One-pot synthesis of a novel C1-symmetric diphosphine from 1,3-cyclic sulfate. Asymmetric hydroformylation of styrene

Article abstract of DOI:10.1016/S0957-4166(01)00498-0

Preparation of a novel homochiral diphosphine with C₁-symmetry from the cyclic sulfate of (2R.4R)-2.4-pentanediol is reported. Reaction of a lithium phosphide salt with the cyclic sulfate affords a γ-phospholylsulfate which can be converted to

Full text of DOI:10.1016/S0957-4166(01)00498-0

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 12 (2001) 2867–2873
One-pot synthesis of a novel C1-symmetric diphosphine from
1,3-cyclic sulfate. Asymmetric hydroformylation of styrene
b
a
b
Csaba Hegedu¨s, Jo´zsef Madara´sz, Henrik Gulya´s, Aron Szo¨llo3
syc and Jo´zsef Bakosa,*
´
aDepartment of Organic Chemistry, University of Veszpre´m, H-8201 Veszpre´m, PO Box 158, Hungary
bResearch Group for Petrochemistry, Hungarian Academy of Science, H-8201 Veszpre´m, PO Box 158, Hungary
cDepartment of General and Analytical Chemistry, Technical University of Budapest, H-1521 Budapest, Hungary
Received 19 October 2001; accepted 2 November 2001
Abstract—Preparation of a novel homochiral diphosphine with C1-symmetry from the cyclic sulfate of (2R,4R)-2,4-pentanediol is
reported. Reaction of a lithium phosphide salt with the cyclic sulfate affords a g-phospholylsulfate which can be converted to a
diphosphine ligand on treatment with a second equivalent of lithium phosphide. Using this ligand in the platinum-catalyzed
asymmetric hydroformylation of styrene, outstanding levels of regio- and enantiocontrol were obtained (89/11 iso/n isomeric ratio
and 89% e.e.). The results are compared with those obtained with the analogous ligands (bdpp and bdbpp) having C2-symmetry.
The novel unsymmetric ligand possessed the advantageous catalytic features of the C2-symmetric parent ligands. © 2001 Elsevier
Science Ltd. All rights reserved.
1. Introduction
fully controlled as hydroformylation can be accompa-
nied by hydrogenation. The platinum systems are
therefore not always the catalysts of choice for asym-
metric hydroformylation. However, it has been found
that if the diphenylphosphino groups of diop 1 or bdpp
2 are exchanged for dibenzophosphole (DBP) groups (4
and 5), the regioselectivity is reversed and branched,
chiral product is predominantly formed (Scheme 1).4,6
Asymmetric hydroformylation is an attractive catalytic
approach to the synthesis of a large number of
homochiral compounds.1 The recently developed Rh-
based asymmetric hydroformylation catalysts, which
utilize chiral bidentate phosphine–phosphite2 or diphos-
phite ligands3 are generally superior to Pt–Sn–chiral
phosphine systems in terms of regioselectivity.4 Chiral
ligands based on the 2,4-pentane-2,4-diyl skeleton
found widespread application in asymmetric synthesis.
The most well-known derivatives of this type are
For example, (S,S)-bdpp 2 readily provides good enan-
tioselectivity, although with the expected moderate
branched aldehyde selectivity (28% with 17% e.e. (R) at
100°C and 42% with 64.5% e.e. (S) at 70°C).10 By the
use of (S,S)-bdbpp 5, the regioselectivity for the
branched aldehyde is increased markedly; however, the
enantioselectivity is dramatically decreased (79.3% with
11.6% e.e. (S) at 100°C and 86% with 18.8% e.e. (S)
around 40°C).6 Ligand 6 also gives better selectivities
than its diphenylphosphino-analogue 3.4 As a result of
these findings, phosphole derivatives of several other
chiral ligands have been prepared.1 Many of the cata-
lysts derived from these ligands also show improved
selectivity with respect to the branched aldehyde, when
compared to the diphenylphosphino- counterparts, but
none simultaneously gives high enantioselectivity with-
out side reactions.
(2S,4S)-2,4-bis(diphenylphosphino)pentane5
((S,S)-
bdpp, 2), (2S,4S)-pentane-2,4-diyl-bis(5H-dibenzo[b]-
phosphindole6 ((S,S)-bdbpp, 5), tetra-para-amino-
functionalized [(S,S)-bdpp-(p-NMe2)4],7 3-benzyl-bdpp8
or different diphosphite diastereomers, which contain
stereogenic centers in the backbone as well as in the
terminal groups.9 As part of our research aimed at the
synthesis and use of new chiral diphosphines, we have
described the catalytic performance of Pt–diphosphine/
SnCl2 complexes for asymmetric hydroformylation of
styrene in recent communications.6,10
The regioselectivity is generally in favor of the linear
aldehyde, and the reaction conditions have to be care-
In the light of these findings we reasoned that by the
exchange of a diphenylphosphino group for a dibenzo-
* Corresponding author. E-mail: bakos@almos.vein.hu
0957-4166/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(01)00498-0

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C. Hegedu¨s et al. / Tetrahedron: Asymmetry 12 (2001) 2867–2873
Scheme 1.
phosphole unit in bdpp, the regioselectivity and enan-
tioselectivity of the catalytic system could be improved.
