Novel phosphine-phosphites and their use in asymmetric hydrogenation

Article abstract of DOI:10.1016/j.tetasy.2011.12.007

Excellent enantioselectivities and activities have been obtained in the rhodium catalyzed asymmetric hydrogenation of dimethyl itaconate and several dehydroamino acid esters using a new class of BINOL based phosphine-phosphite ligand. The hydrogenation pr

Full text of DOI:10.1016/j.tetasy.2011.12.007

Tetrahedron: Asymmetry 22 (2011) 2104–2109
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Tetrahedron: Asymmetry
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Novel phosphine–phosphites and their use in asymmetric hydrogenation
a
a
b
c
c
a,
⇑
Gergely Farkas , Szabolcs Balogh , Áron Szöll o} sy , László Ürge , Ferenc Darvas , József Bakos
a
Department of Organic Chemistry, University of Pannonia, H-8200 Veszprém, Egyetem u. 10, Hungary
Department of General and Analytical Chemistry, Budapest University of Technology and Economics, H-1111 Budapest, Szent Gellért tér 4, Hungary
ThalesNano Nanotechnology Inc., 1031, Budapest, Záhony u. 7, Graphisoft Park, Hungary
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 October 2011
Accepted 15 December 2011
Excellent enantioselectivities and activities have been obtained in the rhodium catalyzed asymmetric
hydrogenation of dimethyl itaconate and several dehydroamino acid esters using a new class of BINOL
based phosphine–phosphite ligand. The hydrogenation proceeded efficiently even at a substrate/catalyst
molar ratio of 10,000 to give the product with 100% conversion and 99.1% enantioselectivity.
Ó 2011 Elsevier Ltd. All rights reserved.
1
. Introduction
1
The C -symmetric phosphine–phosphite ligands (Fig. 1) have
been of great interest since Takaya and Nozaki reported on the syn-
2
Asymmetric hydrogenation using soluble rhodium catalysts
thesis and catalytic application of BINAPHOS. Ligand (R,S)-BINA-
1
constitutes a key synthetic step in many industrial processes.
The precise control of the molecular chirality plays an important
role in chemistry, life science, and material science. High activity,
selectivity and stability, readily accessible ligands, and enzyme-
like stereocontrol are among the main features of an ideal catalyst
for practical asymmetric synthesis.
PHOS 1 provided high regio- and enantioselectivities in the
rhodium-based hydroformylation of a wide range of substrates.3
In recent years, a new series of phosphine–phosphite ligands has
been developed and found to have unique catalytic properties in
hydrogenations and in other asymmetric transformations.4 Zhang
et al. developed a new BINAPHOS derivative 2 that was applied
PPh2
PPh2
O
O
O
P
O
O
O
P
Fe
P
PPh2
O
O
O
Ph
1
2
3
PPh2
O
Ph
O
tBu
PPh2
O
P
O
O
Ph P
2
P
O
O
O
O
P
O
O
O
O
tBu
4
5
6
1
Figure 1. C -Symmetric phosphine–phosphite ligands.
⇑
Corresponding author. Tel.: +36 88624355; fax: +36 886244469.
E-mail address: bakos@almos.vein.hu (J. Bakos).
0
957-4166/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2011.12.007

G. Farkas et al. / Tetrahedron: Asymmetry 22 (2011) 2104–2109
2105
in the asymmetric hydrogenation of dehydroamino acid esters.
They achieved 99% ee with methyl acetamidoacrylate as the sub-
strate. A series of new ferrocene based hybrid ligands of type 3
In order to explore the possibilities derived from the variation of
the configurations of the stereogenic centers one new ligand 10b
was synthesized from the enantiomer of cyclic sulfate 7. In the case
5
was prepared by Chan et al. and gave up to 89% ee in the hydroge-
nation of methyl acetamidocinnamate.6 Monosaccharide based
phosphine–phosphite ligands 4 were synthesized by Claver et al.
and used in the hydrogenation of methyl acetamidoacrylate and
methyl acetamidocinnamate to give the hydrogenated product
of 10c, we envisaged that the introduction of a H
8
-moiety possess-
ing a larger torsion angle could result in an improved chiral induc-
1
1
tion (Fig. 2).
2.1.1. Stereoelectronic features of novel phosphine–phosphite
ligands
7
with up to 99% ee. Pizzano et al. applied phosphine–phosphite
catalysts 5 in the hydrogenation of methyl acetamidocinnamate
and several imines (up to 99% ee).8 Vidal-Ferran et al. developed
a new library of phosphine–phosphite ligands 6, which were tested
in the asymmetric hydrogenation of a wide range of substrates.
