Effect of chelating vs. bridging coordination of chiral short-bite P-X-P (X = C, N, O) ligands in enantioselective palladium-catalysed allylic substitution reactions

Article abstract of DOI:10.1039/b309385a

The chiral short-bite ligands (R_a,R_a)-bis (dinaphthylphosphonito)methane, (R_a,R_a)-1, (R_a,R_a)-bis-dinaphthylpyrophosphite, (R_a,R_a)-2, (S_c)-bis(diphenylphosphino) -sec-butylamine, (S_c)-3, (R_a,R_a)- bis(dinaphthylphosphonito)-phenylamine, (R_a,R_a)-4a, (R_a,R_a, S_c)-bis(dinaphthylphosphonito)-sec-butylamine, (R_a,R_a,S_c)-4b, and (R_a, S_c)-(dinaphthylphosphonito) (diphenylphosphino)-sec-butylamine, (R_a,S_c)-5, have been synthesised. The cationic palladium-allyl mononuclear chelate, [Pd(η³-PhCHCHCHPh) (μ-L-L_short-bite)]PF₆ [L-L_short-bite = (S_c)-3, (R_a,R_a)-4a, (R_a,R_a,S_c)-4b and (R_a, S_c)-5 for complexes 8, 9, 10 and 11, respectively] and binuclear bridged [Pd(η³-PhCHCHCHPh)-(μ-R_a,R_a, R_a-2)]₂(PF₆)₂, 12, have been isolated. The short-bite chiral ligands synthesised have been tested in the palladium-allyl catalysed substitution reaction of 1,3-diphenylallyl acetate with dimethyl malonate. The catalytic system was studied, in solution, by a multinuclear NMR technique. In the catalytically active species formed with (R_a,R_a)-2 ligand, [Pd(η³- PhCHCHCHPh)(R_a,R_a-2)]₂ (PF₆)₂, 12, the palladium(II) centres are bridged by two ligands which are forced to adopt a nearly cis-coordination to allow coordination of the allyl-moiety. Semiempirical calculations on a biphenyl-model molecule, similar to the species 12, indicate that this situation induces a strain and rigid conformation in the chiral ligands, which produce differences in the terminal allyl carbon atoms. As consequence, the catalytic product was obtained with an enantiomeric excess of 57.1% in the S form. A low e.e. value was obtained when the (R_a,R_a)-1, (S_c)-3, (R_a,R_a)-4a, (R_a,R_a,S_c)-4b and (R_a, S_c)-5 ligands have been tested in the same palladium-catalysed reaction.

Full text of DOI:10.1039/b309385a

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Effect of chelating vs. bridging coordination of chiral short-bite
P–X–P (X ؍ C, N, O) ligands in enantioselective
palladium-catalysed allylic substitution reactions†
GianPiero Calabrò, Dario Drommi, Giuseppe Bruno and Felice Faraone*
Dipartimento di Chimica Inorganica, Chimica Analitica, Chimica Fisica dell’Università di
Messina Salita Sperone 31, Villaggio S. Agata, I-98166 Messina, Italy
Received 5th August 2003, Accepted 23rd October 2003
First published as an Advance Article on the web 14th November 2003
The chiral short-bite ligands (Ra,Ra)-bis(dinaphthylphosphonito)methane, (Ra,Ra)-1, (Ra,Ra)-bis-dinaphthyl-
pyrophosphite, (Ra,Ra)-2, (Sc)-bis(diphenylphosphino)-sec-butylamine, (Sc)-3, (Ra,Ra)-bis(dinaphthylphosphonito)-
phenylamine, (Ra,Ra)-4a, (Ra,Ra,Sc)-bis(dinaphthylphosphonito)-sec-butylamine, (Ra,Ra,Sc)-4b, and (Ra,Sc)-
(dinaphthylphosphonito)(diphenylphosphino)-sec-butylamine, (Ra,Sc)-5, have been synthesised. The cationic
palladium–allyl mononuclear chelate, [Pd(η3-PhCHCHCHPh)(µ-L–Lshort-bite)]PF6 [L–Lshort-bite = (Sc)-3, (Ra,Ra)-4a,
(Ra,Ra,Sc)-4b and (Ra,Sc)-5 for complexes 8, 9, 10 and 11, respectively] and binuclear bridged [Pd(η3-PhCHCHCHPh)-
(µ-Ra,Ra-2)]2(PF6)2, 12, have been isolated. The short-bite chiral ligands synthesised have been tested in the
palladium–allyl catalysed substitution reaction of 1,3-diphenylallyl acetate with dimethyl malonate. The catalytic
system was studied, in solution, by a multinuclear NMR technique. In the catalytically active species formed with
(Ra,Ra)-2 ligand, [Pd(η3-PhCHCHCHPh)(Ra,Ra-2)]2(PF6)2, 12, the palladium() centres are bridged by two ligands
which are forced to adopt a nearly cis-coordination to allow coordination of the allyl-moiety. Semiempirical
calculations on a biphenyl-model molecule, similar to the species 12, indicate that this situation induces a strain
and rigid conformation in the chiral ligands, which produce differences in the terminal allyl carbon atoms.
As consequence, the catalytic product was obtained with an enantiomeric excess of 57.1% in the S form.
A low e.e. value was obtained when the (Ra,Ra)-1, (Sc)-3, (Ra,Ra)-4a, (Ra,Ra,Sc)-4b and (Ra,Sc)-5 ligands have
been tested in the same palladium-catalysed reaction.
Introduction
Short-bite ligands have been widely used in organometallic
chemistry owing to their structural features.1 In fact, they are
bidentate ligands in which the donor-atoms are separated by
one spacer atom, as C, N, O, S, and are able to give, by co-
ordination to a metal centre, either chelated mononuclear or
bridged binuclear complexes.1 In the mononuclear complexes,
the short-bite ligand forms a strained four-membered ring with
a very small bite angle; in the binuclear complexes, two metal
centres are held in close proximity by the features of the bridg-
ing short-bite ligand. For the latter coordination mode, novel
modes of substrate activation, as a consequence of cooperative
interactions between the metal centres, can be achieved.2 Owing
Chart 1
to these properties, both mononuclear and binuclear com-
new ligands, with structural features analogous to dppm,
dppma, and Ph2PPy, containing the chiral moiety –P(binaph-
thyl) instead of –PPh2. In a subsequent step of the work, we
explored the coordinating properties of the synthesised ligands
toward palladium()–allyl substrates. This study was prelimin-
ary to the use of such systems, containing palladium()–allyl-
substrates and the chiral P–X–P (X = C, N, O) short-bite
ligands, in conventional palladium-catalysed asymmetric allylic
alkylation reactions. The work was focused to have insight on
the effect of chelating or bridging coordination mode of P–X–P
short-bite ligand in the palladium-catalysed allylic substitution
reactions.
plexes, containing short-bite ligands, have been found to act as
homogeneous catalysts.3
Among the short-bite ligands, the bis(diphenylphosphino)-
methane (dppm) and analogous 1,1-diphosphines,1a,c,4 the
bis(diphenylphosphino)methylamine (dppma)1e,f,5 and the
2-(diphenylphosphino)pyridine (Ph2PPy)1b,d,6 have been widely
studied and have shown great versatility either to bridge metal
centres or to display chelating behaviour.
As far as we know, the only chiral optically pure short-bite
ligands reported in literature are A–C.7
Among them only the diphosphines MiniPHOS A were
explored as catalyst precursors in asymmetric catalysis, afford-
ing excellent enantioselectivity in representative reactions.7
Either the conformational rigidity of the highly strained
four-membered ring formed by chelation, or the cooperative
interaction between metal centres in the binuclear complexes
can promote beneficial effects in the asymmetric C–C form-
ation catalysis.3d On this basis, we started with the synthesis of
Results and discussion
Synthesis of the ligands
The new short-bite chiral ligands synthesised are reported in
Fig. 1.
