Quinolinophane-derived alkyldiphenylphosphines: two homologous P,N-planar chiral ligands for palladium-catalysed allylic alkylation

Article abstract of DOI:10.1016/j.tetasy.2007.07.005

Two novel homologous [2]paracyclo[2](5,8)quinolinophane-derived P,N-bidentate planar chiral ligands have been synthesised and their effectiveness in asymmetric catalysis tested in palladium-catalysed allylic malonylation of 1,3-diphenylpropenyl acetate. T

Full text of DOI:10.1016/j.tetasy.2007.07.005

Tetrahedron: Asymmetry 18 (2007) 1742–1749
Quinolinophane-derived alkyldiphenylphosphines: two homologous
P,N-planar chiral ligands for palladium-catalysed allylic alkylation
a,
b
a
*
Renzo Ruzziconi, Claudio Santi and Sara Spizzichino
a
Dipartimento di Chimica Universit a` di Perugia, via Elce di Sotto, 8, 06123 Perugia, Italy
Dipartimento di Chimica e Tecnologia del Farmaco, via Elce di Sotto, 8, 06123 Perugia, Italy
b
Received 2 July 2007; accepted 9 July 2007
Abstract—Two novel homologous [2]paracyclo[2](5,8)quinolinophane-derived P,N-bidentate planar chiral ligands have been synthesised
and their effectiveness in asymmetric catalysis tested in palladium-catalysed allylic malonylation of 1,3-diphenylpropenyl acetate. The
extent of asymmetric induction depends linearly on the ligand/metal molar ratio, indicating the involvement of P,P-type and chelate
P,N-type p-allylpalladium complexes in equilibrium. The length of the chain that binds the diphenylphosphine group to the quinolino-
phane moiety, while appreciably affecting the P,N-complex stability, has little effect on the extent of asymmetric induction, which is due
to the greater reactivity of the [PN]-exo–syn–syn– ([PN]xss) with respect to the [PN]-endo–syn–syn– ([PN]nss) p-allylpalladium complex.
ꢀ
2007 Elsevier Ltd. All rights reserved.
1
. Introduction
To date, most investigations dealing with this class of
ligands have been focused on chiral ferrocene derivatives,
in which planar chirality is almost always associated with
central chirality by a 4-alkyl- or 4-aryl-substituted oxazo-
line ring bonded to the ferrocene nucleus and located near
Enantioselective palladium-catalysed allylic alkylation is
one of the most valuable tools for stereoselective carbon–
carbon bond-forming reactions. To this end, many types
of chiral ligands have been employed, among which the
P,N-bidentate ones have been the most pursued, as testified
by the myriad of chelating ligands tested in different enan-
tioselective allylic alkylation reactions during the last dec-
ade. The main reason for the increased interest in this
class of ligands is the electronic differentiation of the elec-
trophilic sites in square planar P,N-chelate allylpalladium
1
8
the diphenylphosphino group.
In spite of the substantial rigidity of the [2.2]paracyclo-
phane backbone and its marked stability towards oxidation
and relatively high temperatures, compared to the metallo-
cene-based ligands, [2.2]paracyclophane derivatives have
only received attention as planar chiral ligands of transi-
2
3
9
complexes. This is due to the different abilities of nitrogen
tion-metal catalysts during the last decade. Chiral P,P-,
and phosphorus to act as donor centres, as attack occurs
regioselectively at the allylic terminus opposite to the phos-
phorus atom, which leads to the enantioselective formation
N,O-, N,P- and N,N-type [2.2]paracyclophane-based
ligands have been used in different transition-metal-cataly-
sed stereoselective processes such as hydrogenation of car-
4
10
of the alkylated product.
bon–carbon double bonds, regio- and enantioselective
1
1
12
epoxidations, allylic alkylations, and diethylzinc addi-
5
13
Chiral phosphine–oxazoline ligands, developed by Pfaltz,
Helmchen
tions to aliphatic and aromatic aldehydes, as well as
ketone hydrosilylation. During our research in the field
2
b,4b,6
7
14
and Williams have been the basis for
many variants, which have the common feature of a 4-
substituted oxazoline ring as an asymmetric element
bonded to an aryldiphenylphosphine moiety. Several
P,N-bidentate planar chiral ligands have also been synthes-
ised and tested in asymmetric allylic alkylation reactions.
of planar chiral ligands, special attention has been given
to chiral derivatives of [2]paracyclo[2](5,8)quinolino-
1
5
phane. This planar chiral heterocyclic compound was
first used by V o¨ gtle and Pfaltz to prepare enantiomerically
pure 2-(pyridin-2-yl)-[2]paracyclo[2](5,8)quinolinophane, a
N,N-bidentate ligand which was used in both copper-catal-
ysed asymmetric cyclopropanation and iridium-catalysed
1
6
*
0
Corresponding author. E-mail: ruzzchor@unipg.it
asymmetric transfer-hydrogenation reactions. We were
957-4166/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2007.07.005

R. Ruzziconi et al. / Tetrahedron: Asymmetry 18 (2007) 1742–1749
1743
attracted by this uncommon system, reasoning that, with
1. BuLi
respect to planar 4,5-disubstituted [2.2]paracyclophane-
based bidentate ligands (Fig. 1a), the quinolinophane moi-
ety would allow the metal reaction centre to be orientated
towards the stereogenic ethylenic bridge (Fig. 1b), there-
fore, inducing a higher stereoselectivity.
2. ClPPh2
.
3
. BH3 OMe2
Et2O, 0°C
N
N
(
R)-3
(R)-4 Ph2PBH3
DABCO
C6H6, 40°C
a
b
H
H
H
H
N
H
H
H
H
L2
M
(R)-1
Ph2P
N
M
L1
L1
Scheme 2.
Figure 1.
The ability of ligand (R)-1 to induce stereoselectivity was
tested in the classical palladium-catalysed alkylation of
racemic 1,3-diphenyl-2-propenyl acetate 5 with dimethyl
malonate anion, which gave a non-racemic mixture of
methyl (E)-2-methoxycarbonyl-3,5-diphenylpent-4-enoate
6 (Scheme 3). The palladium complex catalyst (5 mol %
with respect to substrate) was prepared by mixing the allyl-
Accordingly, some enantiomerically pure (R )- and (S )-
p
p
2
-hydroxymethyl-4-methyl-[2]paracyclo[2](5,8)quinolino-
phanes were successfully used in the addition of diethylzinc
to aromatic and aliphatic aldehydes to produce excellent
1
7
standards of enantioselectivity. These encouraging results
prompted us to extend our investigation to planar chiral
quinolinophanephosphine ligands in order to assess their
effectiveness in stereoselective processes, as well as to inves-
tigate the effect that planar chirality has on the extent of
asymmetric induction. Herein, we report the synthesis of
two novel homologous planar chiral quinolinophane-
phosphine ligands (R)-1 and (R)-2 (Scheme 1), and its
effectiveness in palladium-catalysed enantioselective allyllic
alkylation reactions was also investigated.
