A novel chiral phosphino-phosphaferrocene: Its coordination behavior and application to palladium-catalyzed asymmetric allylic alkylation

Article abstract of DOI:10.1021/om010440e

The synthesis of a novel chiral phosphino-phosphaferrocene ligand is described. The ligand possesses two electronically distinctive donor moieties and behaves either as a monodentate (with a free phosphaferrocene) or a bidentate ligand depending on stoichiometry with a coordinating transition-metal center. In the palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate, a clear correlation was observed between the enantioselectivity of the reaction and a Pd/phosphino-phosphaferrocene molar ratio. With a deficient amount (to the Pd) of the chiral ligand, the highest enantioselectivity (99% ee) was achieved.

Full text of DOI:10.1021/om010440e

Organometallics 2001, 20, 3913-3917
3913
A Novel Ch ir a l P h osp h in o-P h osp h a fer r ocen e: Its
Coor d in a tion Beh a vior a n d Ap p lica tion to
P a lla d iu m -Ca ta lyzed Asym m etr ic Allylic Alk yla tion
Masamichi Ogasawara, Kazuhiro Yoshida, and Tamio Hayashi*
Department of Chemistry, Graduate School of Science, Kyoto University,
Sakyo, Kyoto 606-8502, J apan
Received May 24, 2001
The synthesis of a novel chiral phosphino-phosphaferrocene ligand is described. The ligand
possesses two electronically distinctive donor moieties and behaves either as a monodentate
(with a free phosphaferrocene) or a bidentate ligand depending on stoichiometry with a
coordinating transition-metal center. In the palladium-catalyzed asymmetric allylic alkylation
of 1,3-diphenyl-2-propenyl acetate, a clear correlation was observed between the enantiose-
lectivity of the reaction and a Pd/phosphino-phosphaferrocene molar ratio. With a deficient
amount (to the Pd) of the chiral ligand, the highest enantioselectivity (99% ee) was achieved.
In tr od u ction
phosphino-phosphaferrocene (-)-5 was prepared. The
basic framework of our chiral phosphaferrocene (-)-5
is different from that of the planar chiral phosphafer-
rocenes of Ganter and Fu, and (-)-5 is obtained in an
enantiomerically pure form without resolution. Phos-
phaferrocenes are electronically quite different from
classical tertiary phosphines in that they have a weak
σ-donating and strong π-accepting character.4 Thus, the
phosphino-phosphaferrocene 5 possesses two distinc-
tive ligating moieties, showing two different coordina-
tion modes depending on the stoichiometry with a metal.
The design of chiral ligands has been a central subject
in the development of asymmetric reactions. Recently,
Ganter1 and Fu2 have reported several chiral phospha-
ferrocenes. Their chirality is based on the phosphafer-
rocene planar chirality, and enantiomerically pure
samples were obtained by resolution of the correspond-
ing racemates. Some of these new classes of chiral
ligands (two representative examples are shown below)
have been successfully applied to transition-metal-
catalyzed symmetric reactions and have demonstrated
their potential usefulness.1,2
Here we wish to report on the new chiral phosphino-
phosphaferrocene (-)-5: its preparation, coordination
behavior, and application to the palladium-catalyzed
asymmetric allylic alkylation5 where the enantioselec-
tivity is clearly related to the coordination behavior.
We have recently reported on preparation of the chiral
phosphole (-)-1.3 This phosphole is the first example
of an enantiomerically pure chiral phosphole in which
chiral substituents attach directly to the carbon atoms
of the phosphole ring. The phosphole was readily
transformed into the corresponding chiral and enantio-
merically pure phospholyl anion 2, from which the novel
Resu lts
P r ep a r a tion a n d Ch a r a cter iza tion of a Ch ir a l
P h osp h in o-P h osp h a fer r ocen e. The chiral phosphi-
(1) (a) Ganter, C.; Brassat, L.; Ganter, B. Tetrahedron: Asymmetry
1997, 8, 2607. (b) Ganter, C.; Brassat, L.; Ganter, B. Chem. Ber./ Recl.