According to their results (ees up to 99%) rhodium complexes mod-
ified by such ligands are undoubtedly excellent catalysts for
dehydroamino acid esters.9
Among bifunctional compounds phosphine–phosphites are an
interesting class of ligands due to their unique electronic proper-
ties. Their good
functionality, and good
r
-donor ability can be attributed to the phosphine
-acceptor ability to the phosphite group.
p
The rhodium coordination chemistry of ligands 10 was investi-
gated because of their relevance to the asymmetric catalysis de-
scribed below. The products formed upon treatment of the chiral
Our aim herein was the development of effective chiral ligands
that could be easily prepared using inexpensive starting materials
and successfully applied in asymmetric synthesis. Herein we report
the preparation of new hybrid phosphine–phosphite ligands
based on the axially chiral BINOL-moiety and centrally chiral
pentane-2,4-diyl backbone and their use in asymmetric catalytic
hydrogenations.
2 4
ligands with 1 or 0.5 equiv of [Rh(COD) ]BF were evaluated by
P{ H} NMR spectroscopy (Table 1 and Section 4).
3
1
1
At a ligand/metal ratio of 1:1, two double doublets were seen in
the 3 P{ H} NMR spectrum of compounds 11. When a ratio of 2:1
1
1
was applied, two double triplets were obtained. This pattern can-
not be attributed to the expected cis-[Rh(10) ]BF complexes. The
2 4
observed NMR characteristics instead correspond to the structure
of 12, where the phosphorus atoms of a similar chemical environ-
ment are in a trans-position (Scheme 2). The unique electronic fea-
tures of our ligands were also supported by the coordination
chemical shifts of the phosphorus atoms; the phosphite site is
shifted to high frequency, while the phosphine site is shifted in
the opposite direction.
2
2
. Results and discussion
.1. Synthesis of phosphine–phosphite ligands
Chiral hydroxyalkyl phosphines can be conveniently prepared
A simple way of evaluating the
r-donor ability of the phospho-
from cyclic sulfate esters, which are synthesized according to the
1
1
0
rous functionalities is by measuring the magnitude of the J(Se–P)
Sharpless method. The ring opening of cyclic sulfate 7 with
LiPPh takes place smoothly, with complete inversion at the stere-
7
7
coupling constant in the Se isotopomer of the corresponding se-
leno-phosphate and phosphine–selenide.
2
ogenic center to provide the Li-salt of the sulfated phosphine 8.
Hydrolysis gives the hydroxyalkyl phosphine 9 in a good yield
and subsequent reaction with the BINOL-derived chlorophosphite
gives the desired chiral phosphine–phosphite ligand 10a
The synthesis of the diselenides was performed by reacting the
corresponding ligand with elemental selenium. According to the
preparation method developed by Pizzano et al., the reaction pro-
ceeds in a stepwise manner and needs a prolonged reaction time
(Scheme 1).
LiPPh2
20% H SO
2
4
O
O
O
O
0
°C, THF, 100%
Ph2P
OSO3Li
90 °C, 4 h, 66%
Ph2P
OH
S
9
8
7
PPh2
O
O
O
O
P
Cl
P
O
10a
Et2O, Et3N, 62-79%
Scheme 1. Synthesis of new chiral phosphine–phosphite ligands.
PPh2
R)
PPh2
PPh2
(S)
(
S)
(
O
O
O
O
(
R)
(R)
(
S)
(
S)
(
S)
P
O
P
O
(S)
P
O
O
O
10c
10a
10b
Figure 2. Novel phosphine–phosphite ligands.

2
106
G. Farkas et al. / Tetrahedron: Asymmetry 22 (2011) 2104–2109
Table 1
31
1
P{ H} NMR data of compounds 10 and 11
Ligand
d(P
A
) (ppm)
1J(MP
A
) (Hz)
d(P
B
) (ppm)
1J(MP
B
) (Hz)
1J(P
A
P
B
) (Hz)
d
A
lig(P ) (ppm)
d
lig(P
B
) (ppm)
D
d(P
A
) (ppm)
D
d(P
B
) (ppm)
10a
10b
10c
140.73
132.83
126.53
259.5
264.0
259.5
24.35
35.94
35.88
139.2
142.6
143.7
47.9
51.2
51.2
153.50
149.33
142.05
0.00
ꢀ0.07
ꢀ0.01
ꢀ12.77
ꢀ16.50
ꢀ15.52
24.35
36.01
35.88
3 3 4 A B
All spectra measured in CDCl , at 20 °C at 121.495 or 161.976 MHz with chemical shifts to high frequency of 85% H PO . P is in the phosphite group and P is in the
phosphino group. The coordination chemical shift,
D
d = d(complex) ꢀ d(ligand).
OP
O
P
2 eq.
