Metal-catalyzed ring-opening of alkylidenecyclopropanes: New access to building blocks with an acyclic quaternary stereogenic center

Article abstract of DOI:10.1002/chem.200902656

A study was conducted to investigate metal-catalyzed ring-opening of alkylidenecyclopropanes (ACP). The investigations focused on developing this concept and to delineate the reactivity of exo-alkylidene moiety towards the metal-catalyzed hydroboration reaction. Methylene- and ACPs were subjected to pinacol borane (HBPin) in the presence of the Wilkinson catalyst at room temperature. HBPin was selected to conduct the investigations, as the reductive elimination to form the carbon-boron bond was slower than other boronate esters. The formation of the single boronate ester was rationalized through the oxidative addition of the catalyst into the H-B bond of HBPin that gave the corresponding metal hydride species. The metal hydride species added to the double bond of methylenecyclopropane (MCP) through a hydrometalation reaction to form the alkyl metal.

Full text of DOI:10.1002/chem.200902656

DOI: 10.1002/chem.200902656
Metal-Catalyzed Ring-Opening of Alkylidenecyclopropanes: New Access to
Building Blocks with an Acyclic Quaternary Stereogenic Center
Samah Simaan,[a] Alexander F. G. Goldberg,[a] Stephane Rosset,[b] and Ilan Marek*[a]
Dedicated to Professor Alexandre Alexakis on the occasion of his 60th birthday
A very stimulating and dy-
namic area in organic synthesis
nowadays is the asymmetric
construction of molecules with
quaternary carbon stereocen-
ters, that is, carbon centers
with four different non-hydro-
gen substituents,[1] and the top-
of-the-art still remains the
asymmetric construction of
such stereocenters in acyclic
systems.[2] Over the last few
years, we[3] and others[4] have
Scheme 1. General features of the reaction of ACP.
been involved in the develop-
ment of such synthetic strat-
egies. We recently questioned whether it might be possible
to develop a simple metal-catalyzed ring-opening reaction
of substituted alkylidenecyclopropanes (ACPs) into linear
products with complete preservation of the stereochemical
integrity of pre-existing stereogenic centers.
The reaction of ACPs in the presence of transition-metal
catalysts M is known and has been summarized into the fol-
lowing patterns (Scheme 1): insertion of M into the distal
bond C-3/C-4 (path a); insertion of M into the proximal
bond C-2/C-3 (path b); and addition of organometallic de-
rivative RMLn across the exomethylene double bond lead-
ing to two possible products (paths c and d). In the former
case (path c), the addition product may be eventually fol-
lowed by a further ring opening of the cyclopropyl unit
(path c).[5] Therefore, the attractive but often troublesome
feature of ACPs is their multiform reactivities that may lead
to the formation of a variety of products. Among all the re-
ported transformations,[5] the metal-catalyzed hydroboration
of ACPs has surprisingly never received attention.[6] In this
context, a particularly interesting reaction would be the re-
gioselective anti-Markovnikov addition of pinacol borane[7]
to the exo-alkylidene moiety of 1, followed by a regioselec-
tive ring-opening reaction of the intermediate 2. If the ring
cleavage occurs through the C-2/C-3 bond, a primary acyclic
organometallic species 3 would be obtained potentially with
full preservation of the stereochemical information
(Scheme 1). On the other hand, if the ring opening occurs
through the cleavage of the C-2/C-4 bond, the less stable tri-
substituted organometallic species 4 would result. Based on
the stability of primary versus tertiary organometallic spe-
cies (3 versus 4, respectively), we anticipated that only the
regioisomer 3 would be obtained in such a process. The pur-
[a] Dr. S. Simaan, A. F. G. Goldberg, Prof. Dr. I. Marek
Contribution from the Mallat Family Laboratory of Organic Chemis-
try
Schulich Faculty of Chemistry and
the Lise Meitner-Minerva Center for Computational Quantum
Chemistry
Technion-Israel Institute of Technology
Technion City, Haifa 32000 (Israel)
