Basicity and bulkiness effects of 1,8-diaminonaphthalene, 8-aminoquinoline and their alkylated derivatives on the different efficiencies of η5-C5H5 and η5-C 5Me5 ruthenium precatalysts in allylic etherification reactions

Article abstract of DOI:10.1039/c0nj00338g

The different behaviours of Ru(η⁵-C₅H ₅) and Ru(η⁵-C₅Me₅) precatalysts, [Ru(η⁵-C₅R₅)(NCMe)(N,N)] PF₆ (R = H, Me), in the allylic etherification reaction of cinnamyl chloride using the phenoxide anion as a nucleophile was considered. The N,N ligands are the commercial products 1,8-diaminonaphthalene and 8-aminoquinoline, and their derivatives obtained by alkylation of the amino nitrogen atoms: alkyl substituents that are also bulky chiral C₂-symmetric frameworks allow modulation of the basicity and steric demand of the ligands. Some of the precatalysts, [Ru(η⁵-C₅R₅)(NCMe)(N,N)] PF₆ (R = H, Me), were also synthesized and characterized. The cinnamyl phenyl ether isomers were obtained with very high B/L regioselectivity values, either with Ru(η⁵-C₅H₅) or Ru(η⁵-C₅Me₅) precatalysts. The highest B/L regioselectivity values achieved with Ru(η⁵-C₅Me ₅) precatalysts were found with the N,N ligand 1,8-diaminonaphthalene and its derivatives; with Ru(η⁵-C₅H₅) precatalysts best B/L values were obtained with ligands derived from 8-aminoquinoline. A correlation between the B/L regioselectivity, and the σ-donor power and bulkiness of the substituents at the nitrogen atoms of the N,N coordinated ligand was established, but the Ru(η⁵-C ₅H₅) or Ru(η⁵-C₅Me₅) precatalysts followed an opposite trend. It was also found that the low ee values did not depend on the diastereomeric composition of the chiral-at-metal precatalyst [Ru(η⁵-C₅R₅)(NCMe)(N,N)]PF ₆. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/c0nj00338g

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Basicity and bulkiness effects of 1,8-diaminonaphthalene,
8-aminoquinoline and their alkylated derivatives on the different
efficiencies of g5-C5H5 and g5-C5Me5 ruthenium precatalysts in
allylic etherification reactionsw
Giovanna Brancatelli,* Dario Drommi, Giusy Femino, Maria Saporita,
Giovanni Bottari and Felice Faraone*
Received (in Gainesville, FL, USA) 2nd May 2010, Accepted 25th June 2010
DOI: 10.1039/c0nj00338g
The different behaviours of Ru(Z5-C5H5) and Ru(Z5-C5Me5) precatalysts,
[Ru(Z5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me), in the allylic etherification reaction
of cinnamyl chloride using the phenoxide anion as a nucleophile was considered. The N,N
ligands are the commercial products 1,8-diaminonaphthalene and 8-aminoquinoline, and their
derivatives obtained by alkylation of the amino nitrogen atoms: alkyl substituents that are also
bulky chiral C2-symmetric frameworks allow modulation of the basicity and steric demand of the
ligands. Some of the precatalysts, [Ru(Z5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me), were also
synthesized and characterized. The cinnamyl phenyl ether isomers were obtained with very high
B/L regioselectivity values, either with Ru(Z5-C5H5) or Ru(Z5-C5Me5) precatalysts. The highest
B/L regioselectivity values achieved with Ru(Z5-C5Me5) precatalysts were found with the
N,N ligand 1,8-diaminonaphthalene and its derivatives; with Ru(Z5-C5H5) precatalysts best
B/L values were obtained with ligands derived from 8-aminoquinoline. A correlation between the
B/L regioselectivity, and the s-donor power and bulkiness of the substituents at the nitrogen
atoms of the N,N coordinated ligand was established, but the Ru(Z5-C5H5) or Ru(Z5-C5Me5)
precatalysts followed an opposite trend. It was also found that the low ee values did not
depend on the diastereomeric composition of the chiral-at-metal precatalyst
[Ru(Z5-C5R5)(NCMe)(N,N)]PF6.
Concerning the enantioselectivity in the formation of the
Introduction
branched product, only a few examples of high ee values are
reported in the literature.5b,6a
Transition metal-catalyzed allylic substitution reactions are still
a topic that continues to attract interest.1 Recently, attention
has turned to obtain chiral branched isomers from asymmetric
prochiral allylic precursors, such as cinnamyl derivatives, with
high regioselectivity and enantioselectivity, by nucleophilic
substitution at the more substituted allylic carbon.2 Enantio-
enriched chiral allyl alkyl compounds and allylic aryl ethers are
useful precursors for asymmetric synthesis.
Trost,3 Bruneau4 and other research groups5 have found
that the [Ru(Z5-C5Me5)(NCMe)3]PF6 complex and some
of its derivatives containing mono- or bidentate ligands are
efficient precatalysts, and induce very high values of regio-
selectivity in favour of the branched product, both in alkyl-
ation and etherification reactions of cinnamyl derivatives,
leading to the formation of C–C and C–O bonds, respectively
(Scheme 1).
Recently, we reported on the efficiency of the precatalysts
[Ru(Z5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me) in the catalyzed
alkylation and etherification reactions of cinnamyl derivatives,
where dimethylmalonate and phenoxide anions were used as
nucleophiles.7
The above-mentioned N,N bulky chiral ligands are charac-
terized by either a flexible or a rigid backbone. Surprisingly,
using [Ru(Z5-C5H5)(NCMe)(N,N)]PF6 precatalysts, values of
B/L regioselectivity (94/6) higher than those obtained using
the corresponding [Ru(Z5-C5H5)(NCMe)3]PF6 precursor were
reached in the etherification reactions of cinnamyl chloride
with phenoxide anions. Such results led us to carry out further
In contrast, Ru(Z5-C5H5) precatalysts have been considered
poorly efficient and stereoselective in the same reactions.
