Diphosphines based on an inherently chiral calix[4]arene scaffold: Synthesis and use in enantioselective catalysis

Article abstract of DOI:10.1039/b101369f

A series of calix[4]arenes bearing two phosphorus pendent groups p-Bu^t-calix[4]arene-25,26-[CH₂P(O)Ph₂] ₂-27-(OR¹)-28-(OR²) (R^{1 or 2} = CH₂CO₂Et, R^{2 or 1} = H,2; R¹ = R² = CH₂CO₂Et, 3; R ^{1 or 2} = C(O)Ocholesteryl, R^{2 or 1} = H, 4; R¹ = R² = C(O)Ocholesteryl, 5; R^{1 or 2} = (R)-CH₂C(O)NHCMe(Ph)H, R^{2 or 1} = H, 6) and p-Bu^t-calix[4]arene-25,26-(CH₂PPh₂) ₂-27-(OR¹)-28-(OR²) (R¹ = (R)-CH₂ C(O)NHCMe(Ph) H, R² = H,7; R¹ = (R)- CH₂C(O)NHCMe(Ph)H, R² = SiMe₃, 8; R¹ = (R)-CH₂C(O)NHCMe(Ph)H, R² = (R)-CH₂C(O)NHCMe(Ph)H, 10) have been synthesised. The enantiomerically pure calixarenes 7,8 and 10 having an AABC substitution pattern are inherently chiral. Reaction of the latter three diphosphines with [Pd(2-Me-allyl)(THF)₂]]BF₄ (THF = tetrahydrofuran) afforded the chelate complexes [Pd(2-Me-allyl)(diphosphine)]BF₄ 11-13, respectively, while reaction with [Rh(NBD)(THF)₂]BF₄ (NBD = norbornadiene) resulted in quantitative formation of the complexes [Rh(NBD)(diphosphine)]BF₄ 14-16, respectively. As a result of allyl rotation, the palladium complexes 11-13 exist in solution as two interconverting species. These complexes efficiently catalyse the alkylation of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate, the turnovers beingca. 30 h^-1. Enantioselectivity was shown to depend on the size difference between the B and C substituents. Thus, while virtually no induction was observed with the chiral calixarene 10 bearing two identical substituents, ee's of 45% and 67% respectively were observed with 12 and 11, which have a more marked dissymmetry. Similar trends were observed in the catalytic hydrogenation of dimethyl itaconate with the rhodium complexes 14-16, leading to ee's of 48%, 25% and 0%, respectively. Related chiral calixarenes in which the two phosphine arms occupy proximal instead of distal phenolic positions were found to be considerably less effective in catalysis of both allylic alkylation and hydrogenation.

Full text of DOI:10.1039/b101369f

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Diphosphines based on an inherently chiral calix[4]arene scaffold:
synthesis and use in enantioselective catalysis
Cedric Dieleman, Stéphane Steyer, Catherine Jeunesse and Dominique Matt
Université Louis Pasteur, Laboratoire de Chimie Inorganique Moléculaire, 1 rue Blaise Pascal,
F-67008 Strasbourg Cedex, France. E-mail: dmatt@chimie.u-strasbg.fr
Received 12th February 2001, Accepted 12th June 2001
First published as an Advance Article on the web 8th August 2001
A series of calix[4]arenes bearing two phosphorus pendent groups p-But-calix[4]arene-25,26-[CH2P(O)Ph2]2-27-(OR1)-
28-(OR2) (R1 or 2 = CH2CO2Et, R2 or 1 = H, 2; R1 = R2 = CH2CO2Et, 3; R1 or 2 = C(O)Ocholesteryl, R2 or 1 = H, 4;
R1 = R2 = C(O)Ocholesteryl, 5; R1 or 2 = (R)-CH2C(O)NHCMe(Ph)H, R2 or 1 = H, 6) and p-But-calix[4]arene-25,26-
(CH2PPh2)2-27-(OR1)-28-(OR2) (R1 = (R)-CH2C(O)NHCMe(Ph) H, R2 = H, 7; R1 = (R)-CH2C(O)NHCMe(Ph)H,
R2 = SiMe3, 8; R1 = (R)-CH2C(O)NHCMe(Ph)H, R2 = (R)-CH2C(O)NHCMe(Ph)H, 10) have been synthesised. The
enantiomerically pure calixarenes 7, 8 and 10 having an AABC substitution pattern are inherently chiral. Reaction
of the latter three diphosphines with [Pd(2-Me-allyl)(THF)2]BF4 (THF = tetrahydrofuran) afforded the chelate
complexes [Pd(2-Me-allyl)(diphosphine)]BF4 11–13, respectively, while reaction with [Rh(NBD)(THF)2]BF4
(NBD = norbornadiene) resulted in quantitative formation of the complexes [Rh(NBD)(diphosphine)]BF4 14–16,
respectively. As a result of allyl rotation, the palladium complexes 11–13 exist in solution as two interconverting
species. These complexes efficiently catalyse the alkylation of 1,3-diphenylprop-2-enyl acetate with dimethyl
malonate, the turnovers being ca. 30 hϪ1. Enantioselectivity was shown to depend on the size difference between
the B and C substituents. Thus, while virtually no induction was observed with the chiral calixarene 10 bearing two
identical substituents, ee’s of 45% and 67% respectively were observed with 12 and 11, which have a more marked
dissymmetry. Similar trends were observed in the catalytic hydrogenation of dimethyl itaconate with the rhodium
complexes 14–16, leading to ee’s of 48%, 25% and 0%, respectively. Related chiral calixarenes in which the two
phosphine arms occupy proximal instead of distal phenolic positions were found to be considerably less effective
in catalysis of both allylic alkylation and hydrogenation.
were all obtained by lower-rim functionalisation of the pre-
Introduction
viously described di(phosphine oxide) 1.20 The conformational
Calix[4]arenes are remarkable building blocks which have
assignments were made using empirical NMR methods which
become useful in many areas of synthetic chemistry.1,2 This
are now well-established.20,28 In the present paper, the phenolic
development mainly rests on the particular architecture of the
substituents without a phosphorus atom will be termed
calix[4]arene framework. The latter provides a circular platform
auxiliary groups. It should be mentioned here that, to date,
which permits several functional groups to be oriented in the
calixarene-derived phosphanes have only sparingly been used
same direction and thus to generate sophisticated micro-
for catalytic purposes.29–35
environments organized around a central core.3 Such polytopic
ligands have found many practical applications, notably as
selective cation binders,4–6 molecular sensors,7–10 and container
molecules11,12 as well as highly ordered materials.13–15
Our recent work in this field has been centred on the design
and synthesis of P()-functionalised calix[4]arenes and their
use in transition metal chemistry.16–20 We have described some
chiral phosphanes which were obtained from calix[4]arenes
to which a chiral moiety had been attached on the lower rim
prior to P()-functionalisation.21 In terms of enantioselectivity
the catalytic properties of these ligands were rather disappoint-
ing, presumably because the asymmetric carbon atoms were
located too far from the catalytic centre and/or because the
chiral dangling groups were not fixed in a rigid manner with
respect to the calix scaffold. In the present work we report on
the synthesis and catalytic properties of new optically active
phosphines built on inherently chiral22 calix[4]arene units
possessing an AABC substitution pattern. We also describe the
X-ray structure of an enantiomerically pure di(phosphine
oxide) based on such a framework.
Results and discussion
Synthesis of chiral ligands
Substitution of a single phenolic oxygen in 1 generates an
inherently chiral calix[4]arene. The possibility of achieving
monofunctionalisation was first assessed by carrying out the
alkylation reaction shown in eqn. (1), using 1.0 equiv. of
BrCH2CO2Et and 0.5 equiv. of K2CO3. This reaction afforded
the monoalkylated compounds 2a and 2b (racemic mixture) in
44% yield together with small amounts of the dialkylated
derivative 3 (10%). The racemate 2 was separated from 3 by
Although inherently chiral calixarenes have been known
for some time23–25 and have also been resolved in several
instances,26,27 catalytic properties of ligands derived from such
structures remain unreported. The ligands described herein
2508
J. Chem. Soc., Dalton Trans., 2001, 2508–2517
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b101369f

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(1)
column chromatography. As could be unambiguously deduced
from the 1H and 13C NMR spectra, compounds 2 and 3 adopt a
cone conformation (see Experimental section). Attempts to
improve the yield of the monofunctionalised compound were
unsuccessful.
Higher yields were obtained in the monofunctionalisation
of 1 using cholesteryl chloroformate–NEt3. The carbonates
thus formed, 4a and 4b, were obtained in ca. 70% yield. Both
isomers contain a chiral cholesteryl fragment as part of an
inherently chiral calix[4]arene and hence are diastereomers. As
inferred from the 31P NMR spectrum, the two diastereomers
were formed in a ca. 1 : 1 ratio. The NMR data are again in
keeping with cone conformations. Separation of these two
isomers by column chromatography proved to be never better
than partial, their Rf values being very close. Note, during the
synthesis of 4a/4b (4), small amounts of the dicholesteryl com-
pounds 5a/5b (diastereomeric mixture 5) were also formed.
They could be separated from 4 but again the two components
5a and 5b could not be separated from each other. The form-
ation of both diastereomers (ca. 1 : 1 ratio) was deduced from
the 1H NMR spectrum which shows two distinct ABX systems
for one CH2 group. The assignment of a partial cone structure
1
to 5 was made on the basis of the H and 13C spectra. The
former shows four AB systems for the ArCH2 groups, two
of them displaying a large AB separation (∆δ = ca. 1.8 ppm),
the other two a considerably smaller one (∆δ = 0.51 ppm and
0.27 ppm). Corroborating these observations, the 13C NMR
spectrum displays four ArCH2 signals, two appearing at >37
ppm, the other two at <33 ppm. The latter values are in agree-
ment with ArCH2Ar fragments containing aryl rings which are
respectively anti- and syn-oriented.
