-
But in sharp contrast to the C–C bond formation reaction, C–N
bond formation did not proceed when Au(OAc)3, AuCl(PPh3) or
AuCN were used as catalyst, whereas AuCl3 showed comparable

A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
531
Table 6
Au-catalyzed oxidative hetero-coupling of arenes.a
4
+
OMe
OMe
2 mol% HAuCl4
+
+
PhI(OAc)2
HOAc, 95 °C, 17 h
X
X
X = Cl 40, Br, 41, I 42
+
OMe
X
X
MeO
X = Cl 16, Br, 18, I 43
Entry
X
Halo-anisole:benzeneb
Hetero-coupled product
Homo-coupled product
Biphenyl (4) (%)c
Hetero:homo:4 (%)d
(40, 41 or 42) (%)c
(16, 18 or 43) (%)c
1
2
3
4
5
6
7
8
Cl
Cl
Cl
Cl
Cl
Cl
Br
Br
Br
Br
Br
Br
I
5:1
5:2
5:5
5:10
10:4
15:6
5:1
5:2
5:5
5:10
10:4
15:6
5:1
23
32
30
23
43
46
27
42
37
29
50
55
15
26
25
20
36
41
17
7
3
4
18
32
41
19
22
9
27
43
60
30
30
3
49:40:11
52:12:36
41:5:53
0
32:0:68
10
11
15
7
3
1
56:15:29
54:15:31
45:37:18
48:13:39
38:4:58
9
10
11
12
13
14
15
16
17
18
27:2:71
8
50:13:37
51:14:35
48:40:12
51:16:33
41:7:52
25:2:73
53:21:26
48:13:39
11
nde
nd
nd
nd
nd
nd
I
I
I
I
5:2
5:5
5:10
10:4
15:6
16
29
54
17
15
I
a
Reaction conditions: oxidant (1.0 mmol), appropriate amounts of arenes, dodecane (55
(1.0 mL) at 95 °C in air for 17 h.
lL, internal standard) and HAuCl4 (0.02 mmol, 2.0 mol%) were heated in HOAc
b
No. of moles of anisole: no. of moles of benzene.
Calibrated GC yields based on the oxidant used.
GC peak area ratio of corresponding products.
Not determined.
c
d
e
reactivity (Table 1, entries 2, 3, 4 and 5). Further solvent screening
revealed that, MeNO2 is the solvent of choice, whereas polar protic
solvent like AcOH and MeOH, coordinative CH3CN, and non-polar
aprotic 1,2-dichloroethane gave inferior results (Table 1, entries
6–10). However, using 5 mol% of BF3 ꢁ Et2O instead of HAuCl4, a
similar yield was given (Table 1, entry 11), which suggests the
present aromatic C–N bond formation passes through a Lewis
acid-catalyzed reaction mechanism. This type of gold-catalyzed
electrophilic aromatic C–H functionalization is mechanistically en-
tirely different from the aforementioned oxidative homo-coupling
of arenes.
Some mechanistic insights can be drawn from this diverse reac-
tivity of gold catalysts. It should be noted that both AuCl(PPh3),
Au(OAc)PPh3 and HAuCl3 worked with same efficiency under our
oxidative conditions and this strongly supports the fact that Au it-
self but not Lewis acid is the exact C–H functionalization catalyst
[14j,38]. Lewis acid mediated oxidative coupling reactions of elec-
tron-rich arenes using hypervalent iodine salts could perform at as
low temperature as ꢀ78 °C and a cationic radical species has been
proposed as the reaction intermediate [8b]. In the aromatic C–N
bond formation process both BF3 ꢁ OEt2 and HAuCl4 worked equally
well, establishing that it is likely a Lewis acid-catalyzed process,
while no biaryl was observed with 2 mol% BF3 ꢁ OEt2 in the present
oxidative homo-coupling system. Moreover, nitro-substituted ani-
sole did not work in the Lewis acid systems, while it worked mod-
erately in our case. Hence, direct participation of cationic radicals is
not very likely. But the regioselectivity in the present homo-cou-
pling reaction protocol strictly follows typical electrophilic aro-
matic substitution pattern. During the screening process of
homo-coupling of p-xylene, a trace amount of an unidentified com-
pound with a molecular mass of 212, which corresponds to the not
oxidized intermediate to bixylyl was observed. Participation of
gold stabilized cationic radical species or electrophilic metalation
like conventional Pd(II) or Pt(II) cannot be entirely ruled out. It
has been recently reported that oxidative addition of aryliodides
