Kumada cross-coupling of aryl Grignard reagents with aryl halides catalyzed by an immobilized nickel catalyst

Article abstract of DOI:10.1055/s-0029-1216832

The Kumada cross-coupling reaction of a variety of unactivated aryl bromides and aryl chlorides with phenylmagnesium bromide has been developed. The reaction is catalyzed by an immobilized nickel(II) complex containing a pyrrolidine unit, which is part of a bidentate nitrogen ligand. The catalyst is highly efficient for the Kumada reaction, which proceeds smoothly at 10 °C to generate the corresponding products in good to excellent yields. In addition, the catalyst can be reused five times without significant loss of activity. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0029-1216832

2
408
PAPER
Kumada Cross-Coupling of Aryl Grignard Reagents with Aryl Halides
Catalyzed by an Immobilized Nickel Catalyst
a
g Chen, Lei Wang,* Jie Liu
a,b
a
K
X
umada
C
ross-Co
i
upling
a
of
A
ryl
G
ri
o
gnard Reage
f
nts
w
ith
a
A
ryl
H
alide
n
s
a
Department of Chemistry, Huaibei Coal Teachers College, Huaibei, Anhui 235000, P. R. of China
b
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, P. R. of China
Fax +86(561)3090518; E-mail: leiwang@hbcnc.edu.cn
Received 22 January 2009; revised 17 March 2009
novel synthetic strategies for carbon–carbon bond-forma-
Abstract: The Kumada cross-coupling reaction of a variety of un-
activated aryl bromides and aryl chlorides with phenylmagnesium
bromide has been developed. The reaction is catalyzed by an immo-
bilized nickel(II) complex containing a pyrrolidine unit, which is
14
tion reactions, we have carried out the research reported
herein, showing that immobilized nickel(II), coordinated
by a new kind of bidentate ligand, can be a much more ef-
part of a bidentate nitrogen ligand. The catalyst is highly efficient fective heterogenized catalyst for Kumada coupling reac-
for the Kumada reaction, which proceeds smoothly at 10 °C to gen- tions.
erate the corresponding products in good to excellent yields. In ad-
The synthesis of the organic–inorganic hybrid-material-
immobilized nickel catalyst is illustrated in Scheme 1.
The desired catalyst material ‘silica-APTS-Pyr-Ni(II)’
dition, the catalyst can be reused five times without significant loss
of activity.
Key words: Kumada cross-coupling, immobilized nickel(II) com-
plex, bidentate nitrogen ligands, Grignard reagents, aryl halides
[
APTS = (3-aminopropyl)triethoxysilane; Pyr = pyrroli-
din-2-ylmethyl] was readily prepared by a multistep pro-
cedure and subsequently used for Kumada reactions of
aryl bromides and aryl chlorides with phenylmagnesium
bromide in tetrahydrofuran. To our delight, the reactions
can generate the corresponding products in good to excel-
lent yields. It is worth noting that the silica-supported
nickel(II) catalyst can be recycled by a simple filtration of
the reaction solution and used for five consecutive trials
without significant loss of activity.
The cross-coupling of Grignard reagents with aryl halides
(
Kumada reaction) catalyzed by a nickel complex repre-
sents a very useful and synthetic method to produce un-
1
symmetric biaryls. Recently, a numbers of nickel and
palladium complexes have been employed in the Kumada
2
reaction with great success. Ever-increasing environmen-
tal concern has resulted in much attention being directed
recently toward the development of new environmentally In our initial screening experiments, the activity of the im-
friendly catalysts for the Kumada reaction. Initially, the mobilized nickel catalyst silica-APTS-Pyr-Ni(II) was
catalysts have mainly been nickel complexes with phos- tested (Table 1). It has been reported that the order of the
3
4
phine ligands, e.g. [NiCl (PPh ) ], [NiCl (PCy ) ], and addition of the reagents has some influence on the Kuma-
2
3 2
2
3 2
15
NiCl L (L = dppe, dppp, dppf). More recently, new het- da reaction, and therefore we followed the following
erogeneous nickel catalysts, such as polymer-supported protocol for the reaction. A small Schlenk tube was
2
5
6
nickel, nickel on charcoal, nickel/nanoporous carbon charged with the silica-APTS-Pyr-Ni catalyst (48 mg, 2
7
materials, and N-heterocylic carbene-based nickel(II) mol% catalyst, loading 0.21 mmol/g), the appropriate aryl
8
complexes, have been used for this transformation.