Seeking reagents which allow both mono-functionalisation of
1 and convenient product separation, we reacted 1 with (ϩ)-
(R)-BrCH2C(O)NHCHMePh in the presence of 0.5 equiv. of
K2CO3. The diastereomers formed, 6a and 6b, could readily be
separated by column chromatography, the yields after work-up
being respectively 29% and 26%. The absolute configuration of
6a was determined by a single crystal X-ray diffraction study.
This (Fig. 136) also confirmed the cone conformation of the
calixarene. The macrocyclic framework adopts the usual shape
for a calix[4]arene in the cone conformation, with angles
between the opposite phenoxy rings of 6Њ and 72Њ, respectively.
Fig. 1 Molecular structure of the chiral di(phoshine oxide) 6a (for
clarity only the ipso carbon atoms of the PPh2 groups are shown).
A striking feature of the structure is the short N ؒ ؒ ؒ O(17) sep-
aration (3.157(3) Å), which is consistent with the presence of a
hydrogen-bonded NH group. As found in other compounds,
the P᎐O bonds are oriented tangentially with respect to the
᎐
cavity defined by the calix substituents.16
Reduction of compound 6a with PhSiH3 resulted in the
formation of the optically active diphosphine 7, eqn. (2). The
1H and 31P NMR spectra show that 7 exists in solution as a
10 : 1 mixture of two interconverting isomers. Owing to the
J. Chem. Soc., Dalton Trans., 2001, 2508–2517
2509

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diphosphine 10 in which the cone conformation is retained. The
two NH protons of 10 appear at 7.24 ppm and 6.91 ppm, sug-
gesting that the NH groups are no longer involved in hydrogen
bonding.
Synthesis of cationic palladium–(2-Me-allyl) and rhodium–
(2)
(norbornadiene) complexes
The palladium complexes 11–13 were prepared in high yield by
reaction of [Pd(Me-allyl)(THF)2]BF4 with the ligands 7, 8 and
10, respectively (eqn. (5)). These complexes were authenticated
1
complexity of the H NMR spectrum, only the conformation
of the major isomer could unambiguously be established as a
cone by 13C NMR. We assign a partial cone conformation to
the second isomer, considering the very facile through-the-
annulus motion of phenoxy rings bearing small substituents.37
It is well known that conformational inversion can be inhibited
by incorporating sufficiently large substituents on the lower
rim.38 Thus, alkylation of the 7-cone/7-partial cone mixture
with Me3SiCl–NEt2SiMe3 (eqn. (3)) afforded calixarene 8 which
(5)
(3)
by elemental analysis and FAB mass spectroscopy. As revealed
by a variable temperature 31P NMR study, each complex exists
in solution as a mixture of two interconverting isomers (11a/
11b; 12a/12b; 13a/13b). The NMR data indicate that these
isomers must have a very similar structure. This observation
may be interpreted in terms of allyl fluxionality giving two
distinct isomers with different orientations of the Callyl–Me
bond (Scheme 1). Conformational change within the pallado-
proved to exist exclusively as a cone conformer. The formation
of a single conformer is consistent with the fact that the
precursors forming 7 are equilibrating species. As expected, the
31P NMR spectrum of 8 shows two inequivalent P() atoms
(Ϫ21.0 ppm and Ϫ21.4 ppm). The cone conformation of 8 was
inferred from the 13C NMR spectrum, in which all ArCH2Ar
signals lie below 33 ppm.
For the present study we also prepared the chiral di(phos-
phine oxide) 9, bearing two identical, chiral substituents. This
phosphine precursor was obtained in 75% yield by double
alkylation with (R)-BrCH2C(O)NHCHMePh. The NMR data
of 9 are in full agreement with a cone conformation. As
1
expected for a calixarene having no symmetry, the H NMR
spectrum of 9 shows four distinct ArCH2Ar groups while its 31
P
NMR spectrum displays two well-separated singlets (27.6 ppm
and 24.8 ppm) in the phosphine oxide region. It is noteworthy
that the two NH signals (at 8.93 ppm and 8.83 ppm) are
considerably downfield-shifted with respect to those of
BrCH2C(O)NHCHMePh (6.74 ppm), presumably because of
hydrogen-bonding between the NH protons and the phos-
phoryl groups (in CDCl3). Using PhSiH3, compound 9 could
be reduced quantitatively (eqn. (4)) to the corresponding
Scheme 1
macrocycle could in principle also account for the observed
equilibrium, but such a phenomenon is unlikely since in
related, non-allylic [PtCl2(calix-diphos)] complexes,20 no
dynamics of the metallocyclic unit were observed. It should
also be mentioned here that, as expected, all three 31P NMR
spectra display AB systems with coupling constants in accord
with cis-arranged P atoms (35–40 Hz). While complexes 11 and
13 could unambiguously be identified as cone conformers,
conformational assignment was not made for isomers 12a/12b
owing to the complexity of the NMR spectra.
For the preparation of the chelate complexes 14–16,
[RhCl(NBD)]2 (NBD = norbornadiene) was used as precursor
(Scheme 2). The latter was first treated with AgBF4 in a CH2Cl2–
THF mixture, resulting in formation of a cationic intermediate
which was separated from silver chloride before being reacted
with the particular disphosphine. For each complex, the 31P
NMR spectrum displays a single AB pattern with a coupling
constant in agreement with cis-bonded phosphorus atoms
(ca. 30 ppm). Significantly, the largest peak separation
(4)
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J. Chem. Soc., Dalton Trans., 2001, 2508–2517

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Table 1 Palladium-catalysed alkylation of 1,3-diphenylprop-2-enyl
acetate
complexes 12 and 11, respectively. These observations suggest
that the presence of asymmetric carbon atoms as the only
source of chirality has little influence on the selectivity. For
comparison, we also evaluated the chiral complexes 17–2042
which are all based on non-inherently chiral calixarenes con-
taining either one or two asymmetric carbon atoms integrated
in the auxiliary groups. Note that in these calixarenes the two P
atoms are tethered to distal positions. Complexes 17–20 gave
poor enantioselectivities (Table 1), the best ee’s being only 16%.
It is also noteworthy that in the presence of BSA–KOAc–
CH2Cl2 the activity of these complexes, ca. 6 hϪ1, was lower
than that reported above for 11–13. However, we observed an
increase of the reaction rate when performing the catalytic runs
with NaH in refluxing THF instead of BSA–KOAc–CH2Cl2,
the ee’s remaining unchanged. The low ee’s observed with 13
and 17–20 may be explained by the large separation between the
stereogenic centre(s) and the metal unit, and the flexibility of
the pendent amide, which both prevent effective induction. In
contrast, an inherently chiral calix[4] backbone, as found in 11
and 12, induces higher ee’s.
Complex
Reaction time/h
Conversion (%)
ee’s (%)
TOFc
11a
12a
13a
17b
18b
19b
20b
3.3
3.3
3.8
4
3
5
100
100
100
100
100
100
100
67
45
0
8
16
6
30
30
26
25
33
20
33
3
2
a Reaction conditions: 0.012 mmol catalyst, 1.2 mmol allylacetate, 2.4
mmol BSA, 2.4 mmol dimethyl malonate, 0.06 mmol KOAc; T = 0 ЊC;
solvent: CH2Cl2. b Reaction conditions: 0.012 mmol catalyst, 1.2 mmol
allylacetate, 2.4 mmol dimethyl malonate, 2.4 mmol NaH; T = 67 ЊC;
solvent: THF. c Turnover frequency in hϪ1. For the complexes 17–20 we
observed an increase of the reaction rate when performing the catalytic
runs with NaH in refluxing THF instead of BSA–KOAc–CH2Cl2, but
the ee’s remained unchanged.
Scheme 2
(δPA Ϫ δPB ≈ 20 ppm!) was observed for the calixarene bearing
the sterically most disparate substituents (i.e. OH and OCH2-
C(O)NHCHMePh), namely complex 14. For comparison,
the signal separation is only 1 ppm in complex 16 having sub-
stituents equal in size, and 8 ppm in 15 containing the SiMe3
and CH2C(O)NHCHMePh groups. Obviously the large peak
separation observed in 14 reflects a strong “perturbation” of
one of the two phosphino groups, possibly caused by a steric
interaction with the adjacent amide group.
As inferred from the 13C NMR spectra, the calixarene units
in 14–16 are in a cone conformation. It should be emphasized
that each rhodium complex exists as a single isomer. This find-
ing further supports the interpretation given for the equilibrium
observed in complexes 11–13, involving allyl dynamics rather
than structural changes within the metallocyclic unit.
Catalytic properties of 11–13 (allylic alkylation) and 14–16
(hydrogenation)
The three diphosphines 14–16 were also used in catalytic
olefin-hydrogenation. Thus, dimethyl itaconate is easily reduced
with complex 16, as expressed by a turnover frequency of 267
The catalytic activity of complexes 11–13 was assessed in the
alkylation of 1,3-diphenylprop-2-enyl acetate with dimethyl
malonate in the presence of BSA (BSA = Me3SiOC(NSiMe3)-
CH3). For this reaction a Pd : acetate ratio of 1 : 100 was used.
Operating at 0 ЊC, complete substrate conversion occurred in
less than 4 hours with all three complexes, corresponding to
a turnover frequency of ca. 30 hϪ1 (Table 1). These activities
compare well with that of other effective palladium-based
alkylation catalysts.39–41 Remarkably, while no asymmetric
induction was observed with complex 13 bearing two identical
chiral substituents, ee’s of 45% and 67% were obtained with
h
Ϫ1 (Table 2). However, no asymmetric induction was observed,
presumably again because of the long distance between the
chiral carbons and the coordinated substrate. We note, however,
that the catalytic activity of this complex is significantly higher
than that observed for the related complex 21 (TOF: 10 hϪ1).21
It is plausible that, in the latter, the pocket-like metal environ-
ment hinders somewhat the access of the incoming olefin. The
rate of hydrogenation significantly increases when using
complexes 14 and 15. The observed turnover frequencies
are respectively 2000 and 1176 hϪ1, while the corresponding
J. Chem. Soc., Dalton Trans., 2001, 2508–2517
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Table 2 Rhodium-catalysed hydrogenation of dimethyl itaconatea
phosphinomethoxy)calix[4]arene]}rhodium() tetrafluorobo-
rate 21,21 [Pd(2-Me-allyl)Cl]2,43 [RhCl(NBD)]2,44 1,3-diphenyl-
propenylacetate45 and Me3SiNEt2,46 were prepared by using
literature procedures.