Rh(COD)2]BF4
1
eq.
OP
P
P
Rh
BF4
Rh
BF4
[
[
Rh(COD) ]BF
Ph2P
*
*
O
O
PO
P
2
4
11
10
Scheme 2. Coordination abilities of ligands 10.
12
Table 2
uents on the phosphorous atoms are structurally identical. On the
other hand, in compound 10c, the phosphite moiety shows a much
lower coupling constant, which indicates its higher basicity due to
the partially saturated binaphthyl unit.
3
1P–77Se coupling constants in compounds 13
O
O
P
Se
P
benzene, 24 h, rt
Ph2P
*
O
O
Ph2P
O
O
*
*
*
Se
2.2. Asymmetric catalytic hydrogenation
Se
10
13
1J(P–Se)
1J(P–Se)
Ligands 10a and 10b were evaluated in the Rh-catalyzed asym-
metric hydrogenation of several dehydroamino acid esters (Ta-
ble 3). The cationic Rh(I)-complexes were prepared in situ by
mixing the corresponding Rh(I)-precursor with 1.1 M equiv of the
Entry
Compound
A
(Hz)
B
(Hz)
1
2
3
13a
13b
13c
1033.6
1029.2
1020.2
754.0
755.2
754.0
2 2
ligand under argon in CH Cl . Hydrogenation reactions were car-
All spectra measured in benzene at 20 °C at 121.495 MHz with chemical shifts to
1
ried out at 1 bar hydrogen pressure at 0 and 20 °C. As shown in Ta-
ble 3, there were no significant differences between the catalytic
performances of ligand 10a and 10b under identical conditions. It
can also be seen that the structure of the substrates does have a
slight influence on the enantioselectivity of the reaction. However,
the activities of our catalytic systems are excellent since the con-
versions are almost complete in each case (Table 3, entries 2–11)
after 1 h reaction time. Generally, ligand 10a provides the best
ees, up to 97.1% in the hydrogenation of 14d. These slight differ-
ences in the catalytic properties of the ligands tested prompted
us to term compound 10a as matched and 10b as a mismatched li-
high frequency of 85% H
3
PO
4 A
. J(P–Se) is the coupling constant in the phosphite
group and 1J(P–Se)
B
in the phosphino group.
12
(
2–8 days) to reach completion at 100 °C in toluene. In contrast
to this, phosphine–phosphite ligands 10 react readily with sele-
nium powder to produce the desired diselenides in benzene in
2
4 h at room temperature.
From the data shown in Table 2, it is possible to conclude that
there is no remarkable difference in the coupling constants of the
phosphine fragment. It matches our expectations since the substit-
Table 3
Hydrogenation of dehydroamino acid esters using ligands 10a and 10b
COOCH3
L*/Rh
COOCH3
14a R = H
b
c
d
6 5
R = C H
*
R = p-MeO-C H
H2
6
6
4
4
R
NHCOCH3
4a-d
R
NHCOCH3
R = o-MeO-C H
1
Entry
Ligand
Substrate
T (°C)
Conv. (%)
ee (%)
1
2
3
4
5
6
7
8
9
10a
10b
10b
10a
10b
10b
10a
10b
10b
10a
10b
10b
14a
14a
14a
14b
14b
14b
14c
14c
14c
14d
14d
14d
20
20
0
20
20
0
20
20
0
20
20
0
90.8
100
95.3
99.7
100
96.6
100
100
100
100
100
81.6
96.8 (R)
93.8 (R)
96.8 (R)
95.1 (R)
95.1 (R)
94.1 (R)
96.5 (R)
96.8 (R)
95.9 (R)
97.1 (R)
92.5 (R)
94.6 (R)
1
1
1
0
1
2
Reaction conditions: 2.5 mmol substrate in 5 mL of CH
0 min.
2 2 2 4
Cl ; catalyst: 0.0055 mmol of 10a or 10b, and 0.0050 mmol of [Rh(COD) ]BF ; hydrogen pressure:1 bar; reaction time:
6

G. Farkas et al. / Tetrahedron: Asymmetry 22 (2011) 2104–2109
2107
gand.13 Since the favored enantiomer was the (R)-product in each
case, it is evident that the BINOL-moiety governs the stereochem-
ical outcome of the reaction.
Inspired by the results shown in Table 5 and in order to discover
the limits of our catalytic system, we decided to increase the sub-
strate/rhodium molar ratio (Table 6). At a ratio of 500, the reaction
was completed after 30 min, even under atmospheric pressure, to
provide the product with higher than 99% ee. Furthermore, at a
molar ratio of 5000 and 10,000, the ee still remained very high.