In order to prove the hypothesis we have developed a
new methodology for the synthesis of chiral 1,3-diter-
tiary phosphines with two stereogenic centers and
investigated the catalytic performance of the new phos-
phine–phosphole 9 in the asymmetric hydroformylation
of styrene catalyzed by Pt and Rh complexes.
ester reacts smoothly with 1 equiv. of Li–DBP to give
the ‘sulfated’ phosphole followed by the addition of a
second equiv. of LiPPh2 (Scheme 2).
Although it is known that an ionic sulfate group can
act as a leaving group,15 it was clear that its anionic
nature renders it kinetically much less reactive than a
ROSO2OR% group. The negative charge decreases the
polarity of CꢀO bond, and the electrostatic repulsion
between the leaving group and an attacking anionic
group also increases the activation energy of the substi-
tution. Accordingly, (i) the second substitution, the
replacement of the –OSO3Li occurred at 60°C and (ii)
in an independent experiment the sulfated phosphole
could be isolated and fully characterized. Both nucle-
ophilic attacks occur with complete inversion at the
stereogenic centers to give a new homochiral phos-
phine–phosphole. This was proved by the synthesis of
bdpp following the same methodology. A comparison
of the configuration and specific rotation value of the
product obtained from cyclic sulfate 7 with that of the
known configuration and specific rotation of
diastereomerically pure bdpp proves the complete enan-
tioselectivity and diastereoselectivity of the double sub-
stitution. This is also supported by the presence of only
two singlets in the 31P{1H} NMR spectrum of the
product 9. Recently, Werner et al. reported the synthe-
sis of related enantiopure 1,2-bis(phosphanyl)ethane.16
The simplest and most attractive way to prepare chiral
ditertiary phosphines with C1-symmetry would be via
direct selective mono-substitution of readily available
ditosylates or similar electrophiles. However, the direct
nucleophilic substitution of ditosylates with conven-
tional nucleophiles is usually non-selective, leading to
mixtures of unreacted ditosylate and mono- and diter-
tiary phosphines.11
2. Results and discussion
2.1. Synthesis of the ligand
The availability of homochiral diol from 2,4-pentane-
dione,12 coupled with the highly electrophilic behavior
of the derived cyclic sulfates,13 has enabled us to
develop an efficient route to a new ditertiary phosphine
9 having C1-symmetry. The cyclic sulfate 7 of (2R,4R)-
2,4-pentanediol was obtained by a simple one-pot reac-
tion following the procedure developed for 1,2-cyclic
sulfates by Gao and Sharpless.14 The synthesis involves
the treatment of diols with thionyl chloride followed by
ruthenium-catalyzed oxidation. In this way, sulfate 7
could be obtained in high yield (82%).13 The sulfate
2.2. Solution structure of the platinum complexes
The [PtCl2(9)] complex was prepared from the appro-
priate amount of [PtCl2(PhCN)2] and 1 equiv. of the
enantiopure ligand 9 in refluxing CHCl3. The reaction
1
resulted in a platinum complex possessing J(195Pt,31P)
Scheme 2. Reagent and conditions: (i) Li–DBP, THF, 0°C and then at room temperature 2 h; (ii) LiPPh2, 60°C, 5 h (47% over
two steps).

C. Hegedu¨s et al. / Tetrahedron: Asymmetry 12 (2001) 2867–2873
2869
coupling constants of 3224 Hz at 3.11 ppm and 3384 Hz
at 10.10 ppm in the 31P{1H} NMR spectrum. These
coupling constants are indicative for P–Pt–Cl trans
arrangement and have been obtained for a number of
cis-[PtCl2(diphosphine)]-type complexes 10.17 In the case
of bdpp and bdbpp the corresponding coupling constants
are 3413 Hz (l 7.21 ppm) and 3258 Hz (l 8.30 ppm),
respectively. From the platinum–phosphorus coupling
constants it can be concluded that the coupling constant
at 3.11 ppm belongs to the dibenzophosphole and that
with a value of 3384 Hz at 10.10 ppm to the
diphenylphosphine unit. It is interesting to note that
ligand 5 initially gives a dimeric complex containing
trans-bridging diphosphines, which rearranges to cis-
[PtCl2(5)] on stirring for a further 3 days.6
are diagnostic values to differentiate between cis- and
trans-coordination of the ligands.