is possible with gold(I) complexes. But under our conditions, the
substrate with the weakest carbon halogen bond (C–I) coupled
smoothly with intact preservation of iodo-group in the product
(Table 5, entry 11), which implies that high-valent gold is the ma-
jor catalyst [14j,20,38]. Knowing the distinct difference of reactiv-

532
A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
Table 7
Catalyst and solvent screening for electrophilic amination of p-xylene.a
Me
Me
i
i
CO2 Pr
CO2 Pr
N N
iPrO2C
5 mol% Catalyst
+
N
Solvent, 55 °C, 17 h
i
NHCO2 Pr
Me
Me
44
Entry
Catalyst
Solvent
Yield of major isomer (%)b
Major:minor (%)c
1
2
3
4
5
6
7
8
HAuCl4
AuPPh3Cl
AuCl3
Au(OAc)3
AuCN
HAuCl4
HAuCl4
HAuCl4
HAuCl4
HAuCl4
BF3.OEt2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3CN
p-Xylene
ClCH2CH2Cl
AcOH
31
0
30
0
85:15
0:0
85:15
0:0
0
0:0
14
11
14
22
0
80:20
83:17
84:16
84:16
0:0
9
10
11
MeOH
CH3NO2
31
85:15
a
Reaction conditions: DIAD (1.0 mmol), p-xylene (10.0 mmol), dodecane (55
solvent (1.0 mL) at 55 °C in air for 17 h.
l
L, internal standard) and catalyst (0.05 mmol, 5.0 mol%) were heated in the appropriate
b
Calibrated GC yields.
GC peak area ratio of corresponding products.
c
ity between the C–C bond formation and C–N bond formation pro-
cess, it strongly suggests that rather than a simple aromatic elec-
trophilic substitution, it follows a complicated pathway.
The reaction mixture was extracted with EtOAc (3 ꢂ 10 mL) and
the combined organic layer was washed with saturated NaHCO3
(2 ꢂ 20 mL), brine (10 ml), dried over Na2SO4, filtered and concen-
trated. The residue was purified by column chromatography to af-
ford the desired product.
In summary, a new general gold-catalyzed oxidative coupling
of arenes was reported. Hetero-coupling was shown for the first
time possible. This reaction can be simply handled in air and no
pre-treatment of substrate and solvent is necessary. Interestingly
our reaction protocol activated by a suitable acidic solvent and
does not require any Ag salt to enhance the reactivity.[39]
Remarkable functional groups tolerance has been shown in our
reaction conditions. The reaction proceeds via a double CH-func-
tionalization, which is in principle the most efficient process for
the synthesis of biaryls. From the reaction pattern showed by
electrophilic C-N bond formation of p-xylene, the mechanism of
gold-catalyzed CH-functionalization is still unclear and an
interesting area. Studies of the reaction mechanism are undoubt-
edly a currently fruitful area for the next generation of gold
catalysis.
2.2.1. 2,5,20,50-Tetramethylbiphenyl (2) [40]
Me
Me
Me
Me
Rf = 0.63 (hexane); white solid; 1H NMR (300.1 MHz, CDCl3):
d = 2.04 (s, 6H), 2.35 (s, 6H), 6.90-7.00 (m, 2H), 7.05-7.2
(m, 4H); 13C NMR (75.5 MHz, CDCl3): d = 19.30, 20.93, 127.70,
129.59, 129.94, 132.59, 134.82, 141.58; ATR-IR (cmꢀ1): 3017m,
2917m, 2859s, 1610m, 1501s, 1446w, 1376s, 1145s, 1037w,
890s, 882s, 812s, 754s, 7646s, 475m; MS (EI): m/z (rel. int.) 211
(11), 210 (66), 196 (15), 195 (100), 180 (33), 179 (23), 178 (21),
165 (31); HRMS calcd. for C16H18 m/z 210.1403, found m/z
210.1399.
2. Experimental
2.1. General
NMR spectra were recorded on a Bruker ARX 300 spectrometer,
operating at 300 MHz for 1H NMR, 75 MHz for 13C NMR were re-
ported downfield from CDCl3 (d: 7.27 ppm) for 1H NMR. For 13C
NMR, chemical shifts were reported in the scale relative to the sol-
vent of CDCl3 (d: 77.0 ppm) used as an internal reference. Mass
spectra were in general recorded on an AMD 402/3 or a HP
5989A mass selective detector. Column chromatography was per-
formed with silica gel Fluka 60 (70-230 mesh ASTM).