Complex
Reaction time/h
Conversion (%)
ee’s (%)
TOFb
14
15
16
21
0.10
0.17
0.75
20
100
100
100
100
48
25
0
2000
1176
267
10
X-Ray crystallography
0
Crystals suitable for diffraction study were obtained by slow
diffusion of tetrahydrofuran into a dichloromethane solution
of the compound.
a Reaction conditions: 0.02 mmol catalyst, 4.0 mmol dimethyl itaconate,
P
= 20 bar, T = 40 ЊC; solvent: MeOH. b Turnover frequency in hϪ1
.
H2
Crystal data for 6aؒMeOH. C81H93NO8P2, M = 1270.59, tri-
clinic, space group P1, colourless prisms, a = 10.3100(3),
enantioselectivities are 48% and 25%. We have no definitive
explanation for the increased activity of these complexes with
respect to that of 16, but it is possible that the steric interaction
between the metallocyclic unit and the auxiliary substituents
decreases when the size of the latter become smaller. The net
result is then that the steric interaction between the whole calix-
arene and the metal centre decreases, making the rhodium more
accessible for an incoming olefin. On the other hand, the
increased enantioselectivity observed with 14 and 15 suggests
that the calix backbone effectively transfers to the metal centre
the high steric anisotropy which characterises the domain com-
prising the two auxiliary groups. As in the allylic alkylation
reactions described above, the more different the auxiliary
groups are in size, the higher the chiral induction is. The better
chirality transfer observed with calixarenes 7 and 8 may imply
involvement of the phenyl substituents of the P atoms. Whether
this occurs via direct steric interaction or via a backbone distor-
tion is not clear at this stage.
In summary, we have described the first optically active
diphosphines based on an inherently chiral calix[4]arene
framework. For one of them, 6a, the absolute configuration has
been established by a single crystal X-ray diffraction study.
Ligands 6a and 7 display good activities when used as allylic
alkylation and hydrogenation catalysts. The catalytic properties
of the ligands have been compared to those of related diphos-
phines where the only sources of chirality are asymmetric
carbon atoms belonging to the auxiliary groups. Our findings
clearly indicate that in terms of activity, the calixarenes which
possess two proximal –CH2PPh2 groups are superior to those
having the phosphines appended to distal positions. Moreover,
the inherently chiral calixarenes gave enantioselectivities
significantly higher than those induced by the other ligands
studied, suggesting that a chiral calix skeleton is able to effect-
ively transfer the chiral information to the catalytic centre,
while the presence alone of chiral C atoms located within the
side chains has no significant influence on the selectivity. It
appears likely that increasing the size difference between the
two auxiliary groups should result in higher ee’s.
¯
b = 13.1130(6), c = 15.0380(6) Å, α = 109.403(2), β = 96.716(3),
γ = 97.714(3)Њ, U = 1871.6(3) Å3, Z = 1, Dc = 1.13 g cmϪ3
,
µ = 0.112 mmϪ1, F(000) = 680. Data were collected on a Nonius
KappaCCD diffractometer (graphite Mo-Kα radiation,
0.71073 Å) at Ϫ100 ЊC. 13115 Reflections collected with
(2.5 < θ < 28.05Њ), 5065 data with I > 3σ(I ). The structure was
solved by direct methods and refined anisotropically on F 2
using the OpenMoleN package.47 Absolute structure was
determined refining Flack’s x (0.02(7)) parameter. Hydrogen
atoms were included using a riding model or rigid methyl
groups. Two But groups (C(7) and C(55)) are disordered over
two positions. Some disorder was also found in the methanol
solvate. Final results: R(F) = 0.041, wR(F) = 0.056, goodness of
fit = 1.061, 826 parameters, largest difference peak = 0.288 e
ÅϪ3
.
CCDC reference number 157446.
See http://www.rsc.org/suppdata/dt/b1/b101369f/ for crystal-
lographic data in CIF or other electronic format.
Syntheses
5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphinoyl-
methoxy)-27(or
28)-ethoxycarbonylmethoxy-28(or
27)-
(hydroxy)calix[4]arene 2a and 2b (racemic mixture). A suspen-
sion of 1 (2.000 g, 1.86 mmol) and K2CO3 (0.140 g, 1.01 mmol)
in acetonitrile (100 cm3) was refluxed for 4 hours. Ethyl
bromoacetate (0.310 g, 1.86 mmol) was added and the mixture
refluxed for a further 4 days. The solvent was evaporated and
the residue dissolved in CH2Cl2 (50 cm3). The organic layer was
washed with HCl 1 M (20 cm3) and water (2 × 20 cm3). The
organic layer was dried over MgSO4, then filtered and evap-
orated. The residue was purified by flash chromatography using
AcOEt–hexane (50 : 50, v/v) as eluent. Compounds 2a and 2b
(racemic mixture) were obtained as an analytically pure colour-
less powder (SiO2, Rf = 0.37, AcOEt–hexane, 50 : 50, v/v).
Yield: 0.941 g, 0.81 mmol, 44%; mp >220 ЊC; IR (KBr, cmϪ1):
1
ν(C᎐O) = 1736. H NMR (400 MHz, CDCl ): δ 7.91–7.79 and
᎐
3
7.52–7.21 (20H, P(O)Ph2), 7.06 and 7.01 (AB spin system, 2H,
m-ArH, 4J = 2.3 Hz), 6.88 and 6.72 (AB spin system, 2H,
Experimental
4
m-ArH, J = 2.4 Hz), 6.86 (s, 1H, OH exchanges with D2O),
4
General procedures can be taken from ref. 20. Samples of 5,11,
17,23-tetra-tert-butyl-25,26-dihydroxy-27,28-bis(diphenylphos-
phinoylmethoxy)calix[4]arene 1,16 (ϩ)-(R)-BrCH2C(O)NHCH-
MePh,21 (η3-2-methylallyl)-(P,PЈ)-[5,11,17,23-tetra-tert-butyl-
25,27-bis{(1R,2S,5R)-menthyloxycarbonylmethoxy}-26,28-bis-
(diphenylphosphinooxy)calix[4]arene]palladium() tetrafluor-
oborate 17,42 (R,R)-(η3-2-methylallyl)-(P,PЈ)-{5,11,17,23-tetra-
tert-butyl-25,27-bis[(1-phenylethyl)carbamoylmethoxy]-26,28-
bis(diphenylphosphinomethoxy)calix[4]arene}palladium()
tetrafluoroborate 18,42 (R)-(η3-2-methylallyl)-(P,PЈ)-{5,11,17,-
23-tetra-tert-butyl-25-(3-oxabutyloxy)-27-[(1-phenylethyl)carb-
amoylmethoxy]-26,28-bis(diphenylphosphinomethoxy)calix[4]-
arene}palladium() tetrafluoroborate 19,42 (η3-2-methlylallyl)-
(P,PЈ)-[5,11,17,23-tetra-tert-butyl-25,27-bis{(1R,2S,5R)-men-
thyloxycarbonylmethoxy}-26,28-bis(diphenylphosphinometh-
oxy)calix[4]arene]palladium() tetrafluoroborate 20,42 (nor-
bornadiene){cis-(P,PЈ)-(R,R)-[5,11,17,23-tetra-tert-butyl-25,-
27-bis[(1-phenylethyl)carbamoylmethoxy]-26,28-bis(diphenyl-
6.69 and 6.63 (AB spin system, 2H, m-ArH, J = 2.4 Hz), 6.33
4
and 6.23 (AB spin system, 2H, m-ArH, J = 2.3 Hz), 5.58 and
5.22 (ABX spin system with X = P, 2H, P(O)CH2, 2J(AB) = 14.9
Hz, 2J(AX) = 4.1 Hz, 2J(BX) = 4.0 Hz), 5.24 and 3.16 (AB spin
system, 2H, ArCH2Ar, 2J = 12.9 Hz), 5.04 and 4.19 (AB
spin system, 2H, OCH2CO2, 2J = 15.7 Hz), 4.84 and 4.55 (ABX
spin system with X = P, 2H, P(O)CH2, 2J(AB) = 13.5 Hz,
2J(AX) = 0 Hz, 2J(BX) = 8.6 Hz), 4.59 and 3.01 (AB spin
2
system, 2H, ArCH2Ar, J = 13.5 Hz), 4.48 and 3.15 (AB spin
system, 2H, ArCH2Ar, 2J = 12.7 Hz), 4.35 and 3.26 (AB
spin system, 2H, ArCH2Ar, 2J = 13.6 Hz), 4.03 (q, 2H,
CH2CH3, 3J = 7.1 Hz), 1.31 (s, 9H, C(CH3)3), 1.22 (s, 9H,
C(CH3)3), 1.15 (t, 2H, CH2CH3, 3J = 7.1 Hz), 0.92 (s, 9H,
C(CH3)3), 0.65 (s, 9H, C(CH3)3). 13C{1H} NMR (50 MHz,
CDCl3): δ 169.50 (s, CO2), 153.29–124.77 (aryl C), 73.81
(d, P(O)CH2, J(PC) = 82 Hz), 72.31 (s, CH2CO2), 70.71 (d,
P(O)CH2, J(PC) = 75 Hz), 60.51 (s, CH2CH3), 33.97 (s,
C(CH3)3), 33.86 (2s, C(CH3)3), 33.56 (s, C(CH3)3), 31.84 (s,
2512
J. Chem. Soc., Dalton Trans., 2001, 2508–2517

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ArCH2Ar), 31.83, 31.60, 31.08 and 30.98 (4s, C(CH3)3), 14.21
(s, CH2CH3) (only a single ArCH2Ar signal could be detected).