At ambient temperature four signals were observed in the
31P{1H} NMR spectrum for the [Pt(SnCl3)Cl(9)] complex
containing the bdpp analogue with C1-symmetry
(Scheme 4). Based on the mutual phosphorus–phospho-
rus coupling 2J(P,P), both the doublets at 11.95 and 12.85
ppm (complex 12), furthermore the doublets at 17.95 and
−6.65 ppm (complex 11) are assigned to cis isomers.18 The
relatively large platinum–phosphorus coupling constant
and the relatively small tin–phosphorus coupling con-
2
stants (2Javg(Sn,P), the averaged value of Jcis(117Sn,31P)
2
and Jcis(119Sn,31P)) of 229 and 165 Hz of the signals at
−6.65 and 11.95 ppm, respectively, are indicative of
phosphine positioned trans to chlorine and cis to the tin
and hence, are again indicative of cis complexes. From
the chemical shifts and the platinum–phosphorus cou-
pling constants it can be concluded that the doublets at
12.85 and 17.09 ppm belong to the phosphine positioned
trans to tin, and those at 11.95 and −6.65 ppm to the
phosphine positioned trans to chlorine. According to the
relative intensities of the corresponding signals in the
NMR spectrum, the diastereomeric ratio of the cis
complexes [Pt(SnCl3)Cl(9)] (11 and 12) is 1:1. This 1:1
ratio of the diastereomers (11 and 12) might reflect the
The platinum catalytic precursor [Pt(SnCl3)Cl(9)] was
prepared in CH2Cl2 at room temperature from the
[PtCl2(9)] complex with an equimolar amount of anhy-
drous tin(II) chloride (Scheme 3). The [Pt(SnCl3)Cl(9)]
complex was investigated using 31P{1H} NMR spec-
troscopy to elucidate the coordination mode of the
ligand. For comparison the platinum/tin complexes of 2
and 5 having C2-symmetry were included (Table 1). The
platinum–phosphorus coupling constants (1J(Pt,P)) of
the square-planar [Pt(SnCl3)Cl(diphosphine)] complexes
Scheme 3.
Table 1. 31P{1H} NMR data for the platinum complexes of [Pt(SnCl3)Cl(diphosphine)]a obtained in the
[PtCl2(diphosphine)]+SnCl2 reaction
P (trans to SnCl3)
2J(Sn,P)b (Hz)
P (cis to SnCl3)
Ligand
l (ppm)
1J(Pt,P) (Hz)
2J(P,P) (Hz)
l (ppm)
1J(Pt,P) (Hz)
2J(Sn,P)c (Hz)
9d
9e
17.09
12.85
2798
2519
4031, 3873
4085, 3904
23.1
26.2
−6.65
11.95
3091
3320
229
165
a [Pt(SnCl3)Cl(2)]:10 l 13.79 ppm (trans to SnCl3), 1J(Pt,P) 2759 Hz, 2J(Sn,P) 4090 Hz, 2J(P,P) 23.7 Hz, l 7.43 ppm (cis to SnCl3), 1J(Pt,P) 3348
2
1
2
1
Hz, J(Sn,P) 187 Hz; [Pt(SnCl3)Cl(5)]:6 l 15.6 (trans to SnCl3), J(Pt,P) 2556 Hz, J(P,P) 20.8 Hz, l −0.70 ppm (cis to SnCl3), J(Pt,P) 3120 Hz.
b 2
2
J
J
(
117Sn,31P); Jtrans
(
(
119Sn,31P).
119Sn,31P) coincide.
trans
c 2
2
(
117Sn,31P) and Jcis
cis
d Complex 11.
e Complex 12.

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C. Hegedu¨s et al. / Tetrahedron: Asymmetry 12 (2001) 2867–2873
Scheme 4. 31P{1H} NMR of the solution of [9-Pt(SnCl3)Cl]. Complex 11 (ꢀ): A. Complex 12 (ꢁ): B.
relative trans influences of the non-equivalent phos-
phorus atoms (Scheme 3).
