Diarylated ethanones from Mo(CO)6-mediated and microwave-assisted palladium-catalysed carbonylative Negishi cross-couplings

Article abstract of DOI:10.1002/ejoc.201300610

Two protocols for palladium-catalysed carbonylative Negishi cross-couplings were developed for aryl iodides and aryl bromides. The two main breakthroughs were that molybdenum hexacarbonyl [Mo(CO)₆] could be used as a solid in situ source of CO, and that controlled microwave irraditaion could be used for heating. Consequently, the reactions were safe (in contrast to when CO gas was used) and fast (in comparison to when conventional heating was used). The carbonylative cross-coupling reactions were carried out using commercially available benzylzinc bromide in closed vials (90-120°C for 0.5-1 h) to give a set of diarylated ethanones, a common pharmacophore found in several pharmaceuticals, in moderate to high isolated yields (47-84 %). The mild three-component carbonylation protocol presented here is operationally simple, safe, and rapid, and the formation of the carbonylative Negishi cross-coupling product is favoured over the product of Negishi cross-coupling. Copyright

Full text of DOI:10.1002/ejoc.201300610

Job/Unit: O30610
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Date: 17-06-13 18:05:53
Pages: 6
SHORT COMMUNICATION
Carbonylative Cross-Coupling
Two palladium-catalysed gas-free carb-
onylative Negishi cross-coupling protocols
using Mo(CO)6 and microwave irradiation
were optimized and used to synthesize a
series of diarylated ethanones.
H. V. Motwani, M. Larhed* ............. 1–6
Diarylated Ethanones from Mo(CO)6-Me-
diated and Microwave-Assisted Palladium-
Catalysed Carbonylative Negishi Cross-
Couplings
Keywords: Carbonylation / Cross-coupling /
Palladium / Homogeneous catalysis / Metal
carbonyls / Microwave chemistry
0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Job/Unit: O30610
/KAP1
Date: 17-06-13 18:05:53
Pages: 6
H. V. Motwani, M. Larhed
SHORT COMMUNICATION
DOI: 10.1002/ejoc.201300610
Diarylated Ethanones from Mo(CO)6-Mediated and Microwave-Assisted
Palladium-Catalysed Carbonylative Negishi Cross-Couplings
Hitesh V. Motwani[a] and Mats Larhed*[a]
Keywords: Carbonylation / Cross-coupling / Palladium / Homogeneous catalysis / Metal carbonyls / Microwave chemistry
Two protocols for palladium-catalysed carbonylative Negishi
cross-couplings were developed for aryl iodides and aryl
commercially available benzylzinc bromide in closed vials
(90–120 °C for 0.5–1 h) to give a set of diarylated ethanones,
bromides. The two main breakthroughs were that molybd- a common pharmacophore found in several pharmaceuticals,
enum hexacarbonyl [Mo(CO)6] could be used as a solid in
situ source of CO, and that controlled microwave irraditaion
could be used for heating. Consequently, the reactions were
safe (in contrast to when CO gas was used) and fast (in com-
parison to when conventional heating was used). The carb-
onylative cross-coupling reactions were carried out using
in moderate to high isolated yields (47–84%). The mild three-
component carbonylation protocol presented here is opera-
tionally simple, safe, and rapid, and the formation of the
carbonylative Negishi cross-coupling product is favoured
over the product of Negishi cross-coupling.
Introduction
In the drug discovery process, it is common practice to
synthesize series of congeners based on pharmacophore
templates to explore structure–activity relationships for the
targets of interest. For this purpose it is important to have
access to rapid, robust, and reliable synthetic methods. The
1,2-diarylated ethanone (deoxybenzoin) structure is a com-
mon pharmacophore that is found in several pharmaceuti-
cals. Examples of drugs that contain a 1,2-diarylated eth-
anone substructure include Bermoprofen (anti-inflamma-
tory), Oxacarbazepine (anti-convulsant) and Narceine (an-
algesics).[1–3] Palladium-catalysed Heck, Stille, and Negishi
reaction protocols have been developed for the synthesis of
various deoxybenzoins, both by our group and others.[4–7]
The carbonylative Negishi cross-coupling (Scheme 1) is a
less explored method for the functionalization of aryl hal-
ides.[8] An important synthetic advantage of the Negishi
carbonylation reaction is that organozinc compounds,
which are widely available with different substituents, are
less toxic than, for example, organostannanes.[5]
Scheme 1. Negishi cross-coupling vs. carbonylative Negishi cross-
coupling.