2.2.2. 2,4,20,40-Tetramethylbiphenyl (6) [41]
Me
Me
Me
Me
Rf = 0.60 (hexane); colorless oil; 1H NMR (300.1 MHz, CDCl3):
d = 2.05 (s, 6H), 2.39 (s, 6H), 6.90-7.20 (m, 6H); 13C NMR
(75.5 MHz, CDCl3): d = 19.79, 21.11, 126.19, 129.43, 130.52,
135.80, 136.51, 138.63; ATR-IR (cmꢀ1): 3013w, 2919w, 2858w,
1612s, 1487s, 1443w, 1377s, 1233s, 1035w, 1007s, 874s, 815s,
2.2. General procedure for HAuCl4 catalyzed homo-coupling of arenes
To a 10 mL vial arene (10 mmol), PhI(OAc)2 (1 mmol), HAuCl4
(0.02 mmol) and acetic acid (1 mL) were added. The mixture was
stirred for 17 h at 55 °C and then quenched with water (10 mL).

A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
533
768s, 724s; MS (EI): m/z (rel. int.) 211 (15), 210 (90), 209 (7), 195
(100), 180 (39), 179 (27), 178 (22), 165 (35), 89 (11); HRMS calcd.
for C16H18 m/z 210.1403, found m/z 210.1402.
(73), 236 (15), 235 (100), 207 (14), 192 (17), 164 (17); HRMS
calcd. for C14H12F2O2 m/z 250.0800, found m/z 250.0800. Elemental
Anal. Calc. for C14H12F2O2: C, 67.20; H, 4.83. Found: C, 67.64; H,
4.67%.
2.2.3. 5,50-Di-tert-butyl-2,20-dimethylbiphenyl (8) [42]
2.2.6. 3,30-Difluoro-2,40-dimethoxybiphenyl (minor isomer)
Me
tBu
F
OMe
F
OMe
tBu
Me
Rf = 0.64 (hexane); colorless oil; 1H NMR (300.1 MHz, CDCl3):
d = 1.34 (s, 18H), 2.05 (s, 3H), 7.18–7.25 (m, 4H), 7.28–7.33 (m,
2H); 13C NMR (75.5 MHz, CDCl3): d = 19.37, 31.45, 34.41, 123.83,
126.64, 129.44, 132.78, 141.50, 148.30; ATR-IR (cmꢀ1): 2960w,
2867s, 1607s, 1491s, 1463m, 1391w, 1260m, 1202s, 1151m,
1113s, 894s, 847s, 818s, 738m, 682m; MS (EI): m/z (rel. int.) 295
(5), 294 (22), 280 (23), 279 (100), 57 (11); HRMS calcd. for
C22H30 m/z 294.2342, found m/z 294.2343.
Rf = 0.21 (hexane); colorless oil; 1H NMR (300.1 MHz, CDCl3):
d = 3.72 (d, JHF = 1.5 Hz, 3H), 3.92 (s, 3H), 6.97–67.10 (m, 4H),
5
7.24 (ddd, J = 8.4, 2.1, 1.1 Hz, 1H), 7.30 (dd, J = 12.5, 2.2 Hz, 1H);
4
13C NMR (75.5 MHz, CDCl3): d = 56.22, 61.17 (d, JCF = 4.4 Hz),
4
2
113.01 (d, JCF = 1.9 Hz), 115.86 (d, JCF = 19.4 Hz), 116.99 (d,
2JCF = 19.4 Hz), 123.76 (d, JCF = 8.4 Hz), 124.96 (d, JCF = 3.7 Hz),
3
3
125.48 (d, 4JCF = 2.6 Hz), 130.22 (dd, JCF = 6.8, 3.0 Hz), 135.11 (unre-
2
2
solved dd), 145.04 (d, JCF = 10.8 Hz), 147.06 (d, JCF = 10.8 Hz),
1
1
151.93 (d, JCF = 245.2 Hz), 156.07 (d, JCF = 246.3 Hz); MS (EI): m/
z (rel. int.) 251 (17), 250 (100), 235 (33), 220 (34), 204 (39), 175
(12), 164 (24); HRMS calcd. for C14H12F2O2 m/z 250.0800, found
m/z 250.7976.
