[Me2C(C5H4)2TiMe2]: An open-bent titanocene catalyst for the hydro-silylation of bulky 1,3-dienes

Article abstract of DOI:10.1055/s-0030-1259687

Motivated by our preliminary results on Cp₂TiF ₂-catalysed 1,4-hydrosilylation of monosubstituted dienes, we assessed the performance of several titanium complexes for the hydrosilylation of 2,3-dimethylbutadiene, a representative bu

Full text of DOI:10.1055/s-0030-1259687

LETTER
679
[Me2C(C5H4)2TiMe2]: An Open-Bent Titanocene Catalyst for the Hydro-
silylation of Bulky 1,3-Dienes
Titanocene
Catal
o
H
x
a
of Bulky 1
n
,3-Dienes a Pop,a Jin Lan Cui,b Louis Adriaenssens,a Virginie Comte,a Pierre Le Gendre*a
a
Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB-UMR CNRS 5260, Université de Bourgogne, 9 Avenue Alain
Savary, BP 47870, 21078 Dijon Cedex, France
E-mail: pierre.le-gendre@u-bourgogne.fr
Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, KY 40292, USA
b
Received 30 November 2010
stable titanium precatalyst Cp2TiF2.6 This complex is the
only known precatalyst capable of selectively generating
(E)-allylsilanes.7 The reaction proceeded well with buta-
diene and monosubstituted dienes such as isoprene,
Abstract: Motivated by our preliminary results on Cp2TiF2-cataly-
sed 1,4-hydrosilylation of monosubstituted dienes, we assessed the
performance of several titanium complexes for the hydrosilylation
of 2,3-dimethylbutadiene, a representative bulky diene. An open-
bent titanocene complex [Me2C(C5H4)2TiMe2] performed the best myrcene, and pentadiene. However, attempted hydrosily-
and proved to be efficient for the hydrosilylation of a variety of sub-
lation of sterically more demanding dienes (disubstituted
strates such as disubstituted dienes, activated alkenes, and even an
acetylene.
dienes) met with little success. In an effort to widen the
scope of this reaction we decided to investigate the cata-
lytic properties of other titanium precatalysts, and we
present the results here.
Key words: hydrosilylation, titanium, diene, allylsilane, homo-
geneous catalysis
Considering our previous success with Cp2TiF2, we first
Allylsilanes are indispensable compounds widely em-
ployed as synthetic reagents in organic synthesis.1 Among
the wide number of synthetic methods to prepare these
versatile reagents,2,3 metal-catalysed hydrosilylation of
1,3-dienes is attractive as it avoids the use of highly reac-
tive organometallic reagents and their associated limita-
tions.4 Several late-transition-metal complexes catalyse
this reaction with those based on Rh and Pd being espe-
cially useful as they are selective, predominantly giving
1,4-addition of the hydrosilane.5 However, when unsym-
metric dienes are used, the Rh- or Pd-catalysed reaction
generally leads to a mixture of regioisomers (tail or head
products) via Z-specific 1,4-addition.
assessed the efficacy of a series of difluoride complexes
as precatalysts in the dihydrosilylation of sterically chal-
lenging dienes. Unfortunately, whereas activation of
Cp2TiF2 by PhSiH3 proceeded in a few minutes, activation
periods with other complexes ranged from a few minutes
to several hours at varying temperatures which rendered a
comparative study risky. Taking into account that dialkyl
titanocene complexes may also be good-candidates as
precatalysts for the hydrosilylation of dienes,8 we contin-
ued our investigation using a variety of titanium complex-
es with methyl groups as equatorial ligands. We thus
assessed the efficacy of these complexes in the catalytic
hydrosilylation of 2,3-dimethyl-1,3-butadiene with
PhSiH3 (Scheme 1).
In 2005, our group described the first regio- and stereo-
selective anti-1,4-hydrosilylation of dienes using the air-
SiH2Ph
R
[Ti] cat.