1997, 130, 1771. (c) Ganter, C.; Brassat, L.; Glinsbo¨ckel, C.; Ganter,
B. Organometallics 1997, 16, 2862. (d) Ganter, C.; Glinsbo¨ckel, C.;
Ganter, B. Eur. J . Inorg. Chem. 1998, 1163. (e) Ganter, C.; Kaulen,
C.; Englert, U. Organometallics 1999, 18, 5444.
(2) (a) Qiao, S.; Fu, G. C. J . Org. Chem. 1998, 63, 4168. (b) Qiao, S.;
Hoic, D. A.; Fu, G. C. Organometallics 1998, 17, 773. (c) Shintani, R.;
Lo, M. M.-C.; Fu, G. C. Org. Lett. 2000, 2, 3695. (d) Tanaka, K.; Qiao,
S.; Tobisu, M.; Lo, M. M.-C.; Fu, G. C. J . Am. Chem. Soc. 2000, 122,
9870.
(4) (a) Fischer, J .; Mitschler, A. Ricard, L.; Mathey, F. J . Chem. Soc.,
Dalton Trans. 1980, 2522. (b) Mathey, F.; Fischer, J .; Nelson, J . H.
Struct. Bonding 1983, 55, 153. (c) Mathey, F. J . Organomet. Chem.
1990, 400, 149. (d) Mathey, F. Coord. Chem. Rev. 1994, 137, 1.
(5) (a) Consiglio, G.; Waymouth, R. M. Chem. Rev. 1989, 89, 257.
(b) Frost, C. G.; Howarth, J .; Williams, J . M. J . Tetrahedron: Asym-
metry 1992, 3, 1089. (c) Trost, B. M.; Van Vranken, D. L. Chem. Rev.
1996, 96, 395. (d) Pfaltz, A.; Lautens, M. In Comprehensive Asymmetric
Catalysis; J acobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.; Springer:
Berlin, 1999; Vol. II, p 833. (e) Trost, B. M.; Lee, C. In Catalytic
Asymmetric Synthesis, 2nd ed.; Ojima, I., Ed.; Wiley-VCH: Weinheim,
Germany, 2000; p 593.
(3) Ogasawara, M.; Yoshida, K.; Hayashi, T. Organometallics 2001,
20, 1014.
10.1021/om010440e CCC: $20.00 © 2001 American Chemical Society
Publication on Web 08/09/2001

3914 Organometallics, Vol. 20, No. 18, 2001
Ogasawara et al.
Sch em e 1. Syn th esis of th e Ch ir a l
P h osp h in o-P h osp h a fer r ocen e (-)-5
no-phosphaferrocene 5 was prepared by a reaction
sequence outlined in Scheme 1. Treatment of (ferroce-
nylmethyl)diphenylphosphine (3)6 with a mixture of Al/
AlCl3/mesitylene in cyclohexane in the presence of a
stoichiometric amount of H2O removed one of the two
η5-cyclopentadienyl ligands to give an 82% yield of a
mixture of cationic mesitylene complexes 4 and 4′ in a
ratio of 9:1.7 The preferential formation of the phosphino
complex 4 indicates that the unsubstituted η5-cyclopen-
tadienyl ligand in 3 was more labile than that substi-
tuted with the (diphenylphosphino)methyl group. The
mixture of 4 and 4′ was used for the next step without
separating the two species. The mixture of the cationic
complexes was allowed to react with the chiral lithium
phospholide 2, which was generated in situ from (-)-1
and lithium metal.8 Subsequent purification by column
chromatography over silica gel gave the phosphino-
phosphaferrocene (-)-5 in 31% yield as a highly viscous
orange oil.
F igu r e 1. 31P NMR spectra of reaction mixtures of (-)-5
and 6 with varied molar ratios (from top to bottom, (-)-
5/6 ) 1/0, 3/1, 2/1, 1.5/1, and 1/1) recorded at 202 MHz in
CD2Cl2.
