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Asymmetric catalytic hydrosilylation of ketones preparation of chiral ferrocenylphosphines as chiral ligands
Tetrahedronletters No. 49-50, pp 4405 - 4408, 1974.
Perc;cuon ?remr. Printed in Greet W'itein.
Asyb4t4~mIc CATALYTIC HYDRosILYLATI~N OF KETONES
PREPARATIONOF CHIRAL FERROCENYLPHOSPHINES AS CHIRAL LIGANDS
Tamio Hayashi, Keiji Yamamoto,and Makoto Kumada* Departmentof SyntheticChemistry,Kyoto University,Yoshida, Kyoto 606, Japan (Reoeivedin Jam
22 Ootober 1974; reoeired in UK for pablioation5 Noveder 1974)
Asymmetricsyntheses,especiallyhydrogenation,catalyzedby transitionmetal complexes with chiral ligandshave recently attractedmuch interest. In most cases, phosphineshaving an asymmetriccenter at the phosphorusatom1 or those derived from L-threito12or I-menthol3have been successfullyused as chiral ligands. We wish to report the preparationof new phosphineswith planar chiralitywhich arises from introducingphosphinogroups into a-dimethylaminoethylferrocene, and the use of these phosphinesas chiral ligands in asymmetriccatalytichydrosilylationof ketones with which we have been primarilyconcerned.4 Chiral ferrocenylphosphines are readily preparedby way of stereoselectivelithiationof (S)-a-ferrocenylethyldimethylamine(&).5 Thus, u1 (14 mmoles) was metalatedwith n-butyllithium (17 mmoles) in ether at room temperature,and the mixture was then treated with chlorodiphenylphosphine (28 mmoles) to give (S)-a-[(R)-2-diphenylphosphinoferrocenyl]ethyldimethylamine(PPFA). The product was purifiedby alumina-columnchromatography(eluentn-hexane/benzene, 3:l) and recrystallization from ethanol:yield 50%; mp 139'; [a]E5 +361° (c 0.6, ethanol). In a similar manner, (R)-a-[(S)-2-dimethylphosphinoferrocenyl]ethyldimethylamine(MPFA) was obtained starting with @)-A (eq. 1). PR2
Q
1) n-BuLi/EtzO
Fe
Fe
* 2) R2PCl
(11
a
&iMeNMep
EHMeNMe2
(S) or (R)-1 u
4405
(S)-(R) -PPFA
(R = Ph)
(R)-(S) -MPFA
(R = Me)
Ho. 49-50
4406
Stepwise
lithiation
of
(S)-I
V.
with n-BuLi
introduction
of
two diphenylphosphino
groups
[(R) -1’ ,2-bis
(diphenylphosphino)ferrocenyl]
in ether into
and with n-BuLi/TMEDA in ether
both
the cyclopentadienyl
ethyldimethylamine
rings
(BPPFA) (eq.
led
to give
2) n-BuLi/TMEDA/EtpO
2).
Fe -9%
~CHMeNMe 2
chirality
CHMeNMe2
(S) - (R) -BPPFA (R)-l-ethyl-2-diphenylphosphinoferrocene(EPPF)
was prepared
as shown in eq.
J’UJlPhp
1)
Fe &NeNMe2
a planar
only
element
of
PPh2
PWPh2
Acetone *
having
3.
Me1
Fe a
(2)
I
(a -A Finally,
(S)-a-
PPh2 PPh2
1) n-BuLi/EtzO
3) PhgPCl
to the
WWI
2) LiAlH4
a
CH=CH2
Fe
(3)
-a
CH2CH3 (R) -EPPF
All specific tion
new compounds gave satisfactory rotations
and circular
of
these
chiral
dichroism Table
1.
elemental
ferrocenylphosphines
(CD) spectra
Physical
(S)-(R) -PPFA
139
+361°
(c 0.6,
EtOH)
(R)-(S) -MPFA
oil
-134’
(c 0.3,
CHC13)
(S) - (R) -BPPFA
117.5
+34S”
(c 0.5,
CHCl3)
94.5
+273’
(c 0.3,
CHC13)
(S)-(R)-BPPFA,
spectrum transition.6
ferrocene
and (R)-EPPF all
chirality
has two long wavelength of
chiral
around these
have positive
whereas
opposite
1.
and
The absorp-
[ali
The CD spectra
from the planar
340 - 350 nm respectively, MPFA.
of
in Table
points
ferrocenylphosphines.