(3 mol%)
R
+ PhSiH3
or
toluene–THF
60 °C, 3 h (R = Me)
or r.t., 15 min (R = H)
SiH2Ph
SiH2Ph
3
2 R = Me
4 R = H
PPh2
Me
SiMe3
Me
Me
Me
Me
Me
Ti
Me
SiMe3
Me
Me
Ti
Ti
Ti
Ti
Me
1a
1d
1b
1c
1e
R = Me
R = H
(2 21%)
(4 35%)
(3 25%)
(–)
(3 29%)
(–)
(2 <5%)
(4 30%)
(2 76%)
(4 87%)
Scheme 1 Screening of titanium complexes as precatalysts for the hydrosilylation of 2,3-dimethyl-1,3-butadiene and isoprene with PhSiH3
SYNLETT 2011, No. 5, pp 0679–0683
x
x.
x
x.
2
0
1
1
Advanced online publication: 25.02.2011
DOI: 10.1055/s-0030-1259687; Art ID: D31210ST
© Georg Thieme Verlag Stuttgart · New York

680
R. Pop et al.
LETTER
Dimethyltitanocene complexes 1a–e were generated in Table 1 Scope of [Me2C(C5H4)2TiMe2] (1e) Catalysed Hydrosilyla-
tiona
situ from the corresponding dichloride complexes and two
equivalents of MeLi. After stirring one hour at room tem-
Entry Substrate
1
Product
Time (h) Yield (%)
perature, phenylsilane was added to the orange solution,
and the reaction mixture was briefly heated to 60 °C (1–2
min) until the colour changed to black. 2,3-Dimethylbuta-
diene was then added at room temperature, and the reac-
tion was stirred at 60 °C for three hours. Volatiles were
evaporated, and the products were separated by flash
chromatography. Using these conditions, complex 1a led
to the formation of targeted hydrosilylated product 2 in
21% yield and also to oligomerisation of PhSiH3. Com-
plexes 1b and 1c with bulkier, more electron-rich cyclo-
pentadienyl ligands did not catalyse the hydrosilylation
reaction. However, both were active giving mainly doubly
silylated product 3 in 25% and 29% yield, respectively.
Complex 1b also catalysed the competitive dehydropoly-
merisation of PhSiH3 under these conditions, whereas a
redistribution of 20% of PhSiH3 into Ph2SiH2 was ob-
served as the main side reaction when using 1c as precat-
alyst. Recent studies conducted on the electrochemical
properties of the complex [(h5-C5H5)(h5-C5H4PPh2)TiCl2]
have highlighted its particularly electron-poor character
and thus it was of interest in our screening.9 In the event
the dimethyl variant 1d gave only traces of the expected
hydrosilylation product 2. We next studied the ansa-com-
plex 1e exhibiting a pronounced bent geometry and a pos-
sibly more open reactive surface than Cp2TiMe2.10 This
last proved to be the most effective catalyst leading to full
conversion of phenylsilane after three hours and giving al-
lylsilane 2 in 76% yield. It should be noted that, aside
from fitting nicely into a comparative study, complex 1e
was the best precatalyst studied, outperforming all other
Ti complexes, whether they contained fluorine or methyl
equatorial ligands, in the hydrosilylation of 2,3-dimethyl-
1,3-butadiene.11
SiH2Ph
SiH2Ph
0.25
87b
76
83
85
4
2
3
4
3
2
6
2
5
SiH2Ph
SiH2Ph
6
SiH2Ph
Ph
5
6
4.5
4
75
34
Ph
Ph
Ph
7
SiH2Ph
SiH2Ph
8
7
8
21
4
40
SiH2Ph
87b
10
Ph
Ph
Ph
9
3
75
72
SiH2Ph
Ph
11
PhH2Si
The comparative study was expanded to include the hy-
drosilylation of isoprene using 1a–e as precatalysts. Once
again the ansa-titanocene complex 1e performed the best,
promoting the trans-1,4-hydrosilylation of isoprene in
87% yield in 15 minutes at room temperature.12 Cp2TiMe2
1a was a distant second giving only a 35% yield under
similar conditions. Interestingly, the electron-poor diphe-
nylphosphino-substituted dimethyltitanocene complex 1d
gave a comparable result to Cp2TiMe2 (30% yield) where-
as both electron-rich and bulky titanium complexes 1b
and 1c did not show any activity in hydrosilylation or si-
lylation of isoprene at room temperature.