3
19
palladium chloride dimer [Pd(g -C H )Cl]
with 2 equiv
3
5
2
of ligand (R)-1 in dichloromethane (L/M = 1).
OAc
Ph
Ph
(+)-5
-
CH2(CO2Me)2/
BSA/KOAc/5%
(
R)-1-Pd cat.
CH2Cl2, 0°C
MeO2C
Ph
CO2Me
Ph
MeO C
CO Me
2
2
+
N
Ph2P
R)-1
N
Ph2P
(R)-2
Ph
Ph
(
(S)-(-)-6
(R)-(+)-6
Scheme 1.
Scheme 3.
The nucleophilic species was generated in situ from
2
. Results and discussion
dimethyl malonate and N,O-bis(trimethylsilyl)acetamide
(
BSA, 3 equiv) in the presence of a catalytic amount of
2
0
The versatile (R)-(+)-2,4-dimethyl-[2]paracyclo[2](5,8)-
quinolinophane 3, which can be prepared on a multigram
scale from enantiomerically pure (R)-(ꢀ)-4-amino[2.2]para-
potassium acetate, using the Trost procedure. Under such
conditions, there was 20% enantiomeric excess (ee) of the
alkylated product in favour of the (R)-(+) enantiomer after
24 h, as determined by chromatographic analysis of the
crude reaction mixture. The same result was obtained in
two separate experiments in which the ligand/metal (L/
M) molar ratio was increased to 1.5 and finally to 2.0.
However, at L/M ratios less than 1.0, there was a linear
drop in the ee values until at L/M = 0.5 and essentially a
racemic mixture was obtained. If the L/M ratio decreased
further, the ee increased linearly, but instead the enantio-
mer (S)-6 was formed as the main alkylation product. Data
are reported in Table 1 and plotted in Figure 2 (plot a).
1
7b
cyclophane,
is a suitable precursor for both ligands 1
and 2. Deprotonation of 3 with butyllithium in diethyl
ether, at 0 ꢁC, involved the methyl group adjacent to the
nitrogen, giving the 2-lithiomethylquinolinophane interme-
1
7,18
diate, exclusively.
The latter gave the (quinolinophan-
2
8
-yl)methyldiphenylphosphine borane complex (R)-4 in
2% yield, at which point chlorodiphenylphosphine, and
then the BH ÆOMe complex were added to the reaction
3
2
mixture (Scheme 2). Finally, after the resulting air-stable
borane complex (R)-4 had been carefully purified by
column chromatography, it was treated with DABCO, to
obtain the expected quinolinophanephosphine (R)-1 in
A similar trend has already been observed by Burgess in an
2
1
8
7% yield.
analogous study that made use of JM-Phos as ligand. It

1744
R. Ruzziconi et al. / Tetrahedron: Asymmetry 18 (2007) 1742–1749
Table 1. Enantiomeric excess in the malonylation of 1,3-diphenyl-2-
propenyl acetate catalysed by [(R)-1]–Pd complex
a
b
c
L/Pd
Time (h) Conversion (%) ee (%) Major enantiomer
+
N
—
3
3
3
3
3
3
3
0
100
100
100
100
90
—
20
20
20
3
—
N
Pd
Ph
P
Ph
Ph
2
1
1
0
0
0
.0
.5
(+)-(R)
(+)-(R)
(+)-(R)
(ꢀ)-(S)
(ꢀ)-(S)
(ꢀ)-(S)
Ph
P
Ph
Ph
[PN]-1
(R)-1
.5
.25
.13
12
25
10
a
b
c
Pd, 0.01 equiv.
0 ꢁC.
Ph
P
2
Ph
N
N
Determined by HPLC analysis of the reaction mixture on a CHIRACEL-
ODH column 0.46 · 25 cm, eluent, 98:2 hexane/isopropanol.
P
Ph
Ph
Pd
Ph
Ph
[PP]-1
Scheme 4.
2
0 (+)
2
1
2
4.6, 22,8 and 18.2 ppm with a relative intensity of
:1.2:0.14. In the first instance, the singlets at d 24.6 and
2.8 were assigned to two [PN]-1 complexes, while the sin-
ee
0
a
glet at d 18.2 was attributed to the [PP]-1 complex. Such an
assignment was based on the observation that when more
ligand (1.0 equiv) was added, the intensity of the singlet
at d 18.2 ppm was enhanced (relative intensity, 1:1.2: 0.5,
2
4
0 (-)
b
3
1
respectively). On the basis of the P NMR analysis re-
ported by Reggelin and Helmchen for the palladium-catal-
ysed allylic alkylation using phosphinoaryldihydrooxazole
0 (-)
4
a
ligands,
we provisionally ascribed the signal at d
24.6 ppm to the endo–syn–syn [PN]nss-1 and the signal at
6
0 (-)
2
2.7 ppm to the diastereomeric exo–syn–syn [PN]xss-1
0
.5
1
.0
1.5
2.0
4
b,22
L/M
complex.
Figure 2. Ee value as a function of L/M molar ratio in the palladium-
catalysed malonylation of 1,3-diphenylpropenyl acetate using (R)-1 (plot
a) and (R)-2 (plot b) as a ligand.
31
The fact that the P signal of the presumed [PP]-1 complex
looks like a very sharp singlet, suggests that the two phos-
phorus atoms are equivalent and that nitrogen is not
involved in the coordination to the metal. Clearly, the
[PP]-1 complex preferentially gives (R)-6, while the [PN]-1
complex mixture gives the corresponding enantiomer (S)-
6 as the main alkylation product. Since the stoichiometric
L/M ratio did not seem to have an effect on the exo/endo
ratio, it substantially affected the [PN]/[PP] ratio, at first
glance, the change of ee with the change in L/M ratio
should depend on the [PN]/[PP] ratio. Unfortunately, due
to the presence of the more reactive [PP]-1 complex at
any L/M ratio, the extent of asymmetric induction ascribed
to [PN]-1 cannot be assessed. However, if we consider the
nucleophilic attack by malonate anion that occurs at the
allylic carbon anti to the phosphorus atom, the preferential
formation of the (S)-6 enantiomer could be due to a greater
reactivity of the exo–syn–syn– with respect to the diastereo-
meric endo–syn–syn–p-allyl complex. The slight preference
for the formation of (R)-6 from the nucleophilic attack
over [PP] complex is more difficult to rationalise.
seems to be a common trait of the P,N-type ligands having
a diphenylphosphino group bonded by an alkyl chain to a
2
stereogenic carbon adjacent to an sp nitrogen. As sug-
gested by Burgess, this trend can be explained by assuming
that the reaction of the allylpalladium chloride dimer with
1
,3-diphenylpropenyl acetate, in the presence of ligand (R)-
1
, generates two reactive species in equilibrium: a P,N-che-
lated allylpalladium complex [PN]-1 and a P,P-type allyl-
palladium complex [PP]-1 involving two molecules of the
ligand (Scheme 4), the relative amounts of [PN]-1 and
[
PP]-1 depend on the stoichiometric L/M molar ratio.