Mp (“C)
to d-d type arising
chiral
Melting
1 and 2.
Abbr .
The absorption
tivity
of
and nmr spectra.
are summarized
are shown in Figs.
constants
(R) -EPPF
aole
analyses
ferrocenylphosphines two absoption
and negative Cotton
bands at 440 and 325 nm assign-
effects
Cotton
bands, effects
are observed
reveal that
is,
optical
ac-
(S)-(R)-PPFA.
around 450 - 470 and in the case
of
(R)-(S)-
No. 49-W
4407
I 300
I
\
/ 400
500
I
j “nl
Fig. 1. CD and UV spectra of (S)-(R)-
Fig. 2. CD spectraof (S)-(R)-BPPFA
PPFA and (R)-(S)-MPFAin chloroform.
and (R)-EPPFin chloroform.
The asymmetriccatalytichydrosilylationof ketones4was carried out in the presence of rhodium complexescontainingthese chiral ferrocenylphosphines as ligands. The asymmetric Table 2. AsymmetricHydrosilylationof Ketones Catalyzedby Chiral Ferrocenylphosphine-Rhodium Complexesaat 20". Ketone
Silane
Ligand
Yieldb (%)
Configuration
Optical Purity ("a)
EtCOPh
PhMe2SiHC
(S)-(R)-PPFA
61
R
10.5
EtCOPh
PhMe2SiHC
(S)-(R)-PPFAd
40
R
9.0
t-BuCOMe
PhMe2SiHC
(S)-(R)-PPFA
71
R
19.6
MeCOPh
PhpSiH2
(R)-(S)
-MPFA
a9
R
49.2
EtCOPh
PhnSiH2
(R) - (S) -MPFA
83
R
38.3
t-BuCOMe
PhZSiH2
(R) - (S) -MPFA
74
R
41.1
t-BuCOMe
PhMe2SiHC
(R)-(S)-MPFA
29
S
23.5
MeCOPh
PhpSiH2
(S)-(R) -BPPFA
72
R
28.6
EtCOPh
PhnSiH2
(S)-(R) -BPPFA
73
R
24.5
EtCOPh
EtpSiHp
(S)-(R) -BPPFA
84
R
25.3
EtCOPh
Me$iHC
88
R
5.2
a [RhJ* = 0.05 mol%.
(R)-EPPF b
Isolatedyield. ' At 50'. d PPFA/Rh = 1.
440s
Ho. 49-50
additions
of
(eq.
The results
4).
trialkylsilanes
R1COR2
As is used.
seen
phine
or
inducing
resulted (-)-diop-Rh
ligand
In addition group of
the
potential
of
tion
using
2, fairly
the reaction
. +
optical
yield
complex
was used.
and anappropriate
catalyst
systems
are indebted
at SO0 and 20°,
respectively
2.
yields
(4)
were attained
with diphenylsilane
than the cases
The high ability
steric
place
2P*
found in the reaction
Efforts
took
R1R2&OSiR3
good optical
in higher
the reaction.
The authors
in Table
of acetophenone
to the expected
ligand
these
WI*
: +[(C~H~O)R~C~]~
was also
readily
are summarized
R3SiH
from Table
For example,
Rh complex
obtained +
[Rh]*
and dialkylsilanes
of
when MPFA or BPPFA was catalyzed
in which
by (R)-(S)-MPFA-
(R)-benzylmethylphenylphos-
(R)-(S)-MPFA
as an asymmetry
interactions
between
of pinacolone.
effects,
attractive
prochiral
substrate
toward this
end as well
might contribute as toward
the amino
to the asymmetric
the asymmetric
hydrogena-
are under way.
to Dr. Y. Imanishi
for
CD measurements.