31P{1H} NMR (121 MHz, CDCl3): δ 26.2 (s), 25.5 (s). Found:
C, 72.16; H, 7.39. Calc. for C74H84O8P2 (Mr = 1163.40): C, 72.40;
H, 7.28%. Small amounts of compound 3 were also formed. A
rational, high yield synthesis of the latter is given below.
(m, 1H, H-3), 4.48 and 3.24 (AB spin system, 2H, ArCH2Ar,
2J(AB) = 13.4 Hz), 4.44 and 3.00 (AB spin system, 2H,
2
ArCH2Ar, J(AB) = 12.9 Hz), 4.05 and 3.25 (AB spin system,
2H, ArCH2Ar, 2J(AB) = 13.1 Hz), 2.57–0.69 (43H, cholesteryl),
1.25 and 1.24 (2s (two diastereomers), 9H, C(CH3)3), 1.20 and
1.18 (2s (two diastereomers), 9H, C(CH3)3), 0.85 and 0.82 (2s
(two diastereomers), 9H, C(CH3)3), 0.83 (s, 9H, C(CH3)3).
13C{1H} NMR (50 MHz, CDCl3): δ 153.97–131.95 (quaternary
aryl C), 131.57–124.89 (aryl C), 122.86 (s, C-6), 78.35 (s, C-3),
73.25 (d, J(PC) = 78.0 Hz, P(O)CH2), 71.46 (d, J(PC) = 74.9
Hz, P(O)CH2), 56.79 (s, C-14), 56.24 (s, C-17), 50.04 (s, C-9),
42.41 (s, C-13), 39.83 (s, C-12 tentative assignment), 39.60 (s,
C-1 tentative assignment), 38.10 (s, CH2), 36.95 (s, CH2), 36.62
(s, C-10), 36.28 (s, CH2), 35.87 (s, CH), 34.00 (s, C(CH3)3), 33.84
(2s, C(CH3)3), 33.73 (s, C(CH3)3), 32.65 (s, ArCH2Ar), 32.43
(s, ArCH2Ar), 31.97 (s, C-7 tentative assignment), 31.75 (s,
C(CH3)3), 31.57 (s, C(CH3)3), 31.05 (2s, C(CH3)3), 28.32
(s, C-16), 28.09 (s, CH), 27.78 (s, CH2), 24.38 (s, CH2), 23.91 (s,
CH2), 22.91 (s, CH3), 22.66 (s, CH3), 21.15 (s, C-11), 19.52 (s,
CH3), 18.82 (s, CH3), 11.97 (s, CH3). 31P{1H} NMR (121 MHz,
CDCl3): δ 25.37 (2s), 25.25 and 25.00 (2s, two diastereomers).
FAB mass spectrum: m/z 1490.0 ([M ϩ H]ϩ, 51%). Found: C,
79.13; H, 8.32. Calc. for C98H122O8P2 (Mr = 1489.96): C, 79.00;
H, 8.25%. The numbering used for the cholesteryl atoms is as in
ref. 48.
5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphinoyl-
methoxy)-27,28-bis(ethoxycarbonylmethoxy)calix[4]arene 3. A
suspension of 1 (0.500 g, 0.464 mmol) and K2CO3 (0.080 g,
0.579 mmol) in acetonitrile (30 cm3) was refluxed for 2 hours.
Ethyl bromoacetate (0.235 g, 1.41 mmol) was then added and
the mixture refluxed for a further 72 hours. The solvent was
evaporated and the residue dissolved in CH2Cl2 (50 cm3). The
organic layer was washed with HCl 1 M (20 cm3) and water
(2 × 20 cm3). The organic layer was dried over MgSO4,
then filtered and evaporated. Drying the residue at 100 ЊC
under vacuum for 24 hours afforded analytically pure 3. Yield:
0.530 g, 0.424 mmol, 91%; mp >240 ЊC; IR (KBr, cmϪ1):
1
ν(C᎐O) = 1757. H NMR (200 MHz, CDCl ): δ 7.95–7.79 and
᎐
3
7.42–7.29 (20 H, P(O)Ph2), 6.73 and 6.69 (AB spin system, 4H,
m-ArH, 4J = 2.3 Hz), 6.48 and 6.39 (AB spin system, 4H,
4
m-ArH, J = 2.2 Hz), 5.52 and 5.07 (ABX spin system with
X = P, 4H, P(O)CH2, 2J(AB) = 14.8 Hz, 2J(AX) = 0 Hz,
2J(BX) = 0 Hz), 4.82 and 3.10 (AB spin system, 4H, ArCH2Ar,
2J = 12.7 Hz), 4.74 and 2.77 (AB spin system, 2H, ArCH2Ar,
2J = 13.0 Hz), 4.71 and 3.07 (AB spin system, 2H, ArCH2Ar,
2J = 13.1 Hz), 4.64 and 4.46 (AB spin system, 4H, CH2CO2,
5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphinoyl-
methoxy)-27,28-bis(cholesteryloxycarbonyloxy)calix[4]arene
(partial cone) 5a and 5b (mixture of diastereomers). Trace
amounts of this compound were obtained in the synthesis of
4a/4b, after chromatography. Recrystallisation from CH2Cl2–
MeOH afforded a white microcrystalline powder. Yield: 0.232
3
2J = 16.0 Hz), 4.09 (q, 4H, CH2CH3, J = 7.1 Hz), 1.20 (t, 6H,
CH2CH3), 1.04 (s, 18H, C(CH3)3), 0.97 (s, 18H, C(CH3)3).
13C{1H} NMR (50 MHz, CDCl3): δ 170.68 (s, CO2), 153.18–
125.06 (aryl C), 71.73 (d, J(PC) = 77 Hz, P(O)CH2), 71.25
(s, CH2CO2), 60.13 (s, CH2CH3), 33.82 (s, C(CH3)3), 33.73 (s,
C(CH3)3), 32.18 (s, ArCH2Ar), 31.38 (s, C(CH3)3), 14.26 (s,
CH2CH3), (only a single ArCH2Ar signal could be detected).
31P{1H} NMR (121 MHz, CDCl3): δ 24.7 (s). FAB mass
spectrum: m/z 1249.6 ([M ϩ H]ϩ, 76%). Found: C, 74.97; H,
7.51. Calc. for C78H90O10P2 (Mr = 1249.49): C, 74.98; H, 7.26%.
g, 0.122 mmol, 3%; mp 189–199 ЊC; IR (KBr, cmϪ1): ν(C᎐
᎐
1
O) = 1749.7. H NMR (400 MHz, CDCl3): δ 7.98–7.05 (20H,
P(O)Ph2), 7.47 and 6.98 (AB spin system, 2H, m-ArH, 4J = 2.1
4
Hz), 6.79 and 6.24 (AB spin system, 2H, m-ArH, J = 2.4 Hz),
4
6.77 and 6.52 (AB spin system, 2H, m-ArH, J = 2.4 Hz), 6.72
and 6.32 (AB spin system, 2H, m-ArH, 4J = 1.5 Hz), 5.41
(broad signal, 2H, H-6), 5.34 and 4.01 (ABX spin system with
X = P, 2H, P(O)CH2, 2J(AB) = 15.3 Hz, 2J(AX) = 7.0 Hz,
2J(BX) = 7.2 Hz), 4.86 and 4.41 (ABX spin system with X = P,
2H, P(O)CH2, 2J(AB) = 14.2 Hz, 2J(AX) = 4.4 Hz, 2J(BX) = 4.6
(av.) Hz), 4.75 and 2.97 (AB spin system, 2H, ArCH2Ar, 2J = 14
5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphinoyl-
methoxy)-27(or 28)-(cholesteryloxycarbonyloxy)-28(or 27)-
(hydroxy)calix[4]arene 4a and 4b (mixture of diastereomers). A
solution of 1 (5.000 g, 4.64 mmol), cholesteryl chloroformate
(6.253 g, 13.92 mmol) and NEt3 (15 cm3) in CH2Cl2 (150 cm3)
was stirred at room temperature for 12 hours. The solution was
then washed with 50 cm3 HCl (1 M) and water (2 × 50 cm3).
The organic layer was dried over MgSO4, filtered and evap-
orated. The residue was purified by flash chromatography
using AcOEt–hexane (25 : 75, v/v) as eluent. Some cholesteryl
derivatives eluted first followed by 5 (SiO2, Rf = 0.31, AcOEt–
hexane, 25 : 75, v/v, for spectroscopic data see below). Further
elution gave 4a and 4b (diastereomeric mixture), (SiO2,
Rf = 0.19, AcOEt–hexane, 25 : 75, v/v). After evaporation, the
residue was taken up in CH2Cl2. Addition of methanol and
cooling at Ϫ78 ЊC afforded the product as a white microcrystal-
line powder. Yield: 4.770 g, 3.2 mmol, 69%; mp 178–181 ЊC;
2
Hz), 4.56 and 2.72 (AB spin system, 2H, ArCH2Ar, J = 14.2
Hz), 4.41 (m, 2H, H-3), 3.87 and 3.36 (AB spin system, 2H,
2
ArCH2Ar, J = 13.8 Hz), 3.76 and 3.49 (AB spin system, 2H,
ArCH2Ar, 2J = 13.8 Hz), 2.60–0.68 (86H, 2 × cholesteryl), 1.20
(s, 9H, C(CH3)3), 1.05 (s, 9H, C(CH3)3), 0.88 (s, 9H, C(CH3)3),
0.86 (s, 9H, C(CH3)3). Owing to the presence of two diastereo-
mers, the 1H NMR spectrum shows two ABX spin systems for
one PCH2 group. 13C{1H} NMR (50 MHz, CDCl3): δ 168.78
(CO), 154.85–132.53 (quaternary aryl C), 132.43–124.43 (aryl
C), 122.99 (s, C-6), 122.83 (s, C-6), 77.98 (s, C-3), 72.12 (d,
P(O)CH2, J(PC) = 80.3 Hz), 68.99 (d, P(O)CH2, J(PC) = 75.4
Hz), 56.71 (s, C-14), 56.15 (s, C-17), 49.99 (s, C-9), 42.32 (s, C-
13), 39.73 (s, C-12 tentative assignment), 39.53 (s, C-1 tentative
assignment), 37.96 (s, CH2), 37.83 (s, ArCH2Ar), 37.01 (s,
ArCH2Ar), 36.91 (s, CH2), 36.61 (s, C-10), 36.19 (s, CH2), 35.80
(s, CH), 33.83, 33.70, 33.40 (3s, C(CH3)3), 32.61 (s, ArCH2Ar),
31.96 (s, C-7 tentative assignment), 31.60, 31.47 (2s, C(CH3)3),
28.36 (s, C-16), 28.03 (s, CH), 27.63 (s, CH2), 24.29 (s, CH2),
23.83 (s, CH2), 22.81 (s, CH3), 22.55 (s, CH3), 21.04 (s, C-11),
19.18 (s, CH3), 18.72 (s, CH3), 11.87 (s, CH3). 31P{1H} NMR
(121 MHz, CDCl3): δ 26.21 (s), 25.21 (s). Found: C, 79.46; H,
8.58. Calc. for C126H166O10P2 (Mr = 1902.61): C, 79.54; H,
8.25%. Compound 5 was also formed by alkylation of a 4a/4b
mixture.