2.2.4. 5,50-Difluoro-2,20-dimethoxybiphenyl (10) [43]
OMe
F
2.2.7. Mixtures of homo-coupled isomers of 3-fluoroanisole (14)
F
MeO
F
F
Rf = 0.14 (hexane:ethyl acetate = 100:3); white solid; m.p. =
123–124 °C (hexane); 1H NMR (300.1 MHz, CDCl3): d = 3.73 (s,
6H), 6.88 (dd, J = 8.9, 4.6 Hz, 2H), 6.96 (dd, J = 8.9, 2.8 Hz, 2H),
7.00 (ddd, J = 8.8, 8.0, 3.2 Hz, 2H); 13C NMR (75.5 MHz, CDCl3):
OMe
MeO
3
2
d = 56.29, 112.08 (d, JCF = 8.4 Hz), 114.81 (d, JCF = 22.6 Hz),
2
118.11 (d, JCF = 23.2 Hz), 127.77 (dd, JCF = 8.0, 1.6 Hz), 153.034
4
1
(d, JCF = 1.9 Hz), 156.64 (d, JCF = 238.2 Hz); ATR-IR (cmꢀ1):
3126w, 3072w, 3020w, 2958w, 2940w, 2910w, 2837w, 1869w,
1592w, 1506m, 1486s, 1464m, 1441m, 1425m, 1406w, 1293m,
1271m, 1256m, 1245s, 1219m, 1180s, 1158s, 1136m, 1035s,
1023s, 947m, 937w, 868s, 844m, 818s, 749s, 722s, 696m; MS
(EI): m/z (rel. int.) 251 (14), 250 (100), 235 (24), 220 (40), 204
(32), 164 (10); HRMS calcd. for C14H12F2O2 m/z 250.0800, found
m/z 250.0798. Elemental Anal. Calc. for C14H12F2O2: C, 67.20; H,
4.83. Found: C, 67.02; H, 4.68%.
Rf = 0.17 (hexane); colorless oil of isomer mixture; 1H NMR
(300.1 MHz, CDCl3): d = 3.68 (s, 6H, 1st isomer, 21%), 3.71 (s, 3H,
2nd isomer, 49%), 3.75 (s, 3H, 2nd isomer, 49%), 3.76 (s, 6H, 3rd iso-
mer, 30%), 6.59–6.71 (m), 7.05–7.23 (m); GC–MS (40 °C, 2 min.;
15 °C min.ꢀ1; 280 °C, 12 min.) [m/z (rel. int.)] tr = 12.59 min. [251
(15), 250 (100), 235 (15), 220 (41), 204 (39), 175 (11), 164 (12)],
13.27 min. [251 (15), 250 (100), 235 (29), 220 (17), 207 (11), 204
(23), 175 (10), 164 (16)], 13.93 min. [251 (15), 250 (100), 236
(10), 235 (69), 207 (29), 192 (12), 164 (15)].
2.2.5. 3,30-difluoro-4,40-dimethoxybiphenyl [major isomer] (12) [44]
2.2.8. 5,50-Dichloro-2,20-dimethoxybiphenyl (16) [43,45]
F
OMe
MeO
Cl
MeO
OMe
F
Cl
Rf = 0.11 (hexane); white solid; m.p. = 155–156 °C (hexane); 1H
NMR (300.1 MHz, CDCl3): d = 3.85 (s, 6H), 6.90–6.95 (m, 2H), 7.13–
7.21 (m, 4H); 13C NMR (75.5 MHz, CDCl3): d = 56.33, 113.67 (d,
Rf = 0.29 (ethyl acetate:hexane = 1:19); white solid; m.p. = 109–
110 °C; 1H NMR (300.1 MHz, CDCl3): d = 3.77 (s, 6H), 6.90 (d,
J = 8.6 Hz, 2H), 7.21 (d, J = 2.8 Hz, 2H), 7.30 (dd, J = 8.6, 2.8 Hz,
2H); m/z (rel. int.) = 286 (11), 285 (9), 284 (6), 283 (15), 282
(100), 232 (49), 217 (19), 189 (11); 13C NMR (75.5 MHz, CDCl3):
d = 55.97, 112.23, 125.18, 127.94, 128.62, 131.01, 155.56; ATR-IR
(cmꢀ1): 3004m, 2934m, 2835s, 1766w, 1729w, 1590, 1499w,
2
3
4JCF = 2.6 Hz), 114.37 (d, JCF = 19.3 Hz), 122.17 (d, JCF = 3.3 Hz),
2
132.94 (dd, JCF = 6.5, 2.0 Hz), 146.94 (d, JCF = 10.3 Hz), 152.54 (d,
1JCF = 245.9 Hz); ATR-IR (cmꢀ1): 3051w, 3030w, 2977w, 2950w,
2922w, 2845w, 2582w, 2031w, 1618m, 1575m, 1499s, 1463s,
1440s, 1404m, 1303s, 1260s, 1209s, 1179s, 1133s, 1043s, 1013s,
863s, 839s, 800s, 760s; MS (EI): m/z (rel. int.) 251 (13), 250

534
A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
1487w, 1469m, 1443m, 1288w, 1271m, 1242b, 1230m, 1181s,
1147s, 1134s, 1096s, 1021s, 889s, 878, 865s, 810, 753s, 727m,
654s; HRMS calcd. for C14H12Cl2O2 m/z 282.0209, found m/z
282.0214.
