Characterization of the nucleophilic allylindium species generated from allyl bromide and indium(0) in aqueous media

Article abstract of DOI:10.1002/ejoc.201000956

The reductive system of allyl bromide and indium (0) in water generated monoallylindium(III) dibromide and diallylindium(III) bromide. These compounds were characterized by X-ray analysis after complexation with 3, 5-dibromopyridine or 4-(dimethylamino)pyridine, respectively. Both isolated complexes showed high nucleophilicity and reacted with benzaldehyde to give the allylation product. The diallylindium(III) bromide was less stable in water than the monoallylindium(III) dibromide. The reaction of the diallylindium(III) with benzhydrol gave a (μ-alkoxido)indium species that showed nucleophilicity. This result suggests that allyl(μhydroxido)indium also acted as a nucleophile in an aqueous Barbie-type reaction system.

Full text of DOI:10.1002/ejoc.201000956

SHORT COMMUNICATION
DOI: 10.1002/ejoc.201000956
Characterization of the Nucleophilic Allylindium Species Generated from Allyl
Bromide and Indium(0) in Aqueous Media
Makoto Yasuda,*[a,b] Masahiko Haga,[a] Yasunori Nagaoka,[a] and Akio Baba*[a]
Keywords: Indium / Allylation / Aqueous media / X-ray analysis / Reduction
The reductive system of allyl bromide and indium(0) in water
generated monoallylindium(III) dibromide and diallylin-
dium(III) bromide. These compounds were characterized by
X-ray analysis after complexation with 3,5-dibromopyridine
or 4-(dimethylamino)pyridine, respectively. Both isolated
complexes showed high nucleophilicity and reacted with
benzaldehyde to give the allylation product. The diallylin-
dium(III) bromide was less stable in water than the mono-
allylindium(III) dibromide. The reaction of the diallylin-
dium(III) with benzhydrol gave a (µ-alkoxido)indium species
that showed nucleophilicity. This result suggests that allyl(µ-
hydroxido)indium also acted as a nucleophile in an aqueous
Barbie-type reaction system.
required. There is still a serious lack of research on unsub-
stituted allylindium compounds (namely allylindium itself)
in aqueous media. In the present study, we used X-ray crys-
tallographic analysis to characterize the unsubstituted al-
lylindium compound generated in water, and based on these
data we speculate on the active species involved in the reac-
tion course.
Introduction
Allylindium compounds have been widely employed for
effective carbon–carbon bond formation.[1,2] There are two
methods by which allylindium compounds are generated:
transmetalation[3,4] and reduction.[5,6] The structural deter-
mination of indium species, however, is rarely reported. Re-
cently, we used X-ray crystallographic analysis to determine
the structures of the allylindium(III) species generated in
organic solvents both by tin/indium transmetalation[7] and
by reduction methods.[8] X-ray analysis required stabiliza-
tion of the indium species by use of appropriate substituents
on the allylic carbon chain and ligands to the indium cen-
ter.[9,10] Many practical synthetic protocols use a reductive
method in aqueous media to synthesize allylindium com-
pounds. These protocols were more stereoselective and ef-
fective than those that used organic media.[11] Generally,
aqueous conditions are thought to generate allylindium(I)
compounds based on the NMR spectroscopic data reported
by Chan.[11g] The InI species was confirmed by NMR spec-
troscopy by comparison with the species prepared from an
organomercury compound. Recently, a structural analysis
of an allylindium compound based on ESI-MS data, con-
Results and Discussion
Before investigating the aqueous system, we examined
the structure of unsubstituted allylindium, which had never
been isolated before, in an organic solvent. Mixing of allyl
bromide (1) with indium(0) in THF gave two sets of allyl
signals in the NMR spectrum. Two compounds were
independently crystallized by mixing with different pyridine
ligands: allylindium dibromide 2·(Br2py)2 complexed
with 3,5-dibromopyridine and diallylindium bromide
3·(Me2Npy)2 complexed with DMAP (Scheme 1). The two
allylindium compounds were analyzed by using X-ray crys-
tallography.[13]
1
ductivity measurements, and H NMR spectrosopy was re-
ported.[12] However, unambiguous determination of the
structure remains to be performed, and X-ray analysis is
[a] Department of Applied Chemistry, Graduate School of
Engineering, Osaka Univeristy,
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
Fax: +81-6-6879-7387
E-mail: yasuda@chem.eng.osaka-u.ac.jp
baba@chem.eng.osaka-u.ac.jp
[b] Center for Atomic and Molecular Technologies, Graduate
School of Engineering, Osaka University,
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201000956.
