Diphosphite ligands based on ribose backbone as suitable ligands in the hydrogenation and hydroformylation of prochiral olefins

Article abstract of DOI:10.1016/S0957-4166(00)00061-6

Rh(I) and Ir(I) cationic complexes [M(cod)(PP)]BF₄ have been synthesised from diphosphite ligands 4-6 derived from ribofuranose. They have been used in the rhodium and iridium catalysed asymmetric hydrogenation of acrylic acid derivatives. Ribose derivative ligands 4-6 have also been used as auxiliaries in the Rh-catalysed hydroformylation of styrene. Hydroformylation results have been explained on the basis of the species formed under hydroformylation conditions. Comparative experiments with the related epimer D-(+)-xylose derivatives showed that the configuration of the product is controlled by the absolute configuration of the stereogenic carbon atom C-3. Copyright (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0957-4166(00)00061-6

Tetrahedron: Asymmetry 11 (2000) 1097±1108
Diphosphite ligands based on ribose backbone as suitable
ligands in the hydrogenation and hydroformylation of
prochiral ole®ns
Oscar Pamies, Gemma Net, Aurora Ruiz* and Carmen Claver
Â
Departament de Quõmica Fõsica i Inorganica, Universitat Rovira i Virgili, Pl. Imperial Tarraco 1, 43005 Tarragona, Spain
Â
Á
Á
Received 25 November 1999; accepted 11 February 2000
Abstract
Rh(I) and Ir(I) cationic complexes [M(cod)(PP)]BF4 have been synthesised from diphosphite ligands 4±6
derived from ribofuranose. They have been used in the rhodium and iridium catalysed asymmetric hydro-
genation of acrylic acid derivatives. Ribose derivative ligands 4±6 have also been used as auxiliaries in the
Rh-catalysed hydroformylation of styrene. Hydroformylation results have been explained on the basis of
the species formed under hydroformylation conditions. Comparative experiments with the related epimer
d-(+)-xylose derivatives showed that the con®guration of the product is controlled by the absolute con-
®guration of the stereogenic carbon atom C-3. # 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction
Ever since the early seventies there has been a great deal of interest in the asymmetric hydro-
formylation of several functionalised alkenes1±3 whose chiral aldehydes can be used as starting
material for the synthesis of ®ne chemicals.4,5 Platinum±diphosphane complexes are highly
enantioselective hydroformylation catalysts, but low chemo- and regioselectivity have been
obtained.6±8 During the last decade considerable attention has been devoted to phosphites as
suitable ligands for hydroformylation catalysts.9±14 One of the major advantages of phosphites is
that they are easy to prepare and are not as sensitive to air as phosphanes.15,16 Moreover they
enable the selectivity of the hydroformylation reaction to be tuned to linear or branched pro-
ducts.17±19 Excellent enantioselectivities have been recently obtained with Rh±diphosphite and
Rh±phosphane±phosphite hydroformylation catalysts.9±11
The asymmetric hydrogenation of prochiral compounds catalysed by transition-metal com-
plexes that contain chiral phosphorus ligands has been extensively used in organic synthesis20±22
and some processes have found applications in industry.23±25 Very little attention, however, has
been paid to diphosphites as ligands in asymmetric hydrogenation.
* Corresponding author. Tel: (+34)-977559572; fax: (+34)-977559563; e-mail: aruiz@quimica.urv.es
0957-4166/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(00)00061-6

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1098
In recent studies, sugar derived ligands showed good conversions and excellent enantio-
selectivities in di€erent types of catalytic reactions, e.g. hydrogenation,26,27 hydrocyanation,28 allylic
alkylation,29 which demonstrate their potential utility. However, the potential of the carbo-
hydrate chiral pool for providing chiral diphosphites has hardly been exploited.27,30±32 One of the
most successful families of sugar diphosphites applied in hydroformylation is the 1,2-O-iso-
propylidene-a-xylofuranose derivatives 1±3 (Scheme 1).31 These ligands have also shown good
conversions and moderate enantioselectivities in the hydrogenation of acrylic acid derivatives.33
This paper discusses the results of the related and previously reported epimeric ribose deriva-
tives32 4±6 in the asymmetric hydrogenation and hydroformylation of prochiral ole®ns. They
provide further information about how the chirality of the sugar backbone is transferred to the
products.
Scheme 1.
2. Results and discussion
2.1. Rhodium and iridium complexes
Carbohydrate diphosphites 4±6 react readily with [M(cod)2]BF4 (M=Rh, Ir) in dichloro-
methane, even with a large excess of diphosphite, to provide high yields of the corresponding
[M(cod)(PP)]+ cationic complexes (Scheme 2).
