Pd-catalyzed oxidative cross-coupling between two electron rich heteroarenes

Article abstract of DOI:10.1039/c3sc51278a

The transition-metal-catalyzed oxidative cross-coupling between two coupling partners with similar structure and electronic characteristics remains a challenge owing to difficulty in suppressing undesired homo-couplings. We herein report a Pd-catalyzed oxidative cross-coupling between two thiophenes under mild reaction conditions. This approach can also be extended to furans. Some notable advantages of this reaction lie in its synthetic simplicity with the omission of the toxic stannanes coupling partner and excellent functional-group compatibility. The features of this protocol make it an ideal strategy for the construction of a 2,2′-thiophene-thiophene linkage of interest in electronic and optoelectronic materials.

Full text of DOI:10.1039/c3sc51278a

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Pd-catalyzed oxidative cross-coupling between two
electron rich heteroarenes†
Cite this: DOI: 10.1039/c3sc51278a
b
Chun-Yang He,a Zhen Wang,b Cai-Zhi Wu,a Feng-Ling Qingab and Xingang Zhang
*
The transition-metal-catalyzed oxidative cross-coupling between two coupling partners with similar
structure and electronic characteristics remains a challenge owing to difficulty in suppressing undesired
homo-couplings. We herein report a Pd-catalyzed oxidative cross-coupling between two thiophenes
under mild reaction conditions. This approach can also be extended to furans. Some notable
advantages of this reaction lie in its synthetic simplicity with the omission of the toxic stannanes
coupling partner and excellent functional-group compatibility. The features of this protocol make it an
ideal strategy for the construction of a 2,20-thiophene–thiophene linkage of interest in electronic and
optoelectronic materials.
Received 8th May 2013
Accepted 17th June 2013
DOI: 10.1039/c3sc51278a
www.rsc.org/chemicalscience
Because bithiophenes can alternate p-conjugated oligomers or susceptible to homocoupling in the existing catalytic systems.8
polymers with unique electrical and optical properties, such an Furthermore, although important progress has been made in
important structural motif is a popular choice for the prepara- the transition-metal-catalyzed oxidative cross coupling between
tion of advanced materials in various electronic and optoelec- two (hetero)arenes during the past few years,9,10 realizing such a
tronic devices, such as organic light-emitting diodes (OLEDs),1 strategy between two coupling partners with similar structure
organic eld-effect transistors (OFETs),2 organic electrochromic and electronic characteristics remains a hindrance owing to the
devices (ECDs),3 and organic solar cells (OSCs).4 A common difficulty in suppressing undesired homo-couplings.11 Hence, it
synthetic method toward bithiophenes is palladium-catalyzed is highly desirable to develop a new catalytic system to overcome
cross-coupling of stannyl thiophenes with thienyl halides (Stille these limitations for widespread applications. Herein, we report
cross-coupling).5 Despite its great reliability and versatility, this a Pd-catalyzed oxidative cross-coupling between two thiophenes
method involves drawbacks such as the use of toxic stannanes (p-electron rich vs. p-electron rich). The reaction proceeds
that are difficult to handle or require extra steps to prepare, and smoothly under mild reaction conditions. The high reaction
oen generate stoichiometric amount of toxic and environ- efficiency as well as the excellent functional group compatibility
mentally risky by-products. Moreover, the important functional of this approach represent an ideal strategy for the construction
groups such as halides are incompatible in these reactions. of well-dened bithiophenes. Furthermore, this approach can
From the point of view of synthetic simplicity as well as a new also be extended to furans. To demonstrate the synthetic
practical and environmentally benign process, the construction importance of the approach, the application of the reaction in
of a thiophene–thiophene linkage structural motif via a tran- functional materials has also been described in a highly effi-
sition-metal-catalyzed oxidative cross-coupling between two cient manner.
simple thiophenes would be an ideal strategy, since the use of
Considering that 3-hexylthiophene is an important unit in
the C–H bond as the functional group6 avoids the pre- the development of high performance electronic and optoelec-
functionalization steps of both thiophenes. However, the tronic materials,12 and bromide and amide could be further
formation of the bithiophene-structure via this strategy is still a functionalized in the preparation of a thiophene-based struc-
great challenge, and has not been reported to date.7 The reason ture, 2-bromo-3-hexylthiophene 2a and N,N-dimethylthiophene-
is that thiophenes are p-electron rich heteroarenes, and are 2-carboxamide 1a were chosen as model substrates (Table 1).