Sch em e 2. Coor d in a tion Beh a vior of (-)-5 tow a r d
P d (II)
Because the C2 symmetry of 2 is lost when it is
incorporated into the phosphaferrocene (-)-5, the ligand
has no symmetry elements. The four H-C5 hydrogens
in η5-C5H4CH2PPh2 are inequivalent to one another and
1
give four resonances in the H NMR spectrum. Analo-
gously, the two â-hydrogens in the phosphacyclopenta-
dienyl ligand in (-)-5 are diastereotopic and are de-
tected as two clearly separated 1H NMR resonances. The
31P NMR spectrum of (-)-5 shows two signals at δ -11.1
and -63.4, which are assigned to the -PPh2 and the
phospholyl, respectively (Figure 1). No coupling is
detected between the two 31P signals.
Coor d in a tion Beh a vior of th e P h osp h in o-P h os-
p h a fer r ocen e. Reactions of (-)-5 with PdCl2(cod) (6)
in CD2Cl2 were examined in various (-)-5:6 molar
ratios. The coordination behavior of (-)-5 was monitored
by 31P{1H} NMR (Figure 1). Treatment of (-)-5 with
an equimolar or a slight excess of 6 completely con-
sumed the phosphino-phosphaferrocene to give the new
Pd complex PdCl2[(-)-5] (7) cleanly (Scheme 2). The two
31P NMR resonances of 7, detected at δ 35.0 (-PPh2)
and δ 70.0 (phosphaferrocene), were coupled with each
other with a small coupling constant (2J PP ) 9.1 Hz).
This indicates the coordination of (-)-5 in a cis fashion.
When a slight excess of (-)-5 (1.5 equiv with respect to
6) was used, no free ligand was detected and two new
(6) Marr, G.; White, T. M. J . Chem. Soc., Perkin Trans. 1 1973, 1995.
(7) Astruc, D. Tetrahedron 1983, 39, 4027.
(8) Robert, R. M. G.; Wells, A. S. Inorg. Chim. Acta 1986, 112, 171.

A Novel Chiral Phosphino-Phosphaferrocene
Organometallics, Vol. 20, No. 18, 2001 3915
Ta ble 1. Asym m etr ic Allylic Alk yla tion of
r a c-1,3-Dip h en yl-2-p r op en yl Aceta te Ca ta lyzed by
a P a lla d iu m /(-)-5 Com p lex
palladium species emerged in addition to 7. The two new
species were generated in a ca. 55:45 molar ratio at 20
°C, and each of them showed a pair of singlet resonances
in the 31P NMR spectrum (δ -64.1 and 19.0 for the
major isomer; δ -64.6 and 29.9 for the minor isomer).
The NMR analyses revealed that the two new species
are cis- and trans-PdCl2[(-)-5]2 (cis- and trans-8), in
which (-)-5 coordinates with the PPh2 moiety as a
monodentate ligand. The major and minor isomers were
assigned to trans-8 and cis-8, respectively, by compari-
son of the 31P NMR chemical shifts of the coordinating
PPh2 moieties.9 As expected, the two new species were
generated cleanly from the reaction of (-)-5 with 6 in a
2:1 molar ratio. With a large excess of (-)-5 (>2 equiv
with respect to 6), unreacted (-)-5 was observed in
addition to cis- and trans-8, and no 7 was detected. All
these processes are reversible, and addition of 6 to the
mixture of cis- and trans-8 regenerates 7 quantitatively.
The coordination behavior of (-)-5 toward palladium-
(II), a tendency to be a monodentate ligand rather than
a chelating ligand in the presence of an extra amount
of the ligand, indicates that coordination of the phos-
phaferrocene moiety is weaker than that of the PPh2
moiety. The 31P NMR measurement of the closely
related platinum(II) complex PtCl2[(-)-5] (9), which was
prepared from PtCl2(cod) and (-)-5 in dichloromethane,
confirmed the difference in their coordination abilities.
