Kinetic resolution of planar-chiral 1,2-disubstituted ferrocenes by molybdenum-catalyzed asymmetric intraannular ring-closing metathesis

Article abstract of DOI:10.1002/chem.201300116

Planar chirality: Ring-closing metathesis of 1,2-diallylmetallocenes afforded the corresponding 4,7-dihydroindenyl species in high yields. The metallocenes are planar chiral with two different allylic substituents, and kinetic resolution of the racemic 1,

Full text of DOI:10.1002/chem.201300116

COMMUNICATION
DOI: 10.1002/chem.201300116
Kinetic Resolution of Planar-Chiral 1,2-Disubstituted Ferrocenes by
Molybdenum-Catalyzed Asymmetric Intraannular Ring-Closing Metathesis
Masamichi Ogasawara,*[a] Sachie Arae,[a] Susumu Watanabe,[a]
Kiyohiko Nakajima,[b] and Tamotsu Takahashi*[a]
Metal-catalyzed structural modification of transition-
metal complexes within their coordination spheres has been
an interesting subject in inorganic/organometallic synthe-
sis.[1] This strategy is potentially extendable to stereoselec-
tive processes, and the development of the enantioselective
counterparts would be particularly attractive. Among metal-
containing chiral scaffolds, planar-chiral ferrocenes[2] are by
far the most widely utilized in asymmetric synthesis and
have found widespread application as chiral ligands[3] or cat-
alysts.[4] In spite of their usefulness, enantioselective prepa-
rations of such ferrocene derivatives are rather limited; the
majority of optically active planar-chiral ferrocenes were ob-
tained either by diastereoselective metalation by utilizing
chiral ortho-directing groups[5] or by classical resolution of
preformed racemates. Enantioselective lithiation of prochi-
ral ferrocenes by a stoichiometric chiral base has also shown
fair success.[6] On the other hand, examples of catalytic
asymmetric syntheses of planar-chiral ferrocenes are ex-
tremely rare,[7,8] and further breakthroughs have been clear-
ly awaited.
closing metathesis (ARCM) giving the optically active met-
allocenes in up to 99% ee (ee=enantiomeric excess). It
should be noted that the present protocol allows direct
access to scalemic planar-chiral indenyl motifs.
Recently, we and others independently reported the prep-
aration of various bridged metallocenes by interannular
ring-closing metathesis (RCM) of 1,1’-diallylmetallocenes
[Eq. (1)].[9] The reaction was extended to the enantioselec-
tive variants in our group,[8] and various planar-chiral bridg-
ed metallocenes were prepared with excellent enantioselec-
tivity. Here, we would like to report an alternative protocol
for the catalytic asymmetric synthesis of planar-chiral metal-
locenes: the “intraannular” RCM of 1,2-diallylmetallocenes
[Eq. (2)]. Kinetic resolution of racemic 1b–1i, which are
planar chiral with the two different allylic substituents, is fa-
cilitated by the molybdenum-catalyzed asymmetric ring-
A series of 1,2-diallylmetallocene substrates (1a–1i) were
prepared by the method outlined in Scheme 1. The two
modes of lithiation on bromoferrocenes, that is, ortho lithia-
tion by lithium tetramethylpiperidide (LTMP)[10] and lithi-
um–bromine exchange by butyllithium, were utilized for the
regioselective and stepwise introduction of the proper sub-
stituents in 1.
[a] Prof. Dr. M. Ogasawara, S. Arae, Dr. S. Watanabe,
Prof. Dr. T. Takahashi
Catalysis Research Center and Graduate School of Life Science
Hokkaido University, Kita-ku, Sapporo 001-0021 (Japan)
Fax : (+81)11-706-9150
E-mail: ogasawar@cat.hokudai.ac.jp
tamotsu@cat.hokudai.ac.jp
[b] Prof. Dr. K. Nakajima
Department of Chemistry
Aichi University of Education
Igaya, Kariya 448-8542 (Japan)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201300116.
Scheme 1. Preparation of 1,2-diallylmetallocene substrates 1a–1i. Tol=
para-methylphenyl, DMPU=N,N’-dimethylpropyleneurea.