halide (0.50 mmol), and anhydrous tetrahydrofuran (2.0
Among the heterogeneous nickel catalysts, organic–inor- mL) under an anhydrous nitrogen atmosphere. The mix-
ganic hybrid-material-supported catalysts have played a ture was allowed to stir at 10 °C for five minutes before
great role in the area of coupling reactions and aroused the reaction was initiated by the dropwise addition by sy-
9,10
great interest among chemists. Both unsupported and ringe of a phenylmagnesium bromide solution (0.75
1
supported
1,12
bidentate nitrogen ligands have been report- mmol) in tetrahydrofuran (2.0 mL); the reaction was then
ed to be effective in this kind of reaction. A number of pa- allowed to run for 12 hours at 10 °C. Table 1 shows that
pers have described that an excess of Grignard reagent can when one mole-percent of catalyst was used, the reaction
reduce nickel(II) to nickel(0) during the course of the cat- did not go to completion (Table 1, entry 1), but that a
6
b,13
alytic cross-coupling reaction.
As part of our program higher loading of the catalyst of two mole-percent gave a
aimed at developing selective and environmentally good result (Table 1, entry 2). However, with an increased
friendly methodologies using organic–inorganic hybrid- loading of the catalyst of up to three mole-percent there
material-supported catalysts for the preparation of fine was no increase in the isolated yield of the desired product
chemicals and in continuation of our interest in exploring (Table 1, entry 3). Thus, two mole-percent catalyst is
enough to accomplish this reaction. Although the Grig-
nard reagent used for this reaction is very reactive, there
SYNTHESIS 2009, No. 14, pp 2408–2412
x
x.
x
x
.
2
0
0
9
was little side reaction. This shows that the bidentate ni-
trogen ligand containing the pyrrolidine unit is a good
type of ligand for the Kumada cross-coupling reaction.
Advanced online publication: 27.05.2009
DOI: 10.1055/s-0029-1216832; Art ID: F02809SS
Georg Thieme Verlag Stuttgart · New York
©

PAPER
Kumada Cross-Coupling of Aryl Grignard Reagents with Aryl Halides
2409
O
OH
OH
O
O
O
Si
NH2
Boc-Pro-OH
O
Si
N
H
(
EtO)3Si(CH2)3NH2
APTS)
OH
OH
O
O
N
(
Boc
OH
OH
toluene
120 °C
Et N, THF
3
0 °C
OH
OH
OH
OH
OH
OH
silica
silica-APTS
silica-APTS-Boc-Pro
TFA
CH2Cl2
0
°C
O
O
O
O
O
O
O
O
Si
HN
Ni
Si
N
H
Si
N
H
N
H
O
HN
O
HN
NiCl2
NaBH4, I2
Cl
OH
OH
Cl
DMF
r.t.
THF
0 °C then
OH
OH
OH
OH
OH
OH
7
0 °C
OH
silica-APTS-Pyr-Ni(II)
silica-APTS-Pyr
silica-APTS-Pro
Pyr = pyrrolidin-2-ylmethyl
Scheme 1
a
Table 1 Effect of Catalyst Loading on the Kumada Reaction
Ni cat.
MeO
Br +
MgBr
MeO
THF, 10 °C, 12 h
b
Yield (%)
Entry
Catalyst loading (mol%)
1
2
1.0
2.0
3.0
77
91
92
3
a
Reagents and conditions: PMPBr (0.50 mmol), silica-APTS-Pyr-Ni (cat.), PhMgBr (0.75 mmol), THF (2.0 mL), 10 °C, 12 h.