of a diphenylphosphino group for a dibenzophospholyl
group in bdpp 2 was found to have a favorable effect
on the catalytic performance of the resulting C1 sym-
metric ligand. A remarkable increase in regio- and
enantioselectivities from 47/53 with 20% e.e. up to
79/21 with 86% e.e. (entries 1–4) was seen on lowering
the reaction temperature from 100 to 24°C. It is inter-
esting to note that with [Pt(Cl)(SnCl3)(S,S)(2)] at low
temperatures (20–40°C) (S)-2-phenylpropanal predomi-
nates up to 85% e.e., while at temperature above 100°C
2.3. Hydroformylation of styrene
The hydroformylation reactions were performed under
classical conditions shown in Table 2. The in situ
preparation of the catalyst by simply mixing
[PtCl2(PhCN)2] or [Rh(CO)2(acac)] in toluene with the
ligand was revealed to be advantageous. The exchange
Table 2. Asymmetric hydroformylation of styrene with chiral Pt and Rh diphosphine catalystsa
Entry
T (°C)
Time (h)
Conv. (%)b
TOFc
RCHO (%)b,d
(b/n)b
E.e. of 13 (%)e
1
2
3
4
100
70
40
24
24
24
70
70
40
8
8
100
64
65
48
70
43
74
90
57
207
139
19
6
29
27
–
83
87
94
97
94
84
93
73
100
47/53
56/44
67/33
79/21
85/15
89/11
36/74
86/14
92/8
20 (S)
43 (S)
69 (S)
86 (S)
89 (S)
88 (S)
26 (S)
19 (S)
47 (R)
66
165
45
27
9
5f
6g
7h
8i
9j
27
46
49
24
a Reactions conditions: H2 and CO (1:1) at 70 atm initial total pressure. Catalyst: 0.05 mmol [Pt(PhCN)2Cl2], 0.05 mmol SnCl2 and 0.055 mmol
chiral ligand in 35 mL toluene, substrate/catalyst molar ratio is 2000.
b For determination see Section 4.
c Amount of RCHO 13+14 in mol (mol Rh)−1 h−1 determined at the end of the reaction time.
d Aldehydes/(aldehydes+ethylbenzene).
e Determined by GC analysis of the distilled product (b-DEX 225, 30 m, id 0.25 mm, 0.25 mm film).
f H2 and CO (2:1) at 195 atm initial total pressure.
g (9:1) at 155 atm initial total pressure.
h Data from Ref. 10. (S,S)-bdpp 2 was used as a ligand.
i Data from Ref. 6. (S,S)-bdbpp 5 was used as a ligand.
j Reactions conditions: H2 and CO (1:1) at 30 atm initial total pressure. Catalyst: 0.0125 mmol [Rh(CO)2(acac)] and 0.075 mmol chiral ligand in
7 mL toluene, substrate/catalyst molar ratio is 2000.

C. Hegedu¨s et al. / Tetrahedron: Asymmetry 12 (2001) 2867–2873
2871
4. Experimental
4.1. General techniques
the (R)-enantiomer predominates with a maximum of
28% e.e.10 In the case of 5 the temperature dependence
is less significant.6 Furthermore, ligand 9 give chemose-
lectivities similar to those obtained with ligand 5
(entries 2 and 7) and both ligands give higher chemose-
lectivities than ligand 2 (entry 8).
All reactions were carried out in oven-dried glasswork
using Schlenk techniques under an atmosphere of
argon. Infrared (IR) spectra were recorded on a
Specord IR-75A spectrometer. 31P{1H} NMR spectra
were recorded on either a VARIAN UNITY 300 spec-
trometer operating at 121.42 MHz or a Bruker DRX-
500 spectrometer operating at 202.45 MHz. Chemical
shifts are relative to external 85% H3PO4 with
Comparing entries 4–6 shows that regio- and enantio-
selectivities are slightly increased by increasing the par-
tial pressure of H2 (iso/n isomeric ratio=89/11 with
88% e.e.) and the activities were best at high PH /PCO
ratios. This is in line with detailed mechanistic st2udies
into platinum-catalyzed hydroformylation with diter-
tiary phosphines, which showed that the rate-determin-
ing step is the hydrogenolysis of the acyl–platinum
complex.19
downfield values reported as positive. H and 13C{1H}
1
NMR spectra were recorded at 300.15 and at 75.43
MHz, respectively, on a VARIAN UNITY 300 spec-
trometer or at 500.13 and 125.76 MHz, respectively, on
a Bruker DRX-500 spectrometer. Chemical shifts are
relative to tetramethylsilane as external reference or
calibrated against solvent resonances. Optical rotations
were measured on Schmidt Haensch 21245 polarimeter
using 10 cm cells. Gas chromatographic analyses were
performed on a Hewlett–Packard 5830A gas chro-
matograph equipped with a flame-ionization detector
and a SPB-1 column (30 m, film thickness 0.1 mm,
carrier gas 2 mL/min). Mass spectrometric measure-
ment was performed using a PE SCIEX API 2000 triple
quadrupole instrument. Electrospray ionization was
used and negative ion was detected.