To the best of our knowledge, the catalytic activity of our system
is exceptional among phosphine–phosphites. Additionally, increas-
ing the molar ratio from 500 to 10,000 only caused the ee to de-
crease slightly from 99.4% to 99.1%, that is, 1 g of our ligand
could be used to produce 2.7 kg of 2-methylsuccinic acid dimethyl
ester with high enantiomeric purity in 2 h.
In order to improve the catalytic performance of our system,
[
4
Rh(10)(COD)]BF complexes were prepared and examined in the
hydrogenation of 14b at 5 bar hydrogen pressure (Table 4). The
Rh-complex of ligand 10a provided the best ee (95.8%). The effect
of H -binaphthyl moiety on the enantioselectivity was not remark-
8
able since changing ligand 10b for 10c only slightly increased the
ee from 94.0% to 94.6%.
Table 4
4
Hydrogenation of substrate 14b using [Rh(10)(COD)]BF complexes
Entry
Catalyst
Conv. (%)
ee (%)
Table 6
1
2
3
[Rh(COD)(10a)]BF
4
100
100
100
95.8 (R)
94.0 (R)
94.6 (R)
Hydrogenation of 15 using ligand 10c
[Rh(COD)(10b)]BF
[Rh(COD)(10c)]BF
4
Entry
Time (min)
p (bar)
S/Rh
500
500
5000
Conv. (%)
ee (%)
4
1
2
3
4
30
30
60
1
5
5
5
100
100
76.9
99.3
99.4 (R)
99.3 (R)
99.0 (R)
99.1 (R)
Reaction conditions: 2.5 mmol of substrate in 5 mL of CH
Rh(COD)(10a–c)]BF
0 min.
2
Cl
2
; catalyst: 0.005 mmol
[
6
4 2
; H pressure: 5 bar; temperature: 20 °C; reaction time:
120
10000
2 2
Reaction conditions: 5 mmol of substrate in 10 mL of CH Cl ; catalyst: added from a
stock solution using P/Rh = 2.2; temperature: 20 °C.
The novel ligands were then tested in the asymmetric catalytic
hydrogenation of dimethyl itaconate (Table 5). The hydrogenation
reactions were performed under different conditions (0 or 20 °C
and 1 or 5 bar) using in situ prepared catalysts. The matched–mis-
matched features observed previously in the hydrogenation of
dehydroamino acid esters seemed to change switch, compound
3
. Conclusion
In conclusion, novel chiral phosphine–phosphite ligands have
1
1
0b gave much higher ees than 10a in each case (Table 5, entries
–3). According to our observations, it can be assumed that sub-
been synthesized and applied to the asymmetric catalytic hydroge-
nation of dehydroamino acid esters and dimethyl itaconate.
According to the results a strong influence of the substrates on
the selectivity and on the reaction rate was observed. The results
also demonstrated that the phosphine–phosphites 10 are efficient
catalysts in asymmetric hydrogenation reactions. Ligands 10b and
strates with certain structural and electronic features can strongly
influence the enantioselectivity of the reaction and even switch the
matched–mismatched properties of the ligands. Furthermore, the
hydrogenation of 15 afforded the desired product with excellent
enantioselectivity (up to 99.2%). As Table 5 shows, modification
1
0c provided excellent enantioselectivities of up to 99.4% in the
of the catalyst structure by introducing the H
instead of H resulted in an expected improvement. Although dif-
ferences between the corresponding ees (entries 4 and 7, 5, and
) are quite small, it is clearly visible that ligand 10c, which pos-
8
-binaphthyl moiety
hydrogenation of dimethyl-itaconate. Furthermore, ligand 10c re-
sulted in 99.1% ee and a remarkable activity even at a substrate/
rhodium molar ratio of 10,000. Finally, it is worth noting the
attractive features of our system: (i) the starting materials are
inexpensive and easily available; (ii) the ligands have a highly
modular structure; (iii) very high activity and selectivity are main-
tained when the S/C ratio is increased; (iv) the reaction is environ-
mentally benign and energy saving because of the high S/C ratio.
We anticipate that this catalytic system will find use in an exten-
sive array of applications.
0
8
sesses a larger torsion angle, provided higher values than 10b. It
is also notable that in the case of 10c only a slight decrease was
observed in the ee (from 99.3% to 99.2%), when the pressure in-
creased from 1 to 5 bar. The temperature dependence, considering
the results obtained at 1 bar, was insignificant.