haemoglobin and inhibit the transport of oxygen from the
lungs. Furthermore, the gas is odourless, invisible, and flam-
mable. To enable safe handling of CO in a standard labora-
tory environment, highly specialized equipment that is cap-
able of withstanding elevated pressure is required. Thus, the
development of safer and more convenient sources of CO
for use in organic synthesis, from which the CO is released
in situ, has gained considerable interest over the past few
years. For example, several groups have developed different
CO-releasing reagents such as chloroform,[13,14] formic acid
derivatives,[13,15] aldehydes,[13,16] and acid halides.[17,18]
However, following the early report by Corey and Hegedus
All examples of the palladium-catalysed carbonylative
Negishi couplings reported in the literature use CO gas to
carry out the carbonylation, and the reaction time required
is of the order of many hours (ca. 20–30 h).[6,9–12] CO is a
highly poisonous gas, mainly due to its ability to bind to
on
the
use
of
the
hazardous
and
vol-
atile Ni(CO)4 in the aminocarbonylation reactions of vinyl
bromides,[19] safer metal carbonyls, such as Mo(CO)6
(which contains 6 equiv. of CO), have been tested as solid
sources of CO in various palladium-catalysed carbonylation
reactions.[20–23] In this paper, we have applied Mo(CO)6-as-
sisted carbonylation to palladium-catalysed Negishi cross-
coupling reactions for the first time. Furthermore, to the
best of our knowledge, microwave heating has not been
used before in carbonylative Negishi couplings. A dedicated
single-mode microwave reactor offers advantages over
[a] Organic Pharmaceutical Chemistry, Department of Medicinal
Chemistry, Uppsala Biomedical Centre, Uppsala University,
Box 574, 75123 Uppsala, Sweden
E-mail: mats@orgfarm.uu.se
Homepage: http://www.orgfarm.uu.se
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201300610.
2
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Carbonylative Negishi Cross-Couplings
traditional heating methods, including operational safety, Table 1. Optimization of reaction conditions for the palladium-cat-
and shorter reaction times.[23] In addition, microwave heat-
alysed carbonylative Negishi cross-coupling using 1-iodonaphth-
alene.[a]
ing gives a high degree of control over the reaction, and
offers the possibility of easily changing the temperature on
the fly.[24,25] We report the development of two efficient pal-
ladium-catalysed carbonylative Negishi cross-coupling pro-
tocols using aryl iodides and aryl bromides, respectively, to
rapidly produce a series of diarylated ethanones. The nov-
elty of these methods comes from the use of Mo(CO)6 as
Entry Ligand
Mo(CO)6
[equiv.]
Temp.
[°C]
Time
[min]
Yield[f]
[%]
the in situ source of CO, and the use of microwave heating
for palladium-catalysed Negishi cross-coupling reactions.
1
DPPB
DPPB
DPPB
DPPB
DPPB
DPPP
X-phos
Xantphos
DPPB
DPPB
DPPB
DPPB
DPPB
DPPB
2
2
2
2
2
2
2
2
2
2
2
1
1
1
90
90
90
90
90
90
90
90
90
70
110
90
110
90
60
60
60
60
60
60
60
60
30
60
60
60
60
120
76
54
69
33
22
53
27
31
62
61
73
51
59
62
2[b]
3[c]
4[d]
5[e]
6
Results and Discussion
Optimization for Aryl Iodides
7
8
9
10
11
12
13
14
We began our investigation by using 1-iodonaphthalene
(1a) as a model aryl iodide, and studying its reaction with
benzylzinc bromide (2a). Various reaction conditions inves-
tigated are shown in Table 1. Using a slight excess of 2a
(1.4 equiv.), a series of experiments were conducted in
which the ligand, concentration of Mo(CO)6, temperature,
and microwave heating time were varied. Benzylzinc brom-
ide was obtained commercially as a solution (0.5 m) in THF,
hence THF was chosen as the solvent. Various ligands were
tested {DPPB [1,4-bis(diphenylphosphino)butane], DPPP
[1,3-bis(diphenylphosphino)propane], X-phos [2-dicyclo-
hexylphosphino-2Ј,4Ј,6Ј-triisopropylbiphenyl], Xantphos [4,5-
bis(diphenylphosphino)-9,9-dimethylxanthene]; Table 1, en-
tries 1, 6, 7, and 8, respectively}, and the best yield was
obtained with DPPB (76%; Table 1, entry 1). The use of a
base, e.g., DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), Et3N,
or K2CO3 (Table 1, entries 3, 4, and 5, respectively), was
found to be detrimental (yields 69, 33, and 22%, respec-
tively).