Fax : (+972)48293709
E-mail: chilanm@tx.technion.ac.il
[b] S. Rosset
Departement de Chimie Organique, Universite de Geneve
30 Quai Ernest Ansermet, 1211 Geneve 4 (Switzerland)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200901488.
774
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Chem. Eur. J. 2010, 16, 774 – 778

COMMUNICATION
pose of our initial investigation was to develop this concept
and to delineate the reactivity of 1 towards the metal-cata-
lyzed hydroboration reaction. As a test reaction, we subject-
ed methylene- and alkylidenecyclopropanes to pinacol
borane (HBPin, 1.1 equiv) in the presence of the Wilkinson
catalyst (0.5 mol%) in CH2Cl2 at room temperature as
shown in Table 1.[8] We chose to use pinacolborane (HBPin)
which would have resulted from the most substituted
carbon–carbon bond ring-cleavage (through reductive elimi-
nation of 4). Only the non-substituted proximal bond under-
goes the ring cleavage to give the corresponding acyclic
alkyl–rhodium intermediate 3, which leads to 5 after reduc-
tive elimination (Scheme 2).[12] Therefore, the Rh-catalyzed
hydroboration of methylenecyclopropane derivatives is a re-
markable combination of several consecutive chemical steps
that proceeds to cleanly lead to the unique formation of 5.
Whatever the methylenecyclopropane derivatives used
(Table 1, entries 1 and 2) a single isomer 5 was always ob-
tained, even when a potentially tertiary benzylic organome-
tallic species could be formed (Table 1, entry 2). When al-
Table 1. Rh-catalyzed hydroboration of MCPs and ACPs.
ACHUTNGRENkNUG ylACHUTNGTRENiNGUN denecyclopropane derivatives were engaged in the same
Entry
R1
R2
R3
Yield 5 [%][a]
Yield 8 [%][b]
reaction (R3 =alkyl or aryl), the chemical outcome is similar
and excellent isolated yields of the single ring-opened prod-
ucts 5 were obtained (no traces of 6, Table 1, entries 3–8).
Following oxidation with hydrogen peroxide and reduction
of the double bond,[13] the resulting saturated alcohols 8c–h
were isolated by column chromatography in excellent yields.
Following our initial success with pinacol borane, we further
decided to investigate the rhodium- and palladium-catalyzed
addition of silanes[14] and stannanes,[15] respectively, of alkyli-
denecyclopropane derivatives and confirm that a selective
ring-opening should also be observed as described in
Table 2.[16] We were pleased to see that the RhI-catalyzed
hydrosilylation of alkylidenecyclopropanes (method A)[14]
also proceeds with selective cleavage of the less substituted
carbon–carbon bond of the cyclopropane ring according to
our mechanistic hypothesis described in Scheme 2. Only ho-
moallylsilanes 9 were produced in good to excellent isolated
yields (see Table 2, method A, entries 1–7). Moreover, the
reaction is stereoselective as the E/Z ratios of homoallylsil-
1 (1a)
2 (1b)
3 (1c)
4 (1d)
5 (1e)
6 (1 f)
7 (1g)
8 (1h)
Bu
Me
Bu
Me
Me
Me
Me
Me
Hex
Ph
Et
Et
Ph
Et
Bu
Hex
H
90 (5a)
89 (5b)
81 (5c)
83 (5d)
83 (5e)
80 (5 f)
84 (5g)
90 (5h)
81 (8a)[c]
81 (8b)[c]
87 (8c)
83 (8d)
81 (8e)
87 (8 f)
81 (8g)
85 (8h)
H
Me[d]
(CH2)2Ph[d]
ACHTUNGTRENNUNG
A
Ph[d]
Ph[d]
Ph[d]
[a] Boronate esters 5 are unstable by column chromatography and yields
were determined by 1H NMR spectroscopy. [b] Isolated yields after pu-
rification by column chromatography. [c] Yields determined based on the
non-reduced double bond. [d] Mixture of geometrical isomers was ob-
tained E/Z 2:1. [e] Mixture of geometrical isomers was obtained E/Z 4:1.