REFERENCES
1.
W.
Knowles and M. J.
S.
and B. D. Vineyard,
J.
Sabacky,
Chem. Colmmtn., 1445 (1968).
C. S. Chem. Corrnan.,
10 (1972).
W. S. Knowles,
L. Horner,
M. J.
H. Siegel,
Sabacky,
and H. Biithe,
Angew. Chem., 80, 1034 (1968). 2.
T.-P.
Dang and H. B. Kagan, &em.
Conamcn., 481 (1971).
Idem, J. Amer. C&m. Sot.,
2,
6429
(1972). 3.
J.
D. Morrison,
SOC., 5,
R. E. Burnett,
1301 (1971);
A. M. Aguiar,
see also,
J.
C. J. Morrow,
D. Morrison
and C. Phillips,
and W. F. Masler,
J.
Org.
J. Amer. Chem. them.,
2,
270
(1974). 4.
K. Yamamoto, T. Hayashi, 54,
C45 (1973);
Dumont, J.-C. 5.
D. Marquarding,
and M. Kumada, J.
see also, Poulin,
I. Ojima,
T.-P.
H. Klusacek,
Orga?wmetaZ. Chem., 42, C65 (1972),
T. Kogure,
Dang, and H. 8. 6. Gokel,
and Y. Nagai,
Chem.
Kagan, J. Amer. Chem. Sot.,
P. Hoffmann,
and I.
Ugi,
idem,
541 (1973),
L&t., g,
ibid., W.
8295 (1973).
J. Amer. C&m. SOC., 92,
5389 (1970). 6.
M. Rosenblum, p.
40.
“Chemistry
of
the
Iron Group Metallocenes,”
Wiley,
New York,
N. Y.,
1965,
Perc;cuon ?remr. Printed in Greet W'itein.
Asyb4t4~mIc CATALYTIC HYDRosILYLATI~N OF KETONES
PREPARATIONOF CHIRAL FERROCENYLPHOSPHINES AS CHIRAL LIGANDS
Tamio Hayashi, Keiji Yamamoto,and Makoto Kumada* Departmentof SyntheticChemistry,Kyoto University,Yoshida, Kyoto 606, Japan (Reoeivedin Jam
22 Ootober 1974; reoeired in UK for pablioation5 Noveder 1974)
Asymmetricsyntheses,especiallyhydrogenation,catalyzedby transitionmetal complexes with chiral ligandshave recently attractedmuch interest. In most cases, phosphineshaving an asymmetriccenter at the phosphorusatom1 or those derived from L-threito12or I-menthol3have been successfullyused as chiral ligands. We wish to report the preparationof new phosphineswith planar chiralitywhich arises from introducingphosphinogroups into a-dimethylaminoethylferrocene, and the use of these phosphinesas chiral ligands in asymmetriccatalytichydrosilylationof ketones with which we have been primarilyconcerned.4 Chiral ferrocenylphosphines are readily preparedby way of stereoselectivelithiationof (S)-a-ferrocenylethyldimethylamine(&).5 Thus, u1 (14 mmoles) was metalatedwith n-butyllithium (17 mmoles) in ether at room temperature,and the mixture was then treated with chlorodiphenylphosphine (28 mmoles) to give (S)-a-[(R)-2-diphenylphosphinoferrocenyl]ethyldimethylamine(PPFA). The product was purifiedby alumina-columnchromatography(eluentn-hexane/benzene, 3:l) and recrystallization from ethanol:yield 50%; mp 139'; [a]E5 +361° (c 0.6, ethanol). In a similar manner, (R)-a-[(S)-2-dimethylphosphinoferrocenyl]ethyldimethylamine(MPFA) was obtained starting with @)-A (eq. 1). PR2
Q
1) n-BuLi/EtzO
Fe
Fe
* 2) R2PCl
(11
a
&iMeNMep
EHMeNMe2
(S) or (R)-1 u
4405
(S)-(R) -PPFA
(R = Ph)
(R)-(S) -MPFA
(R = Me)
Ho. 49-50
4406
Stepwise
lithiation
of
(S)-I
V.