In the 31P NMR spectrum of 9, two resonances were
(-)-5/Pda
% eec
entry (mol/mol) temp (°C) time (h) yieldb (%) (confignd)
1
2
3
4
5
6
7
1.5/1
2/1
3/1
4/1
8/1
20
20
20
20
20
20
-20
24
24
24
24
24
24
96
97
99
99
97
99
97
99
97 (R)
97 (R)
91 (R)
87 (R)
77 (R)
98 (R)
99 (R)
0.75/1
0.75/1
a
A relative molar ratio between (-)-5 and palladium (as a
monomer). Isolated yield by silica gel chromatography. c Deter-
b
mined by HPLC analyses with a chiral stationary phase column
d
(Daicel Chiralcel OD-H, 98/2 hexane/2-propanol). Determined on
the basis of the sign of the specific rotation of the product.15
alkylation product. The enantioselectivity of the reaction
was sensitive to stoichiometry between palladium and
the chiral ligand (-)-5. The product with 97% ee was
obtained from 1.5 equiv (with respect to Pd monomer)
of (-)-5 (entry 1). The absolute configuration of the
product was determined to be R on the basis of the sign
of the specific rotation.12 The enantioselectivity de-
creased as the (-)-5/Pd ratio increased. The ee value in
the product was diminished to 91% with 3 equiv of the
ligand (entry 3) and to 77% with a large excess (8 equiv)
of (-)-5 (entry 5). On the other hand, a deficient amount
of (-)-5 ((-)-5/Pd ) 0.75) enhanced the selectivity to
98% ee (entry 6). Although lowering the temperature
to -20 °C slowed the reaction, the enantioselectivity was
further improved to 99% ee and the product was
obtained in 99% yield in 96 h (entry 7). This enantio-
selectivity is one of the highest values reported to date
for the reaction.
2
detected at δ 10.1 and 49.4 with a small J PP coupling
of 15.5 Hz, and they were assigned to the -PPh2 and
the phospholyl, respectively. The two signals were
accompanied by 195Pt-31P satellite signals, and the 1J PtP
coupling constants were 4183 Hz for the -PPh2 signal
and 3586 Hz for the phospholyl signal. The observation
demonstrates that the Pt-PPh2 bond is shorter than
the Pt-phospholyl bond: i.e., the former is stronger than
the latter.10 Because both PPh2 and the phospholyl
moieties have identical ligands (chlorides) at their trans
positions in the complex 9, the relative Pt-P bond
length (bond strength) between the two in 9 should
directly correlate with the relative coordination abili-
tyies of the two phosphorus moieties in (-)-5.
Discu ssion
When the phosphino-phosphaferrocene (-)-5 is ap-
plied to the palladium-catalyzed allylic alkylation as a
chiral ligand, the phosphaferrocene part in (-)-5 is
responsible for constructing an effective chiral environ-
ment at the palladium center of the catalyst. At the
monodentate coordination of (-)-5, the phosphafer-
rocene moiety is apart from the metal center, and thus
high enantioselectivity is not expected for the catalyst
with the monodentate (-)-5 (Figure 2). The correlation
between the (-)-5/Pd molar ratio and the enantioselec-
tivity in the Pd-catalyzed allylic alkylation can be
explained by competitive catalysis of several palladium
species with the different coordination modes of (-)-5.
With the deficient amount of the ligand, the monoden-
tate coordination of (-)-5 could be effectively eliminated,
and all of the ligand coordinates to the palladium in a
bidentate manner. Since the remaining palladium pre-
cursor [PdCl(π-C3H5)]2 is not an effective catalyst of the
Ap p lica tion of (-)-5 to P a lla d iu m -Ca ta lyzed Al-
lylic Alk yla tion . The potential of (-)-5 as a chiral
ligand in asymmetric synthesis was explored for the
palladium-catalyzed enantioselective allylic alkylation.5
It was found that a palladium complex generated in situ
from [PdCl(π-C3H5)]2 and (-)-5 is an effective catalyst
for asymmetric allylic alkylation of racemic 1,3-diphen-
yl-2-propenyl acetate with dimethyl malonate in the
presence of BSA (Table 1).11 The reaction at 20 °C was
completed in 24 h to give a quantitative yield of the
(9) Redfield, D. A.; Cary, L. W.; Nelson, J . H. Inorg. Chem. 1975,
14, 50.
(10) Mather, G. G.; Pidcock, A.; Rapsey, G. J . N. J . Chem. Soc.,
Dalton Trans. 1973, 2095.
(11) Trost, B. M.; Brickner, S. J . J . Am. Chem. Soc. 1983, 105, 568.