Table 5
Hydrogenation of 15 using novel phosphine–phosphite ligands
4
4
. Experimental
L*/Rh
COOCH3
COOCH3
.1. General experimental details
H COOC
3 *
H COOC
3
H2
15
All manipulations were carried out under argon using Schlenk
techniques. Solvents were purified, dried and deoxygenated by
Entry
Ligand
T (°C)
p (bar)
Time (min)
Conv. (%)
ee (%)
standard methods. and
H
0
-
H
8
-chlorophosphite,14 and the
1
2
3
4
5
6
7
8
9
10a
10a
10a
10b
10b
10b
10c
10c
10c
0
20
20
0
20
20
0
1
1
5
1
1
5
1
1
5
120
300
60
300
180
60
120
120
60
5.0
93.6
100
61.0
100
100
100
100
100
93.5
93.8
87.6
99.2
99.1
92.6
99.4
99.3
99.2
1
5
hydroxyalkyl phosphines were prepared according to the litera-
ture. All other starting materials were purchased from Aldrich.
3
1
1
1
13
P{ H}-, H NMR and C{1H}-spectra were recorded on either a
VARIAN UNITY 300 spectrometer operating at 121.42, 300.15,
and 75.43 MHz, on a Bruker Avance 400 spectrometer operating
at 161.976, 400.130, 100.613 MHz, or on a Bruker DRX-500
spectrometer operating at 202.45, 500.13, and 125.76 MHz,
respectively.
20
20
Reaction conditions: 2.5 mmol of substrate in 5 mL of CH
2 2
Cl ; Catalyst:
0
.0055 mmol of 10 or 11, and 0.0050 mmol of [Rh(COD) ]BF
2
4
.
4
.2. Hydrogenation process
It is interesting to note that the activity of our catalytic systems
changes depending upon the structure of the substrates. In general,
Rh-catalysts modified by 10 seem to be more active when 14a–d
were used as substrates instead of 15.
The substrate (2.5 mmol) was placed under argon in a stainless
steel autoclave equipped with a gas inlet. A mixture of [Rh(COD) ]-
2
BF4 (0.005 mmol) and 10 (0.0055 mmol) or [Rh(10)(COD)]BF4

2
108
G. Farkas et al. / Tetrahedron: Asymmetry 22 (2011) 2104–2109
(
0.005 mmol) was stirred in 5 mL of solvent for 20 min. The cata-
2 4
4.5. [Rh(10) ]BF 12a
lyst solution was then transferred into the autoclave via syringe.
The autoclave was pressurized with hydrogen (5 bar). After stirring
the reaction mixture for 1 h, the hydrogen pressure was released
carefully. The reaction mixture was filtered over a pad of silica
and analyzed by chiral GC. Hydrogenation reactions at 1 bar were
carried out in glass vessels using the procedure described above.
The conversions of the hydrogenation reactions of dimethyl itaco-
nate, acetamidoacrylic acid methyl ester and the enantiomeric ex-
cesses of the products were determined by chiral GC using a
Hewlett Packard HP 4890 D, equipped with b-Dex 255 column
A mixture of 10a (30 mg, 0.0512 mmol) and [Rh(COD)
2
]BF
4
(10.4 mg, 0.0256 mmol) in an NMR tube was dissolved in CDCl
3
.
3
1
1
1
P{ H} NMR (121.495 MHz, CDCl
3
): d = 27.27 (dt, J(Rh,P) =
2
1
121.4 Hz, J(P,P) = 52.3 Hz), 158.48 ppm (dt, J(Rh,P) = 215.0 Hz,
2
J(P,P) = 52.3 Hz).
0
0
4
.6. (2S,4R)-2-Diphenylphosphino-4-{(S)-dinaphtho[2,1-d:1 ,2 -
f][1,3,2]dioxaphosphepin-2-yloxy}-pentane 10b
(
30 m ꢁ 0.25 mm, df = 0.25
2
lm), N as carrier gas, a split/splitless
The title compound was obtained by the procedure described
injector at 250 °C, and a FID at 250 °C. In the case of the hydroge-
nation of dimethyl itaconate retention times at 85 °C isotherm
were 18.8 min for (R), 20.0 min for (S) and 27.6 min for the sub-
strate. In the case of hydrogenation of acetamidoacrylic acid
methyl ester retention times at 140 °C isotherm were 6.7 min for
20
for 10a; white foam. Yield: 75.7%. ½
a
ꢂ
¼ þ344:8 (c 1.05, CH
2
Cl
: C 75.76, H 5.50. Found:
): d = 0.98 (ddd,
J(P,H) = 15.13 Hz, J(H,H) = 6.83 Hz, J(P,H) = 2.29 Hz, 3H, CH ),
), 1.25 (m, diast.
