Modification of Chiral Monodentate Phosphine Ligands (MOP) for Palladium-Catalyzed Asymmetric Hydrosilylation of Cyclic 1,3-Dienes

Article abstract of DOI:10.1002/1615-4169(20010330)343:3<279::AID-ADSC279>3.0.CO;2-5

Several MOP ligands 5 containing aryl groups at 2′ position of (R)-2-(diphenylphosphino)-1,1′-binaphthyl skeleton were prepared and used for palladium-catalyzed asymmetric hydrosilylation of cyclic 1,3-dienes 6 with trichlorosilane. Highest enantioselectivity was observed in the reaction of 1,3-cyclopentadiene (6a) catalyzed by a palladium complex (0.25 mol %) coordinated with (R)-2-(diphenylphosphino)-2′-(3,5-dimethyl-4-methoxyphenyl)-1,1′- binaphthyl (5f), which gave (S)-3-(trichlorosilyl)cyclopentene of 90% ee.

Full text of DOI:10.1002/1615-4169(20010330)343:3<279::AID-ADSC279>3.0.CO;2-5

FULL PAPERS
Modification of Chiral Monodentate Phosphine
Ligands (MOP) for Palladium-Catalyzed
Asymmetric Hydrosilylation of Cyclic 1,3-Dienes
Tamio Hayashi,a,* Jin Wook Han,a Akira Takeda,a Jun Tang,a Kenji Nohmi,a
Kotaro Mukaide,a Hayato Tsuji,a Yasuhiro Uozumia,b
a Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
Fax: (+81) 75-753-3988, E-mail: thayashi@kuchem.kyoto-u.ac.jp
b Present address: Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
Received December 4, 2000; Accepted January 18, 2001
Keywords:
allylsi-
lane; asymmetric ca-
talysis; chiral mono-
Abstract: Several MOP ligands 5 containing aryl complex (0.25 mol %) co-
groups at 2' position of (R)-2-(diphenylphosphino)- ordinated with (R)-2-(di-
1,1'-binaphthyl skeleton were prepared and used phenylphosphino)-2'-(3,5-
for palladium-catalyzed asymmetric hydrosilylation dimethyl-4-methoxyphe-
of cyclic 1,3-dienes 6 with trichlorosilane. Highest nyl)-1,1'-binaphthyl (5f),
dentate
phosphine
ligands; hydrosilyla-
tions; palladium
enantioselectivity was observed in the reaction of
which gave (S)-3-(trichloro-
1,3-cyclopentadiene (6a) catalyzed by a palladium silyl)cyclopentene of 90% ee.
antioselectivity (>90% ee) has been observed by use
of 2-diphenylphosphino-2'-methoxy-1,1'-binaphthyl
(MeO-MOP, 1). For styrene derivatives, 2-diphenyl-
phosphino-1,1'-binaphthyl (H-MOP, 2a)[10] and its
analogue containing the bis[3,5-bis(trifluoromethyl)-
phenyl]phosphino group (2b)[11] are more effective
than MeO-MOP, giving the hydrosilylation products
of over 95% ee. However, unfortunately, these MOP
ligands are not so effective for the hydrosilylation of
1,3-dienes. The highest enantioselectivity reported
so far was 80% ee, which is observed in the hydrosily-
lation of 1,3-cyclopentadiene in the presence of a pal-
ladium catalyst coordinated with 4,4'-biphenanthryl
analogue 3 of MeO-MOP (Figure 1).[12] Here we wish
to report that appropriate modification of the MOP li-
gand by introduction of an aryl group on the 2' posi-
tion leads to the highest enantioselectivity for 1,3-cy-
clopentadiene and 1,3-cyclohexadiene.