Initially, no desired product 3a was observed when the reaction
was carried out in DMF at 80 ꢀC by using Pd(OAc)2 (10 mol%) as
aCollege of Chemistry, Chemical Engineering and Biotechnology, Donghua University,
a catalyst and AgOAc (3.0 equiv.) as an oxidant (Table 1, entry 1).
Aer a survey of the reaction parameters, such as solvents,
oxidants, and the additives, carboxylic acids previously
demonstrated to have a benecial effect on the C–H bond
activation of simple arenes13 (for details see ESI†), it turned
out that DMSO,14 Ag2O and benzoic acid are critical to the
reaction efficiency, providing 3a in 67% yield (Table 1, entry 7).
2999 North Renmin Lu, Shanghai 201620, China
bKey Laboratory of Organouorine Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032,
China. E-mail: xgzhang@mail.sioc.ac.cn; Fax: +86-21-6416-6128; Tel: +86-21-5492-
5333
† Electronic supplementary information (ESI) available: Detailed experimental
procedures, and analytical data for all new compounds. For ESI or other
electronic format see DOI: 10.1039/c3sc51278a
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previously reported.13 In addition, no reaction was observed in
the absence of Ag2O or Pd(OAc)2, thus demonstrating that a
palladium redox catalytic cycle is involved in the reaction
(Table 1, entries 18–19).
Table 1 Representative results for optimization of Pd-catalyzed oxidative cross-
coupling of N,N-dimethylthiophene-2-carboxamide 1a with 2-bromo-3-hexylth-
iophene 2aa
Under the optimum reaction conditions (Table 1, entry 14), a
wide range of 2,20-bithiophenes were generated in moderate to
good yields (Table 2).16 Thiophenes bearing important func-
tional groups, such as methyl ketone, ester, aldehyde, and
nitrile, underwent the cross-coupling smoothly with 2-bromo-3-
hexylthiophene 2a (3a–f), thus providing a good opportunity for
further transformation by using these functional groups.
Importantly, compound 3e, a useful building block in the
development of organic solar cells,17 can be easily prepared
from simple thiophene in good yield (72%) via only one step,
thus featuring the advantages of present strategy. Interestingly,
thiophenes with bromide and chloride at C2-position showed
similar reactivity (3h and 3j), while providing slightly lower
yields than their corresponding 2-halo-3-methylthiophenes (3g
and 3i). However, when 2-methyl-thiophene was investigated,
only a moderate yield (53%) of 3k was afforded. These results
indicated that the efficient cross-coupling of thiophenes
depends on their electronic-proles. Benzothiophene and 2-
phenylthiophene are also suitable substrates with good yields
obtained (3l–n). It is worth noting that an alkyne can also
tolerate the reaction conditions (3o), and as a result some
alkyne containing thiophene-based functional materials can be
efficiently prepared via this strategy18 or an additional thio-
Entry
x
Oxidant (equiv.) Solvent Additive (equiv.) Yield (%)b
1c
2c
3c
4c
5c
6c
7
10
10
10
10
10
10
10
5
AgOAc (3)
AgOAc (3)
AgOAc (3)
AgOAc (3)
Ag2CO3 (3)
Ag2O (1.5)
Ag2O (3)
DMF
Dioxane
DCE
—
—
—
—
—
—
NR
NR
NR
28
24
29
67
72
65
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
PhCO2H (3)
PhCO2H (3)
PhCO2H (3)
oMe-PhCO2H (3) 70
pMe-PhCO2H (3) 64
oNO2-PhCO2H (3) 52
oPh-PhCO2H (3)
oPh-PhCO2H (2)
HOAc (2)
CF3CO2H (2)
—
8
9
Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
2.5 Ag2O (3)
10
11
12
13
14
15
16
17
18
19
71
71d
61
26
28
NR
NR
2.5
—
Ag2O (3)
oPh-PhCO2H (2)
oPh-PhCO2H (2)
—
a
Reaction conditions (unless otherwise specied): 1a (0.9 mmol), 2a
(0.3 mmol), solvent (2 mL). Isolated yield. c 1a/2a ¼ 1 : 1.5, 0.3 mmol phene ring can be introduced from the alkyne.19
b
scale. d 25% homocoupling of 2a was isolated.