With the platinum precursor, anhydrous SnCl2 was
used as co-catalyst, which is essential for catalytic activ-
ity. SnCl2 may act as a Lewis acid or as a ligand
(SnCl3), directly bonded to platinum,19 or as a counter
anion (SnCl3).18 Theoretical studies on the olefin inser-
tion suggest that the major role of the SnCl3 ligand is to
stabilize the pentacoordinated intermediates as well as
to weaken the PtꢀH bond trans to it.20 Recent
theoretical21 and spectroscopic studies22 suggest that the
presence a single catalytically active species in solution
is the key to controlling efficient chirality transfer.
Based on the coordination chemistry and catalytic
results of the new ligand it can be concluded that the
selective insertion of tin(II) chloride into the PtꢀCl
bond is not a prerequisite for achieving high regioselec-
tivity and enantioselectivity in the platinum/tin-cata-
lyzed asymmetric hydroformylation.
4.2. Materials and methods
Tetrahydrofuran (THF), diethyl ether (Et2O), toluene
and hexane were distilled from sodium benzophenone
ketyl under argon. Methylene chloride (CH2Cl2) was
distilled from CaH2 and methanol (MeOH) from
Mg(OMe)2 under argon. Water (H2O) was distilled
twice under argon. Deuterated water (D2O) was deoxy-
genated by bubbling with argon for 10 min. Deuterated
chloroform and methylene chloride (CDCl3 and
CD2Cl2) were deoxygenated by distillation under argon.
Enantiomerically pure pentane-2,4-diol is conveniently
prepared by asymmetric hydrogenation of 2,4-pentane-
dione over Raney nickel catalyst modified with the
corresponding enantiomer of tartaric acid and NaBr
(TA–NaBr–MRNi).12 Li–DBP was prepared according
to the literature procedure.6 All the other chemicals
were commercial products and were used as received
without further purification.
It has recently been reported that for the rhodium
catalyst containing the chiral ligand 2, the enantioselec-
tivity heavily depends on the ligand to metal ratio.23
Thus, the highest enantioselectivity (54%) for 13 at a
2:Rh ratio of 6:1 was obtained. At a similar ratio,
ligand 9 induced slightly lower enantioselectivity (entry
9, e.e.=47%) and regioselectivity (92%).
3. Conclusions
We have developed a highly practical one-pot synthesis
of an unsymmetrical 1,3-bis(phosphanyl)propane from
1,3-cyclic sulfate. This methodology is remarkable
because of its easy synthetic approach, short reaction
time and high efficiency. Moreover, the strategy can be
extended to related phosphines. In the presence of the
novel chiral phosphine–phosphole, the platinum-cata-
lyzed asymmetric hydroformylation of styrene results in
outstanding levels of regio- and enantiocontrol (89/11
iso/n isomeric ratio and 89% e.e.). These results are
similar to those obtained with the most efficient diphos-
phine-based catalytic systems previously reported1 and
are in agreement with the concept that C1-symmetric
diphosphines may provide better results than C2-sym-
metric diphosphines.24
4.3. (2R,4S)-4-(Dibenzophospholyl)-pent-2-yl-sulfate
lithium salt 8
A solution of (4R,6R)-4,6-dimethyl-2,2-dioxide-1,3,2-
dioxathiane 7 (610 mg, 3.7 mmol) in dry THF (4 mL)
was added at 0°C to a solution of LiPAr2·dioxane
adduct (1.2 g, 4.3 mmol) in dry THF (15 mL), mean-
while the bright red color of the phosphide solution
turned light brown. The mixture was stirred at ambient
temperature for 1 h. The THF was removed under
reduced pressure, then deoxygenated water (30 mL) and
Et2O (20 mL) were added. The aqueous phase was
separated and washed with Et2O (20 mL) again. The
remained ether was removed from the aqueous solution

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C. Hegedu¨s et al. / Tetrahedron: Asymmetry 12 (2001) 2867–2873
1
(d, J(P,C)=7.5 Hz), 144.39 (s), 144.71 (s). Anal. calcd
for C29H28P2: C 79.45, H 6.39%. Found: C 79.38, H
6.43%.
in vacuum. The pH of the solution was adjusted to
ꢀ6.8 using diluted H2SO4 solution. The water was
removed under reduced pressure, then CH2Cl2 (20 mL)
was added. Li2SO4 was removed by filtration. Evapora-
tion of the solvent under vacuum yielded the product as
a white powder (900 mg, 68%). [h]D22=+39.5 (c=4.1,
H2O). 31P{1H} NMR (202.45 MHz, D2O): l 2.13 ppm.