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At the outset, the feasibility of the intraannular RCM
process was examined. The reaction of 1,2-diallylferrocene
(1a) proceeded smoothly in the presence of the Grubbs II
After the optimization studies, Mo/(R)-L1 or Mo/(R)-L3
was applied to the other substrates. Substrate rac-1c, which
has a ruthenocene core in place of the ferrocene in 1b, was
also resolved as described above, however the enantioselec-
tivity was somewhat lower (krel =11; Table 1, entry 4). The
position of R3 in 1 is crucial for a high enantioselectivity of
the ARCM reaction. Substrate 1d, which possesses a p-tolyl
group adjacent to the methallyl substituent, was resolved ef-
ficiently by using Mo/(R)-L1, and 1d with 91% ee was re-
covered in 30% yield (Table 1, entry 5). On the other hand,
the reaction of 1e, which has a p-tolyl substituent next to
the allyl group, under the identical conditions gave recov-
ered 1e with 4% ee and cyclized 2e with less than 1% ee
(Table 1, entry 6). Based on our previous studies,[9] it is
postulated that the initial metathesis between the Mo*–al-
catalyst[11] A (1 mol%) or the Schrock Mo catalyst[12]
B
(1 mol%) to give (h5-4,7-dihydroindenyl)FeCp (2a, Cp=cy-
clopentadienyl) in >99% yield [Eq. (2)].
Substrates 1b–1i are planar chiral because the two adja-
cent allylic substituents are non-identical, and their race-
mates were subjected to the kinetic resolution studies by
using a chiral Mo–alkylidene catalyst (Table 1).[13] Screening
of the chiral catalysts was examined on racemic 1-allyl-2-
methallylferrocene (1b) as a prototypical substrate. The re-
actions were carried out in benzene at 238C in the presence
of an appropriate chiral Mo catalyst (5 mol%), that was
generated in situ from the Mo precursor (pyrrolyl)2Mo(=
CHCMe2Ph)(=N-C6H3-2,6-iPr2) and an axially chiral biphe-
nol derivative.[14] Under these conditions, the Mo catalyst
generated with (R)-L1[15a] gave the RCM product 2b with
53% ee in 66% yield, and the unreacted 1b with 98% ee
was recovered in 24% yield (Table 1, entry 1). The krel value
([reaction rate of the fast-reacting enantiomer]/[reaction
rate of the slow-reacting enantiomer]; selectivity factor) for
this reaction is estimated to be 14.[16] The Mo/(R)-L2 spe-
cies[15b] was highly active; the reaction of rac-1b by using
this catalyst showed complete conversion to rac-2b within
4 h. Thus, the kinetic resolution study by using Mo/(R)-L2
was conducted at 08C in toluene for 1 h, but the enantiose-
lectivity was minimal (krel =2.0; Table 1, entry 2). The Mo
catalyst coordinated with (R)-L3[15c] showed excellent enan-
tioselectivity giving 1b with 96% ee in 37% yield and 2b
with 72% ee in 60% yield, respectively. The krel value for
the reaction is as high as 22 (Table 1, entry 3).
A
ACTHUNGERTNNUNGiAHCTUNGTRNENdUNG ene precatalyst and a substrate takes place at the un-
AHCTUNGTRENNUNG
Mo*–alkylidene, the steric factors between the two substitu-
ents adjacent to the [(R)-Mo*]-binding tether are fairly dif-
À
À
ferent (C H vs. C methallyl). As a result, [(R)-Mo*]/(R)-1d
forms preferentially over the other diastereomeric inter-
mediate (Scheme 2, left). On the other hand, the two sub-
stituents proximal to the allyl group are sterically compara-
ble in rac-1e. And thus, the (R)-Mo* species failed to distin-
guish the two enantiomers in 1e leading to the low enantio-
selectivity in its kinetic resolution (Scheme 2, right). Ferro-
cenylphosphine sulfide (1 f), in which the relative
arrangement of the three substituents is similar to that in
1d, was also a suitable substrate for the kinetic resolution,
and unreacted 1 f was recovered with 99% ee and 32%
yield with a krel value of 25 (Table 1, entry 7).