Table 2 Pd-catalyzed oxidative cross-coupling between two thiophenesa
Decreasing the loading amount of Pd(OAc)2 from 10 mol% to
5 mol% further improved the yield to 72% (Table 1, entry 8).
However, when 2.5 mol% of Pd(OAc)2 was used, a lower yield
(65%) was observed (Table 1, entry 9). Considering that the
steric and electronic effect of benzoic acid could be tuned by the
substituents, which may inuence the activity of the carboxylic
acid and benet formation of cross-coupling product 3a,
different substituted benzoic acids were then investigated to
further optimize the catalytic system (Table 1, entries 10–13).
Finally, the desired cross-coupling product 3a was improved to
71% yield albeit with the formation of homocoupling by-prod-
ucts (25% yield of homocoupling of 2a was obtained15) when
2.0 equiv. of ortho-phenyl benzoic acid (oPh-PhCO2H) and 2.5
mol% of Pd(OAc)2 were used (Table 1, entry 14). It is worth
noting that benzoic acid with a bulky substituent at its ortho
position benets the reaction efficiency, while an electron-
decient substituent diminishes the yield. A control experiment
using AcOH was also performed under the optimized reaction
conditions (Table 1, entry 14), providing a slightly lower yield
than oPh-PhCO2H (Table 1, entry 15), while a dramatically
decreased yield was observed when more acidic TFA or no acid
was used (Table 1, entries 16–17). Thus, these ndings
demonstrate that the nature of carboxylic acids is critical for the
reaction efficiency. We supposed that the oPh-PhCO2 gener-
ated by the reaction of oPh-PhCO2H with Ag2O may serve as a
suitable base to assist the C–H cleavage for thiophenes as
a
ꢁ
Reaction conditions (unless otherwise specied): 1 (3 equiv.), 2
(0.3 mmol), DMSO (2 mL). All reported yields are isolated yields. The
number in parentheses is the homocoupling yield of compound 2.
b
5 mol% of Pd(OAc)2 was used. c No homocoupling of 2 was observed.
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The construction of 2,20-bithiophenes via the present products (3x). It should be mentioned that an important
strategy is not limited to the cross-coupling of two thiophenes monomer 3y used for organic solar cell and other useful elec-
bearing substituents with different electronic characteristics. tronic devices21 was easily prepared in only one step without the
Thiophenes with similar electron-decient groups, such as ester prerequirement of the preparation of thienyl bromides or
and amide, also furnished the corresponding bithiophene 3p in organotin reagents.
