Chiral diphosphites derived from D-glucose: New ligands for the asymmetric catalytic hydroformylation of vinyl arenes

Article abstract of DOI:10.1002/1521-3765(20010716)7:14<3086::AID-CHEM3086>3.0.CO;2-O

A series of novel diphosphite ligands derived from readily available D-(+)-glucose has been synthesized. These ligands have been applied to the Rh-catalyzed hydroformylation of vinyl arenes. Both excellent enantioselectivities (up to 91%) and regioselectivities (up to 98.8%) were achieved under mild conditions. The advantage of these ligands is that their modular natures allow facile, systematic variation in the configurations at the stereocenters [C(3), C(5)] at the ligand bridge and in the biphenyl substituents, enabling their effects on the stereoselectivity to be studied. Results show that the absolute configuration of the product is governed by the configuration at the stereogenic center C(3), while the level of the enantioselectivity is influenced by a cooperative effect between stereocenters C(3) and C(5). Replacement of the tert-butyl substituent by methoxy substituents at the para positions of the biphenyl moieties improved the enantioselectivities. We have characterized the rhodium complexes formed under CO/H₂ by NMR techniques and in situ IR spectroscopy and have observed that there is a relationship between the structure of the [HRh(CO)₂(PP)] species and their enantiodiscriminating performance in hydroformylation. Enantio-selectivities were highest with ligands with a strong bis-equatorial coordination preference, while an equilibrium of species with bis-equatorial and equatorial-axial coordination modes considerably reduced the ee's.

Full text of DOI:10.1002/1521-3765(20010716)7:14<3086::AID-CHEM3086>3.0.CO;2-O

FULL PAPER
Chiral Diphosphites Derived from d-Glucose:
New Ligands for the Asymmetric Catalytic Hydroformylation of Vinyl Arenes
Montserrat DieÂguez,*[a] Oscar PaÁmies,[a] Aurora Ruiz,[a]
Sergio CastilloÂn,[b] and Carmen Claver*[a]
Â
Dedicated to Professor Rafael Uson on the occasion of his 75th birthday
Abstract: A series of novel diphosphite
ligands derived from readily available d-
(‡)-glucose has been synthesized. These
ligands have been applied to the Rh-
catalyzed hydroformylation of vinyl
arenes. Both excellent enantioselectiv-
ities (up to 91%) and regioselectivities
(up to 98.8%) were achieved under mild
conditions. The advantage of these li-
gands is that their modular natures allow
facile, systematic variation in the con-
figurations at the stereocenters [C(3),
C(5)] at the ligand bridge and in the
biphenyl substituents, enabling their ef-
fects on the stereoselectivity to be stud-
ied. Results show that the absolute
tioselectivities. We have characterized
the rhodium complexes formed under
CO/H2 by NMR techniques and in situ
IR spectroscopy and have observed that
there is a relationship between the
structure of the [HRh(CO)2(PP)] spe-
cies and their enantiodiscriminating per-
formance in hydroformylation. Enantio-
selectivities were highest with ligands
with a strong bis-equatorial coordina-
tion preference, while an equilibrium of
species with bis-equatorial and equato-
rial-axial coordination modes consider-
ably reduced the eeꢀs.
configuration of the product is governed
by the configuration at the stereogenic
center C(3), while the level of the
enantioselectivity is influenced by a
cooperative effect between stereocen-
ters C(3) and C(5). Replacement of the
tert-butyl substituent by methoxy sub-
stituents at the para positions of the
biphenyl moieties improved the enan-
Keywords: diphosphites ´ hydrofor-
mylation ´ P ligands ´ rhodium ´
sugar derivatives
made in rhodium-catalyzed asymmetric hydroformylation
based on new diphosphite[4] and phosphine-phosphite[5] li-
gands. In situ spectroscopic studies of both types of ligands
suggest that the presence of only one active diastereoisomeric
hydridorhodiumcarbonyl species in solution is the key to
controlling efficient chirality transfer.[4b, 5a] However, the
mechanistic aspects of the asymmetric hydroformylation
reaction are still not understood well enough for a priori
prediction of the type of ligand needed for high enantiose-
lectivities. Binaphos is so far the only ligand with a wide scope
in asymmetric hydroformylation, although its difficult prep-
aration and the high pressures (up to 100 bar) required limit
its application.[5] In this context, much research still needs to
be done to find ligands that are readily available and provide
both good regio- and enantioselectivity in asymmetric hydro-
formylation.
Introduction
In the last few years, asymmetric hydroformylation has
attracted much attention as a potential tool for preparing
enantiomerically pure aldehydes, which are important pre-
cursors for the synthesis of fine chemicals.[1] From the early
seventies, transition metal complexes based on rhodium and
platinum have been used as catalysts in asymmetric hydro-
formylation.[1] High enantioselectivities have been obtained
with Pt/diphosphine catalysts, but these suffer from low
chemo- and regioselectivity.[2] In general, Rh/diphosphine
catalysts have high catalytic activities and regioselectivities in
branched aldehydes, but the eeꢀs do not exceed 60%.[3]
During the last decade, significant improvements have been
Â
Á
[a] Dr. M. Dieguez, Prof. Dr. C. Claver, Dr. O. Pamies,
Dr. A. Ruiz
One of the simplest methods for obtaining chiral ligands is
the transformation or derivatization of natural chiral com-
pounds, making tedious optical-resolution procedures unnec-
essary. Carbohydrates, which have been widely used in
organic synthesis either as inexpensive starting materials or
as chiral auxiliaries,[6] have only recently shown their huge
potential as a source of highly effective chiral ligands in
homogeneous catalysis.[7] Moreover, carbohydrates are highly
Á
Departament de Química Física i Inorganica
Universitat Rovira i Virgili, Pl. Imperial Tarraco 1
43005 Tarragona (Spain)
Fax : (‡34)977-55-95-63
E-mail: dieguez@química.urv.es, claver@quimica.urv.es
Â
[b] Prof. Dr. S. Castillon
Á
Departament de Química Analítica i Organica
Universitat Rovira i Virgili, Pl. Imperial Tarraco 1
43005 Tarragona (Spain)
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Chem. Eur. J. 2001, 7, No. 14

3086±3094
functionalized compounds with several stereogenic centers,
which easily allow regio- and stereoselective introduction of
different functionalities.[7] Their modular nature therefore
permits the synthesis of systematic series of ligands that can
be screened in the search for high regio- and enantioselectiv-
ities and, at the same time, can provide information about the
origin of the stereoselectivity of the reaction.
In previous studies of diphosphite ligands with furanoside
backbones (1 and 2), moderate success in asymmetric hydro-
formylation of styrene has been achieved.[7f, 8]
related to 1 and 2 but with a new stereocenter at carbon
C(5).[9] These ligands, which are easily prepared from readily
available d-(‡)-glucose, offer the prospect of systematic
variation of the configurations at C(3) and C(5), and different
substituents in the biphenyl moieties. We also report their use
in the rhodium-catalyzed, asymmetric hydroformylation of
vinyl arenes and investigate how the configuration of the
stereogenic carbon atoms C(3) and C(5) affects the enantio-
selectivity, since their configurations are expected to be
important for the course of the catalytic reaction, due to their
close vicinity to the metal. The influence of the substituents on
the biphenyl moieties is also studied. Furthermore, we have
investigated the solution structures of the important inter-
mediate species [HRh(PP)(CO)2], (PP ˆ diphosphite).
OMe
tBu
O
O
5
O
P
O
1
4
O
O
O
3
2
O
O
O
O
O
P
O
OMe
tBu
Results and Discussion
1
D-xylo
L-ribo
2
Synthesis of the chiral diphosphite ligands: Diphosphite
ligands 3 ± 10, based on furanoside backbones, were synthe-
sized from inexpensive d-(‡)-glucose as shown in Scheme 1.
These ligands constitute the four diastereomers that can be
obtained by varying the configuration of the C(3) and C(5)
atoms in the backbone in combination with two different
substituted bulky 2,2'-biphenyl moieties. The absolute config-
uration of carbon atoms in the furanoside backbone of the
synthesized diastereomers is
Since these ligands have a phosphorus moiety bound to the
nonstereogenic center C(5), we decided to examine whether
further modification of the ligands by introducing a new
stereocenter at the carbon C(5) position would improve the
enantioselectivity. With this aim in mind, we report here the
synthesis of a series of new chiral diphosphite ligands 3 ± 10,
given in a shorthand notation
as, for example, (1R, 2R, 3S,
R2
R2
R2
4R, 5R) for ligand 3.
R1
R1
R1
CH3
R2
R2
O
O
Preparation of enantiomerical-
O
O
R2
O
CH3
P
O
P
O
R1
R1
P
O
ly pure diols (13, 15, 18, 20):
Diols 13 and 18 were synthe-
sized stereospecifically in two
steps from 1,2-protected-3-O-
acetylated furanoses 11 and 16,
respectively (Scheme 1). Com-
pounds 11 and 16 are easily
prepared on a large scale by
previously reported, highly ef-
fective methods from d-glu-
cose.[10] Tosylation of diols 11
and 16 produced the expected
6-tosyl derivatives 12 and 17 in
good yields.[11] Treatment of
these tosylated compounds
with sodium methoxide at room
temperature, followed by re-
duction of the corresponding
5,6-anhydrosugars with lithium
aluminium hydride, produced
crystalline compounds 13 and
18.[12]
O
O
R1
O
R1
O
R2
P
O
O
O
O
O
O
R1
R2
3 (1R, 2R, 3S, 4R, 5R)
4 (1R, 2R, 3S, 4R, 5R)
R
1 = tBu; R2 = OMe
R1 = R2 = tBu
5 (1R, 2R, 3S, 4R, 5S)
6 (1R, 2R, 3S, 4R, 5S)
R2
R2
R1
R2
R1
O
O
R2
O
CH3
P
O
CH3
O
R1
P
O
O
O
R1
R1
R1
O
O
O
O
P
O
O
R2
R2
O
O
P
O
O
R1
R1
An improved synthesis of
diols 15 and 20 has been re-
ported,[12] but attempts to re-
produce this procedure were
unsuccessful.[13] They were fi-
R2
R2
7 (1R, 2R, 3R, 4R, 5R)
8 (1R, 2R, 3R, 4R, 5R)
R1 = tBu; R2 = OMe
R1 = R2 = tBu
9 (1R, 2R, 3R, 4R, 5S)
10 (1R, 2R, 3R, 4R, 5S)
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Â
M. Dieguez, C. Claver et al.
FULL PAPER
TsO
HO
HO
O
O
e)
e)
f)
OAc
OH
3, 4
O
O
HO
HO
b)
O
O
13 (92%)
12 (88%)
O
OAc
AcO
TfO
O
OH
O
O
O
c) d)
f)
a)
a)
OAc
OH
5, 6
11
O
O
O
O
D-(+)-Glucose
14 (49%)
15 (79%)
TsO
HO
HO
O
O
e)
e)
f)
7, 8
HO
HO
O
O
b)
O
AcO
O
OH
O
17 (81%)
18 (92%)
O
AcO
TfO
O
AcO
16
OH
O
O
f)
c) d)
9, 10
O
O
O
O
AcO
OH
19 (45%)
20 (78%)
Scheme 1. Synthesis of ligands 3 ± 10. a) Ref. [10]. b) TsCl, Py, CH2Cl2, 16 h, 20 to 258C. c) Ac2O, Py, CH2Cl2, 16 h, 0 to 258C. d) Tf2O, Py, CH2Cl2, 20 min,
258C. e) NaOMe, CH2Cl2, 1 h, 258C; LiAlH4, THF, 4 h, 608C. f) Phosphorochloridite, Py, toluene, 1008C.