(12) (a) Hayashi, T.; Yamamoto, A.; Hagihara, T.; Ito, Y. Tetrahedron
Lett. 1986, 27, 191. (b) Hayashi, T.; Yamamoto, A.; Ito, Y.; Nishioka,
E.; Miura, H.; Yanagi, K. J . Am. Chem. Soc. 1989, 111, 6301.

3916 Organometallics, Vol. 20, No. 18, 2001
Ogasawara et al.
chemical shifts are externally referenced to 85% H3PO4.
Optical rotations were measured on a J ASCO DIP-370 pola-
rimeter.
((Diph en ylph osph in o)m eth yl)fer r ocen e (3). Oxalyl chlo-
ride (56.7 mL, 650 mmol) was added dropwise to a solution of
ferrocenylmethanol (8.85 g, 41.0 mmol) in THF (320 mL)
containing a catalytic amount of DMF (0.56 mL) at -20 °C.
After gas evolution had ceased, the reaction mixture was
concentrated under reduced pressure. The residual solid was
dissolved in THF and filtered through a pad of Celite. The
filtrate was cooled to -78 °C, and to this was added dropwise
KPPh2 solution, which was prepared from diphenylphosphine
(17.1 mL, 98.4 mmol) and potassium hydride (3.98 g, 98.4
mmol) in THF (200 mL) at 0 °C. After the addition, the solution
was warmed to room temperature and stirred overnight. The
mixture was quenched with water and evaporated to dryness
under reduced pressure. The residue was extracted with CH2-
Cl2 under nitrogen. The crude material was prepurified by
silica gel column chromatography (benzene as an eluent) under
nitrogen. The pure product was obtained by a second silica
gel column chromatography (elution with 3/1 hexane/benzene)
under nitrogen. Yield: 11.2 g (29.2 mmol, 71%). This product
is characterized by comparison of the spectroscopic data with
those reported previously.6
F igu r e 2. Two catalytically active species.
allylic alkylation, the highest ee value was obtained
with an excellent chemical yield.
Con clu d in g Rem a r k s
The novel chiral phosphino-phosphaferrocene (-)-5
was prepared from the chiral phosphole (-)-1. Because
of the different electronic characteristics between the
two donor moieties in (-)-5, it behaves either as a
monodentate or a bidentate ligand. The two coordination
modes of (-)-5 can be controlled by adjusting a (-)-5/
transition-metal molar ratio. The new chiral ligand was
applied to the enantioselective palladium-catalyzed
allylic alkylation, and the very high enantioselectivity
(99% ee) was achieved under the conditions where the
bidentate coordination of (-)-5 was dominant.
(η6-Mesitylen e)[η5-((d ip h en ylp h osp h in o)m eth yl)cyclo-
p en ta d ien yl]ir on (II) Hexa flu or op h osp h a te (4). Aluminum
chloride (5.87 g, 44.0 mmol), aluminum powder (0.30 g, 11.0
mmol), 3 (4.23 g, 11.0 mmol), 1,3,5-mesitylene (5.78 mL, 41.5
mmol), and water (0.20 mL, 11.0 mmol) were refluxed in
cyclohexane (30 mL) for 5 h. The mixture was cooled to 0 °C
and quenched with cold water (40 mL). The aqueous layer was
separated, filtered, and washed with ether. Excess NH4PF6
solution was added, and the resulting yellow solid was collected
on a filter and washed with cold water. The solid was dried,
washed with ether, and recrystallized from CH2Cl2/ether to
give the title compound with ca. 10% of inseparable byproduct,
which was (η6-mesitylene)(η5-cyclopentadienyl)iron(II) hexaflu-
orophosphate (4′).17 Yield: 5.09 g (ca. 74% of 4 and 8% of 4′).
1H NMR (acetone-d6): δ 2.46 (s, 9H), 3.35 (s, 2H), 4.56 (t, J )
2.0 Hz, 2H), 4.83 (t, J ) 2.0 Hz, 2H), 6.15 (s, 3H), 7.30-7.39
(m, 10H). 31P{1H} NMR (acetone-d6): δ -7.40 (s), 69.7 (m).
