Synthesis, coordination properties and application of new N,N-ligands based on bornyl and binaphthylazepine chiral backbones in palladium-catalyzed allylic substitution reactions

Article abstract of DOI:10.1002/ejic.201100113

The synthesis of new imine-amine and diamine ligands, based on both the atropisomeric (S_a)- or (R_a)-1,1′-binaphthyl and (R)-bornyl backbones, and incorporating an ethylenediamino spacer, are reported. In addition, analogue ligands in

Full text of DOI:10.1002/ejic.201100113

FULL PAPER
DOI: 10.1002/ejic.201100113
Synthesis, Coordination Properties and Application of New N,N-Ligands Based
on Bornyl and Binaphthylazepine Chiral Backbones in Palladium-Catalyzed
Allylic Substitution Reactions
Giovanni Bottari*[a][‡] Angelo Meduri,[a][‡‡] Dario Drommi,[a] Giovanna Brancatelli,[a] and
Felice Faraone[a]
Keywords: Palladium / N ligands / Allylic compounds / Asymmetric catalysis / Enantioselectivity
The synthesis of new imine-amine and diamine ligands,
based on both the atropisomeric (Sa)- or (Ra)-1,1Ј-binaphthyl
and (R)-bornyl backbones, and incorporating an ethylenedi-
amino spacer, are reported. In addition, analogue ligands in
which one chiral arm is replaced by the achiral NMe2 group
were synthesized. These N,N-ligands when coordinated to a
1,3-diphenylpropene by dimethyl malonate. In one case, the
synergic effect of the chirality elements in the palladium cat-
alyst afforded the (S) substitution product with an enantio-
meric excess (ee) of Ͼ99%. Based on NMR studies of the
active species in solution, a reliable explanation for the origin
of the enantioselectivity of these palladium catalysts is also
palladium metal centre form highly enantioselective cata- provided.
lysts for the asymmetric allylic alkylation of rac-2-acetoxy-
process,[4] as well established by the privileged family of
Introduction
PHOX ligands;[5] on the other hand, steric effects prevail
over electronic effects in homo bidentate ligands. In con-
trast to P,P-ligands,[6] which are extremely useful in asym-
metric hydrogenation reactions, dinitrogen ligands are suc-
cessfully and frequently employed in allylic substitution re-
actions. In particular, C2-symmetric chelating ligands[7]
have been proven to possess the requirements for inducing
high enantioselectivity since they reduce the number of pos-
sible transition states that compete in the enantiomeric en-
richment process.
Stereoselective formation of C–C bonds is a major chal-
lenge in synthetic chemistry and transition metal complexes
may serve as a powerful tool to control the selectivity of
such processes.[1] In this field, allylic substitution reactions
have played a dominant role over the years thanks to their
mild experimental conditions and low metal-catalyst load-
ing requirements; moreover, depending on the nature of the
chiral inducer, the substitution product may be obtained
with excellent selectivity.[2]
During the past decades a plethora of chiral ligands has
been investigated in asymmetric allylic substitution reac-
tions although only some of them have been recognized as
“privileged ligands”, according to the definition given by
Jacobsen.[3] In bidentate ligands containing two different
donor atoms the trans effect exerted by the strong σ-donor
atom plays a determining role in the enantiodiscrimination
In previous work[8] we have investigated the use of C1-
symmetric dinitrogen chiral ligands featuring a binaph-
thylazepine moiety, and which differed in the scaffold rigid-
ity of the achiral portion, which were a 2-picolyl or 8-quin-
olinyl group. In this study we found that the formation of
a flexible five-membered palladacycle favours the activity
and enantioselectivity of the catalyst, with ee values up to
82% in the allylic alkylation of rac-1-acetoxy-1,3-di-
phenylpropene. The same ligands were applied in the ruthe-
nium-catalyzed allylic alkylation and etherification of cin-
namyl derivatives, which are prototypes of unsymmetrical
allylic substrates, and the synthesized precalysts led to high
regioselectivity towards the branched product and moderate
ee values.[9]
[a] Dipartimento di Chimica Inorganica, Chimica Analitica e
Chimica-Fisica dell’Università di Messina,
Salita Sperone 31, Vill. S. Agata, 98166 Messina, Italy
[‡] Current address: Instituto de Investigaciones Químicas,
Consejo Superior de Investigaciones Científicas and
Universidad de Sevilla,
Avenida Américo Vespucio no. 49, Isla de la Cartuja,
41092 Sevilla, Spain
Following our studies of palladium-catalyzed allylic alk-
ylation reactions with symmetrical substrates, we have de-
signed new bidentate C1-symmetric ligands exploiting the
benefits of several structural elements: (a) a binaphth-
ylazepine group along with either a bornyl fragment as
E-mail: giovanni.bottari@iiq.csic.es
[‡‡] Current address: Dipartimento di Scienze Chimiche,
Università di Trieste,
Via Licio Giorgieri 1, 34127 Trieste, Italy
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100113.
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N,N-Ligands Based on Chiral Backbones
further source of chirality[10] or a simple NMe2 group; (b) expected. However, only one diastereomer was detected by
the flexibility of the catalyst metallacycle is ensured by the 1H NMR and the absolute configuration of the stereogenic
presence of an ethylenic spacer between the donor atoms, centre (R)[10f] was determined by means of multidimen-
with the consequential formation of a stable five-membered sional NMR techniques.
ring; (c) the electronic differentiation of the donor atoms
was ensured by use of two ligand typologies, namely, di-
amines and mixed amine-imine ligands. Furthermore, this
study also involved the synthesis of analogue ligands featur-
ing only a bornyl fragment as the chiral source and an
NMe2 group, as well as the investigation of the coordina-
tion chemistry of selected palladium complexes, and the
catalytic application of these complexes in palladium-cata-
lyzed allylic substitution reactions.
In order to evaluate the different asymmetry induction
effects of the chiral binaphthylazepine and bornyl moieties
in catalytic experiments, N,N ligands (Sa)-4, (R,R)-5 and
(R,R,R)-6 in which one of the two chiral arms present in
the diastereomeric ligand pairs 2 and 3 were replaced by a
simple achiral NMe2 group, were synthesized according to
the Scheme 2. Ligand (Sa)-4 was reported for the first time
by Cram and co-workers,[12] who used it as chiral controller
in the asymmetric addition of alkyllithium reagents to alde-
hydes. Some years later this ligand was used by Rosini and
co-workers[13] in the enantioselective dihydroxylation of ole-
fins; to the best of our knowledge no data related to its
use in palladium-catalyzed allylic substitution are present in
literature. Ligand (R,R)-5 was obtained by a condensation
reaction between (R)-(+)-camphor and N,N-dimethylethyl-
enediamine. The reduction of the C=N double bond in
(R,R)-5 gave (R,R,R)-6 as the major isomer, while traces of
the corresponding diastereomer with S configuration at the
new stereogenic carbon atom were revealed by GC–MS. Al-
though the complete removal of the minor diastereomer
was not successful, it is reasonable to neglect its effect in
subsequent studies. All ligands were fully characterized by
NMR spectroscopy and elemental analysis; they are stable
in air and even the amine-imine ligands are resistant to hy-
drolysis.