Both complexes catalyse the allylic alkylation, even though
the [PP]-1 complex seems to be much more effective. In
order to assess the composition of the mixture at different
L/M ratios, we prepared a 0.0032 mM solution of the
allylic complexes, by reacting diallylpalladium chloride
dimer with 1 equiv of the ligand (R)-1 (L/M = 0.5) in
CD Cl , under an argon atmosphere.
Since (R)-6 can be formed by nucleophilic attack either at
an endo–syn–syn ([PN]nss-1) or at an 31exo–anti–syn
([PN]xas-1) complex, the assignment of the P NMR sin-
glet at 24.6 to the former remain, at the moment, uncertain.
Indeed, it has been reported that the intervention of the
2
2
3
1
After 1,3-diphenylpropenyl acetate was added, the
P
NMR spectrum of the resulting mixture was quickly
recorded. The spectrum showed three sharp singlets at d

R. Ruzziconi et al. / Tetrahedron: Asymmetry 18 (2007) 1742–1749
1745
exo–anti–syn allylic arrangement may become important in
very overcrowded systems, as in this case.
Table 2. Enantiomeric excess in the malonylation of 1,3-diphenyl-2-
propen-1-yl acetate catalysed by [(R)-2]–Pd complex at variable L/M
molar ratios
4
c
23
a
b
c
To get further, more reliable information about the struc-
tural features of the P,N-type complexes involved in the
above process, we turned our attention to the homologous
ligand which has a diphenylphosphino group bonded to the
heterocyclic ring by an ethylenic bridge. We reasoned that
a greater flexibility of the side-chain would have entailed a
greater stability of the [PN] complexes, so as to allow a bor-
derline L/M ratio to be determined, below which in the
presence of [PP] complex in the reaction mixture can be
excluded. This would allow a more complete investigation
of the structural features of [PN] complexes. To this end, the
available (R)-(ꢀ)-2-hydroxymethyl-4-methyl[2]paracyclo[2]-
L/M ratio
Time (h) Conversion (%) ee (%) Configuration
2
1
.0
.5
24
24
24
24
24
24
100
100
100
60
25
10
2
17
39
58
57
54
(R)-(+)
(S)-(ꢀ)
(S)-(ꢀ)
(S)-(ꢀ)
(S)-(ꢀ)
(S)-(ꢀ)
1.0
0.5
0.25
0
.125
a
b
c
Pd, 0.01 equiv.
20 ꢁC.
Determined by HPLC analysis of the reaction mixture on a CHIRACEL-
ODH column 0.46 · 25 cm, eluent, 98:2 hexane/isopropanol.
1
7
(
5,8)quinolinophane 7 was treated with CBr /PPh in
cies is operating: [PP]-2 is the only species working at L/
M >2; while [PN]-2 complexes are running at L/M <0.5.
Of course, the asymmetric induction is affected by the
side-chain flexibility, as well as the significant distance of
the metal from the quinolinophane moiety.
4
3
diethyl ether at room temperature and the corresponding
bromomethyl derivative 8 was submitted to nucleophilic
substitution by lithium (diphenylphoshine)methylide
borane complex. The resulting 2-(quinolinophane)ethyldi-
phenylphosphine borane complex 9 was then treated with
DABCO and the expected ligand (R)-2 was recovered in
Thus, in the [PP]-2–Pd complex, the lengthening of the
side-chain moves the metal further away from the asym-
metric moiety than in the homologue [PP]-1–Pd complex;
this would account for the drop in enantioselectivity at
higher L/M ratios. Also in this case, the structural features
of the [PN] ligands were investigated by preparing a
.021 mM solution of the allylic complexes by reacting a
diallyl palladium chloride dimer with 1.0 equiv of the
ligand (R)-2 (L/M = 0.5) in CD Cl , under an argon atmo-
7
0% overall yield (Scheme 5).
CBr4/PPh3
Et2O, 20°C
N
0
N
Br
HO
(R)-7
(
R)-8
2
2
3
1
sphere. The P NMR spectrum, registered immediately
after the 1,3-diphenylpropenyl acetate was added, showed
two singlets at d 21.6 and 21.2 ppm with a relative intensity
LiCH2P(BH3)Ph2 THF,
78-0°C
-
3
1
1
:1.3. Analogously to the P NMR signals of the (R)-1-
derived p-allylpalladium complexes, the two singlets were
attributed to two [PN] bidentate complexes. As indicated
by plot b of Figure 2, at L/M ratios <0.5, the P,P-type
complex should be absent. This seems to be the case, as
no peaks attributable to this kind of complex were found
around 17.0 ppm. It is clear that at these L/M ratios, only
the [PN]-type complex operates as a catalytic species. It is
clearly seen that the major alkylated product (S)-6 should
be formed by the attack of the malonate anion at the car-
bon anti to the phosphorus atom of the most stable exo–
syn–syn [PN]–p-allylpalladium complex ([PN]xss-2), while
the minor (R)-6 enantiomer could be derived from an
attack either at an endo–syn–syn ([PN]nss-2) or at its diaste-
reomer exo–syn–anti ([PN]xas-2]) complex.
DABCO
C6H6, 40°C
N
N
Ph2P
R)-2
Ph2(H3B)P
(
(R)-9
Scheme 5.
Similar to ligand (R)-1, (R)-2 was tested in the same allylic
malonylation process. The trend of the ee values as a func-
tion of L/M stoichiometric ratio is reported in Table 2 and
plotted in Figure 2 (plot b).