Introduction
Enantiomerically enriched allylic silanes are useful
synthetic intermediates that react with electrophiles
in an SE' fashion to give a wide variety of enantiomeri-
cally enriched compounds.[1] We have developed sev-
eral synthetic methods for their preparation by asym-
metric catalysis with chiral phosphine-palladium
complexes. These include the asymmetric hydrosily-
lation of 1,3-dienes,[2,3,4] cross-coupling of 1-(silyl)-
alkyl Grignard reagents with alkenyl halides,[5] allylic
silylation of allyl chlorides with disilanes,[6] and re-
duction of 3-(silyl)-2-propenyl carbonates with for-
mic acid.[7] Of these catalytic asymmetric reactions,
the asymmetric hydrosilylation is most promising
from the practical point of view, because the hydrosi-
lylation is usually carried out in the presence of not
more than 1 mol % of the palladium catalyst and the
starting 1,3-dienes are readily accessible. We have
also reported the preparation of several chiral mono-
dentate phosphine ligands (MOP) whose chirality is
due to the binaphthyl axial chirality[3] and their suc-
cessful use for several types of transition metal-cata-
lyzed asymmetric reactions[3] including palladium-
catalyzed hydrosilylation. The MOP ligands have an
advantage over others in that their fine tuning is read-
ily made by the introduction of a desired group at the
2' position. In the asymmetric hydrosilylation of sim-
ple terminal alkenes[8] and cyclic alkenes,[9] high en-
Figure 1. Structures of 1, 2, and 3.
Adv. Synth. Catal. 2001, 343, No. 3
Ó WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2001
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279

asc.wiley-vch.de
of the enantiomeric purity. The results summarized
in Table 1 show that the enantioselectivity is gener-
ally high with the aryl-substituted MOP ligands com-
pared to that reported with (R)-MeO-MOP (1) or (S)-
H-MOP (2a)[12] and that the enantioselectivity is de-
pendent strongly both on the electronic character of
the substituents and on the steric bulkiness of the aryl
group. The ligand substituted with an electron-donat-
ing group at the 4 position showed higher selectivity
than that substituted with an electron-withdrawing
group. Thus, the order of enantioselectivity is 5b
(Ar = 4-MeOC6H4, 76% ee) > 5a (Ar = C6H5, 69% ee)
> 5c (Ar = 4-CF3C6H4, 47% ee) (entries 1±3). Methyl
groups at the meta-position on the phenyl enhance
the enantioselectivity, as indicated by the observation
that the order of the selectivity is 5e (Ar = 3,5-
Me2C6H3, 79% ee) > 5d (Ar = 3-MeC6H5, 76% ee) >
5a (Ar = C6H5, 69% ee) (entries 1, 4, and 5). The li-
gand 5f which has both the electron-donating meth-
oxy group at the 4 position and the two methyl groups
at the 3 and 5 positions was the most enantioselective
ligand giving the hydrosilylation product 7a of 88% ee
at 0 °C (entry 6). At a lower reaction temperature, the
selectivity was increased to some extent (entries 7
and 8). The enantioselectivity of 90% ee observed at
±20 °C is the highest so far reported for the asym-
metric hydrosilylation of 1,3-cyclopentadiene.[15]
Results and Discussion
In our previous studies on the palladium-catalyzed
asymmetric hydrosilylation of 1,3-dienes, the use of
(R)-MeO-MOP (1) or (S)-H-MOP (2a) as a chiral lig-
and resulted in the formation of the corresponding
hydrosilylation products of low enantiomeric pur-
ity.[12] Thus, for example, the reaction of 1,3-cyclo-
pentadiene with trichlorosilane in the presence of
(R)-MeO-MOP (1) and (S)-H-MOP (2a) gave (R)-3-
(trichlorosilyl)cyclopentene of 39% and 28% ee, re-
spectively. Expecting that a sterically more bulky
group at the 2' position of the MOP ligand will bring
about higher enantioselectivity, several MOP ligands
containing aryl groups at the 2' position were pre-
pared by the nickel-catalyzed cross-coupling of (R)-
2-(diphenylphosphino)-2'-(trifluoromethanesulfonyl-
oxy)-1,1'-binaphthyl (TfO-MOP, 4)[13] with arylmag-
nesium bromides. Phenyl and substituted phenyl
groups were introduced in the presence of a catalytic
amount of NiCl2(dppe) in refluxing THF to give the
corresponding
(R)-2-(diphenylphosphino)-2'-aryl-
1,1'-binaphthyls (Ar-MOP, 5a-f) in around 60% yield
(Scheme 1).
Scheme 1. Preparation of chiral monophosphine ligands 5
(Ar±MOP).
Scheme 2. Palladium-catalyzed asymmetric hydrosilylation
of cyclic dienes 6a and 6b.