IR (KBr, cmϪ1): ν(C᎐O) = 1755 (owing to the presence of two
᎐
1
diastereomers, some signals are split). H NMR (500 MHz,
CDCl3): δ 7.99–7.65 and 7.50–7.29 (20H, P(O)Ph2), 7.01 and
6.89 (AB spin system, 2H, m-ArH, 4J(AB) = 3.8 Hz), 6.89
4
and 6.67 (AB spin system, 2H, m-ArH, J(AB) = 3.9 Hz), 6.62
4
and 6.58 (AB spin system, 2H, m-ArH, J(AB) = 3.8 Hz), 6.46
and 6.38 (AB spin system, 2H, m-ArH, 4J(AB) = 3.9 Hz and 4.6
Hz), 5.89 and 5.85 (2s (two diastereomers), 1H, OH, exchanges
with D2O), 5.73 and 4.72 (ABX spin system with X = P, 2H,
P(O)CH2, 2J(AB) = 14.6 Hz, 2J(AX) = 4.2 Hz, 2J(BX) = 6.1
3
Hz), 5.40 and 5.29 (2d (two diastereomers), 1H, H-6, J = 5.2
Hz), 5.00 and 4.84 (ABX spin system with X = P, 2H, P(O)CH2,
2
2
2J(AB) = 14.2 Hz, J(AX) = 4.4 Hz, J(BX) = 0 Hz), 4.90 and
(R)-5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphin-
oylmethoxy)-27(or 28)-[(1-phenylethyl)carbamoylmethoxy]-28-
2
2.93 (AB spin system, 2H, ArCH2Ar, J(AB) = 12.9 Hz), 4.54
J. Chem. Soc., Dalton Trans., 2001, 2508–2517
2513

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(or 27)-(hydroxy)calix[4]arene 6a and 6b (mixture of diastereo-
mers). A suspension of K2CO3 (0.115 g, 0.83 mmol) and 1
(1.500 g, 1.39 mmol) in MeCN (250 cm3) was refluxed for 3 h.
(R)-(ϩ)-2-Bromo-N-(1-phenylethyl)acetamide (0.371 g, 1.53
mmol) was added and the suspension was further refluxed for
48 h. After evaporation of the solvent, the residue was taken up
in CH2Cl2 (150 cm3). The solution was washed with 1 M HCl
(80 cm3), then with water (2 × 80 cm3). The organic layer was
dried with MgSO4, filtered and evaporated to dryness. The solid
residue was subjected to flash chromatography using the follow-
ing procedure: an AcOEt–hexane (1 : 1, v/v) mixture was used
first as eluent to remove a mixture of 1 (19%), 9 (29%) and 6b
(SiO2, Rf = 0.55, AcOEt–hexane, 1 : 1, v/v). Further elution
gave pure stereoisomer 6a (SiO2, Rf = 0.51, AcOEt–hexane,
1 : 1, v/v) obtained as a colourless solid. A second chrom-
atography was then performed on the 1/9/6b mixture using
CH2Cl2–MeOH (98 : 2, v/v) as eluent to remove unreacted 1
(SiO2, Rf = 0.53, CH2Cl2–MeOH, 98 : 2, v/v). However separ-
ation of the stereoisomer 6b was not achieved and a mixture of
6b and 9 was recovered (SiO2, Rf = 0.52, CH2Cl2–MeOH, 98 : 2,
v/v). Spectroscopic characterization of 6b: 31P{1H} NMR (202
MHz, 293 K, CDCl3): δ 25.9 (s) and 25.3 (s). Spectroscopic data
for 6a: Yield: 0.448 g, 26%; mp 190–191 ЊC; IR (KBr, cmϪ1):
J(PC) = 6 Hz, PCH2O), 75.93 (d, PCH2O, J(PC) = 11 Hz), 74.04
(s, OCH2C(O)N), 48.75 (s, NHCH(Me)Ph), 32.78, 32.70 and
32.34 (3s, ArCH2), 31.79, 31.71, 31.03 and 30.94 (4s, C(CH3)3),
22.52 (s, NHCH(CH3)Ph) (one ArCH2 signal is probably
overlapping with a tert-butyl signal). 31P{1H} NMR (121 MHz,
293 K, CDCl3): δ Ϫ20.4 and Ϫ20.7 (2s). Found: C, 79.50; H,
7.38; N, 1.23. Calc. for C80H89NO5P2 (Mr = 1206.51): C, 79.64;
H, 7.43; N, 1.16%.
(R)-5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphino-
methoxy)-27-[(1-phenylethyl)carbamoylmethoxy]-28-(trimethyl-
silyloxy)calix[4]arene 8. To a solution of 7 (1.000 g, 0.83 mmol)
in toluene (35 cm3) were added Me3SiNEt2 (0.240 cm3, 1.24
mmol) and small amounts of Me3SiCl. The solution was heated
to 60 ЊC for 2 h. The solvent was evaporated to dryness under
vacuum yielding a white solid which was subjected to flash
chromatography (pre-treated SiO2 with 5% NEt3 in CH2Cl2)
using AcOEt–hexane (8 : 92, v/v) as eluent. The fraction
obtained with Rf = 0.31 (SiO2–NEt3, AcOEt–hexane, 8 : 92, v/v)
was evaporated to dryness yielding 8 as a colourless powder.
Yield: 0.448 g, 90%; mp 201–203 ЊC; IR (KBr, cmϪ1):
ν(NH) = 3415br, ν(NH) = 3338br sh, ν(C᎐O) = 1677s. 1H NMR
᎐
(400 MHz, 293 K, CDCl3): δ 7.36–7.16 (m, 20H, PPh2), 7.09 (d,
3
ν(OH) = 3423br, ν(NH) = 3292br, ν(C᎐O) = 1669s, ν(P᎐O,
1H, NH, J = 7 Hz), 6.85–6.53 (m, 8H, m-ArH), 5.27 (AMX3
᎐
᎐
tentative assignment) = 1192s. 1H NMR (500 MHz, 293 K,
CDCl3): δ 9.17 (d, 3J = 7 Hz, 1H, NH), 7.96–7.91, 7.84–7.70 and
7.52–7.11 (m, 20H, PPh2), 7.02 and 6.98 (AB spin system, 2H,
m-ArH, 4J = 3 Hz), 6.92 and 6.83 (AB spin system, 2H, m-ArH,
system, 1H, NHCHMe(Ph), 3J(AM) = 3J(AX) = 7 Hz), 5.16
2
and 4.94 (ABX system with X = P, 2H, PCH2O, J(AB) = 14
2
2
Hz, J(AX) = 2 Hz, J(BX) = 4 Hz), 4.96 and 4.75 (AB spin
system, 2H, PCH2O, 2J = 13 Hz), 4.84 and 4.66 (AB spin
system, 2H, OCH2C(O)N, 2J = 14 Hz), 4.52 and 2.98 (AB
4
4J = 3 Hz), 6.57 and 6.51 (AB spin system, 2H, m-ArH, J = 3
4
2
Hz), 6.44 and 6.42 (AB spin system, 2H, m-ArH, J = 3 Hz),
spin system, 2H, ArCH2, J(AB) = 14 Hz), 4.50 and 3.03 (AB
2
5.89 and 4.94 (ABX spin system with X = P, 2H, PCH2O,
spin system, 2H, ArCH2, J = 13 Hz), 4.49 and 3.12 (AB spin
2
2
2J(AB) = 14 Hz, J(AX) = 0 Hz, J(BX) = 3 Hz), 5.26 and 3.03
system, 2H, ArCH2, 2J = 13 Hz), 4.28 and 2.82 (AB spin system,
(AB spin system, 2H, ArCH2Ar, 2J = 13 Hz), 5.16 (AMX3 spin
2H, ArCH2, J = 13 Hz), 1.50 (d, 3H, NHCH(CH3)Ph, J = 7
Hz), 1.16, 1.13, 1.06 and 1.04 (4s, 36H, tert-butyl), 0.29 (s, 9H,
SiMe3). 13C{1H} NMR (100 MHz, 293 K, CDCl3): δ 169.35 (s,
2
3
system, 1H, NHCHMe(Ph), JAM = 3JAX = 7 Hz), 5.15 (s, 1H,
3
OH), 4.83 and 4.65 (ABX system with X = P, 2H, PCH2O,
2
2
2J(AB) = 14 Hz, J(AX) = 2 Hz, J(BX) = 7 Hz), 4.65 and 3.02
(AB spin system, 2H, ArCH2Ar, 2J = 13 Hz), 4.28 and 3.10 (AB
spin system, 2H, ArCH2Ar, 2J = 13 Hz), 4.23 and 3.56 (AB spin
C᎐O), 153.41–131.06 (quaternary aryl C), 133.67–124.62 (aryl
᎐
CH), 76.93 and 76.18 (2d, PCH2O, J(PC) = 8 Hz), 73.51 (s,
OCH2C(O)N), 48.57 (s, NHCH(Me)Ph), 33.92, 33.87 and
33.79 (3s, C(CH3)3), 32.27, 32.26 and 31.56 (3s, ArCH2), 31.48,
31.39 and 31.27 (3s, C(CH3)3), 21.41 (s, NHCH(CH3)Ph) (one
ArCH2 signal is probably overlapping with a tert-butyl signal),
1.00 (s, SiMe3). 31P{1H} NMR (121 MHz, 293 K, CDCl3):
δ Ϫ21.0 and Ϫ21.4 (2s). Found: C, 77.79; H, 7.51; N, 1.16. Calc.
for C83H98NO5P2Si (Mr = 1279.70): C, 77.90; H, 7.72; N, 1.09%.