A linear increase of the ee value in favour of the (S)-6 enan-
tiomer was observed when the L/M ratio decreased from 2
to 0.5. At an L/M value >2, a racemic mixture of alkylated
product was obtained, whereas at L/M <0.5, a practically
constant ee value of 56 ± 2% was recorded. This trend,
which was very similar to that already observed with ligand
With the absence of [PP]-2, an NOE-based investigation on
the structural features of the two [PN] complexes was now
1
possible. The H NMR spectrum of the complex mixture
showed two sets of three signals each: the first one, with
the signals located at d 6.28 (dd, J = 13.4 and 11.1 Hz),
5.56 (d, J = 13.4 Hz) and 4.41 (d, J = 11.1 Hz) ppm was
attributed to the allylic protons H-2, H-1 and H-3, respec-
(
R)-1, led us to conclude that, in this case, two catalytic
species in equilibrium are also operating in the 2.0–0.5 L/
tively, of the major complex [PN] -2 (Scheme 6). The sig-
x
M range, namely, a P,N-type p-allylpalladium complex
nals of the second set located at d 6.27 (dd, J = 13.4 and
10.3 Hz), 5.39 (d, J = 13.4 Hz) and 4.28 (d, J = 10.3 Hz),
[
PN]-2 and a P,P-type p-allylpalladium complex [PP]-2
which involves two ligand molecules. Within this range,
were attributed to the minor diastereomer [PN] -2. The
n
both species undergo nucleophilic attack, with [PP]-2 being
by far the most active one. Outside this range a single spe-
coupling constants and, most importantly the absence of
NOE effects between the allylic protons of each set, suggest
2
4

1746
R. Ruzziconi et al. / Tetrahedron: Asymmetry 18 (2007) 1742–1749
-CH(CO2Me)2
-CH(CO2Me)2
(R)-6
(S)-6
H2
H1
N
Ph
N
Pd
H3
Pd
Ph
Ph
P
P
H1
Ph2
Ph2
Ph
H3
H2
[
PN]nss-2
[PN]xss-2
Scheme 6.
a syn–syn configuration for both the diastereomeric
complexes (Scheme 6). Since they exhibit similar
thermodynamic stabilities, ([PN]xss-2/[PN]nss-2 = 1.3), the
substantial ee value (56 ± 2%) obtained in the alkylation
process has to be ascribed to kinetic rather than thermo-
dynamic factors. Therefore, the [PN]xss-2 complex leading
to the major product (S)-6 should be about five times more
reactive than the [PN]nss-2 one which gives the (R)-6
enantiomer.
Such a hypothesis was substantiated by Helmchen in thor-
ough structural and theoretical studies of palladium-catal-
ysed allylic alkylation using chiral oxazolinephosphines as
2
5
the ligand.
After another 3.0 equiv of ligand was added (L/M = 2), the
3
1
P NMR spectrum was recorded again. Besides the peaks
at d 21.6 and 21.2 ppm, a new very sharp singlet appeared
at d 16.6 ppm, the relative intensity being 1.2:1.5:1, respec-
3
1
tively. Analogous to the P NMR spectrum of the complex
mixture obtained with ligand (R)-1, the peak at 16.6 ppm
was attributed to the [PP]-2 complex. Interestingly, the
[PN]xss-2/[PN]nss-2 molar ratio (ꢁ1.3) remained un-
changed; this indicates that a fast equilibrium takes place
between the nearly isoenergetic exo and endo complexes.
Again, [PP]-2 complex is by far the most reactive species,
thus, at this L/M stoichiometric ratio the reaction is very
fast, and gives practically all racemic product.
In this particular case, the different reactivity could be
ascribed mostly to the substantial difference in the activa-
tion energy relative to the change from the g to g com-
3
2
plex along the reaction path. Indeed, in the reaction of
[
PN]xss-2 with malonate, the counter-clockwise rotation
of the allylic moiety around the Pd-allyl axis brings on a
remarkable steric relaxation, while in the reaction of
[
PN]nss-2, the analogous transformation implies a clock-
wise rotation of the allylic system, which would cause a
substantial increase in the steric interactions (Scheme 7).
3. Conclusion
In order to investigate the effects of planar chirality on the
asymmetric palladium-catalysed enantioselective allylic
alkylation, two homologous chiral P,N-bidentate ligands
Ph
Ph
P
N
(R)-1 and (R)-2 were developed derived from (R)-2,4-di-
Ph
Pd
Ph
very fast
methyl-[2]paracyclo[2](5,8)quinolinophane. Compound (R)-1
differs from (R)-2 only in the length of the carbon
side-chain binding the diphenylphospine group to the
quinolinophane moiety. Reactions of both ligands with
3
[
Pd(g -C H )Cl] , in the presence of 1,3-diphenylpropenyl
3
5
2
Ph
N
Ph
N
Ph
Ph
acetate, generate thermodynamic mixtures of exo–syn–syn
and endo–syn–syn p-allylpalladium complexes ([PN]xss
P
P
Pd Ph
Pd
and [PN]nss, respectively) and P,P-type p-allylpalladium
Ph
Nu
complexes [PP], the latter involving two molecules of the
ligand. The [PN]/[PP] ratio depends linearly on the stoichio-
metric ligand/metal molar ratio (L/M), while the [PN]x/
[PN]n molar ratio remains unchanged, indicating a fast
Ph
fast
Ph
Nu
slow
equilibrium between these two species. The low [PN]xss
/
[
PN]nss ratio (ꢁ1.2–1.3) indicates that the two complexes
are nearly isoenergetic. Due to the low stability of [PN]-1
complexes, the most effective [PP]-1 is present also at L/
M <0.125. This make impossible to assess the actual ee
value ascribable to [PN]-1. However, the value should
not be dissimilar to that of [PN]-2 complexes. If so, the
structural difference between (R)-1 and (R)-2 has little or
no influence on the relative reactivity of the corresponding
Ph
Ph
Ph
Ph
Ph
P
P
H
H
N
N
H
Ph
H
Nu
Pd
Pd
Ph
Ph
Nu
[
PN] complexes, nor on the mechanism of the allylic alkyl-
(
S)-5
(R)-5
minor
ation. The difference between the two ligands lies in a sub-
stantially higher stability of the [PN]-2 with respect to the
[PN]-1 complexes. This is mainly due to the greater flexibil-
major
Scheme 7.

R. Ruzziconi et al. / Tetrahedron: Asymmetry 18 (2007) 1742–1749
1747
ity of the six-member heterocyclic ring, involving phospho-
rus, palladium and nitrogen, formed with (R)-2, compared
with the homologous five member ring formed with (R)-1.
This would allow the angle (h) between the P–Pd–C-1 plane
and that of the quinolinophane moiety to increase in [PN]-
quinolinophane (0.5 g, 1.74 mmol) in diethyl ether (5 mL)
at 0 ꢁC under nitrogen. The cold bath was removed and
the red–brown mixture was allowed to react for 2 h. After
cooling at ꢀ75 ꢁC, chlorodiphenylphosphine (0.31 mL,
0.38 g, 1.74 mmol) was added. A quick decolouration was
observed after which, the mixture was allowed to react at
25 ꢁC for 1 h. Borane dimethyl ether complex (1 M in
THF, 1.74 mL, 1.74 mmol) was then added and the mix-
ture was allowed to react under stirring for 1 h before it
was poured into a mixture of ice and 5% aqueous HCl.
The organic phase was separated and the aqueous phase
was extracted with CH Cl (3 · 20 mL). The collected
2
, making the steric interactions less severe between the
phenyl group at C-1 and the ethylenic bridge of quinolino-
phane (Fig. 3).