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica
`
Fisica dell’Universita di Messina, Salita Sperone 31, Vill. S. Agata,
98166 Messina, Italy. E-mail: ffaraone@unime.it;
Fax: +39 90-393-756
w Electronic supplementary information (ESI) available: Further
experimental details. See DOI: 10.1039/c0nj00338g
Scheme 1 Scheme for the ruthenium-catalyzed allylic alkylation and
etherification of cinnamyl derivatives.
c
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investigations aiming to clarify the effect of basicity and steric
hindrance of the cyclopentadienyl rings Z5-C5H5 or Z5-C5Me5
or even of the coordinated ligands, on the precatalyst
features during each step of the catalytic process. Herein,
we report the results obtained by using the complexes
[Ru(Z5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me) as precatalysts
in the etherification reaction of cinnamyl chloride by
phenoxide anions; the N,N ligands are 1,8-diaminonaphthalene,
8-aminoquinoline and their alkylated derivatives. Some of the
ligands presented in this paper have been reported in work
directed towards the study of 1,8-bis(dimethylamino)naphthalene
derivatives as atropoisomeric proton sponges.8
Results and discussion
Synthesis of the ligands
The herein-reported ligands are derived from 1,8-diamino-
naphthalene and 8-aminoquinoline; their structures are
characterized by coplanarity between the donor atoms and
the ligand skeleton. The basicity of the donor atoms and the
steric hindrance around them have been modulated by their
functionalization with suitable substituents. It has to be con-
sidered that, while the ligands synthesized from 1,8-diamino-
naphthalene give a six-membered ring by coordination to a
metal centre, those derived from 8-aminoquinoline form a five-
membered ring; consequently the 1,8-diaminonaphthalene
derived ligands exhibit a reduced bite angle with respect to
those derived from 8-aminoquinoline. Moreover, the latter
induce a lower electronic density at the ruthenium centre with
respect to the 1,8-diaminonaphthalene derived ligands (Fig. 1).
(a) Ligands 2–4 and 6–8 were obtained by substitution of
the NH2 hydrogen atoms in starting compounds 1 and 5 (used
also as ligands) by alkyl groups so that the s-donor properties
of the ligands were tuned (Fig. 1a); they are not chiral (ligand 8
is in racemic form) and have a low steric hindrance. Only
ligand 9 has an aryl substituent at the nitrogen atom of
8-aminoquinoline; in this ligand, the amino nitrogen basicity
is lower than that of its precursor.
Fig. 1 The used N,N ligands: (a) the 8-aminoquinoline and (b) the
1,8-diaminonaphthalene derivatives.
synthesized and characterized with the aim of comparing their
catalytic performance with that of the precatalysts made
in situ. The [Ru(Z5-C5R5)(NCMe)(N,N)]PF6 complexes
(N,N = 1, R = Me, 18; N,N = (R,R)-13, R = Me, 19;
N,N = (R,R)-14, R = H, 20; N,N = 7, R = H, 21; N,N = 7,
R = Me, 22; N,N = 9, R = Me, 23) were synthesized by
reacting the cationic complex [Ru(Z5-C5R5)(NCMe)3]PF6, in
acetonitrile, with an equimolar amount of the N,N ligand
dissolved in toluene. Compounds 18–23 are solids each of
various colour; some of them are relatively stable towards air
and moisture, and were characterized by elemental analysis
and NMR spectroscopy. The 1H NMR spectra showed the
splitting of some peculiar signals of the ligand derived
from 1,8-diaminonaphthalene or 8-aminoquinoline due to
the coordination to the ruthenium centre.
Particularly, in the 1H NMR spectra of complexes 18
(N,N = 1, R = Me), 19 (N,N = (R,R)-13, R = Me) and
20 (N,N = (R,R)-14, R = H), containing ligands derived from
1,8-diaminonaphthalene, some of the aromatic protons in the
naphthalene ring are shifted upfield owing to ligand coordination
to the metal centre. In the 1H NMR spectrum in acetone-d6 of
18, the aromatic protons show three signals at 6.20, 5.95,
5.71 ppm, whereas the aminic hydrogens are shifted downfield
at 5.72 and 5.40 ppm, compared with the free ligand signals.
The methyl groups of the coordinated Z5-C5Me5 give a singlet
at 1.68 ppm. Given that the ruthenium itself is a stereogenic
(b) Ligands 10–15 derived from 1,8-diaminonaphthalene are
bulky chiral ligands containing the C2-symmetric (S)-(+)-2,20-
(2-azapropane-1,3-diyl)-1,10-binaphthalene or trans-(R,R)-2,5-
dimethylpyrrolidinyl framework (Fig. 1b). Ligands 10–15 were
synthesized with the aim of increasing the steric demand and
evaluating the asymmetric induction on the branched isomer
formed in the enantioselective allylic etherification (see Catalytic
experiments). The chiral ligands 16 and 17, derived from
8-aminoquinoline and containing the same chiral moieties as
ligands 10–15, have been previously reported by our research
group and already used in the same catalytic process, but in
different experimental conditions.7
The synthesis and the NMR spectroscopic data for all the
prepared ligands are reported in a detailed way in the Experi-
mental section. All ligands were characterized by elemental
analysis, GC-MS and NMR spectroscopy.
Synthesis of the precatalysts [Ru(g5-C5R5)(NCMe)(N,N)]PF6
Preliminarily to the catalytic study, some of the complexes
[Ru(Z5-C5R5)(NCMe)(N,N)]PF6 used as precatalysts were
c
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centre, in principle, a mixture of diastereomers, (Sa,RRu) and
(Sa,SRu), differing in the absolute configuration at the
metal centre, can be obtained in the synthesis of the
[Ru(Z5-C5R5)(NCMe)(N,N)]PF6 precatalysts 19 and 20 con-
taining the N,N chiral ligands (R,R)-13 and (R,R)-14. In their
1H NMR spectra, 19 and 20 show the CH and CH2 proton
signals of the pyrrolidinyl chiral fragment slightly shifted at
high field in comparison with the free ligands; moreover,
compound 20 shows the splitting of the broad signal of the
cinnamyl chloride with phenoxide anions. The reaction, lead-
ing to a new carbon–oxygen bond, affords linear and branched
cinnamyl phenyl ether isomers; the branched isomer contains a
stereogenic carbon atom (Scheme 1).
The reactions were carried out in CH3CN at room tempera-
ture, and the precatalyst was formed in situ by adding the
N,N ligand to [Ru(Z5-C5R5)(NCMe)3]PF6 (R = H, Me). After
1 h, to the solution containing the precatalyst (3 mol%) were
sequentially added cinnamyl chloride and a slight excess of
phenol in the presence of K2CO3. We verified that the same
results were obtained by using the synthesized precatalyst as
by forming it in situ. The results are reported in Table 1.
A comparison with data reported in the literature4b indicates
that the catalytic systems are very active in the experimental
conditions used; in fact, the conversion of cinnamyl chloride
was quantitative or close to 100% after 20 h in almost all
experiments, both with Ru(Z5-C5Me5) and Ru(Z5-C5H5) pre-
catalysts. In some cases, the full conversion was reached in a
few hours as indicated by monitoring the reaction via TLC.
The results highlight that Ru(Z5-C5Me5) precatalysts give
the highest B/L values with 1,8-diaminonaphthalene deriva-
tives, while the Ru(Z5-C5H5) precatalysts are more regioselec-
tive when 8-aminoquinoline derivatives are the coordinating
ligands. This trend can be correlated to the different bite angle
of ligands derived from 1,8-diaminonaphthalene and 8-amino-
quinoline; for a better counterbalance of steric interactions,
the more crowded C5Me5 ring prefers the coordination of 1,8-
diaminonaphthalene derived ligands, featuring a smaller bite
angle than the 8-aminoquinoline derivatives.