2
system, 2H, OCH2C(O)N, J = 14 Hz), 3.70 and 3.07 (AB spin
system, 2H, ArCH2, 2J = 13 Hz), 1.51 (d, 3H, NHCH(CH3)Ph,
3J = 7 Hz), 1.30, 1.23, 0.85 and 0.78 (4s, 36H, C(CH3)3).
13C{1H} NMR (100 MHz, 293 K, CDCl ): δ 168.69 (s, C᎐O),
᎐
3
154.34–129.35 (quaternary aryl C), 132.12–124.92 (aryl CH),
75.72 (s, OCH2C(O)N), 72.53 (d, PCH2O, J(PC) = 81 Hz),
72.05 (d, PCH2O, J(PC) = 77 Hz), 48.28 (s, NHCH(Me)Ph),
33.94, 33.86, 33.65 and 33.62 (4s, C(CH3)3), 31.98, 31.85 and
31.21 (3s, ArCH2), 31.66, 31.50 and 30.94 (3s, C(CH3)3), 21.20
(s, NHCH(CH3)Ph) (one ArCH2 signal is probably overlapping
with a C(CH3)3 signal). 31P{1H} NMR (202 MHz, 293 K,
CDCl3): δ 27.7 and 26.3 (2s). Found: C, 77.80; H, 7.33; N, 1.18.
Calc. for C80H89NO7P2 (Mr = 1238.51): C, 77.58; H, 7.24; N,
1.13%.
(R,R)-5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphos-
phinoylmethoxy)-27,28-bis[(1-phenylethyl)carbamoylmethoxy]-
calix[4]arene 9. A suspension of K2CO3 (5.130 g, 37.11 mmol)
and 1 (4.000 g, 3.71 mmol) in MeCN (350 cm3) was refluxed for
3 h. Then (R)-(ϩ)-2-bromo-N-(1-phenylethyl)acetamide (5.394
g, 1.53 mmol) was added and the suspension was refluxed for
7 d. After evaporation of the solvent, the residue was taken up
in CH2Cl2 (250 cm3), washed with 1 M HCl (120 cm3), then with
water (2 × 90 cm3). The organic layer was dried with MgSO4,
filtered and evaporated to dryness. The solid residue was sub-
jected to flash chromatography using AcOEt–hexane (2 : 3, v/v)
as eluent. Compound 9 was obtained as an analytically pure
colourless solid (SiO2, Rf = 0.42, AcOEt–hexane, 2 : 3, v/v).
Yield: 3.895 g, 75%; mp 165–166 ЊC; IR (KBr, cmϪ1):
(R)-5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphosphino-
methoxy)-27-[(1-phenylethyl)carbamoylmethoxy]-28-(hydroxy)-
calix[4]arene 7. A suspension of 6a (2.500 g, 2.02 mmol) in
phenylsilane (15 cm3, 121.56 mmol) was refluxed for 2 days.
After evaporation of the solvent in vacuo, the residue was sub-
jected to flash chromatography using CH2Cl2 as eluent. The
fraction obtained with Rf = 0.45 (SiO2, CH2Cl2) was evaporated
to dryness yielding 7 as a colourless powder. The NMR spectra
of the compound showed evidence for the presence of two
conformers (10 : 1 ratio) in solution. Owing to the complexity
of the NMR spectrum showing two equilibrating species, only
a selection of spectroscopic data are given for the major con-
former, 7-cone. Yield: 2.000 g, 82%; mp 175–177 ЊC; IR (KBr,
ν(NH) = 3430br sh, ν(NH) = 3300br, ν(C᎐O) = 1654s, ν(P᎐O,
᎐
᎐
tentative assignment) = 1200s. 1H NMR (400 MHz, 293 K,
3
CDCl3): δ 8.93 and 8.83 (2d, 2H, NH, J = 8 Hz), 7.93–7.88,
7.76–7.71 and 7.53–7.12 (m, 20H, PPh2), 6.68 and 6.66 (AB spin
system, 2H, m-ArH, 4J ≈ 1 Hz), 6.66 and 6.54 (AB spin system,
2H, m-ArH, 4J = 2 Hz), 6.50 and 6.41 (AB spin system, 2H, m-
4
ArH, J ≈ 1 Hz), 6.43 and 6.42 (AB spin system, 2H, m-ArH,
cmϪ1): ν(OH) = 3447br, ν(NH) = 3349br, ν(C᎐O) = 1677s. 1H
4J = 2 Hz), 6.01 and 4.92 (AB spin system, 2H, PCH2O,
2J(AB) = 14 Hz), 5.20 and 5.12 (2 AMX3 spin systems, 2H,
NHCHMe(Ph), 3J(AM) = 3J(AX) = 7 Hz), 5.12 and 5.05 (ABX
spin system with X = P, 2H, PCH2O, 2J(AB) = 12 Hz,
᎐
NMR (400 MHz, 293 K, CDCl3): δ 8.79 (d, 1H, NH, 3J = 8 Hz),
1.34, 1.31, 0.84 and 0.79 (4s, 36H, C(CH3)3). 13C{1H} NMR
(100 MHz, 293 K, CDCl ): δ 168.93 (s, C᎐O), 79.00 (d,
᎐
3
2514
J. Chem. Soc., Dalton Trans., 2001, 2508–2517

View Article Online
2J(AX) = 3 Hz, 2J(BX) = 5 Hz), 4.96 and 2.77 (AB spin system,
systems, 2J(AB) = 40 Hz). FAB mass spectrum: m/z 1366
2
2H, ArCH2, J = 13 Hz), 4.88 and 4.58 (AB spin system, 2H,
([M Ϫ BF4]ϩ, 20%). Found: C, 69.59; H, 6.60; N, 0.99. Calc. for
C84H96NO5P2PdBF4 (Mr = 1454.83): C, 69.35; H, 6.65; N,
0.96%.
OCH2C(O)N, 2J = 15 Hz), 4.65 and 3.06 (AB spin system,
2H, ArCH2, 2J = 13 Hz), 4.49 and 3.03 (AB spin system,
2
2H, ArCH2, J = 13 Hz), 4.42 and 3.92 (AB spin system, 2H,
(ꢀ3-2-Methylallyl)-(P,PЈ)-(R)-{5,11,17,23-tetra-tert-butyl-
25,26-bis(diphenylphosphinomethoxy)-27-[(1-phenylethyl)carb-
amoylmethoxy]-28-(trimethylsilyloxy)calix[4]arene}palladium(II)
tetrafluoroborate 12. Yield: 82%; mp 211 ЊC (dec.); IR (KBr,
OCH2C(O)N, 2J = 13 Hz), 3.98 and 2.35 (AB spin system,
2
2H, ArCH2, J = 13 Hz), 1.34 and 1.32 (2d, 2 × 3H, NHCH-
(CH3)Ph, 3J = 7 Hz), 1.05, 1.03 and 0.90 (3s, 9H ϩ 18H ϩ 9H,
C(CH3)3). 13C{1H} NMR (100 MHz, 293 K, CDCl3): δ 170.20
cmϪ1): ν(NH) = 3372br, ν(C᎐O) = 1677s. 31P{1H} NMR (121
and 168.93 (2s, C᎐O), 154.72–130.56 (quaternary aryl C),
᎐
᎐
MHz, 293 K, CD2Cl2): δ 15.2 and 13.5 (2 AB systems,
2J(AB) = 35 Hz). FAB mass spectrum: m/z 1439 ([M Ϫ BF4]ϩ,
100%). Found: C, 66.64; H, 6.78; N, 0.93. Calc. for
C87H105NO5P2SiPdBF4ؒ0.5CH2Cl2 (Mr = 1528.02 ϩ 42.46): C,
66.92; H, 6.80; N, 0.89%.
131.96–124.56 (aryl CH), 74.01 and 73.10 (2s, OCH2C(O)N),
72.05 (d, PCH2O, J(PC) = 80 Hz), 71.50 (d, PCH2O, J(PC) = 78
Hz), 48.47 and 48.04 (2s, NHCH(Me)Ph), 33.75 and 33.63 (2s,
C(CH3)3), 32.52, 31.59 and 30.57 (3s, ArCH2), 31.37, 31.30 and
31.26 (3s, C(CH3)3), 21.50 and 21.36 (2s, NHCH(CH3)Ph) (one
ArCH2 signal is probably overlapping with a tert-butyl signal).
31P{1H} NMR (121 MHz, 293 K, CDCl3): δ 27.6 and 24.8 (2s).
Found: C, 77.07; H, 7.02; N, 2.20. Calc. for C90H100N2O8P2
(Mr = 1399.74): C, 77.23; H, 7.20; N, 2.00%.