Ph
Ph Ph
P
Ph
P
H
H
H
H
H
H
H
H
Ph
Ph
2
2
NPd
NPd
C1
organic phases were washed with water and dried over
Na SO . After solvent evaporation, chromatography of
θ2
Ph
C1
θ1
2
4
Ph
the crude product on silica gel (eluent, 8:2 petroleum
ether/CH Cl ) allowed 0.51 g (63%) of a amorphous solid
[PN]xss-2
[PN]xss-1
2
2
2
D
0
to be collected; mp 140–142 ꢁC; ½aꢂ ¼ þ6:7 (c 0.67,
Figure 3.
1
CH Cl ); H NMR d 8.13–8.08 (m, 2H), 7.80–7.75 (m,
2
2
2
H), 7.5 (m, 3H), 7.45–7.40 (m, 3H), 7.09 (s, 1H), 6.76–
4. Experimental
6.66 (four peaks, AB system, JAB = 7.2 Hz, 2H), 6.43–
1
13
6.36 (four doublets, split AB system, J = 7.9 Hz,
J = 1.7 Hz, 2H), 5.38 (dd, J = 7.8 and 1.7 Hz, 1H), 5.03
(d, J = 7.8 Hz, 1H), 4.15 (t, J = 14 Hz, 1H), 3.95 (dd,
J = 11 and 3.4 Hz, 1H), 3.83–3.72 (eight peaks, AB portion
of an ABX system, 2H), 3.10 (dd, J = 13 and 9.5 Hz, 1H),
AB
Unless specified, H and C NMR spectra were recorded
4
at 400 and 100 MHz, respectively, in CDCl solution using
tetramethylsilane as an internal standard. P NMR spec-
tra were recorded at 162 MHz in CDCl solution using
5% H PO as an external standard. IR spectra were
3
3
1
3
8
3 4
2.93 (dt, J = 14 and 9.2 Hz, 1H), 2.81 (td, J = 11 and
recorded in a FT-IR instrument in CHCl solution in the
3
ꢀ
1
3.4 Hz, 1H), 2.71 (td, J = 12 and 3.4 Hz, 1H), 2.64 (s,
4
2
000–400 cm
range. Optical activity was measured at
1
3
3
H), 2.56–2.46 (m, 2H); C NMR d 150.3 (d, J =
0 ꢁC in CHCl solution. The ee values were determined
by HPLC analysis of the (1,3-diphenylallyl)malonate enan-
tiomeric mixtures on a 0.46 · 25 cm Chiracel OD-H
column.
3
3.7 Hz), 142.9, 139.3 139.1, 137.9, 136.9, 133.8, 133.3 (d,
J = 9.4 Hz), 132.3, 132.1 (d, J = 1.9 Hz), 132.0, 131.5 (d,
J = 2.1 Hz), 131.0 (d, J = 2.1 Hz), 130.8, 130.7, 130.3,
1
1
3
29.6, 128.9, 128.8 (d, J = 1.6 Hz), 128.7 (d, J = 2.6 Hz),
28.5, 127.9, 125.4 (d, J = 2.7 Hz), 38.0, 36.2 (d, J =
4
.1. Reagents and solvents
31
2 Hz), 35.4, 34.3, 22.8; P NMR d 17.7 (m); IR (CHCl ),
3
ꢀ1
mmax 3021, 2928, 2855, 2388, 1589, 1437 cm ; Anal. Calcd
Chlorodiphenylphosphine and methyldiphenylphosphine
borane complexes were prepared from commercial chloro-
diphenylphosphine according to the procedures reported in
the literature. Racemic (E)-1,3-diphenylpropenyl acetate
± )-5 was prepared by condensation of acetophenone with
for C H BNP: C, 81.65; H, 6.85; N,2.89. Found: C,
3
3
33
81.43; H, 6.70; N, 2.97.
2
6
4.3. (R)-2-[(Diphenylphosphino)methyl]-4-methyl[2]para-
cyclo[2](5,8)quinolinophane (R)-1
(
benzaldehyde, followed by the reduction of the resulting
calcone with NaBH in methanol and, finally, acetylation
4
1
,4-Diazabicyclo[2.2.2]octane (DABCO) (80 mg, 0.71
of the alcohol with acetic anhydride in CH Cl in the pres-
2
2
mmol) was added to a solution of (diphenylphosph-
ino)methylquinolinophane borane complex (210 mg,
ence of N,N-dimethylaminopyridine (DMAP) according
to standard procedures. Bis-[(l-chloro)(1,3-diphenylallyl)-
palladium(II) was prepared following the procedure
0.43 mmol) in degassed benzene (2 mL) under argon (Cau-
tion! Use of gloves under an efficient hood is prescribed)
and the mixture was allowed to react at 50 ꢁC for 3 h.
The crude mixture was passed through a short column of
argon-flowed silica gel (eluent, degassed 9:1 petroleum
ether-diethyl ether mixture) in order to collect a white
2
7
reported by Pregosin. The starting material (R)-2,4-
dimethyl[2]paracyclo[2](5,9)quinolinophane and (R)-2-
hydroxymethyl-4-methyl[2]paracyclo[2](5,8)quinolinophane
(
R)-7 were available from a previous work.17 All the other
2
D
0
commercial products were of the highest purity grade and
used without further purification. Tetrahydrofuran and
diethyl ether were distilled from KOH in the presence of
CuCl and redistilled from sodium wires in the presence of
benzophenone. CH Cl was distilled from P O after 2 h
amorphous solid (180 mg, 82%): mp 68–70 ꢁC; ½aꢂ
¼
1
þ3:1 (c 4.4, CH Cl ); H NMR d 7.71 (td, J = 7.5 and
2
2
1
.3 Hz, 2H), 7.59 (td, J = 7.5 and 1.3 Hz, 2H), 7.44–7.38
(Sym. m, 6H), 7.00 (s, 1H), 6.83–6.72 (four peaks, AB sys-
2
2
2
5
tem, JAB = 7.2 Hz, 2H), 6.45 (tight AB system, JAB
7
7
=
=
reflux.