1
(CH3)2N methyl groups. In the H NMR spectrum of 19 in
acetone-d6, the presence of two signals for the Z5-C5Me5
methyl protons in an 86 : 14 ratio at 1.64 ppm for the major
isomer, and at 1.72 ppm for the minor isomer supports the
formation of two diastereoisomers. Acetone-d6 solutions of 19
are not air and moisture stable; in solution, under an argon
atmosphere, the ratio between the diastereomers is unchanged.
We were not able to separate and obtain the diastereomers in
pure form. In contrast, in the 1H NMR spectrum of 20 in
acetone-d6, the Z5-C5H5 protons give only one signal as a
singlet at 5.16 ppm, indicating that compound 20 is formed as
a single diastereomer. Because we were not able to obtain
crystals of 20 suitable for X-ray diffractometry, we have no
information about the absolute configuration at the ruthenium
centre of the single diastereomer obtained. However, the
acquaintance of these data does not seem to be indispensable
in obtaining useful information about the induction of
enantioselectivity when 20 is used as the precatalyst. Since
the catalytic runs were carried out in CH3CN, we confirmed
that in CD3CN the diastereomeric ratios are equal and do not
change with time.
In all cases, it appears clear that the coplanarity of the
N-donor and the skeleton ligand atoms in the chelating agent
In complexes 21 (N,N = 7, R = H), 22 (N,N = 7, R = Me)
and 23 (N,N = 9, R = Me), the coordinated N,N ligands are
derived from 8-aminoquinoline (5) by methylation or, in only
one case, arylation of the amino nitrogen atom. Ligand
coordination to metal centre causes a downfield shift of the
a-quinolinyl hydrogen atom signal. Compounds 21 and 22
differ from each other in their coordination to the ruthenium
centre of the Z5-C5H5 and Z5-C5Me5 ions, respectively. They
were obtained as dark orange solids that are moderately stable
to air and moisture. In both the 1H NMR spectra of 21 and 22,
diastereotopic methyl groups bound to nitrogen atoms appear
as singlets at 3.54 and 3.48 ppm, and at 3.32 and 3.22 ppm,
respectively. In free ligand 7, these methyl protons give one
singlet at 3.09 ppm. Z5-C5H5 protons in 21 and Z5-C5Me5
methyl protons in 22 exhibit singlets at 4.32 and 1.58 ppm,
respectively. Precatalyst 23 contains N-(3,5-dimethylphenyl)-
quinolin-8-amine ligand 9; it was obtained as a dark green
powder. The 1H NMR spectrum in CD3CN shows a singlet at
2.40 ppm for the methyl groups of the 3,5-dimethylphenyl
moiety and a singlet at 6.99 ppm for the aminic hydrogen;
methyl protons of the Z5-C5Me5 ligand show a singlet at
1.40 ppm. In the 1H NMR spectrum of compounds 19–23,
the methyl signal of the acetonitrile ligand was found in the
2.01–2.84 ppm range.
Table 1 Allylic etherification of cinnamyl chloride with phenol
catalyzed by [Ru(Z5-C5R5)(N,N)(NCMe)]PF6 (R
= H, Me)
complexesa
Ru(Z5-C5H5)
Ru(Z5-C5Me5)
Conversion
Conversionb B/Lb (%)b
B/L (%)b
Entry N,N
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
100
100
100
97
100
100
100
100
100
90
71/29 100
75/25 100
68/32 100
76/24 95
72/28 100
84/16 100
90/10 75
86/14 100
57/43 100
68/32 100
67/33 100
70/30 100
69/31 100
72/28 100
79/21 97
95/5
93/7
87/13
81/19
81/19
68/32
87/13
81/19
70/30
84/16
86/14
93/7
86/14
86/14
91/9
—
—
rac-8
9
9
10c
11c
12c
13c
14c
15c
16d
17d
(Sa)-10
(Sa)-11
(Sa,Sa)-12
(R,R)-13
(R,R)-14
(R,R,R,R)-15 89
(Sa)-16
(R,R)-17
97
97
99
97
100
100
83/17
84/16
—
—
a
Experimental conditions: catalyst (3 mol%), phenol (1.5 equiv.),
K2CO3 (1 equiv.), CH3CN as solvent, room temperature, 24 h.
b
c
Determined by 1H NMR and GC-MS. A complete table of ee
d
Catalytic experiments
values of the branched isomer is reported in the ESI. Ligands already
used in previous work. The corresponding Ru(Z5-C5Me5) derivatives
were not stable enough to be used in the catalytic experiments.7
The [Ru(Z5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me; N,N =
1–15) precatalysts were tested in the etherification reaction of
c
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is a requirement of primary importance to achieve high regio-
selectivity values.4a,c,d
[Ru(Z5-C5R5)(NCMe)(N,N)]PF6 (R = H, CH3; N,N =
enantiopure nitrogen ligand) precatalysts. It was also very
surprising for us to observe that the product 1-phenoxy-1-
phenyl-2-propene was obtained nearly in a racemic form using
the Ru(Z5-C5Me5) precatalyst containing the N,N chiral
ligand (R,R)-13 as diastereomeric mixture (86 : 14), or even
the Ru(Z5-C5H5) precatalyst containing the ligand (R,R)-14)
as a single diastereomer (see above, Synthesis of the precatalysts).
It is noteworthy that ligands (R,R)-13 and (R,R)-14 are
structurally very similar, possessing the same chiral moiety
in an enantiopure form; moreover, they give a similar regio-
selectivity. Preliminarily, the 1H NMR spectra of 19 and 20 in
acetone-d6 and their invariability with time led us to exclude
changes in the precatalyst due to breaking processes of the
Ru–N bond induced by the solvent. Therefore, the very similar
enantioselectivity values indicate that, at least in this case,
there is no correlation between the diastereomeric composition
of the precatalyst and the ee, which should then be determined
by the diastereomeric ratio of the catalytic intermediate
[Ru(Z3-PhCHCHCH2)(Z5-C5Me5)(N,N)]2+, produced by the
oxidative addition of cinnamyl chloride to the precatalyst;
further investigations are in progress in order to confirm this
point of view.
The influence of the N,N ligand on the efficiency of the
catalyst is also evidenced by the correlation between the B/L
regioselectivity and the s-donor power of the amino nitrogen
atoms in the coordinated ligand. Looking at the 1,8-diamino-
naphthalene derived ligands, it appears that, using
[Ru(Z5-C5Me5)(NCMe)(N,N)]PF6 complexes, the B/L regio-
selectivity reaches the highest value of 95 : 5 with 1,8-diamino-
naphthalene ligand 1, whose donor nitrogen atoms possesses
the lowest basicity. The B/L regioselectivity decreases
for [Ru(Z5-C5Me5)(NCMe)(N,N)]PF6 precatalysts (N,N
from 1 to 4) as the nitrogen atom basicity grows. An
opposite trend is observed with the corresponding
[Ru(Z5-C5H5)(NCMe)(N,N)]PF6 precatalysts; in this case, the
B/L regioselectivity increases, although in a limited way, from 1
to 4 as the nitrogen atom basicity grows, and the highest value
(90 : 10) is found with the most basic ligand derived from
8-aminoquinoline. Summarizing, when the catalytic precursor
contains the Z5-C5Me5 ligand, which offers the metal centre
more electronic density than the Z5-C5H5 ligand, the highest
B/L regioselectivity values are found with ligands having the
lowest s-donor power. A stronger s-donor power of the N,N
ligand is required in the Ru(Z5-C5H5) precatalysts in order to
counterbalance the low charge density at the ruthenium centre
and to obtain the highest B/L regioselectivity values.