The enantioselectivity of the
kinetic resolution was sensitive
to the substituent at the allylic
2-position (R2 group in 1). In-
troduction of a bulkier substitu-
ent in place of the methyl
group in 1b improved the enan-
tioselectivity. The ARCM of
rac-1g, which has a 2-ethylallyl
tether, proceeded with excellent
selectivity (krel =30) to give the
Table 1. Molybdenum-catalyzed intraannular ARCM kinetic resolution of planar-chiral 1,2-diallylmetallo-
ACHTUNGTRENNUNG
cenes.[a]
[e]
1
Chiral L
T [8C],
t [h]
ee (yield) of
ee (yield) of
Config./optical
krel
recovered 1 [%][b,c,d]
cyclized 2 [%][b,c]
rotation of 2
recovered
substrate
with
99% ee in 37% yield (Table 1,
entry 8). With a benzyl group as
the R2 substituent in rac-1h, the
krel value was further improved
to 33 (Table 1, entry 9). Sub-
strate 1i, possessing a 2-(tri-
1
rac-1b
rac-1b
rac-1b
rac-1c
rac-1d
rac-1e
rac-1 f
rac-1g
rac-1h
rac-1i
(R)-L1
(R)-L2
(R)-L3
(R)-L3
(R)-L1
(R)-L1
(R)-L3
(R)-L3
(R)-L3
(R)-L2
23, 24
0, 1
98 (24)
5 (80)
96 (37)
96 (31)
91 (30)
4 (26)
99 (32)
99 (37)
96 (41)
97 (35)
53 (66)
31 (15)
72 (60)
52 (60)
31 (66)
<1 (74)
67 (67)
74 (59)
79 (53)
87 (57)
(+)
(+)
(+)
14
2.0
22
11
5.3
<1.1
25
30
2[f]
3
23, 12
23, 12
23, 0.5
23, 0.5
23, 12
23, 12
23, 12
23, 3
4
5
6
7
8
9
10
(+)
(À)
(À)
(R)-(+)
(+)
ACHUTNGRENmNUG ethACHTUNGTRENNyUGN lsilyl)allyl tether, was less
(+)
(À)
33
60
reactive probably due to the ex-
cessively bulky SiMe3 substitu-
ent. Both Mo/(R)-L1 and Mo/
(R)-L3 failed to afford the cy-
clized product for the reaction
with 1i. It was found that the
[a] The reaction was carried out in benzene in the presence of a metathesis catalyst (5 mol%) generated in
situ unless otherwise noted. [b] The enantiomeric excess was determined by chiral HPLC (see the Supporting
Information for details). [c] The yield of the product isolated by silica gel chromatography is given in paren-
theses. [d] The enantiomeric excess of recovered 1 was determined after conversion into 2 by a reaction with
the Grubbs II catalyst. [e] Calculated based on a first-order equation (Ref. [16]). [f] In toluene.
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Chem. Eur. J. 2013, 19, 4151 – 4154

Kinetic Resolution of 1,2-Disubstituted Ferrocenes
COMMUNICATION
Scheme 3. Stereoretentive conversion of (S)-1 f into the planar-chiral fer-
rocenylphosphine (S)-3 f.
the transformation (Scheme 3). Phosphine (S)-3 f is a novel
chiral ligand with a unique structure.[19] Its applications are
now under investigation in our group and will be reported
in due course.
Scheme 2. Comparison between 1d and 1e in the reaction with the chiral
Mo–alkylidene precatalyst [(R)-Mo*]=CHR.
In summary, we have developed an efficient method for
the kinetic resolution of racemic planar-chiral 1,2-disubsti-
tuted ferrocene derivatives through a molybdenum-cata-
lyzed asymmetric intraannular ring-closing metathesis reac-
tion.
molybdenum species coordinated with (R)-L2, which is a
more active but less enantioselective catalyst for the reac-
tion of rac-1b (see Table 1, entries 1–3), was the catalyst of
choice for the kinetic resolution of rac-1i. With this catalyst,
the ARCM of rac-1i proceeded smoothly to give the cy-
clized product (2i) with 87% ee in 57% yield, and unreacted
1i was recovered with 97% ee and 35% yield. The selectivi-
ty factor for the reaction is remarkably high being krel =60
(Table 1, entry 10).
Experimental Section
General procedure for the molybdenum-catalyzed ARCM kinetic resolu-
tion of 1: In a glovebox under prepurified argon, Mo(=NC6H3-2,6-iPr2)(=
CHCMe2Ph)ACHTNUGRTNEUNG(NC4H4)2 (4.9 mg, 9.1 mmol) and L3 (6.3 mg, 9.1 mmol) were
Single-crystal X-ray crystallography revealed that the ab-
solute configuration of the levorotatory 2 f ([a]2D5 =À26.0
(c=1.6 in CHCl3) for the sample with 99% ee), which was
derived from recovered 1 f (Table 1, entry 7), was S as
shown in Figure 1 (see the Supporting Information for de-
tails).[17] The configurations of the other ARCM products
were deduced by analogy.