Isolated yield.
b
Thus, the optimized reaction conditions for the Kumada group in the aryl bromide (Table 2, entries 3 and 7); in
reaction consist of the following: silica-APTS-Pyr-Ni (2 comparison, the position of the nitro substituent had no in-
mol%), aryl halide (0.50 mmol), phenylmagnesium bro- fluence on the Kumada reaction of aryl chlorides (Table 2,
mide (0.75 mmol), tetrahydrofuran (2.0 mL), 10 °C, 12 entries 11 and 13). It may be that the nitro-substituted aryl
hours.
bromide was more active than the nitro-substituted aryl
chloride. In addition, the coupling reaction of o-tolyl bro-
mide gave lower conversion than the p-tolyl bromide as a
result of steric hindrance (Table 2, entries 6 vs 9). It is
worth noting that some substituents with electron-with-
drawing groups that could have been very sensitive to the
Grignard reagent also gave the desired products in good
yields (Table 2, entries 1, 4, 5, 10, and 12).
Next, the synthetic scope of the cross-coupling of various
aryl bromides and aryl chlorides with phenylmagnesium
bromide solution under the optimized reaction conditions
was investigated (Table 2). It was found that electron-
neutral, electron-poor, as well as electron-rich aryl bro-
mides react very well with phenylmagnesium bromide to
generate the corresponding cross-coupling products in
good to excellent yields under the established reaction In addition, the recyclability of the silica-APTS-Pyr-Ni
conditions (Table 2, entries 1–9). For electron-neutral, catalyst was also examined after the completion of the
electron-rich, as well as electron-poor aryl chlorides, Kumada reaction of 4-bromoanisole with phenylmagne-
moderate to good yields of the desired products were ob- sium bromide solution. The organic reaction solution
tained (Table 2, entries 10–14). The position of the cyano (containing 48 mg of silica-APTS-Pyr-Ni, catalyst load-
group on the aryl bromide did not have an effect on the ing 0.21mmol/g) was filtered through a sintered glass fun-
outcome of the reaction (Table 2, entries 4 and 5). How- nel, and the solid was washed sequentially with ethanol
ever, there was an obvious positional effect of the nitro (2 × 5 mL), dichloromethane (2 × 5 mL), and acetone (2 ×
Synthesis 2009, No. 14, 2408–2412 © Thieme Stuttgart · New York

2
410
X. Chen et al.
PAPER
a
Table 2 Effect of Substrates on the Kumada Reaction
R
R
Ni cat. (2 mol%)
X +
MgBr
THF, 10 °C, 12 h
b
Yield (%)
Entry
ArX
1
2
3
4
5
6
7
4-AcC H Br
6
74
90
93
81
83
91
83
4
PMPBr
4-O NC H Br
2
6
4
4-NCC H Br
6
4
Figure 1 Yields obtained with recycled silica-APTS-Pyr-Ni cata-
lyst (model reaction under standard reaction conditions: PMPBr,
PhMgBr, 10 °C, 12 h)
3-NCC H Br
4
6
4-TolBr
3-O NC H Br
2
6
4
(2 mol%) in anhydrous tetrahydrofuran at 10 °C for 12
hours under a nitrogen atmosphere and generate the corre-
sponding biaryls in good to excellent yields. In addition,
the silica-APTS-Pyr-Ni catalyst can be used for five con-
secutive trials without significant loss of activity.
Br
8
9
81
N
2-MeC H Br
6
76
70
88
74
86
85
4
1
1
1
1
0
1
2
3
4
4-AcC H Cl
6 4
Melting points were recorded on a WRS-2B melting point apparatus
1
and are uncorrected. H NMR spectra were recorded on a Bruker
4-O NC H Cl
2
6
4
3
00-MHz, 400-MHz, or 500-MHz FT-NMR spectrometer. Chemi-
4-NCC H Cl
6
cal shifts are given relative to TMS as internal standard. IR spectra
were obtained on a Nicolet NEXUS 470 spectrophotometer. Prod-
ucts were purified by flash column chromatography (silica gel,
4
3-O NC H Cl
2
6
4
2
30–400 mesh). The chemicals were purchased from commercial
1
4-TolCl
suppliers (Aldrich, USA and Shanghai Chemical Company, China)
and used without further purification prior to use.
a
Reagents and conditions: ArX (0.50 mmol), silica-APTS-Pyr-Ni
2 mol%, cat. loading 0.21 mmol/g), PhMgBr (0.75 mmol), THF (2.0
mL), 10 °C, 12 h.