The synthesised ligands, in principle, should behave either as
chelating, and originate four-membered metallacycles, or as
bridging ligands to give bimetallic species. The different value
† Electronic supplementary information (ESI) available: Colour
versions of Fig. 2 and Fig. 4. See http://www.rsc.org/suppdata/dt/b3/
b309385a/
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 8 1 – 8 9
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Fig. 1 Synthesised ligands.
of the angle P–X–P (X = C, N, O) should be the factor
determining their coordination mode.
of the phosphorochloridite in tetrahydrofuran containing a
stoichiometric amount of H2O, in the presence of NEt3; this
was converted to corresponding sodium salt by reaction with
sodium hydride, in tetrahydrofuran. Then, the addition of
the phosphorochloridite, (Ra)-6, in the 1 : 1 molar ratio, to this
solution containing the sodium phosphonato, afforded the
pyrophosphite ligand (Ra,Ra)-2, in high yields.
The ligand (Ra,Ra)-1 was easily obtained from the reaction
of bis(dichlorophosphino)methane with (Ra)-binaphthol, in a
molar ratio 1 : 2, in toluene, at room temperature, in the pres-
ence of an excess of NEt3. It is a microcrystalline white solid,
moderately stable in the air and in solution; its 31P{1H} NMR
spectrum, in CDCl3, shows a singlet at δ 204.0.
We attempted the synthesis of a compound similar to 2-(di-
phenylphosphino)pyridine, Ph2PPy, containing axial chirality
at phosphorus substituents, following the method reported to
obtain this short-bite ligand.8 All the attempts to obtain it by
reaction of 2-bromopyridine with n-BuLi, in THF at 173 K,
and subsequently with the phosphorochloridite derived from
(Ra)-binaphthol, (Ra)-6, failed and afforded to a mixture with-
out the desired product. The major product shows in the
31P{1H} NMR spectrum, in CDCl3, a signal (145.4 ppm) at
frequency significantly shifted to higher field compared to the
phosphonito group; it was separated by column chromato-
graphy and characterized by elemental analysis, mass spectrum
and IR and NMR spectroscopy, as the bis(binaphthyl)pyro-
phosphite ligand, (Ra,Ra)-2.
The formation of (Ra,Ra)-2 should occur by partial form-
ation of the corresponding phosphonate from the reaction of
(Ra)-6 with little amount of H2O; this is in tautomeric equi-
librium with the phosphite species.9 The reaction of the phos-
phite with the unreacted phosphorochloridite, (Ra)-6, in the
presence of pyridine, afforded the final product (Ra,Ra)-2 in low
yields. A similar reaction path was recently proposed by Pastor
et al.10 for the synthesis of a sterically congested pyrophosphite,
starting from the phosphorochloridite derived from 3,3Ј,
5,5Ј-tetra-tert-butyl-1,1Ј-biphenyl-2,2Ј-diol. The synthesis of
diphosphoxanes by reaction of phosphorochloridite with the
corresponding phosphonate, in the presence of an hydrogen
chloride acceptor, is usually employed.11,12
Scheme 1
The N,N-bis(diphosphino)alkylamine, (Sc)-3, N,N-bis(di-
phosphonito)alkyl-amine, (Ra,Ra)-4a and (Ra,Ra,Sc)-4b and
mixed N-(phosphino)-N-(phosphonito)-alkylamine, (Ra,Ra,Sc)-
5, have been designed to determine the effects associated with
the nature, the absolute configuration and the number of the
stereogenic centres in the coordinated ligands.
We obtained the (Ra,Ra)-2 ligand in high yields revising the
synthesis method. The phosphonate was prepared by hydrolysis
D a l t o n T r a n s . , 2 0 0 4 , 8 1 – 8 9
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Scheme 2
Ligands similar to (Sc)-3, in which R = CHMePh and
the product was better obtained by reacting the (Sc)-(ϩ)-sec-
CHCH3COOEt, were previously reported but they were not
butylamine first with (Ra)-6, in the molar ratio 1 : 1, in toluene,
at room temperature, in the presence of an excess of NEt3; next,
in situ, was added the chlorodiphenylphosphine, in the molar
ratio 1 : 1, to effect complete hydrogen replacement of (Sc)-(ϩ)-
sec-butylamine. The reaction was followed by 31P{1H} NMR
spectra. At the end, the reaction mixture contains (Ra,Sc)-5,
together with little amount of (Ra,Ra,Sc)-4b and of corre-
sponding phosphino-oxide ligands. The pure (Ra,Sc)-5 was
obtained by flash chromatography on SiO2 column.
used in asymmetric catalysis.7
Literature reports indicate that the presence of an alkyl
group on the nitrogen atom of the N,N-bis(diphosphino)alkyl-
amines results in favoured formation of a four-membered
strained ring when the ligand coordinates to
a metal
center.5d We confirmed that the N,N-bis(diphosphino)alkyl-
amines coordinate as chelating ligand by an X-ray diffraction
structural determination on [M(Sc-3)Cl2] (M
= Pd, Pt)
complexes.13
Synthesis of catalytic species [Pd(ꢀ3-PhCHCHCHPh)-
(L–Lshort-bite)]PF6 and [Pd(ꢀ3-PhCHCHCHPh)(ꢁ-L–Lshort-bite)]2-
(PF6)2
The diphosphinoamines and diphosphonitoamines chiral
ligands have been synthesised by the reaction of the correspond-
ing primary amine RNH2 (R = Ph, (Sc)-(ϩ)-sec-CHC2H5CH3)
with the diphenylchlorophosphine or (Ra)-6, in the molar ratio
1 : 2, in toluene at 0 ЊC, in the presence of an excess of NEt3.
Differently from the other P–N–P ligands here reported, (Sc)-3
shows in the 31P{1H} NMR spectrum, in CDCl3, at 298 K, a
broad signal at δ 49.6; this signal, at 220 K, raises two doublets
Preliminarily, to test the catalytic system containing the
palladium()–allyl species and the chiral P–X–P (X = C, N, O)
short-bite ligands in the substitution reaction of 1,3-di-
phenylallyl acetate with dimethylmalonate, we synthesised
the catalytic allyl species of the type [Pd(η3-PhCHCH-
2
centred at δ 52.9 and 42.9, with JPP of 24.0 Hz. At 330 K the
[Pd(η3-PhCHCHCHPh)-
1
31P{1H} NMR spectrum exhibits a singlet at δ 51.5. In the H
CHPh)(L–Lshort-bite)]PF6
and/or
(µ-L–Lshort-bite)]2(PF6)2 with the aim to obtain information about
their conformations in solution.
NMR spectrum, the resonance of the methyl group bonded to
stereogenic carbon atom appears as a doublet; while the phenyl-
ic protons show a dynamic behaviour, the methyl group
resonance is not affected by temperature variation. A similar
behaviour in the 31P{1H} NMR variable-temperature spectrum
was observed for other diphosphinoamines and was explained
considering that these species, in solution, different conform-
ations can adopt.14
The compounds have been characterized by elemental analy-
sis, conductivity values and spectroscopic multinuclear NMR
studies; these will be discussed below. A conductivity value of
183 µS in acetone solution, using a 5×10Ϫ4–10Ϫ4 molar concen-
tration range, indicates a dimeric structure for 12 and further
supports the results reached on the basis of NMR data (see
below). Unfortunately, we are not able to obtained crystals of
compound 12 suitable for X-ray analysis. Compound 7,
obtained by reacting [Pd(η3-PhCHCHCHPh)(µ-Cl)]2 with the
stoichiometric amount of (Ra,Ra)-1 following the procedure
described above, formed as a mixture of mononuclear and
binuclear cationic species, which we are not able to separate;
their characterization was supported by multinuclear NMR
studies.
The presence of conformers can be related to the restricted
rotation about the P–N bonds of the diphosphinoamine and to
2
the magnitude of their torsional barriers. The JPP of 24.0 Hz
found for (Sc)-3 supports14 the presence of conformers with Cs
symmetry; no evidence of the presence of the C2vЈ conformer
was obtained.