nally obtained, in three steps, from compounds 11 and 16
(Scheme 1) by acetylation of position 6 under standard
conditions, followed by treatment with triflic anhydride to
obtain triflates 14 and 19. Treatment of a dichloromethane
solution of compounds 14 and 19 with sodium methoxide
afforded the corresponding 5,6-anhydrosugars with inversion
of configuration at C(5).[12] Epoxide ring-opening by using
LiAlH4 afforded easy access to the desired diols 15 and 20.[12]
especially as intermediates for the synthesis of various
pharmaceuticals such as anti-inflammatory agents.[16] In a
first set of experiments, we used ligands 3 ± 10 in the rhodium-
catalyzed, asymmetric hydroformylation of styrene, which is
widely used as a model substrate (Scheme 2).
CHO
CHO
[Rh(acac)(CO)2]
*
+
3-10
CO / H2
Preparation of diastereomeric diphosphites 3 ± 10: Optically
pure diphosphite ligands 3 ± 10 were easily prepared by
treatment of the corresponding diol with two equivalents of
the desired phosphorochloridite,[14] formed in situ (either 3,3'-
di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl phosphoro-
chloridite or 3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl
phosphorochloridite) in the presence of base (Scheme 1, step
f). All the ligands were stable during purification on neutral
silica gel under an atmosphere of argon and they were isolated
in moderate to good yields (61 ± 76%) as white solids. They
were stable at room temperature and fairly robust toward
Scheme 2. Hydroformylation of styrene with compounds 3 ± 10.
The catalysts were prepared in situ by adding one equiv-
alent of the corresponding diphosphite ligand to [Rh(acac)-
(CO)2] (acac ˆ acetylacetone) as a catalyst precursor, since
other precursors were reported to be less enantioselective.[5a]
The styrene hydroformylation results are summarized in
Table 1. In no cases were hydrogenated or polymerized
products of styrene observed.
The effects of different reaction parameters were inves-
tigated for the catalytic precursors containing ligands 3 and 9;
these ligands have opposite configurations at C(3) and C(5).
Variation of the ligand-to-rhodium ratio showed that excess
ligand was not needed to obtain good regio- and enantiose-
lectivities (entries 1 ± 3). This is an important advantage over
the most successful catalysts based on diphosphites[4] and
phosphine ± phosphite,[5] for which larger excesses of ligand
are required.
1
hydrolysis. The H and 13C NMR spectra agree with those
expected for these C1 ligands (see Experimental Section).
Rapid ring inversions (atropoisomerization) of the seven-
membered dioxaphosphepin rings occurred on the NMR
timescale, since the expected diastereoisomers were not
detected by low temperature 31P NMR.[15] Moreover, the 31P
NMR spectra of ligands 3, 4, 9, and 10 showed phosphorus ±
phosphorus coupling constants, while ligands 5 ± 8 gave rise to
a structure in solution without the correct conformation to
enhance phosphorus ± phosphorus coupling. It is to be noted
that the coupling constants for ligands 3 and 4 were much
larger than other six-bond phosphorus ± phosphorus coupling
constants in similar diphosphites (6J(P,P) ꢀ 12 Hz).[4b,15]
After identical catalyst preparation, hydroformylation ex-
periments were carried out under different partial pressures
of CO and H2 (entries 1, 4, 5 and 6). The results clearly show
that activities were best at low PCO/PH . There was therefore
2
an inverse dependency on partial CO pressure and a positive
dependency on partial H2 pressure; this suggests that hydro-
genolysis is the rate determining step. These results contrast
with reported kinetic studies of rhodium-catalyzed hydro-
Asymmetric hydroformylation of vinyl arenes: Aldehydes
derived from aryl-substituted olefins are of great interest,
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Chem. Eur. J. 2001, 7, No. 14

Chiral Diphosphites
3086±3094
Table 1. Asymmetric hydroformylation of styrene catalyzed by [Rh(acac)-
(CO)2]/diphosphite.[a]
The results of hydroformylation with catalyst precursors
containing ligands 3 ± 10 can be summarized as follows:
a) Both (S)- and (R)-2-phenylpropanal enantiomers can be
obtained with excellent regio- and enantioselectivies by
using diastereoisomeric ligands 3 and 9, respectively
(entries 7 and 9).
b) Methoxy substituents in the para positions of the biphenyl
moieties always produced enantioselectivities better than
those observed for the corresponding tert-butyl-substitut-
ed analogs (entries 7, 9 and 12, 14 vs 11, 10 and 13, 15).
However, activity and regioselectivity were hardly affect-
ed.
c) The sense of the enantiodiscrimination is predominantly
controlled by the configuration at C(3). Accordingly,
ligands 3 ± 6, with S configuration at C(3), gave (S)-2-
phenylpropanal, while ligands 7 ± 10, with R configuration
at C(3), gave (R)-2-phenylpropanal.
Entry Ligand PCO/PH2 T [8C] TOF[b] %Conv [h][c] %Regio[d] %ee[e]
1
9
9
9
9
9
9
9
3
3
4
10
5
6
7
8
1
2
1
1
1
0.5
2
0.5[h]
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
40
40
40
40
40
40
20
40
20
20
20
20
20
20
20
40
40
98
97
94
174
61
198
17
174
18
19
16
12
97 (10)
96 (10)
93 (10)
100 (6)
92 (15)
100 (6)
80 (48)
100 (6)
83 (48)
85 (48)
79 (48)
59 (48)
71 (48)
60 (48)
61 (48)
19 (5)
97.7
97.6
97.7
97.8
97.7
97.8
98.3
97.9
98.6
98.4
98.7
97.6
97.4
97.2
97.1
96
78 (R)
78 (R)
77 (R)
78 (R)
78 (R)
77 (R)
89 (R)
78 (S)
90 (S)
74 (S)
76 (R)
64 (S)
52 (S)
58 (R)
46 (R)
53 (S)
51 (R)
2[f]
3[g]
4
5
6
7
8
9
10
11
12
13
14
15
16[i]
17[i]
15
13
14
41
50
20 (5)
95
d) The results also show a cooperative effect between stereo-
centers C(3) and C(5), that is, the value of enantioselec-
tivity when C(3) has either an R or an S configuration
depends on the configuration at C(5). Therefore, when the
configuration of C(3) was S, changing C(5) from R (ligand
3) to S (ligand 5) resulted in a decrease in enantioselec-
tivity from 90% S to 64% S. When the configuration of
C(3) was R; however, the same change of C(5) from R
(ligand 7) to S (ligand 9) resulted in an increase in
enantioselectivity from 58% R to 89% R.
[a] Reaction conditions: P ˆ 10 bar, styrene (13 mmol), [Rh(acac)(CO)2]
(0.013 mmol), toluene (15 mL), PP/Rh ˆ 1.1. [b] Turn over frequency, i.e.,
mol styrene per mol Rh per h measured after 1 hour. [c] %Conversion of
styrene. [d] %Regioselectivity in 2-phenylpropanal. [e] %Enantiomeric
excess measured by GC. [f] PP/Rh ˆ 2. [g] PP/Rh ˆ 4. [h] PCO ˆ 5 bar,
PH ˆ 10 bar. [i] Data from [7f].
2
formylation with bulky diphosphite, in which the rate
determining step was the alkene coordination.[1d] Moreover,
comparison of entries 1, 4 and 5 shows that regio- and
enantioselectivity are not affected by varying the partial H2
pressure. This contrasts with the results reported by Buisman
et al. for the asymmetric hydroformylation of styrene by using
diphosphite ligands, in which increasing the hydrogen partial
pressure had a negative effect on regio- and enantioselectiv-
ity.[17]
e) The presence of a methyl substituent at C(5) significantly
increased the activity.
We next applied these new, highly efficient diphosphite
ligands 3 and 9 in the Rh-catalyzed hydroformylation of other
vinyl arenes (Table 2). As with styrene, excellent enantio- and
regioselectivities were obtained in the branched aldehydes.
Moreover, these results suggest that the presence of different
substituents in the para position hardly affects conversion,
regioselectivity or enantioselectivity.
Comparisons of entries 4 and 7, and also 8 and 9, show a
remarkable increase in enantioselectivities (up to 90%)
combined with excellent regioselectivities (up to 98.6%) on
lowering the reaction temperature. Moreover, there were no
changes in the enantioselectivities over time; this indicates
that no decomposition of the catalysts took place. Further-
more, the catalytic systems with ligands 3 and 9 provided
better activities and enantioselectivities than those with the
related diphosphite ligands 1 and 2 with xylo- and ribofurano-
side backbones[7f] (Table 1, entries 4 and 8 vs. 16 and 17).
For comparative purposes, the rest of the ligands were
tested under the conditions that gave the optimum compro-
mise between enantioselectivities and reaction rates, that is a
ligand to rhodium ratio of 1.1, a total pressure of 10 bar of
synthesis gas, a temperature of 208C and a CO to H2 ratio of
0.5. The use of ligands 4 and 10, with tert-butyl groups instead
of methoxy groups in the para positions of the biphenyl
moieties, resulted in lower enantioselectivities but similar
activities and regioselectivities (entries 10 and 11 vs 9 and 7).