.1 Hz, 2H), 5.36–5.29 (four peaks, AB system, JAB
.7 Hz, 2H), 4.19 (br t, J = 8.6 Hz, 1H), 3.92 (d,
4.2. (R)-2-[(Diphenylphosphino)methyl]-4-methyl[2]para-
cyclo[2](5,8)quinolinophane borane complex (R)-4
J = 13 Hz, 1H), 3.83 (dd, J = 14 and 9.0 Hz, 1H), 3.73
(d, J = 13 Hz, 1H), 3.14 (dd, J = 13 and 9.5 Hz, 1H),
2
.98 (dt, J = 14 and 9.1 Hz, 1H), 2.90–2.80 (m, 3H), 2.64
1
3
Butyllithium (1.63 M in hexanes, 1.1 mL, 1.74 mmol) was
added to a solution of 2,4-dimethyl[2]paracyclo[2](5,8)-
(s, 3H), 2.54 (dt, J = 13 and 9.0 Hz, 1H); C NMR d
155.2 (d, J = 8.5 Hz), 150.2, 143.0, 139.6, 139.3, 139.1,

1748
R. Ruzziconi et al. / Tetrahedron: Asymmetry 18 (2007) 1742–1749
1
38.4 (d, J = 15 Hz), 137.7, 136.7, 133.3, 133.1, 132.8 (d,
d 156.9 (d, J = 14 Hz), 149.9, 143.4, 139.4, 139.2, 137.8,
137.0, 137.8, 137.0, 133.3, 132.5, 132.3, 132.2, (d,
J = 6.9 Hz), 132.1, 131.2, 131.2 (d, J = 2.1 Hz), 129.9,
129.4 (d, J = 20.9 Hz), 129.0, 128.9, 128.9, 128.2, 127.7,
J = 19 Hz), 132.3, 132.2 (d, J = 10 Hz), 130.9, 128.8,
1
3
28.7, 128.6, 128.5, 128.4, 128.3, 123.7 (d, J = 5.0 Hz),
3
1
8.7 (d, J = 15 Hz), 37.8, 35.3, 34.3, 31.5; P NMR d
12.8 (s); IR (CDCl ) m 3016 (s), 2972, 2930, 2855,
ꢀ
123.0, 37.6, 35.2, 34.6, 32.0, 31.3, 24.4 (d, J = 37 Hz),
3
max
ꢀ
1
31
1
590 (s), 1506, 1435, 1380 cm . Anal. Calcd for
22.6; P NMR d 16.0; IR (CHCl ) m
3023(vs), 2928,
3
max
ꢀ
1
C H NP: C, 84.05; H, 6.41; N, 2.97. Found: C, 83.81;
2382(s), 1591, 1437, 1110, 1062 cm . Anal. Calcd for
3
3
30
H, 6.29; N, 2.89.
C H BNP: C, 81.77; H, 7.06; N, 2.80. Found: C, 81.59;
3
4
35
H, 7.12; N, 2.91.
4
[
.4. (R)-2-(Bromomethyl)-4-methyl[2]paracyclo-
2](5,8)quinolinophane (R)-8
4.6. (R)-2-[2-(Diphenylphosphino)ethyl]-4-methyl[2]para-
cyclo[2](5,8)quinolinophane (R)-2
(
Hydroxymethyl)quinolinophane (R)-7 (1.0 g, 3.2 mmol)
was dissolved in anhydrous diethyl ether (10 mL), after
which CBr4 (1.1 g, 3.2 mmol) and triphenylphosphine
The same procedure used to prepare (R)-1 was used to pre-
pare (R)-2 starting from the quinolinophanephosphine bor-
ane complex (R)-9 (0.20 g, 0.40 mmol). A white amorphous
product was obtained and identified as quinolinophane-
(
0.86 g, 3.2 mmol) were added and the clear solution kept
at 25 ꢁC for 15 h. Fresh CBr (0.54 g, 1.6 mmol) and triphen-
4
20
ylphosphine (0.43 g, 1 6 mmol) were added and the mix-
ture allowed to react for 3 h. The solvent was evaporated
and the crude mixture filtered through a short column of
silica gel eluting with a 9:1 petroleum ether/diethyl ether
mixture. Flat white crystals were collected: mp, 158–
phosphine (R)-2 (0.18 g, 93%): mp 138–140 ꢁC; ½aꢂ
¼
D
1
þ17 (c 0.51, CHCl ); H NMR d 7.5 (m, 4H), 7.4 (m,
3
6H), 6.91 (s, 1H), 6.88–6.74 (four peaks, AB system,
JAB = 7.1 Hz, 2H), 6.47 (br s, 2H), 5.78 (d, J = 7.6 Hz,
1H), 5.48 (d, J = 7.6 Hz, 1H), 4.33 (m, 1H), 3.83 (dd,
J = 14 and 9.5 Hz, 1H), 3.15 (dd, J = 12 and 10 Hz, 1H),
3.08–2.89 (m, 6H), 2.71 (t, J = 16 Hz, 2H), 2.65 (s, 3H),
2
D
0
1
1
1
2
60 ꢁC; ½aꢂ ¼ ꢀ11:5 (c 0.5, CHCl ); H NMR d 7.22 (s,
3
H), 6.93–6.80 (four leaks, AB system, J = 7.2 Hz,
H), 6.48 (tight AB system, JAB = 8.4 Hz, 2H), 5.87 (d,
AB
1
3
2.56 (dt, J = 12 and 9.3 Hz, 1H); C NMR d 158.6 (d,
J = 12 Hz), 150.0, 143.1, 139.6, 139.3, 138.7, 138.8 (d,
J = 9 Hz), 138.7 (d, J = 19 Hz), 137.8, 136.9, 133.1, 132.9
(d, J = 18 Hz), 132.8 (d, J = 18 Hz), 132.4, 132.2, 131.1,
128.7, 128.6 (d, J = 7.0 Hz), 128.4, 128.3, 128.0, 123.0,
37.6, 35.3, 34.6, 34.5 (d, J = 21 Hz), 32.0, 27.5 (d,
J = 7.7 Hz, 1H), 5.15 (d, J = 7.7 Hz, 1H), 4.74–4.66 (four
peaks, AB system, JAB = 9.8 Hz, 2H), 4.32 (br t,
J = 10 Hz, 1H), 3.85 (dd, J = 14 and 9.1 Hz, 1H), 3.20–
2
1
1
1
3
.91 (m, 5H), 2.71 (s, 3H), 2.57 (dt, J = 13 and 9.0 Hz,
1
3
H); C NMR d 152.7, 149.7, 144.2, 139.8, 139.6, 137.7,
37.0, 134.3, 132.7, 132.5, 131.2, 129.4, 128.6, 128.4,
22.8, 37.7, 35.2, 35.1, 34.5, 32.0, 22.7; IR (CHCl ) m
3
1
J = 12 Hz), 22.7; P NMR d ꢀ15.56; IR (CHCl ) m
3
max
ꢀ
1
3018, 2928, 2855, 1591, 1436 cm . Anal. Calcd for
C H NP: C, 84.09; H, 6.64; N, 2.88. Found: C, 83.93;
3
max
ꢀ
1
016, 2972, 2930, 2855, 1590, 1506, 1435 cm . Anal. Calcd
3
4
32
for C H BrN: C, 68.86; H, 5.50; N, 3.82. Found: C,
H, 6.72; N, 2.95.
2
1
20
6
8.70; H, 5.42; N, 3.89.