Scheme 2. Synthesis of complexes [M(cod)(PP)]BF4 7±12

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The 31P NMR spectra of the rhodium complexes showed two signals split into clearly resolved
double doublets due to the 31P,103Rh and 31P,31P couplings, except for complex 8, which showed
only one doublet because the chemical shifts of both phosphorus atoms accidentally coincide for
a single isomer or for di€erent species in ¯uxional behaviour on the NMR time-scale. The iridium
complexes 10±12 showed two doublets due to the 31P,31P coupling. When the temperature was
lowered, none of the rhodium or iridium complexes showed any splitting, which indicates that
only one isomer is present, unlike the related xylofuranose derivatives, for which two isomers
were observed.33 In the case of complex 8, it suggests also that the presence of only one doublet
for the two phosphorus atoms is caused by an accidental isocronicity.
2.2. Hydrogenation of acrylic acid derivatives
Cationic complexes [M(cod)(PP)]+ (M=Rh, Ir; PP=4±6) 7±12 have been used in the asym-
metric hydrogenation of itaconic acid 13 and a-methyl(acetamido)acrylic ester 14 under mild
conditions. Conversion and enantioselectivity results are shown in Table 1.
The [Rh(cod)(PP)]+ 7±9 complexes gave better conversions in toluene/methanol than in CH2Cl2/
methanol while the [Ir(cod)(PP)]+ complexes 10±12 were more ecient in CH2Cl2/methanol, as
previously observed for the related catalyst precursors that contain the epimer ligands 1±3.33
The introduction of tert-butyl groups onto the ortho positions in the diphosphites produces an
important e€ect on rate and enantioselectivity. In contrast with the results reported by Reetz and
Neugebauer27 conversions are higher for the precursors which contain the bulky and electron-rich
ligands 2±3 (entries 3 and 5 versus 1; entries 8 and 10 versus 7). This is probably because they
favour the oxidative addition reactions in the catalytic cycle.33 The best enantioselectivities for
the rhodium-catalysed hydrogenation of itaconic acid are obtained for precursor 7, which con-
tains the less hindered ligand 4 (entries 1 and 2).
Substrate 13 was hydrogenated with higher rates than substrate 14 for all catalytic precursors.
For itaconic acid 13 the iridium complexes 11±12 were more active at 1 bar of H2 than their
rhodium counterparts. It is important to note that the sense of the enantioselectivity inductions
obtained with iridium precursors 11 and 12 were opposite to those obtained with their rhodium
counterparts 8 and 9. For enamide 14 the enantiomeric excesses obtained with the iridium com-
plexes were higher than those obtained with the rhodium catalysts.
The catalytic precursors with ribose diphosphites 4±6 are generally less active and enantio-
selective than the related with the epimers derived from d-(+)-xylose 1±3.33 For itaconic acid the
sense of the enantioselectivity was generally the same as with the catalytic precursors containing
d-(+)-xylose-derivative ligands. However, for the acrylic ester derivative 14 the opposite direc-
tion was always obtained.
2.3. Hydroformylation of styrene and derivatives
Diphosphites 4±6 have been used in the rhodium-catalysed asymmetric hydroformylation of
styrene (Table 2). The catalysts were prepared in situ under typical hydroformylation conditions
(40ꢀC, 25 bar, 16 h) before the substrate was added.34,35
For all ligands regioselectivity for the branched aldehyde (88±98%) is good. As expected, the
enantioselectivity varies according to the substitution of the ligand. Enantioselectivities were high
with the catalyst containing ligands 5 and 6, which have bulky tert-butyl substituents at the ortho
positions of the bisphenol moieties (entries 2 and 3 versus 1).

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1100
Table 1
Hydrogenation of prochiral substrates with [M(cod)(PP)]BF4 7±12, M=Rh, Ir
Replacement of tert-butyl by methoxy substituent at the para positions of the present bisphenol
moiety produces somewhat higher enantioselectivities (entry 2 versus 3).
The highest enantiomeric excess (up to 61%) was achieved using ligand 5 at 25ꢀC but the
reaction rate turned to an impractically low value (entry 4).
For comparison purposes, hydroformylation experiments under the same conditions were car-
ried out with the previously reported xylose diphosphites.31 Ligands based on 1,2-O-iso-
propylidene-xylofuranose containing a tert-butyl group in ortho positions gave (S)-aldehydes,
while ligands with ribofuranose backbone gave (R)-aldehydes with similar enantioselectivities
(entries 6 and 7 versus 2 and 3). These opposite asymmetric inductions and the similar conver-
sions and regioselectivities suggest that the absolute con®guration at the stereogenic carbon atom

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1101
Table 2
Hydroformylation resultsa
C-3 produces an overall opposite absolute structure of the hydroformylation catalysts and hereby
induces opposite enantioselectivities.
Introduces di€erent groups in para position in the substrate does not seem to a€ect the con-
version, regioselectivitity or enantioselectivity of the hydroformylation (entries 6, 8 and 9).