Scheme 1. Isolation of two types of generated allylindium species
in THF and their stability in aqueous media.
View this journal online at
wileyonlinelibrary.com
Eur. J. Org. Chem. 2010, 5359–5363
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5359

M. Yasuda, M. Haga, Y. Nagaoka, A. Baba
SHORT COMMUNICATION
The ORTEP drawings of 2·(Br2py)2 and 3·(Me2Npy)2 are suspension of benzaldehyde in water with stirring at room
shown in Figure 1. In either case, the indium center has a temp. for 1 h gave the homoallyl alcohol in 77% yield
trigonal-bipyramidal coordination sphere. These are the [Equation (1)]. The reaction under the same conditions with
first reported examples of a crystallographic characteriza- 3·(Me2Npy)2 resulted in a lower yield (51%). In homogen-
tion of unsubstituted allylindium species as nucleophiles.[14] eous aqueous media, DMF/H2O (3:1), similar results were
observed with a 95% yield from 2·(Br2py)2 and 88% from
3·(Me2Npy)2. The lower yields from 3·(Me2Npy)2 were
caused by decomposition due to proton quenching of
3·(Me2Npy)2. In fact, premixing of the allylindium species
in DMF/H2O for 2 min followed by loading of benzalde-
hyde gave significantly different results for 2·(Br2py)2 and
3·(Me2Npy)2 [Equation (2)]. Monoallylindium 2·(Br2py)2
gave the product in 68% yield, whereas diallylindium
3·(Me2Npy)2 resulted in recovery of the starting benzalde-
hyde unreacted.
Figure 1. ORTEP drawing of (a) allyllindium dibromide 2·(Br2py)2
and (b) diallylindium bromide 3·(Me2Npy)2 (all hydrogen atoms
are omitted for clarity).
(1)
As no NMR spectra of allylindium generated in water
The stability of isolated 2·(Br2py)2 and 3·(Me2Npy)2 was were previously reported in the literature,[11g] we performed
examined in aqueous media. When monoallylindium com- an NMR study (Figure 2). Allyl bromide (1) was mixed
pound 2·(Br2py)2 was dissolved in DMF/D2O at room with indium(0) in D2O with stirring, and the resulting
1
temp. for 30 min, almost no decomposition was observed heterogeneous mixture was monitored by H NMR (Fig-
by NMR spectroscopy.[15] By contrast, after 10 min, ure 2a). The allyl signals (red) correspond with the allylin-
3·(Me2Npy)2 had decomposed, releasing propene. These re- dium(I) species assumed in the literature.[11g] However, we
sults suggest that 3·(Me2Npy)2 is much less stable in water confirmed the monoallylindium(III) species in the following
than 2·(Br2py)2 (Scheme 1). The addition of 2·(Br2py)2 to a experiment. Loading of [D7]DMF caused the hetero-
1
Figure 2. H NMR spectra under various conditions (red, 2; green, 3; blue, 1; black, propene). (a) Mixing of 1 with In0 in D2O at room
temp. for 30 min. (b) Addition of [D7]DMF to the mixture (a), giving a DMF/D2O (3:1) solution. (c) Mixing of 1 with In0 in DMF at
room temp. for 30 min and addition of D2O, giving a DMF/D2O (3:1) solution.