because the reductive elimination to form the carbon–boron
bond is slower than other boronate esters (i.e., catechol
borane), a feature attributed to pinacolboraneꢁs lower Lewis
acidity.[9] Our choice of a less reactive substrate would ideal-
ly stack the deck in favor of ring-opening as opposed to
direct addition. Remarkably, the reaction proceeds smoothly
and when methylenecyclopro-
pane (MCP) 1a was subjected
to our experimental conditions,
a single boronate ester 5a was
observed (Table 1, entry 1).
The formation of the isomer
5a could be rationalized
through the following mecha-
nism (Scheme 2).[10] Oxidative
addition of the catalyst into
À
the H B bond of HBPin gives
the corresponding metal hy-
dride species that add to the
double bond of MCP 1 through
a hydrometalation reaction to
form the alkyl metal 2.[11]
The ring-opening process is
indeed faster than reductive
elimination, since no cyclopro-
pylborane 7 was detected in
the crude reaction mixture.
Moreover, the ring opening is
selective, since we could not
detect the formation of 6,
Scheme 2. Mechanistic hypothesis.
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775

I.Marek et al.
Table 2. Rh-catalyzed hydrosilylation and Pd-catalyzed hydrostannations
of ACPs.
93:7) was performed, (E)- and (Z)-homoallylsilanes 9a were
formed with the same E/Z ratio, respectively ((E,R)-9a/
TERNN(UG Z,S)-9a=93:7). Both isomers were purified and then sub-
ACHTUNG-
jected to hydrogenation of the double bond followed by
Tamao–Fleming oxidation.[19] The corresponding saturated
alcohols 8 f possessing the quaternary center were obtained
in quantitative yields with enantiomeric ratios similar to the
starting materials (Scheme 3).[20]
To confirm that such reaction proceeds also with an ali-
phatic group on the double bond of the alkylidenecyclopro-
pane, 1c was easily accessed as a single E isomer in an enan-
Entry
R1 R2 R3
Me Et Ph
R4 Method E/Z ratio[a] Yield [%][b]
1
2
N
H
H
H
H
H
H
H
H
Me
Ph
H
H
H
H
A
A
A
A
A
A
A
B
B
B
B
B
B
B
1
93:7
87:13
95:5
97:3
100:0
100:0
100:0
–
90 (9a)
93 (9b)
89 (9c)
91 (9d)
85 (9e)
87 (9 f)
94 (9g)
90 (10a)
80 (10b)
93 (10c)
94 (10d)
90 (10e)
91 (10 f)
88 (10g)
3
A
Me Et p-MeAr
Me Ph p-MeAr
4
ACHTUNGTRENNUNG
5
ACHTUNGTRENNUNG
6
ACHTUNGTRENNUNG
tiomerically pure form from our reported procedure.[18]
When submitted to the Rh-catalyzed hydroboration reac-
tion, a selective ring-opening reaction occurs leading to the
corresponding primary alkyl borane 5c in 81% yield as a
mixture of two E/Z isomers. After oxidation, the enantio-
meric excess of the homoallylic alcohol 11 possessing the
quaternary stereocenter was determined to be higher than
96%, demonstrating again that the stereochemistry of the
stereogenic center is retained in the reaction sequence. This
simple concept could be used to prepare 8c, a known pre-
cursor of 4-ethyl-4-methyloctane,[21] the simplest chiral satu-
7
A
8
N
H
9
A
–
–
10
11
12
13
14
N
100:0
72:28
87:13
76:24
Me Bu Ar[c]
Me Et Me
[a] E/Z ratio determined on the crude H NMR spectrum and is identical
to the starting E/Z ratio of ACPs 1. [b] Isolated yields after purification
by column chromatography. [c] Ar=2,4,6-Me3Ar.