2.4. Characterisation of [HRh(PP)(CO)2] complexes
Hydrido rhodium diphosphite dicarbonyl complexes, which are generally considered to be
active catalysts,9±14 were prepared from a starting rhodium precursor such as [Rh(acac)(CO)2] by
adding 1 equivalent of diphosphite under hydroformylation conditions (Scheme 3).
Scheme 3. Synthesis of complexes [HRh(PP)(CO)2] 15±17
The solution structures of hydridorhodium diphosphite dicarbonyl catalysts [HRh(PP)(CO)2],
1
PP=diphosphite ligand, were studied by H and 31P HP NMR spectroscopy.11,31,34 Table 3

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1102
Table 3
1
Selected H and 31P NMR data for hydrido-carbonyl rhodium complexes 16 and 17
shows the selected data obtained for complexes 16 and 17. Fairly long reaction times (4±8 h) at 25
bar syngas were needed for the complete formation of [HRh(PP)(CO)2]. Shorter reaction times
revealed the formation of intermediate species as side products in the 31P NMR spectra with
phosphorus±rhodium coupling constants around 300 Hz.11
At 298 K the 31P HP NMR spectra for hydrido dicarbonyl complexes 16 and 17 showed a
broad eight-line spectrum (Áo1/2 around 30 Hz) due to the 31P,31P and 31P,103Rh couplings (ABX
system). The same broad NMR pattern is observed at low temperature (298±203 K). These
suggest ¯uxional processes on the NMR time scale. This was con®rmed by measuring the 31P NMR
spectra at 333 K which showed sharp signals (Áo1/2 around 10 Hz) (Fig. 1). The large values for
the 1JP±Rh are characteristic of phosphite ligands coordinated in an equatorial position.11,31

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O. Pamies et al. / Tetrahedron: Asymmetry 11 (2000) 1097±1108
1103
Figure 1. 31P{1H} HP NMR spectrum of compound 16 at 333 K
The 1H NMR spectra in the hydride region revealed a broad signal between 333 and 203 K for
complexes 16 and 17, due to the small coupling constants of hydrogen with rhodium and with the
two phosphorus atoms.
1
The 31P and H NMR data are consistent with the presence of two diastereoisomers, whose
diphosphites coordinate bisequatorially to the rhodium in a fast exchange on the NMR time scale.
Complex 15 containing ligand 4 showed several catalytic hydride rhodium species in di€erent
proportions. This is due to the presence of di€erent atropoisomers of the bisphenol moiety in the
diphosphite ligand. The ambient temperature 31P NMR spectrum for the major diastereoisomer
showed the expected eight-line spectrum for an ABX system. The simulation of these signals
1
a€ords the two phosphorus atoms located at 169.2 (2JP±P=324 Hz, JP±Rh=278 Hz) and 172.3
1
ppm (1JP±Rh=261 Hz). The H NMR for this isomer in the hydride region revealed a double
2
triplet at 9.9 ppm (1JRh±H=5.4 Hz, JP±H=32.4 Hz), not the expected double double doublet,
because the coupling constants with the two non-equivalent phosphorus atoms located in equa-
torial position coincide. The relatively large phosphorus±hydride coupling constant is indicative
of a distorted trigonal bipyramidal hydride complex.31
3. Experimental
3.1. General comments
All syntheses were performed by standard Schlenk techniques under a nitrogen or argon
36
36
atmosphere. The complexes [Rh(cod)2]BF4 and [Ir(cod)2]BF4 and the diphosphites 1±331 and
4±632 were prepared by previously described methods. Solvents were puri®ed by standard procedures.
All other reagents were used as commercially available. Elemental analyses were performed on a

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O. Pamies et al. / Tetrahedron: Asymmetry 11 (2000) 1097±1108
1104
1
Perkin±Elmer 240 B instrument. H, 13C{1H} and 31P{1H} NMR spectra were recorded on a
Variant Gemini 300 MHz spectrometer. Chemical shifts are relative to SiMe4 (1H and 13C) as
internal standard or H3PO4 (31P) as external standard. All assignments in NMR spectra were
determined by means of COSY and HETCOR spectra. EI Mass spectra were obtained on a HP
5989 A spectrometer. VG-Autospect equipment was used for FAB mass spectral analyses. The
matrix was m-nitrobenzylalcohol. Gas chromatographic analyses were run on a Hewlett±Packard
HP 5890A instrument (split/splitless injector, J&W Scienti®c, Ultra-2 25 m column, internal dia-
meter 0.2 mm, ®lm thickness 0.33 mm, carrier gas: 150 kPa He, F.I.D. detector) equipped with a
Hewlett±Packard HP 3396 series II integrator. Hydroformylation reactions were carried out in a
home-made 100 mL stainless steel autoclave. Enantiomeric excesses were measured after oxida-
tion of the aldehydes to the corresponding carboxylic acids on a Hewlett±Packard HP 5890A gas
chromatograph (split/splitless injector, J&W Scienti®c, FS-Cyclodex b-I/P 50 m column, internal
diameter 0.2 mm, ®lm thickness 0.33 mm, carrier gas: 100 kPa He, F.I.D. detector). Absolute
con®guration was determined by comparing the retention times with enantiomerically pure (S)-2-
phenylpropionic and R-2-phenylpropionic acid derivatives. Hydrogenations at 5 bar were carried
out in a home-made 100 mL stainless steel autoclave. The reaction under 1 atm of H2 was per-
formed in a previously described hydrogen±vacuum line.37 The enantiomeric excesses for the
methylsuccinic acid were determined by polarimetry,38 while for N-acetylalanine methyl ester
they were determined by gas chromatography using an l-Chirasil-Val column.