with n-BuLi
introduction
of
two diphenylphosphino
groups
[(R) -1’ ,2-bis
(diphenylphosphino)ferrocenyl]
in ether into
and with n-BuLi/TMEDA in ether
both
the cyclopentadienyl
ethyldimethylamine
rings
(BPPFA) (eq.
led
to give
2) n-BuLi/TMEDA/EtpO
2).
Fe -9%
~CHMeNMe 2
chirality
CHMeNMe2
(S) - (R) -BPPFA (R)-l-ethyl-2-diphenylphosphinoferrocene(EPPF)
was prepared
as shown in eq.
J’UJlPhp
1)
Fe &NeNMe2
a planar
only
element
of
PPh2
PWPh2
Acetone *
having
3.
Me1
Fe a
(2)
I
(a -A Finally,
(S)-a-
PPh2 PPh2
1) n-BuLi/EtzO
3) PhgPCl
to the
WWI
2) LiAlH4
a
CH=CH2
Fe
(3)
-a
CH2CH3 (R) -EPPF
All specific tion
new compounds gave satisfactory rotations
and circular
of
these
chiral
dichroism Table
1.
elemental
ferrocenylphosphines
(CD) spectra
Physical
(S)-(R) -PPFA
139
+361°
(c 0.6,
EtOH)
(R)-(S) -MPFA
oil
-134’
(c 0.3,
CHC13)
(S) - (R) -BPPFA
117.5
+34S”
(c 0.5,
CHCl3)
94.5
+273’
(c 0.3,
CHC13)
(S)-(R)-BPPFA,
spectrum transition.6
ferrocene
and (R)-EPPF all
chirality
has two long wavelength of
chiral
around these
have positive
whereas
opposite
1.
and
The absorp-
[ali
The CD spectra
from the planar
340 - 350 nm respectively, MPFA.
of
in Table
points
ferrocenylphosphines.
Mp (“C)
to d-d type arising
chiral
Melting
1 and 2.
Abbr .
The absorption
tivity
of
and nmr spectra.
are summarized
are shown in Figs.
constants
(R) -EPPF
aole
analyses
ferrocenylphosphines two absoption
and negative Cotton
bands at 440 and 325 nm assign-
effects
Cotton
bands, effects
are observed
reveal that
is,
optical
ac-
(S)-(R)-PPFA.
around 450 - 470 and in the case
of
(R)-(S)-
No. 49-W
4407
I 300
I
\
/ 400
500
I
j “nl
Fig. 1. CD and UV spectra of (S)-(R)-
Fig. 2. CD spectraof (S)-(R)-BPPFA
PPFA and (R)-(S)-MPFAin chloroform.
and (R)-EPPFin chloroform.