ACHTUNGTRENNUNGanes 9 correspond to the initial
E/Z ratios of the alkylidenecy-
clopropanes 1. No traces of hy-
drosilylation of the exo-meth-
ylene double bond was detect-
ed suggesting that the ring-
opening is again faster that the
reductive elimination.[17] When
MCPs and ACPs 1 were treat-
ed with
a
slight excess
(1.3 equiv) of Bu3SnH in THF
in the presence of a catalytic
amount
of
[PdACTHUNGTRENNU(G PPh3)4]
(3 mol%, method B),[15] the
corresponding homoallylstan-
nanes 10 were also obtained in
excellent yields as single ring-
opened products (Table 2, en-
tries 8–14). As the ring cleav-
age preferentially occurs to
lead to the primary alkyl metal
species 3 in all examined cases
(Scheme 2), the integrity of
Scheme 3. Formation of enantiomerically enriched quaternary stereocenter through selective ring opening.
the quaternary stereogenic center should remain unaffected
in the process. To confirm our assumption, several enantio-
merically pure alkylidenecyclopropane derivatives were pre-
pared by the method that we recently described.[18]
Although the E isomer is largely predominant, the two
isomers have opposite absolute configurations. For instance,
1 f was prepared with a E/Z ratio of 93:7, whereby (E)-1 f
has an absolute S configuration and that of (Z)-1 f is R—
each geometric isomer was formed with an enantiomeric
ratio >99:1. Accordingly, when the Rh-catalyzed hydrosily-
rated hydrocarbon with
(Scheme 3).
a
quaternary stereocenter
In conclusion, a selective metal-catalyzed ring opening of
alkylidenecyclopropane derivatives leads to various func-
tionalized acyclic derivatives possessing the challenging qua-
ternary sterocenters. The key feature of this transformation
is that the ring opening is faster than the reductive elimina-
tion and is highly regioselective; a single opened product
was always observed and the stereointegrity of the quaterna-
ry stereogenic center remains unaffected in the process.
lation reaction of enantiomerically pure 1 f ((E,S)/ACTHUNTGRNEUNG(Z,R)=
776
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Homogeneous Catalysis
COMMUNICATION
14477; k) C. A. Falciola, A. Alexakis, Chem. Eur. J. 2008, 14, 10615;
l) C. E. Stivala, A. Zakarian, J. Am. Chem. Soc. 2008, 130, 3774;
m) S. Jautze, R. Peters, Angew. Chem. 2008, 120, 9424; Angew.
Chem. Int. Ed. 2008, 47, 9284; n) J. L. Stymiest, V. Bagutski, R. M.
French, V. K. Aggarwal, Nature 2008, 456, 778.
Experimental Section
General procedure for the preparation of homoallyl boranes: [Rh-
(PPh3)3Cl] (5 mg, 0.5 mol%) was placed in a dry three-necked flask. The
ACHTUNGTRENNUNG
flask was attached to a vacuum pump for 5 min and refilled with argon
three times. ACP (1 mmol) was dissolved in CH2Cl2 (3 mL; distilled over
CaH2) and added to the flask. The solution was stirred for 15 min and
then pinacolborane (PinBH; 1.5 equiv) was added slowly. The reaction
was finished after 12 h at room temperature. The solvent was evaporated
and the crude product was purified by short column chromatography.
Eluent: hexane/ethyl acetate 100:1.
[5] For reviews, see a) I. Marek, S. Simaan, A. Masarwa, Angew. Chem.