3.2. Preparation of cationic complexes
3.2.1. General procedure
Diphosphite ligand (0.1 mmol) was added to a solution of [M(cod)2](BF4) (0.1 mmol; M=Rh,
40.5 mg; M=Ir, 49.4 mg) in 2 mL of dichloromethane. After 10 min, the desired products were
obtained by precipitation with hexane.
3.2.1.1. [Rh(cod)(4)]BF4 7. 81 mg (89%, yellow solid). Elemental analysis. Found (%): C,
52.05; H, 4.48. Calculated (%) for C40H40BF4O9P2Rh: C, 52.42; H, 4.40. FAB spectrometry: m/z:
2
1
829 [M+]. 31P NMR (CDCl3), ꢀ (ppm): 137.64 (dd, 1P, JP±P=49.5 Hz, JP±Rh=253.9 Hz),
2
1
1
137.77 (dd, 1P, JP±P=49.5 Hz, JP±Rh=251.9 Hz). H NMR (CDCl3), ꢀ (ppm): 1.31 (s, 3H,
CH3), 1.41 (s, 3H, CH3), 1.82 (m, 2H, CH2), 1.98 (m, 2H, CH2), 2.44 (m, 2H, CH2), 2.84 (m, 2H,
CH2), 4.31 (m, 1H, H-4), 4.48 (m, 1H, H-50), 4.90 (m, 1H, H-5), 5.05 (dd, 1H, H-2, 3J2±1=3.0 Hz,
3J2±3=3.6 Hz), 5.32 (m, 1H, CHˆ), 5.51 (M, 1H, CHˆ), 5.68 (m, 1H, H-3), 6.03 (d, 1H, H-1,
3J1±2=3.0 Hz), 6.21 (m, 2H, CHˆ), 7.2±7.6 (m, 16H, arom.). 13C NMR (CDCl3), ꢀ (ppm): 26.3
(CH3), 26.6 (CH3), 29.3 (CH2), 30.5 (CH2), 30.6 (CH2), 67.5 (C-5), 74.6 (t, C-4, JP±C=3.8 Hz),
78.8 (t, C-3, JP±C=4.0 Hz), 79.2 (d, C-2, JP±C=2.3 Hz), 104.2 (C-1), 107.6 (m, CHˆ), 109.4 (m,
CHˆ), 111.4 (m, CHˆ), 112.0 (m, CHˆ), 113.6 (CMe2), 121.3, 122.0, 122.1, 125.9, 126.7, 127.1,
127.2 (CHˆ), 128.8 (C), 129.7 (CHˆ), 129.8 (C), 129.9 (CHˆ), 130.0 (C), 130.2, 130.4, 130.7,
130.9 (CHˆ).
3.2.1.2. [Rh(cod)(5)]BF4 8. 105 mg (87%, yellow solid). Elemental analysis. Found (%): C,
.