Results and Discussion
Synthesis of Ligands
The synthesis of ligands featuring the binaphthylazepine
moiety started from (Ra)- or (Sa)-1,1Ј-binaphthol, which
can be converted easily into the compounds (Ra)-1 or (Sa)-
1 after four synthetic steps, according to the literature.[7f,11]
The reaction between the NH2 group of the enantiomeric
diamines (Ra)-1 and (Sa)-1 and the (R)-(+)-camphor car-
bonyl group, in refluxing toluene in the presence of catalytic
amounts of p-toluenesulfonic acid afforded the desired dia-
stereomeric amine-imine ligands (Ra,R,R)-2 and (Sa,R,R)-2,
as depicted in the Scheme 1, in good yields. The subsequent
reduction of the C=N bond within (Ra,R,R)-2 and
(Sa,R,R)-2 with sodium borohydride and nickel chloride
From a general point of view, the two arms of the ligands
readily gave the new diamine ligands (Ra,R,R,R)-3 and produce sterically differentiated environments, especially in
(Sa,R,R,R)-3.[10c]
ligands (Sa)-4, (R,R)-5 and (R,R,R)-6 that contain a small
It is clear that the reduction involves the formation of a NMe2 fragment and a bulkier binaphthylazepine or bornyl
stereogenic carbon atom and two possible diastereomers are chiral arm.
Scheme 1. Reagents and conditions: (i) See ref.[7f]; (ii) (R)-(+)-camphor, PTSA (p-toluenesulfonic acid), toluene, Dean–Stark conditions;
(iii) NaBH4, NiCl2, MeOH, –40 °C to room temp.
Scheme 2. Reagents and conditions: (i) (Sa)-2,2Ј-dibromomethyl-1,1Ј-binaphthalene, toluene, 65 °C; (ii) (R)-camphor, PTSA, toluene,
Dean–Stark conditions; (iii) NaBH4, NiCl2, MeOH, –40 °C to room temp.
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G. Bottari, A. Meduri, D. Drommi, G. Brancatelli, F. Faraone
FULL PAPER
Catalytic Experiments
Interestingly, bornyl and binaphthylazepine chiral arms
in ligands (Sa,R,R,R)-3 and (Ra,R,R,R)-3 play a synergic
role in inducing high enantiomeric excesses, and only a
small mismatching effect can be ascribed to the catalysts
containing these ligands, which differ in the absolute config-
uration of the atropisomeric binaphthyl moiety. It is also
noteworthy that the structurally simple and easily accessible
ligand (Sa)-4 is able to induce 95% ee under standard allylic
alkylation conditions. In Figure 1 our best results are com-
pared to that obtained by Moberg and co-workers with a
C2-symmetric binaphthylazepine-based dinitrogen ligand.
The synthesized chiral N,N-ligands were evaluated in the
allylic alkylation reaction of rac-1-acetoxy-1,3-diphenyl-
propene with dimethyl malonate under Trost conditions
(Scheme 3). The active species was formed in situ by mixing
[Pd(η3-allyl)Cl]2 and the N,N-ligand in an 1:2.2 ratio in an
appropriate solvent, and the results from these reactions are
reported in Table 1.
Scheme 3. Allylic alkylation reaction of rac-1-acetoxy-1,3-di-
phenylpropene catalyzed by Pd/N,N-catalysts.
Table 1. Details of the palladium-catalyzed allylic alkylation reac-
tions of rac-1-acetoxy-1,3-diphenylpropene.[a]
Entry
N,N-ligand
Yield [%][b]
ee [%][c]
1
2
3
(Ra,R,R)-2
(Sa,R,R)-2
(Ra,R,R,R)-3
(Ra,R,R,R)-3
(Sa,R,R,R)-3
(Sa,R,R,R)-3
(Sa)-4
12
18
84
Ͼ99
16
38
Ͼ99
15
26
68 (S)
76 (S)
98 (S)
Ͼ99 (S)
92 (S)
96 (S)
95 (S)
66 (S)
55 (S)
Figure 1. Comparison of ee values obtained in this work with that
reported by Moberg using a C2-symmetric ligand.[7f]
4[d,e]
5
6[d]
7[e]
8
The ligands in Figure 1 contain binaphthylazepine
groups and form flexible five-membered palladacycles,
which shows that the symmetry of the ligand is not a factor
that dramatically influences the selectivity of the catalytic
process. However, the presence of the binaphthylazepine
moieties is beneficial in the enantiocontrol process. Finally,
it appears that when in presence of the mixed ligand pairs
2 and 3 the absolute configuration of the substitution prod-
uct is determined by the chirality of the bornyl moiety,
which always assumes the descriptors (R,R) or (R,R,R),
while compounds containing a binaphthylazepine group af-
forded the S product regardless of the absolute configura-
tion of this group, which can be either Ra or Sa.
(R,R)-5
9
(R,R,R)-6
[a] Experimental conditions: [Pd(η3-allyl)Cl]2/N,N-ligand/substrate/
dimethyl malonate/BSA [bis(trimethylsilyl)acetamide]
1:2.2:100:300:300, in CH2Cl2 (if not stated otherwise), a pinch of
KOAc, room temp., 16 h. [b] Determined by 1H NMR spec-
troscopy. [c] Determined by chiral HPLC (see experimental section
for details). [d] The catalytic run was carried out in toluene instead
of CH2Cl2. [e] Complete conversion was observed after 4 h.