2007, 119, 7508; Angew. Chem. Int. Ed. 2007, 46, 7364; b) M. Rubin,
M. Rubina, V. Gevorgyan, Chem. Rev. 2007, 107, 3117; c) I. Naka-
mura, Y. Yamamoto, Adv. Synth. Catal. 2002, 344, 111; d) A. Brandi,
A. Goti, Chem. Rev. 1998, 98, 589; e) A. de Meijere, S. I. Kozhush-
kov, A. F. Khlebnikov, Top. Curr. Chem. 2000, 207, 89; f) L.-X. Shao,
M. Shi, Curr. Org. Chem. 2007, 11, 1135.
General procedure for the preparation of homoallyl silanes: The ACP
[6] For a single report on non-catalyzed hydroboration of ACP deriva-
tives, see: a) K. Utimoto, M. Tamura, M. Tanouti, K. Sisido, Tetrahe-
dron 1972, 28, 5697. Pd- and Pt-catalyzed silaboration of MCP deriv-
atives, see: b) M. Suginome, T. Matsuda, Y. Ito, J. Am. Chem. Soc.
2000, 122, 11015; c) T. Ohmura, H. Taniguchi, Y. Kondo, M. Sugi-
nome, J. Am. Chem. Soc. 2007, 129, 3518; d) T. Pohlmann, A. de
Meijere, Org. Lett. 2000, 2, 3877; e) T. Ohmura, H. Taniguchi, M.
Suginome, Org. Lett. 2009, 11, 2880.
derivative (1 mmol) was placed in a dry three-necked flask containing a
solution of [RhACHTUNGTRENNUNG(PPh3)3Cl] (5 mg, 0.5 mol%) in dry toluene (5 mL). Phe-
nyldimethylsilane (0.23 mL, 1.5 mmol) was added slowly to the solution
over a period of 15 min and the mixture was heated at 808C over night.
The solvent was evaporated and the crude product was purified by
column chromatography. Eluent: hexane.
General procedure for the preparation of homoallyl stannanes: The ACP
derivative (1 mmol) was placed in a dry three-necked flask containing
[7] For recent reports on metal-catalyzed addition of pinacol borane on
different substrates, see: a) D. Imao, B. W. Glasspoole, V. S. Laberge,
C. M. Crudden, J. Am. Chem. Soc. 2009, 131, 5024; b) C. M. Crud-
den, Y. B. Hleba, A. C. Chen, J. Am. Chem. Soc. 2004, 126, 9200;
c) M. Rubina, M. Rubin, V. Gevorgyan, J. Am. Chem. Soc. 2003,
125, 7198; For addition of different metal hydrides on cyclopro-
penes, see d) A. Trofimov, M. Rubina, M. Rubin, V. Gevorgyan, J.
Org. Chem. 2007, 72, 8910.
dry THF (10 mL). The catalyst [PdACHTNUGRTNEUNG(PPh3)4] (34 mg, 3 mol%) was added
to the solution and the mixture was stirred for 15 min. Then tributyltin
hydride (0.44 mL) was added through a syringe pump over a period of
one hour. The reaction was monitored by TLC and finished after 30 min.
The solute was evaporated and the crude product was purified by column
chromatography. Eluent: hexane.
[8] D. R. Edwards, Y. B. Hleba, C. J. Lata, L. A. Calhoun, C. M. Crud-
den, Angew. Chem. 2007, 119, 7945; Angew. Chem. Int. Ed. 2007, 46,
7799.
[9] C. M. Crudden, D. R. Edwards, Eur. J. Org. Chem. 2003, 4695.
[10] D. A. Evans, G. C. Fu, J. Org. Chem. 1990, 55, 2280.
Acknowledgements
This research was supported by a grant from the Israel Science Founda-
tion administrated by the Israel Academy of Sciences and Humanities
(70/08). I.M. is holder of the Sir Michael and Lady Sobell Academic
Chair.
[11] For recent metal-catalyzed reactions of MCPs and ACPs, see a) S. I.