55.98; H, 6.36. Calculated (%) for C60H80BF4O13P2Rh 1/2CH2Cl2: C, 55.75; H, 6.27. FAB
spectrometry: m/z: 1175 [M+]. 31P NMR (CDCl3), ꢀ (ppm): 123.8 (d, 1JRh±P=255 Hz). 1H NMR
t
(CDCl3), ꢀ (ppm): 1.20 (s, 3H, CH3), 1.35 (s, 3H, CH3), 1.47 (s, 18H, CH3 Bu), 1.68 (s, 9H, CH3
tBu), 1.70 (s, 9H, CH3 Bu), 1.92 (m, 2H, CH2), 2.19 (m, 2H, CH2), 2.28 (m, 2H, CH2), 2.32 (m,
t

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O. Pamies et al. / Tetrahedron: Asymmetry 11 (2000) 1097±1108
1105
2H, CH2), 3.27 (dd, 1H, H-2, J2±1=3.3 Hz, J2±3=3.0 Hz), 3.49 (m, 1H, H-50), 3.81 (s, 12H,
OMe), 3.92 (m, 1H, H-5), 4.42 (m, 2H, H-3, H-4), 5.18 (m, 1H, CHˆ), 5.41 (m, 1H, CHˆ), 5.43
(d, 1H, H-1, 3J1±2=3.3 Hz), 6.20 (m, 1H, CHˆ), 6.29 (m, 1H, CHˆ), 6.60 (m, 2H, CHˆ, arom),
6.69 (m, 1H, CHˆ, arom.), 6.74 (m, 1H, CHˆ, arom.), 7.04 (m, 4H, CHˆ, arom.). 13C NMR
3
3
t
(CDCl3), ꢀ (ppm): 25.5 (CH3), 26.3 (CH3), 27.7 (CH2), 28.5 (CH2), 32.0 (CH3, Bu), 32.1 (CH3,
t
t
t
t
tBu), 32.2 (CH3, Bu), 35.3 (C, Bu), 35.4 (C, Bu), 35.6 (C, Bu), 55.7 (OCH3), 69.8 (dd, C-5,
JP±C=9.7 Hz, JP±C=3.5 Hz), 71.2 (t, C-4, JP±C=4.0 Hz), 77.0 (C-2), 77.3 (dd, C-3, JP±C=5.1 Hz,
JP±C=2.8 Hz), 101.5 (m, CHˆ), 102.8 (m, CHˆ), 103.1 (C-1), 109.7 (m, CHˆ), 112.9 (CHˆ),
113.2 (CMe2), 113.7, 114.3, 114.7, 115.5, 115.9 (CHˆ), 128.0, 131.3, 131.9 (C), 132.4 (CHˆ),
141.9, 142.3, 142.9, 156.5, 156.7, 157.3 (C).
3.2.1.3. [Rh(cod)(6)]BF4 9. 120 mg (88%, yellow solid). Elemental analysis. Found (%): C,
.
62.36; H, 7.57. Calculated (%) for C72H104BF4O9P2Rh 1/2CH2Cl2: C, 61.91; H, 7.52. FAB
spectrometry: m/z: 1277 [M+]. 31P NMR (CDCl3), ꢀ (ppm): 122.7 (dd, 1P, 2JP±P=26.7 Hz, 1JP±Rh
266.6 Hz), 123.6 (dd, 1P, 2JP±P=26.7 Hz, 1JP±Rh=265.3 Hz). 1H NMR (CDCl3), ꢀ (ppm): 1.11 (s,
=
t
t
t
3H, CH3), 1.37 (m, 39H, CH3, CH3 Bu), 1.48 (m, 18H, CH3 Bu), 1.62 (m, 18H, CH3 Bu), 1.81
(m, 2H, CH2), 2.20 (m, 2H, CH2), 2.45 (m, 2H, CH2), 2.62 (m, 2H, CH2), 3.21 (dd, 1H, H-2,
3J2±1=2.7 Hz, 3J2±3=2.4 Hz), 3.48 (m, 1H, H-50), 3.92 (m, 1H, H-5), 4.44 (m, 2H, H-3, H-4), 5.15
3
(m, 1H, CHˆ), 5.37 (d, 1H, H-1, J1±2=2.7 Hz), 5.44 (m, 1H, CHˆ), 6.18 (m, 1H, CHˆ), 6.31
(m, 1H, CHˆ), 7.17 (m, 2H, CHˆ), 7.21 (m, 2H, CHˆ), 7.52 (m, 4H, CHˆ). 13C NMR (CDCl3),
t
t
ꢀ (ppm): 26.3 (CH3), 26.4 (CH3), 27.7 (CH2), 28.7 (CH2), 31.2 (CH3, Bu), 31.3 (CH3, Bu), 31.6
t
t
t
t
t
t
(CH3, Bu), 32.3 (CH3, Bu), 32.4 (CH3, Bu), 34.6 (C, Bu), 35.3 (C, Bu), 35.4 (C, Bu), 69.3
(d, C-5, JP±C=14.8 Hz), 70.9 (d, C-3, JP±C=6.2 Hz), 77.2 (d, C-2, JP±C=3.4 Hz), 77.4 (m, C-4),
101.8 (m, CHˆ), 102.7 (C-1), 103.2 (m, CHˆ), 109.9 (m, CHˆ), 113.4 (CMe2), 124.8, 125.2, 125.4,
126.2, 127.4, 128.0, 128.5 (CHˆ), 130.2 (C), 130.8 (CHˆ), 131.3, 139.9, 140.5, 148.5, 148.9, 149.5
(C).