The MOP ligands thus obtained were examined for
their enantioselectivity in the palladium-catalyzed It was found that 1,3-cyclohexadiene (6b) is a little
asymmetric hydrosilylation of 1,3-cyclopentadiene less reactive than 1,3-cyclopentadiene (6a) toward
(6a) with trichlorosilane. In the presence of the palladium-catalyzed hydrosilylation, and its reac-
0.25 mol % of the palladium catalyst generated in situ tion was carried out at 20 °C. In the asymmetric hy-
from [PdCl(p-C3H5)]2 and the MOP ligand 5 (P/Pd = drosilylation of 1,3-cyclohexadiene (6b), the same
2/1), the hydrosilylation was completed at 0 °C in electronic and steric effects were observed as in the
24 h to give high yields of (S)-3-(trichlorosilyl)cyclo- case of 1,3-cyclopentadiene (6a) (entries 9±15 in Ta-
pentene (7a) (Scheme 2). The allyl(trichloro)silane ble 1). Thus, the highest enantioselectivity (76% ee
7a was allowed to react with benzaldehyde in DMF at 20 °C) was obtained with the ligand 5f that has a
according to Kobayashi's procedure[14] to give 3,5-dimethyl-4-methoxyphenyl group (entry 14), and
(3R,1'S)-(+)-3-[hydroxy(phenyl)methyl]cyclopentene
the order of enantioselectivity of the MOP ligands is
(8a), which was subjected to HPLC analysis with a 5b > 5a > 5c for the electronic effect of the substituents
chiral stationary phase column for the determination at the para-position (entries 9±11) and 5e > 5d > 5a for
280
Adv. Synth. Catal. 2001, 343, 279±283

FULL PAPERS
Table 1. Palladium-catalyzed asymmetric hydrosilylation of
Experimental Section
cyclic dienes with trichlorosilane.[a]
Entry Diene Ligand T [°C] Time Yield
% ee[c] Configu-
ration[d]
General Remarks
[h]
[%][b]
All moisture-sensitive manipulations were carried out un-
der a nitrogen atmosphere. Nitrogen gas was dried by pas-
sage through P2O5. Optical rotations were recorded with a
JASCO DIP-370 polarimeter. NMR spectra were recorded
on a JEOL JNM LA500 spectrometer (500 MHz for 1H and
202 MHz for 31P) in CDCl3. Chemical shifts are reported in d
ppm referenced to an internal SiMe4 standard for 1H NMR
and to an external 85% H3PO4 standard for 31P NMR. HPLC
analysis was performed on a JASCO PU±980 liquid chroma-
tograph system with a chiral stationary phase column, Dai-
cel Chiralpak OB-H. GC analysis was carried out on a Hew-
lett Packard 6890 system with a chiral stationary phase
column, CP-Chirasil-Dex CB.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
6a
6a
6a
6a
6a
6a
6a
6a
6b
6b
6b
6b
6b
6b
6b
5a
5b
5c
5d
5e
5f
0
0
0
0
0
24
24
24
24
24
24
72
72
24
24
24
24
24
24
72
84
84
83
85
83
79
95
89
74
73
90
78
82
74
75
69
76
47
76
79
88
89
90
55
63
32
64
66
76
79
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
0
5f
5f
±10
±20
20
20
20
20
20
20
0
5a
5b
5c
5d
5e
5f
5f
[a]
The hydrosilylation was carried out without solvent. The
catalyst was generated in situ by mixing [PdCl(p-C3H5)]2 and
a chiral phosphine ligand 5. The initial ratio of diene/HSiCl3/
Pd/P is 1/1.2/0.0025/0.0050.
Preparation of (R)-2-(Diphenylphosphino)-2'-
aryl-1,1'-binaphthyls (Ar±MOP; 5)
[b] Yield of product isolated by bulb-to-bulb distillation.
A typical procedure is given for the preparation of (R)-2-(di-
phenylphosphino)-2'-(3,5-dimethyl-4-methoxyphenyl)-1,1'-
binaphthyl (5 f). A mixture of (R)-2-(diphenylphosphino)-2'-
(trifluoromethanesulfonyloxy)-1,1'-binaphthyl (4) (1.12 g,
[c]
Determined by HPLC analysis of alcohol 8a with a chiral
stationary phase column (Daicel Chiralpak OB-H, hexane/
2-propanol = 9/1). Determined by GC analysis of alcohol 8b
with a chiral stationary phase column (CP-Chirasil-Dex CB).