Kozhushkov, D. S. Yufit, L. Ackermann, Org. Lett. 2008, 10, 3409;
b) P. A. Evans, P. A. Inglesby, J. Am. Chem. Soc. 2008, 130, 12838;
c) R. Garcꢂa-FandiÇo, M. Gulꢂas, L. Castedo, J. R. Granja, J. L. Mas-
careÇas, D. J. Cꢃrdenas, Chem. Eur. J. 2008, 14, 272; d) M. Gulꢂas, J.
Durꢃn, L. Castedo, J. L. MascareÇas, J. Am. Chem. Soc. 2007, 129,
11026; e) E. Smolensky, M. Kapon, M. S. Eisen, Organometallics
2005, 24, 5495; f) A. I. Siriwardana, I. Nakamura, Y. Yamamoto, J.
Org. Chem. 2004, 69, 3202; g) B. H. Oh, I. Nakamura, Y. Yamamoto,
J. Org. Chem. 2004, 69, 2856; h) M. Shi, Y. Chen, B. Xu, Org. Lett.
2003, 5, 1225; i) M. Shi, B. Xu, Tetrahedron Lett. 2003, 44, 3839; j) S.
Ma, J. Zhang, Angew. Chem. Int. Ed. 2003, 42, 184; Angew. Chem.
2003, 115, 193; k) D. H. Camacho, I. Nakamura, S. Saito, Y. Yama-
moto, J. Org. Chem. 2001, 66, 270; l) I. Nakamura, S. Saito, Y. Ya-
mamoto, J. Am. Chem. Soc. 2000, 122, 2661; m) D. H. Camacho, I.
Nakamura, S. Saito, Y. Yamamoto, Angew. Chem. 1999, 111, 3576;
Angew. Chem. Int. Ed. 1999, 38, 3365; Angew. Chem. 1999, 111,
3576; n) M. Lautens, Y. Ren, J. Am. Chem. Soc. 1996, 118, 10668;
o) M. Shi, B.-Y. Wang, J.-W. Huang, J. Org. Chem. 2005, 70, 5606;
p) M. Shi, G.-Q. Tian, J. Li, Tetrahedron 2009, 65, 3404; q) X.-Y.
Tang, M. Shi, Tetrahedron 2009, 65, 8863.
Keywords: alkylidenecyclopropanes
·
homogeneous
catalysis · hydroboration · hydrosilylation · hydrostannation ·
palladium · rhodium
[1] E. J. Corey, A. Guzman-Perez, Angew. Chem. 1998, 110, 2092;
Angew. Chem. Int. Ed. 1998, 37, 388.
[2] a) B. M. Trost, C. Jiang, Synthesis 2006, 369; b) J. Christoffers, A.
Baro, Adv. Synth. Catal. 2005, 347, 1473.
[3] a) J. P. Das, H. Chechik, I. Marek, Nature Chem. 2009, 1, 128; b) I.
Marek, Chem. Eur. J. 2008, 14, 7460; c) I. Marek, G. Sklute, Chem.
Commun. 2007, 1683; d) G. Kolodney, G. Sklute, S. Perrone, P. Kno-
chel, I. Marek, Angew. Chem. 2007, 119, 9451; Angew. Chem. Int.
Ed. 2007, 46, 9291; e) G. Sklute, I. Marek, J. Am. Chem. Soc. 2006,
128, 4642; f) G. Sklute, D. Amsallem, A. Shibli, J. P. Varghese, I.
Marek, J. Am. Chem. Soc. 2003, 125, 11776.
[4] For representative recent papers, see: a) A. H. Hoveyda, P. J. Lom-
bardi, R. V. OꢁBrien, A. R. Zhugralin, J. Am. Chem. Soc. 2009, 131,
8378; b) E. A. Tiong, J. L. Gleason, Org. Lett. 2009, 11, 1725; c) R.
Yazaki, N. Kumagai, M. Shibasaki, J. Am. Chem. Soc. 2009, 131,
3195; d) L. Yin, M. Kanai, M. Shibasaki, J. Am. Chem. Soc. 2009,
131, 9610; e) S. E. Denmark, T. W. Wilson, M. T. Burk, J. R. Heem-
stra, J. Am. Chem. Soc. 2007, 129, 14864; f) D. A. Kummer, W. J.