5360
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 5359–5363

Allylindium Species from Allyl Bromide and Indium(0)
(2)
geneous sample to become homogeneous, giving the spec-
trum in (Figure 2b) (DMF/D2O = 3:1) that indicates the
presence of monoallylindium dibromide (2) (red), diallylin-
dium bromide (3) (blue), allyl bromide (1) (green), and pro-
pene (black). These signals are consistent with Figure 2c,
which shows authentic samples of 2 and 3 in DMF/D2O
(see Supporting Information). These results show that the
reductive system that used 1 and In0 in water gave monoal-
lylindium(III) dibromide (2) and diallylindium bromide (3),
similar to the results obtained with an organic solvent. Al-
though a lower ratio of 3 was observed in the aqueous sys-
tem owing to its faster decomposition in water,[16] 3 sur-
vived in the system [Equation (3)]. Therefore, diallylindium
compound 3 should be considered in a Barbier-type reac-
tion course in the coexistence of carbonyl compounds.
Scheme 2. Reaction of an allylindium species with benzhydrol to
give allyl(µ-oxido)indium compound 7.
Figure 3. ORTEP drawing of (µ-alkoxido)allylindium compound 7
(all hydrogen atoms are omitted for clarity).
(3)
To further discuss the results of the NMR study shown
in Figure 2, we were interested in the process by which the
diallylindium species undergoes decomposition. A relatively
stable allylindium compound [cinnamylindium prepared
from cinnamyl bromide (4) and In0] was investigated in
alcohol instead of water as a model reaction of diallylin-
dium decomposition in water. The allylic species generated
from cinnamyl bromide with indium(0) in THF, i.e.,
monoallylindium compound 5 and diallylindium com-
pound 6,[8] were mixed with benzhydrol with stirring at
room temperature for 30 min and analyzed by using NMR
spectroscopy.[17] As expected, the monoallylindium com-
pound 5 remained unchanged, and the diallylindium com-
pound 6 was converted into the allylindium alkoxide 7
along with the generation of 3-phenylpropene (8)
(Scheme 2).
(4)
Conclusions
We identified the species generated in the system of allyl
bromide with In0 in water to be monoallylindium(III) com-
pound 2, diallylindium(III) compound 3, and the µ-oxido
form 9 (Scheme 3). The isolation of allyl(µ-hydroxido)-
indium with stabilizing bulky substituents is currently under
investigation.
X-ray analysis demonstrated that 7 was a (µ-alkoxido)-
indium complex (Figure 3). The indium atom has a tetrahe-
dral geometry with bridging oxygen atom, bromide and al-
lyl groups. The isolated allylindium compound 7 showed
a considerable reactivity toward benzaldehyde to give the
addition product in 47% yield [Equation (4)]. This structure
supports the generation of allyl(µ-hydroxido)indium species
9 in an aqueous 1/In0 system.
Scheme 3. Allylindium species generated in water.
Experimental Section
Allylindium Dibromide–3,5-Dibromopyridine Complex 2·(Br2py)2:
Allyl bromide (3.1 mmol, 0.376 g) was added to indium powder
Eur. J. Org. Chem. 2010, 5359–5363
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5361

M. Yasuda, M. Haga, Y. Nagaoka, A. Baba
SHORT COMMUNICATION
(3.1 mmol, 0.3514 g) in THF (10 mL) at room temperature. After
stirring for 30 min, 3,5-dibromopyridine (6.0 mmol, 1.420 g) was
added to the mixture, followed by stirring for 30 min. The solvent
was evaporated to give a white solid. This solid was washed with
hexane (5ϫ10 mL) to give a pure product as a white solid
(0.53 mmol, 0.42 g, 17%). A suitable crystal for X-ray analysis was
obtained after recrystallization from THF solution. 1H NMR
(400 MHz, CDCl3): δ = 8.80 (s, 4 H), 8.20 (s, 2 H), 6.02–5.90 (m,
1 H), 4.86 (d, J = 17.9 Hz, 1 H), 4.78 (d, J = 9.6 Hz, 1 H), 2.31 (d,
J = 8.7 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 148.1,
143.4, 136.4, 121.4, 111.5, 26.9 ppm.