When Pd(OAc)2 (10 mol-%) and DPPB (10 mol-%) were
used as the palladium catalyst and ligand, respectively, with
Mo(CO)6 (2 equiv.) under microwave irradiation at 90 °C
for 1 h, a 76% yield of deoxybenzoin 3a was obtained
(Table 1, entry 1). The carbonylative cross-coupling domi-
nated over the competing Negishi-coupling product in a ra-
tio of ca. 9:1 (cf. Scheme 1). The yield decreased compared
to that obtained in Table 1, entry 1 when the catalyst load-
[a] Reactions were performed under microwave irradiation in a
sealed vial with 1a (1 mmol), 2a (1.4 equiv.), Pd(OAc)2 (10 mol-%),
ligand (10 mol-%), and THF (4 mL), unless otherwise specified.
[b] Reaction was performed with 5 mol-% Pd(OAc)2. [c] Reaction
was performed in the presence of base DBU (2 equiv.). [d] Reaction
was performed in the presence of base Et3N (2 equiv.). [e] Reaction
was performed in the presence of base K2CO3 (2 equiv.). [f] Isolated
yields.
microwave heating), the reaction time was nearly 8 h, and
the isolated yield of compound 3a was similar (75%), dem-
onstrating the advantage of microwave heating in giving a
shorter reaction time (1 h).
Diarylated Ethanones from Aryl Iodides
Next, we investigated the scope and limitations of the
ing was reduced to 5 mol-% (Table 1, entry 2), the amount optimized protocol for aryl iodides using benzylzinc brom-
of Mo(CO)6 was reduced to 1 equiv. (Table 1, entry 12), the ide. All the reactions shown in Table 2 proceeded under mi-
heating time was reduced to 30 min (Table 1, entry 9), or crowave irradiation using a standard single-mode reactor
the temperature was reduced to 70 °C (Table 1, entry 10). with 1 h of microwave heating; more than 95% conversion
When the temperature was increased to 110 °C (Table 1, en- of 1a–k was seen, and moderate to good isolated yields (47–
try 11), a yield similar to that achieved at 90 °C (Table 1, 84%) of the corresponding 1,2-diarylethanones (i.e., 3a–k)
entry 1) was obtained. When the reaction was performed in products were obtained. 3-Iodothiophene, as a representa-
the absence of a palladium source and a ligand, less than tive example of a heteroarene, gave 61% of the desired
5% of product 3a was detected.[26] When the amount of ketone (i.e., 3j). When 4-cyanobenzylzinc bromide (2b) was
Mo(CO)6 was reduced to 1 equiv., but the temperature was used instead of 2a for the reaction with 1a, product 3k was
increased to 110 °C (Table 1, entry 13) or the reaction time obtained in moderate yield (66%), suggesting that the reac-
to 120 min (Table 1, entry 14), the yields were not higher tion protocol could also be used for substituted benzylzinc
than that obtained in Table 1, entry 1. Furthermore, when bromides. However, further experiments are needed to con-
a reaction was carried out under the conditions of Table 1, firm that various substituted benzylzinc bromides may be
entry 1 but with heating to 90 °C in an oil bath (instead of used in this protocol.