Conclusions
The [Ru(Z5-C5R5)(NCMe)(N,N)]PF6 (R = H, Me) complexes
are active and effective precatalysts in the allylic etherification
of cinnamyl chloride with phenoxide anions. The branched
isomer cinnamyl phenyl ether was obtained with very good
regioselectivity, either with Ru(Z5-C5Me5) (up to 95 : 5) or
with Ru(Z5-C5H5) (up to 90 : 10) precatalysts. These values are
very close to the highest reported for the classic catalytic test of
allylic etherification with PhOH/K2CO3.4b It is noteworthy
that these regioselectivity values have been obtained with
precatalysts containing the commercial and low-cost 1,8-
diaminonaphthalene and the 8-dimethylaminoquinoline, readily
synthesized from commercial 8-aminoquinoline. Nevertheless,
the work emphasizes and explains for the first time the
opposite effect of the s-donor power of the N,N coordinated
ligand on the B/L regioselectivity values for Ru(Z5-C5Me5)
and Ru(Z5-C5H5) precatalysts. In fact, the results demonstrate
that a counterbalance between the electronic density induced
by the Z5-cyclopentadienyl ligand at the ruthenium centre and
the s-donor power of the N,N coordinated ligand plays a
determining role in the regioselectivity.
It is noteworthy that the B/L values found with precatalysts
[Ru(Z5-C5Me5)(NCMe)(1)]PF6 and [Ru(Z5-C5H5)(NCMe)(7)]PF6
are higher compared to those reported for the corresponding
precursors [Ru(Z5-C5R5)(NCMe)3]PF6 (R = H, Me), respectively
75 : 25 and 90 : 10.
This assumption also explains the results achieved with the
[Ru(Z5-C5Me5)(NCMe)(N,N)]PF6 (R = H, Me) precatalysts,
having N,N ligands with comparable electronic properties but
very different steric demands. In fact, the increase of ligand
bulkiness modifies in an opposite way the B/L regioselectivity
induced by Ru(Z5-C5Me5) and Ru(Z5-C5H5) precatalysts
(see and compare entry 4 with entries 11, 12, 14 and 15 in
the Ru(Z5-C5Me5) series or entry 7 with entries 16 and 17 in
the Ru(Z5-C5H5) series). Indeed, it was established that in
similar pentamethylcyclopentadienyl ruthenium and rhodium
complexes containing diamine ligands with substituents of
different steric demand on nitrogen donor atoms, the bulky
groups cause a lengthening of the M–N bond distance, with a
consequent lowering of the electronic density contribution to
the metal centre.9 Therefore, in accordance with the verified
effect induced by the increase of donor atom basicity on the
regioselectivity of the process, the increase of steric demand of
the coordinated ligands raises the B/L regioselectivity ratio in
Ru(Z5-C5Me5) systems and produces the opposite effect in
Ru(Z5-C5H5) systems.
It was also noted that the presence of highly bulky groups
in the coordinated ligand influences in the opposite way the
B/L regioselectivity values by the use of Ru(Z5-C5Me5) and
Ru(Z5-C5H5) precatalysts, depending on the charge density
required by the metal center in the catalytic process.
To the best of our knowledge, even if the allylic substitution
process catalyzed by chiral ruthenium(II) complexes leads to
the formation of the branched isomer with excellent regio-
selectivity, it induces poor or modest ee values, except for only
a few examples reported by the Bruneau,6a Onitsuka6b and
Lacour6c–f research groups.
Experimental
General methods
All manipulations were carried out under an argon atmo-
sphere using standard Schlenk techniques. Freshly distilled
solvents were used throughout and dried by standard
The results herein reported highlight very low enantio-
selectivity values (in the range 4–7%) by the use of
c
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procedures. Published methods were used to prepare the
following precursors: (Sa)-(+)-2,20-dibromomethyl-1,10-bi-
naphthalene10 and (2S,5S)-2,5-hexandiol cyclic sulfate.11
Cinnamyl methyl carbonate12 and the ligand N-(3,5-dimethyl-
phenyl)quinolin-8-amine (9)13 were prepared according to
published procedures. 1,8-Diaminonaphthalene (1), N,N,N0,N0-
tetramethylnaphthalene-1,8-diamine (4) and 8-aminoquinoline
(5) were purchased from Sigma-Aldrich and Strem, and used
as supplied. The ligands 16 and 17 were prepared as previously
reported by our research group.7 For column chromato-
graphy, silica gel 60 (220 ꢀ 440 mesh) purchased from Fluka
and basic alumina (70–290 mesh) purchased from Sigma-Aldrich
were used. GC-MS analysis were carried out with a Shimadzu
GCMS-QP5000 spectrometer. NMR experiments were carried
out using a Varian 300 spectrometer and referenced to internal
tetramethylsilane. Enantiomeric excesses were determined by a
HPLC Shimadzu LC-8A. Elemental analyses were performed by
Redox s.n.c., Cologno Monzese, Milan, Italy.
of 8-aminoquinoline (0.25g, 1.68 mmol) in THF (40 mL)
followed by (CH3)2SO4 (1.6 mL, 16.8 mmol). The reaction
mixture was stirred at 75 1C for 24 h, then allowed to cool to
room temperature. A solution of NaOH pellets (12 g) in
H2O (30 mL) was added and the mixture was stirred at
room temperature overnight. The resulting solution was
transferred to a separating funnel and extracted with CH2Cl2
(2 ꢁ 150 mL). The CH2Cl2 solution was washed with H2O
(2 ꢁ 500 mL), dried over MgSO4, filtered and evaporated in
vacuo. The resulting yellow oil was purified by chromato-
graphic column (silica gel; hexane–ethyl acetate 3 : 1) giving
in two different fractions the desired products 6 and 7.