3.2.1.4. [Ir(cod)(4)]BF4 10. 82 mg (83%, white solid). Elemental analysis. Found (%): C,
47.77; H, 4.12. Calculated (%) for C40H40BF4IrO9P2: C, 47.82; H, 4.32. FAB spectrometry: m/z:
919 [M+]. 31P NMR (CDCl3), ꢀ (ppm): 104.8 (s). 31P NMR (CDCl3, 233 K), ꢀ (ppm): 103.1 (d,
2
1
2JP±P=54 Hz), 105.9 (d, JP±P=54 Hz). H NMR (CDCl3), ꢀ (ppm): 1.24 (s, 3H, CH3), 1.41 (s,
3H, CH3), 1.80±2.80 (m, 8H, CH2), 3.80±4.70 (m, 5H, H-2, H-3, H-5, H-50), 5.31 (m, 2H, CHˆ),
5.52 (d, 1H, H-1, 3J1±2=3.9 Hz), 5.57 (m, 2H, CHˆ), 6.80±7.80 (m, 16H, CHˆ).
3.2.1.5. [Ir(cod)(5)]BF4 11. 109 mg (87%, red solid). Elemental analysis. Found (%): C,
.
54.58; H, 6.56. Calculated (%) for C60H80BF4IrO13P2 1/2CH2Cl2: C, 54.36; H, 6.71. FAB spec-
2
trometry: m/z: 1263 [M+]. 31P NMR (CDCl3), ꢀ (ppm): 113.6 (d, 1P, JP±P=43.1 Hz), 114.9 (d,
2
1
1P, JP±P=43.1 Hz). H NMR (CDCl3), ꢀ (ppm): 1.25 (s, 3H, CH3), 1.40 (s, 3H, CH3), 1.54 (s,
18H, CH3 tBu), 1.64 (s, 18H, CH3 tBu), 2.05 (m, 4H, CH2), 2.30 (m, 2H, CH2), 2.56 (m, 2H,
CH2), 3.22 (dd, 1H, H-2, J2±1=3.3 Hz, J2±3=3.6 Hz), 3.59 (m, 1H, H-50), 3.82 (s, 12H, OMe),
3
3
4.00 (m, 1H, H-5), 4.45 (m, 2H, H-3, H-4), 4.84 (m, 1H, CHˆ), 5.08 (m, 1H, CHˆ), 5.40 (d, 1H,
3
H-1, J1±2=3.3 Hz), 6.03 (m, 1H, CHˆ), 6.14 (m, 1H, CHˆ), 6.65 (m, 2H, CHˆ), 6.77 (m, 2H,
CHˆ), 7.05 (m, 4H, CHˆ). 13C NMR (CDCl3), ꢀ (ppm): 25.9 (CH3), 26.7 (CH3), 28.4 (CH2), 29.3
(CH2), 31.0 (CH2), 31.9 (CH3, tBu), 32.3 (CH3, tBu), 32.6 (CH3, tBu), 32.9 (CH3, tBu), 35.9 (C, tBu),
36.0 (C, tBu), 56.2 (OCH3), 70.6 (d, C-5, JP±C=14.3 Hz), 71.8 (d, C-3, JP±C=6.8 Hz), 77.6 (C-2),
78.2 (d, C-4, JP±C=13.7 Hz), 92.3 (d, CHˆ, JC±P=16.6 Hz), 93.7 (d, CHˆ, JC±P=16.5 Hz), 101.4

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1106
(d, CHˆ, JC±P=13.2 Hz), 101.7 (d, CHˆ, JC±P=13.2 Hz), 103.7 (C-1), 113.6 (CHˆ), 113.9
(CMe2), 114.7, 115.1, 115.4, 115.5, 115.9, 116.5 (CHˆ), 129.2, 131.8, 132.4, 132.5, 132.9, 142.6,
142.7, 142.9, 157.0, 157.3, 157.8, 157.9 (C).