4.7. General procedure for the palladium-catalysed allylic
4.5. (R)-2-[2-(Diphenylphosphino)ethyl]-4-methyl[2]para-
cyclo[2](5,8)quinolinophane borane complex (R)-9
alkylation of 1,3-diphenyl-2-propen-1-yl acetate at variable
L/M ratios
sec-Butyllithium (1.34 M in hexanes, 1.7 mL, 2.2 mmol)
was added to a solution of methyldiphenylphosphine bor-
ane complex (0.46 g, 2.2 mmol) in anhydrous THF at
Six test tubes, fitted with a para rubber septum, filled with
argon, after a few vacuum-argon cycles, were filled with
variable volumes (from 30 to 80 lL) of the suitable ligand
solution in degassed CH Cl (5.0 mL, 5.17 M) followed by
ꢀ
78 ꢁC under an argon atmosphere while stirring. The
2
2
mixture was allowed to react for 2 h before 2-(bromo-
methyl)-4-methyl[2]paracyclo[2](5,8)quinolinophane (0.80 g,
a degassed solution of diallylpalladium chloride dimmer
(30 lL, 0.033 M). After stirring for 5 min, 0.5 mL of a
freshly prepared solution of dimethyl malonate (0.75 g,
5.7 mmol), 1,3-diphenyl-2-propen-1-yl acetate (0.50 g,
2.0 mmol), potassium acetate (0.0016 g, 0.16 mmol), N,O-
bis(trimethylsilyl)acetamide (1.4 mL) in degassed CH Cl
2
.2 mmol) was added. The cold bath was removed and
after the temperature had risen to 25 ꢁC, the resulting yel-
low solution was poured into a mixture of ice and 5% aque-
ous HCl. The organic phase was separated and the aqueous
phase extracted with diethyl ether (3 · 20 mL), and the col-
lected organic phases were washed with water and dried
over Na SO . After solvent evaporation, chromatography
2
2
(5 mL) was added and the mixture allowed to react at
20 ꢁC for a suitable time. Water (1.0 mL) was added
through the septum and, after 2 min of stirring, the organic
phase was separated, dried over Na SO and the solvent
2
4
of the crude product on silica gel (eluent, 8:2 petroleum
ether/diethyl ether) allowed 0.81 g (75%) of an amorphous
white solid to be collected, which was identified as the
2
4
evaporated at reduced pressure. Preparative TLC on silica
gel (eluent petroleum ether/diethyl ether 8:2) allowed enan-
tiomeric mixtures of dimethyl (1,3-diphenyl-2-propen-1-
yl)malonate to be isolated. The enantiomeric excesses were
determined by HPLC analysis of the above mixtures on a
CHIRACEL OD-H 0.46 · 25 cm column using a hexane/
isopropanol 98:2 mixture as the eluent. Under such condi-
tions, the retention times were 16.5 min and 17.7 min for
(R)-(+)- and (S)-(ꢀ)-enantiomers, respectively.
20
phosphine borane complex: mp, 148–150 ꢁC; ½aꢂ ¼ þ37
D
1
(
(
c 0.48, CHCl ); H NMR d 7.85–7.76 (m, 4H), 7.52–7.44
3
m, 6H), 6.91 (s, 1H), 6.89–6.76 (four peaks, AB system,
JAB = 7.2 Hz, 2H), 6.48 (br s, 2H), 5.67–5.44 (four peaks,
AB system, JAB = 7.6 Hz, 2H), 4.34 (br t, J = 9.4 Hz,
1
2
H), 3.82 (dd, J = 13 and 9.4 Hz, 1H), 3.10–2.91 (m, 9H),
.64 (s, 3H), 2.55 (dt, J = 13 and 9.0 Hz, 1H); C NMR
1
3

R. Ruzziconi et al. / Tetrahedron: Asymmetry 18 (2007) 1742–1749
1749
Acknowledgements
Tsou, N. N.; Volante, R. P.; Reider, P. J. Am. Chem. Soc.
997, 119, 6207–6208; (c) Focken, T.; Raabe, G.; Bolm, C.
1
Tetrahedron: Asymmetry 2004, 15, 1693–1706; (d) Bolm, C.;
Focken, T.; Raabe, G. Tetrahedron: Asymmetry 2003, 14,
Thanks are due to MUR (Ministero dell’Universit a` e Ric-
erca) and the University of Perugia for financial support
1
733–1746.
(
PRIN 2004 Contract No. 2004033322). We also wish to
1
1
1. Bolm, C.; Beckmann, O.; Kuhn, T.; Palazzi, C.; Adam, W.;
express our sincere gratitude to Professor Thomas Rizzo
dean of the Institute of Chemical Sciences and Engineering
Rao, P. B.; Saha-Moller, C. R. Tetrahedron: Asymmetry
2
001, 12, 2441–2446.
´
(
(
ISIC) of the ‘Ecole Polytechnique F e´ d e´ rale de Lausanne’
2. (a) Whelligan, D. K.; Bolm, C. J. Org. Chem. 2006, 71, 4609–
4618; (b) Wu, X. W.; Yuan, K.; Sun, W.; Zhang, M. J.; Hou,
X. L. Tetrahedron: Asymmetry 2003, 14, 107–112; (c)
Bolm, C.; Wenz, K.; Raabe, G. J. Organomet. Chem. 2002,
Epfl), for the donation of useful laboratory equipments.
6
62, 23–33; (d) Wu, X. W.; Hou, X. L.; Dai, L. X.; Tao, J.;
Cao, B. X.; Sun, J. Tetrahedron: Asymmetry 2001, 12, 529–
32.
References
5
1
2
. (a) Trost, B. M.; Crawley, M. L. Chem. Rev. 2003, 103, 2921–
1
3. (a) Wu, X. W.; Zhang, T. Z.; Yuan, K.; Hou, X. L.
Tetrahedron: Asymmetry 2004, 15, 2357–2365; (b) Danilova,
T. I.; Rozenberg, V. I.; Starikova, Z. A.; Br a¨ se, S. Tetra-
hedron: Asymmetry 2004, 15, 223–229; (c) Br a¨ se, S.; Dahmen,
S.; H o¨ fener, S.; Lauterwasser, F.; Kreis, M.; Ziegert, R. E.
Synlett 2004, 2647–2669; (d) Danilova, T. I.; Rozenberg, V.
I.; Sergeeva, E. V.; Starikova, Z. A.; Br a¨ se, S. Tetrahedron:
Asymmetry 2003, 14, 2013–2019.
2
9
943; (b) Trost, B. M.; van Vranken, D. L. Chem. Rev. 1996,
6, 395–422; (c) Uenishi, J.; Hamada, M. Tetrahedron:
Asymmetry 2001, 12, 2999–3006.
. (a) Chelucci, G.; Orr u` , G.; Pinna, G. A. Tetrahedron 2003, 59,
471–9515; (b) Helmchen, G. J. Organomet. Chem. 1999, 576,
03–214; (c) Lautens, M. A.; Pfaltz, A. Allylic substitution
reactions. In Comprehensive Asymmetric Catalysis; Jacobsen,
E. N., Pfaltz, A., Yamanoto, H., Eds.; Springer: Heidelberg,
9
2
1
1
1
1
4. Song, C.; Ma, C.; Ma, Y.; Feng, W.; Ma, S.; Chai, Q.;
Andrus, M. B. Tetrahedron Lett. 2005, 46, 3241–3244.