=
The catalytic systems showed poor to excellent activity
in the catalytic tests, with the Pd/(Ra,R,R,R)-3 and Pd/(Sa)-
4 complexes being the most efficient catalysts in terms of
both product yield and enantioselectivity; in fact, the reac-
tion involving Pd/(Ra,R,R,R)-3 was complete in about 4 h
(as monitored by GC–MS) with ee values of Ͼ99%
(Table 1, entry 4). The solvent does have an influence on
the catalytic results and changing from dichloromethane to
the less polar toluene gives a moderate increase in the con-
version and a slight improvement of asymmetric induction
when ligands (Ra,R,R,R)-3 and (Sa,R,R,R)-3 were used, as
clearly highlighted by comparison between entries 3 and 4,
and entries 5 and 6, in Table 1. It was not possible to verify
if this trend applies to ligand (Sa)-4 due to the precipitation
of the active species Pd/(Sa)-4 when formed in toluene. The
palladium catalysts containing mixed amine-imine ligands,
(Ra,R,R)-2, (Sa,R,R)-2 and (R,R)-5, gave only low conver-
sion levels, although the enantioselectivity of (Sa,R,R)-2
was good (up to 76%, entry 2, Table 1); it is likely that the
catalytic activity of these complexes is suppressed by the
rigidity of the iminic moiety coordination.
Coordination Chemistry and Solution Studies
The reactions between [PdCl2(PhCN)2] and some se-
lected N,N-ligands were investigated in order to evaluate the
coordination modes and spatial arrangement of the coordi-
nated ligands. The reactions were carried out with a Pd/
N,N-ligand ratio of 1:1.2, in THF, at room temperature, and
the mixture was left to react for 2 h, in accordance with the
equation in Scheme 4.
Scheme 4. Synthesis of [PdCl2(k2-N,N-ligand)] complexes.
All the synthesized complexes were fully characterized by
NMR and elemental analysis. Although we did not obtain
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N,N-Ligands Based on Chiral Backbones
suitable crystals for X-ray diffraction analysis, NMR analy- species, and with their reactivity under equilibrium condi-
sis revealed a bidentate coordination mode for the N,N-li- tions. In order to explain the high enantioselectivity of this
1
gands with palladium. In the H NMR spectrum of com- complex, a complete structural assignment of the allylic
pound 7 [PdCl2{(Ra,R,R,R)-3}] a shift of the proton signals species would be advantageous. Unfortunately, due the
of the N,N-ligand relative to the signals of the uncoordi- complexity of the NMR spectra of complex 11, it was nec-
nated ligand was observed; for instance, the AB system at- essary for us to limit the study to the relationship between
tributed to the azepinic CH2 groups of the free ligand turns the palladium-allyl species and the origin of enantio-
into four doublets in the spectrum of 7, and one methylenic selectivity of the “model” complex 12. This complex is also
group of the coordinated ligand experiences the proximity present in solution as a mixture of two syn-syn isomers,
of the palladium centre and gives two well resolved doublets which do not undergo exchange processes, in a ratio of ca.
at δ = 4.80 and 2.90 ppm in the spectrum of 7. The ethylenic 96:4. On the basis of the NOE crosspeaks between the al-
spacer protons show signals between δ = 4.37 and lylic moiety and the ligand (Figure 2, a), an endo-syn-syn
2.25 ppm, while the NH signal in the spectrum of 7 is conformation was assigned to the major isomer, and as this
shifted significantly downfield with respect to the same sig- is the only species contributing to the enantioenrichment,
nal in the spectrum of the free ligand (broad singlet at δ = since no exchange processes are observed, the S configura-
6.25 ppm compared to 1.72 ppm in the free ligand spec- tion of the product can be explained by the nucleophilic
trum). The coordination of the NMe2 containing ligands, attack at the allylic carbon trans to the binaphthylazepine
(Sa)-4, (R,R)-5 and (R,R,R)-6, to palladium was witnessed group affording the corresponding (η2-olefinic)palladium
by the appearance of two different singlets (in the 2–3 ppm species (Figure 2, b); in this case, the olefin rotation should
range) in the spectra of their coordination complexes that not be affected by possible interactions with the binaphth-
arise due to the diastereotopicity of the methyl groups after ylazepine group.
the chelation process, which is in contrast to the unique
singlet in 1H NMR spectra of the corresponding free li-
gands. Also, the C=N carbon atom of (R,R,R)-6 is strongly
shifted downfield in the 13C NMR spectrum of the coordi-
nated ligand (δ = 196.9 ppm compared to 182.4 ppm in
spectrum of the free ligand), confirming that the iminic ni-
trogen atom is bonded to the metal centre.
As shown in Scheme 5, we have also prepared the palla-
dium allyl complexes containing ligands (Sa)-4 and
(Ra,R,R,R)-3, which showed the best catalytic performance
out of all the complexes reported herein.
Figure 2. (a) Allylic conformers of complex [Pd{(Sa)-4}(η3-
PhCHHCCHPh)]OTf in CDCl3 solution, also shown are some se-
lected NOE contacts within the major isomer (the OTf anion is
omitted for clarity). (b) Formation of the (S) substitution product
from the nucleophilic attack at the C-Ha carbon atom of the endo-
syn-syn isomer (the OTf anion is omitted for clarity).
Indeed, the enantiomeric ratio of the product (97.5:2.5,
as determined by chiral HPLC; see Table 1, entry 7) is con-
Scheme 5. Synthesis of palladium allyl complexes.
NMR analysis of the allylic complexes {[Pd(Ra,R,R,R)- sistent with the observed ratio of the palladium-allyl con-
1
3][(η3-PhCHCHCHPh)]OTf} (11) and {[Pd{(Sa)-4}(η3- formational isomers in solution, 96:4, as determined by H
PhCHCHCHPh)]OTf} (12) gave useful information about NMR integration of allylic proton signals. The small differ-
the catalytic active species formed in solution. For complex ence in these ratios is attributable to the measurement
1
11, H NMR spectra revealed the presence of two confor- method and the experimental conditions of the catalytic test
mational allylic isomers in a 75:25 ratio; in both species, 2D with respect to those of the complex analysis, particularly
NOESY spectroscopy indicates a syn-syn arrangement for the differences in the counteranion and solvent. The basic-
the phenyl substituents on the allylic fragment with respect ity properties of both nitrogen atoms are very similar as
to the central allylic hydrogen, and both isomers are in reflected in the close chemical shift values of the C1 and
equilibrium. In Figure 2 (a) the two isomers are illustrated, C3 allylic carbon atoms in the 13C NMR spectrum of com-
and can be called exo-syn-syn and anti-syn-syn, in accord- plex 12 (75.4 and 78.9 ppm, respectively), this is due to a
ance to the nomenclature proposed by Widhalm and co- comparable trans influence of the donor atoms. On the
workers.[14] In previous work,[8] we correlated the observed other hand, it is reasonable to assume that steric effects
enantiomeric excess with the concentration of the allylic must play a role in determining the high enantioselectivity
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G. Bottari, A. Meduri, D. Drommi, G. Brancatelli, F. Faraone
FULL PAPER
of this complex, with the bulky binaphthylazepine group solution of two allylic isomers. Furthermore, these com-
exerting an excellent degree of regio- and, more specifically, plexes gave excellent ee values when used as catalysts in al-
enantio-control.