1.91 mmol),
dichloro[1,3-bis(diphenylphosphino)ethane]-
[d]
Determined by optical rotation of alcohols 8. For entry 8
nickel (0.202 g, 0.38 mmol), and 3,5-dimethyl-4-methoxyphe-
nylmagnesium bromide (1.5 M, 9 mL, in tetrahydrofuran)
was heated at reflux for 24 h under nitrogen. After cooling to
room temperature, the reaction mixture was quenched with
saturated ammonium chloride (20 mL) on an ice bath, and
extracted with diethyl ether. The extract was dried over anhy-
drous MgSO4 and the solvent was evaporated. The residue
was chromatographed on silica gel (hexane/ethyl acet-
ate = 5/1) to give 0.634 g (58% yield) as a white solid.
(8a), [a]2D0: +27.2 (c 1.86, chloroform). For entry 15 (8b),
[a]2D0: +11.1 (c 0.82, benzene).
the steric effect caused by the meta-methyl substitu-
tion (entries 9, 12, and 13).
The strong dependency of the enantioselectivity on
the aryl group at the 2' position of the MOP ligand 5
may suggest that the aryl group is located close to
the palladium and that it plays an important role in
determining the stereochemical outcome in the pre-
sent asymmetric hydrosilylation. Structural studies
on the MOP-palladium complexes by NMR spectro-
scopy and X-ray crystal analysis are now in progress.
(R)-2-(Diphenylphosphino)-2'-(3,5-dimethyl-4-methoxy-
phenyl)-1,1'-binaphthyl (5f): [a]2D0: +183 (c 1.00, chloro-
form); 1H NMR (CDCl3): d = 1.83 (s, 6H), 3.61 (s, 3 H), 6.61
(s, 2 H), 6.65 (t, J = 6.8 Hz, 2 H), 6.83 (d, J = 8.3 Hz, 1 H), 6.90
(t, J = 6.8 Hz, 2 H), 7.00 (t, J = 7.3 Hz, 1 H), 7.04 (t, J = 7.3 Hz,
2 H), 7.09 (t, J = 6.8 Hz, 2 H), 7.12 (t, J = 7.8 Hz, 1 H), 7.17 (t,
J = 7.3 Hz, 1 H), 7.22 (dd, J = 8.8, 2.9 Hz, 1 H), 7.35 (t,
J = 8.3 Hz, 1 H), 7.36 (t, J = 6.9 Hz, 1 H), 7.45 (d, J = 8.8 Hz,
1 H), 7.50 (t, J = 6.8 Hz, 1 H), 7.63 (d, J = 8.3 Hz, 1 H), 7.74 (d,
J = 8.8 Hz, 1 H), 7.86 (d, J = 8.3 Hz, 1 H), 7.91 (d, J = 8.3 Hz,
1 H), 8.03 (d, J = 8.3 Hz, 1 H); 31P{1H}NMR: d = ±19.5 (s); anal.
calcd. for C41H33PO: C, 85.99; H, 5.81; found: C, 85.71; H,
5.91.
Conclusions
In summary, we have shown that some of the MOP li-
gands which contain aryl groups at the 2' position of 2-
(diphenylphosphino)-1,1'-binaphthyl skeleton are ef-
fective for the palladium-catalyzed asymmetric hydro-
silylation of cyclic 1,3-dienes with trichlorosilane giv-
ing the corresponding allylic silanes of up to 90% ee.
The clear relationship between the enantioselectivity
and the electronic and steric characters of the aryl
group observed here provide us with significant infor-
mation on the design of more effective chiral ligands.
(R)-2-(Diphenylphosphino)-2'-phenyl-1,1'-binaphthyl
(5a): White solid (53% yield); [a]2D0: +143 (c 1.00, chloro-
form); 1H NMR (CDCl3): d = 6.61 (t, J = 6.9 Hz, 2 H), 6.76 (d,
J = 8.3 Hz, 1 H), 6.91 (t, J = 7.4 Hz, 4 H), 6.96 (t, J = 8.3 Hz,
1 H), 7.00±7.05 (m, 5 H), 7.08 (t, J = 6.9 Hz, 2 H), 7.10 (t,
J = 8.3 Hz, 1 H), 7.15 (t, J = 7.3 Hz, 1 H), 7.21 (dd, J = 8.8,
3.0 Hz, 1 H), 7.31 (t, J = 7.4 Hz, 1 H), 7.34 (t, J = 6.9 Hz, 1 H),
7.42 (d, J = 8.3 Hz, 1 H), 7.47 (t, J = 7.8 Hz, 1 H), 7.66 (d,
J = 8.3 Hz, 1 H), 7.73 (d, J = 8.3 Hz, 1 H), 7.84 (d, J = 7.8 Hz,
1 H), 7.90 (d, J = 8.3 Hz, 1 H), 8.04 (d, J = 8.3 Hz, 1 H);
31P{1H}NMR d = ±18.9 (s); anal. calcd. for C38H27P: C, 88.69;
H, 5.29; found: C, 88.79; H, 5.49.