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H. V. Motwani, M. Larhed
SHORT COMMUNICATION
Table 2. Palladium-catalysed carbonylative Negishi cross-coupling
using aryl iodides.[a]
Table 3. Optimization of reaction conditions for the palladium-cat-
alysed carbonylative Negishi cross-coupling using 1-bromonaphth-
alene.[a]
Entry
Pd catalyst
Ligand
Time Temp. Yield[g]
[min]
[°C]
[%]
1
2
3
4
5
6
7
8
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
palladacycle DPPB
palladacycle X-phos
DPPB
X-phos
Xantphos
[(tBu)3PH]BF4
60
60
60
60
30
30
30
30
30
30
15
30
30
30
90
90
90
12
14
17
23
21
34
39
49
61
74
57
38
27
59
90
120
120
120
120
120
120
120
120
120
120
palladacycle Xantphos
palladacycle [(tBu)3PH]BF4
palladacycle [(tBu)3PH]BF4
palladacycle [(tBu)3PH]BF4
palladacycle [(tBu)3PH]BF4
palladacycle [(tBu)3PH]BF4
palladacycle [(tBu)3PH]BF4
palladacycle [(tBu)3PH]BF4
9[b]
10[c]
11[c]
12[d]
13[e]
14[f]
[a] Reactions were performed in a sealed vial with aryl iodides 1a–
k (1 mmol), 2a (1.4 equiv.), Mo(CO)6 (2 equiv.), Pd(OAc)2 (10 mol-
%), DPPB (10 mol-%), and THF (4 mL) under microwave irradia-
tion, unless otherwise specified. [b] 4-Cyanobenzylzinc bromide
(2b; 1.4 equiv.) was used instead of 2a.
[a] Reactions were performed under microwave irradiation in a se-
aled vial with 4a (1 mmol), 2a (1.4 equiv.), palladium source
(10 mol-%), ligand (10 mol-%), Mo(CO)6 (2 equiv.), and THF
(4 mL), unless otherwise specified. [b] Reaction was performed with
Herrmann’s palladacycle (5 mol-%). [c] Reaction was performed
with Herrmann’s palladacycle (5 mol-%) in the presence of base
DBU (3 equiv.). [d] Reaction was performed with Herrmann’s pal-
ladacycle (5 mol-%) in the presence of base Et3N (3 equiv.). [e] Re-
action was performed with Herrmann’s palladacycle (5 mol-%) in
the presence of base K2CO3 (3 equiv.). [f] Reaction was performed
with 1 equiv. Mo(CO)6 and 3 equiv. DBU. [g] Isolated yields.
Optimization for Aryl Bromides
Encouraged by the results obtained with aryl iodides, we
decided to extend the scope of our investigation by testing
aryl bromides 4 as arylpalladium precursors. This would
improve the method as aryl bromides tend to have lower
cost than the corresponding iodides, and also more aryl
bromides are commercially available. Aryl bromides are less
prone to undergo oxidative additions than iodides, so when
reaction conditions similar to those used for the aryl iodides
were tested with the bromides, the reaction did not proceed
as expected, and only a low conversion was observed (12%
yield; Table 3, entry 1). Changing the ligand {X-phos,
Xantphos, [(tBu)3PH]BF4} did not improve the yield sub-
stantially (14–23%; Table 3, entries 2–4).
yields. When the reaction conditions from Table 3, entry 10
were used with 1-chloronaphthalene and 4-chlorobenzo-
nitrile as substrates, the yields of 3a and 3i, respectively,
were very low (5–7%), which suggests that this protocol re-
quires further optimization before aryl chlorides can be
used as reaction partners.
We envisaged that a more reactive catalytic system and a
higher reaction temperature would allow the transforma-
tion to proceed efficiently. This led us to use Herrmann’s
palladacycle as the palladium source to promote the reac-
tions.[27] The palladacycle was tested with the various li-
Diarylated Ethanones from Aryl Bromides
Aryl bromides 4 substituted with different functional
gands (Table 3, entries 5–9), and the best yield was obtained groups (Table 4) were found to react under the selected re-
with [(tBu)3PH]BF4 (61%; Table 3, entry 9). In an attempt action conditions (i.e., Table 3, entry 10) with a similarly
to further improve the yield, the reaction was tested in the high chemoselectivity in favour of carbonylative Negishi
presence of a base, e.g., DBU, Et3N, or K2CO3 (Table 3, cross-coupling to what had been seen with the aryl iodides.
entries 10, 12, and 13, respectively). It was found that, in However, the conversion of the aryl bromides into the de-
contrast to the situation with aryl iodides, a base (DBU) sired product was, in general, not fully complete (ca. 90%).
improved the efficiency of the reactions of the aryl brom- Increasing the reaction time to 1 h (from 30 min) and the
ides. The highest yield of 3a was obtained using Herrmann’s temperature to 140 °C (from 120 °C) did not give a substan-
palladacycle (5 mol-%) and [(tBu)3PH]BF4 (10 mol-%) after tial increase of the conversion, but resulted instead in the
30 min of microwave irradiation at 120 °C, with DBU as formation of non-carbonylative by-products. This partly ex-
the base (74%; Table 3, entry 10). Attempts to reduce the plains the somewhat lower yields (49–81%) obtained for the
reaction time to 15 min (Table 3, entry 11), or the amount reactions with the aryl bromides (Table 4) compared to
of Mo(CO)6 to 1 equiv. (Table 3, entry 14) led to lower those obtained with the aryl iodides (Table 2).