1′-((Dip h en ylp h osp h in o)m eth yl)-2,5-bis[(-)-m en th yl]-
1-p h osp h a fer r ocen e (5). Lithium metal (125 mg, 18.0 mmol)
was added to a solution of 1 (786 mg, 1.80 mmol) in THF (30
mL) at room temperature. The mixture was stirred until
disappearance of 1 (checked by TLC). The solvent was removed
in vacuo, and the residue was dissolved in 1,4-dioxane (30 mL).
The mixture was added to a solution of 4 (2.24 g, ca. 90%
purity, ca. 3.60 mmol) in 1,4-dioxane (60 mL) at 100 °C. The
resulting mixture was stirred for 2 h at this temperature. After
this mixture was cooled, ca. 60 mL of benzene was added and
the solution was filtered through a pad of Celite. The mixture
was evaporated to dryness under reduced pressure, and the
crude product was chromatographed on silica gel (elution with
4/1 hexane/benzene) under nitrogen. Yield: 376 mg (0.554
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All anaerobic and/or moisture-
sensitive manipulations were carried out with standard Schlenk
techniques under predried nitrogen or with glovebox tech-
niques under prepurified argon. Tetrahydrofuran, Et2O, and
1,4-dioxane were distilled from benzophenone-ketyl under
nitrogen prior to use. Dichloromethane was distilled from CaH2
under nitrogen prior to use. EtOH was dried over magnesium
ethoxide, distilled, and stored in a glass flask with a Teflon
stopcock under nitrogen. CD2Cl2 and CDCl3 were dried over
P2O5, vacuum-distilled, and stored in the glovebox. Ferroce-
nylmethanol was prepared from formylferrocene and LiAlH4.
Racemic 1,3-diphenyl-2-propenyl acetate was obtained from
the corresponding alcohol and acetic anhydride. The chiral
phosphole 1,3 Ph2PH,13 PdCl2(cod),14 PtCl2(cod),15 and [PdCl-
16
(π-C3H5)]2 were prepared as reported. Aluminum powder,
NH4PF6, KOAc, N,O-bis(trimethylsilyl)acetamide, and di-
methyl malonate were purchased from Wako Pure Chemical
Industries and used as received. Oxalyl chloride and lithium
metal were purchased from Aldrich Chemical Co. and used
as received. DMF, aluminum chloride, mesitylene, and cyclo-
hexane were purchased from Nacalai Tesque and used as
received. The reaction progress was monitored by analytical
thin-layer chromatography (TLC) using 0.25 mm Merck F-254
silica gel glass plates. Visualization of the TLC plates was
achieved by UV illumination. NMR spectra were recorded on
a J EOL J NM LA500 spectrometer (1H, 500 MHz; 13C, 125
1
mmol, 31%). H NMR (CDCl3): δ 0.68-1.09 (m, 26H), 1.32-
1.39 (m, 2H), 1.58-1.62 (m, 2H), 1.70-1.75 (m, 3H), 1.78-
1.91 (m, 4H), 2.01 (dq, J ) 12.8 and 2.2 Hz, 1H), 3.23
(unresolved q, 2H), 3.77 (m, 1H), 3.87 (m, 1H), 4.10-4.11 (m,
1H), 4.31-4.32 (m, 1H), 4.78 (dd, J PH ) 4.9 Hz and J HH ) 2.9
Hz, 1H), 4.81 (dd, J PH ) 5.6 Hz and J HH ) 2.9 Hz, 1H), 7.31-
7.34 (m, 6H), 7.36-7.42 (m, 4H). 31P{1H} NMR (CDCl3): δ
-63.4 (s), -11.1 (s). [R]20D ) -142 (c 1.00, CHCl3). Anal. Calcd
for C42H56FeP2: C, 74.33; H, 8.32. Found: C, 74.21; H, 8.41.
Dich lor o[1′-((d ip h en ylp h osp h in o)m eth yl)-2,5-bis[(-)-
m en th yl]-1-p h osp h a fer r ocen e]p la tin u m (9). An equimolar
mixture of PtCl2(cod) and (-)-5 in dichloromethane was stirred
for 1 h at room temperature, and then all the volatiles were
1
MHz; 31P, 202 MHz). H and 13C chemical shifts are reported
in ppm downfield of internal tetramethylsilane. 31P NMR
(13) Bourumeau, K.; Gaumont, A. C.; Denis, J . M. J . Organomet.