[1]
a) J. Augé, N. L. Germain, J. Uziel, Synthesis 2007, 1739–1764;
b) S. Araki, T. Hirashita, in Comprehensive Organometallic
Chemistry III (Eds.: R. H. Crabtree, D. M. P. Mingos), Elsevier,
Oxford, U. K., 2007, vol. 9, pp. 650–724; c) U. K. Roy, S. Roy,
Chem. Rev. 2010, 110, 2472–2535.
a) C. J. Li, Chem. Rev. 1993, 93, 2023–2035; b) C. J. Li, Tetrahe-
dron 1996, 52, 5643–5668; c) T. P. Loh, G. L. Chua, Chem.
Commun. 2006, 2739–2749.
a) J. A. Marshall, K. W. Hinkle, J. Org. Chem. 1995, 60, 1920–
1921; b) M. Yasuda, T. Miyai, I. Shibata, A. Baba, Tetrahedron
Lett. 1995, 36, 9497–9500; c) J. A. Marshall, Chem. Rev. 1996,
96, 31–47; d) K. Inoue, Y. Shimizu, I. Shiata, A. Baba, Synlett
2001, 1659–1661; e) S. Donnelly, E. J. Thomas, E. A. Arnott,
Chem. Commun. 2003, 1460–1461.
Reductive transmetalation: Allyl halide/Sn/In system; a) X. R.
Li, T. P. Loh, Tetrahedron: Asymmetry 1996, 7, 1535–1538; Pd/
In system; b) S. Araki, T. Kamei, T. Hirashita, H. Yamaura,
M. Kawai, Org. Lett. 2000, 2, 847–849; c) U. Anwar, R. Grigg,
M. Rasparini, V. Savic, V. Sridharan, Chem. Commun. 2000,
645–646; d) U. Anwar, R. Grigg, V. Sridharan, Chem. Com-
mun. 2000, 933–934; e) Y. Takemoto, M. Anzai, R. Yanada, N.
Fujii, H. Ohno, T. Ibuka, Tetrahedron Lett. 2001, 42, 1725–
1728; f) M. Anzai, R. Yanada, N. Fujii, H. Ohno, T. Ibuka, Y.
Takemoto, Tetrahedron 2002, 58, 5231–5239; g) S. K. Kang,
S. W. Lee, J. Jung, Y. Lim, J. Org. Chem. 2002, 67, 4367–4379;
h) S. Araki, S. Kambe, K. Kameda, T. Kirashita, Synthesis
2003, 751–754; i) I. R. Cooper, R. Grigg, W. S. MacLachlan,
V. Sridharan, M. Thornton-Pett, Tetrahedron Lett. 2003, 44,
403–405; j) H. Miyabe, Y. Yamaoka, T. Naito, Y. Takemoto, J.
Org. Chem. 2004, 69, 1415–1418; k) R. Grigg, J. Blacker, C.
Kilner, S. McCaffrey, V. Savic, Tetrahedron 2008, 64, 8177–
8181; l) L. A. T. Cleghorn, R. Grigg, V. Savic, M. Simic, Tetra-
hedron 2008, 64, 8731–8737.
Organic solvent: a) S. Araki, H. Ito, Y. Butsugan, J. Org. Chem.
1988, 53, 1833–1835; b) S. Araki, H. Ito, N. Katsumura, Y.
Butsugan, J. Organomet. Chem. 1989, 369, 291–296; c) S.
Araki, T. Shimizu, P. S. Johar, S. Jin, Y. Butsugan, J. Org.
Chem. 1991, 56, 2538–2542; d) K. L. Tan, E. N. Jacobsen, An-
gew. Chem. Int. Ed. 2007, 46, 1315–1317; e) J. S. Yadav, B. V. S.
Reddy, P. Vishnumurthy, S. K. Biswas, Tetrahedron Lett. 2007,
48, 6641–6643; f) T. Hirashita, Y. Daikoku, H. Osaki, M. Og-
ura, S. Araki, Tetrahedron Lett. 2008, 49, 5411–5413; g) T. D.
Haddad, L. C. Hirayama, B. Singaram, J. Org. Chem. 2010, 75,
642–649.
[2]
[3]
Diallylindium
Bromide–4-(Dimethylamino)pyridine
Complex
3·(Me2Npy)2: Allyl bromide (3 mmol, 0.363 g) was added to indium
powder (3 mmol, 0.344 g) in THF (8 mL) at room temperature. Af-
ter stirring for 30 min, 4-(dimethylamino)pyridine (6 mmol,
0.733 g) was added to the mixture, followed by stirring for 16 h.