4.5. (2S,4S)-2,4-Bis(diphenylphosphino)pentane 2
A solution of (4R,6R)-4,6-dimethyl-2,2-dioxide-1,3,2-
dioxathiane (7) (1.5 g, 8.8 mmol) in dry THF (15 mL)
was added dropwise at 0°C to
3
1H NMR (500 MHz, D2O): l 0.47 (dd, J(P,H)=13.0
Hz, 3J(H,H)=7.0 Hz, 3H, CH3CHPAr2), 0.84 (d,
3J(H,H)=6.0 Hz, 3H, CH3CHOSO3Li), 0.84 (over-
lapped by the signal of CH3, 1H, diastereotopic CH2),
1.33 (m, 1H, diastereotopic CH2), 2.02 (m, 1H,
CHPAr2), 4.33 (m, 1H, CHOSO3Li), 6.81–7.36 (m, 8H,
aromatic protons). 13C{1H} NMR (125.76 MHz, D2O):
a solution of
LiPPh2·dioxane (2.4 g, 8.8 mmol) in dry THF (20 mL),
meanwhile the bright red color turned light brown. The
mixture was stirred at ambient temperature for 2 h.
LiPPh2·dioxane adduct (2.5 g, 8.8 mmol) in THF (15
mL) was added and the reaction mixture was heated for
5 h at 60°C. The THF was removed under reduced
pressure, then Et2O (30 mL) and deoxygenated water
(15 mL) were added. The organic phase was separated
and the aqueous phase was washed with Et2O (2×10
mL). The organic phase was filtered through a pad of
MgSO4–Al2O3–MgSO4. The solvent was removed under
reduced pressure. The remained dense liquid was crys-
tallized from hot MeOH. Yield: 1.8 g (58%). mp 79–
80°C; [h]D20=−123.5 (c=4.1, CHCl3).
2
l 15.45 (d, J(P,C)=6.3 Hz, CH3CHPAr2), 20.95 (s,
CH3CHOSO3Li), 28.88 (d, 1J(P,C)=17.0 Hz,
2
CHPAr2), 40.07 (d, J(P,C)=7.7 Hz, CH2), 75.67 (d,
3J(P,C)=10.6 Hz, CHOSO3Li), 121.52 (s), 127.57
(pseudo t, Dl:3J(P,C):8.8 Hz), 128.77 (s), 128.91 (s),
2
2
130.58 (d, J(P,C)=20.1 Hz), 130.81 (d, J(P,C)=21.4
1
1
Hz), 140.05 (d, J(P,C)=6.4 Hz), 140.63 (d, J(P,C)=
5.0 Hz), 144.25 (s), 144.35 (s). MS (ESI, m/z) 349
[M−Li+].
4.6. Preparation of cis-[PtCl2(9)]
4.4. (2S,4S)-2-(Dibenzophospholyl)-4-(diphenylphos-
phino)pentane 9
CHCl3 (10 mL) was added to
[PtCl2(PhCN)2] (387 mg, 0.82 mmol) and (2S,4S)-2-
(dibenzophospholyl)-4-(diphenylphosphino)pentane
a
mixture of
A solution of (4R,6R)-4,6-dimethyl-2,2-dioxide-1,3,2-
dioxathiane 7 (1.5 g, 8.8 mmol) in dry THF (15 mL)
was added to a solution of Li–DBP·dioxane adduct (2.4
g, 8.8 mmol) in THF (20 mL) at 0°C, wherein the
bright red color turned light brown. The mixture was
stirred at ambient temperature for 2 h. LiPPh2·dioxane
adduct (2.5 g, 8.8 mmol) in THF (15 mL) was added
and the reaction mixture was heated for 5 h at 60°C.
The THF was removed under reduced pressure, then
Et2O (30 mL) and deoxygenated water (15 mL) were
added. The organic phase was separated and the
aqueous phase was washed with Et2O (2×10 mL). The
organic phase was filtered through a pad of MgSO4–
Al2O3–MgSO4. The solvent was removed under reduced
pressure. The remaining dense liquid was crystallized
from hot MeOH. Yield: 1.8 g (47%) mp 107–109°C;
[h]2D0=−67.3 (c=4.1, CHCl3). 31P{1H} NMR (121.42
9
(359 mg, 0.82 mmol) with stirring. The formed yellow
solution was refluxed for 1 h, upon which the solution
went lighter in color. After cooling hexane (20 mL) was
added and the formed precipitate was filtered. The solid
was washed with hexane (10 mL) and dried under
vacuo, yielding product as a white powder (575 mg).
31P{1H} NMR (202.45 MHz, CDCl3): l=3.11 (d,
2J(P,P)=24.8 Hz, 1J(P,Pt)=3224.0 Hz), 10.10 (d,
2J(P,P)=24.8 Hz, 1J(P,Pt)=3384.0 Hz). 1H NMR
3
(500.13 MHz, CDCl3): l=0.31 (dd, J(P,H)=14.9 Hz,
3J(H,H)=6.7 Hz, 3H; CH3), 1.35 (dd, J(P,H)=16.3
3
3
Hz, J(H,H)=7.0 Hz, 3H; CH3), 2.23 (m, 2H; CH2),
2.46 (m, 1H; CH), 3.00 (m, 1H; CH), 6.5–8.3 (m, 18H;
aromatic protons). 195Pt NMR (CDCl3, Na2PtCl6): l=
−4647.70 (dd, 1J(P,Pt)=3224.0 Hz, 1J(P,Pt)=3384.0
Hz).