(
Silica-APTS
A 50-mL three-necked round-bottomed flask with a Dean–Stark
trap was loaded in succession with anhyd toluene (20 mL), activated
b
Isolated yield.
1
6
silica (3.0 g, prepared by a literature procedure ), and (3-aminopro-
pyl)triethoxysilane (APTS; 10 mL). The mixture was refluxed at
5
mL). After being dried in the oven at 60 °C for ten
hours, the catalyst could be reused directly without further
purification. The silica-APTS-Pyr-Ni catalyst could be re-
1
tone (10 mL) followed by CH Cl (10 mL) and dried overnight un-
20 °C for 24 h, and then filtered; the solid was washed with ace-
2
2
covered and reused for five consecutive trials without loss der reduced pressure at 60 °C. Thus silica-APTS was obtained;
of activity (Figure 1). When the recycled catalyst was yield: 3.36 g; loading (by CHN microanalysis): 0.512 mmol of ami-
nopropyl groups/g (based on the nitrogen percentage).
used for more than five times, there was a significant de-
activation of the supported catalyst along with a color
Silica-APTS-Boc-Pro
change to dark grayish; this is presumably the result of the
formation of nickel powder and nickel oxide on the sur-
face of the organic–inorganic hybrid support. Nickel
Boc-L-proline (301 mg, 1.4 mmol) and Et N (141 mg, 1.4 mmol)
3
were dissolved in THF (10 mL). The resulting soln was cooled to
0
°C, and ClCO Et (154 mg, 1.4 mmol) was added dropwise over
2
leaching from the silica-APTS-Pyr-Ni catalyst was also 10 min. After the soln had stirred for 30 min, silica-APTS (2.735 g,
determined. Atomic absorption spectroscopy analysis of 0.512 mmol aminopropyl groups/g) was added, and then the result-
ing mixture was stirred at 0 °C for 1 h, at r.t. for another 16 h, and
the clear filtrates obtained by filtration after the reaction
finally refluxed for 3 h. After cooling to r.t., the mixture was filtered
indicated a nickel content of less than 0.5 ppm. Also, only
and successively washed with THF (10 mL), EtOH (10 mL), and
a trace amount of the desired product was isolated for the
EtOAc (10 mL), and then dried under vacuum. This gave silica-
model reaction if substrates were added to a filtrate ob-
ATPS-Boc-Pro; yield: 2.931 g; loading (by CHN microanalysis):
tained after the filtration of the immobilized catalyst after
a reaction.
0
.336 mmol/g (based on the nitrogen percentage).
Silica-APTS-Pyr
A 10-mL round-bottomed flask was successively loaded with TFA
In conclusion, we have developed a highly efficient and
recoverable organic–inorganic hybrid-material-immobi-
lized nickel catalyst (silica-APTS-Pyr-Ni) for the Kuma-
(5 mL) and CH Cl (5 mL), and then the mixture was stirred. After
addition of silica-APTS-Boc-Pro (2.7 g), the mixture was stirred for
2 2
da reaction. The cross-coupling reactions of a variety of 2.5 h in an ice bath. The mixture was filtered and the solid was
unactivated aryl bromides and aryl chlorides with phenyl- washed with CH Cl (10 mL) and dried under vacuum; this gave the
2
2
corresponding Boc-deprotected product silica-APTS-Pro; yield: 2.5
g.
magnesium bromide are catalyzed by silica-APTS-Pyr-Ni
Synthesis 2009, No. 14, 2408–2412 © Thieme Stuttgart · New York

PAPER
Kumada Cross-Coupling of Aryl Grignard Reagents with Aryl Halides
2411
1
In a 50-mL round-bottomed flask were introduced successively the
thus obtained Boc-deprotected product (2.5 g), NaBH (127 mg),
H NMR (300 MHz, CDCl ): d = 2.38 (s, 3 H), 7.24 (d, J = 8.1 Hz,
3
2 H), 7.32 (m, 1 H), 7.41 (t, J = 7.5 Hz, 2 H), 7.48 (d, J = 8.1 Hz, 2
H), 7.56 (d, J = 7.5 Hz, 2 H).