The solvent was evaporated to give a white solid, which was washed
with hexane (3ϫ10 mL) to give a product (a slightly excess amount
of DMAP remained) as a white solid (0.49 g, purity 81%,
0.76 mmol, 25%). A suitable crystal for X-ray analysis was ob-
tained after recrystallization from THF solution. 1H NMR
(400 MHz, CDCl3): δ = 8.11 (d, J = 6.3 Hz), 6.50 (d, J = 6.3 Hz),
6.10 (ddt, J = 17.9, 9.6, 8.7 Hz, 2 H), 4.73 (dd, J = 17.9, 0.9 Hz, 2
H), 4.54 (dd, J = 9.6, 0.9 Hz, 1 H), 3.02 (s, NMe2), 1.94 (d, J =
8.7 Hz, 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 154.5, 148.9,
139.5, 107.6, 106.5, 38.9, 24.0 ppm.
[4]
(µ-Alkoxido)cinnamylindium Compound 7: Cinnamyl bromide
(3.0 mmol, 0.59 g) was added to indium powder (3.0 mmol, 0.34 g)
in THF (10 mL) at room temperature. After stirring for 30 min,
benzhydrol (6.0 mmol, 1.10 g) was added to the mixture, followed
by stirring for 30 min. The solvent was evaporated to give a mix-
ture. It contained monocinnamylindium compound 5, allylbenzene
(8), and (µ-alkoxido)cinnamylindium compound 7 were observed
in the 1H NMR spectrum (CCl3). This mixture was washed with
hexane (5ϫ10 mL) to give a pure product as a white solid
(0.18 mmol, 0.18 g, 6%). A suitable crystal for X-ray analysis was
obtained after recrystallization from dichloromethane solution. 1H
NMR (400 MHz, CDCl3): δ = 7.51 (d, J = 6.8 Hz, 8 H), 7.37–7.16
(m, 22 H), 6.10 (s, 2 H), 5.86 (d, J = 15.5 Hz, 2 H), 5.70 (dt, J =
15.5, 8.7 Hz, 2 H), 1.40 (d, J = 8.7 Hz, 4 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 143.9, 137.6, 129.3, 128.6, 128.5, 128.4,
126.8, 126.5, 126.4, 125.7, 79.9, 24.7 ppm.
[5]
[6]
Radical reduction: a) N. Hayashi, H. Honda, M. Yasuda, I.
Shibata, A. Baba, Org. Lett. 2006, 8, 4553–4556; b) N. Hayashi,
H. Honda, I. Shibata, M. Yasuda, A. Baba, Synlett 2008,
1407–1411.
M. Yasuda, M. Haga, A. Baba, Organometallics 2009, 28,
1998–2000.
M. Yasuda, M. Haga, A. Baba, Eur. J. Org. Chem. 2009, 5513–
5517.
a) M. Yasuda, K. Kiyokawa, K. Osaki, A. Baba, Organometal-
lics 2009, 28, 132–139; b) Y. Nishimoto, R. Moritoh, M. Ya-
suda, A. Baba, Angew. Chem. Int. Ed. 2009, 65, 5462–5471; c)
B. Xu, M. S. Mashuta, G. B. Hammond, Angew. Chem. Int.
Ed. 2006, 45, 7265–7267.
CCDC-781656 [2·(Br2py)], -781655 [3·(Me2Npy)2] and 781657 (7)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_requ-
est/cif.
[7]
[8]
[9]
Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures and spectroscopic data for allylic
compounds.
[10]
[11]
Propargylindium system: a) B. Xu, M. S. Mashuta, G. B. Ham-
mond, Angew. Chem. Int. Ed. 2006, 45, 7265–7267; b) B. Xu,
G. B. Hammond, Chem. Eur. J. 2008, 14, 10029–10035.
Aqueous media: a) C. J. Li, T. H. Chan, Tetrahedron Lett. 1991,
32, 7017–7020; b) E. Kim, D. M. Gordon, W. Schmid, G. M.