high efficiency (Table 3, 3p). Importantly, the introduction of a
The importance of the protocol can also be featured by the
highly electron-decient pentauorophenyl group at C2 posi- rapid access of p-conjugated oligomer 7 for dye-sensitized solar
tion of thiophene did not affect the cross-coupling with 1a, thus cell in only three steps17a (Scheme 1). Application of the present
providing a new strategy for the preparation of a polyuoroaryl- method, the key intermediate oligothiophene 5 was obtained in
thiophene based structural motif of interest in functional an efficient way, followed by the direct introduction of another
materials20 (3q). Furthermore, thiophenes bearing electron- thiophene ring with the use of the Pd(OAc)2/PPh3 catalytic
donating groups are also suitable substrates, providing 3r, 3t, system,22 providing compound
6 in good yield. Finally,
and 3u in moderate to good yields. A reasonable yield of 3s was condensation of 6 with 2-cyanoacetic acid afforded 7 in 98%
obtained due to signicant formation of homocoupling by- yield. Thus, compared with the traditional method,17a the
products. Extension to furans could also afford synthetically present method features the following advantages: (1) high
useful yields by using Pd(TFA)2, AgOAc, and 1,10-phen catalytic efficiency and synthetic simplicity without extra prefunctional-
systems (3v and 3w). However, the cross-coupling between ization steps, such as the preparation of stannyl thiophene and
furans led to a low yield due to formation of some uncertain by- bromination of thiophene (3 steps vs. 6 steps); (2) environ-
mental friendliness without the generation of toxic and envi-
ronmentally risky by-products (H vs. Sn). To further
demonstrate the usefulness of this protocol, bithiophene 9, a
Table
3
Pd-catalyzed oxidative cross-coupling between two electron-rich
key intermediate in the preparation of the in vivo optical
imaging agent 11 for diagnosing Alzheimer's disease,23 was also
synthesized in high efficiency. Deprotection of a methyl group
on compound 9 with BBr3followed by condensation with
malononitrile afforded 11 with even higher overall yield than
the traditional method did using an organotin intermediate
(45% overall yield, 3 steps vs. 37% overall yield, 5 steps).23
To gain some mechanistic insight into the present reaction,
kinetic isotope effect (KIE) experiments for both coupling part-
ners were conducted (Scheme 2). Initial rate measurements
revealed KIEs of 2.6 and 4.1 for 1e and 2h, respectively (for details
see ESI†). These ndings imply that (1) the turnover-limiting
heteroarenesa
a
Reaction conditions (unless otherwise specied): 1/2 (3 equiv.), 2/1
(0.3 mmol), DMSO (2 mL). All reported yields are isolated yields. The
number in parentheses is the homocoupling yield of compound 2/1.
b
Pd(TFA)2 (10 mol%), AgOAc (3.0 equiv.), 1,10-phen (0.2 equiv.),
c
DMSO/DMA (3 : 1, 2 mL) at 100 ꢀC. No homocoupling of 2 was
observed. 0.1 mmol scale, Pd(OAc)2 (5% mmol), 2a (6 equiv.), Ag2O
(6 equiv.), DMSO (3 mL), 14 h. The homocoupling of 2/1 was not
d
e
Scheme 1 Synthesis of functional materials p-conjugated oligomer 7 and
optical imaging agent 11.
determined.
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showed that a concerted metalation-deprotonation (CMD)25
pathway could be involved for a Pd(II)–acetate complex catalyzed
C–H bond cleavage for thiophenes.26 Since the typical SEAr
pathway was ruled out, on the basis of previous studies as well
as the fact that the C–H bond cleavage of present reaction
depends on the C–H bond acidity and the nature of carboxylate,
we proposed that the present reaction may proceed via a CMD
pathway. However, the detailed mechanism remains a point of
discussion.
Scheme 2 Kinetic isotope effect studies.
In conclusion, a Pd-catalyzed oxidative cross-coupling of
thiophenes has been developed. The solvent effect and additive
benzoic acid play critical roles in the reaction efficiency. Thio-
phenes bearing electron-withdrawing or electron-donating
groups all furnished the cross-coupling products efficiently.
Application of the method led to important and useful oligo-
thiophene building blocks, which can be further applied in
photovoltaics. Because of the high reaction efficiency under
mild reaction conditions, operational simplicity with the
omission of organotin reagents and prefunctionalization
process, as well as excellent functional group compatibility, this
protocol provides a straightforward and efficient access to 2,20-
bithiophenes. Furthermore, this approach can also be extended
to furans. We believe that this protocol should be useful for the
atom/step-economical synthesis of new thiophene-based elec-
tronic and optoelectronic materials. Mechanistic studies
revealed that the cleavage of C–H bonds for both thiophenes
depends on their electronic-proles. Further studies to uncover
the detailed mechanism and expand the substrate scope and
their applications are now in progress.
step24 of the catalytic cycle is the C–H cleavage of relatively elec-
tron-rich thiophene, and (2) the cleavage of the C–H bonds in
both thiophenes depends on their electronic-proles, and the
C–H bond cleavage for thiophenes bearing electron-decient
substituents is relatively easier than that of electron-rich ones.