4
and anhyd THF (25 mL), and then the mixture was cooled to 0 °C
overnight. After a soln of I (160 mg) in THF (5 mL) had been add-
2
13
C NMR (75 MHz, CDCl ): d = 21.2, 127.1, 128.8, 129.6, 137.1,
3
ed, the soln was refluxed for 48 h. Then it was cooled to r.t., the mix-
ture was filtered, and the solid was washed successively with THF
1
38.5, 141.3.
(
10 mL), EtOH (10 mL), and EtOAc (10 mL), and then it was dried
3
-Nitrobiphenyl
Mp 58–60 °C (Lit. 61 °C).
under reduced pressure until the weight remained constant. This
gave the organic–inorganic hybrid material silica-APTS-Pyr; yield:
2.4 g; loading (by CHN microanalysis): 0.218 mmol/g (based on the
nitrogen percentage).
20
1
H NMR (300 MHz, CDCl ): d = 7.52 (m, 3 H), 7.63 (m, 3 H), 7.95
3
(m, 2 H), 8.46 (s, 1 H).
1
3
–
IR (KBr): 1101 (Si–O), 2937 (C–H), 3330 (N–H) cm .
1
C NMR (75 MHz, CDCl ): d = 122.6, 127.5, 129.0, 129.7, 133.4,
3
1
36.8, 137.6, 148.7.
Silica-APTS-Pyr-Ni Catalyst
In a small Schlenk tube, NiCl (26 mg, 0.2 mmol) was dissolved in
3-Cyanobiphenyl
Pale yellow solid.
2
2
1
anhyd DMF (10 mL), and then silica-APTS-Pyr (920 mg) was add-
ed and the suspension was stirred for 10 h under a N atmosphere at
1
2
H NMR (500 MHz, CDCl ): d = 7.42–7.59 (m, 7 H), 7.65 (m, 1 H),
3
r.t. The soln was filtered and the solid was successively washed with
DMF (5 mL) and acetone (5 mL), and then dried under reduced
pressure at r.t. overnight; this gave the silica-APTS-Pyr-Ni catalyst
as a pale yellow powder; yield: 945 mg; 1.24 wt% Ni (based on
atomic absorption spectroscopy analysis).
7
.77 (dd, J = 1.0, 8.0 Hz, 1 H).
1
3
C NMR (125 MHz, CDCl ): d = 111.1, 118.6, 127.9, 128.7, 130.3,
3
1
33.2, 133.6, 138.4, 145.8.
4
Mp 90–92 °C (Lit. 89–90 °C).
-Methoxybiphenyl
22
–
1
IR (KBr): 1081 (Si–O), 2936 (C–H), 3327 (N–H) cm .
1
H NMR (400 MHz, CDCl ): d = 3.86 (s, 3 H), 6.98 (d, J = 9.0 Hz,
3
Kumada Cross-Coupling Reaction; General Procedure
2 H), 7.31 (t, J = 7.5 Hz, 1 H), 7.42 (t, J = 7.8 Hz, 2 H), 7.54 (t,
J = 8.4 Hz, 4 H).
A small Schlenk tube was charged successively with the silica-
APTS-Pyr-Ni catalyst (25 mg; 0.005 mmol Ni), the aryl halide (0.25
mmol), and anhyd THF (1.0 mL). The mixture was stirred for 5 min
before the catalytic reaction was initiated by the dropwise addition
by syringe of the Grignard reagent (0.375 mmol) in THF (1.0 mL)
at 10 °C. The reaction was quenched by the addition of MeOH (1.0
mL). The crude product was purified by column chromatography.