NMR studies
The catalytically active species 7–12 have been generated, in
CDCl3 solution, in situ, into the NMR tube, as previously
described. When the equilibrium is reached, all the conform-
Chart 2
1
ational isomers present in solution have been detected by H,
The (Ra,Ra)-4a and (Ra,Ra,Sc)-4b ligands have been obtained
as white solids, from the reaction of phenylamine and (Sc)-(ϩ)-
sec-butylamine, respectively, with (Ra)-6, in the molar ratio 1 : 2,
in toluene, at 0 ЊC, using an excess of NEt3. Their 31P{1H}
NMR spectra, in CDCl3, at 298 K show a sharp singlet at
δ 136.9 and 138.0 relative to the ligand (Ra,Ra)-4a and (Ra,
Ra,Sc)-4b, respectively. The bulkiness of the substituents on the
phosphorus atoms does not allow in this case the rotation
around the P–N bonds, precluding the more sterically stable Cs
conformer formation.
13C and 31P NMR spectroscopy.
The enantioselectivity of the allylic substitution reaction
process is determined by the regioselectivity of the nucleophilic
attack; the latter depends from the ability of the coordinated
chiral ligand to induce different nucleophilic character to the
two terminus carbons on the allyl-group.16
By a multinuclear NMR study in solution, it was very useful
to know: (i) the chelating or bridging coordination mode
assumed by the short-bite ligand; (ii) the allylic conformational
isomers present in the catalytic conditions and the existence of
exchange processes;17 (iii) possible steric or electronic effect
which will determine the site of the nucleophilic attack.17 It is
clear that chelating or bridging coordination of the bidentate
The synthesis of the mixed phosphino-phosphonito ligand
(Ra,Sc)-5 was practicable owing to different rate of hydrogen
substitution from the primary amine (Sc)-(ϩ)-sec-butylamine;15
D a l t o n T r a n s . , 2 0 0 4 , 8 1 – 8 9
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Table 1 Relevant 1H, 31P{1H} and 13C{1H} NMR spectroscopic data of palladium()–phenylallyl compounds 7–12a, b
δ(1H)
δ(31P)
δ(13C)
c
Compound
Ha
Hb
Pa
Pb
2JPaPb
Ca
Cb
82.2
99.8
88.1
90.2
89.7
114.3
120.5
93.7
Conformation
7a
7b
8
9
10
11
4.74
6.19
5.66
5.71
5.75
5.87
5.89
4.79
5.47
6.52
5.65
5.68
5.71
6.43
6.28
5.52
173.0
177.8
62.3
64.5
63.0
110.8
110.2
139.1
79.5
101.8
87.8
89.1
88.5
88.6
92.6
98.6
exo syn–syn
exo syn–synd
171.6
75
exo or endo anti–anti
exo or endo anti–anti
exo or endo anti–anti
endo syn–synd
58.9
58.6
127.4
116
121
177
exo syn–antid
12
exo syn–synd
c 2
a In CDCl3 at room temperature. b δH, δP, δC are in ppm.
J
are in Hz. d Binuclear species.
PaPb
Chart 3
“short-bite” ligands modify differently the electronic and steric
features of terminal allylic carbon atoms. Besides, chelating
coordination gives the [Pd(η3-PhCHCHCHPh)(L–Lshort-bite)]ϩ
species while bridging coordination affords the binuclear
[Pd(η3-PhCHCHCHPh)(Ra,Sc-5)]CF3SO3, 11, since the corre-
sponding complex [Pd(η3-PhCHCHCHPh)(Ra,Sc-5)]PF6 has
resulted to be less stable in solution during the necessary
experimental time. The 31P{1H}NMR spectrum has evidenced
the presence of at least two isomers in solution (Table 1).
Through 2D NOESY experiments it has been possible to assign
the configuration of both isomers as endo syn–syn (85%) and
exo syn–anti (12%),
The two species are not exchanging in solution at 298 K tem-
perature. The syn–syn configuration for the major isomer it was
assigned through the NOE peaks between the two allylic pro-
tons Ha (5.87 ppm) and Hb (6.43 ppm). The syn–anti configur-
ation for the other isomer it has been demonstrated by the
presence of a NOE peak between the terminal hydrogen Hb*
(6.28 ppm) and the central hydrogen Hc* (6.34 ppm), and by the
absence of any NOE peak between the hydrogen Ha* (5.89
ppm) and the other two allylic hydrogens. As expected, the ter-
minal carbon atoms Cb and Cb* are shifted to lower positions
than the Ca and Ca* atoms because they are trans to the phos-
phonite group. The isomer syn–syn is characterized by an
higher chemical shift difference between the two terminal allylic
carbons than the isomer present in less concentration.19 The
different electronic characteristics of the two phosphorous
atoms led to different chemical shifts for the two terminal allyl
carbons and make such atoms different to nucleophilic attack.
A different situation has been found with the species 12, con-
taining the ligand (Ra,Ra)-2, in which the spacer heteroatom
between the two phosphorous atoms is the oxygen.
2ϩ
[Pd(η3-PhCHCHCHPh)(µ-L–Lshort-bite)]2 one, in which each
palladium atom is coordinated to the allyl group and to two
phosphorus atoms of different bridging chiral ligand; the latter
arrangement seems the same as that due to the coordination of
two monodentate phosphonite chiral ligands to the palladium–
allyl centre.
1
In Table 1 are reported the spectroscopic H, 31P{1H} and
13C{1H} NMR data, together with the isomer configuration
assignments, for the catalytic palladium–allyl species.
We started with the species [Pd(η3-PhCHCHCHPh)(Sc-3)]ϩ,
8, to acquire confidence in the study of catalytic system. The
full assignment of the proton signals has been possible by the
1H 2D-NOESY spectrum.
The complex assumes a symmetric conformation,18 since
both the terminal allylic protons Ha and Hb lie in the same
range of chemical shift. Both protons show cross peaks with
the central allylic hydrogen Hc and with the ortho hydrogen in
the close phenyls bound to the same carbon atom.
The complete symmetry of the molecule is also evidenced by
the 13C NMR spectra in which it is observed that the chemical
shift of both allylic terminal carbons Ca and Cb lie very close
each other at δ 87.8 and 88.1, respectively.
It can be concluded that the catalytically active species 8 is
present in solution as the only highly symmetric conformer. We
are not able to distinguish between endo anti–anti or exo anti–
anti being the chemical shift of Ha and Hb protons coincident.
An analogous situation has been found with the species 9 and
10, containing the ligands (Ra,Ra)-4a and (Ra,Ra,Sc)-4b; in fact,
in solution only one symmetric18 conformer in high concen-
tration was evidenced.
The 31P{1H} NMR spectrum of this catalytically active
species, in CDCl3 solution, presents two couples of doublets at
δ 139.11 (d, 2JPbPa=177 Hz) and at δ 127.44 (d, 2JPbЈPaЈ=177 Hz),
respectively. The 2D-NOESY NMR spectrum let us to assign
the resonances of the allylic hydrogens and to establish the
exact configuration of the species present in solution. NMR
and experimental data allow one to assign it as a dimeric
The multinuclear NMR analysis of the product obtained
with the (Ra,Sc)-5 ligand has been possible only for the species
2ϩ
structure [Pd(η3-PhCHCHCHPh)(Ra,Ra-2)]2 in which the
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Scheme 3
palladium() centres are bridged by the two short-bite ligands
(Ra,Ra)-2. The molecule presents two allylic fragments in the
same configuration exo syn–syn; the absence of exchange peaks
allows one to exclude the presence, in CDCl3 solution, of
two mononuclear palladium() allylic complexes in different
conformation and strongly supports the presence of only one
1
binuclear species. This assignment is further confirmed by H
NMR T1 measurement; in fact, for this compound a 600 ms
value has been measured in agreement with the expected relax-
ation time for the mass increment in the binuclear species (for
the chelated mononuclear species 8–11, T1 values in the range
850–750 ms have been observed). As shown in Fig. 2, cross-
peaks between Hb and Ha have been observed, giving rise to the
assignment of the configuration of the allylic fragments.
Fig. 3 31P{1H} NMR spectrum in CDCl3 at 298 K for the mixture of
isomers in which 7a (∆) and 7b (᭺) are the major isomers.
by exchange cross peak in the 2D 1H NOESY between the two
mononuclear species (∆ vs. ꢀ) each other and between the
binuclear species (᭺ vs. ᮀ and ×) each other.