Thus, the possibility of C–H bond cleavage for thiophenes under
present reaction conditions via a typical electrophilic aromatic
substitution (SEAr) pathway can be ruled out, as the observed
reactivity of substituted thiophenes 1e and 2h is not in agree-
ment with SEAr reactivity.
Additionally, when the reaction of d-1e with 2h was con-
ducted within 10 min, no homocoupling of 1e was formed
(Scheme 3a). A similar result was also observed in the treatment
of 1e with d-2h, in which the homocoupling of 2h was not
detected until the reaction lasted 20 min (Scheme 3b). However,
both of these reactions provided the cross-coupling product 3n
and homocoupling by-products of non-deuterated coupling
partners. Thus, these results implied that the present reaction
could be initiated from both thiophenes.
On the basis of above results, we proposed that the present
reaction could be initiated from both thiophenes to give a pal-
ladated thienyl complex, which then reacts with the other
thiophene to form a dithienyl palladium complex. Finally,
reductive elimination provides the nal product, and the
released Pd(0) species is reoxidized by silver salt to regenerate
Pd(II). Among these two pathways, the reaction begins with
relatively electron-decient thiophene might be the major
pathway. However, the formation of a dithienyl palladium
complex through metal-exchange between two palladated
thienyl complexes could not be ruled out. Previous studies
Acknowledgements
This work was nancially supported by the National Basic
Research Program of China (973 Program) (no. 2012CB821600),
the NSFC (nos 21172242), and SIOC.
Notes and references
1 (a) J. Roncali, Macromol. Rapid Commun., 2007, 28, 1761; (b)
S. Gunes, H. Neugebauer and N. S. Saricici, Chem. Rev.,
2007, 107, 1324; (c) A. C. Grimsdale, K. L. Chan,
R. E. Martin, P. G. Jokisz and A. B. Holmes, Chem. Rev.,
2009, 109, 897; (d) P.-L. T. Boudreault, A. Najari and
M. Leclerc, Chem. Mater., 2011, 23, 456.
2 (a) V. Coropceanu, J. Cornil, D. A. da Silva Filho, Y. Olivier,
R. Silbey and J.-L. Bredas, Chem. Rev., 2007, 107, 926; (b)
M. Mas-Torrent and C. Rovira, Chem. Soc. Rev., 2008, 37,
827; (c) S. Allard, M. Forster, B. Souharce, H. Thiem and
U. Scherf, Angew. Chem., Int. Ed., 2008, 47, 4070; (d)
W. Wu, Y. Liu and D. Zhu, Chem. Soc. Rev., 2010, 39, 1489.
3 (a) A. A. Argun, P. H. Aubert, B. C. Thompson,
I. Schwendeman, C. L. Gaupp, J. Hwang, N. J. Pinto,
D. B. Tanner, A. G. MacDiarmid and J. R. Reynolds, Chem.
Mater., 2004, 16, 4401; (b) P. M. Beaujuge and
J. R. Reynolds, Chem. Rev., 2010, 110, 268.
4 (a) B. C. Thompson and J. M. J. Frechet, Angew. Chem., Int.
Ed., 2008, 47, 58; (b) Z. Ning and H. Tian, Chem. Commun.,
Scheme 3 Pd-catalyzed oxidative cross-coupling between H/d-1e and H/d-2h.
Chem. Sci.
This journal is ª The Royal Society of Chemistry 2013

View Article Online
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2009, 5483; (c) Y.-J. Cheng, S.-H. Yang and C.-S. Hsu, Chem.
Rev., 2009, 109, 5868.