Ph
10
24
Ph
Ph
Ph
12
a Conditions: ansa-Cp2TiCl2 (1e, 0.036 mmol), MeLi (0.072 mmol),
PhSiH3 (1.2 mmol), substrate (3 mmol), 60 °C.
b Reaction at r.t.
butadiene, an example of a 1,4-disustituted diene. The hy-
drosilylation took place smoothly but with different regi-
oselectivity, furnishing only the 1,2-addition product 7
(entry 5). Cyclic dienes such as 1,3-cyclohexadiene and
1,3-cycloheptadiene also underwent hydrosilylation to
yield (2-cyclohexenyl)(phenyl)silane 8 and (2-cyclohep-
tenyl)(phenyl)silane 9 albeit in only modest yields.
With these results in hand, we started to explore the scope
of the ansa-dimethyltitanocene-catalysed hydrosilylation
(Table 1). As observed for 2,3-dimethylbutadiene, hy-
drosilylation of 2-methyl-1,3-pentadiene and 3-methyl-
1,3-pentadiene required higher reaction temperature and
longer reaction time with respect to isoprene (Table 1, en-
tries 2–4 vs. entry 1). In both cases, the hydrosilylation
took place regio- and stereoselectively to give (E)-allylsi-
lanes 5 and 6 in 83% and 85% yields, respectively.13 We
next attempted the hydrosilylation of 1,4-diphenyl-1,3-
A proposed mechanism of the reaction using 2-methyl-
1,3-pentadiene as a representative substrate is reported in
Scheme 2. Initially, as proposed by Harrod,
[Me2C(C5H4)2TiH(SiPhH2)] (A) is generated from
[Me2C(C5H4)2TiMe2] 1e and phenylsilane.14 Then, hy-
drotitanation of the internal double bond of the diene oc-
curs leading to the h1-allyl titanium complex (B).
Isomerisation, via a syn-p-allyltitanium complex (C), to
Synlett 2011, No. 5, 679–683 © Thieme Stuttgart · New York

LETTER
Titanocene Catalyst for the Hydrosilylation of Bulky 1,3-Dienes
681
Me
Ti
Me
PhSiH3
H
Ti
PhH2Si
SiH2Ph
A
Ti
SiH2Ph
Ti
H
SiH2Ph
B
SiH2Ph
PhSiH3
Ti
Ti
SiH2Ph
SiH2Ph
D
C
Scheme 2 Postulated mechanism of the [Me2C(C5H4)2TiMe2]-catalyzed hydrosilylation of 2-methyl-1,3-pentadiene as representative substrate
the less congested and, thus, more stable h1-allyl complex silylation of alkynes. Phenylsilane added to
(D) followed by subsequent s-bond metathesis with a diphenylacetylene in the presence of 3 mol% 1e giving
molecule of phenylsilane leads to the desired allylsilane exclusively (E)-vinylsilane 12 in good yield (entry 10).
and regenerates the active catalyst (A). As mentioned
In summary, we have shown that the ansa-dimethylti-
above, the hydrosilylation of 1,4-diphenyl-1,3-butadiene
tanocene complex is a very efficient catalyst for the hy-
led preferentially to 1,2-addition product whereas other
drosilylation of 1,3-dienes. It gives (E)-allylsilanes with
high regio- and stereoselectivities from isoprene and a va-
dienes led to 1,4-addition. This regioselectivity is consis-
tent with the formation of the more stable allyltitanium in-
riety of disubstituted dienes. Cyclic dienes also underwent
termediate.