4
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Carbonylative Negishi Cross-Couplings
1-(o-tolyl)ethanone (3c);[29] 2-phenyl-1-[4-(trifluoromethyl)phenyl]-
Table 4. Palladium-catalysed carbonylative Negishi cross-coupling
using aryl bromides.[a]
ethanone
(3d);[30,31]
1-(4-isopropylphenyl)-2-phenylethanone
(3e);[32,33] 1-(3-methoxyphenyl)-2-phenylethanone (3f);[29] 1-(4-hy-
droxyphenyl)-2-phenylethanone (3g);[34] 1-(4-methoxyphenyl)-2-
phenylethanone (3h);[28,29] 4-(2-phenylacetyl)benzonitrile (3i);[31] 2-
phenyl-1-(thiophen-3-yl)ethanone (3j);[6] and 4-[2-(naphthalen-1-
yl)-2-oxoethyl]benzonitrile (3k).[35] Yields are given in Tables 2 and
4.
Supporting Information (see footnote on the first page of this arti-
1
cle): Experimental details, H and 13C NMR spectra, and chroma-
tograms for all products.
Acknowledgments
The authors thank the Swedish Research Council for financial sup-
port and Apotekarsocieteten for awarding the Elisabeth och Alfred
Ahlqvist stiftelse to H. V. M.
[1] N. Carril, R. SanMartin, E. Dominguez, I. Tellitu, Tetrahedron
2007, 63, 690–702.
[2] R. Olivera, R. SanMartin, F. Churruca, E. Dominguez, J. Org.
Chem. 2002, 67, 7215–7225.
[a] Reactions were performed in a sealed vial with aryl bromides
4a–k (1 mmol), 2a (1.4 equiv.), Mo(CO)6 (2 equiv.), Herrmann’s
palladacycle (5 mol-%), [(tBu)3PH]BF4 (10 mol-%), DBU
(3 equiv.), and THF (4 mL) under microwave irradiation, unless
otherwise specified. [b] 4-Cyanobenzylzinc bromide (2b; 1.4 equiv.)
was used instead of 2a.
[3] M. Lamblin, A. Couture, E. Deniau, P. Grandclaudon, Org.
Biomol. Chem. 2007, 5, 1466–1471.
[4] P. Nilsson, M. Larhed, A. Hallberg, J. Am. Chem. Soc. 2001,
123, 8217–8225.
[5] J. Savmarker, J. Lindh, P. Nilsson, Tetrahedron Lett. 2010, 51,
6886–6889.
[6] X. F. Wu, J. Schranck, H. Neumann, M. Beller, Chem. Asian
J. 2012, 7, 40–44.
Conclusions
[7] P. Nilsson, K. Olofsson, M. Larhed, in: Topics in Current
Chemistry, vol. 266: Microwave Methods in Organic Synthesis
(Eds.: M. Larhed, K. Olofsson), Springer, Heidelberg, Ger-
many, 2006, p. 103–144.
New, convenient and efficient palladium-catalysed carb-
onylative Negishi cross-coupling protocols have been devel-
oped. Aryl halides (iodides or bromides) are treated with
benzylzinc bromide in the presence of Mo(CO)6 under mi-
crowave heating. A broad array of diarylated ethanones
were produced with high chemoselectivity and in moderate
to high (47–84%) isolated yields using these single-vial
methods optimized for either aryl iodides or aryl bromides.
To the best of our knowledge, this is the first report to pres-
ent carbonylative Negishi cross-coupling reactions in which
a solid CO source has been used. In comparison to classical
[8] X.-F. Wu, H. Neumann, M. Beller, Chem. Soc. Rev. 2011, 40,
4986–5009.
[9] Y. Tamaru, H. Ochiai, Y. Yamada, Z. Yoshida, Tetrahedron
Lett. 1983, 24, 3869–3872.
[10] K. Yasui, K. Fugami, S. Tanaka, Y. Tamaru, J. Org. Chem.
1995, 60, 1365–1380.
[11] B. M. O’Keefe, N. Simmons, S. F. Martin, Org. Lett. 2008, 10,
5301–5304.