The use of ligands 5 and 7, in which the configuration at
carbon atom C(5) is the opposite of that in ligands 3 and 9,
produced lower reaction rates and enantioselectivities (en-
tries 12 and 14 vs entries 9 and 7). This is also true for ligands 6
and 8, which contain tert-butyl groups in the para positions of
the biphenyl moieties (entries 13 and 15).
Table 2. Asymmetric hydroformylation of vinyl arenes with [Rh(acac)(CO)2]/
diphosphite.[a]
Entry Substrates
Ligand %Conv[b] [h] %Regio[c] %ee[d]
1
24
3
81 (48)
98.6
91 ( )
2
3
4
24
25
9
3
9
80 (48)
80 (48)
79 (48)
98.7
98.8
98.3
89 (‡)
89 (‡)
25
89 (
)
[a] Reaction conditions: P ˆ 10 bar, PCO/PH ˆ 0.5, Tˆ 208C, substrate
2
(13 mmol), [Rh(acac)(CO)2] (0.013 mmol), toluene (15 mL), PP/Rh ˆ 1.1.
[b] %Conversion measured by GC. [c] %Regioselectivity in branched alde-
hyde. [d] %Enantiomeric excess measured by GC.
Structures of [HRh(PP)(CO)2] complexes in solution: Hy-
dridorhodium diphosphite dicarbonyl complexes denoted as
[HRh(PP)(CO)2] (21 ± 28), known to be responsible for the
catalytic activity,[4, 5, 17, 18] were prepared in order to elucidate
the solution structures of these catalysts. The complexes were
prepared in situ under hydroformylation conditions (10 bar,
408C) by adding one equivalent of diphosphite ligand 3 ± 10 to
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Â
M. Dieguez, C. Claver et al.
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the catalyst precursor [Rh(acac)(CO)2] (Scheme 3). Initially,
displacement of two carbon monoxide molecules by the
ligands caused the formation of the [Rh(acac)(PP)] com-
plexes, which after a short time under hydroformylation
conditions evolved to the intermediate species [Rh(acac)-
(CO)(PP)] with characteristic rhodium ± phosphorus coupling
constants around 300 Hz.[18] Reaction times of 3 ± 4 hours
were needed for the complete formation of the desired species
[HRh(PP)(CO)2] 21 ± 28.
At room temperature, 31P {1H} NMR spectra of complex 28,
which contains ligand 10, showed a broad doublet at d ˆ 164.1
(w1/2 ˆ 63 Hz), due to 31P ± 103Rh coupling. The fact that there
is a broad doublet, not the expected eight-line spectrum, is
caused by the accidental isocronicity of the two phosphorus
atoms in fluxional behaviour. Fluxionality could be frozen out
at low temperature ( 408C). As expected for the two
nonequivalent phosphorus atoms, an eight-line spectrum
was obtained. The 1H NMR spectrum revealed a pseudo-
triplet of doublets in the hydride region at d ˆ 10.32, due to
coupling with two pseudo-equivalent phosphorus atoms
(2J(P,H) ˆ 5.9 Hz) and with the rhodium atom.
∆
[Rh(acac)(PP)]
CO
[Rh(acac)(CO)2]
+ 2 CO
+
PP
In summary, NMR data for complexes 21, 22, 27, and 28
indicate trigonal bipyramidal (TBP) hydridorhodium dicar-
bonyl species with ee coordinating diphosphites. Further
evidence is provided by IR in situ measurements. Each of the
spectra showed two carbonyl vibrations around 2070 and
2010 cm 1; these are characteristic of ee isomers (Fig-
ure 1a).[19] Moreover, formation of only one diastereoisomer
was detected by variable temperature NMR.
[HRh(PP)(CO2)]
[Rh(acac)(CO)(PP)]
CO / H2
PP = 3-10 21-28
Scheme 3. In situ preparation of catalysts.
Stable [HRh(PP)(CO)2] complexes were obtained quanti-
tatively for all the ligands, and no hydrolysis of the diphos-
phite ligands to H-diphosphonates was observed. NMR
spectroscopy under atmospheric conditions showed no de-
tectable decomposition of the complexes. Table 3 shows
selected data obtained for complexes 21 ± 28.
At room temperature, the 31P{1H} NMR spectrum of
complexes 21 and 22, containing ligands 3 and 4, showed a
broad, eight-line spectrum (w1/2 ꢁ 70 Hz) due to the two non-
equivalent phosphorus atoms and a rhodium atom (ABX
system). These broad signals suggest a fluxional process on
the NMR timescale.[4b] This was confirmed by measuring the
31P NMR at variable temperature. At
808C, the 31P
resonances showed sharp signals (w1/2 ꢁ 10 Hz). 1H NMR
spectroscopy in the hydride region revealed a quadruplet, due
to coupling with rhodium and the two phosphorus atoms. The
fact that there is a quadruplet instead of the expected doublet
of doublets of doublets is caused by the accidental coincidence
of the coupling constants. The values of the phosphorus ± hy-
dride coupling constants (2J(P,H) ꢀ 4.2 Hz) are typical of a
trigonal bipyramidal (TBP) hydridorhodium dicarbonyl spe-
cies with bis-equatorially (ee) coordinating diphosphites.
Small cis phosphorous ± hydride coupling constants have been
reported in [HRh(PP)(CO)2] complexes with ee coordinating
diphosphite ligands.[7f, 8, 17, 18]
Figure 1. In situ IR spectrum of [HRh(PP)(CO)2]. a) PP ˆ 3; b) PP ˆ 8.
The 31P{1H} NMR spectra at room temperature of com-
plexes 23 ± 26, which contain ligands 5 ± 8, had eight sharp
lines due to 31P, 31P and 31P, 103Rh couplings (ABX systems)
(Table 3). The 1H NMR spectra in the high-field region
revealed a doublet of doublets for complexes 24 ± 26, due to
the coupling constants of the hydride atom and the two
1
Table 3. Selected H and 31P NMR data for [HRh(PP)(CO)2] complexes.[a]
Complex
d P1
d P2
1J(Rh,P1)
1J(Rh,P2)
2J(P1,P2)
dH
2J(H,P)
2J(H,P)
1J(H,Rh)
21
22
23
24
25
162.0
159.4
158.6
153.4
153.8
152.6
159.2
161.1
165.9
163.2
160.4
155.1
156.7
156.2
161.8
166.0
231.2
229.1
221.2
218.1
217.9
224.4
233.2
232.7
238.4
231.3
236.7
229.4
232.5
231.9
234.5
237.8
274.1
269.3
209.1
201.7
191.7
204.8
267.7
286.5
9.94(q)
9.89(q)
4.2
3.6
30.0
28.1
36.1
27.0
4.2
3.6
4.2
5.0
5.0
4.8
4.2
3.6
1.2
10.01(ddd)
9.72(dd)
9.85(dd)
9.68(dd)
10.21(b)
10.32(dt)
[c]
±
±
±
[c]
[c]
26
27
28[b]
5.9
5.9
3.3
[a] Prepared in [D8]toluene. NMR spectra recorded under atmospheric conditions at room temperature. d in ppm. Coupling constants in Hz. [b] 31P NMR
data measured at 408C. [c] Not observed.
3090
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0947-6539/01/0714-3090 $ 17.50+.50/0
Chem. Eur. J. 2001, 7, No. 14

Chiral Diphosphites
3086±3094
nonequivalent phosphorus atoms. The values of the phospho-
rus ± phosphorus coupling constants are relatively small for a
pure coordination in a TBP.[19] Two explanations can be put
forward: firstly, the formation of a distorted TBP hydrido-
rhodium dicarbonyl species with ee coordinating diphos-
phites,[8] or secondly, a fast equilibrium mixture of bis-
equatorially and equatorial ± axial (ea) species, giving aver-
aged signals in the NMR spectra (Scheme 4).[20] Evidence for
configuration of the product is therefore governed by the
configuration of the stereogenic carbon atom C(3), while the
level of enantioselectivity is a function of a cooperative effect
between both stereocenters. Investigation of the hydridorho-
dium dicarbonyl complexes 21 ± 28 under syngas pressure by
NMR and in situ IR spectroscopy showed that the config-
urations of the stereogenic carbon atoms C(3) and C(5)
greatly influence structure and, therefore, enantioselectivity.
The best enantioselectivities were therefore obtained with
ligands that have a strong ee coordination preference, while
equilibria between ee and ea coordination modes in species
23 ± 26 considerably lowered the eeꢀs.
H
H
P
P
OC
P
Rh
CO
Rh
CO
These results are among the best that have been reported
for the asymmetric hydroformylation of vinyl arenes. Further
research into more active catalysts is now in progress,
exploiting the advantage that these sugar ligands can be so
easily modified.
CO
ee
P
ea
Scheme 4. Equilibrium between equatorial-equatorial (ee) and equatori-
al-axial (ea) species.
the latter should be supplied by the HP-IR spectra, thanks to
the faster timescale of this technique. If an equilibrium
between two isomers occurs, two sets of carbonyl frequencies
originating from the two isomers should be observed.[20] In
general, carbonyl bands of ea isomers are found at lower
wavenumbers than those of ee isomers.[21] The infrared spectra
of complexes 23 ± 26 showed four carbonyl absorption bands
Experimental Section
General Comments: All syntheses were performed by using standard
Schlenk techniques under an argon atmosphere. Solvents were purified by
standard procedures. Compounds 11,[10] 16,[10] 12,[11] 17,[11] and phosphoro-
chloridites[14] were prepared by methods described previously. All other
reagents were used as commercially available. Elemental analyses were
performed on a Carlo Erba EA-1108 instrument. 1H, 13C{1H} and 31P{1H}
NMR spectra were recorded on a Varian Gemini 300 MHz spectrometer.
Chemical shifts are relative to SiMe4 (1H and 13C) as internal standard or
H3PO4 (31P) as external standard. All NMR spectral assignments were
determined by COSY and HETCOR spectra. In situ high-pressure IR
spectra were recorded on a Nicolet510 FT-IR spectrometer. Gas chro-
matographic analyses were run on a Hewlett-Packard HP 5890A instru-
ment (split/splitless injector, J&W Scientific, Ultra-2 25 m column, internal
diameter 0.2 mm, film thickness 0.33 mm, carrier gas: 150 kPa He, F.I.D.
detector) equipped with a Hewlett-Packard HP3396 series II integrator.