), 2.63 (m, 1H, CH), 4.53 (m, 1H,
2
),
D
mp: 61–66 °C. Anal. Calcd for C37H O P
32 3 2
1
C, 75.66; H, 5.95. H NMR (400.130 MHz, CDCl
3
3
3
6
3
.21 (dd, J(H,H) = 6.14 Hz, 4J(P,H) = 1.83, 3H, CH
3
1
1
3
(
R), 7.4 min for (S) and 5.9 min for the substrate. The conversions
of the hydrogenation reactions of (Z)- -acetamidocinnamic acid
methyl ester, 4-methoxy-(Z)- -acetamidocinnamic acid methyl es-
ter, 2-methoxy-(Z)- -acetamidocinnamic acid methyl ester, and
2 2
H, CH ), 1.75 (m, diast. 1H, CH
a
13
1
CH-O), 7.10–8.00 (aromatic, 22H). C{ H} NMR (100.613 MHz,
CDCl ): d = 16.52 (d, 1C, CH ), 24.28 (d, 1C, CH ), 26.35 (d, 1C,
CH ), 42.29 (dd, 1C, CH), 71.31 (dd, 1C, CH), 122–149 ppm (aro-
matic, 32C).
a
3
3
3
a
2
the enantiomeric excesses of the products were determined by chi-
ral GC using a Hewlett Packard HP 4890 D, equipped with Chiralsil-
31
1
3
P{ H} NMR (161.976 MHz, CDCl ): d = 1.61 (s),
1
49.33 ppm (s).
L
-Val column (25 m ꢁ 0.25 mm, df = 0.12
2
lm), N as carrier gas, a
split/splitless injector at 250 °C, and a FID at 250 °C. Temperature
4
.7. [Rh(COD)(10b)]BF 11b
4
program: 2 min at 140 °C; 2 °C/min from 140 °C to 180 °C;
4
0 min at 180 °C. Retention times were 12.3 min for (R), 13.2 min
for (S), and 22.1 min for (Z)- -acetamidocinnamic acid methyl es-
ter; 25.7 min for (R), 26.3 min for (S) enantiomers, and 53.6 min for
-methoxy-(Z)- -acetamidocinnamic acid methyl ester; 21.9 min
[
Rh(COD)(10b)]BF
4
was obtained by the procedure described
; yellow powder. Yield: 90%, mp 155–
a
for [Rh(COD)(10a)]BF
4
3
1
1
1
60 °C.
3
P{ H} NMR (121.495 MHz, CDCl ): d = 33.82 (dd,
4
a
1
J(Rh,P) = 143.7 Hz, J(P,P) = 51.2 Hz), 130.83 ppm (dd, 1J(Rh,P) =
2
for (R), 22.6 min for (S), and 34.9 min for 2-methoxy-(Z)-a-acetam-
idocinnamic acid methyl ester, respectively.
2
2
64.0 Hz, J(P,P) = 51.2 Hz).
0
0
4.8. [Rh(10b) ]BF 12b
4
.3. (2R,4S)-2-Diphenylphosphino-4-{(S)-dinaphtho[2,1-d:1 ,2 -
2
4
f][1,3,2]dioxaphosphepin-2-yloxy}-pentane 10a
[
Rh(10b)
2
]BF
4
was obtained by the procedure described for
3
1
1
[
Rh(10a)
2
]BF
4
.
P{ H} NMR (121.495 MHz, CDCl
3
): d = 36.69 (dt,
At first, (2R,4S)-4-(diphenylphosphino)-pentane-2-ol 9 (1.9 g,
1
2
1
J(Rh,P) = 127.0 Hz, J(P,P) = 53.5 Hz), 146.21 ppm (dt, J(Rh,P) =
12.7 Hz, J(P,P) = 53.5 Hz).
6
.976 mmol) and triethylamine (0.81 g, 8.00 mmol) were dissolved
2
2
0
in 30 mL of ether at room temperature. Next, H -chlorophosphite
(
2.8 g, 8.00 mmol) was dissolved in 30 mL of ether at ꢀ10 °C. The
0
0
0
0
4
.9. (2S,4R)-2-Diphenylphosphino-4-{(S)-5,5 ,6,6 ,7,7 ,8,8 -
solution of the phosphine was added to the solution of the chloro-
0
0
octahydro-dinaphtho[2,1-d:1 ,2 -f][1,3,2]dioxaphosphepin-2-
phosphite at ꢀ10 °C and stirred for 30 min. The mixture was fil-
yloxy}-pentane 10c
tered through a pad of activated Al
O
2 3
and washed with 4 ꢁ 5
mL of ether. The solvent of the filtrate was removed under reduced
pressure to obtain 2.55 g (yield: 62.2%) of 10a as a white foam.