5. Ricci, G.; Ruzziconi, R.; Giorgio, E. J. Org. Chem. 2005, 70,
1
999; Vol. 2, Chapter 24, (d) Jones, G.; Richards, C. J.
Tetrahedron: Asymmetry 2004, 15, 653–664; (e) Bunlaksan-
anusorn, T.; Luna, A. P.; Bonin, M.; Knochel, L.; Micouin,
P. Synlett 2003, 2240–2242; (f) Gilbertson, S. R.; Chang, C.
W. T. J. Org. Chem. 1998, 63, 8424–8431.
. (a) Cesarotti, E.; Demartin, F.; Grassi, M.; Prati, L. J. Chem.
Soc., Dalton Trans. 1991, 2073–2082; (b) Faller, J. W.; Chao,
K.-H.; Murray, H. H. Organometallics 1984, 3, 1231–1240.
. (a) Steinhagen, H.; Reggelin, M.; Helmchen, G. Angew.
Chem., Int. Ed. 1997, 36, 2108–2110; (b) Sprinz, J.; Kiefer,
M.; Helmchen, G.; Reggelin, M.; Huttner, G.; Walter, O.;
Zsolnai, L. Tetrahedron Lett. 1994, 35, 1523–1526; (c) Togni,
A.; Burckhardt, U.; Gramlich, V.; Pregosin, P. S.; Salzmann,
R. J. Am. Chem. Soc. 1996, 118, 1031–1037.
1
011–1018.
6. Worsdorfer, U.; V o¨ gtle, F.; Glorius, F.; Pfaltz, A. J. Prakt.
Chem. 1999, 341, 445–448.
7. (a) Ruzziconi, R.; Piermatti, O.; Ricci, G.; Vinci, D. Synlett
3
2
002, 747–750; (b) Ricci, G.; Ruzziconi, R. Tetrahedron:
Asymmetry 2005, 16, 1817–1827.
4
1
8. Kaiser, E. M.; Bartling, G. J.; Thomas, W. E.; Nichols, S. B.;
Nash, D. R. J. Org. Chem. 1973, 38, 71–75.
9. Togni, A. Tetrahedron: Asymmetry 1991, 2, 683–690.
0. Trost, B. M.; Murphy, D. J. Organometallics 1985, 4, 1143–
1
2
1
145.
1. Porte, A. M.; Reibenspies, J.; Burgess, K. J. Am. Chem. Soc.
998, 120, 9180–9187.
2
2
5
. (a) von Matt, P.; Loiseleur, O.; Koch, G.; Pfaltz, A.; Lefeber,
C.; Feucht, T.; Helmchen, G. Tetrahedron: Asymmetry 1994,
1
2. The subscripts xss, xas and nss refer to diastereomeric p-
allylpalladium complexes according to the meaning given by
Faller and Helmchen: (a) Faller, J. W.; Chao, K. H. J. Am.
Chem. Soc. 1983, 105, 3893–3898; (b) Kollmar, M.; Goldfuss,
B.; Reggelin, M.; Rominger, F.; Helmchen, G. Chem. Eur. J.
5
, 573–584; (b) von Matt, P.; Pfaltz, A. Angew. Chem., Int.
Ed. Engl. 1993, 32, 566–567; (c) von Matt, P.; Lloyd-Jones, G.
C.; Minidis, A. B. E.; Pfaltz, A.; Macko, L.; Neuburger, M.;
Zehnder, M.; Ruegger, H.; Pregosin, P. S. Helv. Chim. Acta
1
995, 78, 265–284.
2
001, 7, 4913–4927.
6
. (a) Sprinz, J.; Helmchen, G. Tetrahedron Lett. 1993, 34,
1
13
2
3. Because of the overlapping of the H and C signals of the p-
1
2
769–1772; (b) Helmchen, G.; Pfaltz, A. Acc. Chem. Res.
000, 33, 336–345.
allylic system with those of the aromatic protons overlooking
1
13
the quinoline moiety, H and C NMR spectra could not be
used to sort out the structural features of the different
palladium complexes present in the reaction mixture. Unfor-
tunately, we were unable to obtain any crystals that were
suitable for RX analysis.
7
8
. Dawson, G. J.; Frost, C. G.; Williams, J. M. J. Tetrahedron
Lett. 1993, 34, 3149–3150.
. (a) Zheng, W.-H.; Sun, N.; Hou, X.-L. Org. Lett. 2005, 7,
5
151–5154; (b) Barbaro, P.; Bianchini, C.; Giambastiani, G.;
Togni, A. Tetrahedron Lett. 2003, 44, 8279–8283; (c) Deng,
W. P.; You, S.-L.; Hou, X.-L.; Dai, L.-X.; Xia, Y.-H.; Yu,
W.; Sun, J. J. Am. Chem. Soc. 2001, 123, 6508–6519; (d)
Zhang, W.; Yoneda, Y.-i.; Kida, T.; Nakatsuji, Y.; Ikeda, I.
Tetrahedron: Asymmetry 1998, 9, 3371–3380; (e) Ahn, K. H.;
Cho, C.-W.; Park, J.; Lee, S. Tetrahedron: Asymmetry 1997,
2
2
4. By applying the pseudo-first order kinetic to the reaction of
each p-allylpalladium complex with malonate anion, an
approximate reactivity ratio k[PP]/k[PN] >120 can be calcu-
lated from the data reported in Tables 1 and 2.
5. Kollmar, M.; Steinhagen, H.; Janssen, J. P.; Goldfuss, B.;
Malinovskaya, S. A.; V a´ zquez, J.; Rominger, F.; Helmchen,
G. Chem. Eur. J. 2002, 8, 3103–3114.
6. Imamoto, T.; Oshiki, T.; Onozawa, T.; Kusumoto, T.; Sato,
K. J. Am. Chem. Soc. 1990, 112, 5244–5252.
7. Barbaro, P.; Pregosin, P. S.; Salzmann, R.; Albinati, A.;
Kunz, R. W. Organometallics 1995, 14, 5160–5170.
8
, 1179–1185; (f) Bolm, C.; Hermanns, N.; Kesselgruber, M.;
Hildebrand, J. P. J. Organomet. Chem. 2001, 624, 157–161.
. Gibson, S. E.; Knight, J. D. Org. Biomol. Chem. 2003, 1,
2
2
9
1
256–1269.
0. (a) Dominguez, B.; Zanotti-Gerosa, A.; Hems, W. Org. Lett.
004, 6, 1927–1930; (b) Pye, P. J.; Rossen, K.; Reamer, R. A.;
1
2