1244s, 1183s, 1144w, 1049s, 1027w, 941s, 872w, 842s, 805w,
792w, 719s, 706s, 693s, 661s; MS (EI): m/z (rel. int.) 468 (3), 467
(16), 466 (100), 451 (42), 309 (149, 167 (12), 126 (18); HRMS calcd.
for C16H16I2O2 m/z 465.8921, found m/z 465.8919.
2.2.9. 5,50-Dibromo-2,20-dimethoxybiphenyl (18) [43,46]
2.2.12. 3,30-Diiodo-2,40-dimethoxybiphenyl [minor isomer]
OMe
MeO
Br
I
OMe
I
OMe
Br
Rf = 0.31 (ethyl acetate:hexane = 1:19); viscous liquid; 1H NMR
(300.1 MHz, CDCl3): d = 3.44 (s, 3H), 3.94 (s, 3H), 6.84-6.94 (m,
2H), 7.24–7.31 (m, 1H), 7.56 (dd, J = 8.5, 2.2 Hz, 1H), 7.75 (dd,
J = 7.9, 1.6 Hz, 1H), 7.56 (d, J = 2.2 Hz, 1H); 13C NMR (75.5 MHz,
CDCl3): d = 56.40, 60.29, 85.67, 93.15, 110.50, 126.19, 130.09,
131.11, 132.09, 133.83, 138.49, 139.61, 156.74, 157.62; ATR-IR
(cmꢀ1): 3001w, 2929m, 2837s, 1724s, 1594s, 1546m, 1492s,
1455m, 1413s, 1373s, 1281m, 1249m, 1233m, 1180s, 1146m,
1074s, 1053s, 1016m, 999w, 888s, 814s, 781m, 755s, 731s, 664s;
MS (EI): m/z (rel. int.) 468 (2), 467 (16), 466 (100), 324 (35), 309
(17), 139 (14), 126 (12); HRMS calcd. for C16H16I2O2 m/z
465.8921, found m/z 465.8921.
Rf = 0.28 (ethyl acetate:hexane = 1:19); white solid; m.p. = 105–
107 °C; 1H NMR (300.1 MHz, CDCl3): d = 3.78 (s, 6H), 6.85 (d,
J = 8.8 Hz, 2H), 7.34 (d, J = 2.6 Hz, 2H), 7.44 (dd, J = 8.8, 2.6 Hz,
2H); m/z (rel. int.) = 374 (49), 373 (16), 372 (100), 371 (9), 370
(51), 278 (41), 276 (41), 263 (25), 261 (27), 235 (16), 233 (15),
139 (20), 138 (12), 126 (27), 63 (12); 13C NMR (75.5 MHz, CDCl3):
d = 55.91, 112.48, 112.71, 128.35, 131.62, 133.77, 156.09; ATR-IR
(cmꢀ1): 3077s, 3017m, 2936w, 2835w, 1599w, 1584w, 1496w,
1479w, 1458m, 1435s, 1410w, 1377s, 1289s, 1257w, 1242w,
1221w, 1180w, 1148s, 1138s, 1082s, 1029w, 1018w, 883s, 868w,
842w, 815w, 806w, 742s, 724w, 670w; HRMS calcd. for
C14H12Br2O2 m/z 369.9199, found m/z 369.9196.