lylic alkylation reactions, and in one case (Table 1, entry 4),
An analogous regioselectivity in the nucleophilic attack slightly better catalytic results were obtained than the best
of complex 11 is possible, since the trans-effect of the NH results reported in the literature for related dinitrogen li-
nitrogen atom is slightly lower than that of the tertiary ni- gands.[7f] In one case, the characterization of the isomers
trogen atom, and an endo-syn-syn conformation is expected and their ratio in solution, along with the identification of
for the more reactive allylic species in order to explain the exchange processes in solution, were found to be correlated
S configuration of the product. Apart from these weak strongly with the observed enantiomeric excess when the
electronic effects, the low number of conformational complex was used to catalyze allylic alkylation reactions.
isomers, along with the cooperative steric effects of the Finally, this work highlights the capability of stable and eas-
binaphthylazepine and bornyl groups in the ligand ily available phosphane-free ligands to form highly selective
(Ra,R,R,R)-3 are definitively crucial in determining the very catalysts for allylic substitution reactions, which is in con-
high enantiomeric excess of products arising from reactions trast to the extensive literature related to the use of chiral
involving this ligand.
P,N- or P,P-ligands in such reactions.[15]
Experimental Section
Conclusions
General Methods: All manipulations involving air-sensitive chemi-
cals were performed in argon or nitrogen atmospheres. Solvents
were dried and distilled prior to use according to standard pro-
cedures. (Sa)-(+)-2,2Ј-dibromomethyl-1,1Ј-binaphthalene and (Sa)-
In conclusion, we have synthesized a new family of dini-
trogen ligands containing both a binaphthylazepine and a
bornyl group, which are derived from (R)-(+)-camphor and
have a flexible ethylenic spacer between the nitrogen donor
atoms. The evaluation of the individual effects of the dif-
ferent ligand components on the product chirality was
made possible by comparison of the catalytic performance
of these ligands with those of ligands containing only one
chiral arm, either a binaphthylazepine or a bornyl frag-
ment, with the second arm being replaced with an achiral
NMe2 group. The ligands featuring sp2 and sp3 nitrogen
atoms, which can rely on a strong trans effect of the iminic
nitrogen to create an electronic differentiation between the
two allylic carbon atoms, produced lower ee values than
diamine ligands, whose donor atoms possess a nearly equal
basicity, when employed in allylic alkylation reactions. On
the other hand, it seems that steric effects play a dominant
role in the catalytic process, especially when the coordinated
ligand contains a binaphthylazepine moiety that is remark-
ably bulky. As a result, although a synergic effect between
the two chiral arms was observed in the diastereomer
(Ra,R,R,R)-3, which afforded a Ͼ99% ee in the allylic alk-
ylation of rac-1,3-diphenylacetoxy-1-propene, it seems that
the binaphthylazepine backbone possesses an intrinsic
capability to exhibit enantiocontrol in this reaction since a
95% ee was reached when the palladium complex contain-
ing ligand (Sa)-4 was used, even though the bornyl group
was replaced with an achiral fragment in this ligand. In
2-(3H-dinaphtho[2,1-c:1Ј,2Ј-e]azepin-4(5H)-yl)ethanamine
were
synthesized according to a literature procedure.[7f] All other rea-
gents were purchased from Sigma–Aldrich and Strem and used as
supplied. For column chromatography, silica gel 60 (220Ϯ440
mesh) purchased from Fluka, and basic alumina (70–290 mesh)
from Aldrich, were used. 1D and 2D NMR experiments were car-
ried out with a 500 MHz Varian or 300 MHz Bruker spectrometers.
Elemental analyses were performed by Redox s.n.c., Cologno Mon-
zese, Milano. Enantiomeric excesses were determined by chiral
HPLC with a Chiralcel OD-column, and the absolute configura-
tion of the materials were determined by comparison with reported
data.
Synthesis of Ligands
(E)-2-{(Ra)-3H-Dinaphtho[2,1-c:1Ј,2Ј-e]azepin-4(5H)-yl}-N-
{(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene}ethanamine
[(Ra,R,R)-2] and (E)-2-{(Sa)-3H-Dinaphtho[2,1-c:1Ј,2Ј-e]azepin-
4(5H)-yl}-N-{(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl-
idene}ethanamine [(Sa,R,R)-2]: In a 10 mL one-neck flask (R)- or
(S)-1 (0.726 g, 2.15 mmol), (R)-(+)-camphor (0.345 g, 2.27 mmol)
and p-toluenesulfonic acid (22 mg, 0.11 mmol) were dissolved in
2 mL of anhydrous toluene. The reaction mixture was vigorously
stirred overnight, under reflux conditions, in a Dean–Stark appara-
tus. The progress of the reaction was monitored by TLC, and after
no trace of the starting amine was detected, the solution was cooled
down and the solvent evaporated under reduced pressure to give
the corresponding crude imine.
principle, the functionalization of the aminic group in the (Ra,R,R)-2: This material was purified by chromatography (basic
alumina, toluene:ethyl acetate, 15:1). Pale yellow solid; yield 750
(74%). H NMR (300 MHz, CDCl3): δ = 0.76 (s, 3 H, CH3), 0.93
precursor 1 with different chiral derivatives, or achiral frag-
ments, with different steric demands, could be exploited to
improve the catalytic performance of palladium complexes
of this class of ligand, and to extend their applicability in
the allylic alkylation of a broad range of substrates. The
potential of this new class of ligands as possible compo-
nents in catalysts resides in the possibility of modulating
their structures inexpensively.
1
(s, 3 H, CH3), 1.02 (s, 3 H, CH3), 1.20 (m, 1 H), 1.38 (m, 1 H),
1.69 (m, 1 H), 1.78–2.01 (m, 3 H), 2.36–2.50 (m, 1 H), 2.65 (m, 1
H), 2.94 (m, 1 H), 3.38–3.64 (m, 2 H), 3.79 and 3.24 (AB, J =
12 Hz, 4 H, 2ϫ ArCH2N), 7.27 (m, 2 H), 7.47 (m, 4 H), 7.62 (d,
J = 8 Hz, 2 H), 7.95 (m, 4 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 11.5 (CH3), 19.0 (CH3), 19.5 (CH3), 27.4 (CH2), 32.1 (CH2),
35.8 (CH2), 43.8 (CH), 47.0 (C), 51.8 (CH2), 53.7 (C), 55.6 (CH2),
55.7 (CH2), 125.3 (CH Ar), 125.6 (CH Ar), 127.4 (CH Ar), 127.9
The NMR study of allyl palladium complexes containing
ligands (Ra,R,R,R)-3 and (Sa)-4 revealed the presence in (CH Ar), 128.2 (CH Ar), 131.3 (C Ar), 133.1 (C Ar), 133. 6 (C
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N,N-Ligands Based on Chiral Backbones
Ar), 134.9 (C Ar), 182.9 (C=N) ppm. C34H36N2 (472.67): calcd. C was washed with brine, dried (MgSO4) and concentrated under vac-
86.40, H 7.68, N 5.93; found C 86.58, H 7.52, N 5.90.
uum to give the crude amine.