Chem. 1997, 529, 205.
(14) Drew, D.; Doyle, J . R. Inorg. Synth. 1972, 13, 52.
(15) McDermott, J . X.; White, J . F.; Whitesides, G. M. J . Am. Chem.
Soc. 1976, 98, 6521.
(17) Khand, I. U.; Pauson, P. L.; Watts, W. E. J . Chem. Soc. C 1968,
(16) Tatsuno, A.; Yoshida, T.; Otsuka, S. Inorg. Synth. 1979, 19, 220.
2257.

A Novel Chiral Phosphino-Phosphaferrocene
Organometallics, Vol. 20, No. 18, 2001 3917
removed under reduced pressure. The yellow residue was
dissolved in a minimum amount of CH2Cl2. Recrystallization
by slow diffusion of acetone into the CH2Cl2 solution at room
temperature gave the title complex quantitatively as a yellow
in a bath maintained at -20 °C, and the solution was stirred
for 96 h. The reaction mixture was quenched with a small
amount of saturated NH4Cl aqueous solution. The mixture was
extracted with CH2Cl2 three times, and the combined organic
layer was dried over MgSO4. After evaporation, the crude
product was purified by preparative TLC on silica gel (eluent
3/1 hexane/EtOAc) to give the alkylated product in pure form.
Yield: 128 mg (325 µmol, 99%). The enantiomeric purity was
determined to be 99% ee by HPLC analysis with a chiral
stationary phase column, Chiralcel OD-H (98/2 hexane/2-
propanol).
1
solid. H NMR (CDCl3): δ 0.56 (q, J ) 12.2 Hz, 1H), 0.64 (d,
J ) 6.5 Hz, 3H), 0.71-0.75 (m, 8H), 0.85-0.99 (m, 10H), 1.12-
1.22 (m, 4H), 1.43 (br, 1H), 1.62-1.75 (m, 7H), 1.82-1.97 (m,
3H), 2.22 (q, J ) 11.8 Hz, 1H), 2.65-2.72 (m, 1H), 2.99 (dd, J
) 16.1 and 10.3 Hz, 1H), 3.25 (s, 1H), 3.89 (s, 1H), 4.10 (s,
1H), 4.49 (s, 1H), 4,84 (br, 1H), 4.88 (br, 1H), 7.41 (br, 3H),
7.47-7.51 (m, 2H), 7.60-7.66 (m, 3H), 8.22-8.25 (m, 2H). 31P-
2
{1H} NMR (CDCl3): δ 10.1 (1J Pt-PPh ) 4183 Hz, J PP ) 15.5
2
2
Hz), 49.4 (1J Pt-phospholyl ) 3583 Hz, J PP ) 15.5 Hz). [R]20
-43.6 (c 0.570, CHCl3). Mp: >300 °C. Anal. Calcd for C42H56
Cl2FeP2Pt: C, 53.40; H, 5.98. Found: C, 52.95; H, 5.98.
)
D
Ack n ow led gm en t. This work was supported by the
“Research for the Future” Program (the J apan Society
for the Promotion of Science), a Grant-in-Aid for Scien-
tific Research (the Ministry of Education of J apan), and
the Mitsubishi Chemical Corporation Fund (to M.O.).
K.Y. thanks the J apan Society for the Promotion of
Science for the award of a fellowship for graduate
students.
-
P d -Ca ta lyzed Allylic Alk yla tion s. A typical procedure is
given for the reaction of entry 7 in Table 1. To a mixture of
[PdCl(π-C3H5)]2 (4.3 mg, 11.7 µmol), (-)-5 (11.9 mg, 17.5 µmol),
KOAc (2.0 mg, 20 µmol), and rac-1,3-diphenyl-2-propenyl
acetate (82.2 mg, 326 µmol) in CH2Cl2 (2.0 mL) was added a
solution of N,O-bis(trimethylsilyl)acetamide (260 µL, 1.05
mmol), and dimethyl malonate (120 µL, 1.05 mmol) in CH2-
Cl2 (1.7 mL) at -78 °C under nitrogen. The flask was immersed
OM010440E