1
3
C NMR (100 MHz, CDCl ): d = 55.5, 114.4, 126.8, 126.9, 128.3,
3
128.8, 133.9, 141.0, 159.3.
3-Phenylpyridine
2
Yellow oil.
3
1
H NMR (400 MHz, CDCl ): d = 7.43–7.35 (m, 2 H), 7.49 (t,
3
Recycling the Silica-APTS-Pyr-Ni Catalyst
J = 7.2 Hz, 2 H), 7.60 (d, J = 8.4 Hz, 2 H), 7.88 (d, J = 12.0 Hz, 1
H), 8.59 (d, J = 6.4 Hz, 1 H), 8.85 (s, 1 H).
After the reaction had been carried out, the mixture (containing 25
mg of silica-APTS-Pyr-Ni) was filtered through a sintered glass
funnel and washed successively with EtOH (2 × 5 mL), CH Cl
1
3
C NMR (100 MHz, CDCl ): d = 123.0, 127.1, 128.1, 129.0, 134.3,
3
2
2
1
36.6, 137.8, 148.3, 148.4.
(
2 × 5 mL), and acetone (2 × 5 mL). After being dried in an oven at
0 °C for 10 h, the catalyst can be reused directly without further
purification.
6
2
Oil.
-Methylbiphenyl
2
4
1
4
Mp 120–121 °C (Lit. mp 119 °C).
-Phenylacetophenone
7
H NMR (400 MHz, CDCl ): d = 2.29 (s, 3 H), 7.36–7.27 (m, 9 H).
3
1
1
3
C NMR (100 MHz, CDCl ): d = 20.5, 125.7, 126.7, 127.3, 128.1,
3
1
H NMR (300 MHz, CDCl ): d = 2.63 (s, 3 H), 7.42 (m, 1 H), 7.47
3
129.2, 129.9, 130.3, 135.2, 141.8.
(m, 2 H), 7.63 (m, 2 H), 7.68 (m, 2 H), 8.03 (m, 2 H).
1
3
C NMR (75 MHz, CDCl ): d = 26.7, 127.2, 127.3, 128.2, 128.9,
3
References
1
29.0, 133.9, 139.9, 145.7, 197.7.
(
1) (a) Tamao, K.; Sumitani, K.; Kumada, M. J. Am. Chem. Soc.
972, 94, 4374. (b) Kumada, M.; Tamao, K.; Sumitani, K.
Org. Synth. 1978, 58, 127.
(2) (a) Montgomery, J. Angew. Chem. Int. Ed. 2004, 43, 3890.
b) Bedford, R. B.; Cazin, C. S. J.; Holder, D. Coord. Chem.
4-Nitrobiphenyl
Mp 113–114 °C (Lit. 113–114 °C).
1
1
8
1
H NMR (300 MHz, CDCl ): d = 7.44 (m, 3 H), 7.61 (m, 2 H), 7.73
3
(
(
d, J = 8.9 Hz, 2 H), 8.29 (d, J = 8.9 Hz, 2 H).
Rev. 2004, 248, 2283. (c) Espinet, P.; Echavarren, A. M.
Angew. Chem. Int. Ed. 2004, 43, 4704.
3) (a) Wenkert, E.; Michelotti, E. L.; Swindell, C. S. J. Am.
Chem. Soc. 1979, 101, 2246. (b) Wenkert, E.; Michelotti,
E. L.; Swindell, C. S.; Tingoli, M. J. Org. Chem. 1984, 49,
1
3
C NMR (75 MHz, CDCl ): d = 124.1, 127.4, 127.8, 129.0, 129.2,
3
1
38.8, 147.7.
(
4-Cyanobiphenyl
Mp 85–86 °C (Lit. 84–86 °C).
19
4894.
1
H NMR (300 MHz, CDCl ): d = 7.44–7.48 (m, 3 H), 7.60 (m, 2 H),
3
(4) (a) Booth, G.; Chatt, J. J. Chem. Soc. 1965, 3238.
(b) Ozawa, F. In Synthesis of Organometallic Compounds: A
Practical Guide; Komiya, S., Ed.; Wiley: Chichester, 1997,
Chap. 12, 249.