Hydroformylation reactions were carried out in a custom-made 100 mL
stainless steel autoclave. Enantiomeric excesses were measured after
oxidation of the aldehydes to the corresponding carboxylic acids on a
Hewlett-Packard HP 5890A gas chromatograph (split/splitless injector,
J&W Scientific, FS-Cyclodex b-I/P 50 m column, internal diameter 0.2 mm,
film thickness 0.33 mm, carrier gas: 100 kPa He, F.I.D. detector). Absolute
configuration was determined by comparison of retention times with
optically pure (S)-(‡)-2-phenylpropionic and (R)-( )-2-phenylpropionic
acids.
1
in the 2100 ± 1900 cm region, which can be attributed to a
mixture of ee and ea isomers (Table 4, Figure 1b).[19] The
proportion of ea species was calculated from the NMR data,
by using a cis phosphorus ± proton coupling constant of 4 to
‡4 Hz and a trans phosphorus ± proton coupling constant of
210 Hz, and is 15% on average.[19] The relative intensities of
the absorption bands obtained from the HP-IR are in good
agreement with the ee:ea ratios determined by NMR
spectroscopy.
Table 4. Selected HP-IR data (cm 1) for complexes 23 ± 26.
Complex
n1 (ee)
n2(ea)
n3 (ee)
n4 (ea)
23
24
25
26
2074 (s)
2073 (s)
2070 (s)
2068 (s)
2032 (m)
2031 (m)
2029 (m)
2030 (m)
2011 (s)
2012 (s)
2008 (s)
2006 (s)
1985 (m)
1989 (m)
1988 (m)
1987 (m)
3,5-Bis[(3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)phosphite]-
1,2-O-isopropylidene-6-deoxy-a-d-glucofuranose (3): Phosphorochloridite
(2.2 mmol) produced in situ was dissolved in toluene (5 mL) and pyridine
(0.36 mL, 4.6 mmol) was added. 1,2-O-Isopropylidene-6-deoxy-a-d-gluco-
furanose 13 (0.21 g, 1 mmol) was azeotropically dried with toluene (3 Â
1 mL) and then dissolved in toluene (10 mL), to which pyridine (0.18 mL,
2.3 mmol) had been added. The diol solution was transferred slowly over
30 min at room temperature to the solution of phosphorochloridite. The
reaction mixture was stirred overnight at reflux, and the pyridine salts were
removed by filtration. Evaporation of the solvent gave a white foam, which
was purified by flash chromatography (toluene, Rf ˆ 0.13) to produce a
white powder. Yield: 0.70 g, 71%; 1H NMR: d ˆ 1.12 (s, 3H; CH3), 1.28 (d,
3J(6,5) ˆ 6.3 Hz, 3H; H-6), 1.38 (s, 3H; CH3), 1.41 (s, 9H; CH3, tBu), 1.43 (s,
18H; CH3, tBu), 1.45 (s, 9H; CH3, tBu), 3.78 (s, 3H; OMe), 3.79 (s, 3H;
OMe), 3.80 (s, 3H; OMe), 3.81 (s, 3H; OMe), 3.95 (d, 3J(2,1) ˆ 3.6 Hz, 1H;
H-2), 4.03 (dd, 3J(4,3) ˆ 2.7 Hz, 3J(4,5) ˆ 8.1 Hz, 1H; H-4), 4.70 (m, 1H;
H-5), 4.79 (dd, 3J(3,4) ˆ 2.7 Hz, J(3,P) ˆ 3.1 Hz, 1H; H-3), 5.57 (d, 3J(1,2) ˆ
Conclusion
A new family of C1 diphosphite ligands containing different
furanoside moieties as simple chiral backbones has been
easily prepared in a few steps from readily available d-(‡)-
glucose. Their rhodium(i) complexes are highly efficient
catalysts for the asymmetric hydroformylation of vinyl arenes.
Both the S and the R enantiomers of 2-phenylpropanal can be
obtained with excellent regio- and enantioselectivity under
very mild reaction conditions. In addition, these catalyst
systems are highly stable under hydroformylation conditions
and no excess of ligand is needed. The type of substituents in
the biphenyl moieties and the configuration of the stereo-
centers [C(3), C(5)] had remarkable effects on the enantio-
selectivity of the hydroformylation reactions. The absolute
ˆ
ˆ
3.6 Hz, 1H; H-1), 6.81 (m, 2H; CH ), 6.94 (m, 2H; CH ), 7.11 (m, 4H;
CH ); 13C NMR: d ˆ 19.8 (C(6)), 25.7 (CH3), 26.4 (CH3), 31.1 (CH3, tBu),
ˆ
31.2 (CH3, tBu), 35.1 (C, tBu), 35.3 (C, tBu), 55.4 (OMe), 55.5 (OMe), 68.6
(d, J(C,P) ˆ 4.8 Hz, C(5)), 76.1 (C(3)), 82.9 (t, J(C,P) ˆ 5.4 Hz, C(4)), 83.9
ˆ
ˆ
ˆ
ˆ
(C(2)), 104.6 (C(1)), 111.4 (CH ), 112.5 (CH ), 112.8 (CH ), 114.1 (CH ),
Chem. Eur. J. 2001, 7, No. 14
ꢁ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0714-3091 $ 17.50+.50/0
3091

Â
M. Dieguez, C. Claver et al.
FULL PAPER
3
ˆ
ˆ
ˆ
114.8 (CMe2), 125.2 (CH ), 128.1 (CH ), 128.9 (CH ), 133.1 (C), 133.4 (C),
134.0 (C), 134.2 (C), 141.8 (C), 142.2 (C), 142.6 (C), 142.8 (C), 155.1 (C),
155.5 (C), 155.6 (C), 155.8 (C); 31P NMR: d ˆ 144.9 (s, 2P); 31P NMR
(CD2Cl2, 233 K): d ˆ 144.6 (d, J(P,P) ˆ 30.9 Hz, 1P), 145.1 (d, J(P,P) ˆ
30.9 Hz, 1P); elemental analysis calcd (%) for C57H70O13P2: C 65.15,
H 7.22; found: C 65.09, H 7.32.
4.11 (m, 1H; H-3), 4.52 (m, 1H; H-5), 5.53 (d, 1H; H-1, J(1,2) ˆ 3.6 Hz),
6.58 (m, 4H; CH ), 6.81 (m, 4H; CH ); 13C NMR: d ˆ 17.1 (m, C(6)), 26.7
(CH3), 26.8 (CH3), 30.9 (CH3, tBu), 31.0 (CH3, tBu), 35.2 (C, tBu), 55.5
(OMe), 55.6 (OMe), 70.5 (t, C(3), J(C,P) ˆ 6.8 Hz), 72.5 (m, C(5)), 78.6
ˆ
ˆ
ˆ
(C(2)), 81.8 (t, C(4), J(C,P) ˆ 3.1 Hz), 104.0 (C(1)), 112.6 (CH ), 112.9
ˆ
ˆ
ˆ
(CH ), 113.1 (CH ), 113.5 (CMe2), 114.0 (CH ), 126.8 (C), 128.1 (C), 129.3
(C), 130.2 (C), 141.8 (C), 141.9 (C), 142.1 (C), 143.2 (C), 155.3 (C), 155.6
(C), 155.8 (C); 31P NMR: d ˆ 144.2 (s, 1P), 147.0 (s, 1P); elemental analysis
calcd (%) for C57H70O13P2: C 65.15 H, 7.22; found: C 65.07, H, 7.42.
1,2-O-Isopropylidene-3,5-bis[(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-
diyl)phosphite]-6-deoxy-a-d-glucofuranose (4): Treatment of phosphoro-
chloridite (2.2 mmol) produced in situ and 13 (0.21 g, 1 mmol), as described
for compound 3, afforded diphosphite 4, which was purified by flash
chromatography (toluene, Rf ˆ 0.18) to produce a white powder. Yield:
0.80 g, 74%; 1H NMR: d ˆ 1.02 (s, 3H; CH3), 1.09 (d, 3J(6,5) ˆ 4.2 Hz, 3H;
H-6), 1.24 (s, 9H; CH3, tBu), 1.26 (brs, 27H; CH3, tBu), 1.31 (s, 3H; CH3),
1.35 (s, 9H; CH3, tBu), 1.39 (brs, 27H; CH3, tBu), 3.98 (m, 2H; H-2, H-4),
1,2-O-Isopropylidene-3,5-bis[(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-
diyl)phosphite]-6-deoxy-a-d-allofuranose (8): Treatment of phosphoro-
chloridite (2.2 mmol) produced in situ and 18 (0.21 g, 1 mmol), as described
for compound 3, afforded diphosphite 8, which was purified by flash
chromatography (toluene, Rf ˆ 0.15) to produce a white powder. Yield:
0.65 g, 60%; 1H NMR: d ˆ 0.85 (m, 3H; H-6), 1.15 (s, 3H; CH3), 1.20 (s,
27H; CH3, tBu), 1.22 (s, 18H; CH3, tBu), 1.24 (s, 9H; CH3, tBu), 1.26 (s,
9H; CH3, tBu), 1.28 (s, 9H; CH3, tBu), 1.38 (s, 3H; CH3), 3.80 (m, 1H;
4.66 (m, 1H; H-5), 4.73 (dd, 3J(3,4) ˆ 2.4 Hz, J(3,P) ˆ 6.3 Hz, 1H; H-3),
3
ˆ
ˆ
5.38 (d, J(1,2) ˆ 3.6 Hz, 1H; H-1), 7.12 (m, 4H; CH ), 7.36 (m, 4H; CH );
13C NMR: d ˆ 19.4 (C(6)), 26.3 (CH3), 26.7 (CH3), 31.2 (CH3, tBu), 31.3
(CH3, tBu), 31.5 (CH3, tBu), 34.6 (C, tBu), 34.7 (C, tBu), 35.4 (C, tBu), 68.9
(d, C(5), J(C,P) ˆ 9.5 Hz), 76.2 (C(3)), 83.0 (t, C(2) or C(4), J(C,P) ˆ
H-2), 4.00 (m, 1H; H-4), 4.39 (m, 1H; H-5), 4.55 (m, 1H; H-3), 5.41 (d,
3
ˆ
ˆ
J(1,2) ˆ 3.3 Hz, 1H; H-1), 6.98 (m, 2H; CH ), 7.03 (m, 2H; CH ), 7.11 (m,
ˆ
ˆ
ˆ
ˆ
ˆ
5.7 Hz), 84.2 (C(4) or C(2)), 104.7 (C-1), 111.6 (CMe2), 124.0 (CH ),
1H; CH ), 7.17 (m, 1H; CH ), 7.23 (m, 1H; CH ), 7.26 (m, 1H; CH );
13C NMR: d ˆ 16.9 (C(6)), 26.9 (CH3), 31.0 (CH3, tBu), 31.1 (CH3, tBu),
31.4 (CH3, tBu), 31.5 (CH3, tBu) 34.5 (C, tBu), 34.6 (C, tBu), 34.7 (C, tBu),
35.2 (C, tBu), 35.3 (C, tBu), 35.4 (C, tBu), 70.4 (d, C(3), J(C,P) ˆ 16.6 Hz),
72.0 (C(5)), 78.7 (C(2)), 81.9 (t, C(4), J(C,P) ˆ 5.2 Hz), 104.0 (C(1)), 113.0
ˆ
ˆ
ˆ
124.2 (CH ), 126.55 (CH ), 126.6 (CH ), 132.4 (C), 132.6 (C), 133.1 (C),
133.2 (C), 139.7 (C), 140.2 (C), 140.3 (C), 145.9 (C), 146.4 (C), 146.5 (C),
146.8 (C); 31P NMR: d ˆ 144.3 (d, J(P,P) ˆ 35.7 Hz, 1P), 145.3 (d, J(P,P) ˆ
35.7 Hz, 1P); elemental analysis calcd (%) for C65H94O9P2: C 72.19, H 8.76;
found: C 72.24, H 8.84.