Palladium-catalysed asymmetric allylic alkylation reactions
We tested the versatility of the short-bite chiral ligands (Ra,Ra)-
1, (Ra,Ra)-2, (Sc)-3, (Ra,Ra)-4a, (Ra,Ra,Sc)-4b, (Ra,Sc)-5, in
the palladium–allyl catalysed substitution reaction of 1,3-di-
phenylallyl acetate with dimethylmalonate.
As will be shown in the following, the 2-(1,3-diphenylallyl)-
dimethylmalonate was obtained with an enantiomeric excess
that is almost meaningful if compared to those of analogous
catalytic systems. It was of interest to analyse the results con-
sidering the conformational isomers of the catalytically active
species present in solution, especially in the case of binuclear
compound, 12, which is quite a novelty in the literature.
The species 8, 9 and 10, formed with the (Sc)-3, (Ra,Ra)-4a
and (Ra,Ra,Sc)-4b ligands, are each present in solution as a
single highly symmetric conformer; this situation does not
allow one to discriminate between the two terminal allylic
carbon Ca and Cb in the nucleophilic attack by dimethyl malon-
ate; thus, it occurs without induction of any significative
enantiomeric excess19 and the catalytic product 2-(1,3-diphenyl-
allyl)dimethylmalonate was obtained as a racemic mixture.
As previously shown, in the species 7 the ligand (Ra,Ra)-1
assumes either the chelated or the bridged coordination and in
CDCl3 solution are present the mononuclear cationic species
and the binuclear cationic one, together with at least other three
isomers in very low concentration. Also using (Ra,Ra)-1 as
ligand, a low e.e. (about 8%) was obtained.
Recently, Moberg et al. introduced the concepts of steric
symmetry and electronic dissymmetry of chiral bidentate
ligands in the palladium catalysed allylic substitution;20 using
the C2-symmetric P,P-ligand, which is different from (Ra,Ra)-1
in its –CH2–CH2– spacer, the product of alkylation of 1,3-di-
phenyl-2-propenyl acetate with malonate was isolated with an
enantiomeric excess of 73% (S) (deprotected ligand) and 94%
(S) (protected ligand). The very different enantioselectivities
found using (Ra,Ra)-1 and the analogous ligand with a –CH2–
CH2– spacer, very likely are the result of the four- or five-
member metallacycle conformations assumed by chelation to
the palladium–allyl moiety. This assumption needs further
investigation.
Fig. 2 1H-2D-NOESY of 12, showing a cross peak between the two
terminal allylic protons Ha and Hb that permits one to assign a syn–syn
conformation. The analysis of these data revealed moreover the absence
of exchange peaks which confirmed the presence of only one isomer.
The diagonal peaks are negative NOE peaks. A colour version is
available as ESI.†
In the species 12 the two diphenylallyl ligands assume the
same exo syn–syn conformations.
As far as the ligand (Ra,Ra)-1 is concerned, their pal-
ladium() derivatives are present in CDCl3 solution as a mix-
ture of binuclear and mononuclear species. As shown in Fig. 3,
the 31P{1H} NMR spectrum reveals the presence of two major
isomers (Table 1) with at least other three isomers in very low
concentration [a singlet (ꢀ) at δ 173.3; two doublets (ᮀ) at
δ 178.3 and 171.2 (2JPaPb = 73 Hz); two doublets (×) at δ 177.3
and 171.3 (2JPaPb = 62 Hz)].
All of the resonances for the major isomers were assigned by
2D homo-(1H NOESY and COSY) and heteronuclear-(13C–1H
and 31P–1H) NMR spectroscopies: (i) the binuclear structure
with an exo syn–syn configuration for both the allylic fragments
(᭺), (ii) the mononuclear species with an exo syn–syn conform-
ation (∆). The similarity in the 31P{1H} NMR pattern of signals
between major and minor species (∆ vs. ꢀ; ᭺ vs. ᮀ and ×) led
us to reasonably hypothesise a monomeric species for ꢀ and
dimeric species for ᮀ and ×. This conclusion is also supported
D a l t o n T r a n s . , 2 0 0 4 , 8 1 – 8 9
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The (Ra,Sc)-5 ligand gave only a modest induction of enantio-
selectivity (18% e.e.). This is due to the features of the ligand
that presents two chemically unequivalent phosphorous atoms
(phosphonite–phosphine); the electronic characteristics of the
two phosphorous atoms make the two terminal allyl carbon
atoms different to nucleophilic attack. The low e.e. value is cer-
tainly related to the presence of 11, in CHCl2 solution, as two
conformers, in different concentration. It cannot be forgotten
that processes involving different conformers, have an activ-
ation energy that determines the relative reaction rates.21
The product of the dimethylmalonate attack on the catalytic
binuclear species 12 was obtained with an e.e. of 57.1% in the S
form, at room temperature. Although far away from the best
results obtained in the allylic alkylation catalysis, the e.e. value
obtained with such a binuclear system containing the short-bite
ligand (Ra,Ra)-2, it does merit some consideration. In the
species 12, the greater nucleophilicity of the syn–syn allylic
carbons has been shown by the low field position of 13C reson-
ances; 13C NMR spectra indicate also that in the syn–syn allylic
moiety the more deshielded carbon Cb is also the more favoured
site for the nucleophilic attack, due to the less steric hindrance
brought about by the closer (Ra)-binaphthyl fragment (see
Fig. 4).
Although the difference due to large binaphthyl groups should
be considered, these structures support the possibility that in
the [Pd(η3-PhCHCHCHPh)(µ-Ra,Ra-2)]22ϩ species, the (Ra,Ra)-
2 ligands are forced to adopt a strain and rigid conformation
which places the binaphthyl groups in such a positions to
produce differences in the terminal allyl carbon atoms.
In order to have further inside information on the strain of
bridged pyrophosphite ligand in the species 12, we have per-
formed a semiempirical calculation on the analogous molecule
containing biphenyl group instead of binaphthyl moiety. The
differences between real binaphthyl species and the biphenyl-
minimized model do not cause different results, having sub-
sequently verified that the further phenylic groups present in the
binaphthyl do not give interactions with the phenylic groups of
the palladium–allyl moiety; in fact, the aforesaid groups are
directed toward the less congested region of the molecule. The
PM3 optimised geometry is shown in Fig. 4. The salient struc-
tural parameters are the two distance Pd1–Ca 2.249 and Pd1–Cb
2.187 (Ca and Cb are the terminal allylic carbon atoms bounded
to the same palladium centre). The different Pd–C distances are
determined by the orientation assumed by the binaphthyl
groups bound to phosphorous atoms to avoid interactions with
phenyl–allylic groups. This is supported by the different dis-
tances between the palladium and the binaphthyl-aromatic
moieties nearly to this metal centre.
The nucleophilic attack being external, it is possible to
exclude cooperative processes between the two metals as factors
determining the enantiomeric excess.26
Conclusions
We synthesised new chiral 1,1-diphosphonitomethane, pyro-
phosphite, bis-diphosphonito- and mixed phosphonito-
phosphinoamines short-bite ligands and tested their behaviour
in the palladium–allyl catalysed alkylation reaction of 1,3-
bis(phenyl)-1,2-propenylacetate by dimethylmalonate. As
expected, the coordinated short-bite (Sc)-3, (Ra,Ra)-4a and
(Ra,Ra,Sc)-4b ligands induces high symmetry in the allylic
catalytic species [Pd(PhCHCHCHPh)(L–Lshort-bite)]ϩ; the rigid
four-atom metallacycle formed further supports the lack of
different conformational isomers in solution. In these condi-
tions, the nucleophilic attack affords the product as a racemic
mixture.