The asymmetriccatalytichydrosilylationof ketones4was carried out in the presence of rhodium complexescontainingthese chiral ferrocenylphosphines as ligands. The asymmetric Table 2. AsymmetricHydrosilylationof Ketones Catalyzedby Chiral Ferrocenylphosphine-Rhodium Complexesaat 20". Ketone
Silane
Ligand
Yieldb (%)
Configuration
Optical Purity ("a)
EtCOPh
PhMe2SiHC
(S)-(R)-PPFA
61
R
10.5
EtCOPh
PhMe2SiHC
(S)-(R)-PPFAd
40
R
9.0
t-BuCOMe
PhMe2SiHC
(S)-(R)-PPFA
71
R
19.6
MeCOPh
PhpSiH2
(R)-(S)
-MPFA
a9
R
49.2
EtCOPh
PhnSiH2
(R) - (S) -MPFA
83
R
38.3
t-BuCOMe
PhZSiH2
(R) - (S) -MPFA
74
R
41.1
t-BuCOMe
PhMe2SiHC
(R)-(S)-MPFA
29
S
23.5
MeCOPh
PhpSiH2
(S)-(R) -BPPFA
72
R
28.6
EtCOPh
PhnSiH2
(S)-(R) -BPPFA
73
R
24.5
EtCOPh
EtpSiHp
(S)-(R) -BPPFA
84
R
25.3
EtCOPh
Me$iHC
88
R
5.2
a [RhJ* = 0.05 mol%.
(R)-EPPF b
Isolatedyield. ' At 50'. d PPFA/Rh = 1.
440s
Ho. 49-50
additions
of
(eq.
The results
4).
trialkylsilanes
R1COR2
As is used.
seen
phine
or
inducing
resulted (-)-diop-Rh
ligand
In addition group of
the
potential
of
tion
using
2, fairly
the reaction
. +
optical
yield
complex
was used.
and anappropriate
catalyst
systems
are indebted
at SO0 and 20°,
respectively
2.
yields
(4)
were attained
with diphenylsilane
than the cases
The high ability
steric
place
2P*
found in the reaction
Efforts
took
R1R2&OSiR3
good optical
in higher
the reaction.
The authors
in Table
of acetophenone
to the expected
ligand
these
WI*
: +[(C~H~O)R~C~]~
was also
readily
are summarized
R3SiH
from Table
For example,
Rh complex
obtained +
[Rh]*
and dialkylsilanes
of
when MPFA or BPPFA was catalyzed
in which
by (R)-(S)-MPFA-
(R)-benzylmethylphenylphos-
(R)-(S)-MPFA
as an asymmetry
interactions
between
of pinacolone.
effects,
attractive
prochiral
substrate
toward this
end as well
might contribute as toward
the amino
to the asymmetric
the asymmetric
hydrogena-
are under way.
to Dr. Y. Imanishi
for
CD measurements.
REFERENCES
1.
W.
Knowles and M. J.
S.
and B. D. Vineyard,
J.
Sabacky,
Chem. Colmmtn., 1445 (1968).
C. S. Chem. Corrnan.,
10 (1972).
W. S. Knowles,
L. Horner,
M. J.
H. Siegel,
Sabacky,
and H. Biithe,
Angew. Chem., 80, 1034 (1968). 2.
T.-P.
Dang and H. B. Kagan, &em.
Conamcn., 481 (1971).
Idem, J. Amer. C&m. Sot.,
2,
6429
(1972). 3.
J.
D. Morrison,
SOC., 5,
R. E. Burnett,
1301 (1971);
A. M. Aguiar,
see also,
J.
C. J. Morrow,
D. Morrison
and C. Phillips,
and W. F. Masler,
J.
Org.
J. Amer. Chem. them.,
2,
270
(1974). 4.
K. Yamamoto, T. Hayashi, 54,
C45 (1973);
Dumont, J.-C. 5.
D. Marquarding,
and M. Kumada, J.
see also, Poulin,
I. Ojima,
T.-P.
H. Klusacek,
Orga?wmetaZ. Chem., 42, C65 (1972),
T. Kogure,
Dang, and H. 8. 6. Gokel,
and Y. Nagai,
Chem.
Kagan, J. Amer. Chem. Sot.,
P. Hoffmann,
and I.
Ugi,
idem,
541 (1973),
L&t., g,
ibid., W.
8295 (1973).
J. Amer. C&m. SOC., 92,
5389 (1970). 6.
M. Rosenblum, p.
40.
“Chemistry
of
the
Iron Group Metallocenes,”
Wiley,
New York,
N. Y.,
1965,