[12] R. F. W. Jackson, D. Turner, M. H. Block, J. Chem. Soc. Perkin
Trans. 1 1997, 865–870.
carbonylative Negishi cross-coupling reactions that use CO [13] T. Morimoto, K. Kakiuchi, Angew. Chem. 2004, 116, 5698–
5706; Angew. Chem. Int. Ed. 2004, 43, 5580–5588.
gas, the use of a solid CO source [Mo(CO)6] is safer, easier,
and faster. Furthermore, the rate of the reactions was signif-
icantly enhanced by using microwave irradiation for heat-
[14] V. V. Grushin, H. Alper, Organometallics 1993, 12, 3846–3850.
[15] D. N. Sawant, Y. S. Wagh, K. D. Bhatte, B. M. Bhanage, J. Org.
Chem. 2011, 76, 5489–5494.
ing. In view of the short reaction times and the robustness
of the methods, we anticipate that our work will facilitate
the preparation of diarylated ethanone derivatives for
various future medicinal-chemistry-related applications.
[16] T. Shibata, N. Toshida, K. Takagi, Org. Lett. 2002, 4, 1619–
1621.
[17] P. Hermange, A. T. Lindhardt, R. H. Taaning, K. Bjerglund,
D. Lupp, T. Skrydstrup, J. Am. Chem. Soc. 2011, 133, 6061–
6071.
[18] P. Hermange, T. M. Gogsig, A. T. Lindhardt, R. H. Taaning,
T. Skrydstrup, Org. Lett. 2011, 13, 2444–2447.
[19] E. J. Corey, L. S. Hegedus, J. Am. Chem. Soc. 1969, 91, 1233–
1234.
Experimental Section
Caution: Pressurized carbonylation reactions should be carried out
using appropriate and safe equipment, such as the microwave reac-
tor used in this study. CO is a poisonous gas, so all reactions involv-
ing CO should be carried out in well-ventilated fume hoods, prefer-
ably with a CO detector to warn of any exposure.
[20] M. A. Herrero, J. Wannberg, M. Larhed, Synlett 2004, 2335–
2338.
[21] N. F. K. Kaiser, A. Hallberg, M. Larhed, J. Comb. Chem. 2002,
4, 109–111.
[22] J. Wannberg, M. Larhed, J. Org. Chem. 2003, 68, 5750–5753.
[23] L. R. Odell, F. Russo, M. Larhed, Synlett 2012, 685–698.
[24] J. Gising, L. R. Odell, M. Larhed, Org. Biomol. Chem. 2012,
10, 2713–2729.
The compounds synthesized were: 1-(naphthalen-1-yl)-2-phenyl-
ethanone (3a);[28] 2-phenyl-1-(p-tolyl)ethanone (3b);[28,29] 2-phenyl-
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SHORT COMMUNICATION
[25] P. Nilsson, H. Gold, M. Larhed, A. Hallberg, Synthesis 2002,
11, 1611–1614.
[26] B. Roberts, D. Liptrot, L. Alcaraz, T. Luker, M. J. Stocks, Org.
Lett. 2010, 12, 4280–4283.
[31] A. Takemiya, J. F. Hartwig, J. Am. Chem. Soc. 2006, 128,
14800–14801.
[32] R. S. Shadbolt, D. R. Woodward, P. J. Birchwood, J. Chem.
Soc. Perkin Trans. 1 1976, 1190–1195.
[27] O. Lagerlund, M. Larhed, J. Comb. Chem. 2006, 8, 4–6.
[28] T. Miao, G. W. Wang, Chem. Commun. 2011, 47, 9501–9503.
[29] K. Huang, G. Li, W. P. Huang, D. G. Yu, Z. J. Shi, Chem. Com-
mun. 2011, 47, 7224–7226.
[30] A. J. Wommack, D. C. Moebius, A. L. Travis, J. S. Kingsbury,
Org. Lett. 2009, 11, 3202–3205.
[33] E. Muller, R. Heischkeil, Tetrahedron Lett. 1964, 5, 2809–2812.
[34] G. K. S. Prakash, C. Panja, T. Mathew, G. A. Olah, Catal. Lett.
2007, 114, 24–29.
[35] G. Wagner, B. Voigt, Pharmazie 1976, 31, 432–436.
Received: April 26, 2013
Published Online: ᭿
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