hydrosilylation under similar conditions. In addition, the
The reaction was then extended to substrates other than complex is also able to promote hydrosilylation of sty-
dienes such as styrene, 1,1-diphenylethylene, and diphe- rene, 1,1-diphenylethylene, and diphenylacetylene in
nylacetylene. The reaction between styrene and phenyl- good yields, making it a versatile addition to the toolbox
silane led to rapid and regioselective hydrosilylation at of hydrosilylation catalysts.
room temperature leading to the linear product in 87%
yield (entry 8). Surprisingly, a complete change of regi-
oselectivity was observed in the hydrosilylation of diphe-
nylethylene, which gave the 2,1-addition product. This
regioselectivity was reported earlier by other groups in the
hydrosilylation of the same substrate using Ca-, Sr-, and
Yb-based catalysts.15 Finally, the ansa-dimethyl-
titanocene complex also proved effective for the hydro-
General Considerations
All experiments were carried out under an atmosphere of purified
argon using vacuum line techniques. Glassware was flame-dried be-
fore use. Solvents were dried and distilled under argon from sodium
and benzophenone before use. Elemental analyses were performed
on a EA 1108 CHNS-O FISONS. H NMR and 13C NMR spectra
1
were recorded on Bruker 300 MHz Avance spectrometer. Chemical
Synlett 2011, No. 5, 679–683 © Thieme Stuttgart · New York

682
R. Pop et al.
LETTER
shifts are denoted in ppm (d) relative to TMS (1H). Coupling con-
stants are reported in Hz. Dienes were purchased from Aldrich and
distilled under an argon atmosphere. Silanes were purchased from
Aldrich and used without further purification. Dichloride precursors
of complexes 1c,16 1d,17 and 1e10a were prepared as reported in the
literature. Titanocene dichloride and bis(pentamethylcyclopentadi-
enyl)titanium dichloride were purchased from Aldrich.
(E)-(1,4-Diphenyl-3-buten-2-yl)phenylsilane (7)
Yield 283 mg, 75%. 1H NMR (300 MHz, CDCl3): d = 2.47 (m, 1 H,
CHCH2), 2.88 (m, 2 H, CH2), 4.26 (m, 2 H, SiH2), 6.13 (m, 1 H,
=CH), 6.25 (s, 1 H, =CH), 7.16 (m, 15 H, Ph). 13C{1H} NMR (75
MHz, CDCl3): d = 31.3, 36.8, 125.8, 126.0, 126.4, 126.6, 127.6,
128.3, 128.5, 128.7, 129.9, 130.8, 131.1, 135.9, 137.9, 141.2. Anal.
Calcd for C22H22Si: C, 84.02; H, 7.05. Found: C, 84.12; H, 7.28.
Procedure for the Catalytic Hydrosilylation
(2-Cyclohexenyl)phenylsilane (8)
1
Methyllithium (1 M in Et2O, 0.072 mL, 0.072 mmol) was added to
a stirred, black solution of ansa-Cp2TiCl2 (10 mg, 0.036 mmol) in
dry toluene (0.5 mL) at 0 °C. The cooling bath was removed, and
the reaction was stirred for 1 h at r.t. A solution of phenylsilane
(0.15 mL, 1.2 mmol) in dry THF (0.5 mL) was added, and the or-
ange solution was heated to 60 °C until the color turned to dark
blue. After cooling to r.t., diene (3 mmol) was added, and the reac-
tion proceeded under the conditions described in Table 1. The reac-
tion was monitored by GC. After consumption of the silane, the
solvent was removed by evaporation, and the product was purified
by silica gel chromatography (pentane).