Angew. Chem., Int. Ed., 2011, 50, 5365; (o) D. Mandal,
A. D. Yamaguchi, J. Yamaguchi and K. Itami, J. Am. Chem.
Soc., 2011, 133, 19660; (p) A. D. Yamaguchi, D. Mandal,
J. Yamaguchi and K. Itami, Chem. Lett., 2011, 40, 555; (q)
J. Wencel-Delord, C. Nimphius, F. W. Patureau and
F. Glorius, Angew. Chem., Int. Ed., 2012, 51, 2247; (r)
L. Zhou and W. Lu, Organometallics, 2012, 31, 2124; (s)
C.-Y. He, Q.-Q. Min and X. Zhang, Organometallics, 2012,
31, 1335; (t) J. Dong, Z. Long, F. Song, N. Wu, Q. Guo,
J. Lan and J. You, Angew. Chem., Int. Ed., 2013, 52, 580.
5 (a) A. de Meijere and F. Diederich, Metal-Catalyzed Cross-
Coupling Reactions, Wiley-VCH, Weinheim, 2nd edn, 2004;
(b) Y.-J. Cheng, S.-H. Yan and C.-S. Hsu, Chem. Rev., 2009,
109, 5868; (c) B. Carsten, F. He, H.-J. Son, T. Xu and L. Yu,
Chem. Rev., 2011, 111, 1493.
6 For selected recent reviews related to C–H bonds activation,
see: (a) L.-C. Campeau and K. Fagnou, Chem. Commun., 2006,
1253; (b) O. Daugulis, V. G. Zaitzev, D. Shabashov,
Q.-N. Pham and A. Lazareva, Synlett, 2006, 3382; (c) 11 For transition-metal-catalyzed oxidative cross-coupling
D. Alberico, M. E. Scott and M. Lautens, Chem. Rev., 2007,
107, 174; (d) R. Giri, B. F. Shi, K. M. Engle, N. Maugel and
J.-Q. Yu, Chem. Soc. Rev., 2009, 38, 3242; (e) L. Ackermann,
R. Vicente and A. R. Kapdi, Angew. Chem., Int. Ed., 2009,
48, 9792; (f) D. A. Colby, R. G. Bergman and J. A. Ellman,
Chem. Rev., 2010, 110, 624; (g) T. W. Lyons and
M. S. Sanford, Chem. Rev., 2010, 110, 1147; (h) C.-L. Sun,
B.-J. Li and Z.-J. Shi, Chem. Commun., 2010, 46, 677.
between two similar structures, see: (a) W. Han, P. Mayer
and A. R. Oal, Angew. Chem., Int. Ed., 2011, 50, 2178; (b)
J. Dong, Y. Huang, X. Qin, Y. Cheng, J. Hao, D. Wan,
W. Li, X. Liu and J. You, Chem.–Eur. J., 2012, 18, 6158; (c)
N. Kuhl, M. N. Hopkinson and F. Glorius, Angew. Chem.,
Int. Ed., 2012, 51, 8230; (d) X. Qin, B. Feng, J. Dong, X. Li,
Y. Xue, J. Lan and J. You, J. Org. Chem., 2012, 77, 7677; (e)
Z. Mao, Z. Wang, Z. Xu, F. Huang, Z. Yu and R. Wang, Org.
Lett., 2012, 14, 3854; (f) S. Fan, Z. Chen and X. Zhang, Org.
Lett., 2012, 14, 4950.