2.2.13. 2,20-Dimethoxy-5,50-dinitrobiphenyl (24) [49]
2.2.10. 5,50-dibromo-2,20-dimethoxy-3,30-dimethylbiphenyl (major
isomer) (20) [47]
OMe
MeO
NO2
Me
Br
OMe
MeO
Br
O2N
Rf = 0.16 (hexane:ethyl acetate = 8:2); yellow solid; m.p. = 266–
268 °C (hexane); 1H NMR (300.1 MHz, CDCl3): d = 3.90 (s, 6H), 7.07
(d, J = 9.2 Hz, 2H), 8.18 (d, J = 2.8 Hz, 2H), 8.32 (d, J = 9.2, 2.8 Hz,
2H); 13C NMR (75.5 MHz, CDCl3): d = 56.39, 110.63, 125.85,
125.89, 127.19, 141.15, 161.85; ATR-IR (cmꢀ1): 3129w, 2921w,
2847s, 1896s, 1611s, 1580w, 1510s, 1470m, 1453w, 1422w,
1335s, 1259s, 1182s, 1146, 1112w, 1097w, 1034s, 1013s, 900s,
863s, 823s, 786s, 747m, 713s; MS (EI): m/z (rel. int.) 305 (21),
304 (100), 245 (14), 228 (16), 73 (13), 44 (46), 32 (72).
Me
Rf = 0.13 (hexane); 1H NMR (300.1 MHz, CDCl3): d = 2.30 (s, 6H),
3.40 (s, 6H), 7.25 (dd, J = 2.4, 0.6 Hz, 2H), 7.32 (dd, J = 2.6, 0.7 Hz,
2H); 13C NMR (75.5 MHz, CDCl3): d = 16.19, 60.34, 116.00, 131.31,
132.75, 133.55, 133.69, 155.32; MS (EI): m/z (rel. int.) 402 (50),
401 (17), 400 (100), 398 (52), 306 (35), 304 (35), 291 (20), 290
(11), 289 (24), 225 (12), 210 (14), 181 (11), 165 (11), 153 (11),
152 (14).
2.2.14. 3,30-Dicarbomethoxy-4,40-dimethoxybiphenyl
[major isomer] (26)
2.2.11. 3,30-Diiodo-4,40-dimethoxybiphenyl [major isomer] (22)
[43,48]
OMe
O
I
MeO
OMe
O
MeO
OMe
I
MeO
Rf = 0.20 (ethyl acetate:hexane = 1:19); white solid; m.p. = 150–
152 °C; 1H NMR (300.1 MHz, CDCl3): d = 3.92 (s, 6H), 6.87 (d,
J = 8.6 Hz, 2H), 7.46 (d, J = 8.6, 2.3 Hz, 2H), 7.98 (d, J = 2.3 Hz, 2H);
13C NMR (75.5 MHz, CDCl3): d = 55.47, 87.41, 110.96, 127.73,
133.90, 137.57, 157.45; ATR-IR (cmꢀ1): 2963s, 2933m, 2833m,
1594s, 1565s, 1549s, 1474w, 1434m, 1404s, 1375w, 1269w,
Rf = 0.19 (hexane:ethyl acetate = 7:3); white solid; m.p. = 115–
117 °C (hexane); 1H NMR (300.1 MHz, CDCl3): d = 3.93 (s, 6H),
3.95 (s, 6H), 7.05 (d, J = 8.8 Hz, 2H), 7.66 (dd, J = 8.8, 2.4 Hz, 2H),
8.00 (d, J = 2.4 Hz, 2H); 13C NMR (75.5 MHz, CDCl3): d = 52.13,
56.17, 112.49, 120.29, 129.79, 131.48, 131.86, 158.37, 166.60;
ATR-IR (cmꢀ1): 3033s, 2925w, 2840s, 1704s, 1611s, 1567s, 1489s,

A. Kar et al. / Journal of Organometallic Chemistry 694 (2009) 524–537
535
1433m, 1380s, 1313s, 1258s, 1236w, 1181s, 1154s, 1094s, 1059s,
1013s, 960s, 900s, 841s, 801s, 778s, 705s, 678s; MS (EI): m/z (rel.
int.) 331 (20), 330 (100), 315 (12) 300 (7), 299 (36), 297 (15),
285 (10), 139 (9); HRMS calcd. for C18H18O6 m/z 330.1098, found
m/z 330.1103.