For the first time in the literature, we have considered a
binuclear palladium allyl species containing two short-bite
bridging ligands as key catalytic species in the nucleophilic
attack reaction. In fact, with (Ra,Ra)-2 pyrophosphite ligand,
the binuclear palladium–allyl species [Pd(η3-PhCHCH-
CHPh)(µ-Ra,Ra-2)]22ϩ, in which each palladium atom is co-
ordinated to an allylic group and to two phosphorus atoms
belonging to different bridging chiral ligand, was formed. This
situation seems analogous to the coordination mode of two
monodentate phosphonite chiral ligand to the palladium–allyl
centre. In the [Pd2(µ-Ra,Ra-2)2] framework, the ligands assume
a strained and rigid arrangement to allow coordination of
the allyl moiety in a nearly square planar palladium() co-
ordination plane. The strained arrangement assumed by the
bridging chiral bidentate ligands in the species [Pd(η3-PhCH-
Fig. 4 Minimized structure of the Pd–allyl complex 12 in which is seen
the repulsions between the allylic-phenyl group and the biphenyl moiety
bound to the phosphorous atom acting mostly on one side. A colour
version is available as ESI.†
In the binuclear palladium–allyl species [Pd(η3-PhCHCH-
CHPh)(µ-Ra,Ra-2)]22ϩ, the η3-coordination of the allyl moieties
requires that the P–Pd–P angles are nearly 90Њ and that the
(Ra,Ra)-2 ligands assume a nearly cis coordination to the pal-
ladium() centre. The only X-ray structural data reported for
complexes similar to the binuclear palladium–allyl 12 support
this finding. In fact, in the cations {[bis(η3-2-methylallyl)]Pd2-
[µ-(diphenylphosphino)-methane][µ-(pyridine-2-thiolate)]} and
{[bis-(η3-2-methylallyl)]Pd2[µ-(diphenylphosphino)methane]-
[µ-(phenylthiolate)]} complexes, the angle values found for the
bridging ligands are N–Pd–P 96.5 and 87.2Њ and P–Pd–S 95.3
and 92.0Њ.22 Besides, bis-allyl binuclear complexes have been
obtained in the presence of only one bridging ligand and a
metal–metal bond.23
2ϩ
CHCHPh)(µ-Ra,Ra-2)]2 induces differences in the terminal
carbon atoms of the coordinated allyl moieties. As result, the
product of the nucleophilic attack, the 2-(1,3-diphenylallyl)-
dimethylmalonate, was obtained with a significant e.e.
The difference observed with the ligand (Ra,Ra)-2, compared
to ligands having carbon, nitrogen or oxygen as spacer, could be
correlated to the different P–X–P angle value. A literature
research reports that P–O–P diphosphoxane ligands are always
bounded to the metal centre in a bridging fashion.24 The species
[M2((OR)P(O)OP(O)(OR))n] (n = 2, 4; M = Pd, Pt; R = H, Et)
have been characterized by X-ray structural determination.25
Experimental
General methods
All manipulation were carried out under an argon atmosphere
using standard Schlenk techniques. Freshly distilled solvents
were used throughout and dried by standard procedures.
D a l t o n T r a n s . , 2 0 0 4 , 8 1 – 8 9
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Published methods were used to prepare the compounds (Sc)-4-
chloro-3,5-dioxa-4-phosphacycloepta[2,1-a;3,4-aЈ]dinaphthal-
ene,27 [Pd(η3-PhCHCH–CHPh)(µ-Cl)]2.24b All other reagents
were purchased from Sigma-Aldrich and Strem and were
used as supplied. For column chromatography, silica gel 60
(220 440 mesh) purchased from Fluka was used. 1D and 2D
NMR experiments were carried out using a Bruker AMX R300
spectrometer. 1H NMR spectra were referenced to internal
tetramethylsilane and 31P{1H} spectra to external 85% H3PO4.
viscous oil was washed with hexane and dried. Yield 73%
(0.632 g, 0.88 mmol). 1H NMR (CDCl3): δ 7.65 – 6.71 (m, 29H,
Ar–H). 31P{1H} NMR (CDCl3): δ 136.9. Anal. calcd. for
C46H29NO4P2 (721.67): C, 76.56; H, 4.05; N, 1.94. Found: C,
76.48; H, 4.21; N, 1.97%.
(Ra,Ra)-N,N-di(3,5-dioxa-4-phosphacycloepta[2,1-a;3,4-aЈ]di-
naphthyl)-(Sc)-sec-butylamine, (Ra,Ra,Sc)-4b. To a toluene (25
ml) solution of (Ra)-6 (0.8417 g, 2.4 mmol), (Sc)-(ϩ)-2-butyl-
amine (0.0877 g, 1.2 mmol) and NEt3 (0.8841 g, 8.7 mmol) were
dropwise added at 0 ЊC. The reaction mixture was stirred at this
temperature for 1 h; after this period, the solution was warmed
at room temperature and filtered. The solution was dried in
vacuo and washed with hexane to obtain a white solid. Yield
1
Standard pulse sequences were employed for H-2D-NOESY,
13C–1H- and 31P–1H-correlation studies.28 Elemental analyses
were performed by Redox s.n.c., Cologno Monzese, Milano.
Preparations
1
75% (0.631 g, 0.90 mmol). H NMR (CDCl3): δ 7.63–6.82 (m,
(Ra,Ra)-di-(3,5-dioxa-4-phosphacycloepta[2,1-a;3,4-aЈ]dinaph-
thyl)methane, (Ra,Ra)-1. To a toluene (30 ml) solution of (Ra)-
2,2Ј-di-hydroxybinaphthyl (1.00 g, 3.5 mmol) was added at
room temperature bis(dichlorophosphino)methane (0.3811 g,
1.7 mmol) and NEt3 (0.8841 g, 8.7 mmol). The reaction mixture
solution was stirred overnight and, at the end, a white muddy
colour was formed. After filtration under argon, the solution
was evaporated under reduced pressure and the crude product
was washed with petroleum ether and dried in vacuo. The
product was obtained as a white solid in 90% yield (0.986 g,
24H, Ar–H), 2.97 (m, 1H, CH), 1.18 (m, 1H, CH2), 0.58 (m, 1H,
3
3
CH2), 0.40 (d, J 6 Hz, 3H, CH3), 0.35 (t, J 7 Hz, 3H, CH3).
31P{1H} NMR (CDCl3): δ 138.0. Anal. calcd. for C44H33NO4P2
(701.68): C, 75.31; H, 4.74; N, 2.00. Found: C, 75.28; H, 5.31;
N, 1.86%.
(Ra,Sc)-(dinaphthylphosphonito)(diphenylphosphino)-sec-
butylamine, (Ra,Sc)-5. A toluene (10 ml) solution of (Sc)-(ϩ)-
sec-butylamine (0.146 g, 2 mmol) and NEt3 (0.311 g, 3 mmol)
was dropwise treated with (Ra)-6 (0.7367 g, 2 mmol) toluene
(15 ml) solution at 0 ЊC. The reaction course was followed by
NMR spectra. When the substitution of the first hydrogen of
amine occurred (2 h), the reaction was warmed at room tem-
perature. After this period the solution was again cooled at 0 ЊC
adding dropwise a PCl(Ph)2 (0.452 g, 2 mmol) toluene (5 ml)
solution and NEt3 (0.311 g, 3 mmol). After 1.5 h, the solution
was warmed at room temperature and stirred overnight. The
formed Et3NؒHCl was removed by filtration and the residue
was washed for 3 times with hexane (15 ml) to obtain a white
1
1.5 mmol). H NMR (CDCl3): δ 7.60–6.91 (m, 24H, Ar–H),
3
2.38 (t, J 7 Hz, 2H, CH2). 31P{1H} NMR (CDCl3): δ 204.0.
Anal. calcd. for C41H26O4P2 (644.59): C, 76.40; H, 4.07. Found:
C, 76.50; H, 4.38%.
(Ra,Ra)-bis-dinaphthylpyrophosphite, (Ra,Ra)-2. The phos-
phorochloridite (Ra)-6 (1.123 g, 3.2 mmol), dissolved in 5 ml of
THF, was reacted with the stoichiometric amount of H2O
(0.576 g, 3.2 mmol) in the presence of NEt3 (0.325 g, 3.2 mmol).