Yield 76 mg, 34%. IR (neat): nSi–H = 2132 cm–1. H NMR (300
MHz, CDCl3): d = 1.55 (m, 3 H, CH2 + CH), 2.02 (m, 4 H, CH2),
4.29 (m, 2 H, SiH2), 7.41 (m, 3 H, Ph), 7.63 (m, 2 H, Ph). 13C{1H}
NMR (75 MHz, CDCl3): d = 21.7, 22.1, 24.7, 24.9, 126.4, 127.3,
128.0, 129.7, 131.8, 135.6. Anal. Calcd for C12H16Si: C, 76.53; H,
8.56. Found: C, 76.84; H, 8.91.
(2-Cycloheptenyl)phenylsilane (9)
Yield 97 mg, 40%. 1H NMR (300 MHz, CDCl3): d = 1.74 (m, 4 H,
CH2), 2.25 (m, 4 H, CH2), 4.49 (m, 2 H, SiH2), 5.79 (m, 2 H, CH),
7.40 (m, 3 H, Ph), 7.60 (m, 2 H, Ph). 13C{1H} NMR (75 MHz,
CDCl3): d = 21.0, 21.7, 26.1, 26.7, 126.9, 128.5, 130.5, 131.1,
134.6, 141.1. Anal. Calcd for C13H18Si: C, 77.16; H, 8.97. Found:
C, 76.80; H, 8.43.
(2,3-Dimethyl-2-butenyl)phenylsilane (2)
Yield 174 mg, 76%. IR (neat): nSi–H = 2169 cm–1. H NMR (300
1
MHz, CDCl3): d = 1.61 (s, 3 H, CH3), 1.70 (s, 3 H, CH3), 1.72 (m,
3 H, CH3), 1.94 (m, 2 H, CH2), 4.36 (t, 2 H, 3JH–H = 3.9 Hz, SiH2),
7.41 (m, 3 H, Ph), 7.61 (m, 2 H, Ph). 13C{1H} NMR (75 MHz,
CDCl3): d = 18.9, 20.0, 20.4, 24.0, 122.5, 123.1, 127.7, 129.3,
132.7, 135.0. Anal. Calcd for C12H18Si: C, 75.71; H, 9.53. Found:
C, 75.52; H, 9.27.
(Phenylethyl)phenylsilane (10)
1
Yield 221 mg, 87%. IR (neat): nSi-H = 2133 cm–1. H NMR (300
MHz, CDCl3): d = 1.20 (m, 2 H, CH2CH2), 2.70 (m, 2 H, CH2C),
3
4.23 (t, 2 H, JH–H = 3.6 Hz, SiH2), 7.23 (m, 10 H, Ph). 13C{1H}
NMR (75 MHz, CDCl3): d = 12.2, 31.2, 125.8, 127.9, 128.1, 128.4,
129.7, 132.2, 135.3, 144.0. 29Si NMR (CDCl3): d = –31.0. Anal.
Calcd for C14H16Si: C, 79.18; H, 7.59. Found C, 79.39; H, 7.88.
(2,3-Dimethyl-2-butene-1,4-diyl)bis(phenylsilane) (3)
Yield 52 mg, 29%. 1H NMR (300 MHz, CDCl3): d = 1.59 (s, 6 H,
CH3), 1.90 (t, 4 H, 3JH–H = 3.9 Hz, CH2), 4.31 (t, 4 H, 3JH–H = 3.9 Hz,
SiH2), 7.38 (m, 6 H, Ph), 7.41 (m, 4 H, Ph). 13C{1H} NMR (75 MHz,
CDCl3): d = 19.4, 20.4, 122.7, 127.9, 129.6, 132.8, 135.2. Anal. Cal-
cd for C18H24Si2: C, 72.90; H, 8.16. Found: C, 72.97; H, 8.31.
(1,1-Diphenylethyl)phenylsilane (11)
Yield 258 mg, 75%. 1H NMR (300 MHz, CDCl3): d = 1.79 (s, 3 H,
CH3), 4.70 (s, 2 H, SiH2), 7.28 (m, 15 H, Ph). 13C{1H} NMR (75
MHz, CDCl3): d = 25.5, 37.6, 125.6, 127.6, 128.3, 129.8, 131.0,
136.4, 147.3. 29Si NMR (CDCl3): d = –19.1. Anal. Calcd for
C20H20Si: C, 83.28; H, 6.99. Found: C, 82.93; H, 6.09.