N-methylquinolin-8-amine (6). Yield: 8% (21.3 mg,
1
0.134 mmol). H NMR (300 MHz, CDCl3): d 8.70 (dd, 1H,
3
4
H a-quinoline, J = 4 Hz, J = 2 Hz), 8.06 (dd, 1H, ArH,
3J = 8 Hz, 4J = 2 Hz), 7.34–7.43 (m, 2H, ArH), 7.05 (dd, 1H,
3
4
3
ArH, J = 8 Hz, J = 2 Hz), 6.65 (dd, 1H, ArH, J = 8 Hz,
4J = 1 Hz), 6.11 (bs, 1H, NH), 3.04 (d, 3H, NHCH3,
3J = 6 Hz). 13C NMR: d 146.81, 145.82, 138.23, 136.00,
128.55, 127.85, 121.38, 113.68, 104.12, 30.07. Anal. calc. for
C10H10N2 (158.2): C, 75.92; H, 6.37; N, 17.71. Found: C,
76.01; H, 6.31; N, 17.59.
Synthesis of ligands
Synthesis of N0-methylnaphthalene-1,8-diamine (2) and
N0,N0,N-trimethylnaphthalene-1,8-diamine (3). To a solution
of sodium hydride (152 mg, 6.33 mmol) in 5 mL of THF, 1,8-
diaminonaphthalene (500 mg, 3.16 mmol) was added. After
stirring for 3 h, methyl iodide (0.098 mL, 1.58 mmol) was
added dropwise and the mixture was left to react overnight;
the progress of the reaction was monitored by GC-MS. The
reaction mixture was cautiously quenched with water (5 mL)
and then extracted with ethyl acetate (3–5 mL). The combined
organic phases were dried (MgSO4) and the solvent was
removed in vacuo to obtain an oil purified by column
chromatography on neutral alumina. Elution with a gradient
from 1 to 10% with ethyl acetate in hexane gave in different
fractions the ligand 3, dimethyl substituted naphthalene and
ligand 2, respectively.
N,N-dimethylquinolin-8-amine (7). Yield: 82% (237.3 mg,
1.38 mmol). 1H NMR (300 MHz, CDCl3): d 8.89 (dd, 1H,
3
4
H a-quinoline, J = 4 Hz, J = 2 Hz), 8.10 (dd, 1H, ArH,
3J = 8 Hz, 4J = 2 Hz), 7.34–7.46 (m, 3 H, ArH), 7.12 (dd, 1H,
ArH, 3J = 7 Hz, 4J = 2 Hz), 3.09 (s, 6H, N(CH3)2).
13C NMR: d 150.59, 147.84, 142.77, 136.36, 129.57, 126.62,
120.85, 120.83, 115.68, 44.52. Anal. calc. for C11 H12N2
(172.2): C, 76.71; H, 7.02; N, 16.27. Found: C, 76.55; H,
7.21; N, 16.89.
Synthesis of (rac)-N-(2-methylbutyl)quinolin-8-amine (8). To
a mixture of 8-aminoquinoline (0.145 g, 1 mmol), K2CO3
(0.27 g, 1.96 mmol) in anhydrous DMF (5 mL) at 120 1C,
1-bromo-2-methyl butane (0.49 mL, 3.94 mmol) was added.
The solution was stirred under reflux for 24 h, then extracted
with CH2Cl2, dried over MgSO4, filtered and evaporated
in vacuo. The resulting brown oil was purified by chromato-
graphic column (silica gel; hexane–ethyl acetate 3 : 1) to give
the product as a yellow oil.
N0-methylnaphthalene-1,8-diamine (2). Yield: 40% (218 mg,
1.26 mmol). 1H NMR (300 MHz, CDCl3): d 7.29–7.24 (m, 2H,
ArH), 7.18–7.11 (m, 2H, ArH), 6.62 (dd, 1H, ArH, 3J = 7 Hz,
3
4
4J = 1 Hz), 6.49 (dd, 1H, ArH, J = 8 Hz, J = 1 Hz), 5.79
(b, 1H, CH3–NH), 4.39 (b, 2H, NH2), 2.88 (s, 3H, CH3–NH).
13C NMR: d 147.89, 143.81, 136.82, 126.64, 126.27, 125.87,
120.49, 117.90, 112.66, 104.77, 31.47. Anal. calc. for C11
H12N2 (172.2): C, 76.71; H, 7.02; N, 16.27. Found: C, 76.41;
H, 7.09; N, 16.08.
Yield: 72% (154.3 mg, 0.72 mmol). 1H NMR (300 MHz,
CDCl3): d 8.70 (dd, 1H, H a-quinoline, 3J = 4 Hz, 4J = 2 Hz),
8.04 (dd, 1H, ArH, 3J = 8 Hz, 4J = 2 Hz), 7.32–7.40 (m, 2H,
ArH), 7.00 (d, 1H, ArH, 3J = 8 Hz), 6.65 (d, 1H, ArH,
3J = 8 Hz), 6.23 (b, 1H, NH), 3.20–3.29 (m, 1H, CH2NH),
3.05–3.15 (m, 1H, CH2NH), 1.80–1.92 (m, 1H, CH), 1.53–1.67
(m, 1H, CH3CH2), 1.22–1.34 (m, 1H, CH3CH2), 1.05 (d, 3H,
N0,N0,N-trimethylnaphthalene-1,8-diamine (3). Yield: 30%
(218 mg, 1.26 mmol). 1H NMR (300 MHz, CDCl3): d 8.90
(b, 1H, NH), 7.50 (dd, 1H, ArH, 3J = 8 Hz, 4J = 1 Hz),
7.33–7.27 (m, 2H, ArH), 7.14 (dd, 1H, ArH, 3J = 8 Hz, 4J = 1
3
CH3CH, J = 7 Hz), 0.97 (t, 3H, CH2CH3, 3J = 7 Hz). 13C
3
4
Hz), 7.04 (dd, 1H, ArH, J = 8 Hz, J = 1 Hz), 6.41 (d, 1H,
ArH, 3J = 7 Hz), 2.96 (d, 3H, CH3-N 3J = 5 Hz), 2.74 (s, 6H,
CH3–N–CH3). 13C NMR: d 151.93, 148.10, 136.86, 126.98,
125.52, 125.24, 115.01, 114.84, 102.37, 46.05, 30.43. Anal. calc.
for C13 H16N2 (200.3): C, 77.96; H, 8.05; N, 13.99. Found: C,
77.71; H, 8.18; N, 13.81.
NMR: d 146.65, 136.05, 136.02, 127.83, 121.30, 113.23, 104.34,
49.47, 34.37, 34.17, 27.46, 18.29, 17.77, 11.43. Anal. calc. for
C14H18N2 (214.3): C, 78.46; H, 8.47; N, 13.07. Found: C,
78.11; H, 8.61; N, 13.29.
Synthesis of (S)-8-(3H-dinaphtho[2,1-c:10,20-e]azepin-4(5H)-yl)-
naphthalen-1-amine (10). In a Schlenk flask, to a solution
of (Sa)-2,20-bis(bromomethyl)-1,10-binaphthalene (600 mg,
1.36 mmol) in 10 mL of toluene, Et3N (0.57 mL, 4.08 mmol)
Synthesis of N-methylquinolin-8-amine (6) and N,N-di-
methylquinolin-8-amine (7). To a solution of NaH (0.8 g,
37 mmol) in anhydrous THF (10 mL) was added a solution
c
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1
Yield: 45% (160.8 mg, 0.225 mmol). H NMR (300 MHz,
and 1,8-diaminonaphthalene (1.29 g, 8.18 mmol) were added.