The reaction mixture was stirred for 2 h and subsequently
added of sodium hydride in THF to afford the pyrophosphate
sodium salt. Then the mixture was treated with (Ra)-6 (1.123 g,
3.2 mmol) in a 1 : 1 molar ratio and was monitored by 31P{1H}
and stirred overnight. The solution was filtered under argon
and evaporated under reduced pressure. The obtained viscous
oil was washed with hexane and dried in vacuo to give the pyro-
1
powder. Yield 45% (0.514 g, 0.90 mmol). H NMR (CDCl3):
δ 8.04–7.95 (m, 22H, Ar–H), 3.04 (m, 1H, CH), 1.12 (m, 1H,
3
CH2), 0.62 (m, 1H, CH2), 0.50 (d, J 6 Hz, 3H, CH3), 0.41 (t,
3J 7 Hz, 3H, CH3). 31P{1H} NMR (CDCl3): δ 148.5 (d, 2JPP 28
2
Hz); δ 31.5 (d, JPP 28 Hz). Anal. calcd. for C36H31NO2P2
(571.58): C, 75.65; H, 5.47; N, 2.45. Found: C, 76,75; H, 6.49;
N, 2.77%.
1
phosphite in high yield (82%; 1.696 g, 2.62 mmol). H NMR
3
[Pd(ꢀ3-PhCHCHCHPh)(Ra,Ra-1)]PF6, 7. The following pro-
cedure for the preparation of 7 is representative and the [Pd-
(CDCl3): δ 7.60–6.91 (m, 22H, Ar–H), 2.38 (t, J 7 Hz, 2H,
CH2). 31P{1H} NMR (CDCl3): δ 145.4. Anal. calcd. for
C40H24O5P2 (646.56): C, 74.30; H, 3.74. Found: C, 74.25; H,
3.78%.
(η3-PhCHCHCHPh)(L–Lshort-bite)]PF6 complexes (L–Lshort-bite
=
(Ra,Ra)-1, (Sc)-3, (Ra,Ra)-4a, (Ra,Ra,Sc)-4b, (Ra,Sc)-5) were
synthesised in a similar manner.
This complex was synthesised by reaction of [Pd(η3-PhCH-
CHCHPh)Cl]2 (0.300 g, 0.043 mmol) with the ligand (Ra,Ra)-1
(0.055 g, 0.086 mmol) in CH2Cl2 (25 ml) at room temperature.
After 1 h AgPF6 (0.217 g, 0.086 mmol) was added and was
stirred for 10 min. The suspension was filtered through a pad of
Celite, the solvent evaporated in vacuo except for a few milli-
litres, and the product precipitated with hexane. Recrystallized
from CH2Cl2/hexane in a 3 : 1 ratio, an orange powder was
obtained. Yield 72% (0.016 g, 0.015 mmol). Anal. calcd. for
C56H40F6O4P3Pd (1090.25): C, 61.69; H, 3.70. Found: C, 51.88;
H, 3.78%.
N,N-bis(diphenylphosphine)-(Sc)-sec-butylamine, (Sc)-3. To a
toluene (20 ml) solution of (Sc)-sec-butylamine (1.00 g, 13.7
mmol) and NEt3 (4.16 g, 41.1 mmol), at 0 ЊC, a solution of
PPh2Cl (6.05 g, 27.4 mmol) in 30 ml of the same solvent was
dropwise added. The reaction mixture was stirred for 1 h, and
after which it was warmed at room temperature for 2 h. Sub-
sequently the solution was filtered to remove the formed Et3Nؒ
HCl and the filtrate was dried in vacuo. The obtained oil was
dissolved in ice/methanol and recrystallized from methanol/
ether to afford white crystals of product. Yield 75% (4.55 g,
1
10.3 mmol). H NMR (CDCl3): δ 7.30 (m, 20H, Ar–H), 3.37
(m, 1H, CH), 1.78 (m, 1H, CH2), 1.25 (m, 1H, CH2), 1.20 (d,
3
3J 6 Hz, 3H, CH3), 0.65 (t, J 7 Hz, 3H, CH3). 31P{1H} NMR
[Pd(ꢀ3-PhCHCHCHPh)(Sc-3)]PF6, 8. Anal. calcd. for
C43H43F6NP3Pd (887.14): C, 58.22; H, 4.89; N, 1.58. Found: C,
58.88; H, 4.88; N, 1.53%.
(CDCl3): δ 49.6 (broad). Anal. calcd. for C28H29NP2 (441.48): C,
76.17; H, 6.62; N, 3.17. Found: C, 76.56; H, 6.38; N, 3.21%.
(Ra,Ra)-N,N-di(3,5-dioxa-4-phosphacycloepta[2,1-a;3,4-aЈ]di-
naphthyl)phenyl-amine, (Ra,Ra)-4a. To (Ra)-6 (0.842 g, 2.4
mmol) toluene (25 ml) solution, PhNH2 (0.1117 g, 1.2 mmol)
and NEt3 (0.8841 g, 8.7 mmol) was dropwise added at 0 ЊC. The
mixture was stirred at low temperature for 1 h and then it was
warmed at room temperature. The solution was filtered under
argon and evaporated under reduced pressure. The obtained
[Pd(ꢀ3-PhCHCHCHPh)(Ra,Ra-4a)]PF6, 9. Anal. calcd. for
C61H43F6NO4P3Pd (1167.33): C, 62.76; H, 3.71; N, 1.20. Found:
C, 62.78; H, 3.78; N, 1.23%.
[Pd(ꢀ3-PhCHCHCHPh)(Ra,Ra,Sc-4b)]PF6, 10. Anal. calcd.
for C59H47F6NO4P3Pd (1147.34): C, 61.76; H, 4.13; N, 1.22.
Found: C, 61.81; H, 4.18; N, 1.23%.
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[Pd(ꢀ3-PhCHCHCHPh)(Ra,Sc-5)]PF6, 11. Anal. calcd. for
C51H45F6NO2P3Pd (1017.24): C, 60.22; H, 4.46; N, 1.38. Found:
C, 60.28; H, 4.48; N, 1.33%.
R. Scopelliti, C. G. Arena, G. Bruno, D. Drommi and F. Faraone,
Organometallics, 1998, 17, 338.
4 A literature search indicates more than thousand articles for
the dppm ligand. Here are reported some pioneering works:
(a) J. P. Farr, M. M. Olmstead and A. L. Balch, J. Am. Chem. Soc.,
1980, 12, 6654; (b) J. P. Farr, F. E. Wood and A. Balch, Inorg. Chem.,
1983, 22, 3387; (c) A. Maisonnet, J. P. Farr, M. M. Olmstead,
C. T. Hunt and A. L. Balch, Inorg. Chem., 1982, 21, 3961; (d ) J. P.
Farr, M. M. Olmstead, F. E. Wood and A. L. Balch, J. Am. Chem.
Soc., 1982, 21, 3961; (e) A. Maisonnet, J. P. Farr and A. L.
Balch, Inorg. Chim. Acta, 1981, 53, L217; ( f ) M. L. Kullberg
and C. P. Kubiak, Organometallics, 1984, 3, 632; (g) A. Mishara
and U. C. Agarwala, Inorg. Chem., 1990, 170, 209; (h) C. H.
Lindsay, L. S. Benner and L. Balch, Inorg. Chem., 1980, 19,
3505.
[Pd(ꢀ3-PhCHCHCHPh)(Ra,Ra-2)]2(PF6)2, 12. This complex
was prepared analogously to 7 from [Pd(η3-PhCHCHCH-
Ph)Cl]2 (0.300 g, 0.043 mmol), the ligand (Ra,Ra)-2 (0.056 g,
0.086 mmol) in CH2Cl2 (25 ml) and AgPF6 (0.217 g, 0.086
mmol). The yellow–orange powder was obtained with 82%
yield (0.039 g, 0.018 mmol). Anal. calcd. for C110H76F12O10-
P6Pd2 (2184.44): C, 60.48; H, 3.51. Found: C, 60.51; H, 3.48%.