(ꢀ3-2-Methylallyl)-(P,PЈ)-(R,R)-{5,11,17,23-tetra-tert-butyl-
25,26-bis(diphenylphosphinomethoxy)-27,28-bis[(1-phenylethyl)-
carbamoylmethoxy]calix[4]arene}palladium(II) tetrafluoroborate
13. Yield: 77%; mp 220 ЊC (dec.); IR (KBr, cmϪ1):
ν(NH) = 3366br, ν(C᎐O) = 1672s. 31P{1H} NMR (121 MHz,
(R,R)-5,11,17,23-Tetra-tert-butyl-25,26-bis(diphenylphos-
phinomethoxy)-27,28-bis[(1-phenylethyl)carbamoylmethoxy]-
calix[4]arene 10. A suspension of 9 (2.280 g, 1.63 mmol) in
phenylsilane (1.5 cm3, 8.15 mmol) was refluxed for 21 days.
After evaporation of the solvent in vacuo, the residue was sub-
jected to flash chromatography using CH2Cl2 as eluent. The
fraction obtained with Rf = 0.13 (SiO2, CH2Cl2) was evaporated
to dryness yielding 10 as a colourless powder. Yield: 1.695 g,
᎐
293 K, CDCl3): δ 12.5 and 10.4 (2AB systems, 2J(AB) = 35 Hz).
FAB mass spectrum: m/z 1527 ([M Ϫ BF4]ϩ, 100%). Found: C,
69.90; H, 6.70; N, 1.75. Calc. for C94H107N2O6P2PdBF4
(Mr = 1616.06): C, 69.86; H, 6.67; N, 1.73%.
General procedure for the syntheses of the Rh(I) complexes 14–16
Typically, a solution of AgBF4 (0.08 mmol) in THF (1 cm3) was
added to a solution of [Rh(NBD)Cl]2 (0.04 mmol) in CH2Cl2
(4 cm3). After 5 min, the solution was decanted to eliminate
AgCl. The supernatant was filtered through Celite and added to
a solution of the ligand (0.08 mmol) in CH2Cl2 (300 cm3). After
1 h the solution was concentrated to ca. 5 cm3 and addition of
pentane afforded an orange precipitate.
76%; mp 171–173 ЊC; IR (KBr, cmϪ1): ν(NH) = 3446br sh,
1
ν(NH) = 3284br, ν(C᎐O) = 1669s. H NMR (400 MHz, 293 K,
᎐
CDCl3): δ 7.24 and 6.91 (2d, 2H, NH, 3J = 8 Hz), 7.44–7.16 (m,
20H, PPh2), 6.76–6.60 (m, 8H, m-ArH), 5.12 (2AMX3 systems,
2H, NHCHMe(Ph), J(AM) = 3J(AX) = 7 Hz), 5.09 and 5.03
3
2
(AB spin system, 2H, PCH2O, J(AB) = 14Hz), 5.03 and 4.81
(ABX system with X = P, 2H, PCH2O, 2J(AB) = 12 Hz,
2J(AX) = 0 Hz, 2J(BX) = 5 Hz), 4.71 and 2.90 (AB spin system,
(Norbornadiene){cis-(P,PЈ)-(R)-[5,11,17,23-tetra-tert-butyl-
25,26-bis(diphenylphosphinomethoxy)-27-[(1-phenylethyl)carb-
2
2H, ArCH2, J = 13 Hz), 4.62 and 4.25 (AB spin system, 2H,
OCH2C(O)N, 2J = 15 Hz), 4.56 and 4.25 (AB spin system,
amoylmethoxy]-28-(hydroxy)calix[4]arene]}rhodium(I)
tetra-
2
fluoroborate 14. Yield: 82%; mp 220 ЊC (dec.); IR (KBr, cmϪ1):
2H, OCH2C(O)N, J = 13 Hz), 4.46 and 3.09 (AB spin system,
2
ν(C᎐O) = 1678s. 1H NMR (500 MHz, 293 K, CD Cl ): δ 8.05 (d,
2H, ArCH2, J = 13 Hz), 4.25 and 3.04 (AB spin system, 4H,
᎐
2
2
ArCH2, 2J = 13 Hz), 1.49 and 1.36 (2d, 2 × 3H, NHCH-
(CH3)Ph, 3J = 7 Hz), 1.13, 1.12, 1.05 and 1.01 (4s, 36H,
C(CH3)3). 13C{1H} NMR (100 MHz, 293 K, CDCl3): δ 169.09
3
1H, NH, J = 8 Hz), 7.79–6.53 (m, 33H, PPh2 ϩ m-ArH), 6.54
and 3.49 (AB spin system, 2H, ArCH2, J(AB) = 14 Hz), 4.96
and 3.48 (AB spin system, 2H, ArCH2, J(AB) = 14 Hz), 4.78
2
2
and 168.96 (2s, C᎐O), 153.74–132.30 (quaternary aryl C),
᎐
(br s, 4H, HC᎐CH of NBD), 4.68 (AMX spin system, 1H,
᎐
3
3
NHCHMe(Ph), J(AM) = 3J(AX) = 7 Hz), 4.58 and 4.43 (AB
133.49–124.79 (aryl CH), 76.60 and 76.16 (2d, PCH2O,
J(PC) = 9 Hz), 74.22 and 73.96 (2s, OCH2C(O)N), 48.78 and
48.42 (2s, NHCH(Me)Ph), 33.92, 33.89, 33.85 and 33.79 (4s,
C(CH3)3), 32.56, 32.43, 32.39 and 31.93 (4s, ArCH2), 31.48 and
31.36 (2s, C(CH3)3), 21.47 and 21.26 (2s, NHCH(CH3)Ph).
31P{1H} NMR (121 MHz, 293 K, CDCl3): δ Ϫ21.4 and Ϫ21.4
(2s) (the signals are resolved). Found: C, 79.14; H, 7.56; N, 2.02.
Calc. for C90H100N2O6P2 (Mr = 1367.71): C, 79.03; H, 7.37; N,
2.05%.
spin system, 2H, OCH2C(O)N, 2J(AB) = 14 Hz), 4.58 and
3.86 (AB spin system, 2H, PCH2O, 2J(AB) = 13 Hz), 4.48
and 3.38 (AB spin system, 2H, ArCH2, 2J(AB) = 14 Hz),
2
4.46 and 3.96 (AB spin system, 2H, PCH2O, J(AB) = 13 Hz),
4.49 and 3.88 (AB spin system, 2H, ArCH2, 2J(AB) = 13
2
Hz), 4.44 and 3.82 (AB spin system, 2H, ArCH2, J(AB) = 14
Hz), 4.07 (br s, 2H, CH of NBD), 1.58 (s, 2H, CH2 of NBD),
1.40, 1.36, 1.13 and 0.97 (4s, 36H, tert-butyl), 0.81 (d, 3H,
NHCH(CH3)Ph, 3J = 7 Hz). 13C{1H} NMR (125 MHz, 293 K,
General procedure for the syntheses of the Pd(II) complexes
11–13
CDCl ): δ 167.83 (s, C᎐O), 156.80–128.21 (quaternary aryl C),
᎐
3
135.02–125.54 (aryl CH), 82.23 and 78.00 (2s, HC᎐CH of
᎐
Typically, a solution of AgBF4 (0.08 mmol) in THF (1 cm3) was
added to a solution of [Pd(η3-C4H7)Cl]2 (0.04 mmol) in CH2Cl2
(4 cm3). After 5 min, the solution was decanted to eliminate
AgCl. The supernatant was filtered through Celite and added
to a solution of the appropriate ligand (0.08 mmol) in CH2Cl2
(300 cm3). After 1 h the solution was concentrated to ca. 5 cm3
and addition of pentane afforded a colourless precipitate.
NBD), 76.04 (s, OCH2C(O)N), 75.91 and 71.81 (2d, PCH2O,
J(PC) = 31 Hz), 69.12 (br s, CH2 of NBD), 53.83 (s, CH of
NBD), 49.17 (s, NHCH(Me)Ph), 36.48 (s, ArCH2), 34.93,
34.81, 34.62 and 34.58 (4s, C(CH3)3), 32.77, 32.68 and 31.98 (3s,
ArCH2), 32.36, 32.22 and 31.63 (3s, C(CH3)3), 21.72 (s,
NHCH(CH3)Ph). 31P{1H} NMR (121 MHz, 293 K, CDCl3):
δ 33.6 and 12.9 (2 ABX systems with X = Rh, 2J(AB) = 30 Hz,
J(P–Rh) = 157 Hz). FAB mass spectrum: m/z 1400
([M Ϫ BF4]ϩ, 100%). Found: C, 70.50; H, 6.38; N, 1.23. Calc.
for C87H97NO5P2RhBF4 (Mr = 1488.40): C, 70.21; H, 6.57; N,
0.94%.
(ꢀ3-2-Methylallyl)-(P,PЈ)-(R)-{5,11,17,23-tetra-tert-butyl-
25,26-bis(diphenylphosphinomethoxy)-27-[(1-phenylethyl)carb-
amoylmethoxy]-28-(hydroxy)calix[4]arene}palladium(II) tetra-
fluoroborate 11. Yield: 80%; mp 185 ЊC (dec.); IR (KBr, cmϪ1):
ν(OH) = 3500br, ν(NH) = 3417br, ν(C᎐O) = 1685s. 31P{1H}
(Norbornadiene){cis-(P,PЈ)-(R)-[5,11,17,23-tetra-tert-butyl-
25,26-bis(diphenylphosphinomethoxy)-27-[(1-phenylethyl)carb-
᎐
NMR (121 MHz, 293 K, CDCl3): δ 17.9 and 13.4 (2 AB
J. Chem. Soc., Dalton Trans., 2001, 2508–2517
2515

View Article Online
amoylmethoxy]-28-(trimethylsilyloxy)calix[4]arene]}rhodium(I)
tetrafluoroborate 15. Yield: 86%; mp 163 ЊC (dec.); IR (KBr,
(1 cm3), BSA (0.58 cm3, 2.38 mmol), dimethyl malonate (0.27
cm3, 2.38 mmol) and KOAc (0.006 g, 0.06 mmol). The mixture
1
cmϪ1): ν(NH) = 3392br, ν(C᎐O) = 1677s. H NMR (400 MHz,
was then stirred at 0 ЊC.