2972w, 2914m, 2850m, 2736s, 1717s, 1570s, 1531s, 1450w,
1381m, 1202s, 1155m, 1051s, 1036w, 871s, 858s, 778w, 737s,
667s; MS (EI): m/z (rel. int.) 195 (18), 194 (100), 193 (73), 179
(10), 161 (33), 96 (8), 32 (30); HRMS calcd. for C10H10S2 m/z
194.0218, found m/z 194.0222.
2.2.18. 2,20,4,40-Tetrachlorobiphenyl (33) [52]
2.2.15. 3,30-Dicarbomethoxy-2,40-dimethoxybiphenyl [minor isomer]
Cl
OMe
O
OMe
Cl
Cl
OMe
O
Cl
Rf = 0.67 (hexane); colorless liquid; 1H NMR (300.1 MHz,
CDCl3): d = 7.19 (d, J = 8.2 Hz, 2H), 7.32 (dd, J = 8.2, 2.0 Hz, 2H),
7.52 (d, J = 2.0 Hz, 2H); 13C NMR (75.5 MHz, CDCl3): d = 127.03,
129.47, 131.93, 134.33, 134.83, 135.75; MS (EI): m/z (rel. int.)
294 (48), 293 (13), 292 (100), 291 (11), 290 (81), 257 (11), 255
(11), 222 (39), 220 (61), 184 (10), 150 (17), 111 (11), 110 (16),
92 (9); HRMS calcd. for C12H6Cl4 m/z 289.9218, found m/z
289.9217.
MeO
Rf = 0.27 (hexane:ethyl acetate = 7:3); colorless oil; 1H NMR
(300.1 MHz, CDCl3): d = 3.50 (s, 3H), 3.91 (s, 3H), 3.95 (s, 3H),
3.98 (s, 3H), 7.05 (d, J = 8.7 Hz, 1H), 7.22 (t, J = 7.1 Hz, 1H), 7.50
(dd, J = 5.7, 2.0 Hz, 1H), 7.71-7.78 (m, 2H), 8.01 (d, J = 2.0 Hz, 1H);
13C NMR (75.5 MHz, CDCl3): d = 52.08, 52.31, 56.11, 61.54,
111.92, 119.92, 124.04, 125.71, 129.43, 130.38, 132.27, 134.24,
134.60, 135.07, 157.14, 158.59, 166.45, 166.81; MS (EI): m/z (rel.
int.) 331 (22), 330 (100), 299 (42), 297 (22), 256 (12), 239 (19),
238 (13), 209 (10), 139 (13), 126 (129, 44 (11), 32 (11).
2.3. General procedure for HAuCl4 catalyzed hetero-coupling of arenes
with benzene
To a 10 mL vial arene (5–15 mmol), benzene (1–10 mmol),
PhI(OAc)2 (1 mmol), HAuCl4 (0.02 mmol)andaceticacid(1 mL)were
added. The mixture was stirred for 17 h at 95 °C and then quenched
with water (10 mL). The reaction mixture was extracted with EtOAc
(3 ꢂ 10 mL) and the combined organic layer was washed with satu-
rated NaHCO3 (2 ꢂ 20 mL), brine (10 ml), dried over Na2SO4, filtered
and concentrated. Theresidue was purified by column chromatogra-
phy to afford the desired product. Analytically pure sample was ob-
tained by thin layer chromatography of the purified product.
2.2.16. 5,50-Dicarbomethoxy-2,20-dimethylbiphenyl (28) [50]
OMe
O
Me
2.3.1. 5-Chloro-2-methoxybiphenyl (40) [53]
Me
O
OMe
MeO
Rf = 0.36 (hexane:ethyl acetate = 9:1); white solid; m.p. = 134–
136 °C (hexane); 1H NMR (300.1 MHz, CDCl3): d = 2.11 (s, 6H),
3.90 (s, 6H), 7.36 (d, J = 8.0 Hz, 2H), 7.79 (d, J = 1.8 Hz, 2H),
7.96 (dd, J = 8.0, 1.8 Hz, 2H); 13C NMR (75.5 MHz, CDCl3):
d = 20.04, 52.01, 127.84, 128.78, 130.14, 130.42, 140.65, 141.41,
167.02; ATR-IR (cmꢀ1): 3429s, 3024s, 2954w, 1721s, 1606s,
1574s, 1433s, 1295m, 1254w, 1231w, 1189m, 1110w, 1045s,
997m, 966m, 912s, 853s, 834s, 790w, 761w; MS (EI): m/z
(rel. int.) 299 (18), 298 (92), 283 (11), 268 (17), 267 (100), 239
(13), 180 (31), 179 (25), 178 (209, 165 (40), 118 (26), 103 (13), 89
(13); HRMS calcd. for C18H18O4 m/z 298.1200, found m/z 298.1197.