7 Metal-free arylation of thiophenes, see: (a) Y. Kita,
K. Morimoto, M. Ito, C. Ogawa, A. Goto and T. Dohi, J. Am.
Chem. Soc., 2009, 131, 1668, For copper-catalyzed 12 For review, see: (a) H. Klauk, Chem. Soc. Rev., 2010, 39, 2643.
iodination/arylation sequence, see: (b) H.-Q. Do and
O. Daugulis, J. Am. Chem. Soc., 2011, 133, 13577.
8 (a) K. Masui, H. Ikegami and A. Mori, J. Am. Chem. Soc., 2004,
126, 5074; (b) M. Takahashi, K. Masui, H. Sekiguchi,
N. Kobayashi, A. Mori, M. Funahashi and N. Tamaok,
J. Am. Chem. Soc., 2006, 128, 10930.
9 For selected recent reviews related to transition-metal
catalyzed oxidative cross-coupling, see: (a) C. S. Yeung and
V. M. Dong, Chem. Rev., 2011, 111, 1215; (b) J. L. Bras and
J. Muzart, Chem. Rev., 2011, 111, 1170; (c) C. Liu, H. Zhang,
W. Shi and A. Lei, Chem. Rev., 2011, 111, 1780; (d) W. Han
and A. R. Oal, Synlett, 2011, 1951; (e) S. H. Cho, J. Y. Kim,
For selected examples, see: (b) M. Sevignon, J. Papillon,
E. Schulz and M. Lemaire, Tetrahedron Lett., 1999, 40, 5873;
(c) Q. Wang, R. Takita, Y. Kikuzaki and F. Ozawa, J. Am.
Chem. Soc., 2010, 132, 11420; (d) S. Tamba, K. Shono,
A. Sugie and A. Mori, J. Am. Chem. Soc., 2011, 133, 9700.
13 (a) D. L. Davies, S. M. A. Donald and S. A. Macgregor, J. Am.
Chem. Soc., 2005, 127, 13754; (b) D. Garcia-Cuadrado, P. de
Mendoza, A. A. C. Braga, F. Maseras and A. M. Echavarren,
J. Am. Chem. Soc., 2007, 129, 6880; (c) M. Lafrance,
S. I. Gorelsky and K. Fagnou, J. Am. Chem. Soc., 2007, 129,
14570; (d) S. I. Gorelsky, D. Lapointe and K. Fagnou, J. Am.
Chem. Soc., 2008, 130, 10848.
J. Kwak and S. Chang, Chem. Soc. Rev., 2011, 40, 5068; (f) 14 DMSO benets the palladium catalytic cycle, see:
X. Bugaut and F. Glorius, Angew. Chem., Int. Ed., 2011, 50,
7479.
B. A. Steinhoff and S. S. Stahl, J. Am. Chem. Soc., 2006, 128,
4348 and ref. 10i.
10 For selected examples related to transition-metal catalyzed 15 29% yield (based on 1a) of homocoupling of 1a was also
oxidative di(hetero)arylation cross-coupling, see: (a) R. Li, observed, because 3.0 equiv. of 1a was used.
L. Jiang and W. Lu, Organometallics, 2006, 25, 5973; (b) 16 Both of homocoupling by products of 1 and 2 were observed.
D. R. Stuart and K. Fagnou, Science, 2007, 316, 1172; (c)
T. A. Dwight, N. R. Rue, D. Charyk, R. Josselyn and
B. DeBoef, Org. Lett., 2007, 9, 3137; (d) D. R. Stuart,
E. Villemure and K. Fagnou, J. Am. Chem. Soc., 2007, 129,
Since excessive amounts of compound 1 were used, the
yields of homocoupling byproducts of were not
determined. For the homocoupling byproducts of 2, see
1
the numbers in parentheses in Tables 2 and 3.
12072; (e) K. L. Hull and M. S. Sanford, J. Am. Chem. Soc., 17 For selected examples, see: (a) E. Kozma, I. Concina,
2007, 129, 11904; (f) B.-J. Li, S.-L. Tian, Z. Fang and
Z.-J. Shi, Angew. Chem., Int. Ed., 2008, 47, 1115; (g)