Adv. Synth. Catal. 2001, 343, 279±283
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asc.wiley-vch.de
(R)-2-(Diphenylphosphino)-2'-(4-methoxyphenyl)-1,1'-
binaphthyl (5b): White solid (43% yield); [a]2D0: +183 (c 1.00,
chloroform); 1H NMR (CDCl3): d = 3.68 (s, 3 H), 6.41 (d,
J = 8.8 Hz, 2 H), 6.63 (t, J = 6.9 Hz, 2 H), 6.79 (d, J = 8.3 Hz,
1 H), 6.88 (d, J = 8.8 Hz, 2 H), 6.90 (t, J = 7.4 Hz, 2 H), 7.03 (t,
J = 8.3 Hz, 1 H), 7.05 (t, J = 6.9 Hz, 2 H), 7.10 (t, J = 7.6 Hz,
2 H), 7.12 (t, J = 7.6 Hz, 1 H), 7.16 (t, J = 7.4 Hz, 1 H), 7.24
(dd, J = 8.8, 3.0 Hz, 1 H), 7.33 (t, J = 7.6 Hz, 1 H), 7.36 (t,
J = 6.9 Hz, 1 H), 7.42 (d, J = 8.3 Hz, 1 H), 7.50 (t, J = 6.9 Hz,
1 H), 7.63 (d, J = 8.8 Hz, 1 H), 7.75 (d, J = 8.3 Hz, 1 H), 7.86 (d,
J = 8.3 Hz, 1 H), 7.91 (d, J = 8.3 Hz, 1 H), 8.04 (d, J = 8.3 Hz,
1 H); 31P{1H}NMR: d = ±19.2 (s); anal. calcd. for C39H29PO: C,
86.01; H, 5.37; found: C, 86.00; H, 5.39.
3-(Trichlorosilyl)cyclopentene (7a): 1H NMR (CDCl3):
d = 2.15±2.25 (m, 2 H), 2.45±2.51 (m, 2 H), 2.71 (m, 1 H), 5.70
(dq, J = 5.5, 2.5 Hz, 1 H), 6.00 (dq, J = 5.5, 2.5 Hz, 1 H).
3-(Trichlorosilyl)cyclohexene (7b): 1H NMR (CDCl3):
d = 1.55±1.59 (m, 1 H), 1.78±1.91 (m, 2 H), 1.98±2.08 (m, 3 H),
2.08±2.32 (m, 1 H), 5.71 (dq, J = 7.9, 2.3 Hz, 1 H), 5.95 (dq,
J = 7.9, 3.0 Hz, 1 H).
Reaction of Allylsilane 7 with Benzaldehyde in DMF
A mixture of allyl(trichloro)silane 7 (0.4 mmol) and benzalde-
hyde (21 mL, 0.2 mmol) in DMF (1 mL) was stirred at 0 °C for
2 h. Saturated aqueous sodium hydrogen carbonate was added
to quench the reaction, and the aqueous layer was extracted
with diethyl ether. The extract was dried over anhydrous
MgSO4, and the solvent was evaporated. The crude product
was purified by preparative TLC on silica gel (hexane/ethyl
acetate = 4/1) to give a high yield of homoallyl alcohol 8.[14]
(R)-2-(Diphenylphosphino)-2'-(4-trifluoromethylphe-
nyl)-1,1'-binaphthyl (5c): White solid (65% yield); [a]D20
:
+182 (c 1.20, chloroform); 1H NMR (CDCl3): d = 6.55 (t,
J = 7.6 Hz, 2 H), 6.84 (d, J = 8.4 Hz, 1 H), 6.88 (t, J = 7.5 Hz,
2 H), 7.01±7.14 (m, 10 H), 7.17 (d, J = 7.9 Hz, 1 H), 7.22 (dd,
J = 8.4, 2.5 Hz, 1 H), 7.35 (t, J = 7.1 Hz, 1 H), 7.41 (d,
J = 9.8 Hz, 1 H), 7.42 (t, J = 7.6 Hz, 1 H), 7.52 (t, J = 7.3 Hz,
1 H), 7.62 (d, J = 8.3 Hz, 1 H), 7.78 (d, J = 8.3 Hz, 1 H), 7.88 (d,
J = 7.9 Hz, 1 H), 7.94 (d, J = 8.3 Hz, 1 H), 8.08 (d, J = 8.3 Hz,
1 H); 31P{1H}NMR: d = ±14.2 (s); anal. calcd. for C39H26F3P: C,
80.40; H, 4.50; found: C, 80.67; H, 4.73.