ˆ
ˆ
ˆ
ˆ
(CMe2), 123.8 (CH ), 123.9 (CH ), 124.0 (CH ), 1126.3 (CH ), 126.5
ˆ
ˆ
(CH ), 126.7 (CH ), 132.7 (C), 132.9 (C), 139.7(C), 139.9 (C), 140.2 (C),
140.4 (C), 145.8 (C), 146.0 (C), 146.2 (C), 146.3 (C); 31P NMR: d ˆ 143.6 (s,
1P), 146.5 (s, 1P); elemental analysis calcd (%) for C65H94O9P2: C 72.19, H
8.76; found: C 72.34, H 8.81.
3,5-Bis[(3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)phosphite]-
1,2-O-isopropylidene-6-deoxy-b-L-idofuranose (5): Treatment of phos-
phorochloridite (1.1 mmol) produced in situ and 1,2-O-isopropylidene-6-
deoxy-b-l-idofuranose 15 (0.11 g, 0.5 mmol), as described for compound 3,
afforded diphosphite 5, which was purified by flash chromatography
3,5-Bis[(3,3'-bis-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)phosphite]-
1,2-O-isopropylidene-6-deoxy-b-l-talofuranose (9): Treatment of phos-
phorochloridite (1.1 mmol) produced in situ and 1,2-O-isopropylidene-6-
deoxy-b-l-talofuranose 20 (0.11 g, 0.5 mmol), as described for compound 3,
afforded diphosphite 9, which was purified by flash chromatography
(toluene, Rf ˆ 0.10) to afford a white powder. Yield: 0.24 g, 50%; 1H NMR:
d ˆ 0.98 (brs, 3H; H-6), 1.21 (s, 3H; CH3), 1.25 (s, 9H; CH3, tBu), 1.38 (s,
9H; CH3, tBu), 1.41 (s, 18H; CH3, tBu), 1.44 (s, 3H; CH3), 3.81 (s, 12H;
1
(toluene, Rf ˆ 0.12) to give a white powder. Yield: 0.29 g, 60%; H NMR:
d ˆ 1.04 (s, 3H; CH3), 1.13 (d, 3J(6,5) ˆ 6.3 Hz, 3H; H-6), 1.37 (s, 3H; CH3),
1.42 (s, 9H; CH3, tBu), 1.44 (s, 9H; CH3, tBu), 1.49 (s, 18H; CH3, tBu), 3.74
(s, 3H; OMe), 3.76 (brs, 9H; OMe), 3.99 (d, 3J(2,1) ˆ 3.6 Hz, 1H; H-2),
4.12 (m, 3J(4,5) ˆ 6.8 Hz, 3J(4,3) ˆ 3.0 Hz, 1H; H-4), 4.78 (m, 2H; H-3,
3
ˆ
H-5), 5.62 (d, J(1,2) ˆ 3.6 Hz, 1H; H-1), 6.84 (m, 4H; CH ), 7.04 (m, 4H;
CH ); 13C NMR: d ˆ 18.5 (C(6)), 26.1 (CH3), 26.7 (CH3), 30.8 (CH3, tBu),
ˆ
31.2 (CH3, tBu), 31.5 (CH3, tBu), 35.3 (C, tBu), 35.4 (C, tBu), 55.6 (OMe),
69.3 (d, J(C,P) ˆ 6.3 Hz, C(3)), 75.2 (C(3)), 82.7 (t, J(C,P) ˆ 4.2 Hz, C-4),
OMe), 4.01 (m, 1H; H-4), 4.40 (m, 2H; H-2, H-3), 4.44 (m, 1H; H-5), 5.71
3
ˆ
ˆ
(d, 1H; H-1, J(1,2) ˆ 3.9 Hz), 6.82 (m, 4H; CH ), 6.99 (m, 4H; CH );
13C NMR: d ˆ 18.9 (d, C(6), J(C,P) ˆ 7.2 Hz), 26.7 (CH3), 26.8 (CH3), 30.8
(CH3, tBu), 31.0 (CH3, tBu), 35.2 (C, tBu), 35.3 (C, tBu), 55.4 (OMe), 55.6
(OMe), 71.4 (d, C(3), J(C,P) ˆ 10.9 Hz), 73.6 (d, C(5), J(C,P) ˆ 6.7 Hz),
78.7 (d, C(2), J(C,P) ˆ 2.4 Hz), 81.7 (t, C(4), J(C,P) ˆ 2.6 Hz), 103.8 (C(1)),
ˆ
ˆ
ˆ
84.2 (C(2)), 103.9 (C(1)), 112.8 (CH ), 113.2 (CH ), 113.5 (CH ), 114.0
ˆ
ˆ
ˆ
ˆ
(CMe2), 123.8 (CH ), 123.9 (CH ), 124.2 (CH ), 124.5 (CH ), 133.6 (C),
133.7 (C), 142.2 (C), 142.8 (C), 142.9 (C), 155.0 (C), 155.2 (C), 155.3 (C),
155.4 (C); 31P NMR: d ˆ 145.5 (s, 1P), 146.7 (s, 1P); elemental analysis
calcd (%) for C57H70O13P2: C 65.15, H 7.22; found: C 65.34, H 7.25.
ˆ
ˆ
ˆ
ˆ
112.5 (CH ), 112.7 (CH ), 112.8 (CH ), 113.2 (CMe2), 114.8 (CH ), 125.2
(C), 128.2 (C), 129.0 (C), 142.4 (C), 142.5 (C), 155.3 (C), 155.4 (C), 155.6
(C); 31P NMR: d ˆ 145.4 (d, J(P,P) ˆ 4.5 Hz, 1P), 146.3 (d, J(P,P) ˆ 4.5 Hz,
1P); elemental analysis calcd (%) for C57H70O13P2: C 65.15, H 7.22; found:
C 65.23, H 7.17
1,2-O-Isopropylidene-3,5-bis[(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-
diyl)phosphite]-6-deoxy-b-l-idofuranose (6): Treatment of phosphoro-
chloridite (2.2 mmol) produced in situ and 15 (0.21 g, 1 mmol), as described
for compound 3, afforded diphosphite 6, which was purified by flash
chromatography (toluene, Rf ˆ 0.19) to afford a white powder. Yield:
0.69 g, 65%; 1H NMR: d ˆ 0.99 (d, 3J(6,5) ˆ 6.3 Hz, 3H; H-6), 1.12 (s, 3H;
CH3), 1.24 (s, 18H; CH3, tBu), 1.26 (s, 18H; CH3, tBu), 1.32 (s, 9H; CH3,
tBu), 1.34 (brs, 27H; CH3, tBu), 1.41 (s, 3H; CH3), 4.01 (d, 1H; H-2,
1,2-O-Isopropylidene-3,5-bis[(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-
diyl)phosphite]-6-deoxy-b-l-talofuranose (10): Treatment of phosphoro-
chloridite (2.2 mmol) produced in situ and 20 (0.21 g, 1 mmol), as described
for compound 3, afforded diphosphite 10, which was purified by flash
chromatography (toluene, Rf ˆ 0.19) to give a white powder. Yield: 0.72 g,
67%; 1H NMR: d ˆ 1.02 (d, 3J(6,5) ˆ 6 Hz, 3H; H-6), 1.18 (brs, 27H; CH3,
tBu), 1.24 (s, 3H; CH3), 1.27 (s, 18H; CH3, tBu), 1.29 (s, 9H; CH3, tBu), 1.30
(s, 9H; CH3, tBu), 1.32 (s, 9H; CH3, tBu), 1.36 (s, 3H; CH3), 3.66 (m, 1H;
H-3), 3.90 (dd, 1H; H-4, 3J(4,5) ˆ 5.7 Hz, 3J(4,3) ˆ 3.2 Hz), 4.10 (m, 1H;
3J(2,1) ˆ 3.6 Hz), 4.09 (m, 1H; H-4), 4.10 (m, 1H; H-2), 4.68 (m, 1H; H-5),
3
ˆ
4.72 (m, 1H; H-3), 5.42 (d, 1H; H-1, J(1,2) ˆ 3.6 Hz), 7.06 (m, 4H; CH ),
7.31 (m, 4H; CH ); 13C NMR: d ˆ 18.9 (brs, C(6)), 25.9 (CH3), 26.5 (CH3),
ˆ
31.3 (CH3, tBu), 31.4 (CH3, tBu), 31.6 (CH3, tBu), 34.9 (C, tBu), 34.6 (C,
tBu), 35.1 (C, tBu), 68.1 (t, C(5), J(C,P) ˆ 10.1 Hz), 75.8 (C(3)), 82.4 (t,
C(4), J(C,P) ˆ 4.2 Hz), 84.1 (C(2)), 103.9 (C(1)), 113.4 (CMe2), 123.8
3
H-2), 4.28 (m, 1H; H-5), 5.49 (d, 1H; H-1, J(1,2) ˆ 3.0 Hz), 7.02 (m, 4H;
CH ), 7.25 (m, 4H; CH ); 13C NMR: d ˆ 18.6 (d, J(C,P) ˆ 5.3 Hz, C(6)),
26.8 (CH3), 26.9 (CH3), 31.0 (CH3, tBu), 31.1 (CH3, tBu), 31.3 (CH3, tBu),
31.4 (CH3, tBu), 31.5 (CH3, tBu), 31.6 (CH3, tBu), 34.5 (C, tBu), 34.6 (C,
tBu), 35.3 (C, tBu), 55.6 (d, J(C,P) ˆ 4.3 Hz, C(3)), 72.0 (dd, J(C,P) ˆ
11.5 Hz, J(C,P) ˆ 3.2 Hz, C(5)), 78.8 (d, J(C,P) ˆ 2.7 Hz, C(2)), 81.8 (t,
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
(CH ), 123.9 (CH ), 124.2 (CH ), 124.4 (CH ), 131.9 (C), 132.2 (C), 132.4
(C), 132.5 (C), 139.9 (C), 140.2 (C), 140.4 (C), 145.2 (C), 145.8 (C), 146.0
(C), 146.2; 31P NMR: d ˆ 144.6 (s, 1P), 145.3 (s, 1P); elemental analysis
calcd (%) for C65H94O9P2: C 72.19, H 8.76; found: C 72.41, H 8.82.