᎐
1
3
293 K, CDCl3): δ 7.96 (d, H, NH, J = 7 Hz), 7.75–6.09 (m,
33H, PPh2 ϩ m-ArH), 5.62 and 5.33 (AB spin system, 2H,
PCH2O, 2J (AB) = 13 Hz), 5.60 and 5.28 (AB spin system, 2H,
PCH2O, 2J (AB) = 13 Hz), 4.97 (AMX3 spin system, 1H,
Method b. Sodium malonate (2.5 mmol) was prepared from
NaH (0.100 g, 60% dispersion in mineral oil, 2.5 mmol) and
dimethyl malonate (0.29 cm
3, 2.5 mmol) in THF (5 cm3). To this
NHCHMe(Ph), J(AM) = 3J(AX) = 7 Hz), 4.66 and 4.01 (AB
suspension was then added a solution of 1,3-diphenylprop-2-
enyl acetate (0.300 g, 1.2 mmol) in THF (1 cm
3
spin system, 2H, OCH2C(O)N, 2J (AB) = 14 Hz), 4.49 and 3.42
3) and a solution
2
(AB spin system, 2H, ArCH2, J (AB) = 14 Hz), 4.45 and 3.12
of the catalyst (0.012 mmol) in THF (3 cm3). The mixture was
refluxed until the reaction was completed. The reaction was
(AB spin system, 2H, ArCH2, 2J (AB) = 13 Hz), 4.36 (br s, 4H,
HC᎐CH of NBD), 3.85 (br s, 2H, CH of NBD), 4.27 and 3.12
, R = 0.5 for starting compound,
monitored by TLC (SiO2
᎐
f
2
(AB spin system, 2H, ArCH2, J(AB) = 13 Hz), 3.96 and 3.00
Rf = 0.2 for alkylated product, AcOEt–hexane, 5 : 1, v/v). After
completion a few drops of acetic acid were added to quench
the reaction. The oily residue, obtained after work-up, was
subjected to flash chromatography using AcOEt–hexane (5 : 1,
v/v) as eluent. After evaporation of the fraction with Rf
the purity of the methyl-2-carbomethoxy-3,5-diphenylpent-4-
enoate sample was checked by H NMR. The enantiomeric
excess was determined by H NMR with an optically active
shift reagent, (ϩ)-Eu(hfc)3. A dilute CDCl3 solution of the
organic substrate was prepared in a NMR tube and small
quantities of the shift reagent were progressively added until a
clean splitting of the peaks was achieved.
(AB spin system, 2H, ArCH2, 2J(AB) = 13 Hz), 1.43 (s, 2H, CH2
3
of NBD), 1.28 (d, 3H, NHCH(CH3)Ph, J = 7 Hz), 1.39, 1.36,
0.98 and 0.66 (4s, 36H, tert-butyl), 0.14 (s, 9H, SiMe3). 13C{1H}
NMR (100 MHz, 293 K, CDCl ): δ 167.69 (s, C᎐O), 153.64–
= 0.2,
᎐
3
125.11 (quaternary aryl C), 134.31–124.32 (aryl CH), 81.80 and
1
77.66 (2s, HC᎐CH of NBD), 73.56 (s, OCH C(O)N), 73.12 (m,
᎐
2
1
PCH2O), 68.50 (br s, CH2 of NBD), 51.98 (s, CH of NBD),
48.58 (s, NHCH(Me)Ph), 35.77 (s, ArCH2), 34.27, 34.17, 33.90
and 33.34 (4s, C(CH3)3), 32.40 (s, ArCH2), 31.70 and 31.07 (2s,
C(CH3)3), 21.56 (s, NHCH(CH3)Ph), 0.42 (s, SiMe3) (two
ArCH2 signals are probably overlapping with a tert-butyl sig-
nal). 31P{1H} NMR (121 MHz, 293 K, CDCl3): δ 21.3 and 13.4
2
(2 ABX systems with X = Rh, J(AB) = 28 Hz, J(P–Rh) = 148
Hydrogenation experiments
Hz). FAB mass spectrum: m/z 1473 ([M Ϫ BF4]ϩ, 100%).
Found: C, 69.20; H, 7.13; N, 0.84. Calc. for C90H106NO5P2-
SiRhBF4 (Mr = 1561.55): C, 69.22; H, 6.84; N, 0.90%.
The catalytic runs were performed in a 100 cm3 glass-lined steel
autoclave containing a magnetic stirring bar. In a typical
experiment, the autoclave was charged with a MeOH solution
of the catalyst precursor (15 cm3, 0.02 mmol) under nitrogen.
The autoclave was flushed twice with H2 and then pressurised to
20 bar at 40 ЊC for 1 h to preform the active catalyst. After
cooling and depressurisation, dimethyl itaconate (200 equiv.)
was introduced. The autoclave was then pressurised again with
H2 at 20 bar and 40 ЊC. At pre-set times, samples were taken
to follow the progress of the reaction and analysed by Gas
Chromatography (WCOT fused silica; stationary phase CP-Sil
(Norbornadiene){cis-(P,PЈ)-(R,R)-[5,11,17,23-tetra-tert-
butyl-25,26-bis(diphenylphosphinomethoxy)-27,28-bis[(1-phenyl-
ethyl)carbamoylmethoxy]calix[4]arene]}rhodium(I) tetrafluoro-
borate 16. Yield: 86%; mp 191 ЊC (dec.); IR (KBr, cmϪ1):
1
ν(NH) = 3364br, ν(C᎐O) = 1670s. H NMR (400 MHz, 293 K,
᎐
CDCl3): δ 7.79 and 7.75 (2d, 2H, NH, 3J = 8 Hz), 7.54–7.01 (m,
20H, PPh2), 6.93–6.69 (m, 8H, m-ArH), 5.70 and 5.41 (ABX
spin system with X = P, 2H, PCH2O, 2J(AB) = 12 Hz,
2J(AX) = 2 Hz, 2J(BX) = 5 Hz), 5.67 and 5.32 (ABX spin system
with X = P, 2H, PCH2O, 2J(AB) = 12 Hz, 2J(AX) = 3 Hz,
2J(BX) = 5 Hz), 4.97 (2AMX3 spin systems, 2H, NHCH-
Me(Ph), 3J(AM) = 3J(AX) = 7 Hz), 4.93 and 4.65 (AB spin sys-
1
5 CB). The enantiomeric excess was determined by H NMR
with an optically active shift reagent, (ϩ)-Eu(hfc)3. A dilute
CDCl3 solution of the organic substrate was prepared in a
NMR tube and small quantities of the shift reagent were
progressively added until a clean splitting of the peaks was
achieved.
2
tem, 2H, OCH2C(O)N, J(AB) = 15 Hz), 4.93 and 3.03 (AB
2
spin system, 2H, ArCH2, J(AB) = 13 Hz), 4.85 and 3.38 (AB
spin system, 2H, ArCH2, 2J(AB) = 13 Hz), 4.84 and 3.29
2
Acknowledgements
(AB spin system, 2H, ArCH2, J(AB) = 13 Hz), 4.83 and 4.79
(AB spin system, 2H, OCH2C(O)N, 2J(AB) = 13 Hz), 4.57 and
3.09 (AB spin system, 2H, ArCH2, 2J(AB) = 13 Hz), 4.35 (br s,
We thank Prof. J. Harrowfield (University of Perth, WA) for
his interest in this work. We are grateful to Genzyme Pharma-
ceuticals (Switzerland) for a gift of rhodium trichloride.
4H, HC᎐CH of NBD), 3.82 (br s, 2H, CH of NBD), 1.44 and
᎐
1.36 (2d, 2 × 3H, NHCH(CH3)Ph, 3J = 7 Hz), 1.38 (s, 2H, CH2
of NBD), 1.17, 1.11, 1.09 and 1.04 (4s, 36H, tert-butyl).
13C{1H} NMR (100 MHz, 293 K, CDCl3): δ 168.59 and 168.52
References
(2s, C᎐O), 153.24–125.70 (quaternary aryl C), 133.04–124.65
᎐
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(aryl CH), 79.49 and 79.10 (2s, HC᎐CH of NBD), 74.02 (m,
᎐
PCH2O), 73.85 and 73.48 (2s, OCH2C(O)N), 67.58 (br s, CH2
of NBD), 52.19 (s, CH of NBD), 48.93 and 48.84 (2s,
NHCH(Me)Ph), 34.02, 33.96 and 33.90 (3s, C(CH3)3), 33.78,
32.00, 31.91 and 31.81 (4s, ArCH2), 31.44 and 31.35 (2s,
C(CH3)3), 22.21 and 21.93 (2s, NHCH(CH3)Ph). 31P{1H}
NMR (121 MHz, 293 K, CDCl3): δ 17.5 and 16.4 (2ABX
systems with X = Rh, 2J(AB) = 35 Hz, J(P–Rh) = 150 Hz).
FAB mass spectrum: m/z 1525 ([M Ϫ BF4]ϩ, 45%). Found: C,
69.98; H, 6.75; N, 1.68. Calc. for C94H107N2O6P2RhBF4
(Mr = 1612.52): C, 70.10; H, 6.69; N, 1.74%.
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Chem. Soc., 1999, 121, 14.
10 P. D. Beer, D. Hesek, K. C. Nam and M. G. B. Drew,
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Method a (see Table 1). To a solution of the catalyst (0.012
mmol) in CH2Cl2 (8 cm3) were successively added a solution of
1,3-diphenylprop-2-enyl acetate (300 mg, 1.2 mmol) in CH2Cl2
2516
J. Chem. Soc., Dalton Trans., 2001, 2508–2517

View Article Online
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12 M. Munakata, L. P. Wu, T. Kuroda-Sowa, M. Maekawa,
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