G. Brasche, J. Garcia-Fortanet and S. L. Buchwald, Org.
Lett., 2008, 10, 2207; (h) K. L. Hull and M. S. Sanford,
J. Am. Chem. Soc., 2009, 131, 9651; (i) C.-Y. He, S. Fan and
X. Zhang, J. Am. Chem. Soc., 2010, 132, 12850; (j) P. Xi,
F. Yang, S. Qin, D. Zhao, J. Lan, G. Gao, C. Hu and J. You,
A. Braga, L. Borgese, L. E. Depero, A. Vomiero,
G. Sberveglieri and M. Catellani, J. Mater. Chem., 2011, 21,
13785; (b) H.-C. Chu, D. Sahu, Y.-C. Hsu, H. Padhy,
D. Patra, J.-T. Lin, D. Bhattacharya, K.-L. Lu, K.-H. Wei and
H.-C. Lin, Dyes Pigm., 2012, 93, 1488; (c) F. Fages,
E. Shilova, C. Martini and J. Ackermann, WO 2012049167,
2012.
J. Am. Chem. Soc., 2010, 132, 1822; (k) Y. Wei and W. Su, 18 (a) C. Wang, H. Dong, W. Hu, Y. Liu and D. Zhu, Chem. Rev.,
J. Am. Chem. Soc., 2010, 132, 16377; (l) H. Li, J. Liu,
C.-L. Sun, B.-J. Li and Z.-J. Shi, Org. Lett., 2011, 13, 276; (m)
2012, 112, 2208; (b) S. C. Rasmussen, R. L. Schwiderski and
M. E. Mulholland, Chem. Commun., 2011, 47, 11394.
X. Wang, D. Leow and J.-Q. Yu, J. Am. Chem. Soc., 2011, 19 K. T. Potta, S. A. Nye and K. A. Smith, J. Org. Chem., 1992, 57,
133, 13864; (n) Z. Wang, K. Li, D. Zhao, J. Lan and J. You,
3895.
This journal is ª The Royal Society of Chemistry 2013
Chem. Sci.

View Article Online
Chemical Science
Edge Article
20 For a review, see: (a) F. Babudri, G. M. Farinola, F. Naso and 22 S. Fan, C.-Y. He and X. Zhang, Chem. Commun., 2010, 46,
R. Ragni, Chem. Commun., 2007, 1003. For selected recent 4926.
papers, see: (b) M. L. Tang, A. D. Reichardt, N. Miyaki, 23 (a) E. E. Nesterov, J. Skoch, B. T. Hyman, W. E. Klunk,
R. M. Stoltenberg and Z. Bao, J. Am. Chem. Soc., 2008, 130,
6064; (c) Y. Wang, S. R. Parkin and M. D. Watson, Org.
Lett., 2008, 10, 4421; (d) Y. Wang and M. D. Watson, J. Am.
Chem. Soc., 2006, 128, 2536; (e) M.-H. Yoon, A. Facchetti,
C. E. Stern and T. J. Marks, J. Am. Chem. Soc., 2006, 128,
B. J. Backai and T. M. Swager, Angew. Chem., Int. Ed., 2005,
44, 5452; (b) compound 9 can also be used for preparation
of non-linear optical materials, see: C. Herbivo, A. Comel,
G. Kirsch, A. M. C. Fonseca, M. Belsley and
M. M. M. Raposo, Dyes Pigm., 2010, 86, 217.
5792; (f) J. A. Letizia, A. Facchetti, C. L. Stern, M. A. Ratner 24 E. M. Simmons and J. F. Hartwig, Angew. Chem., Int. Ed.,
and T. J. Marks, J. Am. Chem. Soc., 2005, 127, 13476. 2012, 51, 3066.
21 (a) W. Li, W. S. C. Roelofs, M. M. Wienk and R. A. J. Janssen, 25 For a review, see: D. Lapointe and K. Fagnou, Chem. Lett.,
J. Am. Chem. Soc., 2012, 134, 13787; (b) Y. Zou, D. Gendron, 2010, 39, 1118.
R. Neagu-Plesu and M. Leclerc, Macromolecules, 2009, 42, 26 S. I. Gorelsky, D. Lapointe and K. Fagnou, J. Org. Chem.,
6361.
2012, 77, 658.
Chem. Sci.
This journal is ª The Royal Society of Chemistry 2013