7
.67–7.75 (m, 4 H).
1
3
C NMR (75 MHz, CDCl ): d = 110.8, 118.9, 127.2, 127.7, 128.7,
3
1
29.1, 132.6, 139.1, 145.6.
(
5) Styring, P.; Grindon, C.; Fisher, C. M. Catal. Lett. 2001, 77,
19.
2
4-Methylbiphenyl
Mp 45–46 °C (Lit. 44.5–46.5 °C).
19
Synthesis 2009, No. 14, 2408–2412 © Thieme Stuttgart · New York

2
412
X. Chen et al.
PAPER
(15) Lipshutz, B. H.; Senguota, S. Org. React. 1992, 41, 135.
(16) (a) Li, P.; Wang, L. Adv. Synth. Catal. 2006, 348, 681.
(b) Miao, T.; Wang, L. Tetrahedron Lett. 2007, 48, 95.
(c) Li, P.; Wang, L. Tetrahedron 2007, 63, 5455.
(17) Mowery, M. E.; Deshong, P. J. Org. Chem. 1999, 64, 3266.
(18) Mino, T.; Saito, T.; Sakamoto, M.; Fujita, T. J. Org. Chem.
2006, 71, 9499.
(19) Tao, B.; Boykin, D. W. J. Org. Chem. 2004, 69, 4330.
(20) Pourbaix, C.; Carreaux, F.; Carboni, B. Org. Lett. 2001, 3,
803.
(21) Riguet, E.; Alami, M.; Cahiez, G. J. Organomet. Chem.
2001, 624, 376.
(
(
6) (a) Lipshutz, B. H.; Tasler, S.; Chrisman, W.; Spliethoff, B.;
Tesche, B. J. Org. Chem. 2003, 68, 1177. (b) Tasler, S.;
Lipshutz, B. H. J. Org. Chem. 2003, 68, 1190.
7) Park, S. Y.; Kang, M.; Yie, J. E.; Kim, J. M.; Lee, I.-M.
Tetrahedron Lett. 2005, 46, 2849.
(
(
8) Xi, H.; Liu, B.; Chen, W. J. Org. Chem. 2008, 73, 3954.
9) Mino, T.; Shirae, Y.; Sasai, Y.; Sakamoto, M.; Fujita, T.
J. Org. Chem. 2006, 71, 6834.
(
(
(
10) Cui, X.; Li, Z.; Tao, C.-Z.; Xu, Y.; Li, J.; Liu, L.; Guo,
Q.-X. Org. Lett. 2006, 8, 2467.
11) Karimi, B.; Zamani, A.; Clark, J. H. Organometallics 2005,
2
4, 4695.
12) Karimi, B.; Abedi, S.; Clark, J. H.; Budarin, V. Angew.
Chem. 2006, 118, 4894.
(22) Cho, S. D.; Kim, H. K.; Yoon, Y. J. Tetrahedron 2007, 63,
1345.
(
(
13) Lipshutz, B. H. Adv. Synth. Catal. 2001, 343, 313.
14) (a) Wang, M.; Li, P.; Wang, L. Eur. J. Org. Chem. 2008,
(23) Lerebours, R.; Wolf, C. Synthesis 2005, 2287.
(24) Bei, X.; Turner, H. W.; Weinberg, W. H.; Guram, A. S.
J. Org. Chem. 1999, 64, 6797.
2255. (b) Li, P.; Wang, L.; Zhang, Y. Tetrahedron 2008, 64,
10825. (c) Li, P.; Wang, L.; Zhang, Y.; Wang, G.
Tetrahedron 2008, 64, 7633. (d) Liu, H.; Wang, L.; Li, P.
Synthesis 2008, 2405. (e) Wu, Q.; Wang, L. Synthesis 2008,
2007. (f) Miao, T.; Wang, L. Synthesis 2008, 363.
(
g) Wang, Z.; Wang, L.; Li, P. Synthesis 2008, 1367.
Synthesis 2009, No. 14, 2408–2412 © Thieme Stuttgart · New York