3,5-Bis[(3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diyl)phosphite]-
1,2-O-isopropylidene-6-deoxy-a-d-allofuranose (7): Treatment of phos-
phorochloridite (2.2 mmol) produced in situ and 1,2-O-isopropylidene-6-
deoxy-a-d-allofuranose 18 (0.21 g, 1 mmol), as described for compound 3,
afforded diphosphite 7, which was purified by flash chromatography
ˆ
J(C,P) ˆ 3.9 Hz, C(4)), 103.8 (C(1)), 113.2 (CMe2), 123.9 (CH ), 124.1
ˆ
ˆ
ˆ
(CH ), 126.5 (CH ), 126.6 (CH ), 132.5 (C), 132.7 (C), 140.0 (C), 140.2
(C), 145.6 (C), 146.2 (C), 146.3 (C), 146.6 (C); 31P NMR: d ˆ 145.9 (d,
J(P,P) ˆ 5.2 Hz, 1P), 146.8 (d, 1P, J(P,P) ˆ 5.2 Hz).Elemental analysis calcd
(%) for C65H94O9P2: C 72.19, H, 8.76; found: C 72.01, H 8.91.
1
(toluene, Rf ˆ 0.12) to give a white powder. Yield: 0.49 g, 50%; H NMR:
d ˆ 0.87 (d, 3J(6,5) ˆ 6.9 Hz, 3H; H-6), 1.14 (s, 3H; CH3), 1.24 (s, 18H; CH3,
tBu), 1.28 (s, 9H; CH3, tBu), 1.30 (s, 9H; CH3, tBu), 1.37 (s, 3H; CH3), 3.62
(s, 9H; OMe), 3.64 (s, 3H; OMe), 3.92 (m, 1H; H-4), 4.09 (m, 1H; H-2),
3,6-Di-O-acetyl-1,2-O-isopropylidene-5-O-(trifluoromethane)sulfonyl-a-
d-glucofuranose (14): Anhydrous pyridine (2 mL, 20 mmol) was added to a
solution of 11 (5.2 g, 20 mmol) in dichloromethane (40 mL). After 10 min,
3092
ꢁ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0714-3092 $ 17.50+.50/0
Chem. Eur. J. 2001, 7, No. 14

Chiral Diphosphites
3086±3094
acetic anhydride (1.9 mL, 20 mmol) was added dropwise over 30 min at
08C and the mixture was allowed to react at room temperature. After 16 h,
water (50 mL) was added, and the mixture was extracted with dichloro-
methane (3 Â 50 mL). The organic layer was washed with dilute sulphuric
acid and water, dried over MgSO4, and evaporated. The residue was
purified by flash chromatography (ethyl acetate/hexane 1:2) to obtain the
C(3)), 83.1 (m, C(4)), 84.5 (m, C(2)), 104.9 (C(1)), 112.6 (CMe2), 124.4
ˆ
ˆ
ˆ
ˆ
(CH ), 124.8 (CH ), 126.5 (CH ), 126.9 (CH ), 132.0 (C), 132.3 (C), 132.4
(C), 140.0 (C), 140.2 (C), 146.5 (C), 146.6 (C), 146.9 (C).
[HRh(CO)2(5)] (23): 1H NMR: d ˆ 10.01 (dd, 2J(P,H) ˆ 30.6 Hz,
2J(P,H) ˆ 4.2 Hz, 1H), 1.02 (m, 3H; H-6), 1.12 (s, 3H; CH3), 1.35 (s, 3H;
CH3), 1.45 (s, 9H; CH3, tBu), 1.48 (s, 18H; CH3, tBu), 1.51 (s, 9H; CH3,
tBu), 3.29 (s, 12H; OMe), 4.02(d, 3J(2,1) ˆ 3.9 Hz, 1H; H-2), 4.43 (m, 1H;
1
diacetylated compound as a colorless liquid. Yield: 3.8 g, 62%; H NMR:
d ˆ 1.26 (s, 3H; CH3), 1.51 (s, 3H; CH3), 2.03 (s, 3H; OAc), 2.08 (s, 3H;
OAc), 3.51 (brs, 1H; OH), 3.98 (dd, 2J(6',6) ˆ 9.6 Hz, 3J(6',5) ˆ 5.1 Hz, 1H;
H-6'), 4.10 (m, 1H; H-5), 4.15 (m, 1H; H-3), 4.21 (dd, 2J(6',6) ˆ 9.6 Hz,
3J(6,5) ˆ 2.9 Hz, 1H; H-6), 4.80 (d, 3J(2,1) ˆ 3.6 Hz, 1H; H-2), 4.89 (dd,
3J(4,3) ˆ 6.9 Hz, 3J(4,5) ˆ 3.9 Hz, 1H; H-4), 5.79 (d, 3J(1,2) ˆ 3.6 Hz, 1H;
H-1); 13C NMR: d ˆ 20.6 (OAc), 20.8 (OAc), 26.6 (CH3), 64.5 (C(3)), 69.9
(C(6)), 71.5 (C(5)), 77.6 (C(4)), 77.7 (C(2)), 104.0 (C(1)), 113.2 (CMe2),
170.2 (CO), 171.0 (CO).
3
H-4), 4.72 (m, 1H; H-3), 4.99 (m, 1H; H-5), 5.69 (d, J(1,2) ˆ 3.9 Hz, 1H;
ˆ
ˆ
ˆ
H-1), 6.82 (m, 4H; CH ), 6.92 (m, 2H; CH ), 6.95 (m, 2H; CH );
13C NMR: d ˆ 19.9 (m, C(6)), 27.1 (CH3), 27.8 (CH3), 31.5 (CH3, tBu), 31.7
(CH3, tBu), 34.8 (C, tBu), 35.0 (C, tBu), 54.9 (OMe), 55.0 (OMe), 77.1 (m,
C(5)), 78.5 (m, C(3)), 81.2 (m, C(4)), 83.2 (m, C-2), 104.2 (C(1)), 112.6
ˆ
ˆ
ˆ
ˆ
(CMe2), 113.5 (CH ), 114.1 (CH ), 114.3 (CH ), 114.5 (CH ), 133.4 (C),
133.5 (C), 134.2 (C), 134.3 (C), 145.9 (C), 146.3 (C), 146.5 (C), 155.8 (C),
155.9 (C), 156.3 (C).
[HRh(CO)2(6)] (24): 1H NMR: d ˆ 9.72 (dd, 2J(P,H) ˆ 28.1 Hz,
1J(P,H) ˆ 5.0 Hz, 1H), 1.03 (m, 3H; H-6), 1.20 (s, 3H; CH3), 1.23 (s, 9H;
CH3, tBu), 1.27 (s, 18H; CH3, tBu), 1.29 (s, 9H; CH3, tBu), 1.35 (s, 3H;
CH3), 1.52 (s, 9H; CH3, tBu), 1.53 (s, 9H; CH3, tBu), 1.56 (s, 18H; CH3,
Anhydrous pyridine (0.5 mL, 5 mmol) was added to a solution of 3,6-di-O-
acetyl-1,2-O-isopropylidene-a-d-glucofuranose (1.52 g, 5 mmol) in di-
chloromethane (20 mL). After 10 min, trifluoromethanesulfonic anhydride
(0.85 mL, 5 mmol) was added dropwise at 208C, and the mixture was
allowed to react at room temperature for 20 min, after which the solvent
was evaporated. The residue was purified by flash chromatography on a
small column of neutral silica (hexane/ethyl acetate 1:1) to produce the
3
tBu), 4.11 (d, J(2,1) ˆ 3.0 Hz, 1H; H-2), 4.15 (m, 1H; H-4), 4.97 (m, 1H;
3
H-3), 5.08 (m, 1H; H-5), 5.71 (d, J(1,2) ˆ 3.0 Hz, 1H; H-1), 7.30 (m, 4H;
CH ), 7.41 (m, 4H; CH ); 13C NMR: d ˆ 19.1 (m, C(6)), 26.5 (CH3), 27.2
(CH3), 31.3 (CH3, tBu), 31.5 (CH3, tBu), 32.1 (CH3, tBu), 35.1 (C, tBu), 35.3
(C, tBu), 35.8 (C, tBu), 68.3 (m, C(5)), 71.3 (m, C(3)), 80.1 (m, C(4)), 81.9
ˆ
ˆ
1
triflate as a colorless liquid. Yield: 1.4 g, 72%; H NMR: d ˆ 1.33 (s, 3H;
CH3), 1.51 (s, 3H; CH3), 2.11 (s, 3H; OAc), 2.14 (s, 3H; OAc), 4.16 (dd,
2J(6',6) ˆ 10.6 Hz, 3J(6',5) ˆ 5.9 Hz, 1H; H-6'), 4.38 (m, 2H; H-3, H-6), 4.82
(dd, 3J(4,3) ˆ 4.8 Hz, 3J(4,5) ˆ 2.7 Hz, 1H; H-4), 4.89 (d, 3J(2,1) ˆ 3.6 Hz,
1H; H-2), 5.28 (m, 1H; H-5), 5.81 (d, 1H; H-1, 3J(1,2) ˆ 3.6 Hz).