The mixture was stirred at 100 1C overnight. The reaction
mixture was quenched with water (5 mL) and then extracted
with diethyl ether (3–5 mL). The combined organic phases
were dried over MgSO4, filtered and evaporated in vacuo.
Purification by chromatographic column (basic alumina,
hexane–diethyl ether 2 : 1) gave the product as a white solid.
Yield: 50% (154.3 mg, 0.72 mmol). 1H NMR (300 MHz,
CDCl3): d 7.93–8.03 (m, 4H, ArH), 7.74 (d, 1H, ArH,
3J = 8 Hz), 7.46–7.56 (m, 5H, ArH), 7.13–7.34 (m, 6H,
ArH), 6.93 (d, 1H, ArH, 3J = 7 Hz), 6.60 (d, 1H, ArH,
3J = 7), 6.25 (b, 2H, NH2), 4.15, (d, 1H, CH2N, 3J = 14 Hz),
4.08 (d, 1H, CH2N, 3J = 11 Hz), 4.05 (d, 1H, CH2N,
3
CDCl3): d 7.88 (d, 2H, ArH, J = 8 Hz), 7.73 (d, 2H, ArH,
3J = 8 Hz), 7.58 (t, 4H, ArH), 7.38–7.48 (m, 12H, ArH),
3
7.22–7.28 (m, 2H, ArH), 6.90 (d, 2H, ArH, J = 8 Hz), 6.88
3
(d, 2H, ArH, J = 8 Hz), 6.75 (d, 2H, ArH, 3J = 7 Hz), 6.53
3
(d, 2H, ArH, J = 8 Hz), 3.95 (s, 4H, CH2N), 3.89 (d, 2H,
CH2N, 3J = 10 Hz), 3.80 (d, 2H, CH2N, 3J = 10 Hz).
13C NMR: d 152.45, 147.93, 134.79, 134.18, 133.73, 133.67,
133.41, 132.93, 132.57, 131.28, 130.88, 129.46, 128.67, 128.27,
128.25, 127.66, 127.47, 127.23, 127.19, 127.07, 125.96, 125.69,
125.51, 125.29, 125.25, 124.65, 121.94, 113.91, 58.15, 52.03.
Anal. calc. for C54H38N2 (714.9): C, 90.72; H, 5.36; N, 3.92.
Found: C, 90.59; H, 5.22; N, 4.01.
3
3J = 14 Hz), 3.88 (d, 1H, CH2N, J = 11 Hz). 13C NMR: d
149.81, 146.01, 137.32, 135.55, 134.78, 134.03, 133.30, 133.20,
132.21, 131.48, 129.13, 128.65, 128.35, 128.17, 127.58, 127.52,
127.48, 126.68, 125.99, 125.73, 125.69, 125.16, 119.15, 116.99,
109.73, 57.77, 55.14. Anal. calc. for C32 H24N2 (436.6): C,
88.04; H, 5.54; N, 6.42. Found: C, 88.31; H, 5.71; N, 6.29.
Synthesis of 8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)naphthalen-
1-amine (13) and 1,8-bis((2R,5R)-2,5-dimethylpyrrolidin-1-yl)-
naphthalene (15). Ligands 13 and 15 were synthesized following
the same procedure but changing the ratio of the starting
reagents. 1,8-diaminonaphthalene and (2S,5S)-2,5-hexandiol
cyclic sulfate were refluxed in dry THF (20–25 mL) for 24–48 h.
The resulting precipitate indicated the presence of the
zwitterionic amine–sulfate species. The Schlenk flask was
cooled to ꢂ78 1C and 1.1 equivalents of n-butyllithium 1.6 M
were added. The mixture was warmed to room temperature
and then refluxed for 72 h. Diethyl ether was added to the
solution which was then washed with 10% ammonium chloride,
water and brine and extracted into diethyl ether. The extract
was dried (MgSO4) and concentrated to yield the crude
material. Purification using column chromatography, (basic
alumina, hexane–diethyl ether 2 : 1) gave the product.
Synthesis of (S)-8-(3H-dinaphtho[2,1-c:10,20-e]azepin-4(5H)-yl)-
N,N-dimethylnaphthalen-1-amine (11). To a solution of sodium
hydride (123 mg, 5.13 mmol) in 3 mL of THF, a solution
of ligand 10 (100 mg, 0.229 mmol) in 4 mL of THF and
CH3I (0.214 mL, 3.43 mmol) were sequentially added. The
mixture was refluxed for 48 h, then allowed to cool to room
temperature. A solution of NaOH pellets (1.67 g) in H2O
(4 mL) was added and the mixture was stirred at room
temperature overnight. The reaction mixture was quenched with
water (5 mL) and then extracted with CH2Cl2 (3 ꢁ 10 mL). The
combined organic phases were dried (MgSO4) and the solvent
was removed in vacuo. The residue was dissolved in acetone and
boiled. After slow cooling the product was obtained as
white solid.
Ligand 13: 1,8-diaminonaphthalene (3.95 g, 25 mmol) and
(2S,5S)-2,5-hexandiol cyclic sulfate (0.9 g, 5 mmol), 5/1 ratio
respectively. N-butyl lithium (1.6 M, 3.5 mL, 5.5 mmol). The
mixture of reaction was refluxed for 48 h. The ligand was
obtained as a red oil. Yield: 65% (0.78 g, 3.25 mmol).