1
MHz, CDCl3): l=0.64 (s), 1.05 (s). H NMR (500.13
4.7. Preparation of cis-[PtCl(SnCl3)(9)]
MHz, CDCl3): l=0.68 (dd, 3J(P,H)=12.5 Hz,
3
3J(H,H)=7.0 Hz, 3H; CH3), 0.84 (dd, J(P,H)=15.2
CH2Cl2 (25 mL) was added to a mixture of cis-
[PtCl2(9)] (150 mg, 0.21 mmol) and anhydrous SnCl2
(40 mg 0.21 mmol) with stirring. After 4 h, the yellow
solution was filtered and the filtrate was concentrated
under reduced pressure giving cis-[9-PtCl(SnCl3)] as an
orange solid. Yield: 178 mg (95%) 31P{1H} NMR
(121.42 MHz, CD2Cl2): l=11.95, d, 12.85, d,
3
Hz, J(H,H)=7.0 Hz, 3H; CH3), 1.37 (m, 1H; CH2),
1.44 (m, 1H; CH2), 1.95 (m, 1H; CH), 2.34 (m, 1H;
CH), 7.1–7.8 (m, 18H; aromatic protons). 13C{1H}
2
NMR (125.76 MHz, CDCl3): l=14.97 (d, J(P,C)=7.4
2
Hz, CH3), 15.69 (d, J(P,C)=15.7 Hz, CH3), 27.49 (t,
1
1J(P,C)ꢀ3J(P,C)ꢀ9.6 Hz, CH), 30.95 (dd, J(P,C)=
17.1 Hz, 3J(P,C)=11.9 Hz, CH), 36.85 (t, 2J(P,C)ꢀ
2J(P,C)ꢀ15.7 Hz, CH2), 121.33 (s), 121.36 (s), 127.10
(d, 3J(P,C)=7.7 Hz), 127.24 (d, 3J(P,C)=7.4 Hz),
128.56 (d, 3J(P,C)=10.5 Hz), 128.55 (s), 128.58 (s),
2
(1J(P,Pt)=3320.6 Hz, Jcis(P,117,119Sn)=165.2 Hz (Cl
trans to diphenylphosphino group), satellites,
1J(P,Pt)=2519.4 Hz, 2Jtrans(P,117Sn)=3904.1 Hz,
2Jtrans(P,119Sn)=4084.7 Hz (SnCl3 trans to diben-
4
2
2
129.07 (d, J(P,C)=3.2 Hz), 130.35 (d, J(P,C)=21.1
zophospholyl group), satellites, J(P,P)=26.2 Hz), l=
2
2
(1J(P,Pt)=3091.0
Hz,
Hz), 130.63 (d, J(P,C)=20.8 Hz), 135.83 (d, J(P,C)=
19.0 Hz), 136.29 (d, 1J(P,C)=9.3 Hz), 136.63 (d,
−6.65,
d,
17.09,
d,
2Jcis(P,117,119Sn)=229.0 Hz (Cl trans to dibenzophos-
pholyl group), satellites, 1J(P,Pt)=2798.8 Hz,
1J(P,C)=9.3 Hz), 140.85 (d, J(P,C)=7.5 Hz), 141.27
1

C. Hegedu¨s et al. / Tetrahedron: Asymmetry 12 (2001) 2867–2873
2873
2
2Jtrans(P,117Sn)=3873.0 Hz, Jtrans(P,119Sn)=4031.0 Hz
Asymmetry 1993, 4, 1625; (c) Buisman, G. J. H.; Martin,
M. E.; Vos, E. J.; Klootwijk, A.; Kamer, P. C. J.; van
Leeuwen,P.W.N.M.Tetrahedron:Asymmetry1995,7,719.
4. (a) Parenillo, G.; Stille, J. K. J. Org. Chem. 1986, 51, 4189;
(b) Stille, J. K.; Su, H.; Brechot, P.; Parenillo, G.; Hegedus,
L. S. Organometallics 1991, 10, 1183; (c) Consiglio, G.;
Nefkens, S. C. A.; Borer, A. Organometallics 1991, 10, 2046;
(d) Scrivanti, A.; Zeggio, S.; Beghetto, V.; Matteoli, U. J.
Mol. Catal. 1995, 101, 217.