dissolved in dry benzene (5 mL) in a test tube with a Teflon-sealed screw
cap. After stirring the mixture for 15 min at room temperature, benzene
(13 mL) and the metallocene substrate 1 (180 mmol) were added. The test
tube was sealed tightly and taken out of the glovebox. The test tube was
immersed in an oil bath maintained at 238C and the mixture was stirred
for 12 h. After quenching the reaction by addition of acetone (ꢀ100 mL),
the reaction mixture was passed through a pad of silica gel by using
hexane/Et2O (9:1) as the eluent. The solvent was removed under reduced
pressure and the residue was purified by preparative HPLC [LC-908 re-
cycle HPLC system (Japan Analytical Industry Co. Ltd.) with a GPC
column (JAIGEL-H, chloroform, 3.5 mLminÀ1)] to give the ARCM
product 2 and the recovered substrate 1. Recovered 1 was converted to
the corresponding compound 2 by treatment with the Grubbs II catalyst
(5 mol%) in benzene for a chiral HPLC analysis. The characterization
data of the ARCM products and the conditions for the chiral HPLC
analysis are described in the Supporting Information.
Acknowledgements
This work was supported by a Grant-in-Aid for Challenging Exploratory
Research (24655039) from MEXT, Japan (to M.O.). S.W. and S.A. are re-
cipients of the JSPS Research Fellowship for the Young Scientists.
Keywords: asymmetric synthesis
·
chirality
·
kinetic
resolution · metallocene · planar chirality · ring-closing
metathesis
Figure 1. Ball-and-stick drawing of the levorotatory planar-chiral phos-
phine sulfide (S)-(À)-2 f. All hydrogen atoms are omitted for clarity.
[1] a) E. B. Bauer, J. A. Gladysz in Handbook of Metathesis, Vol. 2
(Ed.: R. H. Grubbs), Wiley-VCH, Weinheim, 2003, Chapter 2.11,
p. 403; b) Y. Tor, Synlett 2002, 1043.
[2] a) R. L. Halterman, Chem. Rev. 1992, 92, 965; b) G. Wagner, R.
Herrmann in Ferrocenes (Eds.: A. Togni, T. Hayashi), Wiley-VCH,
Weinheim, 1995, Chapter 4, p. 173; c) A. Togni, Angew. Chem. 1996,
108, 1581; Angew. Chem. Int. Ed. Engl. 1996, 35, 1475; d) C. J. Rich-
Phosphine sulfide (S)-2 f (99% ee), which was obtained
from recovered (S)-1 f by the RCM reaction by using the
Grubbs II catalyst, could be reduced to the corresponding
phosphine quantitatively by treating with an excess of P-
ACHTUNGTRENNUNG
(NMe2)3.[18] The enantiopurity of (S)-1 f was retained during
Chem. Eur. J. 2013, 19, 4151 – 4154
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4153

M. Ogasawara, T. Takahashi et al.
ˇ
ˇ
ards, A. J. Locke, Tetrahedron: Asymmetry 1998, 9, 2377; e) P. Step-
Nagano, T. Hayashi, J. Am. Chem. Soc. 2002, 124, 9068 [addition/
correction: M. Ogasawara, T. Nagano, T. Hayashi, J. Am. Chem.
Soc. 2002, 124, 12626]; d) M. Ogasawara, T. Nagano, T. Hayashi, Or-
ganometallics 2003, 22, 1174; e) M. Ogasawara, S. Watanabe, K. Na-
kajima, T. Takahashi, Organometallics 2008, 27, 6565; f) W. Bucho-
wicz, B. Jerzykiewicz, A. Krasinska, S. Losi, A. Pietrzykowski, P. Za-
nello, Organometallics 2006, 25, 5076.
ˇ
ˇ
ˇ
ˇ
ˇ
nicka, M. Lamac in Ferrocenes (Ed.: P. Stepnicka), Wiley, New
York, 2008, Chapter 7, p. 237; f) S. Arae, M. Ogasawara, J. Synth.
Org. Chem. Jpn. 2012, 70, 593.
[3] a) T. Hayashi in Ferrocenes (Eds.: A. Togni, T. Hayashi), Wiley-
VCH, Weinheim, 1995, Chapter 2, p. 105; b) A. Togni in Metallo-
cenes, Vol. 2 (Eds.: A. Togni, R. L. Halterman), Wiley-VCH, Wein-
heim, 1998, Chapter 11, p. 685; c) T. J. Colacot, Chem. Rev. 2003,
103, 3101; d) P. Barbaro, C. Bianchini, G. Giambastiani, S. L. Parisel,
Coord. Chem. Rev. 2004, 248, 2131; e) R. G. Gꢁmez Arrayꢂs, J.