Cl
Rf = 0.18 (hexane); colorless liquid; 1H NMR (300.1 MHz,
CDCl3): d = 3.81 (s, 3H), 6.92 (d, J = 8.7 Hz, 1H), 7.27–7.47 (m,
5H), 7.50–7.55 (m, 2H); 13C NMR (75.5 MHz, CDCl3): d = 55.86,
112.45, 125.67, 127.41, 128.05, 128.08, 129.37, 130.54, 132.24,
137.21, 155.11; MS (EI): m/z (rel. int.) 220 (29), 219 (14), 218
(87), 205 (6), 202 (20), 169 (13), 168 (100), 167 (7), 140 (8), 139
(35).
2.3.2. 5-Bromo-2-methoxybiphenyl (41) [54]
2.2.17. 5,50-Dimethyl-2,20-bithiophenyl (31) [6e,51]
OMe
S
S
Me
Me
Br
Rf = 0.63 (hexane); white solid; m.p. = 62–65 °C; 1H NMR
(300.1 MHz, CDCl3): d = 2.48 (d, J = 1.1 Hz, 6H), 6.65 (qd, J = 3.8,
1.1 Hz, 2H), 6.89 (d, J = 3.8 Hz, 2H); 13C NMR (75.5 MHz, CDCl3):
d = 15.30, 122.84, 125.72, 135.49, 138.45; ATR-IR (cmꢀ1): 3066s,
Rf = 0.17 (hexane); colorless liquid; 1H NMR (300.1 MHz,
CDCl3): d = 3.81 (s, 3H), 6.88 (d, J = 8.6 Hz, 1H), 7.33–7.53 (m,
5H), 7.49–7.54 (m, 2H); 13C NMR (75.5 MHz, CDCl3): d = 55.79,

536
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137.10, 155.61; MS (EI): m/z (rel. int.) 265 (7), 264 (50), 263 (9),
262 (52), 168 (100), 169 (13), 152 (5), 140 (8), 139 (32).
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OMe
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I
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7.60–7.65 (m, 2H); 13C NMR (75.5 MHz, CDCl3): d = 55.66, 83.02,
113.50, 127.40, 128.06, 129.35, 133.20, 136.96, 137.15, 139.17,
156.41; MS (EI): m/z (rel. int.) 311 (14), 310 (100), 169 (9), 168
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Rf = 0.32 (hexane:ethyl acetate = 8:2); white solid; m.p. =
104 °C; 1H NMR (300.1 MHz, CDCl3): d = 1.25 (d, J = 6.2 Hz, 6H),
1.30 (d, J = 6.2 Hz, 6H), 2.26 (s, 3H), 2.32 (s, 3H), 4.96–5.06 (m,
2H), 6.78 (s, 1H), 7.00–7.04 (m, 1H), 7.09 (d, J = 7.8 Hz, 1H), 7.26
(bs, 1H); 13C NMR (75.5 MHz, CDCl3): d = 17.25, 20.71, 21.95,
21.99, 69.98, 70.55, 128.33, 128.83, 130.43, 132.27, 136.29,
140.50, 155.99; ATR-IR (cmꢀ1): 3429s, 3018w, 2980s, 2937w,
1747s, 1690s, 1617s, 1521s, 1506s, 1466s, 1449s, 1396s, 1381w,
1337s, 1322s, 1309s, 1239s, 1173s, 1108s, 1050s, 1028s, 942w,
895s, 856m, 815s, 768m, 729s, 677m; MS (EI): m/z (rel. int.) 308
(6), 223 (6), 222 (40), 207 (14), 181 (10), 180 (100), 164 (6), 147
(5), 146 (7), 136 (7), 135 (49), 133 (15), 121 (8), 120 (23), 119
(21), 118 (14), 108 (26), 106 (5), 105 (15), 93 (10), 91 (16), 79
(6), 77 (11), 43 (71), 41 (17), 27 (6); HRMS calcd. for C16H24O4N2
m/z 308.1736, found m/z 308.1738.
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