3.2.1.6. [Ir(cod)(6)]BF4 12. 140 mg (89%, red solid). Elemental analysis. Found (%): C,
59.54; H, 7.45. Calculated (%) for C72H104BF4IrO9P2: C, 59.45; H, 7.21. FAB spectrometry: m/z:
2
2
1365 [M+]. 31P NMR (CDCl3), ꢀ (ppm): 112.7 (d, 1P, JP±P=43.1 Hz), 113.3 (d, 1P, JP±P=43.1
1
t
Hz). H NMR (CDCl3), ꢀ (ppm): 1.24 (s, 18H, CH3 Bu), 1.32 (s, 3H, CH3), 1.47 (m, 3H, CH3),
1.56 (m, 18H, CH3 tBu), 1.78 (m, 18H, CH3 tBu), 1.90 (m, 18H, CH3 tBu), 2.02 (m, 4H, CH2),
2.37 (m, 4H, CH2), 3.04 (dd, 1H, H-2, 3J2±1=3.3 Hz, 3J2±3=3.1 Hz), 3.50 (m, 1H, H-50), 3.87 (m,
1H, H-5), 4.39 (m, 2H, H-3, H-4), 4.72 (m, 1H, CHˆ), 5.01 (m, 1H, CHˆ), 5.24 (d, 1H, H-1,
3J1±2=3.3 Hz), 5.88 (m, 1H, CHˆ), 6.02 (m, 1H, CHˆ), 7.04 (m, 2H, CHˆ), 7.15 (m, 2H, CHˆ),
7.46 (m, 4H, CHˆ). 13C NMR (CDCl3), ꢀ (ppm): 26.9 (CH3), 29.5 (CH2), 29.7 (CH2), 31.0 (CH2),
t
t
t
t
31.7 (CH3, Bu), 32.2 (CH3, Bu), 32.6 (CH3, CH2), 32.7 (CH3, Bu), 32.8 (CH3, Bu), 33.1 (CH3,
tBu), 35.1 (C, Bu), 35.2 (C, Bu), 35.9 (C, Bu), 36.0 (C, Bu), 70.2 (dd, C-5, JP±C=12.6 Hz,
JP±C=1.8 Hz), 71.6 (dd, C-3, JP±C=5.7 Hz, JP±C=2.9 Hz), 77.8 (d, C-2, JP±C=3.4 Hz), 78.3 (dd,
C-4, JP±C=11.4 Hz, JP±C=2.9 Hz), 92.5 (dd, CHˆ, JP±C=13.7 Hz, JP±C=2.3 Hz), 93.9 (dd, CHˆ,
JP±C=13.7 Hz, JP±C=2.1 Hz), 101.2 (d, CHˆ, JP±C=6.3 Hz), 101.4 (d, CHˆ, JP±C=5.7), 103.5
(C-1), 114.1 (CMe2), 125.5, 125.9, 126.1, 126.9, 128.1, 128.2, 128.6, 129.1 (CHˆ), 130.8 (C), 131.5
(CHˆ), 131.7, 131.8, 140.5, 140.7, 141.2, 149.1, 149.5, 149.7, 150.2 (C).
t
t
t
t
3.3. Hydroformylation of styrene
The autoclave was purged three times with CO. The solution was formed from [Rh(acac)(CO)2]
(0.013 mmol) and diphosphite (0.017 mmol) in toluene (10 mL). After pressurising to the desired
pressure with syngas and heating the autoclave to the reaction temperature, the reaction mixture
was stirred for 15 h to form the active catalyst. The autoclave was depressurised and a solution of
substrate (13 mmol) in toluene (5 mL) was brought into the autoclave and pressurised again.
During the reaction several samples were taken from the autoclave. After the desired reaction
time, the autoclave was cooled to room temperature and depressurised. The reaction mixture was
analysed by gas chromatography. The aldehydes obtained from the hydroformylation were
oxidised to carboxylic acids to determine the enantiomeric excess.
3.4. In situ HP NMR characterisation of [HRh(CO)2(PP)]
In a typical experiment a sapphire tube (f=10 mm) was ®lled under argon with a solution of
[Rh(acac)(CO)2] (0.030 mmol) and ligand (molar ratio PRh=1.1) in toluene-d8 (1.5 mL). The HP
NMR tube was purged twice with CO and pressurised to the appropriate pressure of CO/H2.
After a reaction time of 16 h shaking at the desired temperature, the solution was analysed.
3.5. Hydrogenation experiments
The reactions were performed in a home-made autoclave. The autoclave was purged three
times with H2. In a typical run, catalytic precursor (0.02 mmol) and substrate (2 mmol) were
dissolved in the appropriate mixture of solvents (12 mL) and introduced in the purged autoclave.
After pressurising to the desired pressure with hydrogen and heating the autoclave to the reaction

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O. Pamies et al. / Tetrahedron: Asymmetry 11 (2000) 1097±1108
1107
temperature, the reaction mixture was stirred. After the desired reaction time, the autoclave was
cooled to room temperature and depressurised. The solvent was evaporated.
Acknowledgements
We thank the Spanish Ministerio de Educacion y Cultura and the Generalitat de Catalunya
(CIRIT) for ®nancial support (PB97-0407-CO5-01) and the Generalitat de Catalunya (CIRIT)
for awarding a research grant (to O.P.).
References
1. Botteghi, C.; Paganelli, S.; Schionato, A.; Marchettti, M. Chirality 1991, 3, 355.
2. Consiglio, G. Catalytic Asymmetric Synthesis; Ojima, I., Ed.; VCH: New York, 1993.
3. (a) Gladiali, S.; Bayon, J. C.; Claver, C. Tetrahedron: Asymmetry 1995, 6, 1453. (b) Agbossou, F.; Carpentier, J.-F.;
Mortreux, A. Chem. Rev. 1995, 95, 2485.