(E)-(2-Methyl-2-butenyl)phenylsilane (4)
1
Yield 183 mg, 87%. IR (neat): nSi–H = 2138 cm–1. H NMR (300
MHz, CDCl3): d = 1.50 (d, 3 H, 3JH–H = 7 Hz, CH3CH), 1.57 (s, 3 H,
CH3C), 1.78 (d, 2 H, 3JH–H = 3.9 Hz, CH2Si), 4.24 (t, 2 H, 3JH–H = 3.9
Hz, SiH2), 5.07 (q, 1 H, 3JH–H = 7.0 Hz, CH=C), 7.30 (m, 3 H, Ph),
7.48 (m, 2 H, Ph). 13C{1H} NMR (75 MHz, CDCl3): d = 13.6, 17.6,
23.0, 118.3, 128.0, 129.6, 132.0, 132.7, 135.2. Anal. Calcd for
C11H16Si: C, 74.93; H, 9.15. Found: C, 75.12; H, 9.31.
(E)-(1,2-Diphenylvinyl)phenylsilane (12)
Yield 247 mg, 72%. IR (neat): nSi–H = 2134 cm–1. H NMR (300
1
MHz, CDCl3): d = 5.5 (s, 2 H, SiH2), 7.24 (m, 10 H, Ph), 7.62 (s, 1
H, CH=C), 7.74 (m, 4 H, Ph), 8.22 (m, 1 H, Ph). 13C{1H} NMR (75
MHz, CDCl3): d = 123.3, 128.3, 129.9, 131.6, 135.7. 29Si NMR
(CDCl3): d = –11.7. Anal. Calcd for C20H18Si: C, 83.86; H, 6.33.
Found: C, 83.45; H, 6.41.
(E)-(2-Methyl-2-pentenyl)phenylsilane (5)
Yield 190 mg, 83%; Z/E = 22:78). IR (neat): nSi–H = 2147 cm–1. 1H
NMR (300 MHz, CDCl3): d = 0.96 (t, 3 H, 3JH–H = 7 Hz, CH3CH2),
1.69 (s, 3 H, CH3C), 1.89 (m, 2 H, CH2Si), 2.02 (qt, 2 H, 3JH–H = 7.0
Acknowledgment
The authors thank the Conseil Régional de Bourgogne (PARI SMT
IME - Région Bourgogne), the Ministère de l’Enseignement Su-
périeur et de la Recherche, and the Centre National de la Recherche
Scientifique (CNRS) for financial support.
3
Hz, CH2CH3), 4.38 (t, 2 H, JH–H = 7.0 Hz, SiH2), 5.12 (t, 1 H,
3JH–H = 7.0 Hz, CH=C), 7.40 (m, 3 H, Ph), 7.60 (m, 2 H, Ph).
13C{1H} NMR (75 MHz, CDCl3): d = 14.2, 17.5, 21.2, 22.7, 126.2,
127.7, 129.3, 130.3, 132.4, 135.1. Anal. Calcd for C12H18Si: C,
75.71; H, 9.53. Found: C, 75.70; H, 9.53.
References and Notes
(E)-(3-Methyl-3-penten-2-yl)phenylsilane (6)
1
Yield 193 mg, 85%. IR (neat): nSi–H = 2143 cm–1. H NMR (300
(1) Reviews: (a) Sakurai, H. Pure Appl. Chem. 1982, 54, 1.
(b) Hosomi, A. Acc. Chem. Res. 1988, 21, 200.
(c) Langkopf, E.; Shinzer, D. Chem. Rev. 1995, 95, 1375.
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Org. Chem. 2004, 3173.
MHz, CDCl3): d = 1.10 (d, 3 H, 3JH–H = 7.2 Hz, CH3CH), 1.51 (d, 3
3
H, JH–H = 6.6 Hz, CH3CH=), 1.57 (s, 3 H, CH3C), 1.87 (m, 1 H,
CHCH3), 4.14 (m, 1 H, SiH2), 4.19 (m, 1 H, SiH2), 5.04 (q, 1 H,
3JH–H = 6.6 Hz, CH3CH=C), 7.29 (m, 3 H, Ph), 7.46 (m, 2 H, Ph).