(1R,2R,4R)-N-[2-{(Ra)-3H-Dinaphtho[2,1-c:1Ј,2Ј-e]azepin-4(5H)-
yl}ethyl]-1,7,7-trimethylbicyclo[2.2.1]heptan-2-amine [(Ra,R,R,R)-3]:
This compound was purified by chromatography (silica, pentane:e-
(Sa,R,R)-2: This material was purified by chromatography (basic
alumina, toluene:ethyl acetate, 15:1). Pale yellow solid; yield
640 mg (63 %). 1H NMR (300 MHz, CDCl3): δ = 0.77 (s, 3 H,
CH3), 0.93 (s, 3 H, CH3), 1.00 (s, 3 H, CH3), 1.15–1.24 (m, 1 H),
1.32–1.42 (m, 1 H), 1.61–1.94 (m, 3 H), 2.33–2.43 (m, 1 H), 2.62
(dt, J = 12 and 7 Hz, 1 H), 2.92 (dt, J = 12 and 7 Hz, 1 H), 3.50
(t, J = 7 Hz, 2 H, C=NCH2), 3.77 and 3.24 (AB, J = 12 Hz, 4 H,
2ϫ ArCH2N), 7.23–7.39 (m, 2 H), 7.42–7.50 (m, 4 H), 7.60 (d, J
= 9 Hz, 2 H), 7.95 (m, 4 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 11.5 (CH3), 19.0 (CH3), 19.6 (CH3), 27.5 (CH2), 32.1 (CH2), 35.8
(CH2), 43.8 (CH), 47.1 (C), 51.7 (CH2), 53.6 (C), 55.5 (CH2), 55.6
(CH2), 125.3 (CH Ar), 125.7 (CH Ar), 127.4 (CH Ar), 127.9 (CH
Ar), 128.3 (CH Ar), 131.3 (C Ar), 133.1 (C Ar), 133.6 (C Ar), 135.0
(C Ar), 175.7 (C=N) ppm. C34H36N2 (472.67): calcd. C 86.48, H
7.58, N 5.93; found C 86.55, H 7.51, N 5.94.
1
thyl acetate, 3:1, 2% methanol). White solid; yield 92%. H NMR
(500 MHz, CDCl3): δ = 0.82 (s, 3 H, CH3), 0.90 (s, 3 H, CH3),
1.01–1.11 (m, 4 H), 1.48–1.74 (m, 6 H), 2.44–2.57 (m, 3 H), 2.67–
2.81 (m, 3 H), 3.70 and 3.18 (AB, J = 12 Hz, 4 H, 2ϫ ArCH2N),
7.23–7.28 (m, 2 H), 7.42–7.49 (m, 4 H), 7.54 (d, J = 8 Hz, 2 H),
7.94 (d, J = 8 Hz, 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
12.3 (CH3), 20.5 (CH3), 20.6 (CH3), 27.4 (CH2), 37.0 (CH2), 39.1
(CH2), 45.3 (CH), 46.3 (CH2), 46.7 (CH2), 47.1 (CH2), 48.5 (CH2),
55.1 (CH2), 55.5 (CH2), 67.2 (CH), 125.5 (CH Ar), 125.7 (CH Ar),
127.5 (CH Ar), 127.8 (CH Ar), 128.2 (CH Ar), 128.3 (CH Ar),
131.4 (C Ar), 133.1 (C Ar), 133.8 (C Ar), 135.0 (C Ar) ppm.
C34H38N2 (474.69): calcd. C 86.03, H 8.07, N 5.90; found C 86.21,
H 7.83, N 5.96.
(Sa)-2-{3H-Dinaphtho[2,1-c:1Ј,2Ј-e]azepin-4(5H)-yl}-N,N-dimeth-
ylethanamine [(Sa)-4]: In a Schlenk flask under argon, (Sa)-2,2Ј-
dibromomethyl-1,1Ј-binaphthalene (440 mg, 1 mmol) and N,N-di-
methylethylenediamine (2 mL) were dissolved in toluene (5 mL)
and the solution was left stirring overnight at 60 °C. Water (25 mL)
and diethyl ether (25 mL) were then added and the organic phase
collected, dried with MgSO4, filtered and concentrated under re-
duced pressure. The product was used without further purification;
yield 340 mg (93%). 1H NMR (300 MHz, CDCl3): δ = 2.29 (s, 6
H, 2ϫ NCH3), 2.54 (m, 3 H), 2.74 (m, 1 H), 3.72 and 3.21 (AB, J
= 12 Hz, 4 H, 2ϫ ArCH2N), 7.25 (m, 2 H), 7.46 (m, 4 H), 7.56 (d,
J = 8 Hz, 2 H), 7.93 (m, 4 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 46.0 (2ϫ CH3), 53.3 (CH2), 55.7 (CH2), 58.0 (2ϫ CH2), 125.3
(CH Ar), 125.7 (CH Ar), 127.4 (CH Ar), 127.8 (CH Ar), 128.2
(CH Ar), 131.3 (C Ar), 133.1 (C Ar), 133.4 (C Ar), 134.9 (C Ar)
ppm. C26H26N2 (366.50): calcd. C 85.21, H 7.15, N 7.64; found C
84.98, H 7.35, N 7.67.