(SnCl3 trans to diphenylphosphino group), satellites,
2J(P,P)=23.1 Hz). 195Pt NMR (CD2Cl2, Na2PtCl6):
l=−4891.37 (dd, 1J(P,Pt)=3091.0 Hz, 1J(P,Pt)= 2798.8
Hz), −4909.6 (dd, 1J(P,Pt)=3320.6 Hz, 1J(P,Pt)=2519.4
Hz).
4.8. Catalytic experiments
In a typical experiment, [Pt(PhCN)2Cl2] (0.05 mmol),
the ligand (0.055 mmol), SnCl2 (0.05 mmol), toluene (35
mL), styrene (100 mmol) and decane (5 mmol used as
an internal standard) were placed in a Schlenk-tube
under argon. The stainless-steel autoclave (100 mL) was
filled with this solution and then purged with syn gas
[CO–H2 (1:1)] and pressurized to the appropriate initial
pressure with this gas mixture. At the end of the
reaction the autoclave was cooled, and depressurized.
The reaction mixture was directly vacuum distilled to
remove the catalyst. The reaction mixture and the
distilled products were analyzed by gas chromatogra-
phy. The enantiomeric excess of the aldehyde was
determined by GC analysis of the distilled product on a
Hewlett–Packard HP 4890 gas chromatograph
equipped with a split/splitless injector and a b-DEX 225
column (30 m, internal diameter 0.25 mm, film thick-
ness 0.25 mm, carrier gas: 100 kPa nitrogen, F.I.D.
detector; the retention times of the enantiomers are 30.4
min (R), 31.4 min (S)). The configuration of the pre-
vailing enantiomer in the product was determined by
the sign of optical rotation of the corresponding alde-
hyde. Conversions and composition of the reaction
mixture (13:14:15 branched:linear:hydrogenated) were
determined by GC (SPB-1) using decane as an internal
standard.
5. (a) Mac Neil, P. A.; Roberts, N. K.; Bosnich, B. J. Am.
Chem. Soc. 1981, 103, 2273; (b) Bakos, J.; To´th, I.; Heil,
B.; Marko´, L. J. Organomet. Chem. 1985, 279, 23.
6. To´th, I.; Elseiver, C. J.; de Vries, J. G.; Bakos, J.; Smeets,
W. J. J.; Spek, A. J. Organomet. Chem. 1997, 540, 15.
7. To´th, I.; Guo, I.; Hanson, B. E. Organometallics 1993, 12,
848.
8. Bianchini, C.; Barbaro, P.; Scapacci, G.; Zanobini, F.
Organometallics 2000, 19, 2450.
9. (a) Billig, E.; Abatjoglou, A. G.; Bryant, D. R. US Pat.
4,769,498 (to Union Carbide) 1988; (b) Babin, J. E.;
Whiteker G. T. W.O. US Pat. 911 518 (to Union Carbide)
1992.
10. (a) Kolla´r, L.; Bakos, J.; To´th, I.; Heil, B. J. Organomet.
Chem. 1988, 350, 277; (b) Kolla´r, L.; Ke´gl, T.; Bakos, J.
J. Organomet. Chem. 1993, 453, 155.
11. Morimoto, T.; Chiba, M.; Achiwa, K. Tetrahedron Lett.
1988, 29, 4755.
12. (a) Ito, K.; Harada, T.; Tai, A.; Izumi, Y. Chem. Lett. 1979,
1049; (b) Ito, K.; Harada, T.; Tai, A. Bull. Chem. Soc. Jpn.
1980, 53, 3367.
´
13. (a) Gulya´s, H.; Arva, P.; Bakos, J. Chem. Commun. 1997,
1, 2385; (b) Gulya´s, H.; Dobo´, A.; Bakos, J. Can. J. Chem.
2001, 73, 1040.
14. Gao, Y.; Sharpless, K. B. J. Am. Chem. Soc. 1988, 110, 7538.
15. Burk, M. J.; Pizzano, A.; Martin, J. A.; Liable-Sands, L.
M.; Rheingold, A. L. Organometallics 2000, 19, 250.
16. Fries, G.; Wolf, J.; Pfeiffer, M.; Stalke, D.; Werner, H.
Angew. Chem., Int. Ed. Engl. 2000, 39, 564.
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Acknowledgements
Financial support from the Hungarian National Science
Foundation (OTKA-T016269) is gratefully acknowl-
´
edged. We are grateful to Mr. Be´la Edes for skilful
18. To´th, I.; Ke´gl, T.; Elsevier, C. J.; Kolla´r, L. Inorg. Chem.
1994, 33, 5704 and references cited therein.
technical assistance.
19. (a) Scrivanti, A.; Botteghi, C.; Toniolo, L.; Berton, A. J.
Organomet. Chem. 1988, 344, 261; (b) Scrivanti, A.; Berton,
A.; Toniolo, L.; Botteghi, C. J. Organomet. Chem. 1986,
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