Chain, M. R. Morales, O. Quiroga, A. G. Myers, J. Am. Chem. Soc.
2008, 130, 13231; g) A. Wilsily, E. Fillion, Org. Lett. 2008, 10, 2801;
h) S. E. Reisman, A. G. Doyle, E. N. Jacobsen, J. Am. Chem. Soc.
2008, 130, 7198; i) M. Branca, D. Gori, R. Guillot, V. Alezra, C.
Kouklovsky, J. Am. Chem. Soc. 2008, 130, 5864; j) R. Yazaki, T. Ni-
tabura, N. Kumagai, M. Shibasaki, J. Am. Chem. Soc. 2008, 130,
[12] C. Aꢄssa, A. Fꢅrstner, J. Am. Chem. Soc. 2007, 129, 14836.
[13] As two E and Z isomers were obtained, the reduction of the double
bond was performed to have better NMR spectra.
[14] A. G. Bessmertnykh, K. A. Blinov, Y. K. Grishin, N. A. Donskaya,
E. V. Tveritinova, N. M. Yur’eva, I. P. Beletskaya, J. Org. Chem.
1997, 62, 6069.
[15] a) M. Lautens, C. Meyer, A. Lorenz, J. Am. Chem. Soc. 1996, 118,
10676; b) M. Lautens, Y. Ren, P. Delanghe, P. Chiu, S. Ma, J. Coluc-
ci, Can. J. Chem. 1995, 73, 1251.
[16] For hydrido-rhodium(I) and IrI complex in the ring-opening of
MCPS, see a) Y. Nishihara, C. Yoda, M. Itazaki, K. Osakada, Bull.
Chem. Soc. Jpn. 2005, 78, 1469; b) M. Itazaki, Y. Nishihara, K. Osa-
kada, J. Org. Chem. 2002, 67, 6889 and references therein.
Chem. Eur. J. 2010, 16, 774 – 778
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
777

I.Marek et al.
[17] For Pt-catalyzed hydrosilylation reaction without ring-opening of
MCPs, see: Y. Nishihara, M. Itazaki, K. Osakada, Tetrahedron Lett.
2002, 43, 2059.
[18] a) S. Simaan, A. Masarwa, P. Bertus, I. Marek, Angew. Chem. 2006,
118, 4067; Angew. Chem. Int. Ed. 2006, 45, 3963; b) A. Masarwa, A.
Stanger, I. Marek, Angew. Chem. 2007, 119, 8185; Angew. Chem.
Int. Ed. 2007, 46, 8039; c) S. Simaan, I. Marek, Org. Lett. 2007, 9,
2569; d) S. Simaan, I. Marek, Chem. Commun. 2009, 292; e) S.
Simaan, A. Masarwa, E. Zohar, A. Stanger, P. Bertus, I. Marek,
Chem. Eur. J. 2009, 15, 8449.
[20] (R)-8 f, resulting from the ring-opening of (E,S)-1 f, has an enantio-
meric excess slightly lower since we couldn’t completely remove the
Z isomer of 1 f [(Z,R)-1 f] that has the opposite absolute configura-
tion.
[21] a) K. Mislow, P. Bickart, Isr. J. Chem. 1976, 15, 1; b) T. Fujita, K.
Obata, S. Kuwahara, N. Miura, A. Nakahashi, K. Monde, J. Decatur,
N. Harada, Tetrahedron Lett. 2007, 48, 4219; c) W. ten Hoeve, H.
Wynberg, J. Org. Chem. 1980, 45, 2754.
[19] I. Fleming, R. Henning, D. C. Parker, H. E. Plaut, P. E. J. Sanderson,
J. Chem. Soc. Perkin Trans. 1 1995, 317.
Received: September 27, 2009
Published online: November 30, 2009
778
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