(1R,2R,4R)-N-[2-{(Sa)-3H-Dinaphtho[2,1-c:1Ј,2Ј-e]azepin-4(5H)-
yl}ethyl]-1,7,7-trimethylbicyclo[2.2.1]heptan-2-amine [(Sa,R,R,R)-3]:
This compound was purified by chromatography (silica, pentane:e-
1
thyl acetate, 3:1, 5% methanol). White solid; yield 87%. H NMR
(300 MHz, C6D6): δ = 0.85 (s, 3 H, CH3), 1.03 (s, 3 H, CH3), 1.08–
1.20 (m, 3 H), 1.28 (s, 3 H, CH3), 1.45–1.78 (m, 6 H), 2.39–2.48
(m, 1 H), 2.53–2.62 (m, 2 H), 2.66–2.81 (m, 2 H), 3.51 and 3.18
(AB, J = 12 Hz, 4 H, 2ϫ ArCH2N), 6.97–7.04 (m, 2 H), 7.17–7.24
(m, 2 H), 7.60–7.71 (m, 4 H), 7.34 (d, J = 8 Hz, 2 H), 7.64 (d, J =
8 Hz, 2 H) ppm. 13C NMR (75 MHz, C6D6): δ = 12.5 (CH3), 20.9
(CH3), 27.9 (CH2), 37.3 (CH2), 39.4 (CH2), 45.8 (CH), 47.0 (CH2),
47.2 (CH2), 48.8 (CH2), 55.6 (CH2), 55.8 (CH2), 67.9 (CH), 125.7
(CH Ar), 126.1 (CH Ar), 127.9 (CH Ar), 128.1 (CH Ar), 128.5
(CH Ar), 128.6 (CH Ar), 132.0 (C Ar), 133.7 (C Ar), 134.4 (C Ar),
135.5 (C Ar) ppm. C34H38N2 (474.69): calcd. C 86.03, H 8.07, N
5.90; found C 86.46, H 7.78, N 5.76.
N1,N1-Dimethyl-N2-{(1R,2R,4R)-1,7,7-trimethylbicyclo[2.2.1]-
heptan-2-yl}ethane-1,2-diamine [(Ra,R,R)-6]: Colourless oil; yield
(E)-N1,N1-Dimethyl-N2-{(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]-
heptan-2-ylidene}ethane-1,2-diamine [(R,R)-5]: (R)-(+)-camphor
(3 mmol, 456 mg) and N,N-dimethylethylenediamine (2 mL) were
dissolved in anhydrous toluene (2 mL) and the solution was heated
under reflux in a Dean–Stark trap. The reaction was monitored
by GC–MS and after the camphor was completely consumed, the
mixture was cooled to room temperature. The excess of N,N-di-
methylethylenediamine was removed under vacuum and the imine
was obtained in high purity as pale yellow oil; yield 652 mg (98%).
1H NMR (300 MHz, CDCl3): δ = 0.73 (s, 3 H, CH3), 0.91 (s, 3 H,
CH3), 0.94 (s, 3 H, CH3), 1.18 (m, 1 H), 1.33 (m, 1 H), 1.64 (m, 1
H), 1.77–1.89 (m, 2 H), 1.92 (t, J = 4 Hz, 1 H), 2.27 (s, 6 H, 2ϫ
CH3), 2.34 (m, 1 H), 2.52 (t, J = 8 Hz, 2 H), 3.33 (m, 2 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 11.4 (CH3), 18.9 (CH3), 19.5
(CH3), 27.4 (CH2), 32.1 (CH2), 35.5 (CH2), 43.8 (CH), 45.9 (2ϫ
NCH3), 47.0 (C), 50.9 (C=NCH2), 53.5 (C), 59.9 [(CH3)2NCH2],
182.9 (C=N) ppm. C14H26N2 (222.37): calcd. C 75.62, H 11.79, N
12.60; found C 75.53, H 11.98, N 12.49.
1
89%. H NMR (300 MHz, C6D6): δ = 0.92 (s, 3 H, CH3), 1.06 (s,
3 H, CH3), 1.18 (m, 2 H), 1.35 (s, 3 H, CH3), 1.56–1.70 (m, 2 H),
1.77 (m, 3 H), 2.15 (s, 6 H, 2ϫ NCH3), 2.25–2.48 (m, 2 H), 2.60
(m, 2 H), 2.72 (m, 1 H) ppm. 13C NMR (75 MHz, C6D6): δ = 12.3
(CH3), 20.8 (2ϫ CH3), 27.8 (CH2), 37.1 (CH2), 39.1 (CH2), 45.3
(2ϫ NCH3), 45.7 (CH), 46.8 (CH2), 48.6 (C), 59.5 (CH2), 67.7
(CHNH) ppm. C14H28N2 (224.39): calcd. C 74.94, H 12.58, N
12.48; found C 75.05, H 12.50, N 12.45.
Synthesis of Palladium Complexes
[PdCl2{(Ra,R,R,R)-3}] (7): In a two-neck flask containing a solu-
tion of [Pd(PhCN)2Cl2] (54 mg, 0.14 mmol) in THF (5 mL), a solu-
tion of ligand (Ra,R,R,R)-3 (38 mg, 0.08 mmol) in the same solvent
(5 mL) was added. After stirring for 2 h the solvent was removed
by evaporation and the residue was dissolved in the minimum
amount of dichloromethane and filtered through celite; after add-
ing pentane (25 mL) a yellow powder was obtained. The resulting
solid was washed several times with pentane, and then dried under
vacuum; yield 35 mg (71%). 1H NMR (500 MHz, CDCl3): δ = 0.80
(s, 3 H, CH3), 0.85 (s, 3 H, CH3), 1.07 (s, 3 H), 1.16–1.50 (m, 3 H),
1.78 (m, 1 H), 1.86 (m, 1 H, CH), 2.13 (m, 1 H), 2.22–2.36 (m, 3
H), 2.86 (m, 1 H), 4.16 (bt, 1 H, CH2NHCH), 4.37 (dt, J = 12
and 3 Hz, 1 H, CH2CH2NH), 4.66 and 4.59 (AB, J = 12 Hz, 2 H,
ArCH2N), 4.81 and 2.92 (AB, J = 12 Hz, 2 H, ArCЈH2N), 6.26 (br.