The title compound was obtained by the procedure described
for 10a starting from the corresponding phosphine and H
2
D
0
8
-chloro-
½
a
C
ꢂ
¼ þ336:6 (c 1.135, CH
2
Cl
2
), mp: 60–63 °C. Anal. Calcd for
2
D
0
1
phosphite; white foam. Yield: 78.9%. ½
CH Cl ), mp: 64 °C. Anal. Calcd for C37
Found: C, 75.02; H, 6.95. H NMR (300.130 MHz, CDCl
3
a
40
ꢂ
¼ þ185:9 (c 1.135,
37
H
32
O
3
P
2
: C, 75.76; H, 5.50. Found: C, 75.34; H, 5.45. H NMR
3
3
(
6
3
3
500.130 MHz, CDCl ): d = 0.94 (dd, J(P,H) = 15.7 Hz, J(H,H) =
.9 Hz, 3H, CH
2
2
H
O
3
P
2
: C, 74.73; H, 6.78.
): d = 0.97
1
3
3
), 1.23 (m, diast. 1H, CH
2
), 1.30 (d, J(H,H) = 6.3 Hz,
3
3
3
(
dd, J(P,C) = 15.1 Hz, J(H,H) = 6.5 Hz, 3H, CH
3
), 1.20 (d, J(H,H) =
, overlapped) 1.58 (m,
), 1.80 (m, diast. 1H, CH , overlapped),
), 2.72 (m, 1H, CH–P, overlapped), 2.72 (m, 2H,
), 2.84 (m, 4H, 2CH ), 4.53 (m, 1H, CH–O), 6.84–7.81 ppm (aro-
matic 14H). C{ H} NMR (75.468 MHz, CDCl ): d = 15.73 (d, 1C,
CH ), 22.53 (s, 1C, CH ), 22.58 (s, 1C, CH ), 22.70 (s, 1C, CH ),
2.74 (s, 1C, CH ), 23.72 (d, 1C, CH ), 25.53 (d, 1C, CH ), 27.84 (d,
C, CH ), 29.41 (s, 2C, CH ), 70.29 (dd, 1C,
H, CH ), 1.71 (m, diast. 1H, CH
3
2
), 2.54 (m, 1H, CH–P), 4.55 (m, 1H,
13
1
6.03 Hz, 3H, CH
2H, CH ), 1.80 (m, 6H, 3CH
2.31 (m, 2H, CH
3 2
), 1.20 (m, diast. 1H, CH
CH–O), 6.93–7.91 ppm (aromatic 22H). C{ H} NMR (75.468 MHz,
CDCl ): d = 15.95 (dd, 1C, CH ), 23.85 (d, 1C, CH ), 25.39 (d, 1C,
CH ), 41.73 (dd, 1C, CH), 70.50 (dd, 1C, CH), 122–148 ppm (aro-
matic 32C).
2
2
2
3
3
3
2
2
3
1
1
CH
2
2
3
P{ H} NMR (121.495 MHz, CDCl ): d = 0.00 (s),
1
3
1
1
53.51 ppm (s).
3
3
2
2
2
2
1
CH
2
3
2
4
.4. [Rh(COD)(10a)]BF
4
11a
2
2
), 41.66 (dd, 1C, CH
2
3
1
1
Ligand 10a (129.9 mg, 0.2216 mmol) dissolved in CH
2
Cl
2
(5 mL)
(90 mg,
2
), 119–147 ppm (aromatic 32C). P{ H} NMR (161.976 MHz,
): d = ꢀ0.01 (s), 142.05 ppm (s).
CDCl
3
was added dropwise to a solution of [Rh(COD)
.2216 mmol) in CH Cl
was stirred for 20 min, concentrated, filtered, and finally treated
with Et as an or-
O (3 ꢁ 5 mL) to give 180 mg of [Rh(COD)(10a)]BF
ange powder. Yield: 92%, mp 178–179 °C. P{ H} NMR (121.495
2
]BF
4
0
2
2
(5 mL). The resulting orange solution
4
.10. [Rh(COD)(10c)]BF 11c
4
2
4
31
1
[
Rh(COD)(10c)]BF
4
was obtained by the procedure described
; yellow powder. Yield: 90%, mp 199–
P{1H} NMR (121.495 MHz, CDCl ): d = 35.88 (dd,
1
2
for [Rh(COD)(10a)]BF
4
MHz, CDCl
1
3
): d = 24.35 (dd, J(Rh,P) = 139.2 Hz, J(P,P) = 49.0 Hz),
3
1
1
2
2
00 °C.
3
40.73 ppm (dd, J(Rh,P) = 259.5 Hz, J(P,P) = 49.0 Hz).

G. Farkas et al. / Tetrahedron: Asymmetry 22 (2011) 2104–2109
2109
1
J(Rh,P) = 143.7 Hz, 2J(P,P) = 51.2 Hz), 126.53 (dd, 1J(Rh,P) =
59.5 Hz, J(P,P) = 51.2 Hz).
C.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. J. Org. Chem. 2001, 66, 7626–7631;
(c) Jia, X.; Li, X.; Lam, W. S.; Kok, S. H. L.; Xu, L.; Lu, G.; Yeung, C.-H.; Chan, A. S.