ˆ
ˆ
(m, C-2), 103.4 (C(1)), 112.9 (CMe2), 124.7 (CH ), 124.8 (CH ), 125.0
ˆ
ˆ
(CH ), 125.2 (CH ), 132.3 (C), 132.5 (C), 133.0 (C), 133.2 (C), 145.9 (C),
146.3 (C), 146.5 (C), 146.8 (C), 147 (C).
[HRh(CO)2(7)] (25): 1H NMR: d ˆ 9.85 (dd; 2J(P,H) ˆ 36.1 Hz,
2J(P,H) ˆ 5.0 Hz, 1H), 0.93 (s, 3H; CH3), 1.14 (d, 3J(6,5) ˆ 5.7 Hz, 3H;
H-6), 1.35 (s, 3H; CH3), 1.65 (s, 9H; CH3, tBu), 1.68 (s, 9H; CH3, tBu), 1.69
(s, 9H; CH3, tBu), 1.72 (s, 9H; CH3, tBu), 3.33 (s, 12H; OMe), 4.07 (m, 1H;
H-4), 4.50 (dd, 3J(2,1) ˆ 3.9 Hz, 3J(2,3) ˆ 2.4 Hz, 1H; H-2), 4.72 (m, 1H;
3,6-Di-O-acetyl-1,2-O-isopropylidene-5-O-trifluoromethanesulfonyl-a-d-
allofuranose (19): Treatment of 3,6-di-O-acetyl-1,2-O-isopropylidene-a-d-
allofuranose[22] (1.52 g, 5 mmol), obtained by treating 16 with acetic
anhydride as described before, with trifluoromethanesulfonic anhydride
(0.85 mL, 5 mmol), as described for 14, afforded triflate 19. This was
purified by column chromatography on neutral silica (hexane/ethyl acetate
1:1) to produce a colorless liquid. Yield: 1.38 g, 71%; 1H NMR: d ˆ 1.31 (s,
3H; CH3), 1.52 (s, 3H; CH3), 2.06 (s, 3H; OAc), 2.12 (s, 3H; OAc), 4.12 (dd,
2J(6',6) ˆ 10.2 Hz, 3J(6',5) ˆ 6.2 Hz, 1H; H-6'), 4.31 (dd, 3J(3,4) ˆ 5.2 Hz,
3J(3,2) ˆ 2.4 Hz, 1H; H-3), 4.42 (dd, 2J(6,6') ˆ 9.6 Hz, 3J(6,5) ˆ 2.9 Hz, 1H;
H-6), 4.72 (dd, 3J(4,3) ˆ 5.2 Hz, 3J(4,5) ˆ 3.9 Hz, 1H; H-4), 4.84 (dd,
3J(2,1) ˆ 3.6 Hz, 3J(2,3) ˆ 2.4 Hz, 1H; H-2), 5.21 (m, 1H; H-5), 5.79 (d,
3J(1,2) ˆ 3.6 Hz, 1H; H-1); 13C NMR: d ˆ 20.4 (OAc), 20.5 (OAc), 26.5
(CH3), 26.7 (CH3), 61.1 (C(3)), 72.5 (C(6)), 75.4 (C(4)), 77.1 (C(2)), 84.2
(C(5)), 104.1 (C(1)), 113.7 (CMe2), 119.4 (q, CF3, 1J(C,F) ˆ 309 Hz), 170.1
(CO), 170.6 (CO).
3
H-3), 4.80 (m, 1H; H-5), 5.40 (d, 1H; H-1, J(1,2) ˆ 3.9 Hz), 6.51 (m, 2H;
ˆ
ˆ
ˆ
ˆ
CH ), 6.60 (m, 2H; CH ), 6.65 (m, 2H; CH ), 6.68 (m, 2H; CH );
13C NMR: d ˆ 20.5 (m, C-6), 26.5 (CH3), 26.7 (CH3), 31.7 (CH3, tBu), 32.9
(CH3, tBu), 33.0 (CH3, tBu), 35.7 (C, tBu), 36.2 (C, tBu), 54.6 (OMe), 54.7
(OMe), 54.8 (OMe), 76.0 (d, J ˆ 9.1 Hz, C(5)), 76.9 (C(3)), 79.9 (C(2)), 80.8
ˆ
ˆ
(t, J ˆ 8.9 Hz, C(4)), 103.9 (C(1)), 112.8 (CMe2), 113.7 (CH ), 113.8 (CH ),
ˆ
ˆ
ˆ
ˆ
114.5 (CH ), 114.7 (CH ), 115.7 (CH ), 115.9 (CH ), 133.2 (C), 133.8 (C),
133.9 (C), 134.2 (C), 141.2 (C), 142.0 (C), 142.5 (C), 143.0 (C), 156.1 (C),
156.4 (C), 156.5 (C), 156.6 (C).
[HRh(CO)2(8)] (26): 1H NMR: d ˆ 9.68 (dd, 2J(P,H) ˆ 27.0 Hz, 2J(P,H) ˆ
4.8 Hz, 1H), 0.92 (m, 3H; H-6), 1.22 (s, 9H; CH3, tBu), 1.24 (s, 9H; CH3,
tBu), 1.29 (s, 18H; CH3, tBu), 1.32 (s, 3H; CH3), 1.59 (s, 3H; CH3), 1.70 (s,
9H; CH3, tBu), 1.74 (s, 9H; CH3, tBu), 1.76 (s, 9H; CH3, tBu), 1.79 (s, 9H;
In situ HP-NMR hydroformylation experiments: In a typical experiment, a
sapphire tube (f ˆ 10 mm) was filled under argon with a solution of
[Rh(acac)(CO)2] (0.030 mmol) and ligand (molar ratio PP/Rh ˆ 1.1) in
[D8]toluene (1.5 mL). The HP-NMR tube was purged twice with CO and
pressurized to the appropriate pressure of CO/H2. After a reaction time of
16 hoursꢀ shaking at the desired temperature, the solution was analyzed.
3
CH3, tBu), 4.10 (m, 1H; H-4), 4.52 (t, J(2,1) ˆ 3.6 Hz, 1H; H-2), 4.72 (m,
3
1H; H-5), 4.75 (m, 1H; H-3), 5.49 (d, J(1,2) ˆ 3.6 Hz, 1H; H-1), 7.19 (m,
4H; CH ), 7.56 (m, 2H; CH ), 7.62 (m, 2H; CH ); 13C NMR: d ˆ 19.6 (C-
6), 26.8 (CH3), 31.4 (CH3, tBu), 31.5 (CH3, tBu), 31.9 (CH3, tBu), 32.0 (CH3,
tBu), 32.9 (CH3, tBu), 33.2 (CH3, tBu), 35.7 (C, tBu), 35.8 (C, tBu), 36.2 (C,
tBu), 36.3 (C, tBu), 76.1 (d, C(5), J ˆ 9.8 Hz), 76.9 (C(3)), 79.9 (C-2), 81.2 (t,
ˆ
ˆ
ˆ
[HRh(CO)2(3)] (21): 1H NMR: d ˆ 9.94 (q, 2J(P,H) ˆ 4.7 Hz, 1J(Rh,H) ˆ
4.7 Hz, 1H), 0.95 (m, 3H; H-6), 1.12 (s, 3H; CH3), 1.31 (s, 3H; CH3), 1.45 (s,
9H; CH3, tBu), 1.48 (s, 9H; CH3, tBu), 1.49 (s, 9H; CH3, tBu), 1.51 (s, 9H;
CH3, tBu), 3.28 (brs, 12H; OMe), 3.74 (d, 3J(2,1) ˆ 3.6 Hz, 1H; H-2), 4.12
(m, 1H; H-4), 4.22 (m, 1H; H-3), 5.49 (m, 1H; H-5), 5.71 (d, 3J(1,2) ˆ
ˆ
ˆ
J ˆ 7.9 Hz, C(4)), 104.1 (C(1)), 112.9 (CMe2), 124.3 (CH ), 124.6 (CH ),
ˆ
ˆ
ˆ
ˆ
ˆ
124.7 (CH ), 125.0 (CH ), 125.4 (CH ), 125.6 (CH ), 125.9 (CH ), 132.5
(C), 132.6 (C), 133.1 (C), 133.6 (C), 139.9 (C), 140.3 (C), 140.9 (C), 146.2
(C), 146.8 (C), 146.9 (C), 147.1 (C).
3.6 Hz, 1H; H-1), 6.82 (m, 2H; CH ), 7.10 (m, 6H; CH ); 13C NMR: d ˆ
19.6 (m, C(6)), 26.2 (CH3), 26.9 (CH3), 31.4 (CH3, tBu), 31.9 (CH3, tBu),
32.3 (CH3, tBu), 32.4 (CH3, tBu), 35.2 (C, tBu), 35.5 (C, tBu), 54.8 (OMe),
54.9 (OMe), 55.0 (OMe), 69.1 (m, C(3)), 76.2 (m, C(5)), 78.7 (m, C(2)), 83.5
ˆ
ˆ
1
[HRh(CO)2(9)] (27): H NMR: d ˆ 10.21 (brs, 1H), 1.11 (m, 3H; H-6),
1.34 (s, 3H; CH3), 1.41 (s, 9H; CH3, tBu), 1.45 (s, 3H; CH3), 1.52 (s, 9H;
CH3, tBu), 1.54 (s, 9H; CH3, tBu), 1.58 (s, 9H; CH3, tBu), 3.21 (s, 3H;
OMe), 3.23 (s, 3H; OMe), 3.24 (s, 3H; OMe), 3.26 (s, 3H; OMe), 4.14 (m,
1H; H-4), 4.60 (dd, 3J(2,1) ˆ 3.0 Hz, 3J(2,3) ˆ 4.2 Hz, 1H; H-2), 5.03 (m,
ˆ
ˆ
(m, C(4)), 102.4 (C(1)), 113.0 (CMe2), 114.0 (CH ), 114.8 (CH ), 115.3
ˆ
ˆ
(CH ), 115.5 (CH ), 131.1 (C), 131.4 (C), 132.0 (C), 132.5 (C), 145.1 (C),
145.3 (C), 145.7 (C), 155.3 (C), 155.4 (C), 156.0 (C).