Adrio, J. C. Carretero, Angew. Chem. 2006, 118, 7836; Angew.
Chem. Int. Ed. 2006, 45, 7674; f) G. C. Fu, Acc. Chem. Res. 2006, 39,
853; g) C. Ganter in Phosphorus Ligands in Asymmetric Catalysis
(Ed. : A. Bçrner), Wiley-VCH, Weinheim, 2008, Chapter 4.3, p. 393.
[4] a) Y. Butsugan, S. Araki, M. Watanabe in Ferrocenes (Eds.: A.
Togni, T. Hayashi), Wiley-VCH, Weinheim, 1995, Chapter 3, p. 143;
b) G. C. Fu, Acc. Chem. Res. 2000, 33, 412; c) G. C. Fu, Acc. Chem.
Res. 2004, 37, 542.
[10] a) I. R. Butler, S. Mꢆssig, M. Plath, Inorg. Chem. Commun. 1999, 2,
424; b) I. R. Butler, Inorg. Chem. Commun. 2008, 11, 15; c) I. R.
Butler, Eur. J. Inorg. Chem. 2012, 4387.
[11] a) M. Scholl, S. Ding, C. W. Lee, R. H. Grubbs, Org. Lett. 1999, 1,
953; b) S. T. Nguyen, T. M. Trnka in Handbook of Metathesis, Vol. 1
(Ed.: R. H. Grubbs), Wiley-VCH, Weinheim, 2003, Chapter 1.6,
p. 61.
[12] a) R. R. Schrock, J. S. Murdzek, G. C. Bazan, J. Robbins, M.
DiMare, M. OꢄRegan, J. Am. Chem. Soc. 1990, 112, 3875; b) R. R.
Schrock in Handbook of Metathesis, Vol. 1 (Ed.: R. H. Grubbs),
Wiley-VCH, Weinheim, 2003, Chapter 1.3, p. 8.
[5] a) D. Marquarding, H. Klusacek, G. Gokel, P. Hoffmann, I. Ugi, J.
Am. Chem. Soc. 1970, 92, 5389; b) O. Riant, O. Samuel, H. B.
Kagan, J. Am. Chem. Soc. 1993, 115, 5835; c) F. Rebiꢃre, O. Riant,
L. Ricard, H. B. Kagan, Angew. Chem. 1993, 105, 644; Angew.
Chem. Int. Ed. Engl. 1993, 32, 568; d) C. J. Richards, T. Damalidis,
D. E. Hibbs, M. B. Hursthouse, Synlett 1995, 74; e) T. Sammakia,
H. A. Latham, D. R. Schaad, J. Org. Chem. 1995, 60, 10; f) Y. Nishi-
bayashi, Y. Arikawa, K. Ohe, S. Uemura, J. Org. Chem. 1996, 61,
1172; g) D. Enders, R. Peters, R. Lochtman, G. Raabe, Angew.
Chem. 1999, 111, 2579; Angew. Chem. Int. Ed. 1999, 38, 2421.
[6] a) M. Tsukazaki, M. Tinkl, A. Roglans, B. J. Chapell, N. J. Taylor, V.
Snieckus, J. Am. Chem. Soc. 1996, 118, 685; b) R. S. Laufer, U.
Veith, N. J. Taylor, V. Snieckus, Org. Lett. 2000, 2, 629; c) T. Fukuda,
K. Imazato, M. Iwao, Tetrahedron Lett. 2003, 44, 7503; d) C. Metalli-
nos, H. Szillat, N. J. Taylor, V. Snieckus, Adv. Synth. Catal. 2003, 345,
370.
[7] a) S. Siegel, H.-G. Schmalz, Angew. Chem. 1997, 109, 2569; Angew.
Chem. Int. Ed. Engl. 1997, 36, 2456; b) C. Genet, S. J. Canipa, P.
OꢄBrien, S. J. Taylor, J. Am. Chem. Soc. 2006, 128, 9336; c) A.
Bueno, M. Rosol, J. Garcꢅa, A. Moyano, Adv. Synth. Catal. 2006,
348, 2590; d) A. Mercier, W. C. Yeo, J. Chou, P. D. Chaudhuri, G.
Bernardinelli, E. P. Kꢆndig, Chem. Commun. 2009, 5227; e) A.-N.