Yield: 40% (42.6 mg, 0.09 mmol). 1H NMR (300 MHz,
3
CDCl3): d 8.02 (dd, 2H, ArH, J = 8 Hz), 7.87 (d, 1H, ArH,
3J = 8 Hz), 7.71 (d, 2H, ArH, 3J = 8 Hz), 7.59–7.16 (m, 10H,
ArH), 6.95 (d, 1H, ArH, 3J = 6 Hz), 6.88 (d, 1H, ArH, 3J = 8 Hz),
1H NMR (300 MHz, CDCl3): d 7.45 (d, 1H, ArH, J = 8 Hz),
3
7.26 (t, 1H, ArH, 3J = 7 Hz), 7.17 (t, 1H, ArH, 3J = 8 Hz), 7.10
(d, 1H, ArH, 3J = 8 Hz), 7.01 (d, 1H, ArH, 3J = 7), 6.52 (d, 1H,
3
3
6.78 (d, 1H, ArH, J = 8 Hz), 4.10 (d, 1H, N–CHH, J =
10 Hz), 4.03 (s, 2H, CHH–N–CHH), 3.92 (d, 1H, N–CHH,
3J = 10 Hz), 2.69 (bs, 3H, CH3-NCH3), 2.61 (bs, 3H,
CH3–N–CH3). 13C NMR: d 155.16, 147.57, 145.18, 137.11,
134.75, 131.34, 131.30, 128.58, 128.37, 128.28, 128.15, 127.69,
127.45, 125.78, 125.51, 125.27, 121.91, 114.04, 58.27, 52.89,
29.71. Anal. calc. for C34H28N2 (464.6): C, 87.90; H, 6.07; N,
6.03. Found: C, 88.05; H, 5.96; N, 6.18.
3
ArH, J = 8 Hz), 6.15 (b, 2H, NH2), 3. 90 (m, 1H, CH), 3.77
(m, 1H, CH), 2.22 (m, 2H, CH2), 1.57 (m, 2H, CH2), 1.17 (d, 3H,
3
3
CH3, J = 7 Hz), 0.64 (d, 3H, CH3, J = 7 Hz). 13C NMR:
d 146.11, 143.52, 137.16, 126.36, 124.79, 124.64, 120.69, 119.13,
116.99, 109.23, 59.56, 52.23, 32.05, 30.77, 20.05, 16.64. Anal. calc.
for C16H20N2 (240.3): C, 79.96; H, 8.39; N, 11.66. Found: C,
80.08; H, 8.26; N, 11.51.
Ligand 15: 1,8-diaminonaphthalene (1.07 g, 6.8 mmol) and
(2S,5S)-2,5-hexandiol cyclic sulfate (2.45 g, 13.6 mmol), 1/2
ratio respectively. N-butyl lithium (1.6 M, 4.7 mL, 7.5 mmol).
The mixture of reaction was refluxed for 24 h. The ligand was
obtained as a yellow powder. Yield: 10% (219 mg, 0.68 mmol).
1H NMR (300 MHz, CDCl3): d 7.36 (dd, 2H, ArH, 3J = 8 Hz,
4J = 1 Hz), 7.28 (t, 2H, ArH), 6.88 (dd, 2H, ArH, 3J = 8 Hz,
4J = 1 Hz), 4.39 (sextet, 2H, CH, 3J = 6 Hz), 3.76 (sextet, 2H,
Synthesis of 1,8-bis((S)-3H-dinaphtho[2,1-c : 10,20-e]azepin-
4(5H)-yl)naphthalene (12). To a solution of 1,8-diamino-
naphthalene (79.1 mg, 0.5 mmol) in 5 mL of toluene and
Et3N (0.42 mL, 3 mmol), a 10 mL solution of (Sa)-2,20-bis-
(bromomethyl)-1,10-binaphthalene in toluene (440 mg, 1 mmol)
was added dropwise. The mixture was stirred under reflux at
110 1C for 72 h. After this time, the solvent was removed and
the residue was dissolved in dichloromethane, washed sequen-
tially with water and brine. The combined organic phases were
dried over MgSO4, filtered and evaporated in vacuo. Chromato-
graphic purification over basic alumina (hexane–diethyl ether
2 : 1 as eluent) gave the product as a white solid.
3
CH, J = 6 Hz), 2.08–2.29 (m, 4H, CH2), 1.63-1.71 (m, 2H,
CH2), 1.30–1.40 (m, 2H, CH2), 1.34 (d, 6H, CH3, 3J = 6 Hz),
0.31(d, 6H, CH3, 3J = 6 Hz). 13C NMR: d 144.86, 124.92,
124.55, 121.87, 121.46, 115.87, 115.56, 60.31, 60.08, 50.22,
49.94, 32.32, 32.06, 30.47, 30.07, 19.49, 19.05, 16.92, 16.64.
c
2858 New J. Chem., 2010, 34, 2853–2860 This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

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3
(d, 1H, ArH, J = 6 Hz), 6.84 (d, 1H, ArH, J = 5.86 Hz),
3
Anal. calc. for C22 H30N2 (322.5): C, 81.94; H, 9.38; N, 8.69.
Found: C, 82.09; H, 9.25; N, 8.57.
3
3
6.66 (d, 1H, ArH, J = 6 Hz), 6.20 (t, 1H, ArH, J = 6 Hz),
5.16 (s, 5H, C5H5), 4.19 (m, 1H, CH), 3.85 (m, 1H, CH), 3.05
(s, 3H, CH3-N), 2.91 (s, 3H, CH3-N), 2.84 (s, 3H, CH3CN),
2.30–2.10 (m, 2H, CH2) 1.70 (m, 1H, CH2), 1.43–1.23 (m, 1H,
Synthesis of 8-((2R,5R)-2,5-dimethylpyrrolidin-1-yl)-N,N-di-
methylnaphthalen-1-amine (14). This ligand was synthesized
following the same procedure used for ligand 11, starting from
ligand 13(300 mg, 1.25 mmol) but refluxing the reaction
mixture for 24 h. After chromatographic purification of the
crude product (basic Al2O3, hexane–diethyl ether 2 : 1) the
ligand was obtained as a yellow oil.
Yield: 55% (184.5 mg, 0.69 mmol). 1H NMR (300 MHz,
CDCl3): d 7.35 (m, 5H, ArH), 6.90 (m, 1H, ArH), 6.87 (m, 1H,
ArH), 4.23 (sextet, 1H, CH, 3J = 6 Hz), 3.80 (sextet, 1H, CH,
3J = 6 Hz), 2.90–2.60 (two bs, 6H, CH3–N–CH3), 2.15
(m, 3H, CH2), 1.68 (m, 1H, CH2), 1.32 (d, 3H, CH–CH3,
3J = 6 Hz), 0.34 (d, 3H, CH–CH3,3J = 6 Hz). 13C NMR: d
151.14, 144.18, 137.78, 125.13, 125.11, 122.13, 121.45, 116.16,
112.79, 59.90, 50.67, 32.39, 31.03, 19.09, 17.42. Anal. calc. for
C18H24N2 (268.4): C, 80.55; H, 9.01; N, 10.44. Found: C,
80.41; H, 9.01; N, 10.58.
3
3
CH2), 1.32 (d, 3H, CH3, J = 6 Hz), 0.35 (d, 3H, CH3, J =
6 Hz). Anal. calc. for C25H32F6N3PRu (620.6): C, 48.39; H,
5.20; N, 6.77. Found: C, 48.28; H, 5.09; N, 6.71.
[Ru(g5-C5H5)(NCMe)(7)]PF6 (21). Brown powder. Yield:
78.5% (41 mg, 0.0785 mmol). H NMR (300 MHz, CD3CN):
1
d 9.62 (dd, 1H, H a-quinoline, 3J = 5 Hz, 4J = 1 Hz), 8.40 (dd,
1H, ArH, J = 8 Hz, J = 1 Hz), 7.88–7.93 (m, 2H, ArH),
3
4
3
3
7.68 (t, 1H, ArH, J = 8 Hz), 7.55 (dd, 1H, ArH, J = 8 Hz,
4J = 5 Hz), 4.32 (s, 5H, C5H5), 3.54 (s, 3H, N(CH3)2), 3.48
(s, 3H, N(CH3)2), 2.19 (s, 3H, CH3CN). Anal. calc. for
C18H20F6N3PRu (524.4): C, 41.23; H, 3.84; N, 8.01. Found:
C, 41.02; H, 3.57; N, 7.92.