C. Tetrahedron: Asymmetry 2004, 15, 2273–2278; (d) Rubio, M.; Suárez, A.;
Alvárez, E.; Pizzano, A. Chem. Commun. 2005, 628–630; Conjugate addition: (e)
Diéguez, M.; Deerenberg, S.; Pámies, O.; Claver, C.; van Leeuwen, P. W. N. M.;
Kamer, P. Tetrahedron: Asymmetry 2000, 11, 3161–3166; Hydroboration: (f)
Blume, F.; Zemolka, S.; Fey, T.; Kranich, R.; Schmalz, H.-G. Adv. Synth. Catal.
2
2
4
2
.11. [Rh(10c) ]BF
4
12c
[
Rh(10c)
Rh(10a) ]BF
J(Rh,P) = 129.1 Hz, J(P,P) = 53.3 Hz), 142.02 ppm (dt, J(Rh,P) =
2
]BF
4
was obtained by the procedure described for
2002, 344, 868–883; Asymmetyric allylic alkylation: (g) Deerenberg, S.;
3
1
1
[
2
4
.
P{ H} NMR (121.495 MHz, CDCl
3
): d = 38.62 (dt,
Schrekker, H. S.; van Strijdonck, G. P. F.; Kamer, P. C. J.; van Leeuwen, P. W.
N. M.; Fraanje, J.; Goubitz, K. J. Org. Chem. 2000, 65, 4810–4817; CO/alkene
copolymerisation: (h) Nozaki, K.; Sato, N.; Tonomura, Y.; Yasutomi, M.; Takaya,
H.; Hiyama, T.; Matsubara, T.; Koga, N. J. Am. Chem. Soc. 1997, 119, 12779–
1
2
1
2
2
11.5 Hz, J(P,P) = 53.3 Hz).
12795.
5
6
.
.
Yan, Y.; Chi, Y.; Zhang, X. Tetrahedron: Asymmetry 2004, 15, 2173–2175.
Jia, M.; Li, X. S.; Lam, W. S.; Kok, S. H. L.; Xu, L. J.; Lu, G.; Yeung, C. H.; Chan, A. S.
C. Tetrahedron: Asymmetry 2004, 15, 2273–2278.
Acknowledgements
The authors thank the National Office for Research and Technol-
ogy (KMOP 1.1.4) for financial support. This article was partly
made under the project TÁMOP-4.2.1/B-09/1/KONV-2010-0003
and TÁMOP-4.2.2/B-10/1-2010-0025. These projects are supported
by the European Union and co-financed by the European Social
Fund. We thank Mr Béla Édes for assistance in the synthetic and
catalytic experiments.
7. (a) Pámies, O.; Diéguez, M.; Net., G.; Ruiz, A.; Claver, C. Chem. Commun. 2000, 2,
383–2384; (b) Pámies, O.; Diéguez, M.; Net., G.; Ruiz, A.; Claver, C. J. Org.
2
Chem. 2001, 66, 8364–8369.
8.
(a) Suárez, A.; Pizzano, A. Tetrahedron: Asymmetry 2001, 12, 2501–2504; (b)
Vargas, S.; Rubio, M.; Suárez, A.; Pizzano, A. Tetrahedron Lett. 2005, 46, 2049–
2052; (c) Vargas, S.; Rubio, M.; Suárez, A.; Del Rio, D.; Alvárez, E.; Pizzano, A.
Organometallics 2006, 25, 961–973.
9.
Fernandez-Pérez, H.; Pericás, M. A.; Vidal-Ferran, A. Adv. Synth. Catal 2008, 350,
1984–1990.
1
1
1
0. Gao, Y.; Sharpless, K. B. J. Am. Chem. Soc. 1998, 110, 7538–7539.
1. McCarthy, M.; Guiry, P. J. Tetrahedron 2001, 57, 3809–3844.
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(2S,4R)-4-(Diphenylphosphino)pentane-2-ol
was
prepared
2
.
Sakai, N.; Mano, S.; Nozaki, K.; Takaya, H. J. Am. Chem. Soc. 1993, 115, 7033–
according to the literature method for its enantiomer, starting from the
corresponding sulfated phosphine.
7
034.
3
4
.
.
Nozaki, K.; Takaya, K.; Hiyama, T. Top. Catal. 1997, 4, 175–185.
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Chem. 2001, 66, 8364–8369; (b) Deerenberg, S.; Pámies, O.; Diéguez, M.; Claver,