Palladium-catalysed allylic alkylation. General procedure
5 (a) U. Anandhi, T. Holbert, D. Lueng and P. R. Sharp, Inorg. Chem.,
2003, 42, 1282; (b) P. Bhattacharyya and D. J. Woollins, Polyhedron,
1995, 14, 3367; (c) M. L. McKee and W. E. J. Hill, Phys. Chem. A,
2002, 106, 6201; (d ) E. J. Sekabunga, M. L. Smith, T. R. Webb
and W. E. Hill, Inorg. Chem., 2002, 41(5), 1205; (e) W. M. Xue,
F. E. Kuhn, G. Zhang and H. Eberhardt, J. Organomet. Chem.,
2000, 596, 177; ( f ) F. A. Cotton, F. E. Kuhn and A. Yokochi,
Inorg. Chim. Acta, 1996, 252, 251; (g) C. S. Browning and
D. H. Farrar, J. Chem. Soc., Dalton Trans., 1995, 521; C. S.
Browning and D. H. Farrar, J. Chem. Soc., Dalton Trans., 1995,
2005; (h) I. Haiduc and I. Silaghi-Dimitrescu, Coord. Chem. Rev.,
1986, 74, 127.
6 For example: (a) J. P. Farr, M. M. Olmstead and A. L. Balch, J. Am.
Chem. Soc., 1980, 102, 6655; (b) J. P. Farr, M. M. Olmstead, C. H.
Hunt and A. L. Balch, Inorg. Chem., 1981, 20, 1182; (c) J. P. Farr,
M. M. Olmstead and A. L. Balch, Inorg. Chem., 1983, 22, 1229;
(d ) J. P. Farr, M. M. Olmstead, N. M. Rutherford, F. E. Wood and
A. L. Balch, J. Am. Chem. Soc., 1983, 105, 792; (e) J. P. Farr, M. M.
Olmstead, N. M. Rutherford, F. E. Wood and A. L. Balch,
Organometallics, 1983, 2, 1758; ( f ) G. Bruno, S. Lo Schiavo,
E. Rotondo, C. G. Arena and F. Faraone, Organometallics, 1989, 8,
886; (g) E. Rotondo, S. Lo Schiavo, G. Bruno, C. G. Arena,
R. Gobetto and F. Faraone, Inorg. Chem., 1989, 28, 2944; (h) T. J.
Bander, F. A. Cotton, G. L Powell, S. M. Tetrick and R. A. Walton,
J. Am. Chem. Soc., 1984, 106, 1323; (i) J. T. Mague, Inorg. Chem.,
1989, 28, 2215; (j) N. Lugan, G. Lavigne, J. J. Bonnet, R. Reau,
D. Neibecker and I. Tkatchenko, J. Am. Chem. Soc., 1988, 110,
5369; (k) A. Dervisi, P. G. Edwards, P. D. Newman, R. P. Tooze, S. J.
Coles and M. B. Hursthouse, J. Chem. Soc., Dalton Trans., 1998,
3771; (l ) S. M. Kuang, H. Cheng, L. J. Sun, Z. Y. Zhou, B. M. Wu
and T. C. W. Mak, Polyhedron, 1996, 15, 3417; (m) C. G. Arena,
E. Rotondo, F. Faraone, M. Lanfranchi and A. Tiripicchio,
Organometallics, 1991, 10, 3877; (n) C. G. Arena, G. Bruno, G. De
Munno, E. Rotondo, D. Drommi and F. Faraone, Inorg. Chem.,
1993, 32, 1601.
In a 30 ml Schlenk tube equipped with magnetic stirring bar,
under argon, [Pd(η3-C3H5)Cl]2 (2.34 mg, 0.0064 mmol) was
treated with the L–Lshort-bite ligand (0.0128 mmol) in CH2Cl2
(0.7 ml). The solution was degassed (three freeze–thaw cycles)
and stirred for half an hour. After this period, to the solution
was sequentially added the 1,3-diphenyl-1-acetoxypropene
(323 mg, 1.28 mmol), dimethyl malonate (338.2 mg, 2.56
mmol), N,O-bis(trimethylsilyl)acetamide (520.8 mg, 2.56
mmol), and KOAc (6 mg, 0.06 mmol) and then degassed (three
freeze–thaw cycles). The reaction was monitored by TLC
(eluent: hexane/AcOEt 3 : 1) and, at the end, the mixture was
diluted with Et2O and extracted with two portions of ice-cold
saturated aqueous NH4Cl solution. The solution was dried
(MgSO4) and evaporated in vacuo; the residue was purified by
column chromatography (silica gel, 4×30 cm, hexane/AcOEt
3 : 1) to afford the product as a colourless oil. The optical purity
was determinated by NMR using paramagnetic shift reagent
[Eu(hfbc)3]. Assignment of the absolute configuration was
made by the sign of the optical rotation.
Computational methods
All calculations were carried out on either a Mac G4 running
the Spartan 5.0.1 software obtained from Wavefunction29 and
on a PC PENTIUM IV using the CaChe software.30 The start-
ing geometries of compound 12 were built by Spartan. The
PM3 Hamiltonian was employed in both of the programs,
used for geometry optimisation with appropriate molecular
charge and multiplicity, which provide the same geometry.
7 (a) Y. Yamanoi and T. Imamoto, J. Org. Chem., 1999, 64, 2988;
(b) I. D. Gridnev, Y. Yamanoi, N. Higashi, H. Tsuruta, M. Yasutake
and T. Imamoto, Adv. Synth. Catal., 2001, 343, 118; (c) A. Marinetti,
C. Le Menn and L. Ricard, Organometallics, 1995, 14, 4983;
(d ) P. W. Lendnor, W. Beck, H. G. Fick and H. Zippel, Chem. Ber.,
1978, 111, 615; (e) N. C. Payne and D. W. Stephan, J. Organomet.
Chem., 1981, 221, 203.
References
1 (a) A. L. Balch, in Homogeneous Catalysis Using Metal Phosphine
Complexes, ed. L. H. Pignolet, Plenum Press, New York, 1983,
p. 167; (b) G. R. Newkome, Chem. Rev., 1993, 93, 2067; (c) R. J.
Puddephatt, Chem. Soc. Rev., 1983, 12, 99; (d ) B. Chaudret,
B. Delavaux and R. Poilblanc, Coord. Chem. Rev., 1988, 86, 191;
(e) M. S. Balakrishna, S. V. Reddy, S. S. Krishamurthy, J. F. Nixon
and B. St. Laurent, J. Coord. Chem. Rev., 1994, 129, 1; ( f ) M. Witt
and H. W. Roesky, Chem. Rev., 1994, 94, 1163.
2 For example: (a) B. R. Sutherland and M. Cowie, Organometallics,
1985, 4, 1801; (b) J. T. Mague, Organometallics, 1986, 5, 918;
(c) S. Lo Schiavo, G. Bruno, F. Nicolò, P. Piraino and F. Faraone,
Organometallics, 1985, 4, 2091; (d ) C. Arena, F. Faraone,
M. Lanfranchi, E. Rotondo and A. Tiripicchio, Inorg. Chem., 1992,
31, 4797; (e) M. Cowie, G. Vasapollo, B. R. Sutherland and J. P.
Ennett, Inorg. Chem., 1986, 25, 2648; ( f ) M. Cowie and T. G.
Southern, Inorg. Chem., 1982, 21, 246; (g) N. C. Payne and D. W.
Stephan, J. Organomet. Chem., 1981, 221, 203; (h) B. A. Vaartstra,
K. N. O’Brien, R. Eisenberg and M. Cowie, Inorg. Chem., 1988, 27,
3668; (i) D. J. Anderson, K. W. Kramarz and R. Eisenberg, Inorg.
Chem., 1996, 35, 2688; (j) J. R. Torkelson, F. H. Antwi-Nsiah,
R. McDonald, M. Cowie, J. G. Pruis, K. J. Jalkanen and R. L.
DeKock, J. Am. Chem. Soc., 1999, 121, 3666.
8 A. Maisonnet, J. P. Farr, M. M. Olmstead, C. T. Hunt and
A. L. Balch, Inorg. Chem., 1982, 21, 3961.
9 (a) D. M. Roundhill, R. P. Sperline and W. B. Beaulieu, Coord.
Chem. Rev., 1978, 26, 263; (b) C. G. Arena, F. Nicolò, D. Drommi,
G. Bruno and F. Faraone, J. Chem. Soc., Dalton Trans., 1996, 4357–
4363; (c) M. E. Grayson, C. A. Farley and C. Streuli, Tetrahedron,
1967, 23, 1065; (d ) H. Goldwhite, Introduction to Phosphorus
Chemistry, Cambridge University Press, Cambridge, 1981, 306–308;
(e) Mellor’s Comprehensive Treatise of Inorganic and Theoretical
Chemistry, Longmans, London, 1971, vol. 8, p. 984; ( f ) C. F. Callis,
J. R. Van Wazer, J. N. Shoolery and W. A. Anderson, J. Am. Chem.
Soc., 1957, 79, 2719.