3
1H; H-3), 5.08 (m, 1H; H-5), 5.77 (d, 1H; H-1, J(1,2) ˆ 3.0 Hz), 6.62 (m,
4H; CH ), 6.81 (m, 4H; CH ); 13C NMR: d ˆ 18.3 (m, C(6)), 26.3 (CH3),
26.8 (CH3), 30.7 (CH3, tBu), 31.3 (CH3, tBu), 31.7 (CH3, tBu), 32.3 (CH3,
tBu), 35.3 (C, tBu), 35.5 (C, tBu), 35.8 (C, tBu), 36.0 (C, tBu), 55.1 (OMe),
68.8 (m, C(3)), 73.8 (t, C(5), J ˆ 6.5 Hz), 79.2 (m, C(2)), 81.0 (m, C(4), 104.1
ˆ
ˆ
[HRh(CO)2(4)] (22): 1H NMR: d ˆ 9.89 (q, 1H; 2J(P,H) ˆ 3.6 Hz,
1J(Rh,H) ˆ 3.6 Hz), 0.92 (m, 3H; H-6), 1.25 (s, 9H; CH3, tBu), 1.28 (s,
9H; CH3, tBu), 1.31 (s, 18H; CH3, tBu), 1.36 (s, 3H; CH3), 1.57 (s, 3H;
CH3), 1.62 (s, 18H; CH3, tBu), 1.64 (s, 9H; CH3, tBu), 1.66 (s, 9H; CH3,
tBu), 3.79 (d, 3J(2,1) ˆ 3.6 Hz, 1H; H-2), 4.25 (dd, 3J(4,5) ˆ 7.2 Hz, 3J(4,3) ˆ
ˆ
ˆ
ˆ
(C(1)), 113.0 (CH ), 113.5 (CMe2), 113.9 (CH ), 114.7 (CH ), 115.5
(CH ), 132.6 (C), 132.7 (C), 132.9 (C), 133.4 (C), 141.3 (C), 141.7 (C), 142.0
(C), 142.4 (C), 156.2 (C), 156.5 (C), 146.7 (C), 157.0 (C).
ˆ
2.8 Hz, 1H; H-4), 4.82 (m, 1H; H-5), 5.21 (m, 1H; H-5), 5.72 (d, 1H; H-1,
3
ˆ
ˆ
J(1,2) ˆ 3.6 Hz), 7.11 (m, 3H; CH ), 7.14 (m, 1H; CH ), 7.21 (m, 2H;
CH ); 13C NMR: d ˆ 19.7 (m, C(6)), 26.2 (CH3), 27.0 (CH3), 31.5 (CH3,
[HRh(CO)2(10)] (28): 1H NMR: d ˆ 10.32 (dt, 1J(Rh,H) ˆ 3.3 Hz,
ˆ
tBu), 32.0 (CH3, tBu), 35.7 (C, tBu), 36.3 (C, tBu), 70.9 (m, C(5)), 78.2 (m,
2J(P,H) ˆ 5.9 Hz, 1H), 1.08 (m, 3H; H-6), 1.19 (s, 3H; CH3), 1.21 (s, 9H;
Chem. Eur. J. 2001, 7, No. 14
ꢁ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0714-3093 $ 17.50+.50/0
3093

Â
M. Dieguez, C. Claver et al.
FULL PAPER
CH3, tBu), 1.22 (s, 9H; CH3, tBu), 1.23 (s, 9H; CH3, tBu), 1.24 (s, 9H; CH3,
tBu), 1.33 (s, 3H; CH3), 1.52 (s, 9H; CH3, tBu), 1.56 (s, 9H; CH3, tBu), 1.61
(s, 9H; CH3, tBu), 1.64 (s, 9H; CH3, tBu), 4.18 (m, 1H; H-4), 4.62 (dd,
[5] a) K. Nozaki, N. Sakai, T. Nanno, T. Higashijima, S. Mano, T.
Á
Horiuchi, H. Takaya, J. Am. Chem. Soc. 1997, 119, 4413; b) G. Francio,
W. Leitner, Chem. Commun. 1999, 1663.
3J(2,1) ˆ 3.3 Hz, 3J(2,3) ˆ 4.2 Hz, 1H; H-2), 5.01 (m, 1H; H-3), 5.09 (m,
[6] a) J. S. Penne in Chiral Auxiliaries and Ligands in Asymmetric
Synthesis, Wiley, New York, 1995; b) S. Hanessian in Total Synthesis
of Natural Products: The ªChironº Approach, Vol. 3, Pergamon,
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[7] For some recent applications see: a) M. Beller, J. G. E. Krauter, A.
Zapf, Angew. Chem. 1997, 109, 793; Angew. Chem. Int. Ed. Engl. 1997,
36, 772; b) M. Reetz, S. R. Waldvogel, Angew. Chem. 1997, 109, 870;
Angew. Chem. Int. Ed. Engl. 1997, 36, 865; c) K. Yonehara, T.
Hashizume, K. Mori, K. Ohe, S. Uemura, Chem. Commun. 1999, 415;
d) T. V. RajanBabu, B, Radetich, K. K. You, T. A. Ayers, A. L.
Casalnuovo, J. C. Calabrese, J. Org. Chem. 1999, 64, 3429,and
3
ˆ
1H; H-5), 5.79 (d, J(1,2) ˆ 3.3 Hz, 1H; H-1), 7.31 (m, 4H; CH ), 7.52 (m,
4H; CH ); 13C NMR: d ˆ 18.3 (m, C(6)), 26.4 (CH3), 26.8 (CH3), 31.3
ˆ
(CH3, tBu), 31.4 (CH3, tBu), 31.8 (CH3, tBu), 32.0 (CH3, tBu), 32.2 (CH3,
tBu), 35.5 (C, tBu), 35.6 (C, tBu), 35.7 (C, tBu), 35.8 (C, tBu), 69.2 (m, C(3)),
74.4 (m, C(5)), 79.2 (t, C(2), J ˆ 3.9 Hz), 81.2 (t, C(4), J ˆ 4.3 Hz), 104.2
ˆ
ˆ
ˆ
ˆ
(C(1)), 113.2 (CMe2), 124.7 (CH ), 125.0 (CH ), 127.6 (CH ), 127.9 (CH ),
ˆ
ˆ
128.2 (CH ), 129.2 (CH ), 131.3 (C), 131.7 (C), 132.4 (C), 133.0 (C), 146.0
(C), 146.2 (C), 146.6 (C), 146.9 (C); 31P NMR: d ˆ 164.0 (bd, 1J(Rh,P) ˆ
234.2 Hz, 2P).
High-pressure IR experiments: These experiments were performed in an
SS316 50 mL autoclave equipped with IRTRAN windows (ZnS, trans-
parent up to 70cm 1, 10 mm i.d., optical path length 0.4 mm), a mechanical
stirrer, a temperature controller, and a pressure device. In a typical
experiment, a degassed solution of [Rh(acac)(CO)2] (0.013 mmol) and
diphosphite (0.015 mmol) in methyltetrahydrofuran (15 mL) was intro-
duced into the high pressure IR autoclave. The autoclave was purged twice
with CO, pressurized to 10 bar of CO/H2 and heated to 408C. The reaction
was usually completed in 3 ± 4 hours.
Á
Â
references therein; e) O. Pamies, M. Dieguez, G. Net, A. Ruiz, C.
Á
Claver, Organometallics 2000, 19, 1488; f) O. Pamies, G. Net, A. Ruiz,
Á
C. Claver, Tetrahedron: Asymmetry 2000, 11, 1097; g) O. Pamies, G.
Á
Net, A. Ruiz, C. Claver, Eur. J. Inorg. Chem. 2000, 2011; h) O. Pamies,
Â
M. Dieguez, G. Net, A. Ruiz, C. Claver. Chem. Commun. 2000, 2383;
i) W. Li, Z. Zhang, D. Xiao, X. Zhang, J. Org. Chem., 2000, 65, 3489;
Á
Â
j) O. Pamies, M. Dieguez, G. Net, A. Ruiz, C. Claver, Tetrahedron:
Asymmetry 2000, 11, 4377.
[8] G. J. H. Buisman, M. E. Martin, E. J. Vos, A. Klootwijk, P. C. J.
Kamer, P. W. N. M. van Leeuwen, Tetrahedron: Asymmetry 1995, 6,
719.
Hydroformylation experiments: In a typical experiment, the autoclave was
purged three times with CO. The solution was formed from [Rh(acac)-
(CO)2] (0.013 mmol) and diphosphite (0.015 mmol) in toluene (10 mL).
After pressurizing to the desired pressure with syngas and heating the
autoclave to the reaction temperature, the reaction mixture was stirred for
16 hours to form the active catalyst. In situ IR measurements indicate
shorter reaction times (3 ± 4 hours) for the complete formation of the active
catalysts. The autoclave was depressurized and a solution of styrene
(13 mmol) in toluene (5 mL) was introduced into the autoclave, which was
pressurized again. During the reaction several samples were taken from the
autoclave. After the desired reaction time, the autoclave was cooled to
room temperature and depressurized. The reaction mixture was analyzed
by gas chromatography.
[9] The preliminary hydroformylation results with ligand 3 were partly
Â
Á
Â
reported in M. Dieguez, O. Pamies, A. Ruiz, S. Castillon, C. Claver,
Chem. Commun. 2000, 1607.
[10] O. T. Schmidt in Methods in Carbohydrate Chemistry, Vol. 2, (Eds.:
R. L. Whistler, M. L. Wolfrom), Academic Press, New York, 1963.
[11] M. Nakjima, S. Takahashi, Agric. Biol. Chem. 1967, 31, 1079.
[12] J. Hiebl, E. Zbiral, Monatsh. Chem. 1990, 121, 691.
[13] The formation of 5,6-anhydrosugars from the corresponding mes-
ylated compounds proceeds with low degrees of conversion (around
10%).
[14] Phosphorochloridites are easily prepared in one step from the
corresponding bisphenol as described in G. J. H. Buisman, P. C. J.
Kamer, P. W. N. M. van Leeuwen, Tetrahedron: Asymmetry 1993, 4,
1625.
Acknowledgements
[15] D. D. Pastor, S. P. Shum, R. K. Rodebaugh, A. D. Debellis, F. H.
Clarke, Helv. Chim. Acta 1993, 76, 900.
Â
We thank the Spanish Ministerio de Educacion
y Cultura and the
Generalitat de Catalunya (CIRIT) for their financial support (PB97-
0407-CO5-01). We are also very much indebted to Prof. P. W. N. M.
van Leeuwen, University of Amsterdam, for his helpful comments and
suggestions.
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Received: January 11, 2001 [F2996]
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