Alba, P. Gꢁmez-Sal, R. Rios, A. Moyano, Tetrahedron: Asymmetry
2009, 20, 1314; f) D.-W. Gao, Y.-C. Shi, Q. Gu, Z.-L. Zhao, S.-L.
You, J. Am. Chem. Soc. 2013, 135, 86.
[13] Reviews of asymmetric olefin metathesis: a) A. H. Hoveyda, R. R.
Schrock, Chem. Eur. J. 2001, 7, 945; b) R. R. Schrock, A. H. Hovey-
da, Angew. Chem. 2003, 115, 4740; Angew. Chem. Int. Ed. 2003, 42,
4592; c) A. H. Hoveyda in Handbook of Metathesis, Vol. 2 (Ed.:
R. H. Grubbs), Wiley-VCH, Weinheim, 2003, Chapter 2.3, p. 128;
d) A. H. Hoveyda, R. R. Schrock in Comprehensive Asymmetric
Catalysis (Eds.: E. N. Jacobsen, A. Pfaltz, H. Yamamoto), Springer,
Berlin, 2004, Supplement 1, Chapter 44, p. 207; e) H. F. T. Klare, M.
Oestreich, Angew. Chem. 2009, 121, 2119; Angew. Chem. Int. Ed.
2009, 48, 2085; f) S. K. Collins in Science of Synthesis Stereoselective
Synthesis, Vol. 1 (Eds.: J. G. de Vries, G. A. Molander, P. A. Evans),
Thieme, Stuttgart, 2011, Chapter 1.15, p. 819. See also: g) A. H.
Hoveyda, A. R. Zhugralin, Nature 2007, 450, 243.
[14] A. S. Hock, R. R. Schrock, A. H. Hoveyda, J. Am. Chem. Soc. 2006,
128, 16373.
[15] a) J. B. Alexander, D. S. La, D. R. Cefalo, A. H. Hoveyda, R. R.
Schrock, J. Am. Chem. Soc. 1998, 120, 4041; b) R. R. Schrock, J. Y.
Jamieson, S. J. Dolman, S. A. Miller, P. J. Bonitatebus, Jr., A. H.
Hoveyda, Organometallics 2002, 21, 409; c) S. S. Zhu, D. R. Cefalo,
D. S. La, J. Y. Jamieson, W. M. Davis, A. H. Hoveyda, R. R. Schrock,
J. Am. Chem. Soc. 1999, 121, 8251.
[16] a) H. B. Kagan, J. C. Fiaud, Top. Stereochem. 1988, 18, 249; b) E.
Vedejs, M. Jure, Angew. Chem. 2005, 117, 4040; Angew. Chem. Int.
Ed. 2005, 44, 3974.
[17] CCDC-902537 ((S)-(À)-2 f.) contains the supplementary crystallo-
graphic 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_request/cif.
[18] G. A. Olah, A. Berrier, L. Ohannesian, Nouv. J. Chim. 1986, 10, 253.
[19] a) T. Sturm, W. Weissensteiner, F. Spindler, K. Mereiter, A. M.
Lꢁpez-Agenjo, B. R. Manzano, F. A. Jalꢁn, Organometallics 2002,
21, 1766; b) T. Sturm, B. Abad, W. Weissensteiner, K. Mereiter,
B. R. Manzano, F. A. Jalꢁn, J. Mol. Catal. A: Chem 2006, 255, 209.
[8] a) M. Ogasawara, S. Watanabe, L. Fan, K. Nakajima, T. Takahashi,
Organometallics 2006, 25, 5201; b) M. Ogasawara, S. Watanabe, K.
Nakajima, T. Takahashi, Pure Appl. Chem. 2008, 80, 1109; c) M.
Ogasawara, S. Watanabe, K. Nakajima, T. Takahashi, J. Am. Chem.
Soc. 2010, 132, 2136. See also: d) M. Ogasawara, S. Watanabe, Syn-
thesis 2009, 1761; e) M. Ogasawara, W.-Y. Wu, S. Arae, S. Watanabe,
T. Morita, T. Takahashi, K. Kamikawa, Angew. Chem. 2012, 124,
3005; Angew. Chem. Int. Ed. 2012, 51, 2951.
[9] a) A. J. Locke, C. Jones, C. J. Richards, J. Organomet. Chem. 2001,
637–639, 669; b) D. Hꢆerlꢇnder, N. Kleigrewe, G. Kehr, G. Erker,
R. Frçhlich, Eur. J. Inorg. Chem. 2002, 2633; c) M. Ogasawara, T.
Received: January 13, 2013
Published online: February 20, 2013
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