10 A. D. DeBellis, S. D. Pastor, G. Rihs, R. K. Rodebaugh and
A. R. Smith, Inorg. Chem., 2001, 40, 2156.
11 (a) E. A. Arbuzov and B. A. Arbusow, Chem. Ber., 1932, 65, 195;
(b) V. L. Foss, A. Veits, N. V. Lukashev and I. F. Lutsenko,
Phosphorus Sulfur Relat. Elem., 1977, 3, 299.
12 (a) A. Berg and J. E. Griffiths, J. Am. Chem. Soc., 1962, 84, 3442;
(b) D. S. Irvine, C. Glidewell, D. J. Cole-Hamilton, J. C. Barnes and
A. Howie, J. Chem. Soc., Dalton Trans., 1991, 1765.
13 G. Calabrò, D. Drommi, C. Graiff, F. Faraone and A. Tiripicchio,
Eur. J. Inorg. Chem., in press.
14 (a) R. Keat, L. Manojlovic-Muir, K. W. Muir and D. S. Rycroft,
J. Chem. Soc., Dalton Trans., 1981, 2192 and references therein;
(b) R. J. Cross, T. H. Green and R. Keat, J. Chem. Soc., Dalton
3 (a) E. Drend, D. Arnoldy and P. H. M. Budzelaar, J. Organomet.
Chem., 1993, 455, 247; (b) Y. Gao, J. K. Kuncheria, H. A. Jenkins,
R. J. Puddephatt and G. P. A. Yap, J. Chem. Soc., Dalton Trans.,
2000, 3212–3217; (c) A. Scrivanti, V. Beghetto, E. Campagna,
M. Zenato and U. Matteoli, Organometallics, 1998, 17, 630–635;
(d ) M. E. Broussard, B. Juma, S. G. Train, W. Peng, S. A. Laneman
and G. G. Stanley, Science, 1993, 260, 1784; (e) G. Franciò,
D a l t o n T r a n s . , 2 0 0 4 , 8 1 – 8 9
88

View Article Online
Trans., 1976, 1424; (c) I. J. Colquhoun and W. McFarlane, J. Chem.
Soc., Dalton Trans., 1977, 1674.
15 R. P. Kamalesh Babu, S. S. Krishnamurthy and M. Nethaji,
Tetrahedron: Asymmetry, 1995, 6, 427.
23 (a) P. Braunstein, M. Knorr, P. Hermann and U. Schubert,
Organometallics, 1991, 10, 828 (b).
24 (a) A. Pfaltz, Acc. Chem. Res., 1993, 26, 339–345; (b) P. von Matt,
G. C. E. Lloyd-Jones, A. B. Minidis, A. Pfaltz, L. Macko,
M. Neuburger, M. Zehnder, H. Ruegger and P. Pregosin,
Helv. Chim. Acta, 1995, 78, 265.
16 (a) B. Trost and D. Van Vranken, Chem. Rev., 1996, 96, 395;
(b) G. Helmchen, S. Kudis, P. Sennhenn and H. Steinhagen, Pure
Appl. Chem., 1997, 69, 513; (c) P. Dierkes, S. Ramdeehul, L. Barloy,
A. De Cian, J. Fischer, P. C. J. Kamer, P. W. N. M. van Leeuwen and
J. A. Osborne, Angew. Chem., Int. Ed., 1998, 37, 3116; (d ) P. Dierkes,
S. Ramdeehul, R. Aguado, P. C. J. Kamer, P. W. N. M. van Leeuwen
and J. A. Osborne, Angew. Chem., Int. Ed., 1998, 37, 3118.
17 (a) M. Widhalm, U. Nettekoven, H. Kalchhauser, K. Mereiter,
M. J. Calhorda and V. Félix, Organometallics, 2002, 21, 315;
(b) G. Helmchen, J. Organomet. Chem., 1999, 576, 203–214;
(c) J. Sprinz, M. Kiefer, G. Helmchen, M. Reggelin, G. Huttner,
O. Walter and L. Zsolnai, Tetrahedron Lett., 1994, 35, 1523–1526;
(d ) C. Breutel, P. S. Pregosin, R. Salzmann and A. Togni, J. Am.
Chem. Soc., 1994, 116, 4067–4068.
25 (a) K. A. Alexander, S. A. Bryan, F. R. Fronczek, W. C. Fultz,
A. L. Rheingold, D. M. Roundhill, P. Stein and S. F. Watkins,
Inorg. Chem., 1985, 24, 2803; (b) Chi-Ming Che, T. C. W. Mak
and H. B. Gray, Inorg. Chem., 1984, 23, 4386; (c) D. E. Berry,
K. A. Beveridge, G. W. Bushnell, K. R. Dixon and A. Pidcock, Can.
J. Chem., 1986, 64, 343; (d ) Chi-Ming Che, Wai-Man Lee, T. C. W.
Mak and H. B. Gray, J. Am. Chem. Soc., 1986, 108, 4446;
(e) T. Gebauer, G. Frenzen and K. Dehnicke, Z. Naturforsch., B,
1993, 48, 1661; ( f ) N. Yasuda, M. Kanazawa, H. Uekusa and
Y. Ohashi, Chem. Lett., 2002, 1132; (g) Y. Ozawa, M. Terashima,
M. Mitsumi, K. Toriumi, N. Yasuda, H. Uekusa and Y. Ohashi,
Chem. Lett., 2003, 62.
18 The terms symmetrical and unsymmetrical refer to the constitution
of the allylic groups in the species π-allyl–palladium complexes.
19 P. S. Pregosin and R. Salzmann, Coord. Chem. Rev., 1996, 155, 35–
68.
20 J.-L. Vasse, R. Stranne, R. Zalubovskis, C. Gayet and C. Moberg,
J. Org. Chem., 2003, 68, 3258–3270.
21 (a) J. M. Brown, D. I. Hulmes and P. J. Guiry, Tetrahedron, 1994,
50, 4493–4506; (b) H. Hagelin, B. Åkermark and P.-O. Norrby,
Chem. Eur. J., 1999, 5, 902–909; (c) P. B. Mackenzie, J. Whelan and
B. Bosnich, J. Am. Chem. Soc., 1985, 107, 2046; (d ) A. Saitoh,
K. Achiwa, K. K. Tanaka and T. Morimoto, J. Org. Chem., 2000, 65,
4227–4240.
26 (a) A. Togni, U. Burckhardt, V. Gramlich, P. S. Pregosin and
R. Salzmann, J. Am. Chem. Soc., 1996, 118, 1031; (b) J. V. Allen,
S. J. Coote, G. J. Dawson, G. C. C. J. Martin Frost and J. M.
Williams, J. Chem. Soc., Perkin Trans., 1994, 2065; (c) A. Chesney,
M. R. Bryce, R. W. J. Chubb, A. S. Batsanov and J. A. K. Howard,
Tetrahedron: Asymmetry, 1997, 8, 2337; (d ) G. J. Dawson and
J. M. J. Williams, Tetrahedron: Asymmetry, 1995, 6, 2535.
27 G. Franciò, C. G. Arena, F. Faraone, C. Graiff, M. Lanfranchi and
A. Tiripicchio, Eur. J. Inorg. Chem., 1999, 1219.
28 V. SklenaÁr, H. Miyashiro, G. Zon, H. T. Miles and A. Bax, FEBS
Lett., 1986, 208, 94.
29 Spartan version 5.0, Wavefunction, Inc., Irvine, CA, 1997.
30 CAChe version 5.03, CAChe Chemistry Products, Oxford
Molecular Ltd. Fujitsu, 2002.
22 F. Gomez de la Torre, Y. Gutierrez, F. A. Jalon, B. R. Manzano and
A. Rodriguez, Monatsh. Chem., 2000, 131, 1267.
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89