s, 1 H, NH), 7.12–7.27 (m, 3 H), 7.38–7.46 (m, 3 H), 7.55 (d, J =
8 Hz, 1 H), 7.69 (d, J = 8 Hz, 1 H), 7.81 (d, J = 8 Hz, 1 H), 7.97
(d, J = 8 Hz, 1 H), 8.08 (d, J = 8 Hz, 1 H), 8.25 (d, J = 8 Hz, 1 H)
General Procedure for Imine Reduction: In a three-necked flask
equipped with a bubbler, the imine (1 equiv.) was dissolved in a
mixture of anhydrous methanol and chloroform (4:1). To this solu-
tion, anhydrous NiCl2 (2.1 equiv.) was added, the flask was cooled
to –40 °C and NaBH4 (3.1 equiv.) was added in portions over a
period of 1 h. The reaction mixture was left stirring overnight at
room temperature. The excess of NaBH4 was quenched with an
aqueous solution of 5% NaOH. and the product extracted three
times in a separation funnel with chloroform. The organic phase
Eur. J. Inorg. Chem. 2011, 2738–2745
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2743

G. Bottari, A. Meduri, D. Drommi, G. Brancatelli, F. Faraone
FULL PAPER
ppm. 13C NMR (100 MHz, CDCl3): δ = 12.9 (CH3), 21.5 (CH3), dried under vacuum; yield 22 mg (80%). 1H NMR (500 MHz,
22.0 (CH3), 26.4 (CH2), 32.9 (CH2), 39.6 (CH2), 44.5 (CH), 45.4 CD2Cl2), major isomer: δ = –0.03 (s, 3 H, CH3), 0.65 (s, 3 H, CH3),
(CH2), 46.8 (C), 50.9 (C), 60.4 (CH2), 62.5 (CH2), 63.1 (CH2), 68.6 0.98 (s, 3 H, CH3), 1.06 (m, 1 H), 1.14 (m, 1 H), 1.48 (m, 1 H),
(CH), 125.6 (CH Ar), 125.8 (CH Ar), 125.9 (CH Ar), 126.0 (CH 1.59 (m, 1 H, CH), 1.84 (m, 1 H), 1.97 (m, 1 H), 2.55–2.67 (m, 2
Ar), 127.50 (CH Ar), 127.52 (CH Ar), 128.3 (CH Ar), 128.38 (CH
Ar), 128.4 (CH Ar), 128.7 (CH Ar), 129.2 (CH Ar), 131.0 (C Ar),
130.2 (CH Ar), 131.08 (CH Ar), 131.1 (CH Ar), 131.2 (CH Ar),
133.4 (CH Ar), 133.9 (CH Ar), 135.2 (CH Ar), 136.2 (CH Ar) ppm.
C34H37Cl2N2Pd (650.99): calcd. C 62.73, H 5.73, N 4.30; found C
62.82, H 5.81, N 4.23.
H), 2.80–2.96 (m, 2 H), 3.08 and 2.26 (AB, J = 13 Hz, 2 H,
CH2CH2NH-), 3.41–3.55 (m, 2 H), 3.69 (m, 1 H), 4.22 and 2.93
(AB, J = 12 Hz, 2 H, ArCH2N), 4.39 (d, J = 12 Hz, 1 H, Hanti),
4.56 (d, J = 12 Hz, 1 H, HЈanti), 6.26 (t, J = 12 Hz, 1 H, Hcentral),
6.78 (t, J = 7 Hz, 1 H), 7.22–7.50 (m, 10 H), 7.67 (m, 1 H), 7.81
(m, 2 H), 7.92 (m, 2 H), 7.97 (d, J = 8 Hz, 1 H), 8.19 (d, J = 8 Hz,
1 H), 8.28 (d, J = 8 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 14.3 (CH3), 18.5 (CH3), 20.5 (CH3), 26.9 (CH2), 38.2 (CH2),
41.0 (CH2), 45.0 (CH), 47.0 (C), 50.1 (CH2), 50.6 (C), 58.9 (CH2),
59.2 (ArCH2N), 59.7 (ArCЈH2N), 73.1 (CHNH), 77.0 (CHterminal),
79.7 (CHterminal), 109.2 (CHcentral), 126.5 (CH Ar), 126.6 (CH Ar),
126.9 (CH Ar), 127.1 (CH Ar), 127.4 (CH Ar), 128.2 (CH Ar),
128.3 (CH Ar), 128.7 (CH Ar), 128.8 (CH Ar), 129.1 (CH Ar),
129.2 (CH Ar), 129.6 (CH Ar), 130.8 (C Ar), 131.3 (C Ar), 132.3
(C Ar), 132.5 (C Ar), 133.9 (C Ar), 134.5 (C Ar), 134.8 (C Ar),
135.6 (C Ar), 137.2 (C Ar), 139.2 (C Ar) ppm. C50H50F3N2O3PdS
(922.41): calcd. C 65.10, H 5.46, N 3.04; found C 65.32, H 5.20, N
3.08.
[PdCl2{(Sa)-4}] (8): This complex was synthesized according to the
same procedure reported for 7; yield 88%. 1H NMR (300 MHz,
CDCl3): δ = 2.41 (m, 2 H, CH2NMe2), 2.89 (s, 3 H, NCH3), 2.94
[m, 1 H, CH2CH2N(CH3)2], 2.99 (s, 3 H, NCH3), 3.04 (d, J =
11.8 Hz, 1 H, CH2), 3.83 (d, J = 13.8 Hz, 1 H, CH2), 4.90 (d, J =
13.8 Hz, 1 H, CH2), 4.91 (d, J = 11.8 Hz, 1 H, CH2), 7.20–7.36 (m,
3 H, H Ar), 7.35–7.57 (m, 4 H, H Ar), 7.95–8.00 (m, 3 H, H Ar),
8.03 (d, J = 8.4 Hz, 1 H, H Ar), 8.18 (d, J = 8.4 Hz, 1 H, H Ar)
ppm. 13C NMR (75 MHz, CDCl3): δ = 50.6 (NCH3), 53.3
(NCЈH3), 61.3 (NCH2CH2N), 61.9 (NCЈH2CH2N), 62.3
(ArCH2N), 62.9 (ArCЈH2N), 125.9 (CH Ar), 126.2 (CH Ar), 126.5
(CH Ar), 126.6 (CH Ar), 127.3 (CH Ar), 127.8 (CH Ar), 127.9
(CH Ar),128.3 (CH Ar), 128.6 (CH Ar), 128.7 (CH Ar), 128.9 (CH
Ar), 130.5 (CH Ar), 130.0 (C Ar), 131.2 (C Ar), 131.4 (C Ar), 133.6
(C Ar), 134.0 (C Ar), 134.8 (C Ar), 135.7 (C Ar) ppm.
C26H26Cl2N2Pd (543.82): calcd. C 57.42, H 4.82, N 5.15; found C
57.61, H 4.73, N 5.07.