[Ru(g5-C5Me5)(NCMe)(7)]PF6 (22). Dark orange powder.
Yield: 72% (42.8 mg, 0.072 mmol). 1H NMR (300 MHz,
CD3CN): d 9.10 (dd, 1H, H a-quinoline, 3J = 5 Hz, 4J =
1 Hz), 8.31 (dd, 1H, ArH, 3J = 8 Hz, 3J = 1 Hz), 7.81 (t, 2H,
General procedure for the synthesis of [Ru(g5-C5R5)(NCMe)-
(N,N)]PF6 (18–23) (R = H or Me). The [Ru(Z5-C5R5)(N,N)-
CH3CN]PF6 complexes with N,N = 1, (R = Me, 18), 13
(R = Me, 19), 14 (R = H, 20), 7, (R = H, 21, R = Me, 22), 9
(R = Me, 23) were synthesized in the same way with the
following procedure.
3
ArH, 3J = 8 Hz), 7.65 (dt, 2H, ArH, J = 8 Hz, 4J = 5 Hz),
3.32 (s, 3H, NCH3), 3.22 (s, 3H, NCH3), 2.01 (s, 3H, CH3CN),
1.58 (s, 15H, C5Me5). Anal. calc. for C23 H30F6N3PRu (594.5):
C, 46.26; H, 5.09; N, 7.07. Found: C, 46.11; H, 5.22; N, 7.01.
A solution of the N,N ligand (0.1 mmol) in toluene (2 mL)
was added to a solution of [Ru(Z5-C5H5)(NCMe)3]PF6
(45 mg, 0.1 mmol) or [Ru(Z5-C5Me5)(NCMe)3]PF6 (50.4 mg,
0.1 mmol) in acetonitrile (1 mL). The mixture was stirred for
about 1 h while the starting colour of the solution changed
depending on the ligand. After this time the solvent was
removed under inert atmosphere and the residue was washed
with diethyl ether still under inert atmosphere. The complexes
were obtained as powders of different colour.
[Ru(g5-C5Me5)(NCMe)(9)]PF6 (23). Dark green powder.
Yield: 80% (53.6 mg, 0.08 mmol). 1H NMR (300 MHz,
CD3CN): d 9.07 (dd, 1H, H a-quinoline, 3J = 6 Hz, 3J =
2 Hz), 8.53 (dd, 1H, ArH, 3J = 8 Hz, 4J = 2 Hz), 7.98 (dd, 2H,
ArH, 3J = 8 Hz, 4J = 6 Hz), 7.43 (d, 1H, ArH, 3J = 10 Hz),
7.12 (s, 1H, ArH), 6.99 (bs, 2H, ArH), 6.87 (bs, NH), 6.69
(d, 1H, 3J = 10 Hz, ArH), 2.40 (s, 6H, 2 CH3Ph), 2.07
(s, 3H, CH3CN), 1.40 (s, 15H, C5Me5). Anal. calc. for
C29H34F6N3PRu (670.6): C, 51.94; H, 5.11; N, 6.27. Found:
C, 52.08; H, 5.23; N, 6.33.
[Ru(g5-C5Me5)(NCMe)(1)]PF6 (18). Purple powder. Yield:
90% (52.2 mg, 0.09 mmol). H NMR (300 MHz, acetone-d6):
1
3
d 7.37 (t, 1H, ArH, J = 7 Hz), 6.91 (m, 2H, ArH), 6.20 (d,
Allylic etherification reaction
3
1H, ArH, J = 6 Hz), 5.95 (m, 1H, ArH), 5.72 (b, 2H, NH2),
5.71 (d, 1H, ArH, 3J = 6 Hz), 5.40 (b, 2H, NH2), 2.80, (s, 3H,
CH3CN), 1.68 (s, 15H, C5Me5). Anal. calc. for C22
H28F6N3PRu (580.5): C, 45.52; H, 4.86; N, 7.24. Found: C,
45.38; H, 4.81; N, 7.22.
After stirring 0.015 mmol of [Ru(Z5-C5R5)(NCMe)3]PF6 and
0.015 mmol of N,N ligand in acetonitrile at room temperature
for 1 h, 0.75 mmol of potassium carbonate and 0.5 mmol of
cinnamyl chloride were added and after 15 min, 0.75 mmol of
phenol were added. The mixture was stirred for 24 h and
monitored by TLC (hexane/1% Et2O). After this time, the
solution was filtered on silica and concentrated under vacuo.
The resulting oil was analyzed by 1H NMR spectroscopy
(determined by integration of allylic proton) and GC-MS to
determine the conversion; the enantiomeric excess was
determined by HPLC (Daicel OJ-H column, hexane/iPrOH =
99/1, 220 nm, tR = 42.7 min (R enantiomer), tR = 46.3 min
(S enantiomer)).
[Ru(g5-C5Me5)(NCMe)(R,R-13)]PF6 (19). Green powder.
Yield: 88% (58.3 mg, 0.088 mmol). 1H NMR (300 MHz,
acetone-d6): d 7.57 (t, 1H, ArH, 3J = 9 Hz), 7.34 (d, 1H,
3
ArH, J = 8 Hz), 7.26 (d, 1H, ArH, 3J = 7 Hz), 6.65 (b, 2H,
NH2), 6.20 (d, 1H, ArH, 3J = 6 Hz), 5.90 (t, 1H, ArH,
3J = 6 Hz), 5.74 (d, 1H, ArH, 3J = 6 Hz), 3.95 (m, 1H,
CH), 3.85 (m, 1H, CH), 2.80 (s, 3H, CH3CN), 2.25 (m, 2H,
CH2), 1.54 (s, 15H, C5Me5), 1.70–1.50 (m, 2H, CH2), 1.30
(d, 3H, CH3, 3J = 6 Hz), 0.60 (d, 3H, CH3, 3J = 6 Hz). Anal.
calc. for C28H38F6N3PRu (662.7): C, 50.75; H, 5.78; N, 6.34.
Found: C, 50.82; H, 5.65; N, 6.32.
Acknowledgements
[Ru(g5-C5H5)(NCMe)(R,R-14)]PF6 (20). Yellow powder.
This work was supported by Ministero dell’Istruzione,
dell’Universita e della Ricerca (MIUR-Rome; PRIN 2007
HMTJWP_005).
Yield: 92% (57.1 mg, 0.092 mmol). 1H NMR (300 MHz,
acetone-d6):
d = 6 Hz), 7.10
7.40 (d, 2H, ArH, 3J
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 2853–2860 2859

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