4. Rieu, J.-P.; Bouchelere, A.; Cousse, H.; Mouzin, G. Tetrahedron 1986, 42, 4095.
5. Sonawane, H. R.; Bellur, N. S.; Ahyja, J. R.; Kulkarni, D. G. Tetrahedron: Asymmetry 1992, 3, 163.
6. Parinello, G.; Stille, J. K. J. Am. Chem. Soc. 1987, 109, 7122.
7. Stille, J. K.; Su, H.; Brechot, P.; Parinello, G.; Hegedus, L. S. Organometallics 1991, 10, 1183.
8. Consiglio, G.; Nefkens, S. C. A.; Borer, A. Organometallics 1991, 10, 2046.
9. Babin, J. E.; Whiteker, G. T. WO 93/03839, US 911,518, 1992.
10. Nozaki, K.; Sakai, N.; Nanno, T.; Higashijima, T.; Mano, S.; Horiuchi, T.; Takaya, H. J. Am. Chem. Soc. 1997,
119, 4413 and references cited therein.
11. Buisman, G. J. H.; van der Veen, L. A.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. Organometallics 1997, 16,
5681 and references cited therein.
12. Fernandez, E.; Ruiz, A.; Claver, C.; Castillon, S.; Polo, A.; Piniella, J. F.; Alvarez Larena, A. Organometallics
1998, 17, 2857.
13. Cserepi-Suzcs, S.; Toth, I.; Parkanyi, L.; Bakos, J. Tetrahedron: Asymmetry 1998, 9, 3135.
14. Jiang, Y.; Xue, S.; Li, Z.; Deng, J.; Mi, A.; Chan, A. S. C. Tetrahedron: Asymmetry 1998, 9, 3185.
15. Pignolet, L. H. Homogeneous Catalysis with Metal Phosphine Complexes; Plenum: New York, 1983.
16. Baker, M. J.; Harrison, N. K.; Orpen, A. G.; Pringle, P. G.; Show, G. J. Chem. Soc., Chem. Commun. 1991, 803.
17. van Rooy, A.; Orij, E. N.; Kamer, P. C. J.; van der Aardweg, F.; van Leeuwen, P. W. N. M. J. Chem. Soc., Chem.
Commun. 1991, 1096.
18. Knok, T. J.; Wink, D. J. Organometallics 1993, 12, 1954.
19. Cuny, G. D.; Buchwald, S. L. J. Am. Chem. Soc. 1993, 115, 2066.
20. Takaya, H.; Onta, T.; Noyori, R. Catalytic Asymmetric Synthesis; Ojima, I., Ed.; VCH: New York, 1993;
Chapter 1.
21. Noyori, R. Asymmetric Catalysis in Organic Synthesis; Wiley: New York, 1994; Chapter 2.
22. Brunner, H. Topics in Stereochemistry; Wilen, S. H., Ed.; John Wiley & Sons: New York, 1988, 18, 129.
23. Akutagawa, S. Asymmetric Hydrogenation with Ru-BINAP: Chirality in Industry; Collins, A. N.; Sheldrake, G. N.;
Crosby, J., Eds.; Wiley: Chichester, 1992.
24. Kotha, S. Tetrahedron 1994, 50, 3639.
25. Akutagawa, S. Appl. Catal., A Gen. 1995, 128, 171.
26. Selke, R. J. Organomet. Chem. 1989, 370, 241.
27. Reetz, M. T.; Neugebauer, T. Angew. Chem., Int. Ed. 1999, 38, 179.
28. RajanBabu, T. V.; Casalnuovo, A. L. Pure Appl. Chem. 1994, 94, 149.
29. Yonehara, K.; Hashizuma, T.; Mori, K.; Ohe, K.; Uemura, S. Chem. Commun. 1999, 415.
30. Kadyrov, R.; Heller, D.; Selke, R. Tetrahedron: Asymmetry 1998, 9, 329.
31. Buisman, G. J. H.; Martin, M. E.; Vos, E. J.; Klootwijk, A.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. Tetra-
hedron: Asymmetry 1995, 6, 719.

Á
O. Pamies et al. / Tetrahedron: Asymmetry 11 (2000) 1097±1108
1108
32. Pamies, O.; Net, G.; Ruiz, A.; Claver, C. Tetrahedron: Asymmetry 1999, 10, 2007.
33. Pamies, O.; Net, G.; Ruiz, A.; Claver, C. Eur. J. Inorg. Chem., in press.
34. Buisman, G. J. H.; Vos, E. J.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. J. Chem. Soc., Dalton Trans. 1995, 409.
35. van Rooy, A.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Goubitz, K. J.; Fraanje, J.; Veldman, N.; Spek, A. L.
Organometallics 1996, 15, 835.
36. Green, M.; Kuc, T. A.; Taylor, S. H. J. Chem. Soc., A 1971, 2334.
37. Cativiela, C.; Fernandez, J.; Mayoral, J. A.; Melendez, E.; Uson, R.; Oro, L. A.; Fernandez, M. J. J. Mol. Catal.
1982, 16, 19.
38. Lafont, D.; Sinou, D.; Descotes, G. J. Organomet. Chem. 1979, 169, 87.