[Pd{(Sa)-4}(η3-PhCHCHCHPh)]OTf (12): This complex was syn-
thesized according to the same procedure reported for 11; yield
92%. 1H NMR (300 MHz, CDCl3), major isomer: δ = 2.08 (s, 3
H, NCH3), 2.27 (m, 1 H), 2.44 (d, J = 14 Hz, 1 H, ArCH2N), 2.47
[m, 1 H, CH2N(CH3)2], 2.51 (s, 3 H, NCЈH3), 2.82 (d, J = 12 Hz,
1 H, NCH2CH2N), 3.03 (m, 1 H, ArCЈH2N), 3.21 (d, J = 14 Hz,
1 H, ArCH2N), 3.25 (m, 1 H, CH2NMe2), 4.44 (d, J = 12 Hz, 1 H,
Hanti), 4.85 (d, J = 12 Hz, 1 H, ArCЈH2N), 5.12 (d, J = 11.9 Hz, 1
H, Hanti), 6.34 (t, J = 12 Hz, 1 H, Hcentral), 6.70 (dt, J = 8 and
1 Hz, 1 H), 7.25–7.15 (m, 3 H), 7.47–7.27 (m, 10 H), 7.61 (dt, J =
8 and 1 Hz, 1 H), 7.75 (m, 2 H), 7.85 (m, 2 H), 8.12 (d, J = 8 Hz,
1 H), 8.28 (d, J = 8 Hz, 2 H), 8.32 (d, J = 8 Hz, 2 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 47.0 (NCЈH3), 51.3 (NCH3), 58.6
(NazCH2), 59.2 (NazCЈH2), 59.9 (Me2NCH2CH2), 60.0
(Me2NCH2CH2), 75.4 (Cterminal), 78.9 (CЈterminal), 107.5 (Ccentral),
129.7–126.1 (CH Ar), 130.0 (C Ar), 130.9 (C Ar), 131.0 (C Ar),
132.0 (C Ar), 133.4 (C Ar), 134.0 (C Ar), 134.7 (C Ar), 135.9 (C
Ar), 136.4 (C Ar), 136.7 (C Ar) ppm.
[PdCl2{(R,R)-5}] (9): This complex was synthesized according to
the same procedure reported for 7; yield 79%. 1H NMR (300 MHz,
CD3CN): δ = 0.85 (s, 3 H, CH3), 1.00 (s, 3 H, CH3), 1.26 (m, 1 H),
1.70 (m, 1 H), 1.75 (m, 1 H), 1.92 (s, 3 H, CH3), 2.10–2.35 (m, 3
H), 2.52 (m, 1 H), 2.66 (s, 3 H, NCH3), 2.95 (m, 1 H), 2.97 (s, 3
H, NCЈH3), 3.67 (dd, J = 12 and 3 Hz, 1 H), 4.26 (dt, J = 8 and
3 Hz, 1 H) ppm. 13C NMR (75 MHz, CD3CN): δ = 13.9 (CH3),
19.1 (CH3), 19.9 (CH3), 26.9 (CH2), 31.2 (CH2), 41.5 (CH2), 43.3
(CH), 51.4, 52.0, 53.6, 57.0, 58.8, 67.7, 196.9 (C=N) ppm.
C14H26Cl2N2Pd (399.68): calcd. C 42.07, H 6.56, N 7.01; found C
42.15, H 6.60, N 6.97.
[PdCl2{(R,R,R)-6}] (10): This complex was synthesized according
to the same procedure reported for 7; yield 81%. 1H NMR
(300 MHz, CDCl3): δ = 0.76 (s, 3 H, CH3), 0.99 (s, 3 H, CH3), 1.02
(s, 3 H, CH3), 1.19 (m, 1 H), 1.51 (m, 1 H), 1.66–1.80 (m, 2 H),
1.82–1.92 (m 1 H), 2.06 (m, 1 H), 2.27 (dd, J = 13 and 3 Hz, 1 H),
2.50 (dd, J = 14 and 3 Hz, 1 H), 2.70–2.78 (m, 1 H), 2.80 (s, 3 H,
NCЈH3), 3.02–3.09 (m, 2 H), 3.12 (s, 3 H, NCH3), 4.19 (tt, J = 14
and 4 Hz, 1 H), 5.42 (b, 1 H, NH) ppm. 13C NMR (75 MHz,
CDCl3): δ = 13.4 (CH3), 20.7 (CH3), 20.8 (CH3), 27.2 (CH2), 38.3
(CH2), 39.3 (CH2), 45.0 (CH), 47.5 (C), 50.6 (CH2N), 51.8 (CH3N),
53.0 (CЈH2N), 53.9 (CЈH2N), 63.7 (C), 67.5 (CHN) ppm.
C14H28Cl2N2Pd (401.71): calcd. C 41.86, H 7.03, N 6.97; found C
42.03, H 6.91, N 6.92.
General Procedure for Palladium-Catalyzed Allylic Alkylations: In
a 30 mL Schlenk tube equipped with a magnetic stirring bar,
[Pd(η3-C3H5)Cl]2 (2.34 mg, 0.0064 mmol) was treated with the
N,N-ligand (0.0130 mmol) in CH2Cl2 (0.7 mL). The solutions were
degassed (three freeze–thaw cycles) and stirred for 30 min. After
this time period, to the solutions 1-acetoxy-1,3-diphenylpropene
(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) were added sequentially, and the mixtures
degassed. The reactions were monitored by TLC (hexane:AcOEt,
3:1), and after completion the mixtures were diluted with Et2O and
extracted with two portions of ice-cold saturated aqueous NH4Cl
solutions. The solutions were then dried (MgSO4) and evaporated
in vacuo. The resultant residues were purified by flash chromatog-
raphy (silica gel, hexane:AcOEt, 5:1) to afford the products as a
colourless oils. The enantiomeric excess values were determined by
chiral HPLC (Chiralcel OD-H column) and the assignment of the
absolute configurations was made by comparison with reported
data.
[Pd(Ra,R,R,R)-3][(η3-PhCHCHCHPh)]OTf (11): To a yellow sus-
pension of [Pd(η3-PhCHCHCHPH)Cl]2 (10 mg, 0.015 mmol) in
acetone (5 mL), AgOTf (7.7 mg, 0.030 mmol) was added and con-
sequently the solution became brightened in colour. After 1 h of
stirring, the mixture was filtered through celite. The solvated spe-
cies was left to react with a solution of the ligand (Ra,R,R,R)-3
(14.2 mg, 0.06 mmol) in acetone (2 mL), and after 1 h the solvent
was removed under reduced pressure. The brownish residue was
dissolved in a small amount of dichloromethane and the complex
was precipitated by slowly adding pentane while stirring. The re-
sulting yellow solid was washed with three portions of pentane and
Supporting Information (see footnote on the first page of this arti-
cle): 1H NMR spectra of dinitrogen ligands 1–6 and palladium
complexes 6–12 are reported.
2744
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 2738–2745

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Acknowledgments
This work was supported by Ministero dell’Istruzione, dell’Univer-
sità e della Ricerca (MIUR), PRIN 2007HMTJWP_005.
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Received: February 2, 2011
Published Online: May 10, 2011
Eur. J. Inorg. Chem. 2011, 2738–2745
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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