Acknowledgements
This work was supported by ªResearch for the Futureº Pro-
gram, the Japan Society for the Promotion of Science, and a
Grant-in-Aid for Scientific Research, the Ministry of Educa-
tion, Japan.
(R)-2-(Diphenylphosphino)-2'-(3-methylphenyl)-1,1'-bi-
naphthyl (5d): White solid (64% yield); [a]2D0: +207 (c 0.11,
chloroform); 1H NMR (CDCl3): d = 1.93 (s, 3 H), 6.61 (t,
J = 6.9 Hz, 2 H), 6.71 (d, J = 7.7 Hz, 1 H), 6.75±6.84 (m, 2 H),
6.90±7.12 (m, 10 H), 7.17 (t, J = 7.2 Hz, 1 H), 7.22 (dd, J = 8.6,
2.7 Hz, 1 H), 7.33 (t, J = 7.0 Hz, 1 H), 7.36 (t, J = 7.0 Hz, 1 H),
7.44 (d, J = 8.5 Hz, 1 H), 7.49 (t, J = 7.5 Hz, 1 H), 7.65 (d,
J = 8.6 Hz, 1 H), 7.72 (d, J = 8.6 Hz, 1 H), 7.84 (d, J = 8.1 Hz,
1 H), 7.91 (d, J = 8.2 Hz, 1 H), 8.04 (d, J = 8.5 Hz, 1 H);
31P{1H}NMR: d = ±14.0 (s); anal. calcd. for C39H29P: C, 88.61;
H, 5.53; found: C, 88.34; H, 5.69.
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1,1'-binaphthyl (5e): White solid (54% yield); [a]2D0: +193
(c 1.00, chloroform); 1H NMR (CDCl3): d = 1.87 (s, 6 H),
6.61±6.65 (m, 5 H), 6.82 (d, J = 8.3 Hz, 1 H), 6.92 (t,
J = 8.3 Hz, 2 H), 6.98 (t, J = 7.4 Hz , 1 H), 7.04 (t, J = 8.3 Hz ,
2 H), 7.09 (t, J = 7.4 Hz, 2 H), 7.15 (t, J = 7.4 Hz, 1 H), 7.17 (t,
J = 7.4 Hz, 1 H), 7.23 (dd, J = 8.8, 3.0 Hz, 1 H), 7.33 (t,
J = 6.9 Hz, 1 H), 7.36 (t, J = 6.9 Hz, 1 H), 7.45 (d, J = 8.3 Hz,
1 H), 7.48 (t, J = 6.9 Hz, 1 H), 7.64 (d, J = 8.3 Hz, 1 H), 7.72 (d,
J = 8.8 Hz, 1 H), 7.84 (d, J = 8.3 Hz, 1 H), 7.91 (d, J = 8.3 Hz,
1 H), 8.04 (d, J = 8.3 Hz, 1 H); 31P{1H}NMR: d = ±19.2 (s); anal.
calcd for C40H31P: C, 88.53; H, 5.76; found: C, 88.69; H, 5.80.
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Palladium-Catalyzed Hydrosilylation of Diene 6
A typical procedure is given for entry 1 in Table 1. To a mix-
ture of [PdCl(p-C3H5)]2 (0.9 mg, 0.0025 mmol), a chiral li-
gand 5a (5.1 mg, 0.0100 mmol), and 1,3-cyclopentadiene
(6a) (132 mg, 2.0 mmol) was added trichlorosilane
(0.24 mL, 2.4 mmol) at 0 °C, and the mixture was kept stir-
ring in a sealed tube at 0 °C for 24 h. The reaction mixture
was distilled (bulb-to-bulb) under
a reduced pressure
(120 °C/15 torr) to give 339 mg (84% yield) of 3-(trichlorosi-
lyl)cyclopentene (7a).
282
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