13C{1H} NMR (75 MHz, CDCl3): d = 13.5, 15.4, 16.5, 28.0, 116.6,
127.8, 129.5, 132.4, 135.6, 137.6. Anal. Calcd for C12H18Si: C,
75.71; H, 9.53. Found: C, 75.91; H, 9.88.
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Synlett 2011, No. 5, 679–683 © Thieme Stuttgart · New York

LETTER
Titanocene Catalyst for the Hydrosilylation of Bulky 1,3-Dienes
683
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(9) Roullier, L.; Mugnier, Y.; Pousson, E.; Moïse, C.; Richard,
P.; Le Gendre, P.; Harvey, P. H. unpublished results.
(10) The dihedral angle between the two Cp rings in
[Me2C(Cp2TiCl2)] is about 9° bigger than that of Cp2TiCl2,
indicating a more open geometry: (a) Shaltout, M. R.;
Corey, J. Y.; Rath, N. P. J. Organomet. Chem. 1995, 503,
205. (b) Wang, B.; Mu, B.; Deng, X.; Cui, H.; Xu, S.; Zhou,
X.; Zou, F.; Li, Y.; Yang, L.; Li, Y.; Hu, Y. Chem. Eur. J.
2005, 11, 669.
(11) The efficacy of Cp2TiF2 in the hydrosilylation of mono-
substituted 1,3-dienes prompted us to assess the catalytic
performance of the difluoro-ansa-titanocene. Unfortunately,
in our hands activation of the ansa-difluorotitanocene
precatalyst was not possible.
(4) (a) Speier, J. L. Adv. Organomet. Chem. 1979, 17, 441.
(b) Marciniec, B. Hydrosilylation: A Comprehensive
Review on Recent Advances; Springer: Berlin, 2009, 3.
(5) (a) Ojima, I.; Kumagai, M. J. Organomet. Chem. 1978, 157,
359. (b) Ojima, I. J. Organomet. Chem. 1977, 134, C1.
(c) Ojima, I.; Kumagai, M. J. Organomet. Chem. 1977, 134,
C6. (d) Hayashi, T.; Kebeta, K. Tetrahedron Lett. 1985, 26,
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30, 2143. (f) Gustafsson, M.; Frejd, T. J. Chem. Soc., Perkin
Trans. 1 2002, 102. (g) Gustafsson, M.; Frejd, T.
(12) The geometry of 2 was determined to be E by comparison of
the NMR spectra with those reported previously, see ref. 5.
(13) The E configuration of 5 and 6 was unambiguously
determined by NOESY NMR experiments.
J. Organomet. Chem. 2004, 689, 438.
(6) Bareille, L.; Becht, S.; Cui, J.; Le Gendre, P.; Moïse, C.
Organometallics 2005, 24, 5802.
(7) This process has been used by Leighton for the synthesis of
a spongistatin 1 fragment, see: Spletstoser, J. T.; Zacuto,
M. J.; Leighton, J. L. Org. Lett. 2008, 10, 5593.
(14) Aitken, C. T.; Harrod, J. F.; Samuel, E. J. Am. Chem. Soc.
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(15) (a) Buch, F.; Brettar, J.; Harder, S. Angew. Chem. Int. Ed.
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Inorg. Chem. 2007, 46, 5320.
(8) For dialkyl metallocene catalysed hydrosilylation of
alkenes, alkynes and their derivatives, see: (a) Takahashi,
T.; Hasegawa, M.; Suzuki, N.; Saburi, M.; Rousset, C. J.;
Fanwick, P. E.; Negishi, E. J. Am. Chem. Soc. 1991, 113,
(16) Lappert, M. F.; Picket, C. J.; Riley, P. I.; Yarrow, P. I. W.
J. Chem. Soc., Dalton Trans. 1981, 805.
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Synlett 2011, No. 5, 679–683 © Thieme Stuttgart · New York

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