Whitesides, J. Org. Chem. 1993, 58, 5500–5507; c) M. B. Issac,
T. H. Chan, Tetrahedron Lett. 1995, 36, 8957–8960; d) P.
Bernardelli, L. A. Paquette, J. Org. Chem. 1997, 62, 8284–8285;
e) L. A. Paquette, R. R. Rothhaar, M. Isaac, L. M. Rogers,
R. D. Rogers, J. Org. Chem. 1998, 63, 5463–5472; f) P. C.
Lobben, L. A. Paquette, J. Org. Chem. 1998, 63, 6990–6998; g)
T. H. Chan, Y. Yang, J. Am. Chem. Soc. 1999, 121, 3228–3229;
Acknowledgments
This work was supported by Grant-in-Aid for Scientific Research
on Priority Areas (No. 18065015, “Chemistry of Concerto Cataly-
sis” and No. 20036036, “Synergistic Effects for Creation of Func-
tional Molecules“) and by Grant-in-Aid for Scientific Research
(No. 21350074) from Ministry of Education, Culture, Sports, Sci-
ence and Technology (MEXT), Japan. We thank Dr. Nobuko
Kanehisa for the valuable advice regarding X-ray crystallography.
5362
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 5359–5363

Allylindium Species from Allyl Bromide and Indium(0)
h) T. P. Loh, K. T. Tan, Q.-Y. Hu, Tetrahedron Lett. 2001, 42,
8705–8708; i) K. T. Tan, S. S. Chng, H.-S. Cheng, T. P. Loh, J.
Am. Chem. Soc. 2003, 125, 2958–2963; j) J. M. Huang, K. C.
Xu, T. P. Loh, Synthesis 2003, 755–764; k) J. Li, Z. M. Sun, Y.
Zhang, Z. Wang, Chem. Lett. 2006, 35, 498–499; l) J. H. Min,
S. Y. Jung, B. Wu, T. J. Oh, M. S. Lah, S. Koo, Org. Lett. 2006,
8, 1459–1462; m) M. C. Law, T. W. Cheung, K. Y. Wong, T. H.
Chan, J. Org. Chem. 2007, 72, 923–929; n) S. A. Babu, M. Ya-
suda, A. Baba, J. Org. Chem. 2007, 72, 10264–10267; o) F. Co-
lombo, G. Cravotto, G. Palmisano, A. Penoni, M. Sisti, Eur. J.
[13] The addition of 3,5-dibromopyridine effectively crystallized al-
lylindium compound 2 from the mixture of 2 and 3. The ad-
dition of aminopyridine shifted the equilibrium toward 3. This
situation has been reported in our previous paper.[8]
[14] A dinuclear complex of an allylindium compound including
the PInPIn core was reported, but its nucleophilicity was not
discussed: R. D. Culp, A. H. Cowley, A. Decken, R. A. Jones,
Inorg. Chem. 1997, 36, 5165–5172.
[15] Very slow decomposition occurred, and only half the amount
of 2·(Br2py)2 was consumed after 1 d.
Org. Chem. 2008, 2801–2807; p) W. Kong, C. Fu, S. Ma, Org. [16] The reactivity of 2 and 3 as electrophiles is of the same order
Biomol. Chem. 2008, 6, 4587–4592; q) I. A. Olson, A. M.
Sessler, J. L. Connell, E. Giordano, Y. Y. B. Sosa, S. W. Zava-
leta, W. J. Bowyer, J. Phys. Chem. A 2009, 113, 2801–2808.
[12] An Allylindium compound generated by a reductive system has
been analyzed quite recently by ESI MS, VT 1H NMR, and
electrical conductivity measurements: K. Koszinowski, J. Am.
Chem. Soc. 2010, 132, 6032–6040.
(diallylindium bromide Ͼ allylindium dibromide) as discussed
in our previous report.[8]
[17] The reaction of the allyl bromide/water system was too fast to
be observed. Benzhydrol was used instead of water because
water caused a too fast decomposition.
Received: July 7, 2010
Published Online: August 16, 2010
Eur. J. Org. Chem. 2010, 5359–5363
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5363